AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TALLAHASSEE FL 556 AM EST SUN DEC 16 2007 ...LAKE WIND ADVISORY IN EFFECT TODAY... ...FREEZE WATCH IN EFFECT FOR TONIGHT... .SYNOPSIS... VERY BUSY SHIFT. SAT LATE INTO OVERNIGHT HOURS...NEGATIVELY TILTED TROUGH DIGGING EWD FROM LWR MISS VALLEY OH/TENN VALLEYS AIDED STRONG INFLUX OF OLGA GENERATED TROPICAL PLUME INTO CWA. THIS PUSHED SQUALL AND COLD FRONT RAPIDLY EWD. WITH LOW LEVEL REMNANT OF OLGA ACCELERATING NEWD AND BECOMING ABSORBED INTO STRENGTHENING SW STEERING FLOW. THIS AGGRAVATES THE THREAT OF ECHO TRAINING AS NOTED ON AREA RADARS. ADD DEW POINTS NEAR 70 DEGREES ...STRONG WARM FRONT ACROSS SE GA SERVING AS FOCUS FOR LIFT AND VERY GOOD DEEP LYR SHEAR COMBINED TO GENERATE SEVERAL SEVERE THUNDERSTORMS AND TORNADOES OVER CWA SAT EVENING INTO LATE NIGHT ESPECIALLY ALONG INTERSECTION OF ADVANCING SQUALL/WARM FRONT. THIS ACCOUNTED FOR TORNADO AND FLASH FLOOD WATCH. AT 2 AM EST...SQUALL ACROSS DIXIE AND FRONT STARTING TO CATCH UP NOW CROSSING APALACHICOLA AND WILL BARRELING THRU REST OF CWA THRU SUNRISE. CONDITIONS RAPIDLY IMPROVING FROM W-E AND TORNADO WATCH AND MOST OF FLOOD WATCH EXPIRED B4 3 AM EST. AT UPPER LEVELS PROGRESSIVE LARGE-SCALE PATTERN WILL PERSIST THRU SHORT TERM. NEXT UPSTREAM TROUGH WILL MOVE EWD INTO THE PACIFIC NW LATER TODAY. THIS WILL WORK ON UPPER TROUGH/LOW (RESPONSIBLE FOR SATURDAY STORMS) TO TRANSLATE NEWD FROM THE OH VALLEY THIS MORNING INTO NEW ENGLAND AND SRN QUEBEC BY MONDAY MORNING. RESULT IS NEAR ZONAL FLOW ACROSS MOST OF CONUS THRU EARLY WORK WEEK. AT LOWER LEVELS DEEP LOW ASSOCD WITH ABOVE TROUGH OVER THE OH VALLEY THIS MORNING EXPECTED WEAKEN OVER SRN NEW ENGLAND THIS AFTN AS SECONDARY COASTAL LOW SIGNIFICANTLY DEEPENING AS IT MOVES UP ATLC COAST NEWD THROUGH SRN NEW ENGLAND INTO NEW BRUNSWICK. TRAILING COLD FRONT SHOULD QUICKLY MOVE OFF THE SERN ATLANTIC COAST THIS MORNING...AND THROUGH THE FL PENINSULA TO KEY WEST BY LATE AFTERNOON. IN WAKE OF COLD FRONT...COLD HIGH PRESSURE OVER LOUISIANA COAST WILL BUILD EAST AND REACH EASTERN MISSISSIPPI BY DAYBREAK TODAY...WITH RIDGE AXIS EXTENDING EAST ACROSS THE GULF COAST STATES. LOCALLY THIS TRANSLATES TO GUSTY NORTHWEST WINDS AND CLEARING SKIES WITH MUCH COLDER AND DRIER CONDITIONS THROUGH EARLY NEXT WEEK. && .SHORT TERM...(TODAY THROUGH TUESDAY). TODAY...SMALL CHANCE OF SHOWERS WILL LINGER UNTIL AROUND 9-10 AM EST SE BIG BEND. OTHERWISE...BLUSTERY APTLY DESCRIBES THE DAY. TEMPERATURES WILL BE AT LEAST DEGREES COLDER THAN YESTERDAY AND 25 TO 30 DEGREES COLDER COMPARED TO THOSE EXPERIENCED LAST WEEK. PREFERRED A WEIGHTED BLEND TOWARD THE MAV GUIDANCE NUMBERS HERE AS THE MET NUMBERS SEEM JUST A LITTLE TOO COLD. ALSO...EXPECT SUSTAINED WINDS AND/OR FREQUENT GUSTS 20 TO 25 MPH SO LAKE WIND ADVISORY IN EFFECT. TONIGHT...WITH HIGH BUILDING EAST...STRONG COLD AIR ADVECTION WILL BE CONTINUING AND THE FACT THAT SOME LIGHT WINDS WILL CONTINUE THROUGH THE NIGHT ISN`T SIGNIFICANT ENOUGH TO KEEP TEMPERATURES ABOVE FREEZING. WINDS WILL STAY UP ENOUGH TO LIKELY PREVENT FROST. A FREEZE WATCH REMAINS IN EFFECT FOR THE ENTIRE CWA AND WILL LIKELY BE UPGRADED TO A WARNING BY DAY SHIFT. WINDS WILL DECREASE JUST ENOUGH TO PREVENT NEED FOR A WIND CHILL ADVISORY. MONDAY...WINDS WILL FINALLY ABATE...COLD AIRMASS REMAINS IN PLACE. DESPITE AMPLE SUNSHINE...LOW SUN ANGLE WILL ONLY SUPPORT MAX TEMPERATURES IN THE 50S GIVING US OUR SECOND CONSECUTIVE DAY WITH TEMPERATURES BELOW NORMAL. MONDAY NIGHT...HIGH PRESSURE WILL SETTLE OVER THE SOUTHEAST AFFORDING THE COLDEST NIGHT OF THE SEASON THUS FAR. LATEST MAV GUIDANCE IS GOING FOR THE MID 20S AREA WIDE...BUT THE MET IS A LITTLE WARMER. AT THIS POINT GIVEN THAT THE SURFACE RIDGE WILL SET UP A LITTLE NORTH OF THE REGION CONDITIONS AREN`T ALL THAT FAVORABLE FOR A HARD FREEZE...BUT GIVEN HOW COLD AND DRY THIS AIRMASS IS...WILL KEEP TEMPERATURES NEAR 25 DEGREES MOST LOCATIONS. ONE POTENTIAL PROBLEM FOR VERY COLD TEMPERATURES COULD BE SOME CIRRUS MOVING OVERHEAD TOWARD DAYBREAK. TUESDAY...ANOTHER DRY DAY. WITH HIGH MOVING EWD AND SURFACE RIDGE OFFSHORE BUILDING SWWD ACROSS CWA...LOW LEVEL FLOW VEERS TO ELY ALLOWING SOME LOW LEVEL MOISTURE TO ADVECT IN. MINS REBOUND TO SLIGHTLY ABOVE FREEZING INLAND LOCATIONS. && .LONG TERM...WEDNESDAY-FRIDAY. WEDNESDAY INTO THURSDAY...THE STRONG HIGH PRESSURE WILL SHIFT FURTHER ENE IN THE MID-ATLANTIC COAST AND WEDGE DOWN THE APPALACHIANS WHILE COASTAL TROUGH DEVELOPS JUST OFFSHORE. THIS WILL ALLOW THE WINDS TO VEER AROUND TO A MORE EAST-SOUTHEAST DIRECTION OUT AHEAD OF ANOTHER DEVELOPING SYSTEM WEST OF THE REGION. MORNING LOWS WILL AGAIN DROP TO NEAR OR BELOW FREEZING ACROSS INLAND LOCATIONS WITH THE AFTERNOON HIGHS REACHING THE LOW/MID 60S. GFS/ECMWF SHOW WEAK FRONT PUSHING ACROSS THE AREA SOMETIME BEGINNING THURSDAY AFTERNOON AND INTO THE NIGHT. BEYOND THE PERIOD AND INTO THE WEEKEND...THE MODELS SHOW ANOTHER IMPRESSIVE SYSTEM THAT LOOKS TO PUSH EAST ACROSS THE FORECAST AREA SOMETIME AROUND SATURDAY NIGHT INTO SUNDAY. && .AVIATION...IN WAKE OF SQUALL LINE AND COLD FRONT...GUSTY SHIFTING WINDS WILL CONTINUE THROUGH THE DAY. FOLLOWING THE PASSAGE OF THE FRONT WINDS WILL SHIFT TO THE NORTHWEST AND CONDITIONS WILL RAPIDLY IMPROVE TO VFR THROUGH THE REST OF THE FORECAST PERIOD AND BEYOND. && .MARINE... NEW NAM/RUC GUIDANCE SHOWS SUSTAINED SURFACE WINDS TODAY APPROACHING 30 KTS AND 900MB WINDS 35-40KTS. WITH STRONG COLD AIR ADVECTION...GOOD MIXING DOWN EXPECTED SO SUSTAINED GALE FORCE WINDS A BETTER THAN AVERAGE BET...WITH GALE FORCE GUSTS A VERY GOOD WAGER. SO GALE FORCE WARNING ISSUED FOR ALL WATERS UNTIL 11 AM EST TODAY. SCA REMAINS UNTIL MONDAY MORNING. WINDS AND SEAS WILL BEGIN TO RELAX ON MONDAY AS HIGH PRESSURE BUILDS OVER THE WATERS AND DROP BELOW ALL HEADLINE CRITERIA ON TUESDAY. && .FIRE WEATHER...WITH A DRY AIRMASS DESCENDING OVER THE REGION AND WINDY CONDITIONS EXPECTED...RED FLAG WARNING LOOKS GOOD FLORIDA FOR THIS AFTERNOON. WON`T BE DRY ENOUGH ELSEWHERE YET FOR ANY HEADLINES. BY MONDAY...THE AIRMASS DRIES OUT CONSIDERABLY WITH DEWPOINTS DROPPING OFF INTO THE TEENS. WILL THEREFORE ISSUE A FIRE WEATHER WATCH FOR ALL OF THE CWA WITH RH VALUES LIKELY DROPPING OFF INTO THE TEENS. && .PRELIMINARY POINT TEMPS/POPS... TALLAHASSEE 56 27 57 25 / 05 0 0 0 PANAMA CITY 56 33 58 34 / 0 0 0 0 DOTHAN 53 28 56 28 / 0 0 0 0 ALBANY 53 28 58 24 / 0 0 0 0 VALDOSTA 56 28 55 28 / 10 0 0 0 CROSS CITY 63 27 58 25/ 10 0 0 0 && .TAE WATCHES/WARNINGS/ADVISORIES... AL...LAKE WIND ADVISORY IN EFFECT UNTIL 4 PM CST THIS AFTERNOON. FREEZE WATCH FROM LATE SUNDAY TONIGHT THROUGH MONDAY MORNING. FIRE WEATHER WATCH FROM MONDAY MORNING THROUGH AFTERNOON. GA...LAKE WIND ADVISORY IN EFFECT UNTIL 5 PM CST THIS AFTERNOON. FREEZE WATCH FROM LATE SUNDAY TONIGHT THRU MONDAY MORNING. FIRE WEATHER WATCH MONDAY AFTERNOON FL...RED FLAG WARNING FROM 1 PM EST /12 PM CST/ TO 6 PM EST /5 PM CST/ TODAY ALL COUNTIES. LAKE WIND ADVISORY IN EFFECT UNTIL 5 PM EST THIS AFTERNOON. FREEZE WATCH FROM LATE SUNDAY TONIGHT THROUGH MONDAY MORNING FIRE WEATHER WATCH MONDAY AFTERNOON. GM...GALE WARNING UNTIL 11 AM EST THIS MORNING ALL WATERS. SMALL CRAFT ADVISORY IN EFFECT AFTER 11 AM THIS MORNING FOR ALL WATERS THROUGH MONDAY MORNING. && $$ BLOCK/GIBBS .SHORT TERM... .LONG TERM... && .PRELIMINARY POINT TEMPS/POPS... TALLAHASSEE 56 27 57 25 61 / 10 0 0 0 10 PANAMA CITY 56 33 58 34 60 / 0 0 0 0 10 DOTHAN 53 28 56 28 60 / 0 0 0 0 10 ALBANY 53 28 58 24 60 / 0 0 0 0 10 VALDOSTA 56 28 55 28 60 / 10 0 0 0 10 CROSS CITY 63 27 58 25 64 / 10 0 0 0 10 && .TAE WATCHES/WARNINGS/ADVISORIES... AL...FREEZE WATCH FROM LATE TONIGHT THROUGH MONDAY MORNING FOR THE FOLLOWING ZONES: COFFEE...DALE...GENEVA...HENRY...HOUSTON. LAKE WIND ADVISORY UNTIL 4 PM CST THIS AFTERNOON FOR THE FOLLOWING ZONES: COFFEE...DALE...GENEVA...HENRY...HOUSTON. RED FLAG WARNING FROM 11 AM TO 5 PM CST MONDAY FOR THE FOLLOWING ZONES: COFFEE...DALE...GENEVA...HENRY...HOUSTON. GA...FREEZE WATCH FROM LATE TONIGHT THROUGH MONDAY MORNING FOR THE FOLLOWING ZONES: BAKER...BEN HILL...BERRIEN...BROOKS... CALHOUN...CLAY...COLQUITT...COOK...DECATUR...DOUGHERTY... EARLY...GRADY...IRWIN...LANIER...LEE...LOWNDES...MILLER... MITCHELL...QUITMAN...RANDOLPH...SEMINOLE...TERRELL... THOMAS...TIFT...TURNER...WORTH. LAKE WIND ADVISORY UNTIL 5 PM EST THIS AFTERNOON FOR THE FOLLOWING ZONES: BAKER...BEN HILL...BERRIEN...BROOKS... CALHOUN...CLAY...COLQUITT...COOK...DECATUR...DOUGHERTY... EARLY...GRADY...IRWIN...LANIER...LEE...LOWNDES...MILLER... MITCHELL...QUITMAN...RANDOLPH...SEMINOLE...TERRELL... THOMAS...TIFT...TURNER...WORTH. RED FLAG WARNING FROM 12 PM TO 6 PM EST MONDAY FOR THE FOLLOWING ZONES: BAKER...BEN HILL...BERRIEN...BROOKS...CALHOUN... CLAY...COLQUITT...COOK...DECATUR...DOUGHERTY...EARLY... GRADY...IRWIN...LANIER...LEE...LOWNDES...MILLER... MITCHELL...QUITMAN...RANDOLPH...SEMINOLE...TERRELL... THOMAS...TIFT...TURNER...WORTH. FL...FREEZE WATCH FROM LATE TONIGHT THROUGH MONDAY MORNING FOR THE FOLLOWING ZONES: BAY...CALHOUN...COASTAL WALTON...DIXIE... FRANKLIN...GADSDEN...GULF...HOLMES...INLAND WALTON... JACKSON...JEFFERSON...LAFAYETTE...LEON...LIBERTY... MADISON...TAYLOR...WAKULLA...WASHINGTON. LAKE WIND ADVISORY UNTIL 5 PM EST /4 PM CST/ THIS AFTERNOON FOR THE FOLLOWING ZONES: BAY...CALHOUN...COASTAL WALTON... DIXIE...FRANKLIN...GADSDEN...GULF...HOLMES...INLAND WALTON...JACKSON...JEFFERSON...LAFAYETTE...LEON...LIBERTY... MADISON...TAYLOR...WAKULLA...WASHINGTON. RED FLAG WARNING FROM 12 PM EST /11 AM CST/ TO 6 PM EST /5 PM CST/ MONDAY FOR THE FOLLOWING ZONES: BAY...CALHOUN... DIXIE...FRANKLIN...GADSDEN...GULF...HOLMES...INLAND WALTON...JACKSON...JEFFERSON...LAFAYETTE...LEON...LIBERTY... MADISON...TAYLOR...WAKULLA...WASHINGTON. RED FLAG WARNING FROM 1 PM EST /NOON CST/ TO 6 PM EST /5 PM CST/ THIS AFTERNOON FOR THE FOLLOWING ZONES: BAY...CALHOUN... DIXIE...FRANKLIN...GADSDEN...GULF...HOLMES...INLAND WALTON...JACKSON...JEFFERSON...LAFAYETTE...LEON...LIBERTY... MADISON...TAYLOR...WAKULLA...WASHINGTON. GMZ750...NONE. GMZ755...NONE. GMZ770...NONE. GMZ775...NONE. && $$ BLOCK/GIBBS fl AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TALLAHASSEE FL 405 AM EST SUN DEC 16 2007 ...TORNADO WATCH NUMBER 739 HAS BEEN CANCELLED FOR ALL OF THE FLORIDA EASTERN BIG BEND... ...FLASH FLOOD WATCH HAS BEEN CANCELLED FOR DIXIE AND LAFAYETTE COUNTIES... ...LAKE WIND ADVISORY IN EFFECT TODAY... .SYNOPSIS... VERY BUSY SHIFT. SAT LATE INTO OVERNIGHT HOURS...NEGATIVELY TILTED TROUGH DIGGING EWD FROM LWR MISS VALLEY OH/TENN VALLEYS AIDED STRONG INFLUX OF OLGA GENERATED TROPICAL PLUME INTO CWA. THIS PUSHED SQUALL AND COLD FRONT RAPIDLY EWD. WITH LOW LEVEL REMNANT OF OLGA ACCELERATING NEWD AND BECOMING ABSORBED INTO STRENGTHENING SW STEERING FLOW. THIS AGGRAVATES THE THREAT OF ECHO TRAINING AS NOTED ON AREA RADARS. ADD DEW POINTS NEAR 70 DEGREES ...STRONG WARM FRONT ACROSS SE GA SERVING AS FOCUS FOR LIFT AND VERY GOOD DEEP LYR SHEAR COMBINED TO GENERATE SEVERAL SEVERE THUNDERSTORMS AND TORNADOES OVER CWA SAT EVENING INTO LATE NIGHT ESPECIALLY ALONG INTERSECTION OF ADVANCING SQUALL/WARM FRONT. THIS ACCOUNTED FOR TORNADO AND FLASH FLOOD WATCH. AT 2 AM EST...SQUALL ACROSS DIXIE AND FRONT STARTING TO CATCH UP NOW CROSSING APALACHICOLA AND WILL BARRELING THRU REST OF CWA THRU SUNRISE. CONDITIONS RAPIDLY IMPROVING FROM W-E AND TORNADO WATCH AND MOST OF FLOOD WATCH EXPIRED B4 3 AM EST. AT UPPER LEVELS PROGRESSIVE LARGE-SCALE PATTERN WILL PERSIST THRU SHORT TERM. NEXT UPSTREAM TROUGH WILL MOVE EWD INTO THE PACIFIC NW LATER TODAY. THIS WILL WORK ON UPPER TROUGH/LOW (RESPONSIBLE FOR SATURDAY STORMS) TO TRANSLATE NEWD FROM THE OH VALLEY THIS MORNING INTO NEW ENGLAND AND SRN QUEBEC BY MONDAY MORNING. RESULT IS NEAR ZONAL FLOW ACROSS MOST OF CONUS THRU EARLY WORK WEEK. AT LOWER LEVELS DEEP LOW ASSOCD WITH ABOVE TROUGH OVER THE OH VALLEY THIS MORNING EXPECTED WEAKEN OVER SRN NEW ENGLAND THIS AFTN AS SECONDARY COASTAL LOW SIGNIFICANTLY DEEPENING AS IT MOVES UP ATLC COAST NEWD THROUGH SRN NEW ENGLAND INTO NEW BRUNSWICK. TRAILING COLD FRONT SHOULD QUICKLY MOVE OFF THE SERN ATLANTIC COAST THIS MORNING...AND THROUGH THE FL PENINSULA TO KEY WEST BY LATE AFTERNOON. IN WAKE OF COLD FRONT...COLD HIGH PRESSURE OVER LOUISIANA COAST WILL BUILD EAST AND REACH EASTERN MISSISSIPPI BY DAYBREAK TODAY...WITH RIDGE AXIS EXTENDING EAST ACROSS THE GULF COAST STATES. LOCALLY THIS TRANSLATES TO GUSTY NORTHWEST WINDS AND CLEARING SKIES WITH MUCH COLDER AND DRIER CONDITIONS THROUGH EARLY NEXT WEEK. && .SHORT TERM...(TODAY THROUGH TUESDAY). TODAY...SMALL CHANCE OF SHOWERS WILL LINGER UNTIL AROUND 9-10 AM EST SE BIG BEND. OTHERWISE...BLUSTERY APTLY DESCRIBES THE DAY. TEMPERATURES WILL BE AT LEAST DEGREES COLDER THAN YESTERDAY AND 25 TO 30 DEGREES COLDER COMPARED TO THOSE EXPERIENCED LAST WEEK. PREFERRED A WEIGHTED BLEND TOWARD THE MAV GUIDANCE NUMBERS HERE AS THE MET NUMBERS SEEM JUST A LITTLE TOO COLD. ALSO...EXPECT SUSTAINED WINDS AND/OR FREQUENT GUSTS 20 TO 25 MPH SO LAKE WIND ADVISORY IN EFFECT. TONIGHT...WITH HIGH BUILDING EAST...STRONG COLD AIR ADVECTION WILL BE CONTINUING AND THE FACT THAT SOME LIGHT WINDS WILL CONTINUE THROUGH THE NIGHT ISN`T SIGNIFICANT ENOUGH TO KEEP TEMPERATURES ABOVE FREEZING. WINDS WILL STAY UP ENOUGH TO LIKELY PREVENT FROST. A FREEZE WATCH REMAINS IN EFFECT FOR THE ENTIRE CWA AND WILL LIKELY BE UPGRADED TO A WARNING BY DAY SHIFT. WINDS WILL DECREASE JUST ENOUGH TO PREVENT NEED FOR A WIND CHILL ADVISORY. MONDAY...WINDS WILL FINALLY ABATE...COLD AIRMASS REMAINS IN PLACE. DESPITE AMPLE SUNSHINE...LOW SUN ANGLE WILL ONLY SUPPORT MAX TEMPERATURES IN THE 50S GIVING US OUR SECOND CONSECUTIVE DAY WITH TEMPERATURES BELOW NORMAL. MONDAY NIGHT...HIGH PRESSURE WILL SETTLE OVER THE SOUTHEAST AFFORDING THE COLDEST NIGHT OF THE SEASON THUS FAR. LATEST MAV GUIDANCE IS GOING FOR THE MID 20S AREA WIDE...BUT THE MET IS A LITTLE WARMER. AT THIS POINT GIVEN THAT THE SURFACE RIDGE WILL SET UP A LITTLE NORTH OF THE REGION CONDITIONS AREN`T ALL THAT FAVORABLE FOR A HARD FREEZE...BUT GIVEN HOW COLD AND DRY THIS AIRMASS IS...WILL KEEP TEMPERATURES NEAR 25 DEGREES MOST LOCATIONS. ONE POTENTIAL PROBLEM FOR VERY COLD TEMPERATURES COULD BE SOME CIRRUS MOVING OVERHEAD TOWARD DAYBREAK. TUESDAY...ANOTHER DRY DAY. WITH HIGH MOVING EWD AND SURFACE RIDGE OFFSHORE BUILDING SWWD ACROSS CWA...LOW LEVEL FLOW VEERS TO ELY ALLOWING SOME LOW LEVEL MOISTURE TO ADVECT IN. MINS REBOUND TO SLIGHTLY ABOVE FREEZING INLAND LOCATIONS. && .LONG TERM...WEDNESDAY-FRIDAY. WEDNESDAY INTO THURSDAY...THE STRONG HIGH PRESSURE WILL SHIFT FURTHER ENE IN THE MID-ATLANTIC COAST AND WEDGE DOWN THE APPALACHIANS WHILE COASTAL TROUGH DEVELOPS JUST OFFSHORE. THIS WILL ALLOW THE WINDS TO VEER AROUND TO A MORE EAST-SOUTHEAST DIRECTION OUT AHEAD OF ANOTHER DEVELOPING SYSTEM WEST OF THE REGION. MORNING LOWS WILL AGAIN DROP TO NEAR OR BELOW FREEZING ACROSS INLAND LOCATIONS WITH THE AFTERNOON HIGHS REACHING THE LOW/MID 60S. GFS/ECMWF SHOW WEAK FRONT PUSHING ACROSS THE AREA SOMETIME BEGINNING THURSDAY AFTERNOON AND INTO THE NIGHT. BEYOND THE PERIOD AND INTO THE WEEKEND...THE MODELS SHOW ANOTHER IMPRESSIVE SYSTEM THAT LOOKS TO PUSH EAST ACROSS THE FORECAST AREA SOMETIME AROUND SATURDAY NIGHT INTO SUNDAY. && .AVIATION...IN WAKE OF SQUALL LINE AND COLD FRONT...GUSTY SHIFTING WINDS WILL CONTINUE THROUGH THE DAY. FOLLOWING THE PASSAGE OF THE FRONT WINDS WILL SHIFT TO THE NORTHWEST AND CONDITIONS WILL RAPIDLY IMPROVE TO VFR THROUGH THE REST OF THE FORECAST PERIOD AND BEYOND. && .MARINE... NEW NAM/RUC GUIDANCE SHOWS SUSTAINED SURFACE WINDS TODAY APPROACHING 30 KTS AND 900MB WINDS 35-40KTS. WITH STRONG COLD AIR ADVECTION...GOOD MIXING DOWN EXPECTED SO SUSTAINED GALE FORCE WINDS A BETTER THAN AVERAGE BET...WITH GALE FORCE GUSTS A VERY GOOD WAGER. SO GALE FORCE WARNING ISSUED FOR ALL WATERS UNTIL 11 AM EST TODAY. SCA REMAINS UNTIL MONDAY MORNING. WINDS AND SEAS WILL BEGIN TO RELAX ON MONDAY AS HIGH PRESSURE BUILDS OVER THE WATERS AND DROP BELOW ALL HEADLINE CRITERIA ON TUESDAY. && .FIRE WEATHER...WITH A DRY AIRMASS DESCENDING OVER THE REGION AND WINDY CONDITIONS EXPECTED...RED FLAG WARNING LOOKS GOOD FLORIDA FOR THIS AFTERNOON. WON`T BE DRY ENOUGH ELSEWHERE YET FOR ANY HEADLINES. BY MONDAY...THE AIRMASS DRIES OUT CONSIDERABLY WITH DEWPOINTS DROPPING OFF INTO THE TEENS. WILL THEREFORE ISSUE A FIRE WEATHER WATCH FOR ALL OF THE CWA WITH RH VALUES LIKELY DROPPING OFF INTO THE TEENS. && .PRELIMINARY POINT TEMPS/POPS... TALLAHASSEE 56 27 57 25 / 05 0 0 0 PANAMA CITY 56 33 58 34 / 0 0 0 0 DOTHAN 53 28 56 28 / 0 0 0 0 ALBANY 53 28 58 24 / 0 0 0 0 VALDOSTA 56 28 55 28 / 10 0 0 0 CROSS CITY 63 27 58 25 / 20 0 0 0 && .TAE WATCHES/WARNINGS/ADVISORIES... AL...LAKE WIND ADVISORY IN EFFECT UNTIL 4 PM CST THIS AFTERNOON. FREEZE WATCH FROM LATE SUNDAY TONIGHT THROUGH MONDAY MORNING. FIRE WEATHER WATCH FROM MONDAY MORNING THROUGH AFTERNOON. GA...LAKE WIND ADVISORY IN EFFECT UNTIL 5 PM CST THIS AFTERNOON. FREEZE WATCH FROM LATE SUNDAY TONIGHT THROUGH MONDAY MORNING. FIRE WEATHER WATCH MONDAY AFTERNOON FL...RED FLAG WARNING FROM 1 PM EST /12 PM CST/ TO 6 PM EST /5 PM CST/ TODAY ALL COUNTIES. LAKE WIND ADVISORY IN EFFECT UNTIL 5 PM EST THIS AFTERNOON. FLASH FLOOD WATCH IN EFFECT FOR TAYLOR AND DIXIE COUNTIES UNTIL 6 AM EST THIS MORNING. FREEZE WATCH FROM LATE SUNDAY TONIGHT THROUGH MONDAY MORNING FIRE WEATHER WATCH MONDAY AFTERNOON. GM...GALE WARNING UNTIL 11 AM EST THIS MORNING ALL WATERS. SMALL CRAFT ADVISORY IN EFFECT AFTER 11 AM THIS MORNING FOR ALL WATERS THROUGH MONDAY MORNING. && $$ BLOCK/GIBBS fl AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHARLESTON SC 1228 PM EST SUN DEC 16 2007 .SYNOPSIS... HIGH PRESSURE WILL BUILD IN AND REMAIN THE PRIMARY FEATURE THROUGH THURSDAY. ANOTHER COLD FRONT WILL MOVE THROUGH THE AREA FRIDAY. HIGH PRESSURE WILL RETURN FOR THE FIRST HALF OF NEXT WEEKEND. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... PRIMARY COLD FRONT MOVED OFF THE COAST BETWEEN 13 AND 1330Z...EASILY VISIBLE ON WSR-88D AS A FINE-LINE AND ALSO IN SFC WIND DIRECTIONS. STRONGEST WIND GUSTS OF THE MORNING OCCURRED BRIEFLY WITH THIS BOUNDARY...WITH SPEEDS SETTLING DOWN INTO THE 15-25 KT RANGE. PRECIPITATION HAS ENDED ACROSS THE ENTIRE CWFA. BACK EDGE OF THE FRONTAL CLOUD BAND CURRENTLY BISECTS THE CWFA FROM N TO S AND MOST COASTAL AREAS SHOULD BE SCATTERING OUT BY NOON. A LARGE EXPANSE OF WRAP-AROUND STRATOCUMULUS OVERCAST IS PROGRESSING THROUGH NORTHERN AND CENTRAL GEORGIA. ALTHOUGH THE LEADING EDGE OF THIS CLOUDINESS IS BEGINNING TO BREAK UP...TRENDS AND MODEL TIME HEIGHTS INDICATE CLOUDS COULD ENCROACH ON OUR SW GEORGIA ZONES AGAIN DURING THE AFTERNOON. MAX TEMP FORECAST FOR TODAY IS DIFFICULT SINCE THERE ARE SEVERAL VARIABLES IN QUESTION. THE PREDOMINANT INFLUENCE WILL BE FROM INCREASING COLD ADVECTION FROM STRONG HIGH PRESSURE BUILDING IN FROM THE WEST. HOWEVER LOW-LEVEL WINDS VEER TO WNW AND NW DURING THE DAY...RESULTING IN CONSIDERABLE DOWNSLOPE COMPRESSIONAL PATTERN. SOME DOWNSLOPE WARMING IS LIKELY TO BEGIN DURING THE AFTERNOON. THE AMOUNT OF SUNSHINE IS ALSO DIFFICULT TO PREDICT GIVEN THE UNCERTAINTY WITH THE WRAP-AROUND CLOUDINESS. UPDATED TODAY/S TEMPS VIA A SLIGHTLY WARMER TREND THAN THE HOURLY RUC AND NAM-12 PROGS. TEMPS COULD LEVEL OFF DURING THE EARLY AFTERNOON FOR TWO TO THREE HOURS DURING THE STRONGEST DOWNSLOPE FLOW BEFORE COLD ADVECTION TAKES OVER. WILL KEEP WIND ADVISORY IN PLACE TODAY. WINDS SHOULD INCREASE INTO THE EARLY AFTERNOON AS COLD ADVECTION INCREASES AND MIXING HEIGHT INCREASES BY 1-2000 FT. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM MONDAY/... MAIN ISSUE FOR TONIGHT WILL BE THE FREEZING TEMPERATURES THAT WILL ADVECT TOWARD THE COAST WITHIN WEST TO NORTHWEST SURFACE FLOW. 00Z GUIDANCE HAS ACTUALLY RAISED OVERNIGHT LOWS A DEGREE OR TWO...WHICH HAS LOWERED CONFIDENCE THAT THE COASTAL GEORGIA COUNTIES MAY REACH FREEZE WARNING CRITERIA. HAVE THUS NOT UPGRADED TO A FREEZE WARNING FOR THESE LOCATIONS AND INSTEAD MAINTAINED THE FREEZE WATCH. SUBSEQUENT SHIFTS WILL NEED TO MONITOR MODEL TRENDS TO DETERMINE WHETHER THE WATCH SHOULD BE UPGRADED OR DROPPED. AT THIS POINT HAVE INDICATED LOW TEMPERATURES FALLING INTO THE MID 20S FAR INLAND TO THE LOWER 30S NEAR THE COAST. MONDAY WILL BE A CLEAR AND CHILLY DAY...AS THE COLD AIR MASS REMAINS OVER THE REGION AND SURFACE HIGH PRESSURE CONTINUES TO BUILD EASTWARD. HIGH TEMPERATURES WILL ONLY REACH THE LOWER TO MID 50S DESPITE FULL SUNSHINE...SEVERAL DEGREES BELOW SEASONAL NORMS. LAKE WINDS...WINDS OVER LAKE MOULTRIE WILL REMAIN WITHIN ADVISORY CRITERIA OVERNIGHT...THEN DIMINISH BELOW CRITERIA BY MONDAY MORNING. && .LONG TERM /MONDAY THROUGH SUNDAY/... MONDAY NIGHT...HIGH PRESSURE WILL ALLOW BOUNDARY LAYER DECOUPLING...SUPPORTING EXCELLENT RADIATIONAL COOLING AND ALLOWING TEMPERATURES TO FALL INTO THE 20S AT MOST LOCATIONS AWAY FROM THE COAST. AT THE COAST...12Z NAM/GFS GUIDANCE DIFFERS REGARDING THE POSITION OF THE CENTER OF THE SURFACE HIGH AND RESULTING WIND DIRECTION. SPECIFICALLY...THE 12Z NAM SUGGESTS THAT THE LAND BREEZE WILL DOMINATE...PRODUCING A LIGHT OFFSHORE FLOW ACROSS THE ENTIRE COASTLINE AND PUSHING COLD AIR RIGHT TO THE COASTAL ISLANDS/BEACHES. ON THE OTHER HAND...THE 12Z GFS DEVELOPS A WEAK SURFACE TROUGH OVER THE COASTAL WATERS...ALLOWING WINDS TO TURN SLIGHTLY ONSHORE ALONG THE IMMEDIATE COAST. THE DIFFERENCES IN THESE SOLUTIONS...WHICH ARE BOTH REASONABLE...REMAIN SUBTLE BUT TRANSLATES TO POSSIBLE LOW TEMPERATURE RANGE OF 10-15F ALONG THE IMMEDIATE COAST...ESPECIALLY ALONG THE GEORGIA COAST. THIS FORECAST WILL REPRESENT A COMPROMISE...HOLDING FREEZING TEMPERATURES AWAY FROM THE IMMEDIATE COAST...BUT PUSHING TEMPERATURES TO AROUND FREEZING JUST INLAND. TUESDAY...AS THE CENTER OF HIGH PRESSURE SHIFTS OFF THE COAST AND NE OF THE REGION...INCREASING ONSHORE FLOW WILL ALLOW TEMPERATURES TO RECOVER TO CLOSE TO NORMAL LEVELS. WEDNESDAY AND THURSDAY...UNDERCUT 12Z GFS MOS POPS...LEAVING RAIN FREE FORECASTS...AS MODEL APPEARS OVERDONE WITH AMOUNT OF MOISTURE PROVIDED BY ONSHORE FLOW. ALSO...AS EXPECTED...MEDIUM RANGE GUIDANCE HAS ALTERED THE LATE WEEK SCENARIO. SPECIFICALLY...INSTEAD OF A WELL DEVELOPED LOW PRESSURE PUSHING THROUGH THE SE...GUIDANCE HAS TRENDED FARTHER NORTH WITH LOW PRESSURE/ASSOCIATED WARM FRONT THURSDAY...AND SUGGESTS A WEAKENING COLD FROPA FRIDAY. CONTINUED SLIGHT CHANCE POPS THURSDAY NIGHT/FRIDAY TO ACCOUNT FOR THE FROPA...AND BUMPED TEMPERATURES UP A FEW DEGREES THURSDAY/FRIDAY. THEN...INDICATED LITTLE AIRMASS CHANGE...WITH ABOVE NORMAL TEMPERATURES...TO START THE WEEKEND. OVERALL...CONFIDENCE IN THE THURSDAY/FRIDAY FORECAST REMAINS QUITE LOW. && .AVIATION /18Z SUNDAY THROUGH FRIDAY/... VFR CONDITIONS WILL PREVAL THROUGH THE TAF PERIOD. MAIN CONCERN IS THE GUSTY WINDS THAT WILL PERSIST BEHIND THE COLD FRONT THIS AFTERNOON. AFTER SUNSET...WINDS WILL NOT DECOUPLE BUT WILL DECREASE TO AROUND 10 KNOTS. THEREFORE...WIND SHEAR WILL BE AN ISSUE TONIGHT AT BOTH TAF SITES. THUS HAVE INTRODUCED 30 KT WIND SHEAR AROUND 0230Z GIVING THE WINDS A LITTLE TIME TO DECREASE. EXPECT IT TO UNTIL SUNRISE WHEN THE MIXING WILL COMMENCE. EXTENDED AVIATION OUTLOOK...VFR CONDITIONS WILL PREVAIL. && .MARINE... GALE WARNING FOR ALL MARINE ZONES THROUGH AT LEAST TODAY. SPEEDS WILL INCREASE THROUGH THE AFTERNOON AS COLD ADVECTION MIXES INCREASINGLY WELL OVER THE SLIGHTLY WARMER WATERS. IN THE HARBOR...THE GALE POTENTIAL EXISTS MAINLY IN GUSTS. MARINE CONDITIONS WILL GRADUALLY IMPROVE BY MONDAY MORNING IN THE NEARSHORE WATERS AND ACROSS THE OUTER GA WATERS BY MIDDAY MONDAY. HIGH PRESSURE WILL THEN DOMINATE MARINE CONDITIONS EARLY IN THE WEEK. COASTAL TROUGHING ON THE SOUTHERN RIM OF THE SURFACE RIDGE MAY ENHANCE WINDS/SEAS A BIT THROUGH WEDNESDAY. AHEAD OF ANOTHER APPROACHING COLD FRONT THURSDAY INTO FRIDAY...S WINDS MAY INCREASE. HOWEVER...EXPECT CONDITIONS TO REMAIN BELOW ADVISORY THRESHOLDS MONDAY PM THROUGH FRIDAY. && .FIRE WEATHER... EXPECT CRITICAL WINDS TODAY...BUT MINIMUM RELATIVE HUMIDITY VALUES SHOULD HOLD ABOVE CRITICAL VALUES. CRITICAL RELATIVE HUMIDITY APPEARS LIKELY AT MANY LOCATIONS ON MONDAY...BUT WINDS WILL REMAIN BELOW CRITICAL THRESHOLDS. TUESDAY...NEAR CRITICAL RELATIVE HUMIDITY APPEARS LIKELY INLAND. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...WIND ADVISORY UNTIL 7 PM EST THIS EVENING FOR GAZ087-088- 099>101-114>119-137>141. FREEZE WATCH FROM LATE TONIGHT THROUGH MONDAY MORNING FOR GAZ117-119-139-141. SC...WIND ADVISORY UNTIL 7 PM EST THIS EVENING FOR SCZ040-042>045- 047>051. MARINE...GALE WARNING UNTIL 5 PM EST THIS AFTERNOON FOR AMZ330-352-354. GALE WARNING UNTIL 7 PM EST THIS EVENING FOR AMZ350. GALE WARNING UNTIL 5 AM EST MONDAY FOR AMZ374. && $$ JRL/REB ga AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHARLESTON SC 1253 PM EST SAT DEC 15 2007 .SYNOPSIS... SURFACE HIGH PRESSURE WILL CONTINUE TO WEDGE DOWN THE EAST COAST TODAY WHILE A COASTAL TROUGH DEVELOPS OFFSHORE. A LOW PRESSURE SYSTEM WILL MOVE NORTHWEST OF THE AREA THIS AFTERNOON...BEFORE A STRONG COLD FRONT SWEEPS THROUGH THE REGION SUN MORNING. COOL HIGH PRESSURE WILL BUILD OVER THE REGION SUN THROUGH MON...THEN SHIFT INTO THE NORTH ATLANTIC TUE AND WED. ANOTHER COLD FRONT WILL AFFECT THE AREA LATE IN THE WEEK. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... HIGH PRES WEDGE HAS CONTINUED TO STRENGTHEN THIS MORNING WITH WINDS NOW SOLIDLY NE OR E ACROSS THE MAJORITY OF OUR CWFA. DENSE FOG BRIEFLY DEVELOPED AT CHS AROUND 14Z WHEN THE SRN EDGE OF THE FRONT MOVED S INTO THE TRI-COUNTY AREA. REGIONAL WEB CAMS ALSO SHOWED A BRIEF DROP IN VSBY...ESPECIALLY ON ELEVATED BRIDGES. ALTHOUGH CONDITIONS HAVE SINCE IMPROVED AT THE SFC...THE BOUNDARY IS NOT EXPECTED TO MOVE MUCH FARTHER SE TODAY...THUS WE WILL LIKELY BE OSCILLATING BETWEEN FAIRLY DENSE FOG AND ONLY LIGHT MIST. LAST TWO HRS OF VIS SATELLITE SHOW CLOUD COVER HAS FINALLY GONE OVERCAST OVER MOST OF THE SOUTHEAST UNITED STATES. THE INCREASE IN LOW OVERCAST CLOUD COVER OCCURRED 4-6 HRS LATER THAN THE MODEL CONSENSUS FROM YESTERDAY/S 12Z RUNS. REGIONAL RADAR SHOWS SCATTERED LIGHT PRECIP NOW DEVELOPING OVER CENTRAL AND SOUTHERN GA AS WELL AS ALONG THE SOUTH GA COAST LINE. THE MODELS CONTINUE TO STRUGGLE WITH THIS SYSTEM. EVEN THE NEW 12Z NAM HAD A POOR INITIALIZATION OF THE COASTAL TROUGH. IT SHOWS ONLY A WEAK BAROCLINIC ZONE ALONG THE SC/GA COAST WHILE MSAS AND SFC OBS SHOW A MUCH STRONGER INFLECTION /TEMP GRAD OF 11C BETWEEN CHS AND BUOY 41004/. HOWEVER...THE RUC AND THE NAM DO SEEM TO BETTER REFLECT THE PROGRESS OF PRECIP DEVELOPMENT THROUGH THIS AFTERNOON WITH A MUCH LESS AGGRESSIVE TACK. OUR BEST CHANCE FOR WIDESPREAD PRECIP APPEARS TO BE LATE THIS AFTERNOON THROUGH TONIGHT AS THE COASTAL TROUGH IS STRONGEST AND ISENTROPIC ASCENT IS MAXIMIZED. SPC STILL INCLUDES MOST OF OUR AREA IN A SLIGHT RISK FOR TODAY. ALTHOUGH INSTABILITY MAY BE COMPROMISED BY THE HEAVY CLOUD COVER...THERE WILL BE STRONG DYNAMICS ASSOCIATED WITH THIS SYSTEM. HAVE THUS MAINTAINED THE ONGOING CHANCE FOR THUNDERSTORMS MAINLY IN THE SOUTHERNMOST COUNTIES AND OVER THE WATERS WHERE ANY INSTABILITY WILL BE MAXIMIZED ALONG THE WARM FRONTAL BOUNDARY. MADE EARLY AFTERNOON TWEAKS TO TEMPS AND WINDS. && .SHORT TERM /6 PM THIS EVENING THROUGH SUNDAY NIGHT/... AFTER THE WARM FRONT MOVES NORTHWARD AROUND 00Z TONIGHT...THERE MAY BE A BRIEF LULL IN THE PRECIP WITHIN THE EASTERN HALF OF THE FORECAST AREA AS THE FOCUS SHIFTS TO THE COLD FRONT APPROACHING FROM THE WEST. FRONTAL PASSAGE WILL OCCUR SUNDAY MORNING...WITH DRYING AND CLEARING OCCURRING BY SUNDAY AFTERNOON. STRONG COLD ADVECTION BEHIND THE FRONT WILL ALLOW FOR BREEZY CONDITIONS AND MUCH COOLER TEMPERATURES ON SUNDAY. EXPECT AFTERNOON HIGHS TO BE SUPPRESSED IN THE UPPER 50S TO LOWER 60S. LAKE WINDS...HAVE ISSUED A LAKE WIND ADVISORY FOR LAKE MOULTRIE BEGINNING 10Z ON SUNDAY...SINCE STRONG COLD ADVECTION OVER THE RELATIVELY WARMER LAKE WATERS WILL ALLOW MIXING TO TAP INTO A 35 TO 40 KT LOW LEVEL JET. && .LONG TERM /MONDAY THROUGH SATURDAY/... THE MAIN FCST CONCERN DURING THE LONG TERM WILL BE LOW TEMPS FOR SUNDAY NIGHT AND MONDAY NIGHT. DURING THIS TIME WE WILL BE LOOKING AT OUR COLDEST WX SINCE MID NOVEMBER...AND SOME LOCATIONS WILL EVEN EXPERIENCE THEIR COLDEST WX OF THE SEASON. SUNDAY NIGHT WILL BE PURELY A COLD AIR ADVECTION NIGHT...WITH LOWS IN THE 20S AND 30S ALL AREAS BY MONDAY MORNING. HOWEVER...THE CURRENT THOUGHTS ARE THAT COASTAL SE GA WILL REMAIN ABOVE FREEZING AND THERE WILL BE TOO MUCH WIND FOR ANY FROST. THUS THE SEASONAL FROST/FREEZE PROGRAM WILL CONTINUE FOR THESE AREAS. MONDAY NIGHT IS A BETTER RADIATION NIGHT ACROSS INLAND LOCATIONS...BUT THE SECOND NIGHT IS OFTEN NOT AS COLD ALONG COASTAL AREAS DURING A COLD WX OUTBREAK. THIS AGAIN LOOKS TO BE THE CASE AS COLD AIR ADVECTION HAS ENDED AND THERE IS EVEN A SLIGHT ONSHORE COMPONENT TO THE WIND OFF THE SURFACE. STILL WE CAN EXPECT LOWS AGAIN IN THE 20S AND 30S JUST ABOUT EVERYWHERE...WITH FROST INLAND. WILL KEEP A CLOSE WATCH ON FROST POTENTIAL OVER COASTAL SE GA TO SEE IF ENOUGH OCCURS TO END THE FROST/FREEZE PROGRAM FOR THE REST OF THE WINTER SEASON. NOT MUCH HAPPENING DURING MID WEEK AS HIGH PRES OVER THE AREA TUESDAY WILL SHIFT INTO THE ATLC WEDNESDAY. THIS WILL RESULT IN A GRADUAL WARMING TREND AS ONSHORE FETCH RETURNS...BUT THIS WILL RESULT IN ONLY SOME STRATOCUMULUS OR CUMULUS HUMILIS RETURNING TO THE FCST AREA...AND NOT ANY RAIN. NEXT COLD FRONT TO IMPACT THE REGION LATE IN THE WEEK...BUT WITH ZONAL FLOW THE RAIN CHANCES LOOK SLIM. WILL PROBABLY LOWER OR REMOVE POPS FROM THE FCST THURSDAY AND FRIDAY. TEMPS WILL HAVE WARMED BACK ABOVE NORMAL DURING THAT TIME. LAKE WINDS EXTENDED...CONTINUED COLD AIR ADVECTION AND GEOSTROPHIC WINDS OF 30 KT OR HIGHER WILL RESULT IN THE CONTINUATION OF THE LAKE WIND ADVISORY FOR LAKE MOULTRIE THROUGH AT LEAST MONDAY MORNING. CONDITIONS WILL GRADUALLY IMPROVE OVER THE LAKE BY LATE MONDAY/MONDAY NIGHT. && .AVIATION /18Z SATURDAY THROUGH THURSDAY/... IFR CONDITIONS EXPECTED TO CONTINUE AT CHS THROUGH TONIGHT ALONG THE WEDGE BOUNDARY. RAIN HAS BEEN SLOW TO MATERIALIZE AS FAR N AS CHS TERMINAL BUT LIGHT RAIN WILL OVERSPREAD THE AREA PRETTY SOON. THE HEAVIEST RAIN IS EXPECTED WITH THE COLD FRONT LATE TONIGHT. WIND SHEAR STILL EXPECTED OVERNIGHT WITH THE STRONG LLVL JET DEVELOPING AHEAD OF THE APPROACHING UPPER LOW. CONDITIONS WILL RAPIDLY IMPROVE BY EARLY TO MID SUN MORNING. CIGS HAVE ONLY RECENTLY DROPPED TO MVFR AT SAV BUT WILL REMAIN THERE FOR THE REST OF THE AFTERNOON AND EVENTUALLY DROP TO IFR. SIMILAR TO CHS...HEAVIEST PRECIP EXPECTED LATE TONIGHT WITH THE FROPA. ALSO INCLUDED WIND SHEAR OVERNIGHT. GUSTY WINDS EXPECTED AT BOTH TERMS DURING THE DAY SUN WITH STRONG COLD ADVECTION AND LLVL JET BEHIND THE FRONT. EXTENDED AVIATION OUTLOOK...VFR CONDITIONS WILL PREVAIL. && .MARINE... COASTAL TROUGH HAS TIGHTENED CONSIDERABLY ALONG THE SC COAST NEAR CHARLESTON HARBOR. WINDS IN THE HARBOR HAVE BEEN BLOWING 15-20 KT FOR TWO HRS NOW AND SIMILAR SPEEDS SHOWING UP WITHIN 10 NM OF THE COAST PER BUOY OBS. ISSUING QUICK UPDATE TO INCREASE WINDS TO 15-20 KT IN THE HARBOR AND SC NEARSHORE. DETERIORATING MARINE CONDITIONS EXPECTED TONIGHT AS THE LOW LEVEL JET INTENSIFIES TO 45 TO 50 KT AHEAD OF A STRONG COLD FRONT APPROACHING FROM THE WEST. HAVE MAINTAINED ONGOING SMALL CRAFT ADVISORIES BEGINNING TONIGHT FOR ALL NEARSHORE WATERS AND THE CHARLESTON HARBOR...AS SOUTHERLY WINDS VEER TO SOUTHWESTERLY AND STEADILY INCREASE IN SPEED. COLD ADVECTION INITIATING BEHIND THE FRONT WILL ALLOW OFFSHORE WINDS TO FURTHER SURGE UNDER ENHANCED MIXING. THUS HAVE ISSUED A GALE WATCH IN THE OUTER GEORGIA WATERS BEGINNING 10Z SUNDAY MORNING FOR GALE FORCE GUSTS. THE COMBINATION OF A TIGHT PRESSURE GRADIENT DUE TO STRONG HIGH PRESSURE BUILDING IN BEHIND THE FRONT...AS WELL AS THE LINGERING COLD AIR MASS OVER THE WATERS...WILL ALLOW STRONG WINDS TO CONTINUE THROUGH SUNDAY. SEAS WILL ALSO BUILD IN RESPONSE TO THE STRONG WINDS. WAVE HEIGHTS OF 5 TO 7 FT IN THE NEARSHORE SC WATERS AND 7 TO 9 FT IN THE OFFSHORE GA MARINE ZONES ARE POSSIBLE TONIGHT THROUGH SUNDAY. WILL KEEP HEADLINES GOING ACROSS THE COASTAL WATERS SUNDAY NIGHT AS GEOSTROPHIC WINDS ARE STILL 30 KT OR HIGHER AND COLD AIR ADVECTION PERSISTS. DESPITE THE OFFSHORE FETCH...THE WNA GUIDANCE LOOKS A LITTLE UNDERDONE. LOCAL NOMOGRAM AND WAVE FCST TOOL ON AWIPS SUPPORTS SEAS ABOUT A FOOT OR TWO HIGHER THAN GUIDANCE AND WILL FOLLOW. CONDITIONS WILL SLOWLY IMPROVE MONDAY AS PRES GRADIENT RELAXES BY NIGHTFALL...AND A FURTHER IMPROVEMENT WILL DEVELOP MONDAY NIGHT AND TUESDAY AS THE HIGH SHIFTS FURTHER E AND INTO THE AREA. SEAS WILL BE SLOWER THAN WINDS IN COMING DOWN...AND WILL STILL HAVE SOME 6 OR 8 FT SEAS OVER THE OUTER GA WATERS INTO MONDAY. THE BEST MARINE CONDITIONS OF THIS FCST PERIOD WILL BE TUESDAY AND WEDNESDAY AS WEAK HIGH PRES IS FOUND N AND NE OF THE COASTAL WATERS ALLOWING FOR LIGHT NE-E WINDS AND SEAS NO HIGHER THAN 3 OR 4 FT. && .FIRE WEATHER... EXPECT CRITICAL/NEAR CRITICAL WINDS AFTER THE COLD FRONT SWEEPS THROUGH THE REGION SUNDAY. AT THIS POINT IT APPEAR THAT SUNDAY MINIMUM RELATIVE HUMIDITY VALUES SHOULD REMAIN AT LEAST 10 PERCENT ABOVE CRITICAL VALUES. FOR MONDAY...CRITICAL RELATIVE HUMIDITY APPEARS LIKELY AT MOST INLAND LOCATIONS...BUT WINDS WILL REMAIN BELOW CRITICAL THRESHOLDS. CRITICAL OR NEAR CRITICAL RH VALUES ARE EXPECTED BOTH MONDAY AND TUESDAY AFTN. HOWEVER...WINDS WILL BE ON A CONTINUED DOWNWARDS TREND MONDAY WITH A FURTHER DECREASE TUESDAY. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...NONE. SC...LAKE WIND ADVISORY FROM 5 AM SUNDAY TO 5 AM EST MONDAY FOR SCZ045. MARINE...SMALL CRAFT ADVISORY FROM 7 PM THIS EVENING TO 5 AM EST MONDAY FOR AMZ330-350-352-354. GALE WATCH FROM LATE TONIGHT THROUGH SUNDAY EVENING FOR AMZ374. SMALL CRAFT ADVISORY FROM 7 PM THIS EVENING TO 5 AM EST SUNDAY FOR AMZ374. && $$ JRL ga AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LINCOLN IL 1034 AM CST SUN DEC 16 2007 .DISCUSSION... ISSUED 1022 AM CST SUN DEC 16 2007 SURFACE LOW PRESSURE SYSTEM PUSHING UP THE OHIO RIVER VALLEY THIS MORNING...LEAVING BEHIND GUSTY WINDS IN ITS WAKE AS THE PRESSURE GRADIENT IS VERY SLOW TO RELAX. A TEMPORARY CLEARING OF THE CLOUDS THIS MORNING IS GIVING WAY TO STRATUS THAT IS MOVING IN FROM THE NW. TEMPERATURES ARE SLOW TO RISE...AND THAT SLOW RISE TREND SHOULD CONTINUE ONCE THE CLOUD COVER MOVES IN. MORE DRY AIR IMMEDIATELY TO THE WEST...AND ABOVE THE CLOUDS THEMSELVES SHOULD HELP TO ERODE THE BLANKET OF STRATUS BY LATER THIS AFTERNOON. WILL BE UPDATING THE FORECAST FOR HOURLY TEMPS...CLOUDS...AND TO REMOVE MORNING WORDING. HJS && .AVIATION... ISSUED 530 AM CST SUN DEC 16 2007 STRONG STORM SYSTEM IS PULLING AWAY... BUT STILL DEALING WITH MVFR TO IFR CIGS ACROSS THE EAST. PLENTY OF BREAKS OPENING UP ACROSS WESTERN IL AND EASTERN IOWA... BUT MORE LOW CLOUDS CONTINUE TO LOOM OVER MUCH OF IOWA. RUC13 AND LOCAL 20KM ARW HAS A GOOD HANDLE ON CURRENT SITUATION... AND THESE MODELS SUGGEST THAT ANY BREAKS IN THE WEST WILL FILL IN AGAIN TOWARDS MIDDAY AS A WEAK SHORTWAVE CURRENTLY EXTENDING FROM SOUTHERN MINNESOTA TO NORTHWESTERN ONTARIO DROPS ACROSS THE AREA. WITH NORTHWESTERLY FLOW OVER SNOWPACK... I THINK ANY BREAKS IN THE EAST WILL BE RATHER SHORT-LIVED... WITH THE BACK EDGE OF LOW CLOUD COVER LIKELY TO HANG AROUND THIS MORNING AFTER SUNRISE... WITH BMI/DEC PLAYING WITH THE FRINGES MUCH OF THE AFTERNOON. FINALLY... SKIES SHOULD CLEAR OUT AT ALL STATIONS LATE TONIGHT. BUT WITH WEAK SFC WARM ADVECTION KICKING IN... WOULD COULD SEE SOME FOG DEVELOP TOWARDS DAWN MONDAY MORNING. HARDIMAN && .PREV DISCUSSION... ISSUED 329 AM CST SUN DEC 16 2007 SHORT TERM...TODAY THROUGH TUESDAY. STRONG WINTER STORM IS RAPIDLY MOVING AWAY FROM THE REGION THIS MORNING. 3 AM SFC ANALYSIS HAD 992 MB LOW NEAR COLUMBUS OH... AND IT IS CONTINUING TO DEEPEN WHILE WEAKER SFC LOW BECOMES MORE ORGANIZED ALONG THE NORTH CAROLINA COAST. VERY IMPRESSIVE SYSTEM SO FAR AND WE ONLY GOT A PIECE OF ITS EARLY STAGES. SNOWFALL REPORTS AND RADAR OVERNIGHT INDICATES THAT IMPRESSIVE MESOSCALE BANDING DID OCCUR FARTHER WEST AS WAS FEARED YESTERDAY MORNING. SFC LOW DID HUG QUITE A BIT CLOSER TO THE OHIO RIVER THAN MOST MODELS SUGGESTED 24 HRS AGO. AS A RESULT... THE POCKET OF HEAVIEST ACCUMULATIONS APPEARS TO BE ALONG AND JUST EAST OF THE I-55 CORRIDOR BETWEEN SPI AND BMI... WITH HIGHEST AMOUNTS RUNNING ACROSS EASTERN MCLEAN COUNTY SOUTHWARD INTO MACON COUNTY. STILL SEEING SOME LIGHT TO LOCALLY MODERATE BANDS THAT STUBBORNLY KEEP RE-ENHANCING OVER THE FAR EASTERN CWA. WATER VAPOR IMAGERY SUGGESTS NARROW TROWAL MAY BE HOOKING BACK INTO NORTHWESTERN INDIANA... HELPING TO RE-ENHANCE MESOSCALE BANDING. ALSO NOTED THAT BOTH THE NAM AND GFS-BASED LOCAL 20KM WRF RUNS FROM 00Z... WHICH HAVE HANDLED THE LOCATION OF THE BANDING EXCEPTIONALLY WELL THIS EVENING... CONTINUE TO HINT AT BANDING PERSISTING IN THE FAR EASTERN CWA THROUGH 12Z BEFORE FINALLY GIVING UP THE GHOST. THEREFORE... WE DECIDED TO KEEP THE WARNINGS GOING FOR ALL COUNTIES ALONG AND EAST OF THE I-57 CORRIDOR... BUT WE DROPPED BACK THE EXPIRATION TIME TO 8 AM/14Z. ALL OTHER WARNINGS HAVE BEEN DROPPED. GUSTY NORTHWEST WINDS WILL CONTINUE TO BE A PROBLEM TODAY CAUSING PLENTY OF DRIFTING... ESPECIALLY IN NORTHERN AND EASTERN SECTIONS OF THE CWA. BLOWING SNOW NOT EXPECTED TO BE A BIG ISSUE AT LEAST IN TERMS OF LOFTING AND SUBSEQUENT VISBY RESTRICTIONS. WARM ADVECTION LOOKS TO KICK IN MONDAY AFTERNOON. MOS GUIDANCE STILL APPEARS TOO HIGH AND DOES NOT SEEM TO BE TAKING INTO ACCOUNT FINAL SNOWFALL AMOUNTS. WARMER AIR WILL HAVE THE BEST CHANCE OF MAKING IT INTO AREAS SOUTH OF I-72 MONDAY... FARTHER NORTH... KEPT MAX TEMPS CLOSER TO NAM 2 METER TEMPS... WITH MOST AREAS ALONG THE I-74 CORRIDOR STAYING BELOW FREEZING. OTHERWISE... A SLOW WARM UP LOOKS TO CONTINUE THROUGH TUESDAY. DRY ATMOSPHERE SHOULD HOPEFULLY KEEP FOG THREAT AT BAY DESPITE WARM ADVECTION... BUT WE COULD SEE SOME DIURNAL STRATOCU DECKS DEVELOP ACROSS NORTHERN SECTIONS MONDAY NIGHT AND TUESDAY. LONG TERM...WEDNESDAY AND THURSDAY. NEXT DISTURBANCE LOOKS TO AFFECT THE AREA WEDNESDAY NIGHT INTO THURSDAY... MAINLY BRINGING LIGHT RAIN AND SNOW TO THE AREA. COULD SEE A MIXED BAG ALONG THE I-72 CORRIDOR WED NIGHT... BUT QPF AMOUNTS STILL SHOULD BE LOW... THUS DO NOT EXPECT MAJOR PROBLEMS. ACTIVE PATTERN DOES LOOK TO CONTINUE THOUGH... WITH PERHAPS ANOTHER WINTRY SYSTEM AFFECTING THE AREA NEXT WEEKEND. WHY NOT MAKE IT 4 IN A ROW. HARDIMAN && .ILX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ il AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LINCOLN IL 530 AM CST SUN DEC 16 2007 .DISCUSSION... ISSUED 329 AM CST SUN DEC 16 2007 SHORT TERM...TODAY THROUGH TUESDAY. STRONG WINTER STORM IS RAPIDLY MOVING AWAY FROM THE REGION THIS MORNING. 3 AM SFC ANALYSIS HAD 992 MB LOW NEAR COLUMBUS OH... AND IT IS CONTINUING TO DEEPEN WHILE WEAKER SFC LOW BECOMES MORE ORGANIZED ALONG THE NORTH CAROLINA COAST. VERY IMPRESSIVE SYSTEM SO FAR AND WE ONLY GOT A PIECE OF ITS EARLY STAGES. SNOWFALL REPORTS AND RADAR OVERNIGHT INDICATES THAT IMPRESSIVE MESOSCALE BANDING DID OCCUR FARTHER WEST AS WAS FEARED YESTERDAY MORNING. SFC LOW DID HUG QUITE A BIT CLOSER TO THE OHIO RIVER THAN MOST MODELS SUGGESTED 24 HRS AGO. AS A RESULT... THE POCKET OF HEAVIEST ACCUMULATIONS APPEARS TO BE ALONG AND JUST EAST OF THE I-55 CORRIDOR BETWEEN SPI AND BMI... WITH HIGHEST AMOUNTS RUNNING ACROSS EASTERN MCLEAN COUNTY SOUTHWARD INTO MACON COUNTY. STILL SEEING SOME LIGHT TO LOCALLY MODERATE BANDS THAT STUBBORNLY KEEP RE-ENHANCING OVER THE FAR EASTERN CWA. WATER VAPOR IMAGERY SUGGESTS NARROW TROWAL MAY BE HOOKING BACK INTO NORTHWESTERN INDIANA... HELPING TO RE-ENHANCE MESOSCALE BANDING. ALSO NOTED THAT BOTH THE NAM AND GFS-BASED LOCAL 20KM WRF RUNS FROM 00Z... WHICH HAVE HANDLED THE LOCATION OF THE BANDING EXCEPTIONALLY WELL THIS EVENING... CONTINUE TO HINT AT BANDING PERSISTING IN THE FAR EASTERN CWA THROUGH 12Z BEFORE FINALLY GIVING UP THE GHOST. THEREFORE... WE DECIDED TO KEEP THE WARNINGS GOING FOR ALL COUNTIES ALONG AND EAST OF THE I-57 CORRIDOR... BUT WE DROPPED BACK THE EXPIRATION TIME TO 8 AM/14Z. ALL OTHER WARNINGS HAVE BEEN DROPPED. GUSTY NORTHWEST WINDS WILL CONTINUE TO BE A PROBLEM TODAY CAUSING PLENTY OF DRIFTING... ESPECIALLY IN NORTHERN AND EASTERN SECTIONS OF THE CWA. BLOWING SNOW NOT EXPECTED TO BE A BIG ISSUE AT LEAST IN TERMS OF LOFTING AND SUBSEQUENT VISBY RESTRICTIONS. WARM ADVECTION LOOKS TO KICK IN MONDAY AFTERNOON. MOS GUIDANCE STILL APPEARS TOO HIGH AND DOES NOT SEEM TO BE TAKING INTO ACCOUNT FINAL SNOWFALL AMOUNTS. WARMER AIR WILL HAVE THE BEST CHANCE OF MAKING IT INTO AREAS SOUTH OF I-72 MONDAY... FARTHER NORTH... KEPT MAX TEMPS CLOSER TO NAM 2 METER TEMPS... WITH MOST AREAS ALONG THE I-74 CORRIDOR STAYING BELOW FREEZING. OTHERWISE... A SLOW WARM UP LOOKS TO CONTINUE THROUGH TUESDAY. DRY ATMOSPHERE SHOULD HOPEFULLY KEEP FOG THREAT AT BAY DESPITE WARM ADVECTION... BUT WE COULD SEE SOME DIURNAL STRATOCU DECKS DEVELOP ACROSS NORTHERN SECTIONS MONDAY NIGHT AND TUESDAY. LONG TERM...WEDNESDAY AND THURSDAY. NEXT DISTURBANCE LOOKS TO AFFECT THE AREA WEDNESDAY NIGHT INTO THURSDAY... MAINLY BRINGING LIGHT RAIN AND SNOW TO THE AREA. COULD SEE A MIXED BAG ALONG THE I-72 CORRIDOR WED NIGHT... BUT QPF AMOUNTS STILL SHOULD BE LOW... THUS DO NOT EXPECT MAJOR PROBLEMS. ACTIVE PATTERN DOES LOOK TO CONTINUE THOUGH... WITH PERHAPS ANOTHER WINTRY SYSTEM AFFECTING THE AREA NEXT WEEKEND. WHY NOT MAKE IT 4 IN A ROW. HARDIMAN && .AVIATION... ISSUED 530 AM CST SUN DEC 16 2007 STRONG STORM SYSTEM IS PULLING AWAY... BUT STILL DEALING WITH MVFR TO IFR CIGS ACROSS THE EAST. PLENTY OF BREAKS OPENING UP ACROSS WESTERN IL AND EASTERN IOWA... BUT MORE LOW CLOUDS CONTINUE TO LOOM OVER MUCH OF IOWA. RUC13 AND LOCAL 20KM ARW HAS A GOOD HANDLE ON CURRENT SITUATION... AND THESE MODELS SUGGEST THAT ANY BREAKS IN THE WEST WILL FILL IN AGAIN TOWARDS MIDDAY AS A WEAK SHORTWAVE CURRENTLY EXTENDING FROM SOUTHERN MINNESOTA TO NORTHWESTERN ONTARIO DROPS ACROSS THE AREA. WITH NORTHWESTERLY FLOW OVER SNOWPACK... I THINK ANY BREAKS IN THE EAST WILL BE RATHER SHORT-LIVED... WITH THE BACK EDGE OF LOW CLOUD COVER LIKELY TO HANG AROUND THIS MORNING AFTER SUNRISE... WITH BMI/DEC PLAYING WITH THE FRINGES MUCH OF THE AFTERNOON. FINALLY... SKIES SHOULD CLEAR OUT AT ALL STATIONS LATE TONIGHT. BUT WITH WEAK SFC WARM ADVECTION KICKING IN... WOULD COULD SEE SOME FOG DEVELOP TOWARDS DAWN MONDAY MORNING. HARDIMAN && .ILX WATCHES/WARNINGS/ADVISORIES... WINTER STORM WARNING UNTIL 8 AM CST THIS MORNING FOR ILZ045-046- 055>057-062-063-066>068-071>073. && $$ il AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NORTHERN INDIANA 1257 PM EST SUN DEC 16 2007 .AVIATION... LAKE EFFECT BAND WILL MOVE OVER KSBN OVER THE NEXT HR OR TWO. TEMPO 1/2SM SN SHOULD BE SUFFICIENT. BLSN STILL A PROBLEM WITH STG WINDS. FWA SEEMS TO BE HAVING MORE BLSN THAN SBN AND WILL THEREFORE HIT TEMPO HARDER THERE FOR 1SM VISBYS. VFR VISBYS SHOULD PREVAIL AFTER 00Z TONIGHT. MVFR CIGS MAY MOVE IN FM THE NW AS FCST SOUNDINGS HINTING THAT WAY AND CURRENT VIS IMAGE SUPPORTIVE WITH LG STRAT DECK OVR MN/WI/IA MOVING SLOWLY SE. ADDED JUST A TEMPO MVFR GP AS INVERSION NOT OVERLY IMPRESSIVE PER FCST SOUNDINGS. THIS WILL NEED TO BE MONITORED IN LATER ISSUANCES FOR POSSIBLE IFR CIGS. WINDS SHOULD BEGIN TO DIE DOWN TONIGHT...LIKELY ENDING FURTHER VISBY REDUCTIONS DUE TO BLSN. && .PREV DISCUSSION... /ISSUED 559 AM EST SUN DEC 16 2007/ SHORT TERM... TODAY AND TONIGHT...A MAJOR WINTER STORM WAS UNDERWAY WITH THE DEFORMATION ZONE MOVING OVER NORTHERN INDIANA. THE MIXED AREA OF PRECIPITATION MOVED AS FAR NORTHWEST FROM ABOUT A LOGANSPORT TO DEFIANCE LINE. THE RUC 0C 850 MB HAS HAD A GOOD HANDLE ON THIS WINTRY MIX...AND ALL PRECIPITATION SHOULD CHANGE BACK TO SNOW BY 12Z. VAN WERT EM REPORTED 1/4 INCH OF ICE...PROBABLY REPRESENTATIVE OF LIMA...PORTLAND AND VAN WERT AREAS. HAVE LOWERED SNOW TOTALS SOME TO BASICALLY 4 TO 7 INCHES IN THE FAR SOUTHEAST DUE TO THIS MIX LASTING LONGER THAN EXPECTED...PORTLAND TO LIMA. THE DEFORMATION ZONE SHOULD BEGIN TO PULL LATE THIS MORNING AND WEAKEN AS THE EAST COAST LOW INTENSIFIES. OTHERWISE... SNOWFALL IS EXPECTED TO RANGE FROM 8 TO 14 INCHES IN CORRIDOR FROM MONTICELLO TO HILLSDALE. TOTAL STORM SNOWFALL AMOUNTS ON EITHER SIDE OF THIS AREA SHOULD BE A LITTLE LESS...6 TO 12 INCHES. OVERALL...FAVOR THE NAM/WRF WHICH APPEARS TO HAVE OVERALL THE BEST HANDLE ON THE LOW CYCLOGENESIS AND TRACK INTO OHIO. ALSO...GOOD RESOLUTION OF THE DEFORMATION ZONE PER NAM/WRF. RAISED WIND SPEEDS PER EXPECTED DEEPER OHIO LOW CYCLOGENESIS. THE WINDY CONDITIONS WILL PERSIST TODAY WITH BLOWING AND DRIFTING SNOW. LIKE NGM/FWC MOS WITH SUSTAINED WINDS MUCH ABOVE 20 KNOTS. CONSIDERED A BLIZZARD WARNING...BUT STILL TOO MUCH UNCERTAINTY ON WIDESPREAD VISIBILITIES AT OR UNDER 1/4 MILE FOR 3 HOURS. LONG TERM... FOCUS TONIGHT IS WITH ONGOING WINTER STORM AND THEREFORE LITTLE CHANGES MADE TO LONG TERM PORTION OF GRIDS. STILL CONCERNS WITH TEMPERATURES BEING TOO WARM GIVEN THE SNOW TONIGHT AND ITS AFFECT ON LOW LEVEL THERMAL PROFILES THROUGH THE WEEK. FEW CHANGES MADE THOUGH AS CURRENT GRIDS GENERALLY BELOW MOS AND REASONABLE. CLIPPER SYSTEM FOR THURSDAY NOW LOOKS A LITTLE FURTHER SOUTH IN LATEST GFS RUN AS WE EXPECTED. ECMWF SIMILAR BUT A LITTLE WARMER WITH THERMAL FIELDS. STILL CANNOT RULE OUT MIXED PRECIPITATION AND FURTHER TRACK ADJUSTMENT EXPECTED...THEREFORE WILL CONTINUE WITH RAIN OR SNOW MENTION. THERE IS A POSSIBILITY OF FREEZING RAIN BUT SMALL CHANCE AT THIS TIME AND DIFFICULT TO PIN DOWN SO WILL NOT INTRODUCE. DOES NOT LOOK TO BE A SIGNIFICANT QPF EVENT LIKE PAST 3 SYSTEMS. WILL CONTINUE TO MONITOR. PREV DISCUSSION... /ISSUED 102 AM EST SUN DEC 16 2007/ AVIATION... FWA WAS ON THE EDGE OF A WARMER LAYER ALOFT...WITH A MIX BEING REPORTED. SURFACE REPORTS PLUS LATEST RUC INDICATES PRECIPITATION SHOULD BECOME ALL SNOW LATER TONIGHT. A LARGE DEFORMATION ZONE SHOULD SET UP OVER NORTHERN INDIANA. EXPECT WINDS TO INCREASE AND BACK TO THE NORTH AND EVENTUALLY THE NORTHWEST. LIFR CONDITIONS ARE EXPECTED FOR SEVERAL HOURS WITH SNOW AND BLOWING SNOW. THERE SHOULD BE SOME IMPROVEMENT LATE IN THE TAF PERIOD AS THE LOW BEGINS TO MOVE AWAY FROM THE AREA. PREV DISCUSSION... /ISSUED 1007 PM EST SAT DEC 15 2007/ MESOSCALE ANALYSIS/EVENING UPDATE... MAIN CONCERN WITH FORECAST IS THE WAA THAT HAS INVADED THE FAR SE PORTIONS OF THE FORECAST AREA. THE 0 C LINE AT H850 APPEARS TO LIE FROM BETWEEN DEFIANCE AND LIMA TO NEAR FORT WAYNE AND THEN ON TO AROUND KOKOMO OR FRANKFORT. SOME DECENT BRIGHT-BANDING SEEN ON THE CURRENT RADAR LOOP NEARLY STATIONARY AROUND THE ABOVE MENTIONED AREA...TELLING SIGN THAT WE ARE NEAR THE 0C LINE MOST LIKELY! SEEMS AS IF THE LOW ITSELF HAS SLOWED AS WOULD BE EXPECTED AS IT CONTINUES TO DEEPEN TONIGHT...THIS HAS ALSO SLOWED THE EASTWARD TRANSIT OF THE 0C LINE AS ALSO MENTIONED ABOVE. THE WAA WILL PUSH A BIT FURTHER NORTH INTO NW OHIO FROM 03-06Z BEFORE STARTING TO PUSH EAST AS THE H850 LOW MOVES INTO EXTREME EASTERN INDIANA BY 07-09Z. IT MAY PIVOT TO BECOME SLIGHTLY MORE NORTH TO SOUTH DURING THE NEXT HOUR OR TWO BEFORE STARTING THIS SLOW TRANSIT EAST. THEREFORE THOUGH FORT WAYNE IS EXPERIENCING A MIX RIGHT NOW...DO NOT THINK THAT IT WILL LAST ENOUGH TO LIMIT THE SNOW TOTALS AS MUCH AS FURTHER EAST AND SOUTHEAST TOWARDS LIMA/VAN WERT AREAS AND SOUTH TOWARDS THE MARION TO PORTLAND INDIANA AREA. MODERATE TO HEAVY SNOW AT TIMES WILL BE LIKELY THRU THE OVERNIGHT...AND AFTER 06-08Z IN OUR FAR EASTERN/SOUTHEASTERN COUNTIES. OVERALL NEW MODEL DATA SHOWS NO REASON TO ADJUST ANYTHING ANYWHERE ELSE...COMMENTS FROM PREVIOUS UPDATE STILL VALID AS NEW DATA CONTINUES TO SHOW THAT PLENTY OF MOISTURE IS AVAILABLE AND THE DYNAMICS AND FORCING IS VERY STRONG. UPDATE ZONES AND WARNING OUT SHORTLY. PREV DISCUSSION... /ISSUED 750 PM EST SAT DEC 15 2007/ MESOSCALE ANALYSIS/UPDATE... CURRENT RADAR TRENDS SHOW INCREASING RETURNS WITH BANDS OF HEAVY SNOW ACROSS THE CENTRAL AND WESTERN PORTIONS OF THE FORECAST AREA...OVER THE EAST LIGHTER MIXED PRECIP WITH SLEET AND FRZ RAIN...FRZ RAIN MORE SO ACROSS THE VAN WERT AND LIMA OHIO AREAS. IMPORTANT FEATURE RIGHT NOW IS THE H850 LOW SITUATED NEAR SOUTHERN IL...WITH WAA WORKING INTO THE EASTERN HALF OF THE FORECAST AREA. 0C LINE NEAR LIMA OHIO TO NEAR GRISSOM AFB TO NEAR CRAWFORDSVILLE INDIANA. STRONG H850-700MB FRONTGENETICAL FORCING SEEN OVER NORTHERN IL INTO LOWER MI. HEAVY BANDED SNOW ACROSS NORTHERN ILLINOIS AT THIS TIME AND FURTHER SOUTH INTO MISSOURI. OVER THE NEXT 8 HOURS THE H850 LOW WILL TRAVEL TO NEAR MUNCIE INDIANA...AND THE 0 C LINE THAT WILL HAVE BEEN NEARLY STATIONARY AROUND OR JUST SOUTH OF LIMA OHIO AND MARION INDIANA WILL SHIFT EAST OF THE AREA ALLOWING FOR ALL SNOW BY 09Z FOR THE WHOLE FORECAST AREA. STRONGEST H850-700MB LAYER FRONTOGENETICAL FORCING ACROSS THE REGION WILL BE FROM 03 TO 12Z ACROSS THE REGION...ALONG WITH DECENT NORTHERLY AGEO WINDS AT 300MB HELPING TO PULL MASS FROM THE COLUMN AND ENHANCE LIFT...SLANTWISE INSTABILITY AND NEG EPV WHICH WILL HELP ADD A CONVECTIVE ELEMENT AND MAY ALLOW FOR VERY QUICK ACCUMULATING SNOWS OF 1-3" PER HOUR UNDER THESE BANDS. THEREFORE SOME LIGHTNING AND THUNDER TONIGHT MAY NOT BE OUT OF THE QUESTION ACROSS THE AREA...THUNDERSNOW IS A VERY INTERESTING RARE EVENT. CURRENT RUC THEN SHOWS THE STRONG H700-500MB LAYER FRONTOGENETICAL FORCING MOVING THRU FROM 09Z-18Z SUNDAY ALLOWING FOR CONTINUED MODERATE TO HEAVY SNOW POSSIBLE. PREV DISCUSSION... /ISSUED 519 PM EST SAT DEC 15 2007/ SHORT TERM... TONIGHT THROUGH SUNDAY NEAR BLIZZARD CONDITIONS SUNDAY ENTIRE CWA. FOCUS ON MINOR TWEAKS WITH RESPECT TO SNOW ACCUMS AND ICE ACCRETION FAR SERN CWA THIS FORECAST CYCLE. NAM CONTINUES WELL WRAPPED/WARM SOLUTION THOUGH APPEARED TO FAIL TO PROPERLY CAPTURE PLACEMENT OF 8H LOW...TOO FAR WEST...WHICH MAY PLAY ROLE IN SLOWER/DEEPER/WARMER EVOLUTION OF ELEVATED WARM LAYER AHEAD OF DEEPENING SURFACE LOW TRACK. 20 UTC 1005MB SFC LOW NEAR KMEM WITH STRONG NNE-SSW ELONGATED 3HR PRESSURE FALLS GT 6MB/3HRS FM FAR WRN KY TO KLAF. SECONDARY PRESSURE FALL CENTER NEAR KHTS TO LIKELY BECOME DOMINANT NEXT SEVERAL HOURS AND LESS FAVOR SUCH EXTREME NWRN SURGE OF IP/ZR AS NAM WOULD INDICATE. ALSO COASTAL ENERGY TRANSFER START NOW UNDERWAY WITH INVERTED SURFACE TROFFING EVIDENT FROM AL TO OFF COAST OF CAROLINAS. FAVORING GFS/SREF SOLUTION OVERALL WITH LARGELY SNOW EVENT NWRN HALF. MIX OF SNOW/SLEET PRIMARILY TONIGHT AS WARM CONVEYOR PER KILN VWP AND SREF POINT SOUNDINGS AND 2-3KFT ABOVE 0C LAYER PER KAOH BUFKIT WET BULB PROFILE. NAM OF COURSE MUCH WARMER AND EVEN SUGGESTIVE OF CHANGEOVER TO RAIN AS NEARBY AS KFDY AND ZR TO KFWA...WILL STEER CLEAR FOR NOW. TOTALS LOWERED ONLY IN IP/ZR AREA BUT WITH SIGNIFICANT MOISTURE...GFS WITH 3.5-4 G/KG TAP 1000-850MB LAYER 07-13 UTC TIMEFRAME...SUN THIS WILL LIKELY BE AT HEIGHT OF MOST SIGNIFICANT SNOWFALL RATES ACROSS NWRN HALF CWA. CONVECTIVE ELEMENTS OBSERVED IN KLSX RADAR AND WITH TIMING AND STRENGTH OF MID LEVEL DEFORMATION HAVE ADDED SLIGHT CHANCE THUNDER IN AFTER MIDNIGHT IN HEAVY SNOW WITH SNOWFALL RATES 2-3 INCHES/HOUR ARE WHERE CHARGE SEPARATION MORE LIKELY THAN IN MIXED PRECIP AREA OF SERN ZONES. QUICK CHANGE OVER IN ERN/SERN ZONES TO ALL SNOW BEFORE DAYBREAK SUNDAY AS COASTAL LOW BECOMES DOMINANT AND COLUMN COOLS SIGNIFICANTLY. WINDS A GRAVE CONCERN ESPECIALLY TO E-W RUNNING ROADS 6/30/24/TOLL ROAD/TO IMPASSABLE COUNTY ROADS DRIFTED SHUT. MENTION OF NEAR BLIZZARD CONDITIONS IN BLOWING/DRIFTING SNOW ALL BUT FAR SERN ZONES TONIGHT AND ENTIRE CWA BY SUNDAY WITH SERN ZONES PICKING UP ONE-HALF TO NEAR ONE FOOT OF SNOW WITH OVER 1-2 INCH/HOUR RATES OF DRY ENOUGH SNOW TO BLOW/DRIFT ON TOP OF FEW TENTHS CONGLOMERATION OF ZR/IP WITH NRLY WINDS TO 35 MPH. BAND OF HEAVIEST TOTAL SNOWS WHITE CO NE TO MARSHALL TO ELKHART TO BRANCH/HILLSDALE MI COUNTIES TO AROUND 15 INCHES. LONG TERM... LONG TERM PERIOD WILL CONTINUE TO FEATURE AN ACTIVE FLOW REGIME WITH NUMEROUS MID LEVEL IMPULSES TAKING AIM AT THE REGION. WATER VAPOR SATELLITE OVER THE PACIFIC OCEAN VERIFIES NUMEROUS POTENT TROUGHS THAT WILL QUICKLY SHIFT EAST TOWARD THE REGION. MID-LEVEL FLOW CHANGE TO MORE ZONAL WEST-EAST FLOW WILL SUPPORT A SLIGHT WARMER CONDITIONS BY TUESDAY...BRINGING TEMPS CLOSER TO OR JUST SLIGHTLY ABOVE NORMAL FOR THE REGION...AS THE MAIN NORTHERN STREAM STORM TRACK SHIFTS INTO THE NORTHERN TIER. MODELS AND ENSEMBLES ARE IN PRETTY GOOD AGREEMENT THROUGH THE MAJORITY OF THE PERIOD SAVE THE WEEKEND...AND HAVE TRENDED FORECAST TO THE 12Z GFS AND 12Z AND 00Z ECMWF. LOOK FOR A SLOW RECOVERY IN TEMPS THROUGH MID WEEK WITH EXPECTED SNOW COVER IN PLACE. CONTINUED TO OPT FOR COOL BELOW GUIDANCE TEMPS...IN LINE WITH PREVIOUS FORECAST. RETAINED POP CHANCES THUR AND FRI. WEAK SOUTHERN STREAM WAVE WILL SUPPORT THE DEVELOPMENT OF WEAK LOW PRESSURE OVER THE LOWER MISSISSIPPI VALLEY. WARMER THERMAL PROFILES ARE STILL SUPPORTING RAIN. HOWEVER...WILL RETAIN SNOW MENTION DUE TO POSSIBLE COOLER MODEL SOLUTIONS ONCE NEW SNOW FIELD IS ASSIMILATED...AS PER PREVIOUS FORECAST. SATURDAY...ANOTHER LARGE STORM SYSTEM MAY BE POSSIBLE NEXT WEEKEND...AS A DEEPER MID LEVEL TROUGH DIGS OVER THE WESTERN US...EVENTUALLY EJECTING OUT INTO THE THE SOUTHERN PLAINS. LATEST RUN OF THE ECMWF NO LONGER FAVORS PHASING OF THE NORTHERN AND SOUTHERN STREAMS...AND OPTS FOR A SLOWER/WEAKER SYSTEM OVER THE GULF COAST. THE GFS WITH SOME SUPPORT OF PREVIOUS ENSEMBLE RUNS DO FAVOR PHASING WITH THE DEVELOPMENT OF A MORE INTENSE SFC LOW. THIS WOULD POSSIBLY SPELL MORE ACCUMULATING SNOW FOR THE REGION. HOWEVER...WITH SUCH A LARGE ENSEMBLE SPREAD/CURRENT POOR SAMPLING ISSUES NOTED OVER THE PACIFIC/AND LARGE DETERMINISTIC SOLUTION SPREADS...HAVE OPTED DRY FOR NOW. THIS PERIOD WILL NEED TO BE MONITORED. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...WINTER STORM WARNING UNTIL 7 PM EST /6 PM CST/ THIS EVENING FOR INZ003>009-012>018-020-022>027-032>034. MI...WINTER STORM WARNING UNTIL 7 PM EST THIS EVENING FOR MIZ077>081. OH...WINTER STORM WARNING UNTIL 7 PM EST THIS EVENING FOR OHZ001-002- 004-005-015-016-024-025. LM...GALE WARNING UNTIL 7 PM EST THIS EVENING FOR LMZ043-046. && $$ SHORT TERM...SKIPPER LONG TERM...LASHLEY AVIATION...SIMPSON in AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NORTHERN INDIANA 559 AM EST SUN DEC 16 2007 .SHORT TERM... TODAY AND TONIGHT...A MAJOR WINTER STORM WAS UNDERWAY WITH THE DEFORMATION ZONE MOVING OVER NORTHERN INDIANA. THE MIXED AREA OF PRECIPITATION MOVED AS FAR NORTHWEST FROM ABOUT A LOGANSPORT TO DEFIANCE LINE. THE RUC 0C 850 MB HAS HAD A GOOD HANDLE ON THIS WINTRY MIX...AND ALL PRECIPITATION SHOULD CHANGE BACK TO SNOW BY 12Z. VAN WERT EM REPORTED 1/4 INCH OF ICE...PROBABLY REPRESENTATIVE OF LIMA...PORTLAND AND VAN WERT AREAS. HAVE LOWERED SNOW TOTALS SOME TO BASICALLY 4 TO 7 INCHES IN THE FAR SOUTHEAST DUE TO THIS MIX LASTING LONGER THAN EXPECTED...PORTLAND TO LIMA. THE DEFORMATION ZONE SHOULD BEGIN TO PULL LATE THIS MORNING AND WEAKEN AS THE EAST COAST LOW INTENSIFIES. OTHERWISE... SNOWFALL IS EXPECTED TO RANGE FROM 8 TO 14 INCHES IN CORRIDOR FROM MONTICELLO TO HILLSDALE. TOTAL STORM SNOWFALL AMOUNTS ON EITHER SIDE OF THIS AREA SHOULD BE A LITTLE LESS...6 TO 12 INCHES. OVERALL...FAVOR THE NAM/WRF WHICH APPEARS TO HAVE OVERALL THE BEST HANDLE ON THE LOW CYCLOGENESIS AND TRACK INTO OHIO. ALSO...GOOD RESOLUTION OF THE DEFORMATION ZONE PER NAM/WRF. RAISED WIND SPEEDS PER EXPECTED DEEPER OHIO LOW CYCLOGENESIS. THE WINDY CONDITIONS WILL PERSIST TODAY WITH BLOWING AND DRIFTING SNOW. LIKE NGM/FWC MOS WITH SUSTAINED WINDS MUCH ABOVE 20 KNOTS. CONSIDERED A BLIZZARD WARNING...BUT STILL TOO MUCH UNCERTAINTY ON WIDESPREAD VISIBILITIES AT OR UNDER 1/4 MILE FOR 3 HOURS. && .LONG TERM... FOCUS TONIGHT IS WITH ONGOING WINTER STORM AND THEREFORE LITTLE CHANGES MADE TO LONG TERM PORTION OF GRIDS. STILL CONCERNS WITH TEMPERATURES BEING TOO WARM GIVEN THE SNOW TONIGHT AND ITS AFFECT ON LOW LEVEL THERMAL PROFILES THROUGH THE WEEK. FEW CHANGES MADE THOUGH AS CURRENT GRIDS GENERALLY BELOW MOS AND REASONABLE. CLIPPER SYSTEM FOR THURSDAY NOW LOOKS A LITTLE FURTHER SOUTH IN LATEST GFS RUN AS WE EXPECTED. ECMWF SIMILAR BUT A LITTLE WARMER WITH THERMAL FIELDS. STILL CANNOT RULE OUT MIXED PRECIPITATION AND FURTHER TRACK ADJUSTMENT EXPECTED...THEREFORE WILL CONTINUE WITH RAIN OR SNOW MENTION. THERE IS A POSSIBILITY OF FREEZING RAIN BUT SMALL CHANCE AT THIS TIME AND DIFFICULT TO PIN DOWN SO WILL NOT INTRODUCE. DOES NOT LOOK TO BE A SIGNIFICANT QPF EVENT LIKE PAST 3 SYSTEMS. WILL CONTINUE TO MONITOR. && .PREV DISCUSSION... /ISSUED 102 AM EST SUN DEC 16 2007/ AVIATION... FWA WAS ON THE EDGE OF A WARMER LAYER ALOFT...WITH A MIX BEING REPORTED. SURFACE REPORTS PLUS LATEST RUC INDICATES PRECIPITATION SHOULD BECOME ALL SNOW LATER TONIGHT. A LARGE DEFORMATION ZONE SHOULD SET UP OVER NORTHERN INDIANA. EXPECT WINDS TO INCREASE AND BACK TO THE NORTH AND EVENTUALLY THE NORTHWEST. LIFR CONDITIONS ARE EXPECTED FOR SEVERAL HOURS WITH SNOW AND BLOWING SNOW. THERE SHOULD BE SOME IMPROVEMENT LATE IN THE TAF PERIOD AS THE LOW BEGINS TO MOVE AWAY FROM THE AREA. PREV DISCUSSION... /ISSUED 1007 PM EST SAT DEC 15 2007/ MESOSCALE ANALYSIS/EVENING UPDATE... MAIN CONCERN WITH FORECAST IS THE WAA THAT HAS INVADED THE FAR SE PORTIONS OF THE FORECAST AREA. THE 0 C LINE AT H850 APPEARS TO LIE FROM BETWEEN DEFIANCE AND LIMA TO NEAR FORT WAYNE AND THEN ON TO AROUND KOKOMO OR FRANKFORT. SOME DECENT BRIGHT-BANDING SEEN ON THE CURRENT RADAR LOOP NEARLY STATIONARY AROUND THE ABOVE MENTIONED AREA...TELLING SIGN THAT WE ARE NEAR THE 0C LINE MOST LIKELY! SEEMS AS IF THE LOW ITSELF HAS SLOWED AS WOULD BE EXPECTED AS IT CONTINUES TO DEEPEN TONIGHT...THIS HAS ALSO SLOWED THE EASTWARD TRANSIT OF THE 0C LINE AS ALSO MENTIONED ABOVE. THE WAA WILL PUSH A BIT FURTHER NORTH INTO NW OHIO FROM 03-06Z BEFORE STARTING TO PUSH EAST AS THE H850 LOW MOVES INTO EXTREME EASTERN INDIANA BY 07-09Z. IT MAY PIVOT TO BECOME SLIGHTLY MORE NORTH TO SOUTH DURING THE NEXT HOUR OR TWO BEFORE STARTING THIS SLOW TRANSIT EAST. THEREFORE THOUGH FORT WAYNE IS EXPERIENCING A MIX RIGHT NOW...DO NOT THINK THAT IT WILL LAST ENOUGH TO LIMIT THE SNOW TOTALS AS MUCH AS FURTHER EAST AND SOUTHEAST TOWARDS LIMA/VAN WERT AREAS AND SOUTH TOWARDS THE MARION TO PORTLAND INDIANA AREA. MODERATE TO HEAVY SNOW AT TIMES WILL BE LIKELY THRU THE OVERNIGHT...AND AFTER 06-08Z IN OUR FAR EASTERN/SOUTHEASTERN COUNTIES. OVERALL NEW MODEL DATA SHOWS NO REASON TO ADJUST ANYTHING ANYWHERE ELSE...COMMENTS FROM PREVIOUS UPDATE STILL VALID AS NEW DATA CONTINUES TO SHOW THAT PLENTY OF MOISTURE IS AVAILABLE AND THE DYNAMICS AND FORCING IS VERY STRONG. UPDATE ZONES AND WARNING OUT SHORTLY. PREV DISCUSSION... /ISSUED 750 PM EST SAT DEC 15 2007/ MESOSCALE ANALYSIS/UPDATE... CURRENT RADAR TRENDS SHOW INCREASING RETURNS WITH BANDS OF HEAVY SNOW ACROSS THE CENTRAL AND WESTERN PORTIONS OF THE FORECAST AREA...OVER THE EAST LIGHTER MIXED PRECIP WITH SLEET AND FRZ RAIN...FRZ RAIN MORE SO ACROSS THE VAN WERT AND LIMA OHIO AREAS. IMPORTANT FEATURE RIGHT NOW IS THE H850 LOW SITUATED NEAR SOUTHERN IL...WITH WAA WORKING INTO THE EASTERN HALF OF THE FORECAST AREA. 0C LINE NEAR LIMA OHIO TO NEAR GRISSOM AFB TO NEAR CRAWFORDSVILLE INDIANA. STRONG H850-700MB FRONTGENETICAL FORCING SEEN OVER NORTHERN IL INTO LOWER MI. HEAVY BANDED SNOW ACROSS NORTHERN ILLINOIS AT THIS TIME AND FURTHER SOUTH INTO MISSOURI. OVER THE NEXT 8 HOURS THE H850 LOW WILL TRAVEL TO NEAR MUNCIE INDIANA...AND THE 0 C LINE THAT WILL HAVE BEEN NEARLY STATIONARY AROUND OR JUST SOUTH OF LIMA OHIO AND MARION INDIANA WILL SHIFT EAST OF THE AREA ALLOWING FOR ALL SNOW BY 09Z FOR THE WHOLE FORECAST AREA. STRONGEST H850-700MB LAYER FRONTOGENETICAL FORCING ACROSS THE REGION WILL BE FROM 03 TO 12Z ACROSS THE REGION...ALONG WITH DECENT NORTHERLY AGEO WINDS AT 300MB HELPING TO PULL MASS FROM THE COLUMN AND ENHANCE LIFT...SLANTWISE INSTABILITY AND NEG EPV WHICH WILL HELP ADD A CONVECTIVE ELEMENT AND MAY ALLOW FOR VERY QUICK ACCUMULATING SNOWS OF 1-3" PER HOUR UNDER THESE BANDS. THEREFORE SOME LIGHTNING AND THUNDER TONIGHT MAY NOT BE OUT OF THE QUESTION ACROSS THE AREA...THUNDERSNOW IS A VERY INTERESTING RARE EVENT. CURRENT RUC THEN SHOWS THE STRONG H700-500MB LAYER FRONTOGENETICAL FORCING MOVING THRU FROM 09Z-18Z SUNDAY ALLOWING FOR CONTINUED MODERATE TO HEAVY SNOW POSSIBLE. PREV DISCUSSION... /ISSUED 519 PM EST SAT DEC 15 2007/ SHORT TERM... TONIGHT THROUGH SUNDAY NEAR BLIZZARD CONDITIONS SUNDAY ENTIRE CWA. FOCUS ON MINOR TWEAKS WITH RESPECT TO SNOW ACCUMS AND ICE ACCRETION FAR SERN CWA THIS FORECAST CYCLE. NAM CONTINUES WELL WRAPPED/WARM SOLUTION THOUGH APPEARED TO FAIL TO PROPERLY CAPTURE PLACEMENT OF 8H LOW...TOO FAR WEST...WHICH MAY PLAY ROLE IN SLOWER/DEEPER/WARMER EVOLUTION OF ELEVATED WARM LAYER AHEAD OF DEEPENING SURFACE LOW TRACK. 20 UTC 1005MB SFC LOW NEAR KMEM WITH STRONG NNE-SSW ELONGATED 3HR PRESSURE FALLS GT 6MB/3HRS FM FAR WRN KY TO KLAF. SECONDARY PRESSURE FALL CENTER NEAR KHTS TO LIKELY BECOME DOMINANT NEXT SEVERAL HOURS AND LESS FAVOR SUCH EXTREME NWRN SURGE OF IP/ZR AS NAM WOULD INDICATE. ALSO COASTAL ENERGY TRANSFER START NOW UNDERWAY WITH INVERTED SURFACE TROFFING EVIDENT FROM AL TO OFF COAST OF CAROLINAS. FAVORING GFS/SREF SOLUTION OVERALL WITH LARGELY SNOW EVENT NWRN HALF. MIX OF SNOW/SLEET PRIMARILY TONIGHT AS WARM CONVEYOR PER KILN VWP AND SREF POINT SOUNDINGS AND 2-3KFT ABOVE 0C LAYER PER KAOH BUFKIT WET BULB PROFILE. NAM OF COURSE MUCH WARMER AND EVEN SUGGESTIVE OF CHANGEOVER TO RAIN AS NEARBY AS KFDY AND ZR TO KFWA...WILL STEER CLEAR FOR NOW. TOTALS LOWERED ONLY IN IP/ZR AREA BUT WITH SIGNIFICANT MOISTURE...GFS WITH 3.5-4 G/KG TAP 1000-850MB LAYER 07-13 UTC TIMEFRAME...SUN THIS WILL LIKELY BE AT HEIGHT OF MOST SIGNIFICANT SNOWFALL RATES ACROSS NWRN HALF CWA. CONVECTIVE ELEMENTS OBSERVED IN KLSX RADAR AND WITH TIMING AND STRENGTH OF MID LEVEL DEFORMATION HAVE ADDED SLIGHT CHANCE THUNDER IN AFTER MIDNIGHT IN HEAVY SNOW WITH SNOWFALL RATES 2-3 INCHES/HOUR ARE WHERE CHARGE SEPARATION MORE LIKELY THAN IN MIXED PRECIP AREA OF SERN ZONES. QUICK CHANGE OVER IN ERN/SERN ZONES TO ALL SNOW BEFORE DAYBREAK SUNDAY AS COASTAL LOW BECOMES DOMINANT AND COLUMN COOLS SIGNIFICANTLY. WINDS A GRAVE CONCERN ESPECIALLY TO E-W RUNNING ROADS 6/30/24/TOLL ROAD/TO IMPASSABLE COUNTY ROADS DRIFTED SHUT. MENTION OF NEAR BLIZZARD CONDITIONS IN BLOWING/DRIFTING SNOW ALL BUT FAR SERN ZONES TONIGHT AND ENTIRE CWA BY SUNDAY WITH SERN ZONES PICKING UP ONE-HALF TO NEAR ONE FOOT OF SNOW WITH OVER 1-2 INCH/HOUR RATES OF DRY ENOUGH SNOW TO BLOW/DRIFT ON TOP OF FEW TENTHS CONGLOMERATION OF ZR/IP WITH NRLY WINDS TO 35 MPH. BAND OF HEAVIEST TOTAL SNOWS WHITE CO NE TO MARSHALL TO ELKHART TO BRANCH/HILLSDALE MI COUNTIES TO AROUND 15 INCHES. LONG TERM... LONG TERM PERIOD WILL CONTINUE TO FEATURE AN ACTIVE FLOW REGIME WITH NUMEROUS MID LEVEL IMPULSES TAKING AIM AT THE REGION. WATER VAPOR SATELLITE OVER THE PACIFIC OCEAN VERIFIES NUMEROUS POTENT TROUGHS THAT WILL QUICKLY SHIFT EAST TOWARD THE REGION. MID-LEVEL FLOW CHANGE TO MORE ZONAL WEST-EAST FLOW WILL SUPPORT A SLIGHT WARMER CONDITIONS BY TUESDAY...BRINGING TEMPS CLOSER TO OR JUST SLIGHTLY ABOVE NORMAL FOR THE REGION...AS THE MAIN NORTHERN STREAM STORM TRACK SHIFTS INTO THE NORTHERN TIER. MODELS AND ENSEMBLES ARE IN PRETTY GOOD AGREEMENT THROUGH THE MAJORITY OF THE PERIOD SAVE THE WEEKEND...AND HAVE TRENDED FORECAST TO THE 12Z GFS AND 12Z AND 00Z ECMWF. LOOK FOR A SLOW RECOVERY IN TEMPS THROUGH MID WEEK WITH EXPECTED SNOW COVER IN PLACE. CONTINUED TO OPT FOR COOL BELOW GUIDANCE TEMPS...IN LINE WITH PREVIOUS FORECAST. RETAINED POP CHANCES THUR AND FRI. WEAK SOUTHERN STREAM WAVE WILL SUPPORT THE DEVELOPMENT OF WEAK LOW PRESSURE OVER THE LOWER MISSISSIPPI VALLEY. WARMER THERMAL PROFILES ARE STILL SUPPORTING RAIN. HOWEVER...WILL RETAIN SNOW MENTION DUE TO POSSIBLE COOLER MODEL SOLUTIONS ONCE NEW SNOW FIELD IS ASSIMILATED...AS PER PREVIOUS FORECAST. SATURDAY...ANOTHER LARGE STORM SYSTEM MAY BE POSSIBLE NEXT WEEKEND...AS A DEEPER MID LEVEL TROUGH DIGS OVER THE WESTERN US...EVENTUALLY EJECTING OUT INTO THE THE SOUTHERN PLAINS. LATEST RUN OF THE ECMWF NO LONGER FAVORS PHASING OF THE NORTHERN AND SOUTHERN STREAMS...AND OPTS FOR A SLOWER/WEAKER SYSTEM OVER THE GULF COAST. THE GFS WITH SOME SUPPORT OF PREVIOUS ENSEMBLE RUNS DO FAVOR PHASING WITH THE DEVELOPMENT OF A MORE INTENSE SFC LOW. THIS WOULD POSSIBLY SPELL MORE ACCUMULATING SNOW FOR THE REGION. HOWEVER...WITH SUCH A LARGE ENSEMBLE SPREAD/CURRENT POOR SAMPLING ISSUES NOTED OVER THE PACIFIC/AND LARGE DETERMINISTIC SOLUTION SPREADS...HAVE OPTED DRY FOR NOW. THIS PERIOD WILL NEED TO BE MONITORED. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...WINTER STORM WARNING UNTIL 7 PM EST /6 PM CST/ THIS EVENING FOR INZ003>009-012>018-020-022>027-032>034. MI...WINTER STORM WARNING UNTIL 7 PM EST THIS EVENING FOR MIZ077>081. OH...WINTER STORM WARNING UNTIL 7 PM EST THIS EVENING FOR OHZ001-002- 004-005-015-016-024-025. LM...GALE WARNING UNTIL 7 PM EST THIS EVENING FOR LMZ043-046. && $$ SHORT TERM...SKIPPER LONG TERM...LASHLEY AVIATION...SKIPPER in AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NORTHERN INDIANA 102 AM EST SUN DEC 16 2007 .AVIATION... FWA WAS ON THE EDGE OF A WARMER LAYER ALOFT...WITH A MIX BEING REPORTED. SURFACE REPORTS PLUS LATEST RUC INDICATES PRECIPITATION SHOULD BECOME ALL SNOW LATER TONIGHT. A LARGE DEFORMATION ZONE SHOULD SET UP OVER NORTHERN INDIANA. EXPECT WINDS TO INCREASE AND BACK TO THE NORTH AND EVENTUALLY THE NORTHWEST. LIFR CONDITIONS ARE EXPECTED FOR SEVERAL HOURS WITH SNOW AND BLOWING SNOW. THERE SHOULD BE SOME IMPROVEMENT LATE IN THE TAF PERIOD AS THE LOW BEGINS TO MOVE AWAY FROM THE AREA. && .PREV DISCUSSION... /ISSUED 1007 PM EST SAT DEC 15 2007/ MESOSCALE ANALYSIS/EVENING UPDATE... MAIN CONCERN WITH FORECAST IS THE WAA THAT HAS INVADED THE FAR SE PORTIONS OF THE FORECAST AREA. THE 0 C LINE AT H850 APPEARS TO LIE FROM BETWEEN DEFIANCE AND LIMA TO NEAR FORT WAYNE AND THEN ON TO AROUND KOKOMO OR FRANKFORT. SOME DECENT BRIGHT-BANDING SEEN ON THE CURRENT RADAR LOOP NEARLY STATIONARY AROUND THE ABOVE MENTIONED AREA...TELLING SIGN THAT WE ARE NEAR THE 0C LINE MOST LIKELY! SEEMS AS IF THE LOW ITSELF HAS SLOWED AS WOULD BE EXPECTED AS IT CONTINUES TO DEEPEN TONIGHT...THIS HAS ALSO SLOWED THE EASTWARD TRANSIT OF THE 0C LINE AS ALSO MENTIONED ABOVE. THE WAA WILL PUSH A BIT FURTHER NORTH INTO NW OHIO FROM 03-06Z BEFORE STARTING TO PUSH EAST AS THE H850 LOW MOVES INTO EXTREME EASTERN INDIANA BY 07-09Z. IT MAY PIVOT TO BECOME SLIGHTLY MORE NORTH TO SOUTH DURING THE NEXT HOUR OR TWO BEFORE STARTING THIS SLOW TRANSIT EAST. THEREFORE THOUGH FORT WAYNE IS EXPERIENCING A MIX RIGHT NOW...DO NOT THINK THAT IT WILL LAST ENOUGH TO LIMIT THE SNOW TOTALS AS MUCH AS FURTHER EAST AND SOUTHEAST TOWARDS LIMA/VAN WERT AREAS AND SOUTH TOWARDS THE MARION TO PORTLAND INDIANA AREA. MODERATE TO HEAVY SNOW AT TIMES WILL BE LIKELY THRU THE OVERNIGHT...AND AFTER 06-08Z IN OUR FAR EASTERN/SOUTHEASTERN COUNTIES. OVERALL NEW MODEL DATA SHOWS NO REASON TO ADJUST ANYTHING ANYWHERE ELSE...COMMENTS FROM PREVIOUS UPDATE STILL VALID AS NEW DATA CONTINUES TO SHOW THAT PLENTY OF MOISTURE IS AVAILABLE AND THE DYNAMICS AND FORCING IS VERY STRONG. UPDATE ZONES AND WARNING OUT SHORTLY. PREV DISCUSSION... /ISSUED 750 PM EST SAT DEC 15 2007/ MESOSCALE ANALYSIS/UPDATE... CURRENT RADAR TRENDS SHOW INCREASING RETURNS WITH BANDS OF HEAVY SNOW ACROSS THE CENTRAL AND WESTERN PORTIONS OF THE FORECAST AREA...OVER THE EAST LIGHTER MIXED PRECIP WITH SLEET AND FRZ RAIN...FRZ RAIN MORE SO ACROSS THE VAN WERT AND LIMA OHIO AREAS. IMPORTANT FEATURE RIGHT NOW IS THE H850 LOW SITUATED NEAR SOUTHERN IL...WITH WAA WORKING INTO THE EASTERN HALF OF THE FORECAST AREA. 0C LINE NEAR LIMA OHIO TO NEAR GRISSOM AFB TO NEAR CRAWFORDSVILLE INDIANA. STRONG H850-700MB FRONTGENETICAL FORCING SEEN OVER NORTHERN IL INTO LOWER MI. HEAVY BANDED SNOW ACROSS NORTHERN ILLINOIS AT THIS TIME AND FURTHER SOUTH INTO MISSOURI. OVER THE NEXT 8 HOURS THE H850 LOW WILL TRAVEL TO NEAR MUNCIE INDIANA...AND THE 0 C LINE THAT WILL HAVE BEEN NEARLY STATIONARY AROUND OR JUST SOUTH OF LIMA OHIO AND MARION INDIANA WILL SHIFT EAST OF THE AREA ALLOWING FOR ALL SNOW BY 09Z FOR THE WHOLE FORECAST AREA. STRONGEST H850-700MB LAYER FRONTOGENETICAL FORCING ACROSS THE REGION WILL BE FROM 03 TO 12Z ACROSS THE REGION...ALONG WITH DECENT NORTHERLY AGEO WINDS AT 300MB HELPING TO PULL MASS FROM THE COLUMN AND ENHANCE LIFT...SLANTWISE INSTABILITY AND NEG EPV WHICH WILL HELP ADD A CONVECTIVE ELEMENT AND MAY ALLOW FOR VERY QUICK ACCUMULATING SNOWS OF 1-3" PER HOUR UNDER THESE BANDS. THEREFORE SOME LIGHTNING AND THUNDER TONIGHT MAY NOT BE OUT OF THE QUESTION ACROSS THE AREA...THUNDERSNOW IS A VERY INTERESTING RARE EVENT. CURRENT RUC THEN SHOWS THE STRONG H700-500MB LAYER FRONTOGENETICAL FORCING MOVING THRU FROM 09Z-18Z SUNDAY ALLOWING FOR CONTINUED MODERATE TO HEAVY SNOW POSSIBLE. PREV DISCUSSION... /ISSUED 519 PM EST SAT DEC 15 2007/ SHORT TERM... TONIGHT THROUGH SUNDAY NEAR BLIZZARD CONDITIONS SUNDAY ENTIRE CWA. FOCUS ON MINOR TWEAKS WITH RESPECT TO SNOW ACCUMS AND ICE ACCRETION FAR SERN CWA THIS FORECAST CYCLE. NAM CONTINUES WELL WRAPPED/WARM SOLUTION THOUGH APPEARED TO FAIL TO PROPERLY CAPTURE PLACEMENT OF 8H LOW...TOO FAR WEST...WHICH MAY PLAY ROLE IN SLOWER/DEEPER/WARMER EVOLUTION OF ELEVATED WARM LAYER AHEAD OF DEEPENING SURFACE LOW TRACK. 20 UTC 1005MB SFC LOW NEAR KMEM WITH STRONG NNE-SSW ELONGATED 3HR PRESSURE FALLS GT 6MB/3HRS FM FAR WRN KY TO KLAF. SECONDARY PRESSURE FALL CENTER NEAR KHTS TO LIKELY BECOME DOMINANT NEXT SEVERAL HOURS AND LESS FAVOR SUCH EXTREME NWRN SURGE OF IP/ZR AS NAM WOULD INDICATE. ALSO COASTAL ENERGY TRANSFER START NOW UNDERWAY WITH INVERTED SURFACE TROFFING EVIDENT FROM AL TO OFF COAST OF CAROLINAS. FAVORING GFS/SREF SOLUTION OVERALL WITH LARGELY SNOW EVENT NWRN HALF. MIX OF SNOW/SLEET PRIMARILY TONIGHT AS WARM CONVEYOR PER KILN VWP AND SREF POINT SOUNDINGS AND 2-3KFT ABOVE 0C LAYER PER KAOH BUFKIT WET BULB PROFILE. NAM OF COURSE MUCH WARMER AND EVEN SUGGESTIVE OF CHANGEOVER TO RAIN AS NEARBY AS KFDY AND ZR TO KFWA...WILL STEER CLEAR FOR NOW. TOTALS LOWERED ONLY IN IP/ZR AREA BUT WITH SIGNIFICANT MOISTURE...GFS WITH 3.5-4 G/KG TAP 1000-850MB LAYER 07-13 UTC TIMEFRAME...SUN THIS WILL LIKELY BE AT HEIGHT OF MOST SIGNIFICANT SNOWFALL RATES ACROSS NWRN HALF CWA. CONVECTIVE ELEMENTS OBSERVED IN KLSX RADAR AND WITH TIMING AND STRENGTH OF MID LEVEL DEFORMATION HAVE ADDED SLIGHT CHANCE THUNDER IN AFTER MIDNIGHT IN HEAVY SNOW WITH SNOWFALL RATES 2-3 INCHES/HOUR ARE WHERE CHARGE SEPARATION MORE LIKELY THAN IN MIXED PRECIP AREA OF SERN ZONES. QUICK CHANGE OVER IN ERN/SERN ZONES TO ALL SNOW BEFORE DAYBREAK SUNDAY AS COASTAL LOW BECOMES DOMINANT AND COLUMN COOLS SIGNIFICANTLY. WINDS A GRAVE CONCERN ESPECIALLY TO E-W RUNNING ROADS 6/30/24/TOLL ROAD/TO IMPASSABLE COUNTY ROADS DRIFTED SHUT. MENTION OF NEAR BLIZZARD CONDITIONS IN BLOWING/DRIFTING SNOW ALL BUT FAR SERN ZONES TONIGHT AND ENTIRE CWA BY SUNDAY WITH SERN ZONES PICKING UP ONE-HALF TO NEAR ONE FOOT OF SNOW WITH OVER 1-2 INCH/HOUR RATES OF DRY ENOUGH SNOW TO BLOW/DRIFT ON TOP OF FEW TENTHS CONGLOMERATION OF ZR/IP WITH NRLY WINDS TO 35 MPH. BAND OF HEAVIEST TOTAL SNOWS WHITE CO NE TO MARSHALL TO ELKHART TO BRANCH/HILLSDALE MI COUNTIES TO AROUND 15 INCHES. LONG TERM... LONG TERM PERIOD WILL CONTINUE TO FEATURE AN ACTIVE FLOW REGIME WITH NUMEROUS MID LEVEL IMPULSES TAKING AIM AT THE REGION. WATER VAPOR SATELLITE OVER THE PACIFIC OCEAN VERIFIES NUMEROUS POTENT TROUGHS THAT WILL QUICKLY SHIFT EAST TOWARD THE REGION. MID-LEVEL FLOW CHANGE TO MORE ZONAL WEST-EAST FLOW WILL SUPPORT A SLIGHT WARMER CONDITIONS BY TUESDAY...BRINGING TEMPS CLOSER TO OR JUST SLIGHTLY ABOVE NORMAL FOR THE REGION...AS THE MAIN NORTHERN STREAM STORM TRACK SHIFTS INTO THE NORTHERN TIER. MODELS AND ENSEMBLES ARE IN PRETTY GOOD AGREEMENT THROUGH THE MAJORITY OF THE PERIOD SAVE THE WEEKEND...AND HAVE TRENDED FORECAST TO THE 12Z GFS AND 12Z AND 00Z ECMWF. LOOK FOR A SLOW RECOVERY IN TEMPS THROUGH MID WEEK WITH EXPECTED SNOW COVER IN PLACE. CONTINUED TO OPT FOR COOL BELOW GUIDANCE TEMPS...IN LINE WITH PREVIOUS FORECAST. RETAINED POP CHANCES THUR AND FRI. WEAK SOUTHERN STREAM WAVE WILL SUPPORT THE DEVELOPMENT OF WEAK LOW PRESSURE OVER THE LOWER MISSISSIPPI VALLEY. WARMER THERMAL PROFILES ARE STILL SUPPORTING RAIN. HOWEVER...WILL RETAIN SNOW MENTION DUE TO POSSIBLE COOLER MODEL SOLUTIONS ONCE NEW SNOW FIELD IS ASSIMILATED...AS PER PREVIOUS FORECAST. SATURDAY...ANOTHER LARGE STORM SYSTEM MAY BE POSSIBLE NEXT WEEKEND...AS A DEEPER MID LEVEL TROUGH DIGS OVER THE WESTERN US...EVENTUALLY EJECTING OUT INTO THE THE SOUTHERN PLAINS. LATEST RUN OF THE ECMWF NO LONGER FAVORS PHASING OF THE NORTHERN AND SOUTHERN STREAMS...AND OPTS FOR A SLOWER/WEAKER SYSTEM OVER THE GULF COAST. THE GFS WITH SOME SUPPORT OF PREVIOUS ENSEMBLE RUNS DO FAVOR PHASING WITH THE DEVELOPMENT OF A MORE INTENSE SFC LOW. THIS WOULD POSSIBLY SPELL MORE ACCUMULATING SNOW FOR THE REGION. HOWEVER...WITH SUCH A LARGE ENSEMBLE SPREAD/CURRENT POOR SAMPLING ISSUES NOTED OVER THE PACIFIC/AND LARGE DETERMINISTIC SOLUTION SPREADS...HAVE OPTED DRY FOR NOW. THIS PERIOD WILL NEED TO BE MONITORED. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...WINTER STORM WARNING UNTIL 7 PM EST /6 PM CST/ THIS EVENING FOR INZ003>009-012>018-020-022>027-032>034. MI...WINTER STORM WARNING UNTIL 7 PM EST THIS EVENING FOR MIZ077>081. OH...WINTER STORM WARNING UNTIL 7 PM EST THIS EVENING FOR OHZ001-002- 004-005-015-016-024-025. LM...GALE WARNING UNTIL 7 PM EST THIS EVENING FOR LMZ043-046. && $$ SHORT TERM...MURPHY LONG TERM...CHAMBERLAIN AVIATION...SKIPPER UPDATE...SCHOTT in AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NORTHERN INDIANA 1007 PM EST SAT DEC 15 2007 ...CORRECTED SPELLING ERROR.. .MESOSCALE ANALYSIS/EVENING UPDATE... MAIN CONCERN WITH FORECAST IS THE WAA THAT HAS INVADED THE FAR SE PORTIONS OF THE FORECAST AREA. THE 0 C LINE AT H850 APPEARS TO LIE FROM BETWEEN DEFIANCE AND LIMA TO NEAR FORT WAYNE AND THEN ON TO AROUND KOKOMO OR FRANKFORT. SOME DECENT BRIGHT-BANDING SEEN ON THE CURRENT RADAR LOOP NEARLY STATIONARY AROUND THE ABOVE MENTIONED AREA...TELLING SIGN THAT WE ARE NEAR THE 0C LINE MOST LIKELY! SEEMS AS IF THE LOW ITSELF HAS SLOWED AS WOULD BE EXPECTED AS IT CONTINUES TO DEEPEN TONIGHT...THIS HAS ALSO SLOWED THE EASTWARD TRANSIT OF THE 0C LINE AS ALSO MENTIONED ABOVE. THE WAA WILL PUSH A BIT FURTHER NORTH INTO NW OHIO FROM 03-06Z BEFORE STARTING TO PUSH EAST AS THE H850 LOW MOVES INTO EXTREME EASTERN INDIANA BY 07-09Z. IT MAY PIVOT TO BECOME SLIGHTLY MORE NORTH TO SOUTH DURING THE NEXT HOUR OR TWO BEFORE STARTING THIS SLOW TRANSIT EAST. THEREFORE THOUGH FORT WAYNE IS EXPERIENCING A MIX RIGHT NOW...DO NOT THINK THAT IT WILL LAST ENOUGH TO LIMIT THE SNOW TOTALS AS MUCH AS FURTHER EAST AND SOUTHEAST TOWARDS LIMA/VAN WERT AREAS AND SOUTH TOWARDS THE MARION TO PORTLAND INDIANA AREA. MODERATE TO HEAVY SNOW AT TIMES WILL BE LIKELY THRU THE OVERNIGHT...AND AFTER 06-08Z IN OUR FAR EASTERN/SOUTHEASTERN COUNTIES. OVERALL NEW MODEL DATA SHOWS NO REASON TO ADJUST ANYTHING ANYWHERE ELSE...COMMENTS FROM PREVIOUS UPDATE STILL VALID AS NEW DATA CONTINUES TO SHOW THAT PLENTY OF MOISTURE IS AVAILABLE AND THE DYNAMICS AND FORCING IS VERY STRONG. UPDATE ZONES AND WARNING OUT SHORTLY. && .PREV DISCUSSION... /ISSUED 750 PM EST SAT DEC 15 2007/ MESOSCALE ANALYSIS/UPDATE... CURRENT RADAR TRENDS SHOW INCREASING RETURNS WITH BANDS OF HEAVY SNOW ACROSS THE CENTRAL AND WESTERN PORTIONS OF THE FORECAST AREA...OVER THE EAST LIGHTER MIXED PRECIP WITH SLEET AND FRZ RAIN...FRZ RAIN MORE SO ACROSS THE VAN WERT AND LIMA OHIO AREAS. IMPORTANT FEATURE RIGHT NOW IS THE H850 LOW SITUATED NEAR SOUTHERN IL...WITH WAA WORKING INTO THE EASTERN HALF OF THE FORECAST AREA. 0C LINE NEAR LIMA OHIO TO NEAR GRISSOM AFB TO NEAR CRAWFORDSVILLE INDIANA. STRONG H850-700MB FRONTGENETICAL FORCING SEEN OVER NORTHERN IL INTO LOWER MI. HEAVY BANDED SNOW ACROSS NORTHERN ILLINOIS AT THIS TIME AND FURTHER SOUTH INTO MISSOURI. OVER THE NEXT 8 HOURS THE H850 LOW WILL TRAVEL TO NEAR MUNCIE INDIANA...AND THE 0 C LINE THAT WILL HAVE BEEN NEARLY STATIONARY AROUND OR JUST SOUTH OF LIMA OHIO AND MARION INDIANA WILL SHIFT EAST OF THE AREA ALLOWING FOR ALL SNOW BY 09Z FOR THE WHOLE FORECAST AREA. STRONGEST H850-700MB LAYER FRONTOGENETICAL FORCING ACROSS THE REGION WILL BE FROM 03 TO 12Z ACROSS THE REGION...ALONG WITH DECENT NORTHERLY AGEO WINDS AT 300MB HELPING TO PULL MASS FROM THE COLUMN AND ENHANCE LIFT...SLANTWISE INSTABILITY AND NEG EPV WHICH WILL HELP ADD A CONVECTIVE ELEMENT AND MAY ALLOW FOR VERY QUICK ACCUMULATING SNOWS OF 1-3" PER HOUR UNDER THESE BANDS. THEREFORE SOME LIGHTNING AND THUNDER TONIGHT MAY NOT BE OUT OF THE QUESTION ACROSS THE AREA...THUNDERSNOW IS A VERY INTERESTING RARE EVENT. CURRENT RUC THEN SHOWS THE STRONG H700-500MB LAYER FRONTOGENETICAL FORCING MOVING THRU FROM 09Z-18Z SUNDAY ALLOWING FOR CONTINUED MODERATE TO HEAVY SNOW POSSIBLE. PREV DISCUSSION... /ISSUED 625 PM EST SAT DEC 15 2007/ AVIATION (00Z TAFS)... IFR OR LIFR CONDITIONS WILL DOMINATE THE PERIOD ACROSS THE REGION. A STRONG WINTER SNOW STORM WILL BRING LOW CIGS AND VERY LOW VSBYS THROUGH MUCH OF THE NIGHT (LESS THAN 300FT AND 1/2 SM). SNOW WILL START TO INCREASE IN INTENSITY THROUGH THE EVENING INTO THE OVERNIGHT PERIOD...AS WELL AS THE WINDS. WINDS WILL BECOME STRONG WITH SUSTAIN VALUES NEAR 20KTS...AND GUSTS TO AROUND 30KTS CREATING POSSIBLE 0SM VSBY WITH BLSN THROUGH THE OVERNIGHT AND INTO EARLY SUNDAY. CONDITIONS WILL TREND TOWARDS MVFR LATE TOMORROW AFTERNOON OR EARLY EVENING AS THE SNOW ENDS AND THE CIGS BUMP UP SLIGHTLY...WINDS AND BLSN WILL STILL AN ISSUE SO HAVE VSBY AROUND 5SM...MAY NEED TO BE SLIGHTLY LESS BUT TYING TO BE OPTIMISTIC HERE. PREV DISCUSSION... /ISSUED 519 PM EST SAT DEC 15 2007/ SHORT TERM... TONIGHT THROUGH SUNDAY NEAR BLIZZARD CONDITIONS SUNDAY ENTIRE CWA. FOCUS ON MINOR TWEAKS WITH RESPECT TO SNOW ACCUMS AND ICE ACCRETION FAR SERN CWA THIS FORECAST CYCLE. NAM CONTINUES WELL WRAPPED/WARM SOLUTION THOUGH APPEARED TO FAIL TO PROPERLY CAPTURE PLACEMENT OF 8H LOW...TOO FAR WEST...WHICH MAY PLAY ROLE IN SLOWER/DEEPER/WARMER EVOLUTION OF ELEVATED WARM LAYER AHEAD OF DEEPENING SURFACE LOW TRACK. 20 UTC 1005MB SFC LOW NEAR KMEM WITH STRONG NNE-SSW ELONGATED 3HR PRESSURE FALLS GT 6MB/3HRS FM FAR WRN KY TO KLAF. SECONDARY PRESSURE FALL CENTER NEAR KHTS TO LIKELY BECOME DOMINANT NEXT SEVERAL HOURS AND LESS FAVOR SUCH EXTREME NWRN SURGE OF IP/ZR AS NAM WOULD INDICATE. ALSO COASTAL ENERGY TRANSFER START NOW UNDERWAY WITH INVERTED SURFACE TROFFING EVIDENT FROM AL TO OFF COAST OF CAROLINAS. FAVORING GFS/SREF SOLUTION OVERALL WITH LARGELY SNOW EVENT NWRN HALF. MIX OF SNOW/SLEET PRIMARILY TONIGHT AS WARM CONVEYOR PER KILN VWP AND SREF POINT SOUNDINGS AND 2-3KFT ABOVE 0C LAYER PER KAOH BUFKIT WET BULB PROFILE. NAM OF COURSE MUCH WARMER AND EVEN SUGGESTIVE OF CHANGEOVER TO RAIN AS NEARBY AS KFDY AND ZR TO KFWA...WILL STEER CLEAR FOR NOW. TOTALS LOWERED ONLY IN IP/ZR AREA BUT WITH SIGNIFICANT MOISTURE...GFS WITH 3.5-4 G/KG TAP 1000-850MB LAYER 07-13 UTC TIMEFRAME...SUN THIS WILL LIKELY BE AT HEIGHT OF MOST SIGNIFICANT SNOWFALL RATES ACROSS NWRN HALF CWA. CONVECTIVE ELEMENTS OBSERVED IN KLSX RADAR AND WITH TIMING AND STRENGTH OF MID LEVEL DEFORMATION HAVE ADDED SLIGHT CHANCE THUNDER IN AFTER MIDNIGHT IN HEAVY SNOW WITH SNOWFALL RATES 2-3 INCHES/HOUR ARE WHERE CHARGE SEPARATION MORE LIKELY THAN IN MIXED PRECIP AREA OF SERN ZONES. QUICK CHANGE OVER IN ERN/SERN ZONES TO ALL SNOW BEFORE DAYBREAK SUNDAY AS COASTAL LOW BECOMES DOMINANT AND COLUMN COOLS SIGNIFICANTLY. WINDS A GRAVE CONCERN ESPECIALLY TO E-W RUNNING ROADS 6/30/24/TOLL ROAD/TO IMPASSABLE COUNTY ROADS DRIFTED SHUT. MENTION OF NEAR BLIZZARD CONDITIONS IN BLOWING/DRIFTING SNOW ALL BUT FAR SERN ZONES TONIGHT AND ENTIRE CWA BY SUNDAY WITH SERN ZONES PICKING UP ONE-HALF TO NEAR ONE FOOT OF SNOW WITH OVER 1-2 INCH/HOUR RATES OF DRY ENOUGH SNOW TO BLOW/DRIFT ON TOP OF FEW TENTHS CONGLOMERATION OF ZR/IP WITH NRLY WINDS TO 35 MPH. BAND OF HEAVIEST TOTAL SNOWS WHITE CO NE TO MARSHALL TO ELKHART TO BRANCH/HILLSDALE MI COUNTIES TO AROUND 15 INCHES. LONG TERM... LONG TERM PERIOD WILL CONTINUE TO FEATURE AN ACTIVE FLOW REGIME WITH NUMEROUS MID LEVEL IMPULSES TAKING AIM AT THE REGION. WATER VAPOR SATELLITE OVER THE PACIFIC OCEAN VERIFIES NUMEROUS POTENT TROUGHS THAT WILL QUICKLY SHIFT EAST TOWARD THE REGION. MID-LEVEL FLOW CHANGE TO MORE ZONAL WEST-EAST FLOW WILL SUPPORT A SLIGHT WARMER CONDITIONS BY TUESDAY...BRINGING TEMPS CLOSER TO OR JUST SLIGHTLY ABOVE NORMAL FOR THE REGION...AS THE MAIN NORTHERN STREAM STORM TRACK SHIFTS INTO THE NORTHERN TIER. MODELS AND ENSEMBLES ARE IN PRETTY GOOD AGREEMENT THROUGH THE MAJORITY OF THE PERIOD SAVE THE WEEKEND...AND HAVE TRENDED FORECAST TO THE 12Z GFS AND 12Z AND 00Z ECMWF. LOOK FOR A SLOW RECOVERY IN TEMPS THROUGH MID WEEK WITH EXPECTED SNOW COVER IN PLACE. CONTINUED TO OPT FOR COOL BELOW GUIDANCE TEMPS...IN LINE WITH PREVIOUS FORECAST. RETAINED POP CHANCES THUR AND FRI. WEAK SOUTHERN STREAM WAVE WILL SUPPORT THE DEVELOPMENT OF WEAK LOW PRESSURE OVER THE LOWER MISSISSIPPI VALLEY. WARMER THERMAL PROFILES ARE STILL SUPPORTING RAIN. HOWEVER...WILL RETAIN SNOW MENTION DUE TO POSSIBLE COOLER MODEL SOLUTIONS ONCE NEW SNOW FIELD IS ASSIMILATED...AS PER PREVIOUS FORECAST. SATURDAY...ANOTHER LARGE STORM SYSTEM MAY BE POSSIBLE NEXT WEEKEND...AS A DEEPER MID LEVEL TROUGH DIGS OVER THE WESTERN US...EVENTUALLY EJECTING OUT INTO THE THE SOUTHERN PLAINS. LATEST RUN OF THE ECMWF NO LONGER FAVORS PHASING OF THE NORTHERN AND SOUTHERN STREAMS...AND OPTS FOR A SLOWER/WEAKER SYSTEM OVER THE GULF COAST. THE GFS WITH SOME SUPPORT OF PREVIOUS ENSEMBLE RUNS DO FAVOR PHASING WITH THE DEVELOPMENT OF A MORE INTENSE SFC LOW. THIS WOULD POSSIBLY SPELL MORE ACCUMULATING SNOW FOR THE REGION. HOWEVER...WITH SUCH A LARGE ENSEMBLE SPREAD/CURRENT POOR SAMPLING ISSUES NOTED OVER THE PACIFIC/AND LARGE DETERMINISTIC SOLUTION SPREADS...HAVE OPTED DRY FOR NOW. THIS PERIOD WILL NEED TO BE MONITORED. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...WINTER STORM WARNING UNTIL 7 PM EST /6 PM CST/ SUNDAY FOR INZ003>009-012>018-020-022>027-032>034. MI...WINTER STORM WARNING UNTIL 7 PM EST SUNDAY FOR MIZ077>081. OH...WINTER STORM WARNING UNTIL 7 PM EST SUNDAY FOR OHZ001-002-004- 005-015-016-024-025. LM...GALE WARNING UNTIL 7 PM EST SUNDAY FOR LMZ043-046. && $$ SHORT TERM...MURPHY LONG TERM...CHAMBERLAIN UPDATE...SCHOTT in AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NORTHERN INDIANA 750 PM EST SAT DEC 15 2007 .MESOSCALE ANALYSIS/UPDATE... CURRENT RADAR TRENDS SHOW INCREASING RETURNS WITH BANDS OF HEAVY SNOW ACROSS THE CENTRAL AND WESTERN PORTIONS OF THE FORECAST AREA...OVER THE EAST LIGHTER MIXED PRECIP WITH SLEET AND FRZ RAIN...FRZ RAIN MORE SO ACROSS THE VAN WERT AND LIMA OHIO AREAS. IMPORTANT FEATURE RIGHT NOW IS THE H850 LOW SITUATED NEAR SOUTHERN IL...WITH WAA WORKING INTO THE EASTERN HALF OF THE FORECAST AREA. 0C LINE NEAR LIMA OHIO TO NEAR GRISSOM AFB TO NEAR CRAWFORDSVILLE INDIANA. STRONG H850-700MB FRONTGENETICAL FORCING SEEN OVER NORTHERN IL INTO LOWER MI. HEAVY BANDED SNOW ACROSS NORTHERN ILLINOIS AT THIS TIME AND FURTHER SOUTH INTO MISSOURI. OVER THE NEXT 8 HOURS THE H850 LOW WILL TRAVEL TO NEAR MUNCIE INDIANA...AND THE 0 C LINE THAT WILL HAVE BEEN NEARLY STATIONARY AROUND OR JUST SOUTH OF LIMA OHIO AND MARION INDIANA WILL SHIFT EAST OF THE AREA ALLOWING FOR ALL SNOW BY 09Z FOR THE WHOLE FORECAST AREA. STRONGEST H850-700MB LAYER FRONTOGENETICAL FORCING ACROSS THE REGION WILL BE FROM 03 TO 12Z ACROSS THE REGION...ALONG WITH DECENT NORTHERLY AGEO WINDS AT 300MB HELPING TO PULL MASS FROM THE COLUMN AND ENHANCE LIFT...SLANTWISE INSTABILITY AND NEG EPV WHICH WILL HELP ADD A CONVECTIVE ELEMENT AND MAY ALLOW FOR VERY QUICK ACCUMULATING SNOWS OF 1-3" PER HOUR UNDER THESE BANDS. THEREFORE SOME LIGHTNING AND THUNDER TONIGHT MAY NOT BE OUT OF THE QUESTION ACROSS THE AREA...THUNDERSNOW IS A VERY INTERESTING RARE EVENT. CURRENT RUC THEN SHOWS THE STRONG H700-500MB LAYER FRONTOGENETICAL FORCING MOVING THRU FROM 09Z-18Z SUNDAY ALLOWING FOR CONTINUED MODERATE TO HEAVY SNOW POSSIBLE. && .PREV DISCUSSION... /ISSUED 625 PM EST SAT DEC 15 2007/ AVIATION (00Z TAFS)... IFR OR LIFR CONDITIONS WILL DOMINATE THE PERIOD ACROSS THE REGION. A STRONG WINTER SNOW STORM WILL BRING LOW CIGS AND VERY LOW VSBYS THROUGH MUCH OF THE NIGHT (LESS THAN 300FT AND 1/2 SM). SNOW WILL START TO INCREASE IN INTENSITY THROUGH THE EVENING INTO THE OVERNIGHT PERIOD...AS WELL AS THE WINDS. WINDS WILL BECOME STRONG WITH SUSTAIN VALUES NEAR 20KTS...AND GUSTS TO AROUND 30KTS CREATING POSSIBLE 0SM VSBY WITH BLSN THROUGH THE OVERNIGHT AND INTO EARLY SUNDAY. CONDITIONS WILL TREND TOWARDS MVFR LATE TOMORROW AFTERNOON OR EARLY EVENING AS THE SNOW ENDS AND THE CIGS BUMP UP SLIGHTLY...WINDS AND BLSN WILL STILL AN ISSUE SO HAVE VSBY AROUND 5SM...MAY NEED TO BE SLIGHTLY LESS BUT TYING TO BE OPTIMISTIC HERE. PREV DISCUSSION... /ISSUED 519 PM EST SAT DEC 15 2007/ SHORT TERM... TONIGHT THROUGH SUNDAY NEAR BLIZZARD CONDITIONS SUNDAY ENTIRE CWA. FOCUS ON MINOR TWEAKS WITH RESPECT TO SNOW ACCUMS AND ICE ACCRETION FAR SERN CWA THIS FORECAST CYCLE. NAM CONTINUES WELL WRAPPED/WARM SOLUTION THOUGH APPEARED TO FAIL TO PROPERLY CAPTURE PLACEMENT OF 8H LOW...TOO FAR WEST...WHICH MAY PLAY ROLE IN SLOWER/DEEPER/WARMER EVOLUTION OF ELEVATED WARM LAYER AHEAD OF DEEPENING SURFACE LOW TRACK. 20 UTC 1005MB SFC LOW NEAR KMEM WITH STRONG NNE-SSW ELONGATED 3HR PRESSURE FALLS GT 6MB/3HRS FM FAR WRN KY TO KLAF. SECONDARY PRESSURE FALL CENTER NEAR KHTS TO LIKELY BECOME DOMINANT NEXT SEVERAL HOURS AND LESS FAVOR SUCH EXTREME NWRN SURGE OF IP/ZR AS NAM WOULD INDICATE. ALSO COASTAL ENERGY TRANSFER START NOW UNDERWAY WITH INVERTED SURFACE TROFFING EVIDENT FROM AL TO OFF COAST OF CAROLINAS. FAVORING GFS/SREF SOLUTION OVERALL WITH LARGELY SNOW EVENT NWRN HALF. MIX OF SNOW/SLEET PRIMARILY TONIGHT AS WARM CONVEYOR PER KILN VWP AND SREF POINT SOUNDINGS AND 2-3KFT ABOVE 0C LAYER PER KAOH BUFKIT WET BULB PROFILE. NAM OF COURSE MUCH WARMER AND EVEN SUGGESTIVE OF CHANGEOVER TO RAIN AS NEARBY AS KFDY AND ZR TO KFWA...WILL STEER CLEAR FOR NOW. TOTALS LOWERED ONLY IN IP/ZR AREA BUT WITH SIGNIFICANT MOISTURE...GFS WITH 3.5-4 G/KG TAP 1000-850MB LAYER 07-13 UTC TIMEFRAME...SUN THIS WILL LIKELY BE AT HEIGHT OF MOST SIGNIFICANT SNOWFALL RATES ACROSS NWRN HALF CWA. CONVECTIVE ELEMENTS OBSERVED IN KLSX RADAR AND WITH TIMING AND STRENGTH OF MID LEVEL DEFORMATION HAVE ADDED SLIGHT CHANCE THUNDER IN AFTER MIDNIGHT IN HEAVY SNOW WITH SNOWFALL RATES 2-3 INCHES/HOUR ARE WHERE CHARGE SEPARATION MORE LIKELY THAN IN MIXED PRECIP AREA OF SERN ZONES. QUICK CHANGE OVER IN ERN/SERN ZONES TO ALL SNOW BEFORE DAYBREAK SUNDAY AS COASTAL LOW BECOMES DOMINANT AND COLUMN COOLS SIGNIFICANTLY. WINDS A GRAVE CONCERN ESPECIALLY TO E-W RUNNING ROADS 6/30/24/TOLL ROAD/TO IMPASSABLE COUNTY ROADS DRIFTED SHUT. MENTION OF NEAR BLIZZARD CONDITIONS IN BLOWING/DRIFTING SNOW ALL BUT FAR SERN ZONES TONIGHT AND ENTIRE CWA BY SUNDAY WITH SERN ZONES PICKING UP ONE-HALF TO NEAR ONE FOOT OF SNOW WITH OVER 1-2 INCH/HOUR RATES OF DRY ENOUGH SNOW TO BLOW/DRIFT ON TOP OF FEW TENTHS CONGLOMERATION OF ZR/IP WITH NRLY WINDS TO 35 MPH. BAND OF HEAVIEST TOTAL SNOWS WHITE CO NE TO MARSHALL TO ELKHART TO BRANCH/HILLSDALE MI COUNTIES TO AROUND 15 INCHES. LONG TERM... LONG TERM PERIOD WILL CONTINUE TO FEATURE AN ACTIVE FLOW REGIME WITH NUMEROUS MID LEVEL IMPULSES TAKING AIM AT THE REGION. WATER VAPOR SATELLITE OVER THE PACIFIC OCEAN VERIFIES NUMEROUS POTENT TROUGHS THAT WILL QUICKLY SHIFT EAST TOWARD THE REGION. MID-LEVEL FLOW CHANGE TO MORE ZONAL WEST-EAST FLOW WILL SUPPORT A SLIGHT WARMER CONDITIONS BY TUESDAY...BRINGING TEMPS CLOSER TO OR JUST SLIGHTLY ABOVE NORMAL FOR THE REGION...AS THE MAIN NORTHERN STREAM STORM TRACK SHIFTS INTO THE NORTHERN TIER. MODELS AND ENSEMBLES ARE IN PRETTY GOOD AGREEMENT THROUGH THE MAJORITY OF THE PERIOD SAVE THE WEEKEND...AND HAVE TRENDED FORECAST TO THE 12Z GFS AND 12Z AND 00Z ECMWF. LOOK FOR A SLOW RECOVERY IN TEMPS THROUGH MID WEEK WITH EXPECTED SNOW COVER IN PLACE. CONTINUED TO OPT FOR COOL BELOW GUIDANCE TEMPS...IN LINE WITH PREVIOUS FORECAST. RETAINED POP CHANCES THUR AND FRI. WEAK SOUTHERN STREAM WAVE WILL SUPPORT THE DEVELOPMENT OF WEAK LOW PRESSURE OVER THE LOWER MISSISSIPPI VALLEY. WARMER THERMAL PROFILES ARE STILL SUPPORTING RAIN. HOWEVER...WILL RETAIN SNOW MENTION DUE TO POSSIBLE COOLER MODEL SOLUTIONS ONCE NEW SNOW FIELD IS ASSIMILATED...AS PER PREVIOUS FORECAST. SATURDAY...ANOTHER LARGE STORM SYSTEM MAY BE POSSIBLE NEXT WEEKEND...AS A DEEPER MID LEVEL TROUGH DIGS OVER THE WESTERN US...EVENTUALLY EJECTING OUT INTO THE THE SOUTHERN PLAINS. LATEST RUN OF THE ECMWF NO LONGER FAVORS PHASING OF THE NORTHERN AND SOUTHERN STREAMS...AND OPTS FOR A SLOWER/WEAKER SYSTEM OVER THE GULF COAST. THE GFS WITH SOME SUPPORT OF PREVIOUS ENSEMBLE RUNS DO FAVOR PHASING WITH THE DEVELOPMENT OF A MORE INTENSE SFC LOW. THIS WOULD POSSIBLY SPELL MORE ACCUMULATING SNOW FOR THE REGION. HOWEVER...WITH SUCH A LARGE ENSEMBLE SPREAD/CURRENT POOR SAMPLING ISSUES NOTED OVER THE PACIFIC/AND LARGE DETERMINISTIC SOLUTION SPREADS...HAVE OPTED DRY FOR NOW. THIS PERIOD WILL NEED TO BE MONITORED. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...WINTER STORM WARNING UNTIL 7 PM EST /6 PM CST/ SUNDAY FOR INZ003>009-012>018-020-022>027-032>034. MI...WINTER STORM WARNING UNTIL 7 PM EST SUNDAY FOR MIZ077>081. OH...WINTER STORM WARNING UNTIL 7 PM EST SUNDAY FOR OHZ001-002-004- 005-015-016-024-025. LM...GALE WARNING UNTIL 7 PM EST SUNDAY FOR LMZ043-046. && $$ SHORT TERM...MURPHY LONG TERM...CHAMBERLAIN UPDATE/AVIATION...SCHOTT in AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE QUAD CITIES IA IL 238 PM CST SAT DEC 15 2007 .SYNOPSIS... THE LARGE WINTER STORMS IS TRACKING STRONGER...SLOWER...AND FARTHER NORTH THAN EARLIER DATA HAD INDICATED. FORTUNATELY THE LOCAL FORECAST HAD ANTICIPATED THIS TREND...AND SNOW AMOUNTS ARE FALLING INTO LINE WITH OUR ADVISORY WHICH COVERS THE SOUTHEAST 2/3RDS OF THE CWA. AS OF 1 PM...WIDESPREAD 1 TO 2 INCHES HAVE BEEN REPORTED...AND THE DEFORMATION ZONE IS NOW IN PLACE OVER THE CWA AND IS SNOWING MODERATELY IN MANY LOCATIONS. SEVERAL INTENSE SNOW BANDS ARE MOVING NORTH AND PIVOTING NEAR THE MISSISSIPPI RIVER AND RUC DATA SHOWS THAT MAY CONTINUE UNTIL AROUND 02Z OR SO. && .SHORT TERM...REST OF TODAY AND TONIGHT... THE SNOW ADVISORY WILL REMAIN IN PLACE WITH THE WEST EXPIRING AT 9 PM...AND THE EAST AT MIDNIGHT. WIDESPREAD 2 TO 4 INCHES ARE VERY LIKELY...WITH SEVERAL BANDS OF 5 TO 6 POSSIBLE...ESPECIALLY ALONG AND EAST OF THE MISSISSIPPI RIVER. TOWARDS MID EVENING...THE WIND SHOULD PICK UP TO 10 TO 20...WITH GUSTS TO 25 MPH. THIS COMBINED WITH THE VERY POWDERY SNOW WILL CREATE WIDESPREAD DRIFTING...AND LOW LEVEL BLOWING SNOW. WE WILL NOT ISSUE AN ADVISORY FOR THIS POTENTIAL AT THIS TIME...BUT WILL PASS A CONCERN ON TO THE NEXT SHIFT AS IT MAY PREVENT RURAL ROADS FROM STAYING CLEARED OFF. TEMPS SHOULD DROP AFTER MIDNIGHT AS COLD ADVECTION KICKS IN ACROSS FRESH SNOW. ERVIN .LONG TERM...TOMORROW THROUGH SATURDAY... MAIN FORECAST ISSUES IN THE LONGER TERM ARE TEMPERATURES THROUGHOUT...AS WELL AS THE POTENTIAL FOR PRECIP MIDWEEK AND OVER THE WEEKEND. IN WAKE OF THE CURRENT SRN STREAM UPPER LOW...PATTERN BECOMES MORE ZONAL AS LOW LIFTS ACROSS THE NERN STATES WHILE NEXT UPPER TROUGH DIGS IN ALONG THE W COAST. NWLY FLOW TOMORROW...ALONG WITH FRESH SNOW...WILL KEEP TEMPS FROM RISING TOO FAR...AND HAVE CONTINUED PREVIOUS SHIFT THINKING TO UNDERCUT GUIDANCE BY A CAT OR TWO. TEMPS IN NEB/KS TODAY SUPPORT THIS AS WELL...WITH TEMPS STUCK IN THE MID-TEENS TO LOW 20S. CWA ON MONDAY WILL BE PINCHED BETWEEN SFC RIDGE TO THE S WITH UPPER-LEVEL SHORTWAVE RIDGE...AND CLIPPER DIVING THROUGH THE NRN GT LAKES TO THE N. BELIEVE CLIPPER WILL STAY WELL N...AND HAVE KEPT FCST DRY AND MOSTLY CLEAR THROUGH TUES WITH JUST SOME INCREASED CLOUDS IN THE NERN CWA EARLY MON. ANOTHER CLIPPER MOVING THROUGH THE NRN GT LAKES ON LATE TUES WILL DRAG A WEAK COLD FRONT THROUGH THE CWA...PROVIDING A REINFORCING SHOT OF COLD AIR AS WELL AS SOME CLOUDS BUT LIKELY REMAINING DRY. WOULD NOT RULE OUT NON-MEASURABLE FLURRIES...BUT DID NOT INCLUDE IN THE GRIDS JUST YET. 850MB TEMPS DO MODERATE THROUGH THE EARLY WEEK...BUT WEAK SFC FLOW WILL BRING LITTLE RESPONSE...AND HAVE SIDED CLOSE TO COOLER GFS ENSEMBLE GUIDANCE TEMPS THROUGHOUT MUCH OF THE LONG-TERM. GFS/ECMWF/GEM INDICATE AN UPPER TROUGH MOVING THROUGH THE ZONAL FLOW ACROSS THE CENTRAL US...CROSSING THE CWA ON WED NIGHT/EARLY THURS. MODELS DO KEEP THE WAVE WEAK AND FAST-MOVING...AND AGREE WITH THE FASTER-MOVING/WEAKER SCENARIO WITH UPPER JET INFLUENCE MAINLY ZONAL BEHIND IT. 12Z ECMWF TRENDED SLIGHTLY SWD WITH SYSTEM FROM 00Z RUN...AND AM LEANING TOWARD THIS SOLUTION. 850MB FLOW AHEAD OF THE SYSTEM WILL DRAG MOISTURE INTO THE MID-MS/OH RIVER VALLEYS...WITH PRECIP BLOSSOMING AS WAVE REACHES THAT REGION. SYSTEM ALSO FORCES A WEAK SFC LOW TO MOVE ACROSS KS/MO INTO IL. BELIEVE MODELS ARE NOT YET HANDLING THE SNOWPACK WELL...AND AM A LITTLE LEERY OF WHERE THE BAROCLINIC ZONE WILL SET UP WITH THIS SYSTEM. WILL LEAN TOWARD COOLER TEMPS...WITH BAROCLINIC ZONE REMAINING S OF THE CWA. SHOULD SUB-FREEZING TEMPS GET LOCKED IN AT THE SFC...850MB WARM NOSE COULD BRING SOME FREEZING RAIN ON WED NIGHT...PARTICULARLY IN THE SERN CWA. WOULD EXPECT LIGHTER PRECIP TOTALS WITH MOST MOISTURE FOCUSED S/SE OF THE CWA. FOR NOW... HAVE MENTIONED SN/ZR MIX ON WED NIGHT...CHANGING TO ALL SNOW ON THURS AS COLDER 850MB TEMPS SPILL IN BEHIND THE UPPER WAVE. OTHER SCENARIO WOULD BE A RAIN/SNOW MIX CHANGING TO SNOW IF SFC TEMPS DO REMAIN ABOVE FREEZING. AFTER SYSTEM PASSES THROUGH DURING THE DAY THURS...WILL AGAIN SEE A COUPLE OF QUIET DAYS IN ADVANCE OF NEXT SYSTEM. ECMWF/GFS/ENSEMBLES INDICATE ANOTHER SWRN UPPER LOW DIGS IN BY FRI/EARLY SAT. BELIEVE GFS IS TOO QUICK IN EJECTING THE UPPER LOW...AND SUSPECT BOTH MODELS ARE TENDING TO PUSH THE LOW TOO FAR SE AS IT EJECTS ACROSS THE CENTRAL US. WITH THAT TREND IN MIND...HAVE INSERTED CHC POPS FOR SN ON SAT/SAT NIGHT...THOUGH PRECIP TYPE COULD BE LESS THAN CERTAIN. STILL QUITE A BIT OF TIME TO WATCH THIS SYSTEM DEVELOP...BUT WILL KEEP A CLOSE EYE AS IT COULD AFFECT HOLIDAY TRAVEL. MAYES && .AVIATION... LIGHT TO MODERATE SNOW WILL CONTINUE THROUGH AROUND 00Z WEST AND 04Z EAST...WITH OCCASIONAL LOW CIGS UNDER 1000FT AND VSBY LESS THAN 1/2 MILE. AFTER MIDNIGHT SCATTERED TO BROKEN STRATUS AROUND 1500 FT SHOULD GRADUALLY CLEAR FROM NORTH TO SOUTH. ERVIN && .DVN WATCHES/WARNINGS/ADVISORIES... IA...SNOW ADVISORY UNTIL MIDNIGHT CST TONIGHT FOR CLINTON-JACKSON- SCOTT. SNOW ADVISORY UNTIL 9 PM CST THIS EVENING FOR CEDAR-DES MOINES- HENRY IA-IOWA-JEFFERSON-JOHNSON-KEOKUK-LEE-LOUISA-MUSCATINE- VAN BUREN-WASHINGTON. IL...SNOW ADVISORY UNTIL MIDNIGHT CST TONIGHT FOR BUREAU-CARROLL- HANCOCK-HENDERSON-HENRY IL-JO DAVIESS-MCDONOUGH-MERCER- PUTNAM-ROCK ISLAND-STEPHENSON-WARREN-WHITESIDE. MO...SNOW ADVISORY UNTIL 9 PM CST THIS EVENING FOR CLARK-SCOTLAND. && $$ ERVIN/MAYES ia AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TOPEKA KS 322 PM CST SAT DEC 15 2007 .DISCUSSION... 21Z WATER VAPOR IMAGERY SHOWS MID AND UPPER TROUGH RESPONSIBLE FOR THE SNOW WAS OVER EASTERN KS CONTINUING TO PROPAGATE EAST. DEFORMATION ZONE FROM THIS WAVE HAS ALLOWED LIGHT SNOW TO PERSIST ACROSS FAR EASTERN KS. MEANWHILE AT THE SFC ACROSS WESTERN KS VERY DRY AIR WAS FILLING IN. CONCERNS FOR TONIGHT AND SUNDAY ARE TEMPERATURES. THE NEW SNOW COVER AND CLEARING SKIES WILL SET UP AN IDEAL RADIATIONAL COOLING SITUATION. BECAUSE OF THIS...HAVE UNDERCUT GUIDANCE FOR MIN TEMPS TONIGHT BY SEVERAL DEGREES. IN THE LOW SPOTS...EXPECT TO SEE MORNING LOWS IN THE SINGLE DIGITS. THERE IS ALSO A CONCERN FOR FOG TO DEVELOP. BOTH THE NAM AND RUC SHOW SFC RH VALUES AT 100 PERCENT THROUGH THE NIGHT. WITH A STRONG NOCTURNAL INVERSION ANTICIPATED...THINK SOME PATCHY FOG COULD FORM IN THE LOW LYING AREAS...ESPECIALLY AROUND RIVERS AND LAKES WHERE AND ADDITIONAL MOISTURE SOURCE WILL AID IN DEVELOPMENT. MAIN DETRACTOR FROM FOG FORMATION IS THE WESTERLY WINDS AND DRY AIR ADVECTING IN. THINK THIS WILL PREVENT FOG FROM BEING WIDESPREAD. ALTHOUGH SKIES SHOULD BE MOSTLY SUNNY FOR SUNDAY...NEW SNOW ON THE GROUND WILL TAKE A LITTLE TIME TO MELT. HAVE AGAIN UNDERCUT THE MAV GUIDANCE. THIS UNDER CUTTING IS MOST PRONOUNCED ACROSS NORTH CENTRAL AND FAR NORTHEAST KS WERE THE SNOW PACK IS DEEPER AND WHERE THE SOUTHWESTERLY WINDS WILL HAVE A MUCH LONGER FETCH OF SNOW TO MOVE ACROSS. EAST CENTRAL KS...WHERE THERE IS LESS SNOW...COULD BREAK THE FREEZING MARK BY MID AFTERNOON AND WENT CLOSER TO THE MAV NUMBERS HERE. OTHERWISE... SNOWFALL SHOULD FOR THE MOST PART BE OVER WITH BY 00Z THIS EVENING. HAVE HELD ONTO SOME SMALL POPS ACROSS FAR EASTERN SECTIONS OF THE FORECAST AREA FOR COLLABORATION. FOR THE MOST PART EXPECT FLURRIES AND WILL LET THE SNOW ADVISORY EXPIRE AT 4 PM -WOLTERS FOR SUNDAY NIGHT THROUGH TUESDAY NIGHT...GENERALLY ZONAL FLOW EXPECTED DURING THIS PERIOD. TEMPERATURES WILL GRADUALLY WARM THROUGH THE FIRST PART OF THE WORK WEEK AND CWA WILL SEE A BREAK FROM THE WINTER PRECIPITATION FOR A FEW DAYS. SNOW COVER... ESPECIALLY IN THE WESTERN AND NORTHERN PORTIONS OF THE CWA...SHOULD LIMIT WARM UP INITIALLY. AT THE SURFACE...HIGH PRESSURE IN THE SOUTHERN PLAINS WILL MOVE EAST ALONG THE GULF COAST AS LEE TROF DEVELOPS IN THE HIGH PLAINS. SURFACE WINDS SHIFT FROM WESTERLY TO SOUTH BY MONDAY WHICH ADVECTS WARMER AIR INTO THE CWA. SHORTWAVE TROF IS EXPECTED TO MOVE ACROSS KANSAS WEDNESDAY AND WEDNESDAY NIGHT. LOW LEVEL MOISTURE INCREASES AHEAD OF THIS FEATURE AND EXPECT SOME LIGHT PRECIPITATION TO DEVELOP OVER THE CWA WEDNESDAY EVENING. FORECAST SOUNDINGS INDICATE SURFACE TEMPERATURES ABOVE FREEZING DURING MUCH OF THIS EVENING...THEN FALLING BELOW FREEZING AROUND 12Z COINCIDENT WITH MID LEVEL DRYING. EXPECT PRECIPITATION TO BE RAIN INITIALLY THEN A POSSIBLE CHANGE TO SNOW OR LIGHT FREEZING DRIZZLE BEFORE ENDING. HAVE OPTED TO GO WITH CHANCE OF RAIN OR SNOW IN THE FORECAST FOR NOW. FAST WESTERLY FLOW ALOFT CONTINUES THURSDAY AND FRIDAY BEFORE NEXT TROF DIVES INTO THE WESTERN U.S. GFS AND EUROPEAN BOTH IMPRESSIVE WITH THE STRENGTH OF THIS NEXT SYSTEM. HAVE INCLUDED POPS IN THE FORECAST FOR FRIDAY NIGHT AND SATURDAY...ANOTHER ROUND OF WINTER WEATHER POSSIBLE THE WEEKEND BEFORE THE CHRISTMAS HOLIDAY. STARK .AVIATION... CONCERN TONIGHT IS WHETHER SOME DENSE FOG OR LIFR CIGS WILL DEVELOP IN THE WAKE OF THE SYSTEM. ATTM AM THINKING THAT THE BOUNDARY LAYER WILL DECOUPLE WITH A STRONG NOCTURNAL INVERSION SETTING UP DUE TO THE SNOW COVER. WITH SKIES ALREADY CLEARING FROM THE WEST...THIS SHOULD LEAD TO FOG FORMATION WITH A 1/2SM TO 1/4SM WITH FZFG NOT OUT OF THE QUESTION IN THE RIVER VALLEY. FOE WHICH IS 200FT HIGHER COULD SEE MORE MIXING OF DRY AIR AND VSBY MAY NOT BE AS LOW. EVENING SHIFT WILL NEED TO MONITOR. -WOLTERS && .TOP WATCHES/WARNINGS/ADVISORIES...NONE. && $$ ks AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WICHITA KS 1229 PM CST SAT DEC 15 2007 .UPDATE... PERSISTENT COMMA HEAD/TROWAL PRECIPITATION WILL CONTINUE ACROSS SOUTHEAST KANSAS THROUGH THE AFTERNOON HOURS. TOTAL ACCUMULATIONS WILL RANGE FROM 2-5 INCHES...WITH A FEW LOCATIONS POSSIBLY UP TO 6 INCHES GIVEN THE DECENT FRONTOGENETICAL FORCING AND SOME INSTABILITY (DUE TO PROXIMITY OF THE DRY SLOT). WILL THEREFORE CONTINUE WINTER WEATHER ADVISORY UNTIL 6 PM ACROSS SOUTHEAST KS. PRECIPITATION WILL BE ENDING NORTHWEST OF THE TURNPIKE SHORTLY...SO WILL LIKELY LET WINTER WEATHER ADVISORY NEAR/ALONG THE TURNPIKE EXPIRE AT 1 PM. KLEINSASSER && .AVIATION... 18Z TAFS...ICT/HUT/CNU/RSL/SLN...LIGHT TO MODERATE SNOW WILL CONTINUE ACROSS SOUTHEAST KS THROUGH THE AFTERNOON HOURS...WITH LIGHT SNOW COMING TO AN END BY EARLY TO MID AFTERNOON NEAR/ALONG AND NORTHWEST OF THE TURNPIKE. VISIBILITIES WILL BE REDUCED TO LESS THAN 1 MILE AT TIMES IN THE HEAVIEST SNOW BANDS ACROSS SOUTHEAST KANSAS. MVFR TO LOW VFR CIGS WILL PERSIST THROUGH THE EVENING AND INTO THE OVERNIGHT HOURS...BUT WILL EVENTUALLY CLEAR FROM THE NORTHWEST TONIGHT. KLEINSASSER && .PREV DISCUSSION... /ISSUED 744 AM CST SAT DEC 15 2007/ UPDATE... UPDATED TO INCREASE SNOWFALL AMOUNTS FOR THE 12-18Z TIME FRAME AS A BAND OF MODERATE SNOW HAS SET UP FROM NORTHERN KM COUNTY THROUGH MARION COUNTY. THIS BAND OF SNOW IS RELATED TO THE MAIN UPPER CIRCULATION THAT IS CURRENTLY TRACKING EAST ACROSS SOUTH CENTRAL KS. CROSS-SECTIONS OFF OF THE RUC ARE SHOWING IMPRESSIVE LIFT IN THE DENDRITIC ZONE WITH SURPRISINGLY DECENT INSTABILITY ABOVE 700MB. THIS WILL RESULT IN A CONTINUATION OF A MODERATE SNOW BAND THAT SHOULD SLIDE FAIRLY QUICKLY ACROSS THE FORECAST AREA. LOCATIONS AFFECTED BY THIS BAND SHOULD PICK UP AN ADDITIONAL 1-3 INCHES THROUGH NOON. LAWSON PREV DISCUSSION... /ISSUED 526 AM CST SAT DEC 15 2007/ AVIATION... FOR 12Z TAFS...MAIN AVIATION CONCERN WILL BE LOW CIGS AND VIS RESTRICTIONS DUE TO SNOW. THE ONLY SITES WHERE THERE IS HIGH CONFIDENCE OF IFR CONDITIONS ARE KCNU AND KSLN. KSLN WOULD BE MORE FOR THE SHORT TERM LOWER VIS DUE TO A BAND OF HEAVIER SNOWFALL MOVING OVER THEM. HOWEVER KCNU WILL BE BOUNCING IN AND OUT OF IFR CONDITIONS THROUGHOUT THE DAY AS THE SNOW SHOWERS LINGER LONGER OVER SE KS. WHILE LOW CLOUDS WILL BLANKET ALL SITES THROUGH AT LEAST 21Z...CONFIDENCE WAS ONLY HIGH ENOUGH TO PUT IFR CIGS IN A TEMPO GROUP FOR THE FIRST FEW HOURS(WITH THE EXCEPTION OF KCNU) WITH MVFR CIGS THE PREDOMINATE CLOUD HEIGHT. WHILE LIGHT SNOW WILL LINGER ACROSS CENTRAL AND SOUTH CENTRAL KS THROUGH AT LEAST NOON...IT SHOULD REMAIN LIGHT AND ONLY HAVE A MINIMAL AFFECT ON VIS. PREV DISCUSSION... /ISSUED 403 AM CST SAT DEC 15 2007/ AVIATION... 06Z TAFS...DRY SLOT IS MOVING INTO SOUTH CENTRAL KANSAS AT TAF ISSUANCE TIME...AND WILL KEEP PRECIPITATION LIGHT OR STOP IT ALTOGETHER FOR A TIME OVERNIGHT. SOUTHEAST KANSAS COULD SEE SOME INTERMITTENT FREEZING RAIN...BUT WILL CHANGE BACK TO SNOW BY MORNING. IFR TO LIFR CONDITIONS ARE EXPECTED FOR THE BULK OF THE TAF PERIOD. SNOW WILL INCREASE IN COVERAGE AND INTENSITY AGAIN SATURDAY MORNING AND WILL END DURING THE AFTERNOON HOURS FROM THE WEST. SCHRECK && .PRELIMINARY POINT TEMPS/POPS... WICHITA-KICT 26 12 36 17 / 100 0 0 0 HUTCHINSON 25 9 34 17 / 100 0 0 0 NEWTON 25 10 33 18 / 100 0 0 0 ELDORADO 25 11 34 18 / 100 10 0 0 WINFIELD-KWLD 28 14 37 18 / 100 0 0 0 RUSSELL 25 5 33 13 / 100 0 0 0 GREAT BEND 25 7 34 15 / 100 0 0 0 SALINA 26 8 34 12 / 100 0 0 0 MCPHERSON 25 9 33 16 / 100 0 0 0 COFFEYVILLE 30 15 38 19 / 100 10 0 0 CHANUTE 27 13 35 16 / 100 10 0 0 IOLA 25 12 34 16 / 100 10 0 0 PARSONS-KPPF 30 14 37 19 / 100 10 0 0 && .ICT WATCHES/WARNINGS/ADVISORIES... WINTER WEATHER ADVISORY UNTIL 1 PM CST THIS AFTERNOON FOR KSZ068- 083-091-092. WINTER WEATHER ADVISORY UNTIL 6 PM CST THIS AFTERNOON FOR KSZ053- 069>072-093>096-098>100. && $$ ks AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WICHITA KS 744 AM CST SAT DEC 15 2007 .UPDATE... UPDATED TO INCREASE SNOWFALL AMOUNTS FOR THE 12-18Z TIME FRAME AS A BAND OF MODERATE SNOW HAS SET UP FROM NORTHERN KM COUNTY THROUGH MARION COUNTY. THIS BAND OF SNOW IS RELATED TO THE MAIN UPPER CIRCULATION THAT IS CURRENTLY TRACKING EAST ACROSS SOUTH CENTRAL KS. CROSS-SECTIONS OFF OF THE RUC ARE SHOWING IMPRESSIVE LIFT IN THE DENDRITIC ZONE WITH SURPRISINGLY DECENT INSTABILITY ABOVE 700MB. THIS WILL RESULT IN A CONTINUATION OF A MODERATE SNOW BAND THAT SHOULD SLIDE FAIRLY QUICKLY ACROSS THE FORECAST AREA. LOCATIONS AFFECTED BY THIS BAND SHOULD PICK UP AN ADDITIONAL 1-3 INCHES THROUGH NOON. LAWSON && .PREV DISCUSSION... /ISSUED 526 AM CST SAT DEC 15 2007/ AVIATION... FOR 12Z TAFS...MAIN AVIATION CONCERN WILL BE LOW CIGS AND VIS RESTRICTIONS DUE TO SNOW. THE ONLY SITES WHERE THERE IS HIGH CONFIDENCE OF IFR CONDITIONS ARE KCNU AND KSLN. KSLN WOULD BE MORE FOR THE SHORT TERM LOWER VIS DUE TO A BAND OF HEAVIER SNOWFALL MOVING OVER THEM. HOWEVER KCNU WILL BE BOUNCING IN AND OUT OF IFR CONDITIONS THROUGHOUT THE DAY AS THE SNOW SHOWERS LINGER LONGER OVER SE KS. WHILE LOW CLOUDS WILL BLANKET ALL SITES THROUGH AT LEAST 21Z...CONFIDENCE WAS ONLY HIGH ENOUGH TO PUT IFR CIGS IN A TEMPO GROUP FOR THE FIRST FEW HOURS(WITH THE EXCEPTION OF KCNU) WITH MVFR CIGS THE PREDOMINATE CLOUD HEIGHT. WHILE LIGHT SNOW WILL LINGER ACROSS CENTRAL AND SOUTH CENTRAL KS THROUGH AT LEAST NOON...IT SHOULD REMAIN LIGHT AND ONLY HAVE A MINIMAL AFFECT ON VIS. PREV DISCUSSION... /ISSUED 403 AM CST SAT DEC 15 2007/ AVIATION... 06Z TAFS...DRY SLOT IS MOVING INTO SOUTH CENTRAL KANSAS AT TAF ISSUANCE TIME...AND WILL KEEP PRECIPITATION LIGHT OR STOP IT ALTOGETHER FOR A TIME OVERNIGHT. SOUTHEAST KANSAS COULD SEE SOME INTERMITTENT FREEZING RAIN...BUT WILL CHANGE BACK TO SNOW BY MORNING. IFR TO LIFR CONDITIONS ARE EXPECTED FOR THE BULK OF THE TAF PERIOD. SNOW WILL INCREASE IN COVERAGE AND INTENSITY AGAIN SATURDAY MORNING AND WILL END DURING THE AFTERNOON HOURS FROM THE WEST. SCHRECK && .PRELIMINARY POINT TEMPS/POPS... WICHITA-KICT 27 12 36 17 / 100 0 0 0 HUTCHINSON 27 9 34 17 / 90 0 0 0 NEWTON 26 10 33 18 / 90 0 0 0 ELDORADO 27 11 34 18 / 80 10 0 0 WINFIELD-KWLD 29 14 37 18 / 90 0 0 0 RUSSELL 29 5 33 13 / 60 0 0 0 GREAT BEND 28 7 34 15 / 60 0 0 0 SALINA 29 8 34 12 / 90 0 0 0 MCPHERSON 28 9 33 16 / 90 0 0 0 COFFEYVILLE 32 15 38 19 / 100 10 0 0 CHANUTE 30 13 35 16 / 100 10 0 0 IOLA 27 12 34 16 / 100 10 0 0 PARSONS-KPPF 32 14 37 19 / 100 10 0 0 && .ICT WATCHES/WARNINGS/ADVISORIES... WINTER WEATHER ADVISORY UNTIL 6 PM CST THIS AFTERNOON FOR KSZ071- 072-094>096-098>100. HEAVY SNOW WARNING UNTIL NOON CST TODAY FOR KSZ032-033-047>052- 067-068-082. WINTER WEATHER ADVISORY UNTIL NOON CST TODAY FOR KSZ053-069-070- 083-091>093. && $$ ks AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PADUCAH KY 835 PM CST SUN DEC 16 2007 .UPDATE...TEMPS ARE FALLING OFF RATHER QUICKLY OVER THE SNOW COVERED GROUND IN SOUTHERN ILLINOIS. FORECAST UPDATED TO REFLECT THE EXCELLENT RADIATIONAL COOLING WHERE FRESH SNOW COVER...CLEAR SKY...AND CALM WINDS EXIST. 21Z RUC CAPTURED THE STRONG TEMP GRADIENT ALONG THE EDGE OF THE SNOW COVER...BUT IT APPEARS TO GO OVERBOARD WITH ITS 2 METER TEMPS IN THE SINGLE DIGITS ALONG INTERSTATE 64 BY 09Z. GENERALLY ADDED 10 DEGREES TO THE RUC IN THE FAR NORTH. NEAR SATURATED SURFACE LAYER SUGGESTS SOME FOG OR FROST WILL OCCUR AFTER MIDNIGHT. SOME POSSIBILITY OF HEAVY GROUND FROST...EVIDENCED AS BLACK ICE ON ROADWAYS...EXISTS OVER THE SNOW COVERED AREAS. && PREVIOUS DISCUSSION /ISSUED 117 PM CST SUN DEC 16 2007/... .DISCUSSION... CLOUDS CONTINUED TO DECREASE IN COVERAGE EARLY THIS AFTERNOON. SNOW LINE WAS SEEN FROM ROUGHLY JACKSON MISSOURI TO HARRISBURG ILLINOIS TO PETERSBURG INDIANA. A WEAK SURFACE RIDGE WILL MOVE ACROSS THE FA TONIGHT. WITH LITTLE CLOUD COVER AND WINDS BECOMING LIGHT EXPECT COLD TEMPS. WILL USE COLDEST GFS MOS AS A BASELINE AND THEN UNDERCUT THOSE VALUES BY 3-5 DEGREES ACROSS AREAS WITH LINGERING SNOW COVER. A FAIR AMOUNT OF SUN IS EXPECTED MONDAY WITH WEAK SW RETURN FLOW EXPECTED. THIS SHOULD ALLOW TEMPS TO BE SEVERAL DEGREES WARMER THAN WHAT WE HAVE SO FAR TODAY. QUIET WX IS EXPECTED AGAIN MONDAY NIGHT. A SLIGHTLY STRONGER SW FLOW IS EXPECTED TUE WITH INCREASED CLOUD COVER. BOTH THE NAM AND GFS ARE SHOWING SCANT QPF WITH A COUPLE OF VERY SUBTLE WAVES TUE-WED. RIGHT NOW...GUIDANCE POPS ARE RATHER LOW...AND THE MODELS AREN/T PRODUCING MUCH. SO WILL HOLD ON INTRODUCING ANY SLIGHT CHC POPS. SUBSEQUENT SHIFTS MAY HAVE TO EVENTUALLY ADD SOME POPS WITH TIME. THE FLOW PATTERN IN THE LONG TERM WILL BE QUASI-ZONAL AND RELATIVELY PROGRESSIVE. THE MODELS FORECAST THE SOUTHERN BRANCH OF THE JET WILL REMAIN ESTABLISHED ACROSS THE GULF COAST REGION (H3 80-100KT) WITH A SERIES OF DISTURBANCES AND ASSOCIATED MAXIMA MOVING ACROSS THE MID CONUS. THE FIRST WAVE IS FORECAST TO MOVE ACROSS THE FA WEDNESDAY NIGHT PER A CONSENSUS OF THE LONG RANGE MODELS...WHICH ARE IN FAIR AGREEMENT. THE GFS MAY BE A TAD OVERDONE WITH RESPECT TO THE SHARPNESS OF THE TROF. NEVER THE LESS...HAVE RAISED POPS WEDNESDAY NIGHT AND KEPT WITH A SMALL THUNDER CHANCE DUE TO FORECAST STEEPENING LAPSE RATES / ELEVATED INSTABILITY. ALSO KEPT TEMPS STEADY AND RAISED DEW POINTS IN ADVANCE OF THIS FEATURE. THE SYSTEM SHOULD PASS EAST ON THURSDAY WITH DIMINISHING POPS FROM WEST TO EAST. SOUNDINGS AND LOW LEVEL THERMAL PROFILE SUGGEST ALL LIQUID PRECIP. QUIET WX IS EXPECTED THURSDAY NIGHT INTO FRIDAY WITH WEAK HIGH PRESSURE AND RIDGING ALOFT THE RULE. BEGINNING FRIDAY NIGHT...THE MODELS START TO DIVERGE WITH RESPECT TO THEIR HANDLING OF A STRONGER UPPER TROF / LOW COMING EAST OUT OF THE ROCKIES AND SOUTHERN PLAINS. THE OPERATIONAL GFS IS SHOWING THE GREATEST INCONSISTENCY FROM RUN-TO-RUN SINCE 00Z WHILE A BLEND OF THE NCEP ENSEMBLE / ECMWF OPS ARE MORE CONSISTENT AND IN BETTER AGREEMENT. THEREFORE...WILL FOLLOW A BLEND OF THE LATTER SOLUTIONS...WHICH IS NOT TOO FAR OFF HPC/S DEPICTION...ALTHOUGH A TAD SLOWER. WILL INTRODUCE SMALL CHANCE POPS FRIDAY NIGHT...THEN UP POPS FOR SATURDAY INTO SATURDAY NIGHT AS THE UPPER SYSTEM AND ATTENDANT SURFACE LOW TRACK NE TOWARD THE OHIO VALLEY REGION. WILL MENTION ALL RAIN THROUGH 00Z SUNDAY...THEN MENTION A R-/S- POSSIBILITY SATURDAY NIGHT ACROSS THE WEST 1/2 OF THE FA AS COLDER AIR WORKS IN ON THE BACKSIDE OF THE SYSTEM. SUNDAY LOOKS LIKE A POTENTIALLY CHILLY DAY WITH A FEW LINGERING FLURRIES OR BRIEF LIGHT SNOW SHOWERS POSSIBLE...ESPECIALLY EARLY ON. CONFIDENCE IS NOT TOO HIGH FOR SUNDAY. BUT THERE IS SOME AGREEMENT AMONGST THE MODELS WITH RESPECT TO THIS POSSIBILITY. && .AVIATION... CLOUDS HAVE STEADILY MOVED EAST OF THE AREA TODAY AND AT THE SAME TIME...BECOMING MORE SCATTERED IN NATURE. HAD TO MENTION SOME BKN CIGS IN KPAH...KOWB AND KEVV TODAY BUT EXPECT SKIES TO BE PRETTY MUCH SKC OR FEW BY SUNSET. WINDS HAVE ALSO BEEN SUBSIDING AS THE LOW PRESSURE SYSTEM CONTINUES TO MOVE INTO THE NEW ENGLAND STATES. THEREFORE...WINDS WILL CONTINUE TO SUBSIDE THIS AFTERNOON FROM WEST TO EAST...AND BECOME LIGHT (5-6 KTS) MOST EVERYWHERE BY 00Z OR 01Z. CLEAR SKIES AND LIGHT WINDS PREVAIL ON MONDAY...WITH HIGH PRESSURE DOMINATING. && .PAH WATCHES/WARNINGS/ADVISORIES... KY...NONE. MO...NONE. IL...NONE. IN...NONE. && $$ UPDATE...MY PREVIOUS...CN ky AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LOUISVILLE KY 1204 PM EST SUN DEC 16 2007 .UPDATE... UPDATED TO AVIATION SECTION ONLY AT THIS TIME. .UPDATE (ISSUED 1049 AM EST SUN)... SURFACE LOW OVER NORTHEAST OHIO CONTINUES TO MOVE OFF TO THE NORTHEAST THIS MORNING WITH FLOW TO THE WEST AND SOUTH OF THE LOW SHIFTING MORE TOWARD THE WEST AS THE LOW PULLS AWAY. THIS IS LIMITING ANY AFFECTS OF LAKE MICHIGAN FOR THE CWA...WITH ANY LAKE ENHANCED PRECIPITATION ALREADY SHIFTING OFF INTO SOUTHWEST OHIO. IN ADDITION...UPSLOPE SHOWERS THAT APPEAR ON RADAR ARE VERY LIGHT AND NOT ACCUMULATING MUCH OTHER THAN A TENTH HERE AND THERE ON GRASSY SURFACES PER CONVERSATIONS WITH LOCAL LAW ENFORCEMENT AND VIEWING OF LOCAL WEB CAMERAS. WITH THE INTENSITY OF THE ONGOING UPSLOPE ACTIVITY REMAINING THE SAME AND DIMINISHING OVER THE COURSE OF THE LATE MORNING AND AFTERNOON HOURS...SIGNIFICANT SNOW ACCUMULATIONS NO LONGER A THREAT AND AM CANCELLING THE REMAINDER OF THE SNOW ADVISORY BY 11AM EST. WILL BACK OFF ON POPS FOR ALL AREAS TODAY AND TREND THE NORTHEASTERN ZONES DOWNWARD THIS AFTERNOON. WINDS STILL GUSTING AND SHOULD PICK UP A LITTLE MORE IN THE NEXT SEVERAL HOURS WITH VALUES HOVERING AROUND ADVISORY CRITERIA THROUGHOUT MUCH OF THE AFTERNOON. WILL REEVALUATE THE WIND ADVISORY END TIME WITH THE AFTERNOON ROUTINE FORECAST ISSUANCE. .UPDATE (ISSUED AT 855 AM SUN DEC 16)... SNOW NOT MATERIALIZING AS EXPECTED AND AM GOING TO BEGIN CANCELLING PORTIONS OF THE WINTER WEATHER ADVISORY. AM LEAVING IN THE COUNTIES IN A LINE FROM MADISON COUNTY KENTUCKY NORTHWEST THROUGH CLARK AND SCOTT COUNTIES IN INDIANA...REMOVING ALL POINTS SOUTH AND WEST OF THERE INCLUDING LOUISVILLE. SOME LIGHT SNOW MAY OCCUR FROM TIME TO TIME IN THE AREAS BEING REMOVED FROM THE ADVISORY...BUT A DUSTING WOULD LIKELY BE THE ONLY ACCUMULATION. CONCERNING THE AREAS BEING LEFT IN THE ADVISORY...STRONG WAVE ENERGY ON THE BACK SIDE OF THE LOW PRESSURE SYSTEM JUST NOW MOVING OVER THE WESTERN HALF OF LAKE MICHIGAN RESULTING IN SOME SNOW ENHANCEMENT OVER CENTRAL INDIANA. THIS AREA OF ENHANCED SHOWERS COULD CLIP THE NORTHEAST ZONES AND COMBINE WITH FAVORABLE NORTHWEST UPSLOPE FLOW OVER THE NEXT COUPLE OF HOURS TO CREATE ACCUMULATIONS OF AN INCH OR MORE AND WILL LEAVE ADVISORY UP FOR A WHILE UNTIL THESE SHOWERS EVOLVE A LITTLE. REMAINDER OF FORECAST ON TRACK...INCLUDING WINDS WITH GUSTS OVER 30 MPH CONTINUING AND SOME INCREASE IN THOSE GUSTS TO OVER 40 MPH EXPECTED STILL BY LATE THIS MORNING. && .SHORT TERM (TODAY AND TONIGHT)... 830Z METAR OBSERVATIONS SHOWING SFC LOW NEAR THE IN/OH/KY BORDER. ASSOCIATED WRAP AROUND MOISTURE ALONG THE BACK SIDE OF THE LOW OVER IL STRETCHING INTO WRN IN/KY. THIS MOISTURE IS MOSTLY IN THE FORM OF SNOW AS COLD AIR IS QUICKLY MOVING INTO THE AREA. EXPECT CURRENT LIGHT RAIN AND DRIZZLE OVER CWA TO QUICKLY TRANSITION TO SNOW IN THE NEXT COUPLE OF HOURS. SUSPECT THAT PRECIP HAS ALREADY MADE THIS TRANSITION IN DUBOIS AND ORANGE COUNTIES IN INDIANA. RUC40 SEEMS TO HAVE A GOOD HANDLE ON THIS TRANSITION FOLLOWING 1000-700MB THICKNESS VALUE OF 2840. BY THIS GUIDANCE...PRECIP SHOULD BE ALL SNOW BY 12Z ACROSS ENTIRE CWA. RH VALUES OF THE GFS AND ETA DOING A PRETTY GOOD JOB TRACKING PRECIP FIELD. BEST DEEP LAYER MOISTURE AND SYNOPTIC FORCING TO MOVE NE ALONG THE OHIO RIVER THIS MORNING...AND TO A LESSER EXTENT OVER THE BLUEGRASS EARLY THIS AFTERNOON. WITH AIR COLUMN COLD ENOUGH FOR AN ALL SNOW EVENT...WENT WITH A SNOW ADVISORY NORTH OF A LINE FROM OHIO COUNTY TO NELSON COUNTY TO MADISON COUNTY KY. THERE MAY BE A TRANSITION OF ICE PELLETS FOR A BRIEF TIME DURING THE PRECIP CHANGE OVER...BUT MOSTLY A SNOW EVENT. EXPECT GENERAL SNOW ACCUMULATIONS OF 2 TO 3 INCHES ALONG NORTH OF THE OH RIVER...1 TO 2 INCHES IN THE REST OF THE ADVISORY AREA...AND LITTLE TO NO ACCUMULATION OVER SOUTH CENTRAL KY. PRECIP SHOULD DECREASE IN INTENSITY FROM SW TO NE THIS AFTERNOON WITH LINGERING FLURRIES POSSIBLE TONIGHT. THE OTHER MAIN ISSUE IN THE SHORT TERM IS STRONG WINDS CAUSED BY THE TIGHT PRESSURE GRADIENT ALONG THE BACK SIDE OF SFC LOW. BUFKIT DATA INDICATING 20 TO 30 MPH WITH GUSTS UP TO 45 MPH WHICH MEET WIND ADVISORY CRITERIA. SOME LOCATIONS OVER FA ALREADY GUSTING TO AROUND 40 MPH SO WILL START THE WIND ADY WITH THE 4AM FORECAST PACKAGE AND RUN IT THROUGH 0Z TONIGHT. EXPECT THE STRONGEST WINDS THIS MORNING AND EARLY AFTERNOON AS THE LOW PRESSURE SYSTEM WILL BE CLOSER TO FA. STRONG WINDS COMBINED WITH LIGHT SNOW SHOWERS THIS MORNING/AFTERNOON WILL MAKE FOR HAZARDOUS TRAVEL CONDITIONS SO MOTORISTS SHOULD BE CAUTIOUS. AS FOR TEMPS...THEY SHOULD SLOWLY FALL THROUGHOUT THE DAY FROM THE LOW 30S INTO THE UPPER 20S. AS SKIES BEGIN TO CLEAR SOMEWHAT TONIGHT...RADIATIONAL COOLING AND COLD AIR ON THE BACK SIDE OF LOW PRESSURE SYSTEM WILL ALLOW LOWS TO DIP INTO THE UPPER TEENS AND LOW 20S. .LONG TERM (MONDAY THROUGH SATURDAY)... LOOKING AG THE AO AND PNA TELECONNECTIONS...NOTHING DEFINITIVE TO GO WITH. THE ENSEMBLE DATA AND THE ECMWF/GFS MODELS INDICATE A SERIES OF TROUGHS BEING SPUN OFF BY THE NEGATIVE HEIGHT ANOMALY OVER THE GULF OF ALASKA INTO THE WESTERN CONUS. THESE SHORT WAVES THEN MOVING GENERALLY EWD ACROSS THE CENTRAL AND NRN U.S.. NO REALLY MAJOR COLD OUTBREAK IN SIGHT. MEAN 500 MB HEIGHTS THIS PERIOD RELATIVELY WARM. COUPLE THIS WITH A MORE ZONAL WEST TO EAST STORM TRACK...THIS WOULD INDICATE TEMPS TRENDING ABOVE NORMAL FOR THE LONG TERM PERIOD AFTER TUESDAY. ALSO WITH EACH TROUGH WE HAVE THE RISK OF SOME SHOWER ACTIVITY BUT NOT MUCH CHANCE OF ANY FROZEN PRECIP. MADE SOME CONSISTENCY AND SMOOTHING ADJUSTMENTS TO THE CURRENT LONG TERM PACKAGE BUT NOTHING REALLY MAJOR. && .AVIATION (18Z TAFS)... MVFR CEILINGS TO CONTINUE DURING THE FEW HOURS OF THE TAF PERIOD BEFORE SKIES BEGIN TO CLEAR FROM NORTHWEST TO SOUTHEAST OVERNIGHT. KSDF SHOULD SEE CEILINGS IMPROVE BY 21Z OR SO WITH KLEX AND KBWG SEEING MVFR CEILINGS THROUGH AROUND 03Z. SOME MINOR REDUCTIONS IN VISIBILITY MAY OCCUR AT TIMES ACROSS THE ENTIRE AREA IN LIGHT SNOW SHOWERS UNTIL SKIES BEGIN TO CLEAR OUT...BUT SNOW SHOWER ACTIVITY WILL BE ISOLATED AT BEST. GUSTY SURFACE WINDS OF 20 TO 30 KTS WITH SOME HIGHER GUSTS TO PERSIST AT ALL TAF LOCATIONS DURING THE EARLY PART OF THE TAF PERIOD...WITH DECREASING WIND SPEEDS FROM SOUTH TO NORTH BEGINNING AROUND 20Z OR SO AT KBWG AND AFTER 23Z AT KSDF AND KLEX. SKIES SHOULD REMAIN MOSTLY CLEAR THROUGH MUCH OF TONIGHT THOUGH A LOW STRATUS DECK SHOULD BEGIN TO APPROACH WESTERN AND NORTHERN KENTUCKY AFTER 12Z. AT THIS TIME IT APPEARS THIS DECK SHOULD SLOWLY MOVE BETWEEN 12Z AND 18Z...BUT TIMING IS UNCERTAIN AND COULD MOVE IN SOONER OR JUST AFTER 18Z. && .LMK WATCHES/WARNINGS/ADVISORIES... KY...WIND ADVISORY UNTIL 7PM EST / 6PM CST THIS EVENING FOR ALL OF CENTRAL KENTUCKY. IN...WIND ADVISORY UNTIL 7PM EST / 6PM CST FOR ALL OF SOUTH CENTRAL INDIANA. && $$ UPDATES......MACZKO SHORT TERM...AML LONG TERM....AB AVIATION.....AML ky AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LOUISVILLE KY 1049 AM EST SUN DEC 16 2007 .UPDATE... SURFACE LOW OVER NORTHEAST OHIO CONTINUES TO MOVE OFF TO THE NORTHEAST THIS MORNING WITH FLOW TO THE WEST AND SOUTH OF THE LOW SHIFTING MORE TOWARD THE WEST AS THE LOW PULLS AWAY. THIS IS LIMITING ANY AFFECTS OF LAKE MICHIGAN FOR THE CWA...WITH ANY LAKE ENHANCED PRECIPITATION ALREADY SHIFTING OFF INTO SOUTHWEST OHIO. IN ADDITION...UPSLOPE SHOWERS THAT APPEAR ON RADAR ARE VERY LIGHT AND NOT ACCUMULATING MUCH OTHER THAN A TENTH HERE AND THERE ON GRASSY SURFACES PER CONVERSATIONS WITH LOCAL LAW ENFORCEMENT AND VIEWING OF LOCAL WEB CAMERAS. WITH THE INTENSITY OF THE ONGOING UPSLOPE ACTIVITY REMAINING THE SAME AND DIMINISHING OVER THE COURSE OF THE LATE MORNING AND AFTERNOON HOURS...SIGNIFICANT SNOW ACCUMULATIONS NO LONGER A THREAT AND AM CANCELLING THE REMAINDER OF THE SNOW ADVISORY BY 11AM EST. WILL BACK OFF ON POPS FOR ALL AREAS TODAY AND TREND THE NORTHEASTERN ZONES DOWNWARD THIS AFTERNOON. WINDS STILL GUSTING AND SHOULD PICK UP A LITTLE MORE IN THE NEXT SEVERAL HOURS WITH VALUES HOVERING AROUND ADVISORY CRITERIA THROUGHOUT MUCH OF THE AFTERNOON. WILL REEVALUATE THE WIND ADVISORY END TIME WITH THE AFTERNOON ROUTINE FORECAST ISSUANCE. .UPDATE (ISSUED AT 855 AM SUN DEC 16)... SNOW NOT MATERIALIZING AS EXPECTED AND AM GOING TO BEGIN CANCELLING PORTIONS OF THE WINTER WEATHER ADVISORY. AM LEAVING IN THE COUNTIES IN A LINE FROM MADISON COUNTY KENTUCKY NORTHWEST THROUGH CLARK AND SCOTT COUNTIES IN INDIANA...REMOVING ALL POINTS SOUTH AND WEST OF THERE INCLUDING LOUISVILLE. SOME LIGHT SNOW MAY OCCUR FROM TIME TO TIME IN THE AREAS BEING REMOVED FROM THE ADVISORY...BUT A DUSTING WOULD LIKELY BE THE ONLY ACCUMULATION. CONCERNING THE AREAS BEING LEFT IN THE ADVISORY...STRONG WAVE ENERGY ON THE BACK SIDE OF THE LOW PRESSURE SYSTEM JUST NOW MOVING OVER THE WESTERN HALF OF LAKE MICHIGAN RESULTING IN SOME SNOW ENHANCEMENT OVER CENTRAL INDIANA. THIS AREA OF ENHANCED SHOWERS COULD CLIP THE NORTHEAST ZONES AND COMBINE WITH FAVORABLE NORTHWEST UPSLOPE FLOW OVER THE NEXT COUPLE OF HOURS TO CREATE ACCUMULATIONS OF AN INCH OR MORE AND WILL LEAVE ADVISORY UP FOR A WHILE UNTIL THESE SHOWERS EVOLVE A LITTLE. REMAINDER OF FORECAST ON TRACK...INCLUDING WINDS WITH GUSTS OVER 30 MPH CONTINUING AND SOME INCREASE IN THOSE GUSTS TO OVER 40 MPH EXPECTED STILL BY LATE THIS MORNING. && .SHORT TERM (TODAY AND TONIGHT)... 830Z METAR OBSERVATIONS SHOWING SFC LOW NEAR THE IN/OH/KY BORDER. ASSOCIATED WRAP AROUND MOISTURE ALONG THE BACK SIDE OF THE LOW OVER IL STRETCHING INTO WRN IN/KY. THIS MOISTURE IS MOSTLY IN THE FORM OF SNOW AS COLD AIR IS QUICKLY MOVING INTO THE AREA. EXPECT CURRENT LIGHT RAIN AND DRIZZLE OVER CWA TO QUICKLY TRANSITION TO SNOW IN THE NEXT COUPLE OF HOURS. SUSPECT THAT PRECIP HAS ALREADY MADE THIS TRANSITION IN DUBOIS AND ORANGE COUNTIES IN INDIANA. RUC40 SEEMS TO HAVE A GOOD HANDLE ON THIS TRANSITION FOLLOWING 1000-700MB THICKNESS VALUE OF 2840. BY THIS GUIDANCE...PRECIP SHOULD BE ALL SNOW BY 12Z ACROSS ENTIRE CWA. RH VALUES OF THE GFS AND ETA DOING A PRETTY GOOD JOB TRACKING PRECIP FIELD. BEST DEEP LAYER MOISTURE AND SYNOPTIC FORCING TO MOVE NE ALONG THE OHIO RIVER THIS MORNING...AND TO A LESSER EXTENT OVER THE BLUEGRASS EARLY THIS AFTERNOON. WITH AIR COLUMN COLD ENOUGH FOR AN ALL SNOW EVENT...WENT WITH A SNOW ADVISORY NORTH OF A LINE FROM OHIO COUNTY TO NELSON COUNTY TO MADISON COUNTY KY. THERE MAY BE A TRANSITION OF ICE PELLETS FOR A BRIEF TIME DURING THE PRECIP CHANGE OVER...BUT MOSTLY A SNOW EVENT. EXPECT GENERAL SNOW ACCUMULATIONS OF 2 TO 3 INCHES ALONG NORTH OF THE OH RIVER...1 TO 2 INCHES IN THE REST OF THE ADVISORY AREA...AND LITTLE TO NO ACCUMULATION OVER SOUTH CENTRAL KY. PRECIP SHOULD DECREASE IN INTENSITY FROM SW TO NE THIS AFTERNOON WITH LINGERING FLURRIES POSSIBLE TONIGHT. THE OTHER MAIN ISSUE IN THE SHORT TERM IS STRONG WINDS CAUSED BY THE TIGHT PRESSURE GRADIENT ALONG THE BACK SIDE OF SFC LOW. BUFKIT DATA INDICATING 20 TO 30 MPH WITH GUSTS UP TO 45 MPH WHICH MEET WIND ADVISORY CRITERIA. SOME LOCATIONS OVER FA ALREADY GUSTING TO AROUND 40 MPH SO WILL START THE WIND ADY WITH THE 4AM FORECAST PACKAGE AND RUN IT THROUGH 0Z TONIGHT. EXPECT THE STRONGEST WINDS THIS MORNING AND EARLY AFTERNOON AS THE LOW PRESSURE SYSTEM WILL BE CLOSER TO FA. STRONG WINDS COMBINED WITH LIGHT SNOW SHOWERS THIS MORNING/AFTERNOON WILL MAKE FOR HAZARDOUS TRAVEL CONDITIONS SO MOTORISTS SHOULD BE CAUTIOUS. AS FOR TEMPS...THEY SHOULD SLOWLY FALL THROUGHOUT THE DAY FROM THE LOW 30S INTO THE UPPER 20S. AS SKIES BEGIN TO CLEAR SOMEWHAT TONIGHT...RADIATIONAL COOLING AND COLD AIR ON THE BACK SIDE OF LOW PRESSURE SYSTEM WILL ALLOW LOWS TO DIP INTO THE UPPER TEENS AND LOW 20S. .LONG TERM (MONDAY THROUGH SATURDAY)... LOOKING AG THE AO AND PNA TELECONNECTIONS...NOTHING DEFINITIVE TO GO WITH. THE ENSEMBLE DATA AND THE ECMWF/GFS MODELS INDICATE A SERIES OF TROUGHS BEING SPUN OFF BY THE NEGATIVE HEIGHT ANOMALY OVER THE GULF OF ALASKA INTO THE WESTERN CONUS. THESE SHORT WAVES THEN MOVING GENERALLY EWD ACROSS THE CENTRAL AND NRN U.S.. NO REALLY MAJOR COLD OUTBREAK IN SIGHT. MEAN 500 MB HEIGHTS THIS PERIOD RELATIVELY WARM. COUPLE THIS WITH A MORE ZONAL WEST TO EAST STORM TRACK...THIS WOULD INDICATE TEMPS TRENDING ABOVE NORMAL FOR THE LONG TERM PERIOD AFTER TUESDAY. ALSO WITH EACH TROUGH WE HAVE THE RISK OF SOME SHOWER ACTIVITY BUT NOT MUCH CHANCE OF ANY FROZEN PRECIP. MADE SOME CONSISTENCY AND SMOOTHING ADJUSTMENTS TO THE CURRENT LONG TERM PACKAGE BUT NOTHING REALLY MAJOR. && .AVIATION (12Z TAFS)... LIGHT SNOW OVER SDF AND LEX TERMINALS THIS MORNING WILL CONTINUE THROUGH THE EARLIER AFTERNOON HOURS. THERE MAY BE SOME LINGERING FLURRIES AFTER 17-18Z...BUT WILL NOT WARRANT A TAF MENTION FOR NOW. BWG LOOKS TO BE CLEAR OF THESE LIGHT SNOW SHOWERS THIS MORNING AS PRECIP ON THE BACK SIDE OF SFC LOW REMAINS N OF THIS TERMINAL. MVFR VSBYS AND CIGS THIS MORNING WILL IMPROVE TO VFR FIRST AT BWG AND THEN AT SDF AND LEX THIS AFTERNOON/EVENING. WINDS WILL BE A CONCERN TODAY TOO AS GUSTS HAVE ALREADY REACHED 35 TO 40 MPH THIS MORNING AT THE TAF SITES. EXPECT THESE STRONG WINDS TO CONTINUE THROUGH THE AFTERNOON UNDER TIGHT PRESSURE GRADIENT. NEXT POTENTIAL PROBLEM COULD BE SOME STRATUS WORKING IN TOWARD TOMORROW MORNING AND WILL NEED TO INVESTIGATE THIS FOR LATER TAF ISSUANCES TODAY. && .LMK WATCHES/WARNINGS/ADVISORIES... KY...WIND ADVISORY UNTIL 7PM EST / 6PM CST THIS EVENING FOR ALL OF CENTRAL KENTUCKY. IN...WIND ADVISORY UNTIL 7PM EST / 6PM CST FOR ALL OF SOUTH CENTRAL INDIANA. && $$ UPDATES......MACZKO SHORT TERM...AML LONG TERM....AB AVIATION.....AML ky AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LOUISVILLE KY 855 AM EST SUN DEC 16 2007 .UPDATE... SNOW NOT MATERIALIZING AS EXPECTED AND AM GOING TO BEGIN CANCELLING PORTIONS OF THE WINTER WEATHER ADVISORY. AM LEAVING IN THE COUNTIES IN A LINE FROM MADISON COUNTY KENTUCKY NORTHWEST THROUGH CLARK AND SCOTT COUNTIES IN INDIANA...REMOVING ALL POINTS SOUTH AND WEST OF THERE INCLUDING LOUISVILLE. SOME LIGHT SNOW MAY OCCUR FROM TIME TO TIME IN THE AREAS BEING REMOVED FROM THE ADVISORY...BUT A DUSTING WOULD LIKELY BE THE ONLY ACCUMULATION. CONCERNING THE AREAS BEING LEFT IN THE ADVISORY...STRONG WAVE ENERGY ON THE BACK SIDE OF THE LOW PRESSURE SYSTEM JUST NOW MOVING OVER THE WESTERN HALF OF LAKE MICHIGAN RESULTING IN SOME SNOW ENHANCEMENT OVER CENTRAL INDIANA. THIS AREA OF ENHANCED SHOWERS COULD CLIP THE NORTHEAST ZONES AND COMBINE WITH FAVORABLE NORTHWEST UPSLOPE FLOW OVER THE NEXT COUPLE OF HOURS TO CREATE ACCUMULATIONS OF AN INCH OR MORE AND WILL LEAVE ADVISORY UP FOR A WHILE UNTIL THESE SHOWERS EVOLVE A LITTLE. REMAINDER OF FORECAST ON TRACK...INCLUDING WINDS WITH GUSTS OVER 30 MPH CONTINUING AND SOME INCREASE IN THOSE GUSTS TO OVER 40 MPH EXPECTED STILL BY LATE THIS MORNING. && .SHORT TERM (TODAY AND TONIGHT)... 830Z METAR OBSERVATIONS SHOWING SFC LOW NEAR THE IN/OH/KY BORDER. ASSOCIATED WRAP AROUND MOISTURE ALONG THE BACK SIDE OF THE LOW OVER IL STRETCHING INTO WRN IN/KY. THIS MOISTURE IS MOSTLY IN THE FORM OF SNOW AS COLD AIR IS QUICKLY MOVING INTO THE AREA. EXPECT CURRENT LIGHT RAIN AND DRIZZLE OVER CWA TO QUICKLY TRANSITION TO SNOW IN THE NEXT COUPLE OF HOURS. SUSPECT THAT PRECIP HAS ALREADY MADE THIS TRANSITION IN DUBOIS AND ORANGE COUNTIES IN INDIANA. RUC40 SEEMS TO HAVE A GOOD HANDLE ON THIS TRANSITION FOLLOWING 1000-700MB THICKNESS VALUE OF 2840. BY THIS GUIDANCE...PRECIP SHOULD BE ALL SNOW BY 12Z ACROSS ENTIRE CWA. RH VALUES OF THE GFS AND ETA DOING A PRETTY GOOD JOB TRACKING PRECIP FIELD. BEST DEEP LAYER MOISTURE AND SYNOPTIC FORCING TO MOVE NE ALONG THE OHIO RIVER THIS MORNING...AND TO A LESSER EXTENT OVER THE BLUEGRASS EARLY THIS AFTERNOON. WITH AIR COLUMN COLD ENOUGH FOR AN ALL SNOW EVENT...WENT WITH A SNOW ADVISORY NORTH OF A LINE FROM OHIO COUNTY TO NELSON COUNTY TO MADISON COUNTY KY. THERE MAY BE A TRANSITION OF ICE PELLETS FOR A BRIEF TIME DURING THE PRECIP CHANGE OVER...BUT MOSTLY A SNOW EVENT. EXPECT GENERAL SNOW ACCUMULATIONS OF 2 TO 3 INCHES ALONG NORTH OF THE OH RIVER...1 TO 2 INCHES IN THE REST OF THE ADVISORY AREA...AND LITTLE TO NO ACCUMULATION OVER SOUTH CENTRAL KY. PRECIP SHOULD DECREASE IN INTENSITY FROM SW TO NE THIS AFTERNOON WITH LINGERING FLURRIES POSSIBLE TONIGHT. THE OTHER MAIN ISSUE IN THE SHORT TERM IS STRONG WINDS CAUSED BY THE TIGHT PRESSURE GRADIENT ALONG THE BACK SIDE OF SFC LOW. BUFKIT DATA INDICATING 20 TO 30 MPH WITH GUSTS UP TO 45 MPH WHICH MEET WIND ADVISORY CRITERIA. SOME LOCATIONS OVER FA ALREADY GUSTING TO AROUND 40 MPH SO WILL START THE WIND ADY WITH THE 4AM FORECAST PACKAGE AND RUN IT THROUGH 0Z TONIGHT. EXPECT THE STRONGEST WINDS THIS MORNING AND EARLY AFTERNOON AS THE LOW PRESSURE SYSTEM WILL BE CLOSER TO FA. STRONG WINDS COMBINED WITH LIGHT SNOW SHOWERS THIS MORNING/AFTERNOON WILL MAKE FOR HAZARDOUS TRAVEL CONDITIONS SO MOTORISTS SHOULD BE CAUTIOUS. AS FOR TEMPS...THEY SHOULD SLOWLY FALL THROUGHOUT THE DAY FROM THE LOW 30S INTO THE UPPER 20S. AS SKIES BEGIN TO CLEAR SOMEWHAT TONIGHT...RADIATIONAL COOLING AND COLD AIR ON THE BACK SIDE OF LOW PRESSURE SYSTEM WILL ALLOW LOWS TO DIP INTO THE UPPER TEENS AND LOW 20S. .LONG TERM (MONDAY THROUGH SATURDAY)... LOOKING AG THE AO AND PNA TELECONNECTIONS...NOTHING DEFINITIVE TO GO WITH. THE ENSEMBLE DATA AND THE ECMWF/GFS MODELS INDICATE A SERIES OF TROUGHS BEING SPUN OFF BY THE NEGATIVE HEIGHT ANOMALY OVER THE GULF OF ALASKA INTO THE WESTERN CONUS. THESE SHORT WAVES THEN MOVING GENERALLY EWD ACROSS THE CENTRAL AND NRN U.S.. NO REALLY MAJOR COLD OUTBREAK IN SIGHT. MEAN 500 MB HEIGHTS THIS PERIOD RELATIVELY WARM. COUPLE THIS WITH A MORE ZONAL WEST TO EAST STORM TRACK...THIS WOULD INDICATE TEMPS TRENDING ABOVE NORMAL FOR THE LONG TERM PERIOD AFTER TUESDAY. ALSO WITH EACH TROUGH WE HAVE THE RISK OF SOME SHOWER ACTIVITY BUT NOT MUCH CHANCE OF ANY FROZEN PRECIP. MADE SOME CONSISTENCY AND SMOOTHING ADJUSTMENTS TO THE CURRENT LONG TERM PACKAGE BUT NOTHING REALLY MAJOR. && .AVIATION (12Z TAFS)... LIGHT SNOW OVER SDF AND LEX TERMINALS THIS MORNING WILL CONTINUE THROUGH THE EARLIER AFTERNOON HOURS. THERE MAY BE SOME LINGERING FLURRIES AFTER 17-18Z...BUT WILL NOT WARRANT A TAF MENTION FOR NOW. BWG LOOKS TO BE CLEAR OF THESE LIGHT SNOW SHOWERS THIS MORNING AS PRECIP ON THE BACK SIDE OF SFC LOW REMAINS N OF THIS TERMINAL. MVFR VSBYS AND CIGS THIS MORNING WILL IMPROVE TO VFR FIRST AT BWG AND THEN AT SDF AND LEX THIS AFTERNOON/EVENING. WINDS WILL BE A CONCERN TODAY TOO AS GUSTS HAVE ALREADY REACHED 35 TO 40 MPH THIS MORNING AT THE TAF SITES. EXPECT THESE STRONG WINDS TO CONTINUE THROUGH THE AFTERNOON UNDER TIGHT PRESSURE GRADIENT. NEXT POTENTIAL PROBLEM COULD BE SOME STRATUS WORKING IN TOWARD TOMORROW MORNING AND WILL NEED TO INVESTIGATE THIS FOR LATER TAF ISSUANCES TODAY. && .LMK WATCHES/WARNINGS/ADVISORIES... KY...WIND ADVISORY UNTIL 7PM EST / 6PM CST THIS EVENING FOR ALL OF CENTRAL KENTUCKY. SNOW ADVISORY UNTIL 1 PM EST FOR PORTIONS OF CENTRAL KENTUCKY. IN...WIND ADVISORY UNTIL 7PM EST / 6PM CST FOR ALL OF SOUTH CENTRAL INDIANA. SNOW ADVISORY UNTIL 1PM EST FOR PORTIONS OF SOUTH CENTRAL INDIANA. && $$ UPDATE.......MACZKO SHORT TERM...AML LONG TERM....AB AVIATION.....AML ky AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LOUISVILLE KY 621 AM EST SUN DEC 16 2007 .SHORT TERM (TODAY AND TONIGHT). 830Z METAR OBSERVATIONS SHOWING SFC LOW NEAR THE IN/OH/KY BORDER. ASSOCIATED WRAP AROUND MOISTURE ALONG THE BACK SIDE OF THE LOW OVER IL STRETCHING INTO WRN IN/KY. THIS MOISTURE IS MOSTLY IN THE FORM OF SNOW AS COLD AIR IS QUICKLY MOVING INTO THE AREA. EXPECT CURRENT LIGHT RAIN AND DRIZZLE OVER CWA TO QUICKLY TRANSITION TO SNOW IN THE NEXT COUPLE OF HOURS. SUSPECT THAT PRECIP HAS ALREADY MADE THIS TRANSITION IN DUBOIS AND ORANGE COUNTIES IN INDIANA. RUC40 SEEMS TO HAVE A GOOD HANDLE ON THIS TRANSITION FOLLOWING 1000-700MB THICKNESS VALUE OF 2840. BY THIS GUIDANCE...PRECIP SHOULD BE ALL SNOW BY 12Z ACROSS ENTIRE CWA. RH VALUES OF THE GFS AND ETA DOING A PRETTY GOOD JOB TRACKING PRECIP FIELD. BEST DEEP LAYER MOISTURE AND SYNOPTIC FORCING TO MOVE NE ALONG THE OHIO RIVER THIS MORNING...AND TO A LESSER EXTENT OVER THE BLUEGRASS EARLY THIS AFTERNOON. WITH AIR COLUMN COLD ENOUGH FOR AN ALL SNOW EVENT...WENT WITH A SNOW ADVISORY NORTH OF A LINE FROM OHIO COUNTY TO NELSON COUNTY TO MADISON COUNTY KY. THERE MAY BE A TRANSITION OF ICE PELLETS FOR A BRIEF TIME DURING THE PRECIP CHANGE OVER...BUT MOSTLY A SNOW EVENT. EXPECT GENERAL SNOW ACCUMULATIONS OF 2 TO 3 INCHES ALONG NORTH OF THE OH RIVER...1 TO 2 INCHES IN THE REST OF THE ADVISORY AREA...AND LITTLE TO NO ACCUMULATION OVER SOUTH CENTRAL KY. PRECIP SHOULD DECREASE IN INTENSITY FROM SW TO NE THIS AFTERNOON WITH LINGERING FLURRIES POSSIBLE TONIGHT. THE OTHER MAIN ISSUE IN THE SHORT TERM IS STRONG WINDS CAUSED BY THE TIGHT PRESSURE GRADIENT ALONG THE BACK SIDE OF SFC LOW. BUFKIT DATA INDICATING 20 TO 30 MPH WITH GUSTS UP TO 45 MPH WHICH MEET WIND ADVISORY CRITERIA. SOME LOCATIONS OVER FA ALREADY GUSTING TO AROUND 40 MPH SO WILL START THE WIND ADY WITH THE 4AM FORECAST PACKAGE AND RUN IT THROUGH 0Z TONIGHT. EXPECT THE STRONGEST WINDS THIS MORNING AND EARLY AFTERNOON AS THE LOW PRESSURE SYSTEM WILL BE CLOSER TO FA. STRONG WINDS COMBINED WITH LIGHT SNOW SHOWERS THIS MORNING/AFTERNOON WILL MAKE FOR HAZARDOUS TRAVEL CONDITIONS SO MOTORISTS SHOULD BE CAUTIOUS. AS FOR TEMPS...THEY SHOULD SLOWLY FALL THROUGHOUT THE DAY FROM THE LOW 30S INTO THE UPPER 20S. AS SKIES BEGIN TO CLEAR SOMEWHAT TONIGHT...RADIATIONAL COOLING AND COLD AIR ON THE BACK SIDE OF LOW PRESSURE SYSTEM WILL ALLOW LOWS TO DIP INTO THE UPPER TEENS AND LOW 20S. && .LONG TERM (MONDAY THROUGH SATURDAY). LOOKING AG THE AO AND PNA TELECONNECTIONS...NOTHING DEFINITIVE TO GO WITH. THE ENSEMBLE DATA AND THE ECMWF/GFS MODELS INDICATE A SERIES OF TROUGHS BEING SPUN OFF BY THE NEGATIVE HEIGHT ANOMALY OVER THE GULF OF ALASKA INTO THE WESTERN CONUS. THESE SHORT WAVES THEN MOVING GENERALLY EWD ACROSS THE CENTRAL AND NRN U.S.. NO REALLY MAJOR COLD OUTBREAK IN SIGHT. MEAN 500 MB HEIGHTS THIS PERIOD RELATIVELY WARM. COUPLE THIS WITH A MORE ZONAL WEST TO EAST STORM TRACK...THIS WOULD INDICATE TEMPS TRENDING ABOVE NORMAL FOR THE LONG TERM PERIOD AFTER TUESDAY. ALSO WITH EACH TROUGH WE HAVE THE RISK OF SOME SHOWER ACTIVITY BUT NOT MUCH CHANCE OF ANY FROZEN PRECIP. MADE SOME CONSISTENCY AND SMOOTHING ADJUSTMENTS TO THE CURRENT LONG TERM PACKAGE BUT NOTHING REALLY MAJOR. && .AVIATION (12Z TAFS)... LIGHT SNOW OVER SDF AND LEX TERMINALS THIS MORNING WILL CONTINUE THROUGH THE EARLIER AFTERNOON HOURS. THERE MAY BE SOME LINGERING FLURRIES AFTER 17-18Z...BUT WILL NOT WARRANT A TAF MENTION FOR NOW. BWG LOOKS TO BE CLEAR OF THESE LIGHT SNOW SHOWERS THIS MORNING AS PRECIP ON THE BACK SIDE OF SFC LOW REMAINS N OF THIS TERMINAL. MVFR VSBYS AND CIGS THIS MORNING WILL IMPROVE TO VFR FIRST AT BWG AND THEN AT SDF AND LEX THIS AFTERNOON/EVENING. WINDS WILL BE A CONCERN TODAY TOO AS GUSTS HAVE ALREADY REACHED 35 TO 40 MPH THIS MORNING AT THE TAF SITES. EXPECT THESE STRONG WINDS TO CONTINUE THROUGH THE AFTERNOON UNDER TIGHT PRESSURE GRADIENT. NEXT POTENTIAL PROBLEM COULD BE SOME STRATUS WORKING IN TOWARD TOMORROW MORNING AND WILL NEED TO INVESTIGATE THIS FOR LATER TAF ISSUANCES TODAY. && .LMK WATCHES/WARNINGS/ADVISORIES... KY...WIND ADVISORY FROM 4 AM EST /3 AM CST/ THIS MORNING TO 7 PM EST /6 PM CST/ THIS EVENING FOR KYZ023>043-045>049-053>057- 061>067-070>078-081-082. SNOW ADVISORY UNTIL 1 PM EST /NOON CST/ THIS AFTERNOON FOR KYZ023>043-045>049-055>057. IN...WIND ADVISORY FROM 4 AM EST /3 AM CST/ THIS MORNING TO 7 PM EST /6 PM CST/ THIS EVENING FOR INZ076>079-083-084-089>092. SNOW ADVISORY UNTIL 1 PM EST /NOON CST/ THIS AFTERNOON FOR INZ076>079-083-084-089>092. && $$ SHORT TERM...AML LONG TERM....AB AVIATION...AML ky AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PADUCAH KY 213 PM CST SAT DEC 15 2007 .DISCUSSION... BACK EDGE OF THE HEAVIER RAIN WAS FROM THE OHIO AND WABASH RIVER EASTWARD...AND CONTINUED TO HEAD EAST EARLY THIS AFTERNOON. PLAN ON LETTING THE FLOOD WATCH EXPIRE NATURALLY AS THE RAIN SHOULD BE WINDING DOWN BEFORE 6 PM. MEANWHILE SNOW WAS SEEN IN CLOSE PROXIMITY TO H7/H5 LOW CENTERS NEAR KJLN EARLY THIS AFTERNOON PER THE RUC AND REGIONAL MOSAIC RADAR IMAGERY. THE UPPER LOW WILL TRACK ENE ACROSS SRN MO INTO SRN IL/IN TONIGHT...WITH PRECIPITATION MIXING WITH THEN CHANGING TO SNOW IN ASSOC WITH THE UPPER SYSTEM AND DEEPENING COLD AIR INFILTRATION. HAVE BASED OVERNIGHT TOTALS LARGELY ON THE SREF AND HPC GUIDANCE. 1-3 INCH SNOW TOTALS FORECAST ACROSS OUR FAR NORTHERN COUNTIES...WITH AN INCH OR SO CENTRAL AND GENERALLY LESS THAN OR APPROACHING 1 INCH SOUTH. A LOT OF WHAT FALLS MAY BE MAINLY ON GRASSY OR ELEVATED SURFACES. HOWEVER SOME ROADS MAY BE AFFECTED TOO...NOT ONLY BY THE WINTRY PRECIPITATION...BUT DUE TO BELOW FREEZING TEMPS AS THE NIGHT WEARS ON. THEREFORE PREFERRED HANDLING TONIGHT/S EXPECTED CONDITIONS WITH A WINTER WEATHER ADVISORY NRN 1/3...AND A SPECIAL WEATHER STATEMENT SOUTH. WILL HAVE TO WATCH THE WINDS TONIGHT TOO. THE SURFACE LOW JUST SW OF KMEG EARLY THIS AFTERNOON WILL DEEPEN CONSIDERABLY WHILE HEADING NE TONIGHT...REACHING OHIO BY 12Z. WILL ALSO MENTION THE GUSTY WIND POTENTIAL IN AN SPS. DO NOT EXPECT THE BACK EDGE SNOW TO HANG AROUND LONG SUNDAY MORNING. WILL CLEAR IT OUT PROGRESSIVELY AND DECREASE CLOUDS SUNDAY WITH THE DEPARTURE OF THE LOW. IT SHOULD REMAIN RATHER COLD THOUGH WITH LOW TROP CAA CONTINUING. QUIET AND COLD CONDITIONS ARE EXPECTED SUNDAY NIGHT WITH HIGH PRESSURE BUILDING IN ACROSS THE GULF COAST REGION. HIGH PRESSURE FIRMLY IN PLACE FOR MONDAY...WITH THE CENTER OF THE HIGH OVER THE DEEP SOUTH. THE CENTER OF THE HIGH MOVES OFF THE NORTHEAST INTO THE APPALACHIANS BY MONDAY NIGHT. WITH THE ZONAL UPPER FLOW PATTERN IN PLACE...BOTH THE 00Z ECMWF AND 06Z/12Z GFS BRING A WEAK SHORTWAVE WEST TO EAST ACROSS THE REGION...RESULTING IN SOME LIGHT QPF LATE TUESDAY AFTERNOON AND TUESDAY NIGHT. LOOKS LIKE THERE SHOULD BE A DECENT AMOUNT OF MOISTURE ESPECIALLY AFTER 06Z WED. HOWEVER...QPF AMOUNTS LOOKS TOO PUNY TO MESS WITH PUTTING ANYTHING IN THE FORECAST AT THIS TIME. ON WEDNESDAY...AN UPPER LEVEL RIDGE BEGINS TO BUILD OVER OUR REGION AS A TROUGH MOVES ACROSS THE DESERT SOUTHWEST AND INTO THE CENTRAL PLAINS. THE GFS AND ECMWF NOT TOO BAD WITH THE PROGRESSION OF THIS SYSTEM...WITH THE ECMWF A BIT FASTER. BOTH MODELS WANT TO BREAK OUT SOME VERY LIGHT PRECIPITATION FOR WEDNESDAY AND WEDNESDAY NIGHT ASSOCIATED WITH A WARM FRONT THAT WILL BE SITUATED NEAR THE COUNTY WARNING AREA. THIS IS HANDLED OK IN THE GRIDS WITH SOME SLIGHT CHANCE TO CHANCE POPS WEDNESDAY NIGHT. THE ASSOCIATED SURFACE LOW PRESSURE SYSTEM IS FORECAST TO MOVE OUT OF THE CENTRAL PLAINS WEDNESDAY NIGHT AND INTO MISSOURI BY 12Z THURSDAY. AGAIN...ASIDE FROM A SLIGHT LATITUDINAL DIFFERENCE IN THE ACTUAL LOW PLACEMENT...BOTH THE GFS AND ECWMF ARE VERY SIMILAR IN TIMING. IT APPEARS THE SURFACE LOW AND ASSOCIATED COLD FRONT MOVES ACROSS THE AREA DURING THE DAY ON THURSDAY. THE GFS AND ECMWF DO DIFFER ON WHERE THE LOW WILL TRACK TO OUR NORTHEAST...BUT IT DOES LOOK LIKE THURSDAY WILL BE OUR BEST DAY FOR RAINFALL. RAINFALL TAPERS OFF/COMES TO AN END THURSDAY NIGHT AS THE SYSTEM PULLS OUT OF THE AREA. BOTH THE GFS AND ECMWF WOULD INDICATE THAT THE PRECIP TYPE SHOULD BE ALL RAIN...SO WILL PULL MENTION OF SNOW OUT. MODELS REALLY DIVERGE SIGNIFICANTLY IN THE DAYS 6 AND 7 TIME FRAME. ON FRIDAY...THE 06Z GFS DEVELOPS ANOTHER WARM FRONT OVER THE AREA...WHILE AN UPPER LOW AND ASSOCIATED SURFACE LOW GET THEIR ACT TOGETHER IN THE CENTRAL PLAINS. THE ECMWF SHOWS HIGH PRESSURE BUILDING INTO THE REGION. THE 12Z GFS BACKS OFF A LITTLE BIT ON THE SPEED OF THE SYSTEM. THE 06Z/12Z GFS THEN SHOW THE AFOREMENTIONED LOW MOVING INTO OUR REGION ON SATURDAY...BRINGING SCATTERED RAIN WITH IT. THE ECMWF SHOWS THE HIGH MOVING OFF TO THE EAST AS AN UPPER LEVEL LOW MOVES OUT OF THE DESERT SOUTHWEST AND INTO THE SOUTHERN PLAINS. SO HAVE LEFT FRIDAY DRY FOR NOW BUT ADDED A CHANCE FOR PRECIPITATION ON SATURDAY. WE WILL HAVE TO WAIT AND SEE HOW THIS SYSTEM EVOLVES OVER THE NEXT FEW DAYS IN ORDER TO GET A BETTER HANDLE ON THINGS. && .AVIATION... AS THE AREA OF RAIN CONTINUES TO HEAD EAST...MAINLY IFR CIGS REMAIN...ALTHOUGH VSBYS BECOME P6SM. COULD SEE SOME DRIZZLE OR LIGHT RAIN DEVELOP IN THE WAKE OF THIS LARGE AREA OF RAIN. HOWEVER...LATER ON THIS AFTERNOON AND INTO THE EVENING HOURS...WE EXPECT RAIN TO REDEVELOP/MOVE INTO THE AREA ON THE BACKSIDE OF THE SURFACE LOW THAT WILL BE TRACKING INTO MIDDLE TENNESSEE. EXPECT A CHANGEOVER TO ALL SNOW BTWN 03Z AND 06Z FROM WEST TO EAST. ALONG WITH THAT CHANGEOVER...WILL BE VERY STRONG NORTHWEST WINDS THAT WILL LIKELY GUST AS HIGH AS 30 KT OVERNIGHT TONIGHT. COULD SEE CLOUDS DEPARTING FROM WEST TO EAST THROUGHOUT THE MORNING HOURS. && .PAH WATCHES/WARNINGS/ADVISORIES... KY...FLOOD WATCH UNTIL 6 PM CST THIS AFTERNOON FOR CALDWELL-CALLOWAY- CHRISTIAN-DAVIESS-HOPKINS-LYON-MARSHALL-MCLEAN-MUHLENBERG- TODD-TRIGG. MO...WINTER WEATHER ADVISORY FROM 6 PM THIS EVENING TO 6 AM CST SUNDAY FOR PERRY MO. IL...WINTER WEATHER ADVISORY FROM 6 PM THIS EVENING TO 6 AM CST SUNDAY FOR EDWARDS-FRANKLIN-GALLATIN-HAMILTON-JACKSON- JEFFERSON-PERRY IL-SALINE-WABASH-WAYNE IL-WHITE-WILLIAMSON. IN...WINTER WEATHER ADVISORY FROM 6 PM THIS EVENING TO 6 AM CST SUNDAY FOR GIBSON-PIKE-POSEY-SPENCER-VANDERBURGH-WARRICK. && $$ CN/CW ky AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LAKE CHARLES LA 517 AM CST SAT DEC 15 2007 VERY BUSY MORNING WITH NUMEROUS IMPACTS TO FORECAST TODAY. POWERFUL STORM SYSTEM EXPECTED TO MOVE ACROSS THE REGION TODAY...WITH SEVERE WEATHER POTENTIAL...POST-FRONTAL WINDS...AND TEMPERATURES THE MAIN FORECAST CHALLENGES. THE COLD FRONT WAS LOCATED GENERALLY ALONG A LINE FROM SHREVEPORT TO WEST OF HUNTSVILLE TO EAST OF SAN ANTONIO. SHOWERS AND THUNDERSTORMS HAVE DEVELOPED THIS MORNING ALONG AND EITHER SIDE OF THE FRONT...WITH SOME SHOWERS DEVELOPING IN THE WARM SECTOR ACROSS THE CWA. RAINFALL SEEMS LIKE A CERTAINTY AND WILL GO CATEGORICAL ON POPS TODAY...TAPERING OFF FROM WEST TO EAST WITH FRONTAL PASSAGE. TEMPERATURES WILL BE TRICKY WITH HIGHS OCCURRING AHEAD OF THE FRONT AND PRIOR TO PRECIP ONSET...WITH FALLING TEMPS THEREAFTER. SPC HAS PLACED THE ENTIRE AREA IN A SLIGHT RISK FOR SEVERE WEATHER TODAY. FORECAST SOUNDINGS SHOW INCREASINGLY FAVORABLE KINEMATICS FOR SEVERE WEATHER THIS MORNING AND AFTERNOON AHEAD OF THE FRONT...WITH 0-3KM SRH VALUES OF 200-300 M2/S2 AND DEEP LAYER SHEAR AROUND 60 KNOTS. DESPITE WIDESPREAD CLOUD COVER AND A LOW LEVEL INVERSION IN PLACE THIS MORNING...NAM AND RUC SOUNDINGS BOTH ERODE THE INVERSION DURING THE LATE MORNING HOURS LEADING TO CAPE VALUES GENERALLY FROM 500 TO 1000 J/KG AREAWIDE BUT AS HIGH AS 1500 J/KG PER NAM IN SOUTHERN LOUISIANA. THIS MAY LEAD TO SOME SURFACE BASED THUNDERSTORM DEVELOPMENT...PARTICULARLY SOUTHERN ZONES AND COASTAL WATERS WHERE MOISTURE AND INSTABILITY WILL BE HIGHER. WILL CONTINUE TO MENTION HEAVY RAINFALL AND DAMAGING WINDS AS THE MAIN THREATS...BUT A FEW TORNADOES ARE ALSO POSSIBLE IF SURFACE BASED CONVECTION CAN DEVELOP...ESPECIALLY ACROSS SOUTHERN ZONES. MUCH COOLER AND DRIER AIRMASS WILL BE USHERED IN BEHIND THE FRONT...WITH A VERY TIGHT PRESSURE GRADIENT LEADING TO GUSTY WINDS ACROSS THE AREA. CLOSE LOOK AT MODELS INDICATES SOUTHERN ZONES WILL REACH LAKE WIND ADVISORY CRITERIA TODAY...AND HAVE ISSUED AN ADVISORY ACCORDINGLY. EVEN STRONGER WINDS WILL BE SEEN ACROSS THE COASTAL WATERS...WHERE SUSTAINED WINDS WILL BE NEAR GALE FORCE AT TIMES. DID NOT HAVE MUCH TIME TO LOOK AT EXTENDED AND FEW CHANGES WERE MADE AFTER TODAY. STILL APPEARS A DECENT FREEZE WILL BE SEEN MONDAY MORNING ALONG AND NORTH OF I-10 WITH TEMPERATURES DOWN INTO THE UPPER 20S IN NORTHERN ZONES. ONSHORE FLOW RETURNS BY TUESDAY WITH WARMING TEMPERATURES AND LOW CHANCES FOR SHOWERS AND STORMS BACK IN THE PICTURE NEXT WEEK. && .AVIATION... MESSY WEATHER DAY WITH IFR CONDITIONS EXPECTED THROUGH EARLY THIS MORNING BECOMING MVFR LATE THIS MORNING AND AFTERNOON. SOUTHERLY WINDS WILL INCREASE AHEAD OF THE COLD FRONT WITH SHOWERS AND THUNDERSTORMS POSSIBLE ALL TAF SITES. WINDS TO SWITCH TO NORTHWESTERLY BEHIND FRONTAL PASSAGE...WITH GUSTS TO 30 KNOTS POSSIBLE BEHIND THE FRONT ESPECIALLY SOUTHERN TAF SITES. ALL TERMINALS SHOULD REACH VFR BY THIS EVENING. && .MARINE... HAZARDOUS WEATHER EXPECTED ACROSS THE COASTAL WATERS TODAY AS A POWERFUL COLD FRONT MOVES EASTWARD. SHOWERS AND THUNDERSTORMS WITH GUSTY WINDS WILL BE POSSIBLE AHEAD OF THE FRONT. AFTER FRONTAL PASSAGE...A TIGHT PRESSURE GRADIENT AND COOLER AIR MOVING OVER THE WARMER GULF WATERS WILL CREATE STRONG NORTHWEST WINDS. MODELS ALL INDICATE SUSTAINED WINDS OF AROUND 30 KNOTS WILL BE SEEN FOR MUCH OF THE LATE AFTERNOON AND EVENING HOURS...WITH GUSTS UP TO 40 KNOTS POSSIBLE. APPEARS GALE WARNING LOCAL CRITERIA OF SUSTAINED 35+ KNOTS WILL NOT BE MET BUT IT WILL BE CLOSE...AND AN UPGRADE TO GALE WARNING FOR THE OUTER WATERS IS STILL POSSIBLE LATER TODAY. && .PRELIMINARY POINT TEMPS/POPS... KLCH 69 34 55 32 / 100 0 0 0 KBPT 69 34 55 33 / 100 0 0 0 KAEX 66 32 52 28 / 80 10 0 0 KLFT 71 35 54 31 / 80 10 0 0 && .LCH WATCHES/WARNINGS/ADVISORIES... LA...LAKE WIND ADVISORY FROM NOON SATURDAY TO 9 PM SATURDAY FOR THE FOLLOWING ZONES: ACADIA...CALCASIEU...CAMERON...IBERIA... JEFFERSON DAVIS...LAFAYETTE...LOWER ST. MARTIN...ST. MARY... UPPER ST. MARTIN...AND VERMILION. TX...LAKE WIND ADVISORY FROM NOON SATURDAY TO 9 PM SATURDAY FOR THE FOLLOWING ZONES: JEFFERSON...AND ORANGE. GM...SMALL CRAFT ADVISORY FROM NOON SATURDAY TO 9 AM SUNDAY FOR THE FOLLOWING ZONES: COASTAL WATERS FROM CAMERON, LA TO HIGH ISLAND, TX OUT 20 NM...COASTAL WATERS FROM INTRACOASTAL CITY TO CAMERON, LA OUT 20 NM...COASTAL WATERS FROM LOWER ATCHAFALAYA RIVER TO INTRACOASTAL CITY, LA OUT 20 NM... WATERS FROM CAMERON, LA TO HIGH ISLAND, TX EXTENDING FROM 20 NM TO 60 NM...WATERS FROM INTRACOASTAL CITY, LA TO CAMERON, LA EXTENDING FROM 20 NM TO 60 NM...AND WATERS FROM LOWER ATCHAFALAYA RIVER TO INTRACOASTAL CITY, LA EXTENDING FROM 20 NM TO 60 NM. && $$ SHAMBURGER la AREA FORECAST DISCUSSION...UPDATE NATIONAL WEATHER SERVICE MARQUETTE MI 1005 PM EST SUN DEC 16 2007 .UPDATE... UPDATED TO BUMP UP FCST MIN TEMPS AS LO CLD COVER LOOKS WL BE MORE PERSISTENT THAN PREVIOUSLY THOUGHT PER RECENT STLT TRENDS AND LARGE CLD MASS TO THE SW DRIFTING NEWD. ALTHOUGH THERE MAY BE SOME BREAKS IN THE CLD WITH HI PRES RDG AXIS BLDG INTO THE UPR LKS...EXPECT A MORE CLDY NIGHT AS LOWER CLD TO THE SW OVERSPREADS THE AREA WHERE CLD COVER LOOKED LIKE IT WOULD BREAK EARLIER. ALSO BUMPED UP POPS/ SN FALL AMTS A BIT OVER LUCE COUNTY WITH LLVL CNVGC BTWN NNE LAND BREEZE OFF ONTARIO AND MORE NW FLOW AT GRAND MARAIS/ERY. APX REPORTS PARADISE IN CHIPPEWA COUNTY PICKED UP 4"/2 HRS UNDER THIS BAND. LOCAL HI RES MODEL SHOWS SN BAND IMPACTING AREAS MAINLY E OF LUCE COUNTY...SO NO NEED FOR ANY HEADLINES. OTRW...RISING HGTS/LOWERING SUBSIDENCE INVRN OVERNGT SHOULD CAUSE LES TO DIMINISH AFT 06Z. COORDINATED WITH GRB/APX. && .SYNOPSIS... 20Z WATER VAPOR LOOP AND RUC 500MB HEIGHT ANALYSIS SHOWED A TROUGH JUST OFF THE WEST COAST...BROAD RIDGING MOVING INTO CENTRAL NORTH AMERICA WITH AN UPPER LOW OVER SOUTHERN SASKATCHEWAN ON THE TOP OF THE RIDGE...AND A STRONG TROUGH MOVING THROUGH THE EASTERN GREAT LAKES. THE CWA IS GENERALLY UNDER THE INFLUENCE OF THE STRONG TROUGH...NOTED BY NORTHERLY LOW LEVEL FLOW BETWEEN A 987 MB SURFACE LOW NEAR BUFFALO AND A 1019MB RIDGE STRETCHING FROM NW ONTARIO THROUGH MN. THIS NORTHERLY FLOW HAS BEEN BRINGING 850MB TEMPS OF -10C ACROSS LAKE SUPERIOR...PLENTY COLD ENOUGH TO GENERATE LAKE EFFECT SNOW SHOWERS. FLOW HAS BEGUN TO BACK TO THE NW...WHICH IS HELPING TO DIMINISH THE SNOW SHOWERS OVER BARAGA AND MARQUETTE COUNTIES. DRIER AIR FILTERING IN FROM THE WEST...SEEN ON THE 12Z INL SOUNDING...HAS NOW DECREASED TO THE BAND-LENGTH ON WESTERN LAKE SUPERIOR TO ABOUT HALF OF THE FETCH. FARTHER TO THE NW...1005 MB LOW PRESSURE IS MOVING ACROSS SOUTHERN SASKATCHEWAN...WITH SOME MID CLOUDS EAST OF THE WARM FRONT THAT STRETCHES SE TOWARDS SE SOUTH DAKOTA. CANADIAN RADAR IMAGERY ALSO SHOWS SOME SNOW AROUND THE SURFACE LOW OVER SOUTHERN SASKATCHEWAN. && .SHORT TERM (TONIGHT AND MONDAY)... THERE REMAINS SOME MODEL DIFFERENCES ON THE HANDLING OF THE UPPER LOW OVER SOUTHERN SASKATCHEWAN AS IT HEADS TOWARDS UPPER MICHIGAN...THOUGH THE GENERAL TREND AT LEAST IN THE GFS HAS BEEN FARTHER NORTH. FOR THE PURPOSE OF THE FORECAST...FOLLOWED THE MAJORITY CONSENSUS OF THE GFS/UKMET/LOCAL WRF-ARW/ECMWF. FOR TONIGHT...UPPER AND SURFACE RIDGING WILL BUILD IN AHEAD OF THE UPPER LOW...BECOMING SITUATED OVER THE CENTRAL U.P. AROUND 12Z MON. FLOW SHOULD CONTINUE TO BACK TONIGHT...AND LIKELY TOWARDS THE SW OVER THE FAR WESTERN U.P. AFTER MIDNIGHT. THIS SHOULD KEEP LAKE EFFECT SNOW SHOWERS GOING IN NW FLOW AREAS...MOST NUMEROUS EAST OF MARQUETTE WHERE THE LONGER FETCH LENGTH CAN OVERCOME THE DRY AIR AND UPPER LEVEL SUBSIDENCE. THIS DRY AIR AND UPPER LEVEL SUBSIDENCE WILL HELP LOWER ACCUMULATIONS EAST OF MARQUETTE...THOUGH. BIG QUESTION TONIGHT IS HOW LOW TO GO ON TEMPERATURES...BECAUSE WITH THE DRY AIR AND SURFACE RIDGE MOVING IN...ANY CLEARING COULD CAUSE TEMPS TO PLUMMET. FIGURE THE BEST CHANCE OF CLEARING WILL BE IN THE FAR SOUTH CENTRAL U.P....WHICH IS WHERE IT IS MOSTLY CLEAR NOW. HOWEVER...AS WINDS BACK WESTERLY AFTER MIDNIGHT...THE REST OF THE INTERIOR OF THE WESTERN U.P. COULD CLEAR OUT TOO. THUS THE LOWEST TEMPS ARE FORECAST THERE WITH READINGS AROUND ZERO. EVENING SHIFT WILL NEED TO MONITOR CLOUDS AND TEMPS CLOSELY. ON MONDAY...UPPER LOW IS EXPECTED TO MOVE OVER NORTHERN LAKE SUPERIOR. MUCH OF THE MOISTURE AND FORCING WILL LIKELY OCCUR UNDER THIS UPPER LOW AS IS BEING OBSERVED UPSTREAM...THUS HIGHEST POPS ARE SITUATED OVER NORTHERN LAKE SUPERIOR. THE WARM ADVECTION AHEAD OF THE UPPER LOW COULD ALSO PRODUCE SOME LIGHT SNOW OR FLURRIES...AS GRAND FORKS IS REPORTING AT 3 PM EST. THUS HAVE MAINTAINED AT LEAST 20 POPS FOR MUCH OF THE CWA...EXCEPT NEAR THE WISCONSIN BORDER WHERE THE FORCING IS NOT ENOUGH TO PRODUCE SNOW. IN ADDITION...EARLY IN THE FORECAST SOME LIGHT LAKE EFFECT COULD STILL BE GOING OVER THE FAR EASTERN CWA WHERE WINDS HAVE NOT BACKED TO THE SW YET. THUS 20 POPS REMAIN THERE FOR THE MORNING. ANOTHER CONCERN IS AS THE UPPER LOW MOVES AWAY...LINGERING LOW LEVEL MOISTURE BELOW THE -10C ISOTHERM SITS AROUND...PARTICULARLY IN THE NORTHERN U.P.. SINCE THE WINDS ARE PROGGED OUT OF THE SW...WHICH IS NOT AN UPSLOPE DIRECTION...NO FREEZING DRIZZLE IS MENTIONED. TEMPERATURES SHOULD BE AS WARM AS THEY ARE TODAY OR PERHAPS SLIGHTLY WARMER SINCE 850MB TEMPS ARE PROGGED TO RISE TO -7 TO -9C. .LONG TERM (MONDAY NIGHT THROUGH NEXT SUNDAY)... ECMWF A BIT FARTHER NORTH WITH PAIR OF QUICK MOVING LOW PRESSURE SYSTEMS FOR MON NIGHT AND AGAIN TUE NIGHT INTO WED. GFS WAS A BIT FARTHER SOUTH AND AT THIS POINT WAS NOT PREFERRED. GOING WITH THE FARTHER NORTH SOLUTIONS KEEPS THE BEST CHANCES OF PCPN OVER NORTHERN ZONES INTO LK SUPERIOR. TEMPS IN THE BLYR REMAIN COLD ENOUGH FOR SNOW. HOWEVER...BOTH NAM/GFS SOUNDINGS SHOW LIMITED MOISTURE EXTENDING TO THE -10C ISOTHERM SO FREEZING DRIZZLE IS POSSIBLE AS WELL. LIFT IN THE SHALLOW MOIST LAYER IS MINIMAL...BUT THERE IS ENOUGH OF A CHANCE LATE TUESDAY INTO EARLY WEDNESDAY TO INCLUDE IT FOR AREAS WHERE BLYR WINDS COULD PROVIDE ADDITIONAL UPSLOPE LIFT. FOR THE MOST PART...AFTER LGT PCPN ENDS ON WED...UPPER LEVEL RIDGING LEADS TO QUIET WX ON INTO THU INTO FRI. WARM AIR ADVECTION ALOFT AND EVENTUALLY AT THE SFC COULD LEAD TO SOME SPOTTY LGT PCPN DURING THIS TIME. IF PCPN OCCURS FRI...TEMPS MAY EVEN BE WARM ENOUGH TO JUSTIFY A MIX OF RAIN/SNOW. OTHERWISE...DO EXPECT FAIR AMOUNT OF CLOUDS WITH PERSISTENT INVERSION LIKELY IN PLACE. PRIMARY FOCUS LATE IN THE WEEK INTO NEXT WEEKEND IS HOW FAR NORTH THE STRONG TROF OVER SOUTHERN PLAINS WILL EJECT. HOW THIS TROF PLAYS OUT WILL DETERMINE THE POTENTIAL FOR A SIGNIFICANT STORM SYSTEM OVER THE GREAT LAKES NEXT WEEKEND. A BIT EARLY TO GET WRAPPED UP IN DETAILS...BUT LOW PRESSURE TRACK AND HEAVY SNOW TO THE NORTHWEST OF IT LOOKS LIKE IT WILL SET UP SOMEWHERE OVER THE UPR-CNTRL GREAT LAKES LATE SAT INTO NEXT SUN. INCREASED POPS SOME BUT STILL A CHANCE AT THIS POINT. LATEST ECMWF IS EVEN FARTHER TO THE WEST WITH A POTENTIAL FOR SOME RAIN INTO THE SOUTHEAST CWA BY 12Z SUN. && .AVIATION (FOR THE 00Z TAF ISSUANCE)... EXPECT MVFR CIGS TO LINGER MOST OF THE NGT AT BOTH SITES WITH RELATIVELY MOIST LK MODIFIED AIR TRAPPED UNDER LO INVRN STRENGTHENED BY SUBSIDENCE IN WAKE OF DEEP LO PRES EXITING TO THE E. BUT LES INTENSITY/VSBY REDUCTION WL BE LIMITED BY ARRIVAL OF DRIER AIR NOTED OVER NRN MN...WHERE SKIES ARE MOCLR AND 20Z TAMDAR SDNG FM DLH SHOWS INVRN BASE BLO H9. THIS DRY AIR AND BACKING FLOW TO A MORE DOWNSLOPE WLY COMPONENT WL LIKELY CAUSE CIGS AT SAW TO RISE TO VFR BEFORE LO CLDS SCATTER OUT THERE LATE TNGT WITH ARRIVAL OF SFC RDG AXIS. BUT WLY FLOW OVER WRN LK SUP WL TEND TO MAINTAIN LOWER MVFR CIGS AT CMX THRU SUNRISE. ONCE FLOW TURNS TO THE SW MON MRNG THOUGH...EXPECT CIG TO RISE TO VFR. FCST TRACK OF INCOMING LO PRES NOW OVER SCNTRL CAN ACRS NRN LK SUP ON MON WITH ABSENCE OF SGNFT MSTR IN THE NRN PLAINS SUGS ANY PCPN ON MON WL BE ON THE LGT SIDE...ESPECIALLY AT SAW. BUT EXPECTED VEERING LLVL FLOW TO MORE W AT CMX IN THE AFTN WARRANTS FCST OF LOWER CIG/VSBY TO MVFR RANGE AGAIN AT THAT LOCATION. && .MARINE (FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)... BETWEEN NOW AND WEDNESDAY...TWO LOW PRESSURE AREAS ARE EXPECTED TO MOVE ACROSS LAKE SUPERIOR...ONE ON MONDAY AND THE OTHER TUE NIGHT. HOWEVER...WINDS WILL REMAIN BELOW 30 KT THROUGH WEDNESDAY AS NEITHER SYSTEM IS STRONG ENOUGH TO PRODUCE GALES. A RIDGE OF HIGH PRESSURE WILL THEN BUILD IN FOR THU AND FRI...WHICH SHOULD HELP KEEP WINDS AT OR BELOW 25 KNOTS. && .MQT WATCHES/WARNINGS/ADVISORIES...NONE. && $$ UPDATE...KC SYNOPSIS/SHORT TERM...AJ LONG TERM...JLA MARINE...AJ AVIATION...KC mi AREA FORECAST DISCUSSION...UPDATE NATIONAL WEATHER SERVICE MARQUETTE MI 630 PM EST SUN DEC 16 2007 UPDATED FOR 00Z TAFS .SYNOPSIS... 20Z WATER VAPOR LOOP AND RUC 500MB HEIGHT ANALYSIS SHOWED A TROUGH JUST OFF THE WEST COAST...BROAD RIDGING MOVING INTO CENTRAL NORTH AMERICA WITH AN UPPER LOW OVER SOUTHERN SASKATCHEWAN ON THE TOP OF THE RIDGE...AND A STRONG TROUGH MOVING THROUGH THE EASTERN GREAT LAKES. THE CWA IS GENERALLY UNDER THE INFLUENCE OF THE STRONG TROUGH...NOTED BY NORTHERLY LOW LEVEL FLOW BETWEEN A 987 MB SURFACE LOW NEAR BUFFALO AND A 1019MB RIDGE STRETCHING FROM NW ONTARIO THROUGH MN. THIS NORTHERLY FLOW HAS BEEN BRINGING 850MB TEMPS OF -10C ACROSS LAKE SUPERIOR...PLENTY COLD ENOUGH TO GENERATE LAKE EFFECT SNOW SHOWERS. FLOW HAS BEGUN TO BACK TO THE NW...WHICH IS HELPING TO DIMINISH THE SNOW SHOWERS OVER BARAGA AND MARQUETTE COUNTIES. DRIER AIR FILTERING IN FROM THE WEST...SEEN ON THE 12Z INL SOUNDING...HAS NOW DECREASED TO THE BAND-LENGTH ON WESTERN LAKE SUPERIOR TO ABOUT HALF OF THE FETCH. FARTHER TO THE NW...1005 MB LOW PRESSURE IS MOVING ACROSS SOUTHERN SASKATCHEWAN...WITH SOME MID CLOUDS EAST OF THE WARM FRONT THAT STRETCHES SE TOWARDS SE SOUTH DAKOTA. CANADIAN RADAR IMAGERY ALSO SHOWS SOME SNOW AROUND THE SURFACE LOW OVER SOUTHERN SASKATCHEWAN. && .SHORT TERM (TONIGHT AND MONDAY)... THERE REMAINS SOME MODEL DIFFERENCES ON THE HANDLING OF THE UPPER LOW OVER SOUTHERN SASKATCHEWAN AS IT HEADS TOWARDS UPPER MICHIGAN...THOUGH THE GENERAL TREND AT LEAST IN THE GFS HAS BEEN FARTHER NORTH. FOR THE PURPOSE OF THE FORECAST...FOLLOWED THE MAJORITY CONSENSUS OF THE GFS/UKMET/LOCAL WRF-ARW/ECMWF. FOR TONIGHT...UPPER AND SURFACE RIDGING WILL BUILD IN AHEAD OF THE UPPER LOW...BECOMING SITUATED OVER THE CENTRAL U.P. AROUND 12Z MON. FLOW SHOULD CONTINUE TO BACK TONIGHT...AND LIKELY TOWARDS THE SW OVER THE FAR WESTERN U.P. AFTER MIDNIGHT. THIS SHOULD KEEP LAKE EFFECT SNOW SHOWERS GOING IN NW FLOW AREAS...MOST NUMEROUS EAST OF MARQUETTE WHERE THE LONGER FETCH LENGTH CAN OVERCOME THE DRY AIR AND UPPER LEVEL SUBSIDENCE. THIS DRY AIR AND UPPER LEVEL SUBSIDENCE WILL HELP LOWER ACCUMULATIONS EAST OF MARQUETTE...THOUGH. BIG QUESTION TONIGHT IS HOW LOW TO GO ON TEMPERATURES...BECAUSE WITH THE DRY AIR AND SURFACE RIDGE MOVING IN...ANY CLEARING COULD CAUSE TEMPS TO PLUMMET. FIGURE THE BEST CHANCE OF CLEARING WILL BE IN THE FAR SOUTH CENTRAL U.P....WHICH IS WHERE IT IS MOSTLY CLEAR NOW. HOWEVER...AS WINDS BACK WESTERLY AFTER MIDNIGHT...THE REST OF THE INTERIOR OF THE WESTERN U.P. COULD CLEAR OUT TOO. THUS THE LOWEST TEMPS ARE FORECAST THERE WITH READINGS AROUND ZERO. EVENING SHIFT WILL NEED TO MONITOR CLOUDS AND TEMPS CLOSELY. ON MONDAY...UPPER LOW IS EXPECTED TO MOVE OVER NORTHERN LAKE SUPERIOR. MUCH OF THE MOISTURE AND FORCING WILL LIKELY OCCUR UNDER THIS UPPER LOW AS IS BEING OBSERVED UPSTREAM...THUS HIGHEST POPS ARE SITUATED OVER NORTHERN LAKE SUPERIOR. THE WARM ADVECTION AHEAD OF THE UPPER LOW COULD ALSO PRODUCE SOME LIGHT SNOW OR FLURRIES...AS GRAND FORKS IS REPORTING AT 3 PM EST. THUS HAVE MAINTAINED AT LEAST 20 POPS FOR MUCH OF THE CWA...EXCEPT NEAR THE WISCONSIN BORDER WHERE THE FORCING IS NOT ENOUGH TO PRODUCE SNOW. IN ADDITION...EARLY IN THE FORECAST SOME LIGHT LAKE EFFECT COULD STILL BE GOING OVER THE FAR EASTERN CWA WHERE WINDS HAVE NOT BACKED TO THE SW YET. THUS 20 POPS REMAIN THERE FOR THE MORNING. ANOTHER CONCERN IS AS THE UPPER LOW MOVES AWAY...LINGERING LOW LEVEL MOISTURE BELOW THE -10C ISOTHERM SITS AROUND...PARTICULARLY IN THE NORTHERN U.P.. SINCE THE WINDS ARE PROGGED OUT OF THE SW...WHICH IS NOT AN UPSLOPE DIRECTION...NO FREEZING DRIZZLE IS MENTIONED. TEMPERATURES SHOULD BE AS WARM AS THEY ARE TODAY OR PERHAPS SLIGHTLY WARMER SINCE 850MB TEMPS ARE PROGGED TO RISE TO -7 TO -9C. .LONG TERM (MONDAY NIGHT THROUGH NEXT SUNDAY)... ECMWF A BIT FARTHER NORTH WITH PAIR OF QUICK MOVING LOW PRESSURE SYSTEMS FOR MON NIGHT AND AGAIN TUE NIGHT INTO WED. GFS WAS A BIT FARTHER SOUTH AND AT THIS POINT WAS NOT PREFERRED. GOING WITH THE FARTHER NORTH SOLUTIONS KEEPS THE BEST CHANCES OF PCPN OVER NORTHERN ZONES INTO LK SUPERIOR. TEMPS IN THE BLYR REMAIN COLD ENOUGH FOR SNOW. HOWEVER...BOTH NAM/GFS SOUNDINGS SHOW LIMITED MOISTURE EXTENDING TO THE -10C ISOTHERM SO FREEZING DRIZZLE IS POSSIBLE AS WELL. LIFT IN THE SHALLOW MOIST LAYER IS MINIMAL...BUT THERE IS ENOUGH OF A CHANCE LATE TUESDAY INTO EARLY WEDNESDAY TO INCLUDE IT FOR AREAS WHERE BLYR WINDS COULD PROVIDE ADDITIONAL UPSLOPE LIFT. FOR THE MOST PART...AFTER LGT PCPN ENDS ON WED...UPPER LEVEL RIDGING LEADS TO QUIET WX ON INTO THU INTO FRI. WARM AIR ADVECTION ALOFT AND EVENTUALLY AT THE SFC COULD LEAD TO SOME SPOTTY LGT PCPN DURING THIS TIME. IF PCPN OCCURS FRI...TEMPS MAY EVEN BE WARM ENOUGH TO JUSTIFY A MIX OF RAIN/SNOW. OTHERWISE...DO EXPECT FAIR AMOUNT OF CLOUDS WITH PERSISTENT INVERSION LIKELY IN PLACE. PRIMARY FOCUS LATE IN THE WEEK INTO NEXT WEEKEND IS HOW FAR NORTH THE STRONG TROF OVER SOUTHERN PLAINS WILL EJECT. HOW THIS TROF PLAYS OUT WILL DETERMINE THE POTENTIAL FOR A SIGNIFICANT STORM SYSTEM OVER THE GREAT LAKES NEXT WEEKEND. A BIT EARLY TO GET WRAPPED UP IN DETAILS...BUT LOW PRESSURE TRACK AND HEAVY SNOW TO THE NORTHWEST OF IT LOOKS LIKE IT WILL SET UP SOMEWHERE OVER THE UPR-CNTRL GREAT LAKES LATE SAT INTO NEXT SUN. INCREASED POPS SOME BUT STILL A CHANCE AT THIS POINT. LATEST ECMWF IS EVEN FARTHER TO THE WEST WITH A POTENTIAL FOR SOME RAIN INTO THE SOUTHEAST CWA BY 12Z SUN. && .AVIATION (FOR THE 00Z TAF ISSUANCE)... EXPECT MVFR CIGS TO LINGER MOST OF THE NGT AT BOTH SITES WITH RELATIVELY MOIST LK MODIFIED AIR TRAPPED UNDER LO INVRN STRENGTHENED BY SUBSIDENCE IN WAKE OF DEEP LO PRES EXITING TO THE E. BUT LES INTENSITY/VSBY REDUCTION WL BE LIMITED BY ARRIVAL OF DRIER AIR NOTED OVER NRN MN...WHERE SKIES ARE MOCLR AND 20Z TAMDAR SDNG FM DLH SHOWS INVRN BASE BLO H9. THIS DRY AIR AND BACKING FLOW TO A MORE DOWNSLOPE WLY COMPONENT WL LIKELY CAUSE CIGS AT SAW TO RISE TO VFR BEFORE LO CLDS SCATTER OUT THERE LATE TNGT WITH ARRIVAL OF SFC RDG AXIS. BUT WLY FLOW OVER WRN LK SUP WL TEND TO MAINTAIN LOWER MVFR CIGS AT CMX THRU SUNRISE. ONCE FLOW TURNS TO THE SW MON MRNG THOUGH...EXPECT CIG TO RISE TO VFR. FCST TRACK OF INCOMING LO PRES NOW OVER SCNTRL CAN ACRS NRN LK SUP ON MON WITH ABSENCE OF SGNFT MSTR IN THE NRN PLAINS SUGS ANY PCPN ON MON WL BE ON THE LGT SIDE...ESPECIALLY AT SAW. BUT EXPECTED VEERING LLVL FLOW TO MORE W AT CMX IN THE AFTN WARRANTS FCST OF LOWER CIG/VSBY TO MVFR RANGE AGAIN AT THAT LOCATION. && .MARINE (FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)... BETWEEN NOW AND WEDNESDAY...TWO LOW PRESSURE AREAS ARE EXPECTED TO MOVE ACROSS LAKE SUPERIOR...ONE ON MONDAY AND THE OTHER TUE NIGHT. HOWEVER...WINDS WILL REMAIN BELOW 30 KT THROUGH WEDNESDAY AS NEITHER SYSTEM IS STRONG ENOUGH TO PRODUCE GALES. A RIDGE OF HIGH PRESSURE WILL THEN BUILD IN FOR THU AND FRI...WHICH SHOULD HELP KEEP WINDS AT OR BELOW 25 KNOTS. && .MQT WATCHES/WARNINGS/ADVISORIES...NONE. && $$ SYNOPSIS/SHORT TERM...AJ LONG TERM...JLA MARINE...AJ AVIATION...KC mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MARQUETTE MI 345 PM EST SUN DEC 16 2007 .SYNOPSIS... 20Z WATER VAPOR LOOP AND RUC 500MB HEIGHT ANALYSIS SHOWED A TROUGH JUST OFF THE WEST COAST...BROAD RIDGING MOVING INTO CENTRAL NORTH AMERICA WITH AN UPPER LOW OVER SOUTHERN SASKATCHEWAN ON THE TOP OF THE RIDGE...AND A STRONG TROUGH MOVING THROUGH THE EASTERN GREAT LAKES. THE CWA IS GENERALLY UNDER THE INFLUENCE OF THE STRONG TROUGH...NOTED BY NORTHERLY LOW LEVEL FLOW BETWEEN A 987 MB SURFACE LOW NEAR BUFFALO AND A 1019MB RIDGE STRETCHING FROM NW ONTARIO THROUGH MN. THIS NORTHERLY FLOW HAS BEEN BRINGING 850MB TEMPS OF -10C ACROSS LAKE SUPERIOR...PLENTY COLD ENOUGH TO GENERATE LAKE EFFECT SNOW SHOWERS. FLOW HAS BEGUN TO BACK TO THE NW...WHICH IS HELPING TO DIMINISH THE SNOW SHOWERS OVER BARAGA AND MARQUETTE COUNTIES. DRIER AIR FILTERING IN FROM THE WEST...SEEN ON THE 12Z INL SOUNDING...HAS NOW DECREASED TO THE BAND-LENGTH ON WESTERN LAKE SUPERIOR TO ABOUT HALF OF THE FETCH. FARTHER TO THE NW...1005 MB LOW PRESSURE IS MOVING ACROSS SOUTHERN SASKATCHEWAN...WITH SOME MID CLOUDS EAST OF THE WARM FRONT THAT STRETCHES SE TOWARDS SE SOUTH DAKOTA. CANADIAN RADAR IMAGERY ALSO SHOWS SOME SNOW AROUND THE SURFACE LOW OVER SOUTHERN SASKATCHEWAN. && .SHORT TERM (TONIGHT AND MONDAY)... THERE REMAINS SOME MODEL DIFFERENCES ON THE HANDLING OF THE UPPER LOW OVER SOUTHERN SASKATCHEWAN AS IT HEADS TOWARDS UPPER MICHIGAN...THOUGH THE GENERAL TREND AT LEAST IN THE GFS HAS BEEN FARTHER NORTH. FOR THE PURPOSE OF THE FORECAST...FOLLOWED THE MAJORITY CONSENSUS OF THE GFS/UKMET/LOCAL WRF-ARW/ECMWF. FOR TONIGHT...UPPER AND SURFACE RIDGING WILL BUILD IN AHEAD OF THE UPPER LOW...BECOMING SITUATED OVER THE CENTRAL U.P. AROUND 12Z MON. FLOW SHOULD CONTINUE TO BACK TONIGHT...AND LIKELY TOWARDS THE SW OVER THE FAR WESTERN U.P. AFTER MIDNIGHT. THIS SHOULD KEEP LAKE EFFECT SNOW SHOWERS GOING IN NW FLOW AREAS...MOST NUMEROUS EAST OF MARQUETTE WHERE THE LONGER FETCH LENGTH CAN OVERCOME THE DRY AIR AND UPPER LEVEL SUBSIDENCE. THIS DRY AIR AND UPPER LEVEL SUBSIDENCE WILL HELP LOWER ACCUMULATIONS EAST OF MARQUETTE...THOUGH. BIG QUESTION TONIGHT IS HOW LOW TO GO ON TEMPERATURES...BECAUSE WITH THE DRY AIR AND SURFACE RIDGE MOVING IN...ANY CLEARING COULD CAUSE TEMPS TO PLUMMET. FIGURE THE BEST CHANCE OF CLEARING WILL BE IN THE FAR SOUTH CENTRAL U.P....WHICH IS WHERE IT IS MOSTLY CLEAR NOW. HOWEVER...AS WINDS BACK WESTERLY AFTER MIDNIGHT...THE REST OF THE INTERIOR OF THE WESTERN U.P. COULD CLEAR OUT TOO. THUS THE LOWEST TEMPS ARE FORECAST THERE WITH READINGS AROUND ZERO. EVENING SHIFT WILL NEED TO MONITOR CLOUDS AND TEMPS CLOSELY. ON MONDAY...UPPER LOW IS EXPECTED TO MOVE OVER NORTHERN LAKE SUPERIOR. MUCH OF THE MOISTURE AND FORCING WILL LIKELY OCCUR UNDER THIS UPPER LOW AS IS BEING OBSERVED UPSTREAM...THUS HIGHEST POPS ARE SITUATED OVER NORTHERN LAKE SUPERIOR. THE WARM ADVECTION AHEAD OF THE UPPER LOW COULD ALSO PRODUCE SOME LIGHT SNOW OR FLURRIES...AS GRAND FORKS IS REPORTING AT 3 PM EST. THUS HAVE MAINTAINED AT LEAST 20 POPS FOR MUCH OF THE CWA...EXCEPT NEAR THE WISCONSIN BORDER WHERE THE FORCING IS NOT ENOUGH TO PRODUCE SNOW. IN ADDITION...EARLY IN THE FORECAST SOME LIGHT LAKE EFFECT COULD STILL BE GOING OVER THE FAR EASTERN CWA WHERE WINDS HAVE NOT BACKED TO THE SW YET. THUS 20 POPS REMAIN THERE FOR THE MORNING. ANOTHER CONCERN IS AS THE UPPER LOW MOVES AWAY...LINGERING LOW LEVEL MOISTURE BELOW THE -10C ISOTHERM SITS AROUND...PARTICULARLY IN THE NORTHERN U.P.. SINCE THE WINDS ARE PROGGED OUT OF THE SW...WHICH IS NOT AN UPSLOPE DIRECTION...NO FREEZING DRIZZLE IS MENTIONED. TEMPERATURES SHOULD BE AS WARM AS THEY ARE TODAY OR PERHAPS SLIGHTLY WARMER SINCE 850MB TEMPS ARE PROGGED TO RISE TO -7 TO -9C. .LONG TERM (MONDAY NIGHT THROUGH NEXT SUNDAY)... ECMWF A BIT FARTHER NORTH WITH PAIR OF QUICK MOVING LOW PRESSURE SYSTEMS FOR MON NIGHT AND AGAIN TUE NIGHT INTO WED. GFS WAS A BIT FARTHER SOUTH AND AT THIS POINT WAS NOT PREFERRED. GOING WITH THE FARTHER NORTH SOLUTIONS KEEPS THE BEST CHANCES OF PCPN OVER NORTHERN ZONES INTO LK SUPERIOR. TEMPS IN THE BLYR REMAIN COLD ENOUGH FOR SNOW. HOWEVER...BOTH NAM/GFS SOUNDINGS SHOW LIMITED MOISTURE EXTENDING TO THE -10C ISOTHERM SO FREEZING DRIZZLE IS POSSIBLE AS WELL. LIFT IN THE SHALLOW MOIST LAYER IS MINIMAL...BUT THERE IS ENOUGH OF A CHANCE LATE TUESDAY INTO EARLY WEDNESDAY TO INCLUDE IT FOR AREAS WHERE BLYR WINDS COULD PROVIDE ADDITIONAL UPSLOPE LIFT. FOR THE MOST PART...AFTER LGT PCPN ENDS ON WED...UPPER LEVEL RIDGING LEADS TO QUIET WX ON INTO THU INTO FRI. WARM AIR ADVECTION ALOFT AND EVENTUALLY AT THE SFC COULD LEAD TO SOME SPOTTY LGT PCPN DURING THIS TIME. IF PCPN OCCURS FRI...TEMPS MAY EVEN BE WARM ENOUGH TO JUSTIFY A MIX OF RAIN/SNOW. OTHERWISE...DO EXPECT FAIR AMOUNT OF CLOUDS WITH PERSISTENT INVERSION LIKELY IN PLACE. PRIMARY FOCUS LATE IN THE WEEK INTO NEXT WEEKEND IS HOW FAR NORTH THE STRONG TROF OVER SOUTHERN PLAINS WILL EJECT. HOW THIS TROF PLAYS OUT WILL DETERMINE THE POTENTIAL FOR A SIGNIFICANT STORM SYSTEM OVER THE GREAT LAKES NEXT WEEKEND. A BIT EARLY TO GET WRAPPED UP IN DETAILS...BUT LOW PRESSURE TRACK AND HEAVY SNOW TO THE NORTHWEST OF IT LOOKS LIKE IT WILL SET UP SOMEWHERE OVER THE UPR-CNTRL GREAT LAKES LATE SAT INTO NEXT SUN. INCREASED POPS SOME BUT STILL A CHANCE AT THIS POINT. LATEST ECMWF IS EVEN FARTHER TO THE WEST WITH A POTENTIAL FOR SOME RAIN INTO THE SOUTHEAST CWA BY 12Z SUN. && .AVIATION (FOR THE 18Z TAF ISSUANCE)... KMQT RADAR...SATELLITE IMAGERY AND SURFACE OBS FROM BOTH TAF SITES SHOW LAKE EFFECT SNOWS. WINDS HAVE GENERALLY BEEN NORTH...BUT WILL BACK TO THE NW THIS AFTERNOON AND EVENING AS A RIDGE OF HIGH PRESSURE BUILDS IN FROM MINNESOTA. THIS BACKING OF WIND SHOULD ALLOW VSBYS TO COME UP AT SAW THIS EVENING...WITH CEILINGS PERHAPS GOING VFR BY LATE IN THE NIGHT AS THE RIDGE MOVES OVERHEAD. AT CMX...A NW WIND WILL HELP TO KEEP SNOW GOING THERE...BUT FIGURE THE LOWEST VISIBILITES (PERHAPS AS LOW AS LIFR) WILL OCCUR THIS AFTERNOON WHEN THE FORCING FOR LAKE EFFECT SNOW IS AT ITS GREATEST. BROUGHT VSBYS AND CEILINGS AT CMX TO VFR MON MORNING WHEN THE WINDS TURN TOWARDS THE SOUTH AND ALLOW THE LAKE EFFECT TO EXIT. VFR CEILINGS ARE EXPECTED TO PERSIST THROUGH MON MORNING AT BOTH TAF SITES AS STRATUS COMES IN AHEAD OF LOW PRESSURE MOVING ALONG THE MINNESOTA/ONTARIO BORDER. && .MARINE (FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)... BETWEEN NOW AND WEDNESDAY...TWO LOW PRESSURE AREAS ARE EXPECTED TO MOVE ACROSS LAKE SUPERIOR...ONE ON MONDAY AND THE OTHER TUE NIGHT. HOWEVER...WINDS WILL REMAIN BELOW 30 KT THROUGH WEDNESDAY AS NEITHER SYSTEM IS STRONG ENOUGH TO PRODUCE GALES. A RIDGE OF HIGH PRESSURE WILL THEN BUILD IN FOR THU AND FRI...WHICH SHOULD HELP KEEP WINDS AT OR BELOW 25 KNOTS. && .MQT WATCHES/WARNINGS/ADVISORIES...NONE. && $$ SYNOPSIS/SHORT TERM...AJ LONG TERM...JLA AVIATION/MARINE...AJ mi AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE MARQUETTE MI 107 PM EST SUN DEC 16 2007 UPDATED AVIATION SECTION FOR 18Z TAF ISSUANCE .DISCUSSION... MAIN FCST CONCERNS ARE LES POTENTIAL TODAY AND TONIGHT AND LIGHT SNOW OR FZDZ CHANCES MON AND TUE. WV IMAGERY AND RUC ANALYSIS INDICATED A MID/UPPER LEVEL TROUGH FROM HUDSON BAY TO THE LOWER MS VALLEY...A FLAT RIDGE OVER THE WRN CONUS...AND ANOTHER TROUGH FROM THE GULF OF ALASKA SOUTHWARD. THE NRN STREAM TROUGH AXIS EXTENDED THROUGH WRN ONTARIO INTO NE MN WHILE THE NEXT UPSTREAM SHORTWAVE WAS LOCATED OVER ERN MT. AT THE SFC...A RIDGE EXTENDED FROM MANITOBA THROUGH THE PLAINS BETWEEN A 995 MB LOW OVER WRN OH AND ANOTHER TROUGH/WARM FRONT INTO SRN SASK. A WEAK TROUGH AND BAND OF CLOUDS AND LIGHT SNOW SHOWERS SUPPORTED BY LOW LEVEL CON AND 900-800 MB FGEN WAS ALSO MOVING THROUGH WRN LAKE SUPERIOR. INSTABILITY FOR LES WAS MARGINAL WITH 850 MB TEMPS AROUND -10C. RADAR SHOWED WEAK LES (AOB 15 DBZ) HAD ALSO INCREASED FROM E CNTRL LAKE SUPERIOR TOWARD MARQUETTE IN RESPONSE TO LOW LEVEL CONV WITH WEAK LAKE INDUCED TROF TODAY...EXPECT WINDS TO VEER NRLY AND INCREASE THIS MORNING WITH THE MOST FAVORABLE LOW LEVEL CONV SHIFTING FROM THE WEST TOWARD LOCATIONS EAST OF MARQUETTE THIS AFTERNOON. ALTHOUGH THE LCL HIGH RES WRF/ARW SHOWS THE POTENTIAL FOR A STRONGER LES BAND IN CONVERGENCE AXIS AHEAD OT THE STRONGER N WINDS...CONFIDENCE IN SUCH DETAILS IS LOW. WHILE INSTABILITY MAY BE MARGINAL WITH LAKE-850 MB DELTA/T TO AROUND 15C...FAVORABLE MOISTURE DEPTH/INVERSION HEIGHTS TO 6K-8K FT WITH A DECENT PORTION OF THE CLOUD IN THE FAVORED -12C TO -17C LAYER SHOULD ALLOW FOR DECENT SNOW GROWTH WITH ANY SUSTAINED BANDS. SO...MAINLY JUST SCT -SHSN WITH ACCUMULATIONS AROUND AN INCH WERE MENTIONED WITH LIKELY/NMRS VCNTY KP53 THIS AFTERNOON WHERE ACCUMULATIONS IN THE 1 TO 3 INCH RANGE ARE POSSIBLE. TONIGHT...WINDS WILL SLOWLY BACK TO NW OVER THE E HALF OF THE LAKE. WEAK LAKE INDUCED TROFFING SHOULD KEEP BEST LOW LEVEL CONV FOCUSED INTO THE ERN CWA VCNTY KERY WHERE ADDITIONAL SNOW ACCUMULATIONS OF AN INCH OR TWO ARE EXPECTED. WITH A WEAK RIDGE MOVING THROUGH...EXPECT ENOUGH CLEARING OVER THE INTERIOR WEST FOR TEMPS TO AGAIN DROP BLO GUIDANCE VALUES INTO THE 0 TO -5F RANGE. MON...ALTHOUGH THE NAM MAY BE A BIT WEAK WITH THE MT SHORTWAVE...ITS PATH...FARTHER NORTH THAN THE GFS...IS SUPPORTED BY THE ECMWF AND UKMET. SO...WITH THE BEST 700-500 QVECTOR CONV REMAINING N OF THE CWA...ONLY LOWER END CHANCE POPS SEEM REASONABLE AND MAY NEED TO BE LOWERED/REMOVED IF THE TREND FROM THE NAM HOLDS UP. THE ABUNDANT SFC-925 MB MOISTURE DEPICTED BY THE NAM MAY BE OVERDONE BUT HINTS AT THE POTENTIAL FOR SOME FZDZ WITH THE PRESENCE OF WAA AND 275K-280K ISENTROPIC ASCENT. TUE AND TUE NIGHT...THE GFS WAS ALSO STRONGER AND FARTHER SOUTH WITH THE NEXT SHORTWAVE WHICH MOVES THROUGH THE UPPER GREAT LAKES. THE NAM WAS AGAIN WEAKER AND TOO FAR NORTH COMPARED TO THE FAVORED CANADIAN/ECMWF. LIKE THE MON SYSTEM...THE DEEPER MOISTURE AND BEST CHANCE FOR SNOW IS LIKELY TO REMAIN NORTH OF THE CWA WITH JUST LOWER END POPS FOR UPPER MI. THIS COULD ALSO LEAD TO ANOTHER CHANCE FOR FZDZ WITH MOST OF THE MOISTURE BLO -10C. GIVEN THE AMOUNT OF UNCERTAINTY...WITH THE GFS FAVORING MAINLY SNOW...FZDZ WAS NOT INCLUDED YET. && .AVIATION (FOR THE 18Z TAF ISSUANCE)... KMQT RADAR...SATELLITE IMAGERY AND SURFACE OBS FROM BOTH TAF SITES SHOW LAKE EFFECT SNOWS. WINDS HAVE GENERALLY BEEN NORTH...BUT WILL BACK TO THE NW THIS AFTERNOON AND EVENING AS A RIDGE OF HIGH PRESSURE BUILDS IN FROM MINNESOTA. THIS BACKING OF WIND SHOULD ALLOW VSBYS TO COME UP AT SAW THIS EVENING...WITH CEILINGS PERHAPS GOING VFR BY LATE IN THE NIGHT AS THE RIDGE MOVES OVERHEAD. AT CMX...A NW WIND WILL HELP TO KEEP SNOW GOING THERE...BUT FIGURE THE LOWEST VISIBILITES (PERHAPS AS LOW AS LIFR) WILL OCCUR THIS AFTERNOON WHEN THE FORCING FOR LAKE EFFECT SNOW IS AT ITS GREATEST. BROUGHT VSBYS AND CEILINGS AT CMX TO VFR MON MORNING WHEN THE WINDS TURN TOWARDS THE SOUTH AND ALLOW THE LAKE EFFECT TO EXIT. VFR CEILINGS ARE EXPECTED TO PERSIST THROUGH MON MORNING AT BOTH TAF SITES AS STRATUS COMES IN AHEAD OF LOW PRESSURE MOVING ALONG THE MINNESOTA/ONTARIO BORDER. && .MARINE (FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)... HIGH PRESSURE WILL RESULT IN WINDS AT OR BELOW 30 KNOTS THROUGH THE PERIOD. && .MQT WATCHES/WARNINGS/ADVISORIES...NONE. && $$ DISCUSSION...JLB AVIATION...AJ MARINE...KF mi AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE MARQUETTE MI 620 AM EST SUN DEC 16 2007 UPDATED FOR 12 TAFS .DISCUSSION... MAIN FCST CONCERNS ARE LES POTENTIAL TODAY AND TONIGHT AND LIGHT SNOW OR FZDZ CHANCES MON AND TUE. WV IMAGERY AND RUC ANALYSIS INDICATED A MID/UPPER LEVEL TROUGH FROM HUDSON BAY TO THE LOWER MS VALLEY...A FLAT RIDGE OVER THE WRN CONUS...AND ANOTHER TROUGH FROM THE GULF OF ALASKA SOUTHWARD. THE NRN STREAM TROUGH AXIS EXTENDED THROUGH WRN ONTARIO INTO NE MN WHILE THE NEXT UPSTREAM SHORTWAVE WAS LOCATED OVER ERN MT. AT THE SFC...A RIDGE EXTENDED FROM MANITOBA THROUGH THE PLAINS BETWEEN A 995 MB LOW OVER WRN OH AND ANOTHER TROUGH/WARM FRONT INTO SRN SASK. A WEAK TROUGH AND BAND OF CLOUDS AND LIGHT SNOW SHOWERS SUPPORTED BY LOW LEVEL CON AND 900-800 MB FGEN WAS ALSO MOVING THROUGH WRN LAKE SUPERIOR. INSTABILITY FOR LES WAS MARGINAL WITH 850 MB TEMPS AROUND -10C. RADAR SHOWED WEAK LES (AOB 15 DBZ) HAD ALSO INCREASED FROM E CNTRL LAKE SUPERIOR TOWARD MARQUETTE IN RESPONSE TO LOW LEVEL CONV WITH WEAK LAKE INDUCED TROF TODAY...EXPECT WINDS TO VEER NRLY AND INCREASE THIS MORNING WITH THE MOST FAVORABLE LOW LEVEL CONV SHIFTING FROM THE WEST TOWARD LOCATIONS EAST OF MARQUETTE THIS AFTERNOON. ALTHOUGH THE LCL HIGH RES WRF/ARW SHOWS THE POTENTIAL FOR A STRONGER LES BAND IN CONVERGENCE AXIS AHEAD OT THE STRONGER N WINDS...CONFIDENCE IN SUCH DETAILS IS LOW. WHILE INSTABILITY MAY BE MARGINAL WITH LAKE-850 MB DELTA/T TO AROUND 15C...FAVORABLE MOISTURE DEPTH/INVERSION HEIGHTS TO 6K-8K FT WITH A DECENT PORTION OF THE CLOUD IN THE FAVORED -12C TO -17C LAYER SHOULD ALLOW FOR DECENT SNOW GROWTH WITH ANY SUSTAINED BANDS. SO...MAINLY JUST SCT -SHSN WITH ACCUMULATIONS AROUND AN INCH WERE MENTIONED WITH LIKELY/NMRS VCNTY KP53 THIS AFTERNOON WHERE ACCUMULATIONS IN THE 1 TO 3 INCH RANGE ARE POSSIBLE. TONIGHT...WINDS WILL SLOWLY BACK TO NW OVER THE E HALF OF THE LAKE. WEAK LAKE INDUCED TROFFING SHOULD KEEP BEST LOW LEVEL CONV FOCUSED INTO THE ERN CWA VCNTY KERY WHERE ADDITIONAL SNOW ACCUMULATIONS OF AN INCH OR TWO ARE EXPECTED. WITH A WEAK RIDGE MOVING THROUGH...EXPECT ENOUGH CLEARING OVER THE INTERIOR WEST FOR TEMPS TO AGAIN DROP BLO GUIDANCE VALUES INTO THE 0 TO -5F RANGE. MON...ALTHOUGH THE NAM MAY BE A BIT WEAK WITH THE MT SHORTWAVE...ITS PATH...FARTHER NORTH THAN THE GFS...IS SUPPORTED BY THE ECMWF AND UKMET. SO...WITH THE BEST 700-500 QVECTOR CONV REMAINING N OF THE CWA...ONLY LOWER END CHANCE POPS SEEM REASONABLE AND MAY NEED TO BE LOWERED/REMOVED IF THE TREND FROM THE NAM HOLDS UP. THE ABUNDANT SFC-925 MB MOISTURE DEPICTED BY THE NAM MAY BE OVERDONE BUT HINTS AT THE POTENTIAL FOR SOME FZDZ WITH THE PRESENCE OF WAA AND 275K-280K ISENTROPIC ASCENT. TUE AND TUE NIGHT...THE GFS WAS ALSO STRONGER AND FARTHER SOUTH WITH THE NEXT SHORTWAVE WHICH MOVES THROUGH THE UPPER GREAT LAKES. THE NAM WAS AGAIN WEAKER AND TOO FAR NORTH COMPARED TO THE FAVORED CANADIAN/ECMWF. LIKE THE MON SYSTEM...THE DEEPER MOISTURE AND BEST CHANCE FOR SNOW IS LIKELY TO REMAIN NORTH OF THE CWA WITH JUST LOWER END POPS FOR UPPER MI. THIS COULD ALSO LEAD TO ANOTHER CHANCE FOR FZDZ WITH MOST OF THE MOISTURE BLO -10C. GIVEN THE AMOUNT OF UNCERTAINTY...WITH THE GFS FAVORING MAINLY SNOW...FZDZ WAS NOT INCLUDED YET. && .AVIATION (FOR THE 12Z TAF ISSUANCE)... ACCORDING TO THE LATEST RADAR IMAGES LES HAS ALREADY BEGUN TO SLIDE TOWARDS KSAW...WITH FLURRIES AT MQT NWS THIS MORNING. WINDS WILL BECOME MORE NNW AFTER 12Z INCREASING THE POSSIBILITY OF LES AT BOTH SITES THROUGH THE FIRST 12-18 HOURS OF THE FORECAST. AT THAT POINT WINDS SHIFT ONCE AGAIN BASICALLY CUTTING OFF MUCH OF THE LES ACTIVITY. THIS BREAK FROM THICKER CLOUDS AND SNOW SHOWERS IS EXPECTED TO BE RELATIVELY SHORT LIVED AS A WARM FRONT AND ITS ASSOCIATED LOW PRESSURE SYSTEM SLIDE IN TOWARDS THE END OF OF THE FORECAST PERIOD. && .MARINE (FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)... HIGH PRESSURE WILL RESULT IN WINDS AT OR BELOW 30 KNOTS THROUGH THE PERIOD. && .MQT WATCHES/WARNINGS/ADVISORIES...NONE. && $$ DISCUSSION...JLB AVIATION...KF MARINE...KF mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MARQUETTE MI 500 AM EST SUN DEC 16 2007 .DISCUSSION... MAIN FCST CONCERNS ARE LES POTENTIAL TODAY AND TONIGHT AND LIGHT SNOW OR FZDZ CHANCES MON AND TUE. WV IMAGERY AND RUC ANALYSIS INDICATED A MID/UPPER LEVEL TROUGH FROM HUDSON BAY TO THE LOWER MS VALLEY...A FLAT RIDGE OVER THE WRN CONUS...AND ANOTHER TROUGH FROM THE GULF OF ALASKA SOUTHWARD. THE NRN STREAM TROUGH AXIS EXTENDED THROUGH WRN ONTARIO INTO NE MN WHILE THE NEXT UPSTREAM SHORTWAVE WAS LOCATED OVER ERN MT. AT THE SFC...A RIDGE EXTENDED FROM MANITOBA THROUGH THE PLAINS BETWEEN A 995 MB LOW OVER WRN OH AND ANOTHER TROUGH/WARM FRONT INTO SRN SASK. A WEAK TROUGH AND BAND OF CLOUDS AND LIGHT SNOW SHOWERS SUPPORTED BY LOW LEVEL CON AND 900-800 MB FGEN WAS ALSO MOVING THROUGH WRN LAKE SUPERIOR. INSTABILITY FOR LES WAS MARGINAL WITH 850 MB TEMPS AROUND -10C. RADAR SHOWED WEAK LES (AOB 15 DBZ) HAD ALSO INCREASED FROM E CNTRL LAKE SUPERIOR TOWARD MARQUETTE IN RESPONSE TO LOW LEVEL CONV WITH WEAK LAKE INDUCED TROF TODAY...EXPECT WINDS TO VEER NRLY AND INCREASE THIS MORNING WITH THE MOST FAVORABLE LOW LEVEL CONV SHIFTING FROM THE WEST TOWARD LOCATIONS EAST OF MARQUETTE THIS AFTERNOON. ALTHOUGH THE LCL HIGH RES WRF/ARW SHOWS THE POTENTIAL FOR A STRONGER LES BAND IN CONVERGENCE AXIS AHEAD OT THE STRONGER N WINDS...CONFIDENCE IN SUCH DETAILS IS LOW. WHILE INSTABILITY MAY BE MARGINAL WITH LAKE-850 MB DELTA/T TO AROUND 15C...FAVORABLE MOISTURE DEPTH/INVERSION HEIGHTS TO 6K-8K FT WITH A DECENT PORTION OF THE CLOUD IN THE FAVORED -12C TO -17C LAYER SHOULD ALLOW FOR DECENT SNOW GROWTH WITH ANY SUSTAINED BANDS. SO...MAINLY JUST SCT -SHSN WITH ACCUMULATIONS AROUND AN INCH WERE MENTIONED WITH LIKELY/NMRS VCNTY KP53 THIS AFTERNOON WHERE ACCUMULATIONS IN THE 1 TO 3 INCH RANGE ARE POSSIBLE. TONIGHT...WINDS WILL SLOWLY BACK TO NW OVER THE E HALF OF THE LAKE. WEAK LAKE INDUCED TROFFING SHOULD KEEP BEST LOW LEVEL CONV FOCUSED INTO THE ERN CWA VCNTY KERY WHERE ADDITIONAL SNOW ACCUMULATIONS OF AN INCH OR TWO ARE EXPECTED. WITH A WEAK RIDGE MOVING THROUGH...EXPECT ENOUGH CLEARING OVER THE INTERIOR WEST FOR TEMPS TO AGAIN DROP BLO GUIDANCE VALUES INTO THE 0 TO -5F RANGE. MON...ALTHOUGH THE NAM MAY BE A BIT WEAK WITH THE MT SHORTWAVE...ITS PATH...FARTHER NORTH THAN THE GFS...IS SUPPORTED BY THE ECMWF AND UKMET. SO...WITH THE BEST 700-500 QVECTOR CONV REMAINING N OF THE CWA...ONLY LOWER END CHANCE POPS SEEM REASONABLE AND MAY NEED TO BE LOWERED/REMOVED IF THE TREND FROM THE NAM HOLDS UP. THE ABUNDANT SFC-925 MB MOISTURE DEPICTED BY THE NAM MAY BE OVERDONE BUT HINTS AT THE POTENTIAL FOR SOME FZDZ WITH THE PRESENCE OF WAA AND 275K-280K ISENTROPIC ASCENT. TUE AND TUE NIGHT...THE GFS WAS ALSO STRONGER AND FARTHER SOUTH WITH THE NEXT SHORTWAVE WHICH MOVES THROUGH THE UPPER GREAT LAKES. THE NAM WAS AGAIN WEAKER AND TOO FAR NORTH COMPARED TO THE FAVORED CANADIAN/ECMWF. LIKE THE MON SYSTEM...THE DEEPER MOISTURE AND BEST CHANCE FOR SNOW IS LIKELY TO REMAIN NORTH OF THE CWA WITH JUST LOWER END POPS FOR UPPER MI. THIS COULD ALSO LEAD TO ANOTHER CHANCE FOR FZDZ WITH MOST OF THE MOISTURE BLO -10C. GIVEN THE AMOUNT OF UNCERTAINTY...WITH THE GFS FAVORING MAINLY SNOW...FZDZ WAS NOT INCLUDED YET. && .AVIATION (FOR THE 06Z TAF ISSUANCE)... SAW REMAINS ON THE WRN EDGE OF MSTR THAT ADVECTED ONSHORE EARLIER OFF LK MI...SO A SC DECK/MVFR CIG MAY LINGER THERE THRU THE NGT. IF THE SC BREAKS UP...SOME FOG MAY FORM AS WELL. LATER TNGT...THE ARRIVAL OF A LOW PRES TROF FM THE W/LLVL MSTR AND LO CLDS NOTED OVER MN WL IMPACT CMX FIRST THEN SAW LATER ON. EXPECT LES/LOWER VSBYS TO DVLP AT BOTH SITES AS COLDER AND INITIALLY MOISTER AIR (PER 00Z INL RAOB) IS DRAWN OVER LK SUP BY INCRSG LLVL NW WIND ON THE NW FLANK OF LO PRES MOVING THRU THE LOWER LKS. EXPECT LO CIGS ALL DAY ON SUN AT BOTH SITES WITH LOWER CIGS/VSBY TO IFR AT CMX WITH MORE FVRBL LLVL UPSLOPE FLOW. DEPARTURE OF DEEPER MSTR IN THE AFTN WL ALLOW SN TO DIMINISH AND CONDITIONS TO IMPROVE SOMEWHAT...BUT LO SC DECK/MVFR CIGS LIKELY TO LINGER WITH LLVL MSTR TRAPPED UNDER LO INVRN. && .MARINE (FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)... HIGH PRESSURE WILL RESULT IN WINDS AT OR BELOW 30 KNOTS THROUGH THE PERIOD. && .MQT WATCHES/WARNINGS/ADVISORIES...NONE. && $$ DISCUSSION...JLB AVIATION...KC MARINE...KF mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GRAND RAPIDS MI 423 AM EST SUN DEC 16 2007 LATEST UPDATE...ALL SECTIONS EXCEPT AVIATION... .SYNOPSIS...(423 AM EST SUN DEC 16 2007) A STORM SYSTEM OVER NORTH CENTRAL OHIO WILL MOVE TOWARD THE EAST COAST TODAY. SNOWFALL ACROSS LOWER MICHIGAN WILL GRADUALLY TAPER OFF INTO THE AFTERNOON. HOWEVER...STRONG NORTHWEST WINDS WILL CAUSE CONSIDERABLE BLOWING AND DRIFTING SNOW THROUGHOUT THE DAY. TRAVEL WILL REMAIN HAZARDOUS INTO THIS EVENING. THE WINDS WILL GRADUALLY DIE DOWN TOWARD MIDNIGHT TONIGHT. THE STORM WILL BE FOLLOWED BY RATHER QUIET WEATHER INTO MONDAY AND TUESDAY AS HIGH PRESSURE BRINGS SOME SUNSHINE ALONG WITH SLIGHTLY WARMER TEMPERATURES. && .SHORT TERM...(423 AM EST SUN DEC 16 2007) WILL MAINTAIN CURRENT HEADLINES. THE MAIN QUESTION GOING INTO THE DAYTIME WILL BE THE STRENGTH OF THE WINDS. THE MODEL SOUNDINGS FROM BOTH THE NAM AND GFS SHOW WE MAY TAP INTO 35+ MPH WINDS FOR A PERIOD TODAY. HOWEVER WE NEED 3 OR MORE HOURS OF THIS STRENGTH OF WIND AND FEEL THIS WILL BE A CLOSE CALL OVER THE FAR EASTERN CWA CLOSER TO THE LOW. HAVE NOT SEEN ANY REPORTS OF THIS HIGH OF WIND SO FAR...BUT WITH THE DEEPENING LOW IT COULD BE POSSIBLE TOWARD MID DAY. WILL CONTINUE TO MENTION NEAR BLIZZARD CONDITIONS AT THIS POINT. THE BACK EDGE OF THE INTENSE SNOWFALL WAS ALONG A MUSKEGON TO CLARE LINE AT 0830Z AND SLOWLY PRESSING EAST. WILL KEEP ADDITIONAL SNOWFALL OVER THE NW HALF OF THE CWA INTO THE DAYTIME AT 1 TO 3 INCHES... WHILE THE SE HALF WILL STILL SEE ANOTHER 4 TO 6 INCHES. THIS WILL LEAVE SOME LOCALES IN THE SE CWA WITH A FOOT OR MORE OF SNOW. ALL AREAS WILL SEE THE SNOW TAPERING OFF THROUGH THE AFTERNOON. HOWEVER THE HEADLINES WILL RUN THROUGHOUT THE DAY DUE TO THE STRONG WINDS AND LOW VISIBILITIES DUE TO BLOWING AND DRIFTING SNOW. ATTENTION TURNS TO LAKE EFFECT POTENTIAL TONIGHT AS THE STORM DEPARTS. DELTA T/S WILL BE IN THE MID TEENS ALONG WITH INVERSION HEIGHTS NEAR 8K FT EARLY IN THE EVENING. THERE WILL BE SOME SHEAR INVOLVE DUE TO THE BRISK WINDS THAT WILL ONLY SLOWLY DIMINISH INTO THE EVENING. EXPECT SOME LAKE BANDS WILL BE POSSIBLE TOWARD MIDNIGHT AS THE SHEAR AND WIND RELAXES...HOWEVER WITH THE INVERSION HEIGHTS CRASHING TOWARD DAYBREAK ANY LAKE EFFECT WILL BE SHORT LIVED. WILL MENTION AN INCH OR TWO OF SNOW IN THE FAVORED NW FLOW COUNTIES. FURTHER INLAND TONIGHT...THE BLOWING SNOW WILL GRADUALLY DIMINISH THROUGH THE EVENING. GIVEN THE STRENGTH OF THE WIND SOME SCATTERED LAKE EFFECT SNOW SHOWERS WILL BE POSSIBLE WELL INLAND ALSO THROUGH THE NIGHT BUT ANY ACCUMS WILL BE MINIMAL. A RIDGE OF HIGH PRESSURE MOVES TOWARD THE REGION BY MONDAY WHICH WILL DIMINISH ANY LAKE EFFECT TO FLURRIES. WOULD EXPECT MANY AREAS WILL SEE SOME SUNSHINE AS WARMING BEGINS TO TAKE PLACE ALOFT... ERODING THE LAKE EFFECT CLOUDS INTO THE AFTERNOON. SOUTHERLY WINDS ON TUESDAY WILL HELP PUSH TEMPS TO NEAR OR SLIGHTLY ABOVE THE FREEZING MARK. && .LONG TERM...(423 AM EST SUN DEC 16 2007) ZONAL FLOW REGIME WITH A NORTHERN STREAM SHORTWAVE TROUGH MOVING NORTH OF LOWER MICHIGAN ON TUESDAY NIGHT...BRINGING A CHANCE OF LIGHT SNOW TO THE NORTHERN FORECAST AREA. SHORTWAVE RIDGING RETURNS FOR WEDNESDAY BUT THIS IS SHORT LIVED AS GFS AND ECMWF SHOW PLAINS CYCLOGENESIS ON WEDNESDAY WITH PRECIP ARRIVING BY 12Z THURSDAY AND POSSIBLY PERSISTING INTO FRIDAY. PRECIP TYPE IS AN ISSUE WITH THE 00Z GFS SHOWING SNOW AND THE ECMWF SHOWING RAIN. KEPT THE CURRENT FORECAST GOING FOR RAIN OR SNOW ACROSS THE SOUTHERN FORECAST AREA AND SNOW ACROSS THE NORTH WHICH IS A REASONABLE COMPROMISE. A MORE SIGNIFICANT STORM MAY BE IN THE OFFING FOR SATURDAY AS THE GFS HAS BEEN RATHER CONSISTENT THE PAST FEW DAYS IN SHOWING IMPRESSIVE SFC LOW SPINNING UP AND PASTING US WITH HEAVY QPF NEXT WEEKEND. LATEST ECMWF HAS A WEAKER SYSTEM MISSING US TO THE SOUTH ALTHOUGH EARLIER RUNS ALSO BROUGHT A DEEPER SFC LOW OUR WAY. ADDED CHANCE POPS FOR SNOW SATURDAY GIVEN THE GFS CONSISTENCY AND SINCE WE WERE SURROUNDED BY CHANCE POPS FOR SNOW ON THREE SIDES OF OUR FORECAST AREA. && .AVIATION...(1205 AM EST SUN DEC 16 2007) WIDESPREAD LIFR CONDITIONS IN SNOW EXPECTED OVERNIGHT AS SFC LOW LIFTS TOWARD OHIO AND INTENSIFIES. THE PERIOD OF HEAVIEST SNOW WITH LOWEST CIGS/VSBYS IS EXPECTED TO BE 09Z-16Z WITH IMPROVING CONDITIONS DEVELOPING FROM WEST TO EAST THEREAFTER. HOWEVER EVEN AFTER THE HEAVIEST SNOW MOVES OUT AND CIGS COME UP...VSBYS WILL STILL BE HELD DOWN TO 3-5 MILES (OR POSSIBLY LOWER AT TIMES) BY BLOWING SNOW. SFC WINDS MAY GUST OVER 30 KNOTS AT TIMES ON SUNDAY BEFORE DIMINISHING SUNDAY NIGHT. && .MARINE...(423 AM EST SUN DEC 16 2007) WILL CONTINUE THE GALE WARNING FOR THE ENTIRE NEAR SHORE AS WINDS INCREASE TO AT LEAST 35 KNOTS BY DAYBREAK TODAY AND CONTINUE INTO TONIGHT. RECENT RUC DATA SUGGESTS 45 KNOTS MAY BE SEEN OVER THE SOUTHERN PORTION OF THE LAKE. && .HYDROLOGY...(423 AM EST SUN DEC 16 2007) NO HYDRO ISSUES ANTICIPATED THROUGH THE WEEKEND. NO RISE IN RIVER AND TRIBUTARY LEVELS WILL OCCUR THIS WEEKEND GIVEN AIR TEMPS IN THE MID TO UPPER 20S AND ONLY SNOW PREDICTED. SOME MINOR MELTING IS EXPECTED INTO TUESDAY AS TEMPS WARM INTO THE MID 30S. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...WINTER STORM WARNING MOST OF SW LOWER MI TODAY. SNOW AND BLOWING SNOW ADVISORY NW OF A HARRISON TO WHITEHALL LINE TODAY. LM...GALE WARNING IN EFFECT TODAY THROUGH 1 AM TONIGHT. && $$ SYNOPSIS: JK SHORT TERM: JK LONG TERM: OSTUNO AVIATION: MEADE MARINE: JK HYDROLOGY: JK mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GRAND RAPIDS MI 1205 AM EST SUN DEC 16 2007 LATEST UPDATE...AVIATION... .SYNOPSIS...(340 PM EST SAT DEC 15 2007) LOW PRESSURE DEVELOPING NEAR MEMPHIS WILL TRACK TO NEAR TOLEDO ON SUNDAY. THIS WILL BE A MAJOR WINTER STORM FOR MUCH OF THE REGION. THIS STORM WILL PULL AWAY FROM THE AREA LATER SUNDAY. HIGH PRESSURE WILL BUILD IN FOR MONDAY. && .SHORT TERM...(1011 PM EST SAT DEC 15 2007) WILL MAINTAIN CURRENT HEADLINES. LATEST DATA CONTINUES TO SUGGEST THAT THE HEAVIEST SNOW WILL FALL ACROSS THE SOUTHEASTERN PORTION OF THE CWA...AROUND JXN...WHERE A FOOT OR MORE OF SNOW WILL BE POSSIBLE. SATELLITE PICS SHOW A WELL DEFINED DEFORMATION ZONE WAS COMING TOGETHER TO OUR WEST WITH AN AXIS FROM GRB TO STL. THIS WILL SWING OVER THE AREA...INCREASING THE DEPTH OF THE MOISTURE... PUNCHING UP INTO THE DGZ. 00Z FORECAST SOUNDINGS SHOW AN INTENSE CROSS HAIR OF OMEGA IN THE DGZ BETWEEN 07Z AND 13Z WHEN THE HEAVIEST SNOWFALL WILL OCCUR. SOME AREAS COULD BE PICKING UP TWO OR MORE INCHES PER HOUR IN THIS TIME FRAME. WILL CONTINUE TO MONITOR THE DEVELOPMENT OF THE STORM. THIS WILL INCLUDE THE STRENGTH OF THE WIND THAT IS EXPECTED INTO SUNDAY. NEAR BLIZZARD CONDITIONS WILL BE POSSIBLE WITH STRONG WINDS AND LOW VISIBILITIES DUE TO BLOWING SNOW. && .LONG TERM...(340 PM EST SAT DEC 15 2007) WILL NOT BE ADJUSTING THE LONG TERM SIGNIFICANTLY DUE TO THE PENDING WINTER STORM IN THE SHORT TERM. MAIN WEATHER OF NOTE WILL BE SYSTEM POTENTIALLY AFFECTING THE AREA THU THROUGH EARLY FRI. MODELS HAVE WEAKENED THE SYSTEM FOR NOW AND MOVE IT OUT QUICKER. STILL LOOKS LIKE IT COULD BE A RAIN MAKER...BUT HAVE LEFT THE MIX FOR NOW. && .AVIATION...(1205 AM EST SUN DEC 16 2007) WIDESPREAD LIFR CONDITIONS IN SNOW EXPECTED OVERNIGHT AS SFC LOW LIFTS TOWARD OHIO AND INTENSIFIES. THE PERIOD OF HEAVIEST SNOW WITH LOWEST CIGS/VSBYS IS EXPECTED TO BE 09Z-15Z WITH IMPROVING CONDITIONS DEVELOPING FROM WEST TO EAST THEREAFTER. HOWEVER EVEN AFTER THE HEAVIEST SNOW MOVES OUT AND CIGS COME UP...VSBYS WILL STILL BE HELD DOWN TO 3-5 MILES (OR POSSIBLY LOWER AT TIMES) BY BLOWING SNOW. SFC WINDS MAY GUST OVER 30 KNOTS AT TIMES ON SUNDAY BEFORE DIMINISHING SUNDAY NIGHT. && .MARINE...(340 PM EST SAT DEC 15 2007) WILL CONTINUE THE GALE WARNING FOR THE ENTIRE NEAR SHORE AS WINDS INCREASE TO AT LEAST 35 KNOTS BY DAYBREAK SUNDAY AND CONTINUE INTO SUNDAY NIGHT. RECENT RUC DATA SUGGESTS 40 KNOTS MAY BE TOPPED. && .HYDROLOGY...(340 PM EST SAT DEC 15 2007) NO HYDRO ISSUES ANTICIPATED THROUGH THE WEEKEND. NO RISE IN RIVER AND TRIBUTARY LEVELS WILL OCCUR THIS WEEKEND GIVEN AIR TEMPS IN THE MID TO UPPER 20S AND ONLY SNOW PREDICTED. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...WINTER STORM WARNING MOST OF SW LOWER MI THROUGH SUNDAY. SNOW AND BLOWING SNOW ADVISORY NW OF A HARRISON TO WHITEHALL LINE THROUGH SUNDAY. LM...GALE WARNING IN EFFECT STARTING DAYBREAK SUNDAY. && $$ SYNOPSIS: MJS SHORT TERM: MJS/JK LONG TERM: NJJ AVIATION: MEADE MARINE: MJS HYDROLOGY: MJS mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GRAND RAPIDS MI 1011 PM EST SAT DEC 15 2007 LATEST UPDATE...SHORT TERM... .SYNOPSIS...(340 PM EST SAT DEC 15 2007) LOW PRESSURE DEVELOPING NEAR MEMPHIS WILL TRACK TO NEAR TOLEDO ON SUNDAY. THIS WILL BE A MAJOR WINTER STORM FOR MUCH OF THE REGION. THIS STORM WILL PULL AWAY FROM THE AREA LATER SUNDAY. HIGH PRESSURE WILL BUILD IN FOR MONDAY. && .SHORT TERM...(1011 PM EST SAT DEC 15 2007) WILL MAINTAIN CURRENT HEADLINES. LATEST DATA CONTINUES TO SUGGEST THAT THE HEAVIEST SNOW WILL FALL ACROSS THE SOUTHEASTERN PORTION OF THE CWA...AROUND JXN...WHERE A FOOT OR MORE OF SNOW WILL BE POSSIBLE. SATELLITE PICS SHOW A WELL DEFINED DEFORMATION ZONE WAS COMING TOGETHER TO OUR WEST WITH AN AXIS FROM GRB TO STL. THIS WILL SWING OVER THE AREA...INCREASING THE DEPTH OF THE MOISTURE... PUNCHING UP INTO THE DGZ. 00Z FORECAST SOUNDINGS SHOW AN INTENSE CROSS HAIR OF OMEGA IN THE DGZ BETWEEN 07Z AND 13Z WHEN THE HEAVIEST SNOWFALL WILL OCCUR. SOME AREAS COULD BE PICKING UP TWO OR MORE INCHES PER HOUR IN THIS TIME FRAME. WILL CONTINUE TO MONITOR THE DEVELOPMENT OF THE STORM. THIS WILL INCLUDE THE STRENGTH OF THE WIND THAT IS EXPECTED INTO SUNDAY. NEAR BLIZZARD CONDITIONS WILL BE POSSIBLE WITH STRONG WINDS AND LOW VISIBILITIES DUE TO BLOWING SNOW. && .LONG TERM...(340 PM EST SAT DEC 15 2007) WILL NOT BE ADJUSTING THE LONG TERM SIGNIFICANTLY DUE TO THE PENDING WINTER STORM IN THE SHORT TERM. MAIN WEATHER OF NOTE WILL BE SYSTEM POTENTIALLY AFFECTING THE AREA THU THROUGH EARLY FRI. MODELS HAVE WEAKENED THE SYSTEM FOR NOW AND MOVE IT OUT QUICKER. STILL LOOKS LIKE IT COULD BE A RAIN MAKER...BUT HAVE LEFT THE MIX FOR NOW. && .AVIATION...(710 PM EST SAT DEC 15 2007) WIDESPREAD LIFR CONDITIONS EXPECTED TO DEVELOP BY 06Z OR SOONER AS SFC LOW PRESSURE NEAR MEM LIFTS TOWARD OHIO AND INTENSIFIES. THIS IS WHEN HEAVIER SNOW WILL INCREASE IN COVERAGE. THE PERIOD OF HEAVIEST SNOW WITH LOWEST CIGS/VSBYS IS EXPECTED TO BE 09Z-15Z WITH IMPROVING CONDITIONS DEVELOPING FROM WEST TO EAST THEREAFTER. HOWEVER EVEN AFTER THE HEAVIEST SNOW MOVES OUT AND CIGS COME UP...VSBYS WILL STILL BE HELD DOWN TO 3-5 MILES BY BLOWING SNOW. SFC WINDS MAY GUST OVER 30 KNOTS AT TIME ON SUNDAY. && .MARINE...(340 PM EST SAT DEC 15 2007) WILL CONTINUE THE GALE WARNING FOR THE ENTIRE NEAR SHORE AS WINDS INCREASE TO AT LEAST 35 KNOTS BY DAYBREAK SUNDAY AND CONTINUE INTO SUNDAY NIGHT. RECENT RUC DATA SUGGESTS 40 KNOTS MAY BE TOPPED. && .HYDROLOGY...(340 PM EST SAT DEC 15 2007) NO HYDRO ISSUES ANTICIPATED THROUGH THE WEEKEND. NO RISE IN RIVER AND TRIBUTARY LEVELS WILL OCCUR THIS WEEKEND GIVEN AIR TEMPS IN THE MID TO UPPER 20S AND ONLY SNOW PREDICTED. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...WINTER STORM WARNING MOST OF SW LOWER MI THROUGH SUNDAY. SNOW AND BLOWING SNOW ADVISORY NW OF A HARRISON TO WHITEHALL LINE THROUGH SUNDAY. LM...GALE WARNING IN EFFECT STARTING DAYBREAK SUNDAY. && $$ SYNOPSIS: MJS SHORT TERM: MJS/JK LONG TERM: NJJ AVIATION: MEADE MARINE: MJS HYDROLOGY: MJS mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GRAND RAPIDS MI 340 PM EST SAT DEC 15 2007 LATEST UPDATE...ALL BUT AVIATION... .SYNOPSIS...(340 PM EST SAT DEC 15 2007) LOW PRESSURE DEVELOPING NEAR MEMPHIS WILL TRACK TO NEAR TOLEDO ON SUNDAY. THIS WILL BE A MAJOR WINTER STORM FOR MUCH OF THE REGION. THIS STORM WILL PULL AWAY FROM THE AREA LATER SUNDAY. HIGH PRESSURE WILL BUILD IN FOR MONDAY. && .SHORT TERM... THE TIMING OF THE HEAVY SNOW AND POTENTIAL FOR BLIZZARD CONDITIONS ARE THE MAIN CHALLENGES IN THE SHORT TERM. DECIDED TO START THE WARNING EARLIER. THE MAIN REASON IS THAT THE DRY SLOT IS NOT EVOLVING AS FORECAST...WITH SOME HEAVY SNOW IN EASTERN IA AT 18Z. RADAR TRENDS ACROSS EASTERN MO THROUGH IL SHOW INCREASING PRECIPITATION COVERAGE. VPZ WAS DOWN TO A HALF MILE AT 19Z. THE SURFACE LOW WAS NEAR MEM AT 19Z AND DEEPER THAN ANY MODEL. THIS LOW SHOULD TRACK TO NEAR TOL...WHICH IS FAVORABLE FOR SW LOWER MI TO SEE A WIDESPREAD WARNING EVENT. THE 18Z RUC AND NAM SUPPORT THIS TRACK. STRONGER MID LEVEL FGEN SUPPORTS THE HEAVIEST SNOW SOUTHEAST OF A LINE FROM BIV TO MOP. LOCALLY IN EXCESS OF A FOOT COULD FALL. WILL HOLD OFF ON A BLIZZARD WARNING. WINDS WILL BE ON THE INCREASE LATER TONIGHT INTO SUNDAY. GUSTS OVER 30 MPH ARE LIKELY. THE RECENT RUC RUN SUGGESTS GUSTS WILL STAY UNDER BLIZZARD WARNING CRITERIA. GIVEN THAT THE SNOW WILL BE RELATIVELY DRY...CONSIDERABLE BLOWING AND DRIFTING OF THE SNOW IS EXPECTED. EAST WEST ROADS SHOULD BE ESPECIALLY HARD HIT...PERHAPS IMPASSABLE IN PLACES. && .LONG TERM...(340 PM EST SAT DEC 15 2007) WILL NOT BE ADJUSTING THE LONG TERM SIGNIFICANTLY DUE TO THE PENDING WINTER STORM IN THE SHORT TERM. MAIN WEATHER OF NOTE WILL BE SYSTEM POTENTIALLY AFFECTING THE AREA THU THROUGH EARLY FRI. MODELS HAVE WEAKENED THE SYSTEM FOR NOW AND MOVE IT OUT QUICKER. STILL LOOKS LIKE IT COULD BE A RAIN MAKER...BUT HAVE LEFT THE MIX FOR NOW. && .AVIATION...(1253 PM EST SAT DEC 15 2007) LIGHTER SNOW THAT HAS BEEN OCCASIONALLY FALLING AT THE TAF SITES THIS MORNING IS BEGINNING TO SHIFT NORTH EARLY THIS AFTERNOON AND WILL GIVE EACH OF THE SITES A RELATIVE LULL BEFORE THE HEART OF THE STORM MOVES IN LATER THIS EVENING AND OVERNIGHT TONIGHT. MOST SITES WILL SEE VFR VSBYS AND MVFR CIGS THROUGH AROUND 21Z IN THE LULL. AREA OF LIGHT SNOW NOW DEVELOPING AND MOVING NORTH FROM INDIANA WILL BEGIN TO LOWER VSBYS AND CIGS BEGINNING AROUND 20Z FOR KAZO...KBTL... AND KJXN...AND MOVE NORTH THEREAFTER. SIGNIFICANT SNOWFALL IS EXPECTED TO BEGIN AFTER 03Z FOR THE SRN TAF SITES AND SPREAD ACROSS THE REMAINDER OF THE SITES BY 07Z. FROM THIS PERIOD THROUGH AROUND 15Z SUN LOOKS TO BE THE HEAVIEST SNOWFALL WITH VLIFR CIGS AND VSBYS EXPECTED IN MODERATE TO HEAVY SNOW. WIND GUSTS WILL PICK UP OVERNIGHT AND GUSTS TO 30 KNOTS WILL BE POSSIBLE BY 12Z. SNOW SHOULD TEND TO DIMINISH IN INTENSITY AFTER 15Z...BUT BLOWING AND DRIFTING WILL KEEP VSBYS BELOW 1SM THROUGH THE END OF THE PERIOD. WE HAVE BROUGHT CIGS UP A BIT ONCE THE HEAVIEST SNOW MOVES OUT AFT 15Z. && .MARINE...(340 PM EST SAT DEC 15 2007) WILL CONTINUE THE GALE WARNING FOR THE ENTIRE NEAR SHORE AS WINDS INCREASE TO AT LEAST 35 KNOTS BY DAYBREAK SUNDAY AND CONTINUE INTO SUNDAY NIGHT. RECENT RUC DATA SUGGESTS 40 KNOTS MAY BE TOPPED. && .HYDROLOGY...(340 PM EST SAT DEC 15 2007) NO HYDRO ISSUES ANTICIPATED THROUGH THE WEEKEND. NO RISE IN RIVER AND TRIBUTARY LEVELS WILL OCCUR THIS WEEKEND GIVEN AIR TEMPS IN THE MID TO UPPER 20S AND ONLY SNOW PREDICTED. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...WINTER STORM WARNING MOST OF SW LOWER MI THROUGH SUNDAY. SNOW AND BLOWING SNOW ADVISORY NW OF A HARRISON TO WHITEHALL LINE LATER TONIGHT INTO SUNDAY. LM...GALE WARNING IN EFFECT STARTING DAYBREAK SUNDAY. && $$ SYNOPSIS: MJS SHORT TERM: MJS LONG TERM: NJJ AVIATION: NJJ MARINE: MJS HYDROLOGY: MJS mi AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE MARQUETTE MI 1237 PM EST SAT DEC 15 2007 UPDATED AVIATION DISCUSSION FOR 18Z TAFS .UPDATE... SOUTH FLOW OFF LK MICHIGAN HELPED TO SPREAD FLURRIES FARTHER NORTH INTO MARQUETTE AND ALGER/NORTHERN SCHOOLCRAFT/LUCE COUNTIES. LK EFFECT NEAR LK MICHIGAN VERY TAME WITH QUITE A BIT OF SHEAR IN THE SFC-H85 LAYER. TEMPS AT H85 OF -13C GIVE SUFFICIENT INSTABILITY BUT THE SHEAR AND OVERALL ANTICYCLONIC FLOW IS LIMITING THE SNOW SHOWERS TO MAINLY FLURRIES. DECREASED SKY COVER SOME IN THE WEST CWA BUT OVERALL TEMPS/WINDS/SKY GRIDS ARE IN FINE SHAPE. && .DISCUSSION... MAIN FCST CONCERNS ARE LES CHANCES THROUGH SUN NIGHT AND LIGHT SNOW POTENTIAL MON AND TUE. WV IMAGERY AND RUC ANALYSIS INDICATED A MID LEVEL TROUGH FROM MANITOBA TO THE SRN PLAINS AND ANOTHER TROUGH OFFSHORE FROM THE PAC NW. A WELL-DEFINED BAROCLINIC LEAF WITH SUPPORTING COUPLED UPPER LEVEL JETS WAS ASSOCIATED WITH A BROAD AREA OF PCPN FROM THE PLAINS INTO THE MS VALLEY. A VIGOROUS SHORTWAVE NEAR THE BASE OF THE TROUGH WAS ALSO MOVING OUT OF NM INTO THE TX PANHANDLE. A WEAKER NRN STREAM SHORTWAVE WAS EVIDENT BETWEEN CYQT/KINL. EVEN THOUGH THE LARGE AREA OF PCPN REMAINED WELL TO THE SOUTH OF THE UPPER GREAT LAKES...MID CLOUDS WERE STREAMING INTO THE REGION. AT THE SFC...A RDG EXTENDED FROM WRN QUEBEC INTO WI RESULTING IN ACYC SRLY FLOW THROUGH UPPER MI. RADAR INDICATED WEAK RETURNS(AOB 5 DBZ) OFF OF LK MI BTW KSAW/KESC/KISQ. SO FAR...ONLY FLURRIES WITH 7-10SM VSBY WAS REPORTED AT KISQ/KESC/KERY. SHALLOW INSTABILITY WITH TEMPS OF -14C AT THE TOP OF A 2.5-3.0K FT INVERSION (PER 04Z KPLN TAMDAR SOUNDING) WAS ENOUGH TO SUPPORT THE WEAK LES. TODAY...MDLS SUGGEST SE WINDS OVER NRN LAKE MI WILL VEER TO MAINLY SOUTH MOST OF THE DAY WITH A WEAK RDG AXIS REMAINING IN PLACE BETWEEN THE LOW MOVING INTO THE OH VALLEY AND A TROF OVER CNTRL CANADA. THIS SHOULD KEEP LAKE CLOUDS AND SOME LIGHT LES GOING INTO E CNTRL UPPER MI. SOME INCREASE IN INTENSITY IS POSSIBLE WITH A LONGER FETCH OVER THE LAKE DEVELOPING. HOWEVER...CONTINUED ACYC FLOW AND SHALLOW CONVECTIVE LAYER SUPPORT ONLY CHANCE POPS WITH ANY ACCUMULATIONS MAINLY ALONG THE SHORELINE...OF AN INCH OR LESS. TONIGHT...THE NRN FRINGE OF THE LARGE PCPN SHIELD WITH THE MID MS VALLEY SHORTWAVE AND ASSOCIATED SFC LOW SHOULD REMAIN MAINLY S OF THE CWA BUT MAY BRUSH THE FAR SE TONIGHT. MEANWHILE...A WEAKER NRN STREAM SHORTWAVE WILL MOVE TOWARD THE AREA WITH A DIMINISHING BAND OF LIGHT SNOW. SINCE WINDS WILL REMAIN MAINLY SW AHEAD OF THIS FEATURE...ANY ADDITIONAL LES OVER THE NW WILL HOLD OFF UNTIL LATE TONIGHT WHEN A SFC TROF AND WEAK LOW LEVEL CONV MOVE INTO THE WEST. WITH ONLY WEAK SYNOPTIC SCALE SUPPORT AND 850 MB TEMPS ONLY AROUND -9C...GOING FCST OF CHANCE POPS WITH SNOWFALL AMOUNTS LESS THAN AN INCH STILL SEEMS REASONABLE. SUNDAY AND SUNDAY NIGHT...AFTER THE WEAK TROF MOVES THROUGH NRLY FLOW WILL INCREASE WITH THE WRN LAKES FALLING UNDER THE WRN FRINGE OF THE CIRCULATION AROUND THE ERN CONUS STORM. WITH CAA DROPPING 850 MB TEMPS TO NEAR -12C...EXPECT SCT LIGHT LAKE EFFECT SNOW SHOWERS ACROSS MUCH OF NRN UPPER MI. AGAIN WITH ONLY MARGINAL INSTABILITY...SNOW ACCUMULATIONS OF AROUND AN INCH OR LESS ARE EXPECTED. THE MOST FAVORABLE LOW LEVEL CONVERGENCE SHIFTS FROM BTWN MARQUETTE AND MUNISING LATE SUNDAY TOWARD GRAND MARAIS/NEWBERRY SUNDAY NIGHT. MONDAY INTO TUESDAY...THE GFS/ECMWF SHOW ONE WEAK SHORTWAVE BRUSHING N OF LAKE SUPERIOR MONDAY. MODELS HAVE TRENDED STRONGER AND SLIGHTLY FARTHER S WITH ANOTHER SHRTWV TUE. WITH ONLY SPARSE MOISTURE AVBL...BOTH FEATURES WILL BRING ONLY A CHANCE OF LIGHT SNOW. SOME FZDZ MAY ALSO BE POSSIBLE BOTH LATE MON AND TUE GIVEN WAA AND RELATIVELY MOIST LOW LEVELS AS THE MID LEVEL MOISTURE DEPARTS. MINOR/TRACE PCPN TYPE WAS NOT MENTIONED AT THIS POINT GIVEN UNCERTAINTY WITH THE POSITION AND STRENGTH OF THE SHORTWAVES AND ASSOCIATED MOISTURE PROFILES. && .AVIATION (FOR THE 18Z TAF ISSUANCE)... SOUTHERLY FLOW OFF LK MICHIGAN CONTINUES TO BRING A FEW SNOW SHOWERS INTO KSAW. CONSIDERING IFR VSBY NOW OCCURRING UPSTREAM AT KESC...IT WOULD NOT BE OUT OF THE QUESTION TO SEE A SIMILAR VSBY THIS AFTN...AT LEAST BRIEFLY. A TROUGH CROSSING TONIGHT WILL BRING A CIG BACK TO KCMX THIS EVENING. BY LATE TONIGHT BOTH SITES SHOULD RETURN TO MVFR CONDITIONS WITH OCCASIONAL LK EFFECT SNOW SHOWERS. NNW WIND FAVORS KSAW FOR THE BEST CHANCE OF ANY SIGNIFICANT VSBY REDUCTION ON SUNDAY. && .MARINE (FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)... HIGH PRESSURE WILL RESULT IN WINDS BELOW 25 KNOTS THROUGH THE WEEKEND. IT LOOKS NOW THAT THIS TREND MAY CONTINUE A FEW MORE DAYS...WITH NO GALES FORECAST THROUGH THE PERIOD. && .MQT WATCHES/WARNINGS/ADVISORIES...NONE. && $$ UPDATE...JLA DISCUSSION...JLB AVIATION...JLA MARINE...KF mi AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE MARQUETTE MI 1030 AM EST SAT DEC 15 2007 .UPDATE... SOUTH FLOW OFF LK MICHIGAN HELPED TO SPREAD FLURRIES FARTHER NORTH INTO MARQUETTE AND ALGER/NORTHERN SCHOOLCRAFT/LUCE COUNTIES. LK EFFECT NEAR LK MICHIGAN VERY TAME WITH QUITE A BIT OF SHEAR IN THE SFC-H85 LAYER. TEMPS AT H85 OF -13C GIVE SUFFICIENT INSTABILITY BUT THE SHEAR AND OVERALL ANTICYCLONIC FLOW IS LIMITING THE SNOW SHOWERS TO MAINLY FLURRIES. DECREASED SKY COVER SOME IN THE WEST CWA BUT OVERALL TEMPS/WINDS/SKY GRIDS ARE IN FINE SHAPE. && .DISCUSSION... MAIN FCST CONCERNS ARE LES CHANCES THROUGH SUN NIGHT AND LIGHT SNOW POTENTIAL MON AND TUE. WV IMAGERY AND RUC ANALYSIS INDICATED A MID LEVEL TROUGH FROM MANITOBA TO THE SRN PLAINS AND ANOTHER TROUGH OFFSHORE FROM THE PAC NW. A WELL-DEFINED BAROCLINIC LEAF WITH SUPPORTING COUPLED UPPER LEVEL JETS WAS ASSOCIATED WITH A BROAD AREA OF PCPN FROM THE PLAINS INTO THE MS VALLEY. A VIGOROUS SHORTWAVE NEAR THE BASE OF THE TROUGH WAS ALSO MOVING OUT OF NM INTO THE TX PANHANDLE. A WEAKER NRN STREAM SHORTWAVE WAS EVIDENT BETWEEN CYQT/KINL. EVEN THOUGH THE LARGE AREA OF PCPN REMAINED WELL TO THE SOUTH OF THE UPPER GREAT LAKES...MID CLOUDS WERE STREAMING INTO THE REGION. AT THE SFC...A RDG EXTENDED FROM WRN QUEBEC INTO WI RESULTING IN ACYC SRLY FLOW THROUGH UPPER MI. RADAR INDICATED WEAK RETURNS(AOB 5 DBZ) OFF OF LK MI BTW KSAW/KESC/KISQ. SO FAR...ONLY FLURRIES WITH 7-10SM VSBY WAS REPORTED AT KISQ/KESC/KERY. SHALLOW INSTABILITY WITH TEMPS OF -14C AT THE TOP OF A 2.5-3.0K FT INVERSION (PER 04Z KPLN TAMDAR SOUNDING) WAS ENOUGH TO SUPPORT THE WEAK LES. TODAY...MDLS SUGGEST SE WINDS OVER NRN LAKE MI WILL VEER TO MAINLY SOUTH MOST OF THE DAY WITH A WEAK RDG AXIS REMAINING IN PLACE BETWEEN THE LOW MOVING INTO THE OH VALLEY AND A TROF OVER CNTRL CANADA. THIS SHOULD KEEP LAKE CLOUDS AND SOME LIGHT LES GOING INTO E CNTRL UPPER MI. SOME INCREASE IN INTENSITY IS POSSIBLE WITH A LONGER FETCH OVER THE LAKE DEVELOPING. HOWEVER...CONTINUED ACYC FLOW AND SHALLOW CONVECTIVE LAYER SUPPORT ONLY CHANCE POPS WITH ANY ACCUMULATIONS MAINLY ALONG THE SHORELINE...OF AN INCH OR LESS. TONIGHT...THE NRN FRINGE OF THE LARGE PCPN SHIELD WITH THE MID MS VALLEY SHORTWAVE AND ASSOCIATED SFC LOW SHOULD REMAIN MAINLY S OF THE CWA BUT MAY BRUSH THE FAR SE TONIGHT. MEANWHILE...A WEAKER NRN STREAM SHORTWAVE WILL MOVE TOWARD THE AREA WITH A DIMINISHING BAND OF LIGHT SNOW. SINCE WINDS WILL REMAIN MAINLY SW AHEAD OF THIS FEATURE...ANY ADDITIONAL LES OVER THE NW WILL HOLD OFF UNTIL LATE TONIGHT WHEN A SFC TROF AND WEAK LOW LEVEL CONV MOVE INTO THE WEST. WITH ONLY WEAK SYNOPTIC SCALE SUPPORT AND 850 MB TEMPS ONLY AROUND -9C...GOING FCST OF CHANCE POPS WITH SNOWFALL AMOUNTS LESS THAN AN INCH STILL SEEMS REASONABLE. SUNDAY AND SUNDAY NIGHT...AFTER THE WEAK TROF MOVES THROUGH NRLY FLOW WILL INCREASE WITH THE WRN LAKES FALLING UNDER THE WRN FRINGE OF THE CIRCULATION AROUND THE ERN CONUS STORM. WITH CAA DROPPING 850 MB TEMPS TO NEAR -12C...EXPECT SCT LIGHT LAKE EFFECT SNOW SHOWERS ACROSS MUCH OF NRN UPPER MI. AGAIN WITH ONLY MARGINAL INSTABILITY...SNOW ACCUMULATIONS OF AROUND AN INCH OR LESS ARE EXPECTED. THE MOST FAVORABLE LOW LEVEL CONVERGENCE SHIFTS FROM BTWN MARQUETTE AND MUNISING LATE SUNDAY TOWARD GRAND MARAIS/NEWBERRY SUNDAY NIGHT. MONDAY INTO TUESDAY...THE GFS/ECMWF SHOW ONE WEAK SHORTWAVE BRUSHING N OF LAKE SUPERIOR MONDAY. MODELS HAVE TRENDED STRONGER AND SLIGHTLY FARTHER S WITH ANOTHER SHRTWV TUE. WITH ONLY SPARSE MOISTURE AVBL...BOTH FEATURES WILL BRING ONLY A CHANCE OF LIGHT SNOW. SOME FZDZ MAY ALSO BE POSSIBLE BOTH LATE MON AND TUE GIVEN WAA AND RELATIVELY MOIST LOW LEVELS AS THE MID LEVEL MOISTURE DEPARTS. MINOR/TRACE PCPN TYPE WAS NOT MENTIONED AT THIS POINT GIVEN UNCERTAINTY WITH THE POSITION AND STRENGTH OF THE SHORTWAVES AND ASSOCIATED MOISTURE PROFILES. && .AVIATION (FOR THE 12Z TAF ISSUANCE)... SOUTHERLY FLOW IS BRINGING IN MOISTURE FROM LAKE MICHIGAN...AT LEAST TO SAW...AND AHEAD OF THE DEEPENING SURFACE LOW CURRENTLY OVER OKLAHOMA AND ARKANSAS AT BOTH SITES. EXPECT VFR TO HIGH MVFR CEIGS AND VIS AT SAW THROUGH THE AFTERNOON. AT THAT TIME...WITH THE TROUGH CROSSING TO THE NORTH AND THE STRONG LOW TO THE SOUTHEAST...WINDS WILL BECOME CALM BEFORE BECOMING NORTHERLY LATE IN THE PERIOD. && .MARINE (FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)... HIGH PRESSURE WILL RESULT IN WINDS BELOW 25 KNOTS THROUGH THE WEEKEND. IT LOOKS NOW THAT THIS TREND MAY CONTINUE A FEW MORE DAYS...WITH NO GALES FORECAST THROUGH THE PERIOD. && .MQT WATCHES/WARNINGS/ADVISORIES...NONE. && $$ UPDATE...JLA DISCUSSION...JLB AVIATION...KF MARINE...KF mi AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE MARQUETTE MI 650 AM EST SAT DEC 15 2007 .DISCUSSION... MAIN FCST CONCERNS ARE LES CHANCES THROUGH SUN NIGHT AND LIGHT SNOW POTENTIAL MON AND TUE. WV IMAGERY AND RUC ANALYSIS INDICATED A MID LEVEL TROUGH FROM MANITOBA TO THE SRN PLAINS AND ANOTHER TROUGH OFFSHORE FROM THE PAC NW. A WELL-DEFINED BAROCLINIC LEAF WITH SUPPORTING COUPLED UPPER LEVEL JETS WAS ASSOCIATED WITH A BROAD AREA OF PCPN FROM THE PLAINS INTO THE MS VALLEY. A VIGOROUS SHORTWAVE NEAR THE BASE OF THE TROUGH WAS ALSO MOVING OUT OF NM INTO THE TX PANHANDLE. A WEAKER NRN STREAM SHORTWAVE WAS EVIDENT BETWEEN CYQT/KINL. EVEN THOUGH THE LARGE AREA OF PCPN REMAINED WELL TO THE SOUTH OF THE UPPER GREAT LAKES...MID CLOUDS WERE STREAMING INTO THE REGION. AT THE SFC...A RDG EXTENDED FROM WRN QUEBEC INTO WI RESULTING IN ACYC SRLY FLOW THROUGH UPPER MI. RADAR INDICATED WEAK RETURNS(AOB 5 DBZ) OFF OF LK MI BTW KSAW/KESC/KISQ. SO FAR...ONLY FLURRIES WITH 7-10SM VSBY WAS REPORTED AT KISQ/KESC/KERY. SHALLOW INSTABILITY WITH TEMPS OF -14C AT THE TOP OF A 2.5-3.0K FT INVERSION (PER 04Z KPLN TAMDAR SOUNDING) WAS ENOUGH TO SUPPORT THE WEAK LES. TODAY...MDLS SUGGEST SE WINDS OVER NRN LAKE MI WILL VEER TO MAINLY SOUTH MOST OF THE DAY WITH A WEAK RDG AXIS REMAINING IN PLACE BETWEEN THE LOW MOVING INTO THE OH VALLEY AND A TROF OVER CNTRL CANADA. THIS SHOULD KEEP LAKE CLOUDS AND SOME LIGHT LES GOING INTO E CNTRL UPPER MI. SOME INCREASE IN INTENSITY IS POSSIBLE WITH A LONGER FETCH OVER THE LAKE DEVELOPING. HOWEVER...CONTINUED ACYC FLOW AND SHALLOW CONVECTIVE LAYER SUPPORT ONLY CHANCE POPS WITH ANY ACCUMULATIONS MAINLY ALONG THE SHORELINE...OF AN INCH OR LESS. TONIGHT...THE NRN FRINGE OF THE LARGE PCPN SHIELD WITH THE MID MS VALLEY SHORTWAVE AND ASSOCIATED SFC LOW SHOULD REMAIN MAINLY S OF THE CWA BUT MAY BRUSH THE FAR SE TONIGHT. MEANWHILE...A WEAKER NRN STREAM SHORTWAVE WILL MOVE TOWARD THE AREA WITH A DIMINISHING BAND OF LIGHT SNOW. SINCE WINDS WILL REMAIN MAINLY SW AHEAD OF THIS FEATURE...ANY ADDITIONAL LES OVER THE NW WILL HOLD OFF UNTIL LATE TONIGHT WHEN A SFC TROF AND WEAK LOW LEVEL CONV MOVE INTO THE WEST. WITH ONLY WEAK SYNOPTIC SCALE SUPPORT AND 850 MB TEMPS ONLY AROUND -9C...GOING FCST OF CHANCE POPS WITH SNOWFALL AMOUNTS LESS THAN AN INCH STILL SEEMS REASONABLE. SUNDAY AND SUNDAY NIGHT...AFTER THE WEAK TROF MOVES THROUGH NRLY FLOW WILL INCREASE WITH THE WRN LAKES FALLING UNDER THE WRN FRINGE OF THE CIRCULATION AROUND THE ERN CONUS STORM. WITH CAA DROPPING 850 MB TEMPS TO NEAR -12C...EXPECT SCT LIGHT LAKE EFFECT SNOW SHOWERS ACROSS MUCH OF NRN UPPER MI. AGAIN WITH ONLY MARGINAL INSTABILITY...SNOW ACCUMULATIONS OF AROUND AN INCH OR LESS ARE EXPECTED. THE MOST FAVORABLE LOW LEVEL CONVERGENCE SHIFTS FROM BTWN MARQUETTE AND MUNISING LATE SUNDAY TOWARD GRAND MARAIS/NEWBERRY SUNDAY NIGHT. MONDAY INTO TUESDAY...THE GFS/ECMWF SHOW ONE WEAK SHORTWAVE BRUSHING N OF LAKE SUPERIOR MONDAY. MODELS HAVE TRENDED STRONGER AND SLIGHTLY FARTHER S WITH ANOTHER SHRTWV TUE. WITH ONLY SPARSE MOISTURE AVBL...BOTH FEATURES WILL BRING ONLY A CHANCE OF LIGHT SNOW. SOME FZDZ MAY ALSO BE POSSIBLE BOTH LATE MON AND TUE GIVEN WAA AND RELATIVELY MOIST LOW LEVELS AS THE MID LEVEL MOISTURE DEPARTS. MINOR/TRACE PCPN TYPE WAS NOT MENTIONED AT THIS POINT GIVEN UNCERTAINTY WITH THE POSITION AND STRENGTH OF THE SHORTWAVES AND ASSOCIATED MOISTURE PROFILES. && .AVIATION (FOR THE 12Z TAF ISSUANCE)... SOUTHERLY FLOW IS BRINGING IN MOISTURE FROM LAKE MICHIGAN...AT LEAST TO SAW...AND AHEAD OF THE DEEPENING SURFACE LOW CURRENTLY OVER OKLAHOMA AND ARKANSAS AT BOTH SITES. EXPECT VFR TO HIGH MVFR CEIGS AND VIS AT SAW THROUGH THE AFTERNOON. AT THAT TIME...WITH THE TROUGH CROSSING TO THE NORTH AND THE STRONG LOW TO THE SOUTHEAST...WINDS WILL BECOME CALM BEFORE BECOMING NORTHERLY LATE IN THE PERIOD. && .MARINE (FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)... HIGH PRESSURE WILL RESULT IN WINDS BELOW 25 KNOTS THROUGH THE WEEKEND. IT LOOKS NOW THAT THIS TREND MAY CONTINUE A FEW MORE DAYS...WITH NO GALES FORECAST THROUGH THE PERIOD. && .MQT WATCHES/WARNINGS/ADVISORIES...NONE. && $$ DISCUSSION...JLB AVIATION...KF MARINE...KF mi AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE MARQUETTE MI 1201 AM EST SAT DEC 15 2007 UPDATED FOR 06Z TAFS .UPDATE... LOWERED FCST MIN TEMPS OVER THE KEWEENAW/ARND ERY TO ACCOUNT FOR EARLIER CLRG IN THESE AREAS. BUMPED UP FCST LO TEMPS A FEW DEGREES AND ADDED SOME FLURRIES/ISOLD -SHRA NEAR THE BAY OF GREEN BAY/LK MI W OF ISQ TO ACCOUNT FOR SC NOW IN THIS AREA TRAPPED UNDER LO INVRN SHOWN ON THE 00Z GRB RAOB. RUC13 SHOWS VORTEX DVLPG IN THIS AREA OVERNGT. WITH LARGER SCALE FLOW TENDING TO TURN SE AS HI PRES RDG AXIS DRIFTS ACRS THE FA INTO SE CAN BY 12Z...SOME SHSN MAY DRIFT ONSHORE IN THESE AREAS. KC && .SHORT TERM... LARGE SCALE PATTERN FEATURES TROUGH OVER ROCKIES WITH WSW FLOW INTO THE UPPER GREAT LAKES. TROUGH OVER HUDSON BAY CONTINUES TO PROPEL COLD AIR INTO THE GREAT LAKES. H85 TEMPS -15C TO -20C ARE SLIDING ACROSS LAKE SUPERIOR...SPURRING ON ONGOING LK EFFECT. LACK OF MIDDLE AND HIGH CLOUDS IS ALLOWING VISIBLE SATELLITE TO PROVIDE GOOD LOOK AT THE LK EFFECT. MULTIPLE SNOW SHOWERS ARE IMPACTING NORTHERN KEWEENAW PENINSULA AND NORTH CENTRAL ZONES FM EASTERN MARQUETTE INTO LUCE COUNTIES. MAJORITY OF THE LK EFFECT CLOUD DEPTH WITHIN BETTER TEMPS FOR SNOW GROWTH IS ALLOWING HIGH SNOW TO WATER RATIOS WITH THE SNOW. IN GENERAL...LACK OF DOMINANT BANDING IS NOT ALLOWING ACCUMS MORE THAN A FEW INCHES IN ANY ONE LOCATION. SINCE 950-900MB WINDS REMAIN ONSHORE...EXPECT LIGHT LK EFFECT SNOW SHOWERS TO CONTINUE THROUGH EARLY THIS EVENING. BTWN 03Z-06Z WINDS IN THE LK EFFECT CLOUD LAYER SHOULD BECOME MORE SOUTHERLY AS RIDGE AXIS OVER MN MOVES ACROSS. 280K (800-700MB) ISENTROPIC LIFT ON BACK SIDE OF RIDGE IS DRIVING A SWATH OF MID CLOUDS OVER NORTHERN MN BUT THESE SHOULD NOT IMPACT FORECAST AREA AS THEY STAY TO THE NORTH AND/OR DISSIPPATE. SOME CIRRUS IS STREAMING INTO SOUTHERN MN ATTM TOO...BUT AGAIN MOST OF THIS SHOULD REMAIN OVER WI. CLEARING SKIES AFTER LK EFFECT ENDS...LIGHT WINDS...AND A DRY AIRMASS WITH PWATS AROUND 0.10 COMBINE TO PRODUCE VERY COLD MIN TEMPERATURES TONIGHT. UPSTREAM MINS IN NORTHEAST MN THIS MORNING BOTTOMED OUT IN THE ZERO TO 10 BELOW RANGE WITH COLD SPOTS DOWN TO -25F. EXPECT SIMILAR READINGS OVER CWA...BUT DID GO WITH "WARMER" TEMPS IN THE MIDDLE SINGLE DIGITS CLOSE TO LK SUPERIOR SHORE DUE TO DEVELOPING LAND BREEZES. INCREASING SOUTH/SOUTHEAST FLOW ON SATURDAY ON BACK SIDE OF RIDGE WILL BRING CHANCE OF LK EFFECT OFF LK MICHIGAN. SOUNDINGS SUGGEST MIXED LAYER RISES TO H85...PERHAPS H8. TEMPS AT INVERSION TOP YIELD DELTA T/S OF 17-18C. SOME CONVERGENCE HINTED AT AS WELL OVER SOUTHERN SCHOOLCRAFT COUNTY. MODEL OUTPUT NOT HITTING THIS AREA FOR MUCH QPF/SNOW BUT PATTERN RECOGNITION SUGGESTS ORGANIZED SNOW SHOWERS FM FAR EASTERN DELTA INTO SCHOOLCRAFT COUNTY ARE LIKELY. MAIN INHIBITING FACTOR FOR STRONGER LK EFFECT IS AREA FIRMLY IN GRIP OF HIGH PRESSURE AND ANTICYCLONIC FLOW. WENT WITH LIKELY POPS AND 1-3 INCHES OF ACCUMULATION. IF CONVERGENCE BAND SETS UP RIGHT...COULD SEE EVEN A BIT MORE SNOW. AWAY FM THE LK MICHIGAN SHORE...WX SHOULD BE QUIET WITH JUST INCREASING CLOUDS IN THE AFTN AHEAD OF SFC TROUGH APPROACHING FM THE NORTH. .LONG TERM...PROGRESSIVE PATTERN WILL BRING A SERIES OF WEAK SYSTEMS THROUGH THE REGION THROUGH THE END OF NEXT WEEK. PERIOD BEGINS WITH AN UPPER TROUGH OVER THE CENTRAL PLAINS AND WEAK RIDGING OVER THE WRN/ERN COASTS. INITIAL TROUGH OVER THE CENTRAL PLAINS WILL BRING STRONG LOW PRESSURE SYSTEM TO THE EAST COAST AS IT MOVES EAST ON SAT NIGHT THROUGH SUN NIGHT. SOME ENERGY ASSOCIATED WITH THE MAIN UPPER TROUGH AS IT MOVES THROUGH ON SAT NIGHT AND INTO SUNDAY...BEFORE WEAK RIDGING BUILDS INTO THE AREA FOR SUN AFTN AND EVENING. WINDS TURN FAVORABLE FOR SOME LES ALONG LK SUPERIOR...WITH WINDS TURNING TO 320-330. LIMITING FACTORS ARE THE SHORT RESIDENCE TIME FOR FAVORABLE WINDS...BEFORE THEY BEGIN TO BACK AND WEAKEN AS A WEAK RIDGE MOVES OVER ON SUN AFT TO EVENING. INVERSION HEIGHTS ARE AROUND 3-4KFT...WITH THE TOP OF THE CLOUDS IN THE -12-15C RANGE...SHOULD PROVIDE DECENT SNOW GROWTH AND BRING SOME LIGHT ACCUMULATIONS TO AREAS NEAR LK SUPERIOR. NEXT SHORTWAVE MOVES EAST ALONG THE U.S./CAN BORDER ON SUN NIGHT AND INTO MON. SOME DIFFERENCES IN THE H500 FEATURES AS GFS/ECMWF ARE SIMILAR AND NAM IS FARTHER N. AT THE SFC...WEAK SFC TROUGH PUSHES THROUGH WITH THE WAVE AND EXITS ON MON EVENING. WEAK H850 WAA AND H500-300DIVQ...ALONG WITH DECENT MID-LEVEL MOISTURE AND LAPSE RATES...SHOULD PROVIDE ENOUGH SUPPORT FOR A FEW SNOW SHOWERS ON MONDAY...ESPECIALLY OVER LK SUPERIOR. H500 HEIGHTS BEGIN TO RISE ON MON NIGHT AS ANOTHER WEAK RIDGE BUILDS IN FOR MON NIGHT AND TUES MORN. 00/12Z GFS/ECMWF EJECT NEXT WEAK CLIPPER FOR TUES AFTN THROUGH WED...WITH GFS BEING A LITTLE MORE AMPLIFIED WITH THE H500 WAVE ON THE 00Z RUN. ONCE AGAIN...WITH THE SYSTEM RUNNING ALONG THE U.S./CANADA BORDER...EXPECT MOST OF THE PCPN TO REMAIN OVER OR NEAR LK SUPERIOR. IN ADDITION...WITH H500 HEIGHTS RISING INTO THE MID 540DAMS...AREA MAY SEE SOME ABOVE NORMAL TEMPS AND AROUND FREEZING BY THE MIDDLE OF THE WEEK. BOTH 00/12Z GFS/ECMWF/EFS ENS SHOWING ANOTHER H500 TROUGH AND SFC SYSTEM OVER THE CENTRAL PLAINS FOR THURS/FRI...WHICH MAY BRING SOME PCPN TO THE CWA...ESPECIALLY OVER THE EAST...AS IT LIFTS NE AND INTENSIFIES. && .AVIATION (FOR THE 06Z TAF ISSUANCE)... EXPECT VFR CONDITIONS AT SAW THRU THE NGT...BUT UPSLOPE SLY FLOW OFF LK MI WL ADVECT SC NOW OBSVD NEAR THE BAY OF GREEN BAY UNDER SHARP INVRN DEPICTED ON 00Z GRB RAOB INTO THE AREA EARLY SAT MRNG. GFS/NAM FCST SDNGS HINT THE SC WL LINGER THRU THE DAY BEFORE SOMEWHAT DRIER AIR ARRIVES ON SAT EVNG. EXPECT VFR CONDITIONS TO PREDOMINATE AT CMX THIS FCST PD WITH SSW FLOW BTWN HI PRES TO THE E AND A LOW PRES TROF PUSHING TOWARD THE UPR GRT LKS FM THE W LATE SAT. UPSTREAM AIRMASS ACRS SRN MN IS RATHER DRY PER THE 00Z MPX SDNG...AND MOISTER TRAJECTORIES OFF LK MI WL MISS THE KEWEENAW TO THE E. && .MARINE (FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)... AFTER THE STRONG WINDS THE LAST 24 HRS...WINDS BLO 25 KNOTS THROUGH THE WEEKEND AS HIGH PRESSURE RIDGE OVER MINNESOTA SLOWLY MOVES ACROSS THE REGION. WINDS TO 30 KNOTS POSSIBLE LATE MONDAY INTO TUESDAY IN WAKE OF SFC LOW THAT CROSSES THE LAKE SUPERIOR REGION. AT THIS TIME...NO GALES ARE EXPECTED THROUGH THE PERIOD. && .MQT WATCHES/WARNINGS/ADVISORIES...NONE. && $$ UPDATE...KC SHORT TERM...JLA LONG TERM...SRF AVIATION...KC MARINE...JLA mi AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE GLASGOW MT 942 AM MST SUN DEC 16 2007 .SHORT TERM...FOR NORTHEAST MONTANA...TODAY THROUGH TUESDAY... QUICK UPDATE TO BOOST HIGH TEMPS MOST PLACES TODAY GIVEN LATEST OBSERVED TRENDS. 12Z GGW RAOB CAPTURED A SHALLOW INVERSION AND WITH ABUNDANT INSOLATION THERE SHOULD BE AT LEAST 1K FEET OR SO OF MIXING. LATEST RUC IS MOST REASONABLE WITH THIS SOLUTION AND HAVE TRENDED IN ITS DIRECTION. COUPLE SNOW SHOWERS IN LOWER SASKATCHEWAN PIVOTING AROUND THE 500MB VORT MAX WILL STAY JUST OUTSIDE THE CWA SO HAVE REDUCED CLOUDS IN THIS AREA. MCZ PREVIOUS DISCUSSION... UPPER DISTURBANCE THAT AFFECTED THE AREA SATURDAY NOW MOVING OFF TO THE EAST WITH AN UPPER RIDGE SLATED TO MOVE IN TODAY. STALLED COLD FRONT ACROSS THE NORTHEAST PORTION OF THE CWA SHOULD BE PUSHED OUT TODAY WITH THE INCOMING RIDGE...ALLOWING ALL OF THE CWA TO BE DECENTLY MILD WITH ABOVE NORMAL TEMPERATURES. UPPER RIDGE STAY IS FAIRLY BRIEF AS IT MOVES OFF INTO THE DAKOTAS BY MIDDAY MONDAY AS ANOTHER WEAK SHORTWAVE TROF MOVES INTO WESTERN MONTANA. RELATIVELY MILD AIR REMAIN MONDAY MAKING FOR ANOTHER ABOVE NORMAL TEMPERATURE DAY FOR MOST. MONDAY NIGHT THE AFOREMENTIONED SHORTWAVE TROF MOVES ACROSS THE AREA AS IT WEAKENS. MODELS INDICATING A DEARTH OF MOISTURE WITH THIS FEATURE...IN ADDITION TO IT WEAKENING. WILL THUS LEAVE THE FORECAST DRY. THIS DISTURBANCE DOES PUSH A WEAK COLD FRONT THRU WHICH COOLS THINGS JUST A BIT FOR TUESDAY AS ANOTHER WEAK UPPER RIDGE MOVES IN. IN A NUTSHELL...CONTINUED DRY WITH AT LEAST SLIGHTLY ABOVE NORMAL TEMPERATURES THRU TUESDAY. .LONG TERM...TUESDAY NIGHT THROUGH SUNDAY... THE QUIET WEATHER WE HAD OF LATE TO CONTINUE. A WESTERLY FLOW ALOFT WILL BE KEEPING TEMPS MODERATE AND STILL NO MAJOR WEATHER SYSTEMS IN SIGHT. MODELS HAVE A FEW WEAK DISTURBANCES MOVING ACROSS THE AREA...BUT THE ONLY ONE WORTH ANY POPS WOULD SEEM TO BE THE SYSTEM THAT ARRIVES FROM THE W THU. MOST MODELS HAVE SURFACE LOW MOVING JUST TO OUR N THEN...WITH THE BEST CHANCE OF ANY LIGHT SNOW IN NE MT OCCURRING WITH THE UPPER TROUGH PASSAGE THU NIGHT AND FRI AS A STRONG SPLITTING PATTERN AGAIN LEAVES NE MT IN THE WEAKER NW FLOW ALOFT. TEMPS TYPICALLY WILL BE TOUGHER...BUT MODELS ARE IN PRETTY GOOD AGREEMENT IN HAVING THICKNESSES IN THE 530S WED...THEN FALLING BACK TO THE 510S FRI. WESTERLY FLOW AT ALL LEVELS FOR AWHILE SHOULD PRODUCE TEMPS ABOVE FREEZING FOR MUCH OF THE AREA WED...THEN A WEAK HIGH PRESSURE FROM THE NW BRINGS CLEARING SKIES AND THE COLDEST TEMPS FRI NIGHT...MAINLY SINGLE DIGITS...WITH A FEW PLACES N BELOW ZERO AS 850 MB TEMPS DROP TO -12C IN OUR N. HAVE STAYED FAIRLY CLOSE TO MOS ON TEMPS. THICKNESSES CLIMB BACK TO 530S OR HIGHER WITH UPPER RIDGING TAKING PLACE OVER THE WESTERN STATES SUNDAY. SIMONSEN && .AVIATION... VFR UNDER MOSTLY CLEAR SKIES. WEST WINDS BECOMING GUSTY IN THE LATE MORNING TO EARLY AFTERNOON...THEN DROPPING OFF AROUND SUNSET. RAE && .GLASGOW WATCHES/WARNINGS/ADVISORIES...NONE. && $$ WEATHER.GOV/GLASGOW mt AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE OMAHA/VALLEY NE 1143 AM CST SAT DEC 15 2007 .UPDATE...HAVE LET SNOW ADVIOSRY EXPIRE. && .PREV DISCUSSION... /ISSUED 1057 AM CST SAT DEC 15 2007/ UPDATE...SNOW CONTINUES TO DIMINISH ACROSS THE FORECAST AREA AS DEFORMATION AXIS IS LIKELY STRETCHING. CLEARING LINE HAS ALREADY MOVED INTO NORTHEAST NEB AND WL CONTINUE TO SLIDE SEWD THRU THE DAY. WL LET ADVISORY EXPIRE OVR SRN COUNTIES AT NOON. UPDATED GRIDS OUT SOON. PREV DISCUSSION... /ISSUED 319 AM CST SAT DEC 15 2007/ DISCUSSION... ON-GOING SNOW ACROSS THE CWA...AND ITS AFFECT ON TEMPERATURES OVER THE NEXT SEVERAL DAYS...ARE THE PRIMARY FORECAST CONCERNS. WIDE SWATH OF SNOW DEVELOPED FRIDAY EVENING PRETTY MUCH AS FORECAST...AND CONTINUES THIS MORNING ACROSS MUCH OF THE CWA. REPORTS OF SNOW AMOUNTS HAVE BEEN SPOTTY SO FAR...BUT IT APPEARS THE RANGE IS AROUND 2 INCHES IN THE OMAHA AREA TO 4 OR 5 ALONG THE KANSAS BORDER. LATEST RADAR TRENDS SHOW HIGHEST REFLECTIVITIES SHIFTING FROM OUR SOUTHWEST CWA TO THE EAST AND WAS FOCUSED ACROSS SOUTHEAST NEBRASKA INTO SOUTHWEST IOWA. GFS...NAM...AND RUC MODELS ALL POINTED TO THIS TREND THIS MORNING AND NOW HAVE RADAR TO BACK THEM UP. EVEN THOUGH HEAVIEST SNOW BANDS ARE SHIFTING EAST...WE SHOULD SEE CONTINUED LIGHT SNOW THROUGH MUCH OF THE MORNING WITH APPROACHING VORT MAX FROM THE SOUTHWEST. SATELLITE LOOPS SHOW THIS VORT IN SOUTHWEST KANSAS HEADING NORTHEAST...SO WILL HAVE AT LEAST SEVERAL HOURS OF INDUCED UPWARD MOTION AHEAD OF IT. A CLASSIC DEFORMATION ZONE WAS ALSO NOTED ON SATELLITE LOOPS BISECTING THE CWA FROM SOUTHWEST TO NORTHEAST...WITH A MARKED REDUCTION IN RADAR RETURNS TO THE NORTHWEST OF THE DRY SLOT/DEFORMATION ZONE BOUNDARY. MODELS ARE ALSO IN DECENT AGREEMENT WITH QPF FORECASTS THROUGH 18Z. 06Z TO 12Z FORECASTS ARE ABOUT A TENTH OF AN INCH ALONG THE PLATTE RIVER TO A QUARTER OF AN INCH NEAR THE KANSAS AND MISSOURI STATE LINES....THEN ABOUT A TENTH OF AN INCH BETWEEN 12Z AND 18Z FROM ABOUT INTERSTATE 80 TO THE SOUTHEAST. SO FROM NOW TIL NOON...THIS WOULD EQUATE TO ANOTHER 1 OR 2 INCHES ALONG THE PLATTE RIVER AND INTERSTATE 80 TO ABOUT 2 OR 3 INCHES IN SOUTHEAST NEBRASKA AND SOUTHWEST IOWA. STORM TOTAL SNOW SHOULD RANGE FROM AN INCH OR SO IN NORTHEAST NEBRASKA...2 TO 4 ALONG INTERSTATE 80...AND 4 TO 6 IN SOUTHEAST NEBRASKA AND FAR SOUTHWEST IOWA. WE MAY SEE A COUPLE OF TOTALS COMING IN A BIT HIGHER...BUT WITH STRONGEST LIFT BEGINNING TO WIND DOWN...DO NOT THINK TOTALS WILL GET MUCH HIGHER THAN THOSE JUST MENTIONED. AS UPPER TROUGH SHIFTS EAST TODAY...SNOW SHOULD REALLY BE WINDING DOWN BY EARLY AFTERNOON...WITH LINGERING SNOWS IN THE SOUTHEAST CWA. HAVE BROUGHT AN END TO ALL MENTION OF SNOW BY 00Z. QUESTION THEN TURNS TO TEMPERATURES. FOR TODAY...NORTH WIND...FRESH SNOW AND PLENTY OF CLOUD COVER SHOULD HOLD TEMPS IN THE LOWER 20S AT BEST. CLOUD COVER WILL PLAY A BIG ROLE IN OVERNIGHT LOWS. BOTH NAM AND GFS SHOW LOW CLOUDS SLOWLY WORKING EAST OF THE MISSOURI RIVER BY MORNING WITH LIGHT WESTERLY LOW LEVEL FLOW. EXPECT STRONG LOW LEVEL INVERSION TO SET UP WHEN SKIES CLEAR...SO TEMPS SHOULD REALLY FALL OFF. HAVE ALL LOWS IN THE SINGLE DIGITS...AND HAVE GONE BELOW COLDEST MOS GUIDANCE NUMBERS. WILL LIKELY SEE SOME SUB-ZERO READINGS IN DEEPEST SNOW SUNDAY MORNING. DESPITE NEARLY FULL SUNSHINE ON SUNDAY...WEAK WESTERLY FLOW AND COLD START WILL KEEP TEMPS WELL BELOW GUIDANCE AGAIN. HAVE PUT HIGHS IN THE 20S...BUT AGAIN COULD SEE SOME READINGS HOLD IN THE TEENS. STRONGER SOUTH OR SOUTHWEST FLOW SETS UP FOR EARLY NEXT WEEK AS FAST ZONAL FLOW INDUCES LOWERING PRESSURES IN THE HIGH PLAINS. THE SOUTH WINDS AND SUNSHINE WILL HELP MELT SNOW AND WARM TEMPS...BUT SHOULD SEE LASTING COOL TEMPERATURE BIAS THROUGH THE MIDDLE OF THE WEEK. HAVE LEFT THE REST OF THE FORECAST UNCHANGED. NEXT POTENTIALLY POTENT WEATHER SYSTEM MAY BE ON THE HORIZON FOR SATURDAY AS BOTH GFS AND ECMWF BRING IN A SYSTEM SIMILAR TO OUR CURRENT ONE NEXT SATURDAY. AVIATION... IFR CONDITIONS EXPECTED THROUGH MOST OF THE MORNING AT KOMA AND KLNK WITH MVFR AT KOFK. IMPROVING CONDITIONS DURING THE AFTN AS JET AXIS AND BETTER FORCING SHIFTS EAST. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...NONE. IA...NONE.. && $$ BG ne AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE OMAHA/VALLEY NE 1057 AM CST SAT DEC 15 2007 .UPDATE...SNOW CONTINUES TO DIMINISH ACROSS THE FORECAST AREA AS DEFORMATION AXIS IS LIKELY STRETCHING. CLEARING LINE HAS ALREADY MOVED INTO NORTHEAST NEB AND WL CONTINUE TO SLIDE SEWD THRU THE DAY. WL LET ADVISORY EXPIRE OVR SRN COUNTIES AT NOON. UPDATED GRIDS OUT SOON. && .PREV DISCUSSION... /ISSUED 319 AM CST SAT DEC 15 2007/ DISCUSSION... ON-GOING SNOW ACROSS THE CWA...AND ITS AFFECT ON TEMPERATURES OVER THE NEXT SEVERAL DAYS...ARE THE PRIMARY FORECAST CONCERNS. WIDE SWATH OF SNOW DEVELOPED FRIDAY EVENING PRETTY MUCH AS FORECAST...AND CONTINUES THIS MORNING ACROSS MUCH OF THE CWA. REPORTS OF SNOW AMOUNTS HAVE BEEN SPOTTY SO FAR...BUT IT APPEARS THE RANGE IS AROUND 2 INCHES IN THE OMAHA AREA TO 4 OR 5 ALONG THE KANSAS BORDER. LATEST RADAR TRENDS SHOW HIGHEST REFLECTIVITIES SHIFTING FROM OUR SOUTHWEST CWA TO THE EAST AND WAS FOCUSED ACROSS SOUTHEAST NEBRASKA INTO SOUTHWEST IOWA. GFS...NAM...AND RUC MODELS ALL POINTED TO THIS TREND THIS MORNING AND NOW HAVE RADAR TO BACK THEM UP. EVEN THOUGH HEAVIEST SNOW BANDS ARE SHIFTING EAST...WE SHOULD SEE CONTINUED LIGHT SNOW THROUGH MUCH OF THE MORNING WITH APPROACHING VORT MAX FROM THE SOUTHWEST. SATELLITE LOOPS SHOW THIS VORT IN SOUTHWEST KANSAS HEADING NORTHEAST...SO WILL HAVE AT LEAST SEVERAL HOURS OF INDUCED UPWARD MOTION AHEAD OF IT. A CLASSIC DEFORMATION ZONE WAS ALSO NOTED ON SATELLITE LOOPS BISECTING THE CWA FROM SOUTHWEST TO NORTHEAST...WITH A MARKED REDUCTION IN RADAR RETURNS TO THE NORTHWEST OF THE DRY SLOT/DEFORMATION ZONE BOUNDARY. MODELS ARE ALSO IN DECENT AGREEMENT WITH QPF FORECASTS THROUGH 18Z. 06Z TO 12Z FORECASTS ARE ABOUT A TENTH OF AN INCH ALONG THE PLATTE RIVER TO A QUARTER OF AN INCH NEAR THE KANSAS AND MISSOURI STATE LINES....THEN ABOUT A TENTH OF AN INCH BETWEEN 12Z AND 18Z FROM ABOUT INTERSTATE 80 TO THE SOUTHEAST. SO FROM NOW TIL NOON...THIS WOULD EQUATE TO ANOTHER 1 OR 2 INCHES ALONG THE PLATTE RIVER AND INTERSTATE 80 TO ABOUT 2 OR 3 INCHES IN SOUTHEAST NEBRASKA AND SOUTHWEST IOWA. STORM TOTAL SNOW SHOULD RANGE FROM AN INCH OR SO IN NORTHEAST NEBRASKA...2 TO 4 ALONG INTERSTATE 80...AND 4 TO 6 IN SOUTHEAST NEBRASKA AND FAR SOUTHWEST IOWA. WE MAY SEE A COUPLE OF TOTALS COMING IN A BIT HIGHER...BUT WITH STRONGEST LIFT BEGINNING TO WIND DOWN...DO NOT THINK TOTALS WILL GET MUCH HIGHER THAN THOSE JUST MENTIONED. AS UPPER TROUGH SHIFTS EAST TODAY...SNOW SHOULD REALLY BE WINDING DOWN BY EARLY AFTERNOON...WITH LINGERING SNOWS IN THE SOUTHEAST CWA. HAVE BROUGHT AN END TO ALL MENTION OF SNOW BY 00Z. QUESTION THEN TURNS TO TEMPERATURES. FOR TODAY...NORTH WIND...FRESH SNOW AND PLENTY OF CLOUD COVER SHOULD HOLD TEMPS IN THE LOWER 20S AT BEST. CLOUD COVER WILL PLAY A BIG ROLE IN OVERNIGHT LOWS. BOTH NAM AND GFS SHOW LOW CLOUDS SLOWLY WORKING EAST OF THE MISSOURI RIVER BY MORNING WITH LIGHT WESTERLY LOW LEVEL FLOW. EXPECT STRONG LOW LEVEL INVERSION TO SET UP WHEN SKIES CLEAR...SO TEMPS SHOULD REALLY FALL OFF. HAVE ALL LOWS IN THE SINGLE DIGITS...AND HAVE GONE BELOW COLDEST MOS GUIDANCE NUMBERS. WILL LIKELY SEE SOME SUB-ZERO READINGS IN DEEPEST SNOW SUNDAY MORNING. DESPITE NEARLY FULL SUNSHINE ON SUNDAY...WEAK WESTERLY FLOW AND COLD START WILL KEEP TEMPS WELL BELOW GUIDANCE AGAIN. HAVE PUT HIGHS IN THE 20S...BUT AGAIN COULD SEE SOME READINGS HOLD IN THE TEENS. STRONGER SOUTH OR SOUTHWEST FLOW SETS UP FOR EARLY NEXT WEEK AS FAST ZONAL FLOW INDUCES LOWERING PRESSURES IN THE HIGH PLAINS. THE SOUTH WINDS AND SUNSHINE WILL HELP MELT SNOW AND WARM TEMPS...BUT SHOULD SEE LASTING COOL TEMPERATURE BIAS THROUGH THE MIDDLE OF THE WEEK. HAVE LEFT THE REST OF THE FORECAST UNCHANGED. NEXT POTENTIALLY POTENT WEATHER SYSTEM MAY BE ON THE HORIZON FOR SATURDAY AS BOTH GFS AND ECMWF BRING IN A SYSTEM SIMILAR TO OUR CURRENT ONE NEXT SATURDAY. AVIATION... IFR CONDITIONS EXPECTED THROUGH MOST OF THE MORNING AT KOMA AND KLNK WITH MVFR AT KOFK. IMPROVING CONDITIONS DURING THE AFTN AS JET AXIS AND BETTER FORCING SHIFTS EAST. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...SNOW ADVISORY UNTIL NOON CST TODAY FOR NEZ068-078-088>093. IA...SNOW ADVISORY UNTIL NOON CST TODAY FOR IAZ090-091. && $$ GRIFFIS ne AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE OMAHA/VALLEY NE 319 AM CST SAT DEC 15 2007 .DISCUSSION... ON-GOING SNOW ACROSS THE CWA...AND ITS AFFECT ON TEMPERATURES OVER THE NEXT SEVERAL DAYS...ARE THE PRIMARY FORECAST CONCERNS. WIDE SWATH OF SNOW DEVELOPED FRIDAY EVENING PRETTY MUCH AS FORECAST...AND CONTINUES THIS MORNING ACROSS MUCH OF THE CWA. REPORTS OF SNOW AMOUNTS HAVE BEEN SPOTTY SO FAR...BUT IT APPEARS THE RANGE IS AROUND 2 INCHES IN THE OMAHA AREA TO 4 OR 5 ALONG THE KANSAS BORDER. LATEST RADAR TRENDS SHOW HIGHEST REFLECTIVITIES SHIFTING FROM OUR SOUTHWEST CWA TO THE EAST AND WAS FOCUSED ACROSS SOUTHEAST NEBRASKA INTO SOUTHWEST IOWA. GFS...NAM...AND RUC MODELS ALL POINTED TO THIS TREND THIS MORNING AND NOW HAVE RADAR TO BACK THEM UP. EVEN THOUGH HEAVIEST SNOW BANDS ARE SHIFTING EAST...WE SHOULD SEE CONTINUED LIGHT SNOW THROUGH MUCH OF THE MORNING WITH APPROACHING VORT MAX FROM THE SOUTHWEST. SATELLITE LOOPS SHOW THIS VORT IN SOUTHWEST KANSAS HEADING NORTHEAST...SO WILL HAVE AT LEAST SEVERAL HOURS OF INDUCED UPWARD MOTION AHEAD OF IT. A CLASSIC DEFORMATION ZONE WAS ALSO NOTED ON SATELLITE LOOPS BISECTING THE CWA FROM SOUTHWEST TO NORTHEAST...WITH A MARKED REDUCTION IN RADAR RETURNS TO THE NORTHWEST OF THE DRY SLOT/DEFORMATION ZONE BOUNDARY. MODELS ARE ALSO IN DECENT AGREEMENT WITH QPF FORECASTS THROUGH 18Z. 06Z TO 12Z FORECASTS ARE ABOUT A TENTH OF AN INCH ALONG THE PLATTE RIVER TO A QUARTER OF AN INCH NEAR THE KANSAS AND MISSOURI STATE LINES....THEN ABOUT A TENTH OF AN INCH BETWEEN 12Z AND 18Z FROM ABOUT INTERSTATE 80 TO THE SOUTHEAST. SO FROM NOW TIL NOON...THIS WOULD EQUATE TO ANOTHER 1 OR 2 INCHES ALONG THE PLATTE RIVER AND INTERSTATE 80 TO ABOUT 2 OR 3 INCHES IN SOUTHEAST NEBRASKA AND SOUTHWEST IOWA. STORM TOTAL SNOW SHOULD RANGE FROM AN INCH OR SO IN NORTHEAST NEBRASKA...2 TO 4 ALONG INTERSTATE 80...AND 4 TO 6 IN SOUTHEAST NEBRASKA AND FAR SOUTHWEST IOWA. WE MAY SEE A COUPLE OF TOTALS COMING IN A BIT HIGHER...BUT WITH STRONGEST LIFT BEGINNING TO WIND DOWN...DO NOT THINK TOTALS WILL GET MUCH HIGHER THAN THOSE JUST MENTIONED. AS UPPER TROUGH SHIFTS EAST TODAY...SNOW SHOULD REALLY BE WINDING DOWN BY EARLY AFTERNOON...WITH LINGERING SNOWS IN THE SOUTHEAST CWA. HAVE BROUGHT AN END TO ALL MENTION OF SNOW BY 00Z. QUESTION THEN TURNS TO TEMPERATURES. FOR TODAY...NORTH WIND...FRESH SNOW AND PLENTY OF CLOUD COVER SHOULD HOLD TEMPS IN THE LOWER 20S AT BEST. CLOUD COVER WILL PLAY A BIG ROLE IN OVERNIGHT LOWS. BOTH NAM AND GFS SHOW LOW CLOUDS SLOWLY WORKING EAST OF THE MISSOURI RIVER BY MORNING WITH LIGHT WESTERLY LOW LEVEL FLOW. EXPECT STRONG LOW LEVEL INVERSION TO SET UP WHEN SKIES CLEAR...SO TEMPS SHOULD REALLY FALL OFF. HAVE ALL LOWS IN THE SINGLE DIGITS...AND HAVE GONE BELOW COLDEST MOS GUIDANCE NUMBERS. WILL LIKELY SEE SOME SUB-ZERO READINGS IN DEEPEST SNOW SUNDAY MORNING. DESPITE NEARLY FULL SUNSHINE ON SUNDAY...WEAK WESTERLY FLOW AND COLD START WILL KEEP TEMPS WELL BELOW GUIDANCE AGAIN. HAVE PUT HIGHS IN THE 20S...BUT AGAIN COULD SEE SOME READINGS HOLD IN THE TEENS. STRONGER SOUTH OR SOUTHWEST FLOW SETS UP FOR EARLY NEXT WEEK AS FAST ZONAL FLOW INDUCES LOWERING PRESSURES IN THE HIGH PLAINS. THE SOUTH WINDS AND SUNSHINE WILL HELP MELT SNOW AND WARM TEMPS...BUT SHOULD SEE LASTING COOL TEMPERATURE BIAS THROUGH THE MIDDLE OF THE WEEK. HAVE LEFT THE REST OF THE FORECAST UNCHANGED. NEXT POTENTIALLY POTENT WEATHER SYSTEM MAY BE ON THE HORIZON FOR SATURDAY AS BOTH GFS AND ECMWF BRING IN A SYSTEM SIMILAR TO OUR CURRENT ONE NEXT SATURDAY. && .AVIATION... IFR CONDITIONS EXPECTED THROUGH MOST OF THE MORNING AT KOMA AND KLNK WITH MVFR AT KOFK. IMPROVING CONDITIONS DURING THE AFTN AS JET AXIS AND BETTER FORCING SHIFTS EAST. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...SNOW ADVISORY UNTIL NOON CST TODAY FOR NEZ068-078-088>093. IA...SNOW ADVISORY UNTIL NOON CST TODAY FOR IAZ090-091. && $$ DERGAN/FOBERT ne AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NEWPORT/MOREHEAD CITY NC 1052 AM EST SAT DEC 15 2007 .SYNOPSIS... HIGH PRESSURE BUILDS NORTH OF THE AREA TODAY. RAIN MAY BE HEAVY AT TIMES TONIGHT AS LOW PRESSURE DEVELOPS OVER THE EASTERN CAROLINAS...AND RAPIDLY INTENSIFIES AS IT MOVES UP ALONG THE MID ATLANTIC COAST EARLY SUNDAY. THE LOW WILL SWING A STRONG COLD FRONT ACROSS THE REGION SUNDAY AFTERNOON. COLD HIGH PRESSURE WILL BUILD IN TO THE AREA FROM THE WEST MONDAY AND TUESDAY. THE HIGH WILL MOVE OFF THE COAST WEDNESDAY AND THURSDAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... LATEST OBJECTIVE ANALYSIS INDICATES WEDGE HOLDING STRONG OVER THE CENTRAL PORTION OF THE STATE WITH TEMPS STEADY IN THE MID 40S FAR INLAND WITH LOWER TO MID 50S COAST AND OUTER BANKS. HAVE DECREASED TEMPS TODAY AS LATEST RUC INDICATES THE WEDGE WILL HOLD IN PLACE FOR MUCH OF THE DAY BEFORE WEAKENING THIS EVENING. TEMPS EXPECTED TO RISE ONLY A FEW MORE DEGREES WITH READINGS IN THE UPPER 40S TO NEAR LOWER 50S FAR INLAND MID TO UPPER 50S ALONG THE BEACHES AND OUTER BANKS. NO ADJUSTMENT TO POPS FOR TODAY AS MODELS INDICATE LIGHT PRECIP BREAKING OUT THIS AFTERNOON FROM SOUTH TO NORTH AS ISENTROPIC LIFT INCREASING ACROSS THE AREA. && .SHORT TERM /6 PM THIS EVENING THROUGH MONDAY/... PCPN WILL BECOME HEAVY AT TIMES TNGT WITH ENHANCEMENT BY JET DYNAMICS AND DEEP MOISTURE INFLOW. PRECIP WATRS INCREASING TO NEAR 2 INCHES AND EXPECTING RAINFALL TOTALS GENERALLY ONE TO ONE HALF INCH WITH LOCALLY HIGHER AMOUNTS PSBL BY THE TIME PCPN COMES TO AN END SUN MORN. VERY HIGH SHEAR/HELICITY VALUES TNGT SUGGS ROTATING STORMS LIKELY BUT WEAK INSTABILITY MAY INHIBIT ABILITY TO TAP HIGHER WINDS ALOFT. WHILE SPC SLIGHT RISK SVR AREA STOPS JUST SW OF MHX FCST AREA...CANT RULE OUT ISOLATED STRONG/SVR WIND GUST OR EVEN A TORNADO OR TWO DURING THE OVRNGT HOURS. TEMPS NEARLY STEADY THIS EVE THEN RISING OVRNGT NIGHT AS CSTL/WARM FRONT LIFTS NORTH OF THE AREA. SHOWERS LINGERING THRU SUNRISE THEN QUICKLY ENDING FROM WEST TO EAST AS SFC COLD FRONT/MID LVL DRY SLOT MOVE TWD COAST. QUITE GUSTY SUNDAY AS INCRSD BNDRY LAYER MIXING PULLS DOWN STRONG WEST WINDS. THE WARMING LOW-MID LEVEL DOWNSLOPING FLOW WILL ALLOW TEMPS TO RISE TO THE U50S/L60S TO PSBLY M60S BEFORE STRONG DEEP CAA SETS IN LATE IN THE DAY AND INTO SUNDAY NIGHT. CONTD MIXING IN THE BNDRY LAYER WONT ALLOW FULL DROP OF TEMPS SUNDAY NIGHT BUT IT`LL REMAIN BRISK WITH LOWS GENERALLY IN THE 30S BY MON MORN. COLD HIGH PRES BUILDS INTO AREA EARLY NEXT WEEK WITH HIGHS ON MONDAY ONLY REACHING TO NEAR 50 DEGS. && .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... QUIET EXTENDED FORECAST WITH HIGH PRESSURE OVER THE AREA TUESDAY THROUGH THURSDAY. AFTER A COLD MON NIGHT-TUESDAY...TEMPS REBOUNDING CLOSE TO CLIMO FOR THE MID TO LATE WEEK PERIOD. GFS/ECMWF SHOWING SIMILAR SOLUTIONS FOR FRIDAY...BOTH HAVE SFC LOWS DEVELOPING AND MOVING INTO THE MID ATLANTIC. GFS AND HPC SHOW EASTERN NC IN THE WARM SECTOR FRIDAY AFTERNOON AND COLD FRONT PUSHING OFF THE COAST LATE FRIDAY. HAVE PUT SLIGHT CHANCE POPS IN FORECAST FOR FRIDAY. && .AVIATION /16Z SATURDAY THROUGH WEDNESDAY/... EXPECT CONDITIONS TO CONTINUE TO DETERIORATE WITH A LOWERING OF CONDITIONS FROM MVFR THIS AFTERNOON TO IFR/LIFR OVERNIGHT-EARLY SUNDAY. WINDS WILL ALSO BE INCREASING WITH GUSTS TO AT LEAST 30 KT EXPECTED OVERNIGHT AND SUNDAY. EVEN HIGHER GUSTS POSSIBLE IN ANY CONVECTION THAT OCCURS WHICH IS LOOKING MORE PROBABLE AS WARM/UNSTABLE AIR ADVECTS INTO THE REGION TONIGHT. HEAVY RAINS WILL ALSO OCCUR AS TROPICAL MOISTURE FLOWS INTO THE AREA AHEAD OF A DEVELOPING AREA OF LOW PRESSURE/STRONG COLD FRONT. THE RAINS WILL BECOME WIDESPREAD AFTER 00Z. WE ARE EXPECTING IMPROVEMENT AFTER 18Z SUNDAY WITH THE PASSAGE OF A STRONG COLD FRONT AND A STRONG INTRUSION OF COLD/DRY AIR INTO THE AREA. STRONG WINDS 30-35 KT WILL POSSIBLE THROUGH MID SUNDAY EVENING AS THE ADVECTION OF COLDER AIR DESTABILIZES THE LOW LEVELS AND PROMOTES MIXING OF STRONGER WINDS ALOFT TO THE SURFACE. HIGH PRES WILL BUILD IN OVER THE REGION MONDAY AND REMAIN THROUGH MID WEEK WITH MAINLY VFR CONDITIONS EXPECTED. && .MARINE... DANGEROUS MARINE CONDITIONS WITH GALE/STORM FORCE CONDITIONS/STRONG TO SEVERE THUNDERSTORMS AND DANGEROUS SEAS EXPECTED...ESPECIALLY TONIGHT INTO SUNDAY. THE GALE FORCE WINDS WILL PERSIST THROUGH SUNDAY EVENING BEFORE SUBSIDING MONDAY AS THE HIGH BUILDS OVER THE AREA. NO CHANGES NEEDED TO CURRENT MARINE FORECASTS AS SMALL CRAFT ADVISORY CONDITIONS THIS AFTERNOON BECOME GALE/STORM THIS EVENING AND SUNDAY. UNSTABLE/TROPICAL AIR WILL DRAWN INTO THE AREA TONIGHT INTO SUNDAY WHICH WILL PRODUCE THUNDERSTORMS WITH WIND GUSTS IN EXCESS OF 50 KT AND WATERSPOUTS. THE STRONG GRADIENT WINDS WILL BUILD SEAS TO 13-16 FT BY SUNDAY MORNING. WE USED A BLEND OF THE WAVE WATCH AND SWAN MODELS WITH A NOD TOWARD THE HIGHER SWAN MODEL SEAS SINCE WE ARE FORECASTING HIGHER WIND SPEEDS THAN DEPICTED IN THE OPERATIONAL GFS MODEL. FOR NOW WON`T WORRY ABOUT HIGH SURF SINCE THE PERIOD OF PEAK ONSHORE SE FLOW WILL BE DURING LOW TIDE AROUND 530 AM...AND BY THE TIME HIGH TIDE ROLLS AROUND THE WINDS WILL HAVE SHIFTED TO THE SW/W. THE TURNING OF THE WINDS WILL ALSO HELP AND PREVENT SIG SOUND SIDE FLOODING ALONG THE OBX. CAN`T RULE OUT 2FT WATER RISES...BUT NOT HIGH ENOUGH TO ISSUE A CFS. THE WIND POTENTIAL REMAINS HIGH...ESP WITH GUSTS AS AREA BECOMES UNSTABLE LATE TNT AND EARLY SUN. WITH STRONG LOW LVL JET FEEL HIGH WINDS ALONG OBX LIKELY...AND LOCALIZED WIND ADV CRITERIA ALONG REMAINING EASTERN COASTAL COUNTIES. HAVE KEPT ONSLOW OUT SINCE IT LOOKS TO BE MORE STABLE THAN COUNTIES EAST OF THERE AND GUST POTENTIAL LESS. FOR CARTERET THE STRONGEST WINDS WILL BE DOWN EAST. AIRMASS WILL BECOME STABLE SUN AFT...THEN WILL SEE BREEZY CONDITIONS DUE TO CAA. WINDS WILL REMAIN BREEZY INTO SUN NT...BUT WILL CONTINUE TO WEAKEN INTO MON AS HIGH PRES BUILDS IN. FOR THE REST OF THE FCST HAVEN`T CHANGED MUCH FROM PREV FCST AS FOCUS HAS BEEN ON WEEKEND STORM. OVERALL LOOKING AT HIGH PRES AND NO SIG SEAS/WIND EVENTS IN FCST. && .MHX WATCHES/WARNINGS/ADVISORIES... NC...HIGH WIND WARNING FROM 7 PM THIS EVENING TO 7 PM EST SUNDAY FOR NCZ103-104. WIND ADVISORY FROM 7 PM THIS EVENING TO 7 PM EST SUNDAY FOR NCZ047-080-081-093>095. MARINE...GALE WARNING FROM 7 PM THIS EVENING TO 1 AM EST MONDAY FOR AMZ130-135-150-156-158. STORM WARNING FROM 1 AM TO 4 PM EST SUNDAY FOR AMZ152-154. && $$ SYNOPSIS...BTC NEAR TERM...JW SHORT TERM...BTC LONG TERM...BTC/CLQ AVIATION...JME MARINE...JME nc AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 1010 AM EST SAT DEC 15 2007 .SYNOPSIS...HIGH PRESSURE CENTERED OVER NEW ENGLAND WILL PUSH COLDER AIR SOUTHWARD INTO THE REGION TODAY... AS A DEVELOPING LOW PRESSURE SYSTEM APPROACHES FROM THE GULF STATES. INTENSE LOW PRESSURE WILL MOVE QUICKLY UP THE COAST AND AWAY ON SUNDAY... WITH GUSTY WEST WINDS IN ITS WAKE. HIGH PRESSURE WILL BUILD OVER THE AREA MONDAY AND TUESDAY. && .NEAR TERM /THROUGH TODAY/... AS OF 1000 AM SATURDAY... ISENTROPIC UPGLIDE AT 285K-295K IS WELL UNDERWAY WITH PLENTIFUL MOISTURE IN THE LOW LEVELS AND A GOOD ONSHORE WIND COMPONENT AROUND 925 MB... HOWEVER THIS LIFT IS BEING TEMPERED A BIT BY DIFFLUENT FLOW NOTED ON THE 12Z 850 MB ANALYSIS. SHOWERS HAVE BEEN RATHER PATCHY THUS FAR AND HAVE DELAYED THE ONSET OF STEADIER RAIN FOR ANOTHER COUPLE OF HOURS FROM THE CURRENT FORECAST. RUC13 DATA SHOWS LOW LEVEL MOISTURE TRANSPORT INCREASING STEADILY THROUGH 18Z AND WE SHOULD SEE COVERAGE FILL IN CONSIDERABLY BY MID AFTERNOON. HAVE MADE ALTERATIONS TO HOURLY TEMPERATURES AND DEWPOINTS TO REFLECT CURRENT TRENDS OF NEAR STEADY READINGS IN THE TRIAD AS THE COLD 1039 MB WEDGING HIGH NOSES SOUTH. HAVE ALSO RAISED TEMPS OVER THE SOUTHEAST BASED ON WARMER THAN EXPECTED READINGS... OTHERWISE EXPECT LARGELY STEADY TEMPS THROUGH THE DAY. OTHER MINOR ADJUSTMENTS WERE MADE TO INCREASE NORTHEASTERLY WINDS WITH MANY SITES REPORTING GREATER THAN 12 MPH SUSTAINED ALREADY. -GIH && .SHORT TERM /TONIGHT THROUGH MONDAY NIGHT/... AS OF 230 AM SATURDAY...MODELS DEPICT A MILLER-B SCENARIO WITH A SECONDARY LOW FORMATION NEAR THE CAROLINAS COAST OVERNIGHT PUSHING A COASTAL WARM FRONT INLAND TO NEAR THE EASTERN BORDER OF THE RAH CWA IN THE LOWER COASTAL PLAIN. MODELS SOUNDINGS SHOW DESTABILIZATION AND POSITIVE ENERGY ALOFT FOR A THREAT OF ISOLATED TSTMS IN EASTERN BORDER COUNTIES IN ADDITION TO WIDESPREAD RAIN THROUGHOUT THE AREA OVERNIGHT. GREATEST LARGE SCALE LIFT APPEARS EARLY TONIGHT AS A 40 KNOT EASTERLY FLOW VEERS INTO A 50 KNOT SOUTHERLY FLOW WITH SATURATED AIR IN THE LOWEST 6000 FEET. MODELS DIFFER ON PLACEMENT OF HEAVIEST RAINFALL AND IT MAY ULTIMATELY DEPEND ON HOW CONVECTIVE ELEMENTS ALIGN WITH THE SECONDARY LOW AND WARM FRONT. CURRENT THINKING IS SIMILAR TO PREVIOUS IN SHOWING BASIN AVERAGE STORM TOTAL QPF INCREASING FROM WEST TO EAST AND RANGING FROM NEAR 0.75 TO NEAR 1.20. TEMPERATURES WILL SHOW A NON DIURNAL PATTERN OF NEARLY STEADY TO SLOWLY RISING VALUES OVERNIGHT. SUNDAY...THE MAIN SURFACE TROUGH AND COLD FRONTAL JUMP TO THE COAST OCCURS MID MORNING WITH CHANCES OF SHOWERS RAPIDLY DECREASING SW TO NE MID TO LATE MORNING. BY AFTERNOON...IN THE WAKE OF THE DEPARTING LOW...THE SURFACE PRESSURE GRADIENT TIGHTENS TO NEARLY 20 MB ACROSS THE STATE WITH THE ARRIVAL OF COLDER AIR. THE -8C ISOTHERM AT 850 MB ADVECTS INTO THE AREA BY EVENING. THIS SUGGESTS STRONG GUSTY WINDS FROM THE WNW IN THE AFTERNOON WITH POTENTIAL GUSTS NEAR 40 MPH AND SUSTAINED WINDS OF 20-30 MPH. WIND ADVISORIES ARE LIKELY. SUNSHINE WILL STRUGGLE AGAINST COLD AIR ADVECTION TO RAISE TEMPERATURES AN A NET RESULT MAY BE NEAR STEADY READINGS BETWEEN 45 AND 55 NW TO SE DURING THE MIDDAY AND AFTERNOON HOURS. SUNDAY NIGHT-MONDAY NIGHT...A THERMAL TROUGH CROSSES THE AREA DURING THE PERIOD AS SURFACE HIGH PRESSURE MOVES FROM THE SOUTHERN PLAINS TO THE MID ATLANTIC COAST. LOWS SHOULD DIP INTO THE 20S BOTH NIGHTS BENEATH CLEAR SKIES...POSSIBLY LOWER 20S MON NIGHT. HIGHS MONDAY MAY BE LIMITED TO MID 40S OR LOWER GIVEN MODEL 1000-850 THICKNESS IN THE 1275-1285 METER RANGE. -RFG && .LONG TERM /TUESDAY THROUGH FRIDAY/... AS OF 325 AM SATURDAY...BROAD ZONAL FLOW WITH HIGH PRESSURE SLOWLY SHIFTING EAST OF THE REGION WILL RESULT IN MODERATING TEMPERATURES BY WEDNESDAY. TUESDAY WILL BE ANOTHER CHILLY DAY WITH HIGHS IN THE 50-54 DEGREE RANGE WITH LOWS TUESDAY NIGHT BACK DOWN INTO THE UPPER 20S. WEDNESDAY WILL ADD ON ABOUT 5 DEGREES TO THE TUESDAY READINGS AS LIGHT SOUTHERLY FLOW DEVELOPS. MEDIUM RANGE GUIDANCE REMAINS IN FAIRLY GOOD AGREEMENT ON OUR NEXT CHANCE OF RAIN COMING THURSDAY NIGHT INTO FRIDAY AS SHORTWAVE ENERGY MOVING ACROSS THE WEST COAST QUICKLY ADVANCES EAST IN THE FAST ZONAL FLOW. SOME DIFFERENCES HAVE BEGUN TO SHOW UP BETWEEN THE ECMWF AND THE GFS IN REGARDS TO THE STRENGTH OF THIS SYSTEM. THE ECMWF MAINTAINS IT SOLUTION OF A MORE AMPLIFIED TROUGH AND RESULTANT MILLER B CYCLOGENESIS OFF THE NC COAST BY FRIDAY MORNING. THE GFS IS MUCH LESS AMPLIFIED AND FURTHER NORTH WITH CYCLOGENESIS. THERE WILL LIKELY BE MODEL DIFFERENCES UNTIL THE ENERGY IN QUESTION MOVES ASHORE AND CAN BE BETTER ASSESSED BY THE RAOB NETWORK. WILL CARRY CHANCE POPS FOR NOW ON THURSDAY NIGHT...LINGERING INTO FRIDAY MORNING. NEAR TO SLIGHTLY ABOVE NORMAL TEMPS EXPECTED FOR THE END OF THE WEEK DUE TO THE AIRMASS BEHIND THE END OF THE WEEK SYSTEM BEING PRIMARILY OF PACIFIC ORIGIN. && .AVIATION /12Z SATURDAY THROUGH WEDNESDAY/... AS OF 640 AM...WIDESPREAD LOW STRATUS HAS DEVELOPED ACROSS CENTRAL NORTH CAROLINA EARLY THIS MORNING IN RESPONSE TO INCREASED ISENTROPIC LIFT. LIFT WILL CONTINUE TO INCREASE TODAY AS A STORM SYSTEM ORGANIZES OVER THE LOWER MISSISSIPPI VALLEY AND MOVES TOWARD THE REGION. THIS WILL RESULT IN IFR CEILINGS AT ALL SITES BY MIDDAY ALONG WITH THE DEVELOPMENT OF LIGHT RAIN WHICH COULD PRODUCE MVFR VSBYS. A SURFACE LOW WILL DEVELOP ALONG THE NORTH CAROLINA COAST THIS EVENING. WIDESPREAD RAIN AND IFR TO OCCASIONALLY LIFR CONDITIONS WILL AFFECT THE CENTRAL NC TERMINALS AS A RESULT. HAVE INCLUDED A MENTION OF CB IN THE SKY CONDITION AT RWI GIVEN THE COASTAL FRONT WILL LIKELY MOVE PAST RWI...PLACING THEM IN THE WARM SECTOR WHICH WILL BE FAVORABLE FOR ISOLATED THUNDER. WINDS WILL ALSO LIKELY VEER TO THE ESE/SE AT RWI LATER TONIGHT WITH THE PASSAGE OF THE COASTAL FRONT. THE WIND FORECAST AT FAY/RDU IS A LITTLE MORE TRICKY GIVEN THAT A SMALL DEVIATION IN THE MOVEMENT OF THE COASTAL FRONT WILL RESULT IN MUCH DIFFERENT WIND DIRECTIONS. THE COOL AIR WEDGE SHOULD HOLD FIRM AT INT/GSO TO MAINTAIN A NE WIND. LLWS WILL ALSO BE A CONCERN TONIGHT AS WINDS NEAR 2000 FT INCREASE TO 40-45 KT. CONDITIONS WILL RAPIDLY BECOME VFR BY MIDDAY SUNDAY AS THE SURFACE LOW MOVES NORTHEAST AND DEEPENS OVER NEW ENGLAND...PRODUCING A STRONG WESTERLY FLOW OVER THE CAROLINAS. THERE WILL BE THE POTENTIAL FOR WINDY CONDITIONS ON SUNDAY DUE TO THE DEEPENING LOW AND VERY STRONG WINDS IN THE MIXED LAYER. SUSTAINED WINDS OF 20 TO 25 KNOTS WITH WIND GUSTS OF 30 40 KNOTS ARE LIKELY BEFORE SUNDAY AFTERNOON. THE WIND DIRECTION WILL BE VEERING TO WESTERLY WHICH WILL PRODUCE SOME CROSSWIND IMPACTS AT THE LOCAL TERMINALS. WINDS WILL DIMINISH AS HIGH PRESSURE BUILDS TOWARD NORTH CAROLINA FROM THE WEST LATE SUNDAY NIGHT RESULTING IN VFR CONDITIONS INTO WEDNESDAY. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...RFG NEAR TERM...RFG/HARTFIELD SHORT TERM...RFG LONG TERM...JFB AVIATION...JFB nc AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC 642 PM EST SAT DEC 15 2007 .SYNOPSIS... A DEEPENING LOW PRESSURE SYSTEM WITH A COLD FRONT IN TENNESSEE WILL SWING ACROSS THE CAROLINAS TONIGHT. A RIDGE OF COLD AND DRY HIGH PRESSURE WILL THEN SETTLE OVER THE SOUTHEAST STATES MONDAY AND PERSIST UNTIL ANOTHER COLD FRONT APPROACHES THE AREA LATE IN THE WEEK. && .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/... AS OF 230 PM SATURDAY...A MILLER-B LOW PRESSURE SYSTEM WITH ONGOING CAD WILL BE THE MAIN WEATHER FEATURES FOR THIS EVENING AND TONIGHT. A STRONG WARM NOSE ABOVE THE DOME OF COLD AIR HAS TEMPERATURES FROM 5-10C (WHICH SHOULD KEEP ALL PRECIP AS RAIN THROUGH LATE TONIGHT. STRONG WAA FORCING WITH DECENT MOISTURE TRANSPORT IS RESULTING IN AREAS OF LIGHT RAIN AND SOME EMBEDDED THUNDER TO DEVELOP TO THE SOUTH OF OUR CWFA. ALL SHORT RANGE GUIDANCE INDICATES THE STRONGEST OMEGA WILL LIKELY OCCUR FROM 00Z-06Z SUNDAY. I HAVE NEAR 100 PCT POP FOR THE ENTIRE CWFA DURING THAT PERIOD. I ADJUSTED HPC QPF ACCUMS THROUGH 12Z SUNDAY GIVING QPF WITH RANGE FROM 0.5-1.0". WITH SOME THUNDER IN NORTHERN GA AND MSAS/RUC LI`S/SHOWALTERS INDICATING SOME ELEVATED INSTABILITY...I DECIDED TO ADD CHC THUNDER FOR THE SW MTNS/GA MTNS THROUGH THIS EVENING. A BRIEF HEAVY RAIN AND A COUPLE RUMBLES OF THUNDER IS ALL THAT IS EXPECTED IN ANY EMBEDDED STORMS. OVERNIGHT...A DRY SLOT IS STILL EXPECTED TO JUT NORTH ACROSS OUR AREA...QUICKLY TAPERING OFF PRECIP. THE WEDGE IS NOT EXPECTED TO ERODE UNTIL THE COLD FRONT PASSES THROUGH THE AREA FROM WEST TO EAST. THE NAM IS LITTLE SLOWER THAN THE GFS. BUT THE AVERAGE TIMING IS GENERALLY FROM 9Z ON THE WESTERN EDGE TO 12Z ALONG THE I-77 CORRIDOR. MODEL THICKNESSES AND SOUNDINGS SEEM TO SUPPORT SNOW LEVELS DROPPING AROUND 12Z...WHILE POPS DROP BELOW SLIGHT CHC EAST OF THE MTNS. TEMPERATURES WILL BE NEARLY STEADY OVERNIGHT UNTIL THE FRONTAL PASSAGE...WHERE SHARP DROPS WILL OCCUR IN THE HIGHER ELEVATIONS. && .SHORT TERM /6 AM SUNDAY MORNING THROUGH MONDAY NIGHT/... AS OF 300 PM SATURDAY...ANY DIFFERENCES NOTED IN THE SHORT RANGE MODELS ARE PROBABLY NOT GOING TO SIGNIFICANTLY IMPACT THE FORECAST. BIG CHANGES WILL BE HAPPENING RIGHT AROUND 12Z SUNDAY AS THE UPPER LOW MOVES PAST THROUGH THE OH VALLEY AND THE DRY SLOT BLASTS IN FROM THE SW...WHILE COLD AIR ALOFT COMES IN FROM THE WEST. EXPECT A QUICK END TO THE PRECIP JUST BEFORE SUNRISE EAST OF THE MTNS AND THE GRIDS WILL REFLECT THIS. MEANWHILE...THE MTNS SHOULD RETAIN A LOW CHANCE UNTIL THE AFTERNOON...WHEN IMPROVING NW FLOW UPSLOPE FORCES MORE PRECIP MAINLY ON THE TN BORDER. A LIKELY POP WILL BE RETAINED THERE. THE MOISTURE HOLDS ON INTO THE EVENING...SO THE CHANCE POP FOR THE FIRST PART OF THE SUNDAY NIGHT PERIOD WILL REMAIN UNCHANGED. SNOW LEVELS DROP QUICKLY WHICH SHOULD CHANGE ALL PRECIP OVER TO A MIX AROUND SUNRISE AND ALL SNOW BY NOON. THE UPPER SYSTEM MOVES AWAY QUICKLY WHICH PULLS THE MOISTURE OUT FAST IN THE EVENING...THUS LIMITING THE AMOUNT OF TIME FOR ACCUMULATION. FAIRLY CONFIDENT ABOUT A SNOW ADVISORY WORKING OUT FOR THE NRN MTNS SO HAVE DECIDED TO ISSUE IT NOW EVEN IF PRECIP CHANCE IN THE FORECAST IS NOT YET CATEGORICAL THERE. THE WIND WILL BE A POTENTIALLY BIGGER PROBLEM WITH THE STRONG PRESSURE GRADIENT ALOFT AS THE LOW WRAPS UP OFFSHORE. STRONG COLD ADVECTION WILL KEEP THE BOUNDARY LAYER RELATIVELY DEEP DURING THE DAY WHICH SHOULD ALLOW VERY STRONG WIND GUSTS PERHAPS AS HIGH AS 50 MPH TO MIX DOWN ANYWHERE FROM LATE MORNING THROUGH MID EVENING. RIDGETOPS COULD HAVE GUSTS ABOVE 60 MPH. FOR NOW...WILL ISSUE A WIND ADVISORY ACROSS THE ENTIRE FORECAST AREA AND ADVISE NEXT SHIFTS ABOUT POSSIBLE UPGRADE TO A WARNING OVER THE HIGHER TERRAIN...RATHER THAN COMPLICATE MATTERS WITH A WATCH JUST OVER THE MTNS. ON MONDAY AND MONDAY NIGHT A FLAT UPPER RIDGE WILL BUILD IN FROM THE WEST WHICH SUPPORTS SURFACE HIGH PRESSURE. KEPT THE FORECAST CLOSE TO A GUIDANCE BLEND...WHICH KEEPS IT DRY AND COOL. && .LONG TERM /TUESDAY THROUGH SATURDAY/... AS OF 300 PM SATURDAY...MEDIUM RANGE FORECAST REMAINS IN FLUX AS MODELS SHIFT BETWEEN SLOWER...MORE AMPLIFIED STORM SYSTEMS AND FASTER...LESS AMPLIFIED SYSTEMS. THERE IS GENERAL AGREEMENT ON DRY WX TUE AND WED...THEN A LOW PRESSURE SYSTEM MOVING THROUGH THE AREA LATE THURSDAY AND THU NITE...A DRY PERIOD FOR FRIDAY...THEN ANOTHER LOW PRESSURE SYSTEM MOVING TOWARD THE AREA LATE SATURDAY. THE DISAGREEMENT CONTINUES ON TRACK AND ACTUAL TIMING OF THE LOW PRESSURE SYSTEMS. 12Z GFS ENSEMBLE SHOWS BEST PRECIP CHC LATE THU AND THU NIGHT...THEN AGAIN SAT NITE. HAVE TRIED TO FOLLOW THIS TIMING WITH POP FORECAST. OPERATIONAL MODELS AND GFS ENSEMBLE SHOW THICKNESSES...SOUNDINGS AND H85 TEMPS CONSISTENT WITH A RAIN ONLY FORECAST THRU THE PERIOD. THEREFORE...HAVE GONE ABOVE THE WAY TOO COOL GRIDDED GFS MOS VALUES FOR THE MTNS. OTHERWISE...FOLLOWED THE GUIDANCE CLOSELY. THIS RESULTS IN TEMPS BELOW NORMAL TUE AND TUE NIGHT...THEN RISING TO ABOVE NORMAL THROUGH THE REST OF THE PERIOD. && .AVIATION /00Z SUNDAY THROUGH THURSDAY/... A LARGE AREA OF MODERATE RAIN WILL OVERSPREAD THE TERMINALS OVER THE NEXT 2 HOURS OR SO...WITH VISBY RESTRICTIONS AS LOW AS A MILE BECOMING COMMON IN HEAVIER RAINFALL. ISOLATED THUNDER CANNOT BE RULED OUT...ESPECIALLY ALONG/SOUTH OF THE I-85 CORRIDOR...SO A CB GROUP WILL BE CARRIED THERE THROUGH ABOUT MIDNIGHT. THE RAIN SHOULD MOVE ACROSS THE REGION FAIRLY QUICKLY...LIKELY EXITING THE AREA BY SUNRISE...IF NOT SOONER. HOWEVER...ONCE PRECIP ENDS...CIGS/VISBY MAY ACTUALLY DETERIORATE FURTHER...AS COLD AIR DAMMING AIRMASS BEGINS TO ERODE. WE DO NOT EXPECT THE LOW CLOUDS AND FOG TO SCOUR UNTIL THE COLD FRONT MOVES THROUGH THE AREA JUST AFTER SUNRISE. AT THAT POINT...GUSTY WEST TO NORTHWEST WINDS WILL BECOME A MAJOR ISSUE...AS LOW PRESSURE BOMBS NEAR THE MID-ATLANTIC COAST. EXPECT GUSTS OF 30 KTS OR GREATER AT MOST TERMINALS BY EARLY AFTERNOON. AVIATION OUTLOOK...GUSTY WINDS WILL CONTINUE INTO SUNDAY NIGHT AND POSSIBLY MONDAY. A DRY HIGH PRESSURE RIDGE WILL RESULT IN QUIET WX CONDITIONS ACROSS THE AREA MONDAY NIGHT THROUGH WEDNESDAY NIGHT. ANOTHER STORM SYSTEM WILL BRING RAIN CHANCES BACK TO THE FORECAST ON THURSDAY. && .GSP WATCHES/WARNINGS/ADVISORIES... GA...WIND ADVISORY FROM 6 AM SUNDAY TO MIDNIGHT EST SUNDAY NIGHT FOR GAZ010-017-018-026-028-029. NC...WIND ADVISORY FROM 6 AM SUNDAY TO MIDNIGHT EST SUNDAY NIGHT FOR NCZ033-035>037-048>053-056>059-062>065-068>072-082- 501>510. SNOW ADVISORY FROM 6 AM SUNDAY TO MIDNIGHT EST SUNDAY NIGHT FOR NCZ033-048>050. SC...WIND ADVISORY FROM 6 AM SUNDAY TO MIDNIGHT EST SUNDAY NIGHT FOR SCZ001>014-019. && $$ SYNOPSIS...PAT NEAR TERM...ARK SHORT TERM...PM LONG TERM...RWH AVIATION...JDL sc AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA NATIONAL WEATHER SERVICE SIOUX FALLS SD 1145 AM CDT SUN DEC 16 2007 .DISCUSSION... APOLOGIES FOR THE DELAYED AFD...FORECAST NEGLECTED TO HIT THE SEND BUTTON EARLIER...SO HERE IS A DELAYED UPDATE TO THE AFD. FOG THIS MORNING CONTINUES TO ERODE ALONG THE WRN EDGE OF FOG BANK ACROSS THE I29 CORRIDOR. STILL SOME 1/4 SM VISIBILITIES IN SW MN AND NW IA BUT EXPECT IMPROVEMENT THE NEXT FEW HOURS. WESTERLY WINDS FROM APPROACHING TROUGH SHOULD SCOUR OUT THE REST OF THE FOG THIS AFTERNOON...HOWEVER SOME PLACED SUCH AS WMW...MJG...AND SPW COULD SEE SOME FOG UNTIL NEAR SUNSET. WILL LEAVE HIGH TEMPERATURES AS IS...MAY PLACES NO WARMING AT 5 TO 7 DEGREES PER HOUR WHERE SUN IS SHINING AND EVEN WHERE CLOUDS AND FOG ARE HOLDING...WARM ADVECTION ALOFT WILL GIVE TEMPERATURES A BOOST THIS AFTERNOON. QUESTION FOG TONIGHT WILL BE WHETHER OR NOT MORE FOG WILL FORM. && .AVIATION... VFR THROUGH THE THIS EVENING AT ALL LOCAL TAF SITES...WITH ONLY SOME MID AND HIGH CLOUDS UPPER LEVEL TROUGH SWINGS ACROSS THE AREA. MAY SEE SOME FOG REDEVELOP LATE TONIGHT. && .PREV DISCUSSION... SIMILAR TO YESTERDAY...CLOUD COVER IS THE REAL CHALLENGE TODAY... AT LEAST OVR THE NRN AND ERN PARTS OF OUR FA. AS MENTIONED BLO IN THE AVN SECTION...A LOT OF STRATUS IS WORKING ITS WAY SWD THRU THE ERN DKTS AND CENTRAL MN. IN ADDITION...WE HAVE MID CLOUDS ALREADY OVR SW MN...EXTENDING DOWN TO ABOUT SPENCER IA. AND ANOTHER THIN BAND OF MID LVL CLOUDS IS NOTED IN THE WRN DKTS MOVG EWD. DOUBT THE WRN DKTS MID LVL CLOUD BAND WL HOLD TOGETHER VERY WELL AS IT MOVES EWD. BUT THE STRATUS CERTAINLY WILL. ATTM...FOLLOWED THE RUC/NAM AND GFS H925 RH GUIDANCE IN KEEPING THE STRATUS JUST E OF KHON... EXTENDING IT DOWN THRU E CENTRAL SD AND SW MN. IT SHOULD EVENTUALLY GET INTO SPENCER IA TOO. WL WATCH THE MOVEMENT OF THE STRATUS CLOSELY EARLY THIS MORNING AND SEE IF IT OOZES INTO KFSD AND KHON. HOWEVER KFSD MAY START OUT FAIRLY CLOUDY ANYWAY DUE TO THE MID LVL CLOUD COVER DEVELOPING IN THIS VICINITY. THE STRATUS MAY HAVE A TOUGH TIME LEAVING OUR N AND E...WITH WEAK WAA ABOVE THE SFC CAUSING INCREASINGLY STABLE CONDITIONS...AND A VERY WEAK WLY LOW LEVEL FLOW NOT REALLY ABLE TO SCOUR IT OUT. THEREFORE WAS PRETTY PESSIMISTIC OVR OUR NE QUARTER ON SKY CONDITIONS THRU THE MIDDLE OF THE DAY... WITH A SLOW DECREASE IN CLOUDS DURING THIS AFTN. KEPT TEMPS MANY LOCATIONS EITHER BLO OR WELL BLO MOST GUIDANCE READINGS WITH THE STABLE AIR. TEMPS UNDERNEATH THE STRATUS ARE TRICKY...BECAUSE SOMETIMES THE AIR WILL ACTUALLY WARM UP BETTER WITH A LID OF CLOUD COVER OVER THE SNOW COVER THAN WITH SUNSHINE. SO THEREFORE WITH THE LIGHT WLY FLOW...DID WARM UP OUR NE SECTIN A FAIR AMOUNT. IN OUR SW THOUGH...ALONG AND W OF A KYKN TO KMHE LINE...LITTLE TO NO SNOW COVER EXISTS SO WENT ISOTHERMAL FM H925 IN THOSE AREAS. FOR TONIGHT...KEPT LOWS BLO MOST GUIDANCE READINGS...TRENDING TOWARD THE EVER COOL MAV READINGS OR LOWER. WITH A LIGHT SW OR WLY FETCH OF SFC AIR...SIMILAR TO NOW...WENT AHEAD AND TANKED THE FAVORED LOCATIONS SUCH AS KSUX AND KSPW. HOWEVER MAY NOT HAVE GONE COLD ENOUGH IN SOME OF THESE SPOTS. BUT THE H925 THERMAL IS QUITE WARM TONIGHT...WARMER THAN IT IS NOW...SO DID GO AS COLD TONIGHT AS IT IS RIGHT NOW. AFTER TODAY...WE ARE BASICALLY LOOKING AT A ZONAL FLOW ALOFT THROUGH EARLY IN THE WEEK WITH MODERATING TEMPS JUST ABOVE THE SFC. THERMAL INVERSION STAYS LOCKED IN THIS AREA THROUGH WED. STRONG WAA SCOOTS OVR THIS AREA ON MONDAY PROVIDING ANOTHER VERY STABLE ATMOSPHERE WITH A SLY SFC FLOW. I MAY BE TOO OPTIMISTIC GOING ISOTHERMAL FM H925 OVR THE ENTIRE NRN AND ERN PARTS OF OUR FA. A DRY S/W PASSAGE IS NOTED LATE MON AND MON EVENING OVER THIS AREA. HOWEVER ONE THING TO KEEP AN EYE ON IS LATE MON NIGHT AND TUE MORNING...THE GFS40 H925 RH FIELD SHOWS A LOT OF STRATUS OVR THE NERN PTN OF OUR FA BEHIND THE S/W PASSAGE. THE GFS WAS FAIRLY ACCURATE IN SHOWING THE CURRENT STRATUS ON YESTERDAYS RUN. SO IT IS DIFFICULT TO IGNORE THIS. ATTM...HEDGED AND PUT IN SOME CLOUD COVER FOR THIS TIMEFRAME IN OUR NE. FOR LOWS MONDAY NIGHT...WITH THE LIGHT SFC FLOW...AGAIN TRIED TO FAVOR WARMER READINGS OVR THE HIGHER TERRAIN SUCH AS SW MN AND OUR SWRN FA...WITH COLDER READINGS IN THE VALLEYS. TUE MAY BE SLIGHTLY WARMER THAN MONDAY WITH A LIGHT WLY SFC WIND. NEXT SLIGHTLY STRONGER WAVE TO WATCH IS LATE WED AND WED EVENING. THIS WAVE HAS BEEN WELL ADVERTISED BY THE VARIOUS MODELS. FRONTOGENESIS AND OVERALL ASCENT IS WEAK WITH THIS WAVE. BUT THE GFS DOES SATURATE UP THE PROFILE OVR OUR ERN HALF WED AFTN...EXTENDING INTO WED EVE ACROSS OUR E. BOOSTED SOME DRY POPS ATTM BUT DID NOT INLCUDE -SN AS THE ECMWF AND GEM WERE NOT BACKING UP THE GFS WITH QPF IN OUR EAST. AND AS MENTIONED...EVEN THE GFS DYNAMICS ARE QUITE WEAK. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...NONE. MN...NONE. IA...NONE. NE...NONE. && $$ MJF/BT sd AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA NATIONAL WEATHER SERVICE SIOUX FALLS SD 320 AM CDT SUN DEC 16 2007 .DISCUSSION... SIMILAR TO YESTERDAY...CLOUD COVER IS THE REAL CHALLENGE TODAY... AT LEAST OVR THE NRN AND ERN PARTS OF OUR FA. AS MENTIONED BLO IN THE AVN SECTION...A LOT OF STRATUS IS WORKING ITS WAY SWD THRU THE ERN DKTS AND CENTRAL MN. IN ADDITION...WE HAVE MID CLOUDS ALREADY OVR SW MN...EXTENDING DOWN TO ABOUT SPENCER IA. AND ANOTHER THIN BAND OF MID LVL CLOUDS IS NOTED IN THE WRN DKTS MOVG EWD. DOUBT THE WRN DKTS MID LVL CLOUD BAND WL HOLD TOGETHER VERY WELL AS IT MOVES EWD. BUT THE STRATUS CERTAINLY WILL. ATTM...FOLLOWED THE RUC/NAM AND GFS H925 RH GUIDANCE IN KEEPING THE STRATUS JUST E OF KHON... EXTENDING IT DOWN THRU E CENTRAL SD AND SW MN. IT SHOULD EVENTUALLY GET INTO SPENCER IA TOO. WL WATCH THE MOVEMENT OF THE STRATUS CLOSELY EARLY THIS MORNING AND SEE IF IT OOZES INTO KFSD AND KHON. HOWEVER KFSD MAY START OUT FAIRLY CLOUDY ANYWAY DUE TO THE MID LVL CLOUD COVER DEVELOPING IN THIS VICINITY. THE STRATUS MAY HAVE A TOUGH TIME LEAVING OUR N AND E...WITH WEAK WAA ABOVE THE SFC CAUSING INCREASINGLY STABLE CONDITIONS...AND A VERY WEAK WLY LOW LEVEL FLOW NOT REALLY ABLE TO SCOUR IT OUT. THEREFORE WAS PRETTY PESSIMISTIC OVR OUR NE QUARTER ON SKY CONDITIONS THRU THE MIDDLE OF THE DAY... WITH A SLOW DECREASE IN CLOUDS DURING THIS AFTN. KEPT TEMPS MANY LOCATIONS EITHER BLO OR WELL BLO MOST GUIDANCE READINGS WITH THE STABLE AIR. TEMPS UNDERNEATH THE STRATUS ARE TRICKY...BECAUSE SOMETIMES THE AIR WILL ACTUALLY WARM UP BETTER WITH A LID OF CLOUD COVER OVER THE SNOW COVER THAN WITH SUNSHINE. SO THEREFORE WITH THE LIGHT WLY FLOW...DID WARM UP OUR NE SECTIN A FAIR AMOUNT. IN OUR SW THOUGH...ALONG AND W OF A KYKN TO KMHE LINE...LITTLE TO NO SNOW COVER EXISTS SO WENT ISOTHERMAL FM H925 IN THOSE AREAS. FOR TONIGHT...KEPT LOWS BLO MOST GUIDANCE READINGS...TRENDING TOWARD THE EVER COOL MAV READINGS OR LOWER. WITH A LIGHT SW OR WLY FETCH OF SFC AIR...SIMILAR TO NOW...WENT AHEAD AND TANKED THE FAVORED LOCATIONS SUCH AS KSUX AND KSPW. HOWEVER MAY NOT HAVE GONE COLD ENOUGH IN SOME OF THESE SPOTS. BUT THE H925 THERMAL IS QUITE WARM TONIGHT...WARMER THAN IT IS NOW...SO DID GO AS COLD TONIGHT AS IT IS RIGHT NOW. AFTER TODAY...WE ARE BASICALLY LOOKING AT A ZONAL FLOW ALOFT THROUGH EARLY IN THE WEEK WITH MODERATING TEMPS JUST ABOVE THE SFC. THERMAL INVERSION STAYS LOCKED IN THIS AREA THROUGH WED. STRONG WAA SCOOTS OVR THIS AREA ON MONDAY PROVIDING ANOTHER VERY STABLE ATMOSPHERE WITH A SLY SFC FLOW. I MAY BE TOO OPTIMISTIC GOING ISOTHERMAL FM H925 OVR THE ENTIRE NRN AND ERN PARTS OF OUR FA. A DRY S/W PASSAGE IS NOTED LATE MON AND MON EVENING OVER THIS AREA. HOWEVER ONE THING TO KEEP AN EYE ON IS LATE MON NIGHT AND TUE MORNING...THE GFS40 H925 RH FIELD SHOWS A LOT OF STRATUS OVR THE NERN PTN OF OUR FA BEHIND THE S/W PASSAGE. THE GFS WAS FAIRLY ACCURATE IN SHOWING THE CURRENT STRATUS ON YESTERDAYS RUN. SO IT IS DIFFICULT TO IGNORE THIS. ATTM...HEDGED AND PUT IN SOME CLOUD COVER FOR THIS TIMEFRAME IN OUR NE. FOR LOWS MONDAY NIGHT...WITH THE LIGHT SFC FLOW...AGAIN TRIED TO FAVOR WARMER READINGS OVR THE HIGHER TERRAIN SUCH AS SW MN AND OUR SWRN FA...WITH COLDER READINGS IN THE VALLEYS. TUE MAY BE SLIGHTLY WARMER THAN MONDAY WITH A LIGHT WLY SFC WIND. NEXT SLIGHTLY STRONGER WAVE TO WATCH IS LATE WED AND WED EVENING. THIS WAVE HAS BEEN WELL ADVERTISED BY THE VARIOUS MODELS. FRONTOGENESIS AND OVERALL ASCENT IS WEAK WITH THIS WAVE. BUT THE GFS DOES SATURATE UP THE PROFILE OVR OUR ERN HALF WED AFTN...EXTENDING INTO WED EVE ACROSS OUR E. BOOSTED SOME DRY POPS ATTM BUT DID NOT INLCUDE -SN AS THE ECMWF AND GEM WERE NOT BACKING UP THE GFS WITH QPF IN OUR EAST. AND AS MENTIONED...EVEN THE GFS DYNAMICS ARE QUITE WEAK. && .AVIATION... TRICKY AVIATION FORECAST THIS MORNING WITH LOW CLOUDS AND LOW VISIBILITIES FILTERING DOWN THE JAMES RIVER VALLEY. OVER THE PAST FEW HOURS...ABERDEEN FELL INTO THE TANK GOING FROM UNRESTRICTED VISIBILITY DOWN TO A QUARTER OF A MILE. WHETHER THE FOG MAKES IT DOWN TO KHON REMAINS TO BE SEEN...BUT IF IT DOES...IT WILL LIKELY BE STUBBORN AND STICK AROUND FOR A WHILE WITH STRONG INVERSION IN PLACE. EXPECT PATCHY TO AREAS OF FOG ACROSS THE REMAINDER OF THE AREA THROUGH 15-16Z THEN VFR CONDITIONS PREVAILING. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...NONE. MN...NONE. IA...NONE. NE...NONE. && $$ MJF/BT sd AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE ABERDEEN SD 1149 AM CST SAT DEC 15 2007 .UPDATE... AN AREA OF DENSE FOG HAS FORMED OVER THE NORTHERN JAMES RIVER VALLEY THIS MORNING WITH PLENTIFUL LOW LEVEL MOISTURE IN PLACE. KABR HAS BEEN REPORTING 1/4 TO 1/2 MILE IN FZFG MOST OF THE MORNING. ISSUED A NOWCAST AND UPDATED FORECAST TO ADD IN MENTION OF AREAS OF DENSE FOG IN PRIMARILY BROWN COUNTY...AS CALLS TO SOUTHERN AREAS OF THE JAMES VALLEY DO NOT REVEAL ANY FOG. WATERTOWN HAS ALSO DROPPED TO 5SM IN BR...SO MAY HAVE TO MONITOR REGIONS TO THE EAST FOR SOME FOG FORMATION IN THESE AREAS AS WELL. THE QUESTION BECOMES HOW LONG THE FOG WILL HANG AROUND...FORECAST RUC/NAM SOUNDINGS...PARTICULARLY THE RUC...REFLECT A GOOD DEAL OF LOW LEVEL MOISTURE AND CLOUDS IN PLACE THROUGHOUT THE ENTIRE DAY AT KABR AND SOMEWHAT AT KATY AS WELL...AND BOTH INDICATE ADDITIONAL FOG FORMATION LATER THIS EVENING INTO TONIGHT. THERE IS A WEAK BOUNDARY MOVING THROUGH THE CWA THIS MORNING...WITH GENERALLY LIGHT SOUTHERLY WINDS AHEAD OF IT...AND WESTERLY WINDS BEHIND IT...AND A DECK OF MID LEVEL CLOUDS ASSOCIATED WITH IT...AND THE NAM/RUC FORECAST THIS BOUNDARY TO REACH THE JAMES VALLEY IN THE NEXT HOUR OR TWO. HOWEVER...BOTH ALSO INDICATE THAT THE SHIFT TO WESTERLY WINDS MAY REMAIN ABOVE THE SURFACE AND THUS ABOVE THE FOG LAYER...WHICH WILL ALLOW THE FOG TO REMAIN IN PLACE INSTEAD OF DISSIPATE AND LIFT. FOR NOW...ONLY CONTINUED THE FOG FOR A COUPLE HOURS INTO THE EARLY AFTERNOON...BUT WILL BE MONITORING AND MAY HAVE TO UPDATE AGAIN IF INDICATIONS POINT TO A LONGER DURATION OF FOG AND WESTERLY WINDS REMAIN ABOVE THE SURFACE. MOST OTHER ELEMENTS REMAIN AS INHERITED. A NEW AVIATION DISCUSSION IS FOUND BELOW. && .PREV DISCUSSION... .SHORT TERM...TODAY THROUGH MONDAY FORECAST CHALLENGES INCLUDE WARMING TEMPERATURES OVER A SNOW FIELD...AND ANY FOG POTENTIAL FROM SNOW MELT ACCOMPANYING A WARMER AIRMASS. WELL...THE ARCTIC COLD FRONTAL BOUNDARY THAT GOT HUNG UP NORTH TO SOUTH ACROSS THE WESTERN DAKOTAS THE OTHER DAY IS FINALLY STARTING TO MAKE SOME PROGRESS EASTWARD...AS A WARM FRONT ACCOMPANYING A WEAK MID-LEVEL S/W TROF WORKING INTO THE REGION EARLY THIS MORNING FROM THE NORTHWEST. THERE IS A LARGE AREA OF MAINLY MVFR CLOUDS STILL HANGING OUT ACROSS THE EASTERN TWO-THIRDS OF ZONES THIS MORNING...ALTHOUGH CLOUD MOTION FROM FOG PRODUCT SATELLITE IMAGERY SUGGESTS THERE IS SOME NORTH AND EAST MOTION TO THESE CLOUDS WITH A LOW LEVEL SOUTHWESTERLY STEERING WIND OUT AHEAD OF THE AFOREMENTIONED BOUNDARY/SFC-TROF. THERE ARE ALSO ADDITIONAL CLOUDS WORKING INTO NORTH CENTRAL SOUTH DAKOTA FROM THE NORTHWEST BEHIND THE TROF AXIS. ASSUMING THE LOW LEVEL STEERING WINDS DUE IN FACT SWING AROUND TO THE WEST-NORTHWEST /SOMETIMES MODELS OVERPLAY THIS AND CLOUDS END UP HANGING ON LONGER THAN ANTICIPATED/ BY THIS AFTERNOON...LOW CLOUDS SHOULD BE A THING OF THE PAST BY MID EVENING...RENDERING THE TONIGHT PERIOD MOSTLY CLEAR. UNTIL THEN...THERE MAY BE A FEW FLAKES FALLING OUT OF THE LOW CLOUDS TODAY. NOT SOMETHING THAT SEEMED VALIDATED BY FLURRIES MENTION FOR NOW IN THE GRIDS. OTHERWISE...A COUPLE MORE WEAK/DRY MID-LEVEL WAVES MOVING THROUGH THE REGION SUNDAY AND AGAIN MONDAY WILL SWEEP SURFACE TROF REFLECTIONS ACROSS THE DAKOTAS FROM WEST TO EAST...WITH A LITTLE BIT WARMER AIR BEING INTRODUCED INTO THE FORECAST AREA WITH EACH PASSING WAVE. AT SOME POINT DOWN THE ROAD WILL BE DEALING WITH SOME CONSIDERABLE FOG PROBLEMS IF PROGRESSIVELY WARMER AIR DOES SUCCEED IN WORKING OVER THE FAIRLY WIDESPREAD SNOW FIELD IN PLACE ACROSS THE EASTERN DAKOTAS. BUT...FOR NOW...STILL JUST MONITORING FOR POTENTIAL. .LONG TERM...MONDAY NIGHT THROUGH FRIDAY GOOD AGREEMENT WITH ALL THE MODELS AND GFS ENSEMBLES THAT FAST PACIFIC FLOW WILL CONTINUE OVER THE REGION THROUGH MUCH OF THE LONG TERM WITH SEVERAL SHORT WAVES AFFECTING THE REGION. THE FIRST SHORT WAVE ASSOCIATED SURFACE LOW PRESSURE AREA WILL MOVE ACROSS SOUTHERN CANADA ON MONDAY NIGHT AND TUESDAY WITH A PACIFIC FRONT MOVING ACROSS OUR CWA. MONDAY NIGHT COULD END UP BEING A WARM NIGHT AS WINDS BECOME WEST AND INCREASE. LOWS SHOULD BE EARLY BEFORE RISING OR LEVELING OFF. TUESDAY WILL LIKELY BE A MILD DAY WITH GOOD MIXING OF PACIFIC AIR WITH WEST WINDS. FOR THE SNOW COVERED AREAS...IT WILL BE TOUGH FOR THE TEMPERATURES TO RISE TO 32 OR ABOVE AND THIS IS THE TYPICAL WINTER TIME SETUP WHERE A WARM UP TAKES PLACE OVER SNOW COVER. OTHERWISE...SURFACE HIGH PRESSURE RIDGING WILL SLIDE OVER THE CWA TUESDAY NIGHT WITH WINDS GOING LIGHT AND TURNING SOUTH BY MORNING. THE NEXT PACIFIC TROUGH AND SURFACE TROUGH/LOW PRESSURE AREA WILL MOVE FARTHER SOUTH THAN THE FIRST ONE ACROSS THE CENTRAL PLAINS WEDNESDAY AND WEDNESDAY NIGHT. THIS ONE WILL BE A LITTLE STRONGER AS THE MODELS SHOW IT INTENSIFYING AS IT MOVES ACROSS THE REGION. THERE IS ALSO SOME INDICATION THAT SOME LIGHT PRECIPITATION MAY OCCUR FAR EAST IN THE CWA. WILL LEAVE IT DRY FOR NOW. OTHERWISE...WEDNESDAY WILL BE COOLER WITH SOUTH TO SOUTHEAST WINDS COMING ACROSS SNOW COVER TO THE SOUTH ALONG WITH MID AND HIGH CLOUDS FROM THE PACIFIC TROUGH. THE MODELS AND ENSEMBLES THEN SHOW A MORE SIGNIFICANT UPPER TROUGH TAKING SHAPE IN THE SOUTHWEST US THURSDAY THROUGH FRIDAY ALONG WITH A DECENT SURFACE LOW PRESSURE AREA DEVELOPING AND HEADING OUT INTO THE SOUTHERN PLAINS BY FRIDAY NIGHT. THE LATEST EC AND GFS AGREE REALLY WELL ON THIS ALONG WITH SPREADING SOME PRECIPITATION NORTH INTO OUR AREA FRIDAY AND FRIDAY NIGHT. LEFT IT DRY FOR NOW AND WILL SEE WHAT LATER RUNS BRING. && .AVIATION... LOW CLOUDS CONTINUE ACROSS THE EASTERN PORTIONS OF THE AREA...NOTABLY THE KABR/KATY TAF SITES...WITH DENSE FZFG FORMING AT KABR AND CONTINUING LATE THIS MORNING. KATY IS ALSO BEGINNING TO REPORT LIGHT FOG FORMATION. WILL BE MONITORING THE FOG DURATION POTENTIAL...BUT INDICATIONS RIGHT NOW ARE THAT A WEAK BOUNDARY MOVING THROUGH THE AREA WILL SHIFT WINDS MORE WESTERLY JUST ABOVE THE SURFACE IN THE JAMES VALLEY BY 18 TO 19Z...AND AT KATY BY 21 TO 22Z...WHICH WOULD HELP MIX OUT THE FOG IF SURFACE WINDS ARE ABLE TO SHIFT TO THE WEST. HOWEVER...THE WIND SHIFT MAY NOT MAKE IT ALL THE WAY TO THE IMMEDIATE SURFACE...AND THUS THE FOG MAY HANG AROUND LONGER THAN CURRENTLY ANTICIPATED. FOR NOW...DID LIFT FOG IN THE TAFS BY THIS AFTERNOON AT KABR...BY 20Z. OTHERWISE...MID LEVEL CLOUDS AT OR ABOVE 6000 FEET ALSO CONTINUE ACROSS SOUTH DAKOTA THIS MORNING...HAVING ALREADY CLEARED MOBRIDGE AND PIERRE. LOW LEVEL MOISTURE HANGS AROUND AND ANTICIPATE ADDITIONAL FOG FORMATION AT KABR/KATY THIS EVENING INTO TONIGHT AS WINDS BECOME FAIRLY LIGHT AND LOW LEVEL MOISTURE OVER A FIELD OF SNOW REMAINS PLENTIFUL. && .ABR WATCHES/WARNINGS/ADVISORIES... SD...NONE. MN...NONE. && $$ UPDATE...ECKSTEIN SHORT TERM...DORN LONG TERM...MOHR AVIATION...ECKSTEIN WEATHER.GOV/ABERDEEN sd AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NASHVILLE TN 858 PM CST SAT DEC 15 2007 .UPDATE... UPR TROUGH REMAINS UPSTREAM AS ECHOES MOVE NORTHEAST. COLD FRONT HAS SLOWED DOWN A LITTLE THIS EVENING WEST OF THE MID STATE. STEERING WINDS WILL TURN WEST AFT MIDNIGHT...AS THE COLD FRONT MARCHES IN. MIX/CHANGE TO FROZEN PCPN AFT MIDNIGHT...LATE IN EAST MID TN. POST FRONTAL SNOWS IN SOUTHEAST MO ASSOC WITH UPR DEFORMATION AND NEGATIVE TILT. ALTHOUGH UPR TROUGH MOVES OVR MID TN TONIGHT...DEEPER MOISTURE REMAINS NORTH 06-12Z. SO WILL DOWNPLAY SNOW AMOUNTS N MID TN (LITTLE TO NO SNOW ACCUM). BUT WL KEEP SNOW ADVISORY RUNNING THROUGH 18Z IN THE PLATEAU SUN...WITH STRONG NORTHWEST FLOW. && .PREV DISCUSSION... /ISSUED 118 PM CST SAT DEC 15 2007/ DISCUSSION... UPPER TROUGH BEGINNING TO PULL EAST PER LATEST SATELLITE LOOP. RAIN AREA HAS BEEN SLOW COMING EAST WITH HEAVY RAIN OVER THE WESTERN PARTS OF MID STATE THIS MORNING. CLARKSVILLE MEASURED 1.17 INCHES SINCE 6 AM. DOPPLER SHOWS 1 TO 2 INCHES ACROSS PARTS OF STEWART...MONTGOMERY...HOUSTON...BENTON AND HUMPHREYS. STILL MORE RAIN TO COME THIS AFTERNOON AND EVENING. THE RAIN AREA HAS BEEN SLOW TO TRANSLATE EAST DURING THE DAY WITH DRIER AIR SHOWING UP ACROSS NORTHERN ALABAMA INTO SOUTHERN MIDDLE TN AT MID-DAY. SURFACE FEATURES STILL TRYING TO GET ORGANIZED AS STORM IS VERY COMPLEX. AFTER LOOKING AT THE LATEST ISALLOBARIC PATTERN BELIEVE LATEST RUC MAY HAVE THE BETTER HANDLE ON SURFACE LOW TRACK. LATEST RUC HAS LOW NEAR LAND BETWEEN THE LAKES ABOUT 00Z. 12Z GFS IS A LITTLE MORE EAST OF THIS TRACK. SHOULD BE SHORTLY AFTER MIDNIGHT BEFORE THE CHANGE OVER TO SNOW TAKES PLACE FIRST IN THE NORTHWEST AND PUSH EAST OVERNIGHT. THERE WILL BE A MIX AT FIRST THEN A CHANGE TO ALL SNOW. WILL PLAY IT THIS WAY: SNOW ADVISORY FOR PLATEAU COUNTIES WITH GENERALLY 1 TO 2 INCHES POSSIBLE...CANT RULE OUT SOME ISOLATED 3 INCH AMOUNTS. UP TO AN INCH POSSIBLE ACROSS THE NORTH HALF OF MID STATE AND A DUSTING OVER THE SOUTH. THESE ACCUMULATIONS ARE BASED ON A 1 TO 10 RATIO WHICH MAY NOT BE ALL THAT REPRESENTATIVE WITH THIS SYSTEM BUT BEST I CAN DO. LIGHT SNOW SHOULD TAPER TO FLURRIES IN THE MORNING IN ALL AREAS EXCEPT PLATEAU WHERE IT WILL BE LATER. COLD SUNDAY WITH ONLY MINOR TEMP RECOVERY AND THEN IN THE LOW TO MID 20S SUNDAY NIGHT. COLD WIND CHILL TEMPS BOTH SUNDAY AND SUNDAY NIGHT. WE`VE NOT HAD MEASURABLE SNOW IN THE MONTH OF DECEMBER AT NASHVILLE SINCE 2.6 INCHES FELL BACK IN DECEMBER OF 2000. SO WE ARE OVER DUE. THE MOST SNOW EVER TO FALL IN THE MONTH OF DECEMBER IS 13.2 INCHES BACK IN 1963. 7.4 INCHES OF SNOW FELL ON DECEMBER 22ND AND 23RD 1963. THE 1960`S WAS THE SNOWIEST DECADE ON RECORD IN NASHVILLE. OHX WATCHES/WARNINGS/ADVISORIES... SNOW ADVISORY FROM 3 AM TO 12 PM CST SUNDAY FOR TNZ010-011- 031>034-065-066-080. $$ && .OHX WATCHES/WARNINGS/ADVISORIES... SNOW ADVISORY FROM 3 AM TO 12 PM CST SUNDAY FOR TNZ010-011- 031>034-065-066-080. && $$ 04 tn AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NASHVILLE TN 118 PM CST SAT DEC 15 2007 .DISCUSSION... UPPER TROUGH BEGINNING TO PULL EAST PER LATEST SATELLITE LOOP. RAIN AREA HAS BEEN SLOW COMING EAST WITH HEAVY RAIN OVER THE WESTERN PARTS OF MID STATE THIS MORNING. CLARKSVILLE MEASURED 1.17 INCHES SINCE 6 AM. DOPPLER SHOWS 1 TO 2 INCHES ACROSS PARTS OF STEWART...MONTGOMERY...HOUSTON...BENTON AND HUMPHREYS. STILL MORE RAIN TO COME THIS AFTERNOON AND EVENING. THE RAIN AREA HAS BEEN SLOW TO TRANSLATE EAST DURING THE DAY WITH DRIER AIR SHOWING UP ACROSS NORTHERN ALABAMA INTO SOUTHERN MIDDLE TN AT MID-DAY. SURFACE FEATURES STILL TRYING TO GET ORGANIZED AS STORM IS VERY COMPLEX. AFTER LOOKING AT THE LATEST ISALLOBARIC PATTERN BELIEVE LATEST RUC MAY HAVE THE BETTER HANDLE ON SURFACE LOW TRACK. LATEST RUC HAS LOW NEAR LAND BETWEEN THE LAKES ABOUT 00Z. 12Z GFS IS A LITTLE MORE EAST OF THIS TRACK. SHOULD BE SHORTLY AFTER MIDNIGHT BEFORE THE CHANGE OVER TO SNOW TAKES PLACE FIRST IN THE NORTHWEST AND PUSH EAST OVERNIGHT. THERE WILL BE A MIX AT FIRST THEN A CHANGE TO ALL SNOW. WILL PLAY IT THIS WAY: SNOW ADVISORY FOR PLATEAU COUNTIES WITH GENERALLY 1 TO 2 INCHES POSSIBLE...CANT RULE OUT SOME ISOLATED 3 INCH AMOUNTS. UP TO AN INCH POSSIBLE ACROSS THE NORTH HALF OF MID STATE AND A DUSTING OVER THE SOUTH. THESE ACCUMULATIONS ARE BASED ON A 1 TO 10 RATIO WHICH MAY NOT BE ALL THAT REPRESENTATIVE WITH THIS SYSTEM BUT BEST I CAN DO. LIGHT SNOW SHOULD TAPER TO FLURRIES IN THE MORNING IN ALL AREAS EXCEPT PLATEAU WHERE IT WILL BE LATER. COLD SUNDAY WITH ONLY MINOR TEMP RECOVERY AND THEN IN THE LOW TO MID 20S SUNDAY NIGHT. COLD WIND CHILL TEMPS BOTH SUNDAY AND SUNDAY NIGHT. WE`VE NOT HAD MEASURABLE SNOW IN THE MONTH OF DECEMBER AT NASHVILLE SINCE 2.6 INCHES FELL BACK IN DECEMBER OF 2000. SO WE ARE OVER DUE. THE MOST SNOW EVER TO FALL IN THE MONTH OF DECEMBER IS 13.2 INCHES BACK IN 1963. 7.4 INCHES OF SNOW FELL ON DECEMBER 22ND AND 23RD 1963. THE 1960`S WAS THE SNOWIEST DECADE ON RECORD IN NASHVILLE. && .OHX WATCHES/WARNINGS/ADVISORIES... SNOW ADVISORY FROM 3 AM TO 12 PM CST SUNDAY FOR TNZ010-011- 031>034-065-066-080. && $$ BOYD tn AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE CORPUS CHRISTI TX 818 PM CST SUN DEC 16 2007 .UPDATE...BASED ON EVENING SOUNDING AND CURRENT DEWPOINT DATA/ANALYSIS HAVE DECIDED TO GO WITH A FREEZE WARNING FOR WESTERN PORTIONS OF NUECES AND KLEBERG COUNTIES...NEAR AND WEST OF US HIGHWAY 77. CURRENT TEMPS AT KCRP NOW AT 40F AND CONTINUING TO FALL. DEWPOINTS AT HEBBRONVILLE AT 12F...KALI AT 23F AND KRBO AT 27F. EVENING SOUNDING SHOWING EVEN DRIER BOUNDARY LAYER THAN YESTERDAY...AND LATEST RUC FORECAST WINDS OVER NUECES AND KLEBERG COUNTIES ACTUALLY GO MORE NNW AFTER 06Z. THUS...HAVE DECIDED TO GO WITH THE FREEZE WARNING FOR THE AFOREMENTIONED COUNTIES AT THIS TIME. RESIDENTS OF THE CITY OF CORPUS CHRISTI WILL LIKELY HAVE TEMPERATURES SLIGHTLY ABOVE FREEZING EXCEPT IN ISOLATED AREAS WHERE A LIGHT FREEZE CAN OCCUR. MODIFIED GRIDS SOME BASED ON OBSERVATIONS. PRODUCTS OUT...WITH NO OTHER MAJOR CHANGES. && .PREV DISCUSSION... /ISSUED 535 PM CST SUN DEC 16 2007/ AVIATION UPDATE...VFR CONDS THRU THE TAF PERIOD. CLEAR SKIES TONIGHT. HIGH CIRRUS STREAMING IN W TO E MON MORNING. BKN 3500-5000 FT STRATACU DECK DVLPG S TO N NEAR AND AFTR 18Z. LGT NE TO E WNDS OVERNIGHT BCMG LGT TO MDT SE WNDS BY 18Z. PREV DISCUSSION... /ISSUED 255 PM CST SUN DEC 16 2007/ SHORT TERM (TONIGHT THROUGH MONDAY NIGHT)...VERY LOW DEWPOINTS...A COOL AIRMASS AND CLEAR SKIES WL ONCE AGAIN PRODUCE FREEZING TEMPS ACROSS PORTIONS OF THE CWA TNT. GUIDANCE MINS CONTINUE TO BE TOO WARM WITH THIS AIRMASS. AS A RESULT...WL UNDERCUT TNTS MINS BY SVRL DEGS IN MOST PLACES. WL RE-ISSUE THE FREEZE WARNING FOR THE ENTIRE AREA EXCEPT FOR ARANSAS...KLEBERG AND NUECES COUNTIES. RETURN FLOW WL BEGIN MONDAY MORNING AS STRATUS BEGINS TO ADVANCE INLAND FROM THE GULF. EXPECT MOSTLY CLOUDY TO OVERCAST CONDITIONS BY MON AFTN/EVE AS THE ISENTROPIC UPGLIDE IN THE 290-295K LYR STRENGTHENS. LIGHT PCPN WL BEGIN TO DEVELOP AS EARLY AS MON EVE OVER THE WATERS AND THEN AFFECT THE ERN COUNTIES OVERNIGHT MONDAY. WL GO WITH SLIGHT CHC TO LOW CHC POPS FOR MON NIGHT. LEANED TWDS THE GFS TEMPS FOR MON AND MON NIGHT. LONG TERM (TUESDAY THROUGH SUNDAY)...A GRADUAL WARMING TREND ALONG WITH INCREASING MOISTURE WILL TAKE PLACE TUESDAY THROUGH WEDNESDAY. A FEW WEAK EMBEDDED SHORTWAVES IN FAIRLY ZONAL FLOW ALOFT WILL COMBINE WITH THE LIMITED MOISTURE AND A MODERATE LOW LEVEL JET TO PRODUCE A FEW SHRA`S ACROSS THE COASTAL WATERS AND E TO NE CWA FOR TUE-WED TIMEFRAME. MAIN ISSUE FOR TUE-WED OVRNITE HRS WILL BE POTENTIAL FOR FOG GIVEN THE HIGH RH VALUES AND WEAK SFC FLOW. ALTHOUGH IT SHOULD BE A MIX OF FOG WITH STRATUS AS THE LLJ INCREASES EACH NIGHT. MODELS ARE IN AGREEMENT WITH BRINGING A WEAK PAC FRONT THROUGH THE CWA ON THUR MORNING BUT WITH NO SIGNIFICANT PRECIP OR CAA...JUST MAINLY A DRIER AIRMASS/LOWER DEWPOINTS. THUS MAX TEMPS WILL BE SIMILAR TO WED MAX TEMPS. THE SFC HIGH QUICKLY SHIFTS E THRU THE DAY WITH ONSHORE FLOW QUICKLY RETURNING BY THUR EVENING. THIS WILL USHER THE LIMITED MOISTURE/HIGHER DEWPOINTS BACK INTO THE CWA...LEADING TO ANOTHER MODERATE DAY ON FRI. MODELS HAVE BEEN SHOWING A STRONGER COLD FRONT ON SAT...BUT NOT QUITE AS STRONG AS THIS PAST CF THAT BLASTED THROUGH YESTERDAY (SATURDAY). A STRONG NLY AND DRIER/COOLER AIRMASS IS EXPECTED TO BLD ACROSS S TX THRU SAT AND CONT INTO SUN. AVIATION...CLEAR SKIES WL PREVAIL UNTIL MONDAY MORNING. STRATUS WITH CEILINGS BETWEEN 4K AND 6K FT WL MOVE INLAND FROM THE GULF BETWEEN 13Z AND 18Z MONDAY. VFR CEILINGS WL THEN PREVAIL AFTER 18Z MONDAY. MVFR CEILINGS WL THEN DEVELOP AFTER MIDNIGHT MONDAY ACROSS ALI...CRP AND VCT. MARINE...WL LET THE CURRENT SCA EXPIRE FOR THE OFFSHORE WATERS SINCE THE SEAS CONTINUE TO RAPIDLY SUBSIDE. OTHERWISE...A WK TO MODERATE NE FLOW WL DEVELOP TNT AND BECOME ONSHORE ON MON/MON NIGHT AS THE SFC RDG AXIS ACROSS SOUTH TX PUSHES RAPIDLY EWD. && .PRELIMINARY POINT TEMPS/POPS... CORPUS CHRISTI 32 63 55 75 63 / 0 10 30 20 10 VICTORIA 28 63 51 73 58 / 0 10 30 20 20 LAREDO 34 66 53 78 60 / 0 0 10 10 10 ALICE 31 63 54 77 60 / 0 10 20 10 10 ROCKPORT 38 61 56 71 63 / 0 10 30 20 20 COTULLA 29 63 47 77 56 / 0 0 10 10 10 KINGSVILLE 32 63 55 77 62 / 0 10 30 10 10 NAVY CORPUS 40 63 57 73 65 / 0 10 30 20 10 && .CRP WATCHES/WARNINGS/ADVISORIES... TX...FREEZE WARNING FROM 2 AM TO 8 AM CST MONDAY FOR THE FOLLOWING ZONES: BEE...CALHOUN...DUVAL...GOLIAD...JIM WELLS... KLEBERG...LA SALLE...LIVE OAK...MCMULLEN...NUECES... REFUGIO...SAN PATRICIO...VICTORIA...WEBB. GM...NONE. && $$ JR/76...SHORT TERM GW/86...LONG TERM tx AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE CORPUS CHRISTI TX 1156 PM CST SAT DEC 15 2007 .UPDATE...UPDATED ZFPCRP FOR WINDS AND DID ADJUST TEMPS UP A BIT MAINLY OVER THE COASTAL COUNTIES WHERE WINDS HAVE KEPT TEMPS UP. WINDS ARE SUPPOSED TO DIMINISH (IT HAS BEEN TAKING LONGER THAN EXPECTED) BUT MSAS IS SHOWING TIGHTEST GRADIENT MOVING INTO THE COASTAL AREAS AT THIS TIME WITH GRADIENT MUCH LESS FARTHER INLAND. MAINTAINED FREEZE WARNING BUT LOOKS LIKE IT MAY BE LONGER FOR TEMPS TO REACH THAT LEVEL WITH WINDS UP MOST OF THE NIGHT. STILL POSSIBLE THAT FREEZING TEMPERATURES FOR 2 TO 4 HOURS WILL OCCUR OVER THE NORTHERN TIER OF COUNTIES. FINALLY...ALTHOUGH WINDS NEAR THE COAST IN A FEW LOCATIONS (KNGP) ARE IN THE WIND ADVISORY CRITERION...MOST LOCATIONS DO NOT MEET CRITERION. THUS...PUT OUT SHORT-TERM FORECAST (WINDS ARE SUPPOSED TO DIMINISH) SO NO ADVISORY. QUIETER AND MUCH LESS WIND ON SUNDAY. PRODUCTS ARE OUT. && .AVIATION...MAINTAINED WIND SHEAR ENDING AOB 12Z AS 925MB GRADIENT. OTHERWISE...VFR CONDITIONS WITH GRADUAL VEERING OF WINDS DURG DAY. && .PREV DISCUSSION... /ISSUED 948 PM CST SAT DEC 15 2007/ DISCUSSION...WINDS STILL CRANKING FROM TIME TO TIME NEAR THE COAST SO FOR NOW WILL NOT UPDATE ZFP UNTIL WINDS SETTLE DOWN (SHOULD BE BY MIDNIGHT). OTHERWISE...PREVIOUS FORECAST AND/OR UPDATED GRIDS SEEM TO BE HOLDING THEIR OWN ATTM SO NO UPDATES TO THE GRIDDED TEXT PRODUCTS NEEDED AT THIS TIME EITHER. HAVE MAINTAINED THE HIGH END SCA FOR THE OFFSHORE WATERS AT THIS TIME. RUC AND NEW MET-MOS SHOWING WINDS IN THE 30 TO 35 KNOT RANGE BUT YESTERDAY WINDS WERE ALREADY SUPPOSED TO BE IN THIS RANGE AND DID NOT/HAVE NOT YET MATERIALIZED SO MAINTAINED SCA BUT DID GO 30 KNOTS SUSTAINED. FIRE WEATHER...RH FIELDS FINALLY ABOVE 40 PERCENT EXCEPT AT NGP WHERE WINDS ARE STRONGEST. AS MOST AREAS BELOW RED FLAG CRITERION NOW (AND GENERALLY HAVE BEEN SINCE 9 PM)...WILL LET RFW EXPIRE. PREV DISCUSSION... /ISSUED 738 PM CST SAT DEC 15 2007/ FIRE WEATHER...TIGHT PRESSURE GRADIENT AND RISING PRESSURES HAVE RESULTED IN WINDS STAYING UP THIS EVENING A BIT MORE THAN EXPECTED. KCRP ASOS STILL HAD A 33 KNOT GUST WITHIN THE LAST HOUR. RH FIELDS OVER THE INLAND AREAS OF THE SOUTHERN COASTAL COUNTIES ARE BELOW 40 PERCENT. THUS...EXTENDED THE RED FLAG WARNING ANOTHER TWO HOURS. FARTHER WEST...WIND GUSTS ARE STILL UP BUT RH FIELDS ARE NEAR 30 PERCENT NOW AND WINDS SHOULD CONTINUE TO DECLINE WITH TEMPERATURES SO DID NOT EXTEND THE WARNING FARTHER WEST. NORTHEASTERN COASTAL COUNTIES WIND GUSTS ARE LOWER AND RH FIELDS ARE HIGHER SO WARNING NOT EXTENDED AT THIS TIME. PREV DISCUSSION... /ISSUED 623 PM CST SAT DEC 15 2007/ UPDATE...WINDS HAVE GONE DOWN SUFFICIENTLY ENOUGH TO ALLOW WIND ADVISORY TO EXPIRE. STILL SOME BORDERLINE RED FLAG CONDITIONS (AOA 25 MPH GUSTS AND RH AOB 30 RH) OVER INLAND SECTIONS BUT WINDS SHOULD CONTINUE TO DECREASE AND RH FIELDS GO UP SO DID NOT EXTEND THE RED FLAG WARNING FOR THE INLAND AREAS...THUS THAT WAS ALLOWED TO EXPIRE. ZFPCRP UPDATE HAS BEEN ISSUED...AS WELL AS NPW. NO OTHER CHANGES AT THIS TIME. PREV DISCUSSION... /ISSUED 559 PM CST SAT DEC 15 2007/ AVIATION...VFR CONDITIONS WILL PREVAIL THROUGH SUNDAY WITH HIGH PRESSURE IN CONTROL. STRONG NW SFC WINDS WILL DIMINISH OVRNITE AND SLOWLY VEER TO THE NE AND E THROUGH SUNDAY AS THE SFC HIGH SETTLES ACROSS THE AREA. PREV DISCUSSION... /ISSUED 327 PM CST SAT DEC 15 2007/ SHORT TERM (TONIGHT THROUGH SUNDAY NIGHT)...THE CURRENT WIND ADVY IS SET TO EXPIRE AT 00Z AND THIS STILL LOOKS GOOD. BY THAT TIME...THE WINDS WL HAVE DECOUPLED AS THE LOW LVL STABILITY INCREASES. OTHERWISE...A CLEAR AND COLD NIGHT IS EXPECTED ACROSS THE CWA AS CHILLY HIGH PRESSURE CONTINUES TO ADVECT SEWD FROM THE SOUTHERN ROCKIES. FREEZING TEMPS LOOK TO BE LKLY ACROSS THE NRN HALF OF THE CWA SINCE WINDS WL CONTINUE TO DECOUPLE AND WEAKEN. AS USUAL THE GUIDANCE MINS FOR TNT ARE JUST A BIT TOO WARM. GUIDANCE HIGHS ON SUN WERE BASICALLY SVRL DEGS TOO WARM AND DECIDED TO LOWER THESE BASED UPON THE FCST SOUNDINGS. ANOTHER COOL NIGHT IS EXPECTED ON SUN NIGHT AS THE SFC RDG AXIS WL BE RIGHT OVER THE AREA...MAINTAINING LIGHT WINDS AND A VERY DRY AIRMASS. WL GO A FEW DEGREES BELOW GUIDNACE MINS FOR TMW NIGHT AS WELL. LONG TERM (MONDAY THROUGH SATURDAY)...ONSHORE FLOW WILL DEVELOP ON MONDAY. MODELS ARE PROGGING 925-850MB MOISTURE TO RETURN RATHER QUICKLY...AND EVEN NEAR SURFACE MOISTURE. MAY BE A BIT OVERDONE GIVEN HOW DRY AIRMASS IS BEHIND THIS MORNINGS COLD FRONT. NEVERTHELESS...DO ANTICIPATE CLOUD COVER TO INCREASE MONDAY AFTERNOON AND MONDAY NIGHT ACROSS THE EASTERN HALF OF THE CWA. COULD SEE SOME PATCHY LIGHT RAIN AND ISOLATED SHOWERS DEVELOPING ACROSS THE COASTAL BEND MONDAY NIGHT AND EARLY TUESDAY MORNING. A VERY WEAK SHORTWAVE TRAVERSING THE PLAINS WILL DRAG MOISTURE AXIS EAST ON TUESDAY INTO THE GULF AND SOUTHWEST LOUISIANA...WITH CLEARING ACROSS SOUTH TEXAS. TEMPS WILL CONTINUE TO MODERATE MONDAY AND TUESDAY. CLOUDS AND MOISTURE WILL RETURN BACK WEDNESDAY IN RESPONSE TO ANOTHER QUICK MOVING SHORTWAVE MOVING OUT OF THE FOUR CORNERS INTO THE SOUTHERN PLAINS. HEALTHY SUBTROPICAL JET ALSO SETS UP ACROSS SOUTH-CENTRAL TEXAS. COULD SEE SOME ISOLATED SHOWERS DEVELOPING ON WEDNESDAY ACROSS THE EASTERN 2/3RDS OF THE CWA. THE SHORTWAVE WILL PUSH A VERY WEAK FRONT INTO THE AREA ON THURSDAY...WITH A WEST FLOW TEMPORARILY DEVELOPING BEHIND IT. SO WILL ACTUALLY SEE WARMER AFTERNOON TEMPS AND COOLER LOWS THURSDAY AND THURSDAY NIGHT. BEYOND THIS MODELS DIVERGE...WITH GFS SHOWING A STRONG COLD FRONT SATURDAY AND ECMWF WETTER AND DELAYED ABOUT 24 HOURS. WILL CONTINUE TO SIDE TOWARDS THE GFS FOR CONSISTENCY. MARINE...HIGH-END SMALL CRAFT ADVY CONDITIONS WL PERSIST THROUGH MOST OF TNT GIVEN THE STRONG PRESSURE GRADIENT AND DECENT CAA. WL BOOST SEAS TO 10 TO 13 FT FOR THE OFFSHORE WATERS BASED UPON THE WIND WAVE NOMOGRAM. A GRADUAL DIMINISHMENT OF WINDS AND SEAS IS EXPECTED TO COMMENCE SUNDAY MORNING AND CONTINUE DURING THE DAY ON SUNDAY. FIRE WEATHER...WIDESPREAD RED FLAG WARNING CONDITIONS ARE CURRENTLY ONGOING. AS THE WINDS DIMINISH AND HUMIDITIES RECOVER AROUND OR SHORTLY AFTER SUNSET...RED FLAG CONDITIONS ARE EXPECTED TO END. THIS IS IN LINE WITH THE CURRENT RFW AND SO NO CHANGES ARE NEEDED AT THIS TIME. AVIATION...VFR CONDITIONS WL PREVAIL THROUGH SUNDAY NIGHT. && .PRELIMINARY POINT TEMPS/POPS... CORPUS CHRISTI 37 59 38 67 56 / 0 0 0 10 20 VICTORIA 31 57 33 64 52 / 0 0 0 0 20 LAREDO 38 64 41 68 53 / 0 0 0 0 10 ALICE 35 61 35 68 54 / 0 0 0 0 10 ROCKPORT 40 57 41 66 58 / 0 0 0 0 20 COTULLA 30 62 33 65 50 / 0 0 0 0 10 KINGSVILLE 35 60 37 69 57 / 0 0 0 10 20 NAVY CORPUS 45 58 43 68 59 / 0 0 0 10 20 && .CRP WATCHES/WARNINGS/ADVISORIES... TX...FREEZE WARNING FROM 3 AM TO 9 AM CST SUNDAY FOR THE FOLLOWING ZONES: BEE...GOLIAD...LA SALLE...LIVE OAK...MCMULLEN... VICTORIA. GM...SMALL CRAFT ADVISORY UNTIL 12 PM CST SUNDAY FOR THE FOLLOWING ZONES: WATERS BAFFIN BAY TO PORT ARANSAS 20 TO 60 NM... WATERS PORT ARANSAS TO MATAGORDA SHIP CHANNEL 20 TO 60 NM. SMALL CRAFT ADVISORY UNTIL 2 AM CST SUNDAY FOR THE FOLLOWING ZONES: BAYS AND WATERWAYS FROM BAFFIN BAY TO PORT ARANSAS... BAYS AND WATERWAYS FROM PORT ARANSAS TO PORT O`CONNOR. SMALL CRAFT ADVISORY UNTIL 6 AM CST SUNDAY FOR THE FOLLOWING ZONES: COASTAL WATERS BAFFIN BAY TO PORT ARANSAS OUT 20 NM...COASTAL WATERS PORT ARANSAS TO MATAGORDA SHIP CHANNEL OUT 20 NM. && $$ GW/86...SHORT TERM TM/95...LONG TERM tx AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE CORPUS CHRISTI TX 948 PM CST SAT DEC 15 2007 .DISCUSSION...WINDS STILL CRANKING FROM TIME TO TIME NEAR THE COAST SO FOR NOW WILL NOT UPDATE ZFP UNTIL WINDS SETTLE DOWN (SHOULD BE BY MIDNIGHT). OTHERWISE...PREVIOUS FORECAST AND/OR UPDATED GRIDS SEEM TO BE HOLDING THEIR OWN ATTM SO NO UPDATES TO THE GRIDDED TEXT PRODUCTS NEEDED AT THIS TIME EITHER. HAVE MAINTAINED THE HIGH END SCA FOR THE OFFSHORE WATERS AT THIS TIME. RUC AND NEW MET-MOS SHOWING WINDS IN THE 30 TO 35 KNOT RANGE BUT YESTERDAY WINDS WERE ALREADY SUPPOSED TO BE IN THIS RANGE AND DID NOT/HAVE NOT YET MATERIALIZED SO MAINTAINED SCA BUT DID GO 30 KNOTS SUSTAINED. && .FIRE WEATHER...RH FIELDS FINALLY ABOVE 40 PERCENT EXCEPT AT NGP WHERE WINDS ARE STRONGEST. AS MOST AREAS BELOW RED FLAG CRITERION NOW (AND GENERALLY HAVE BEEN SINCE 9 PM)...WILL LET RFW EXPIRE. && .PREV DISCUSSION... /ISSUED 738 PM CST SAT DEC 15 2007/ FIRE WEATHER...TIGHT PRESSURE GRADIENT AND RISING PRESSURES HAVE RESULTED IN WINDS STAYING UP THIS EVENING A BIT MORE THAN EXPECTED. KCRP ASOS STILL HAD A 33 KNOT GUST WITHIN THE LAST HOUR. RH FIELDS OVER THE INLAND AREAS OF THE SOUTHERN COASTAL COUNTIES ARE BELOW 40 PERCENT. THUS...EXTENDED THE RED FLAG WARNING ANOTHER TWO HOURS. FARTHER WEST...WIND GUSTS ARE STILL UP BUT RH FIELDS ARE NEAR 30 PERCENT NOW AND WINDS SHOULD CONTINUE TO DECLINE WITH TEMPERATURES SO DID NOT EXTEND THE WARNING FARTHER WEST. NORTHEASTERN COASTAL COUNTIES WIND GUSTS ARE LOWER AND RH FIELDS ARE HIGHER SO WARNING NOT EXTENDED AT THIS TIME. PREV DISCUSSION... /ISSUED 623 PM CST SAT DEC 15 2007/ UPDATE...WINDS HAVE GONE DOWN SUFFICIENTLY ENOUGH TO ALLOW WIND ADVISORY TO EXPIRE. STILL SOME BORDERLINE RED FLAG CONDITIONS (AOA 25 MPH GUSTS AND RH AOB 30 RH) OVER INLAND SECTIONS BUT WINDS SHOULD CONTINUE TO DECREASE AND RH FIELDS GO UP SO DID NOT EXTEND THE RED FLAG WARNING FOR THE INLAND AREAS...THUS THAT WAS ALLOWED TO EXPIRE. ZFPCRP UPDATE HAS BEEN ISSUED...AS WELL AS NPW. NO OTHER CHANGES AT THIS TIME. PREV DISCUSSION... /ISSUED 559 PM CST SAT DEC 15 2007/ AVIATION...VFR CONDITIONS WILL PREVAIL THROUGH SUNDAY WITH HIGH PRESSURE IN CONTROL. STRONG NW SFC WINDS WILL DIMINISH OVRNITE AND SLOWLY VEER TO THE NE AND E THROUGH SUNDAY AS THE SFC HIGH SETTLES ACROSS THE AREA. PREV DISCUSSION... /ISSUED 327 PM CST SAT DEC 15 2007/ SHORT TERM (TONIGHT THROUGH SUNDAY NIGHT)...THE CURRENT WIND ADVY IS SET TO EXPIRE AT 00Z AND THIS STILL LOOKS GOOD. BY THAT TIME...THE WINDS WL HAVE DECOUPLED AS THE LOW LVL STABILITY INCREASES. OTHERWISE...A CLEAR AND COLD NIGHT IS EXPECTED ACROSS THE CWA AS CHILLY HIGH PRESSURE CONTINUES TO ADVECT SEWD FROM THE SOUTHERN ROCKIES. FREEZING TEMPS LOOK TO BE LKLY ACROSS THE NRN HALF OF THE CWA SINCE WINDS WL CONTINUE TO DECOUPLE AND WEAKEN. AS USUAL THE GUIDANCE MINS FOR TNT ARE JUST A BIT TOO WARM. GUIDANCE HIGHS ON SUN WERE BASICALLY SVRL DEGS TOO WARM AND DECIDED TO LOWER THESE BASED UPON THE FCST SOUNDINGS. ANOTHER COOL NIGHT IS EXPECTED ON SUN NIGHT AS THE SFC RDG AXIS WL BE RIGHT OVER THE AREA...MAINTAINING LIGHT WINDS AND A VERY DRY AIRMASS. WL GO A FEW DEGREES BELOW GUIDNACE MINS FOR TMW NIGHT AS WELL. LONG TERM (MONDAY THROUGH SATURDAY)...ONSHORE FLOW WILL DEVELOP ON MONDAY. MODELS ARE PROGGING 925-850MB MOISTURE TO RETURN RATHER QUICKLY...AND EVEN NEAR SURFACE MOISTURE. MAY BE A BIT OVERDONE GIVEN HOW DRY AIRMASS IS BEHIND THIS MORNINGS COLD FRONT. NEVERTHELESS...DO ANTICIPATE CLOUD COVER TO INCREASE MONDAY AFTERNOON AND MONDAY NIGHT ACROSS THE EASTERN HALF OF THE CWA. COULD SEE SOME PATCHY LIGHT RAIN AND ISOLATED SHOWERS DEVELOPING ACROSS THE COASTAL BEND MONDAY NIGHT AND EARLY TUESDAY MORNING. A VERY WEAK SHORTWAVE TRAVERSING THE PLAINS WILL DRAG MOISTURE AXIS EAST ON TUESDAY INTO THE GULF AND SOUTHWEST LOUISIANA...WITH CLEARING ACROSS SOUTH TEXAS. TEMPS WILL CONTINUE TO MODERATE MONDAY AND TUESDAY. CLOUDS AND MOISTURE WILL RETURN BACK WEDNESDAY IN RESPONSE TO ANOTHER QUICK MOVING SHORTWAVE MOVING OUT OF THE FOUR CORNERS INTO THE SOUTHERN PLAINS. HEALTHY SUBTROPICAL JET ALSO SETS UP ACROSS SOUTH-CENTRAL TEXAS. COULD SEE SOME ISOLATED SHOWERS DEVELOPING ON WEDNESDAY ACROSS THE EASTERN 2/3RDS OF THE CWA. THE SHORTWAVE WILL PUSH A VERY WEAK FRONT INTO THE AREA ON THURSDAY...WITH A WEST FLOW TEMPORARILY DEVELOPING BEHIND IT. SO WILL ACTUALLY SEE WARMER AFTERNOON TEMPS AND COOLER LOWS THURSDAY AND THURSDAY NIGHT. BEYOND THIS MODELS DIVERGE...WITH GFS SHOWING A STRONG COLD FRONT SATURDAY AND ECMWF WETTER AND DELAYED ABOUT 24 HOURS. WILL CONTINUE TO SIDE TOWARDS THE GFS FOR CONSISTENCY. MARINE...HIGH-END SMALL CRAFT ADVY CONDITIONS WL PERSIST THROUGH MOST OF TNT GIVEN THE STRONG PRESSURE GRADIENT AND DECENT CAA. WL BOOST SEAS TO 10 TO 13 FT FOR THE OFFSHORE WATERS BASED UPON THE WIND WAVE NOMOGRAM. A GRADUAL DIMINISHMENT OF WINDS AND SEAS IS EXPECTED TO COMMENCE SUNDAY MORNING AND CONTINUE DURING THE DAY ON SUNDAY. FIRE WEATHER...WIDESPREAD RED FLAG WARNING CONDITIONS ARE CURRENTLY ONGOING. AS THE WINDS DIMINISH AND HUMIDITIES RECOVER AROUND OR SHORTLY AFTER SUNSET...RED FLAG CONDITIONS ARE EXPECTED TO END. THIS IS IN LINE WITH THE CURRENT RFW AND SO NO CHANGES ARE NEEDED AT THIS TIME. AVIATION...VFR CONDITIONS WL PREVAIL THROUGH SUNDAY NIGHT. && .PRELIMINARY POINT TEMPS/POPS... CORPUS CHRISTI 35 59 38 67 56 / 0 0 0 10 20 VICTORIA 31 57 33 64 52 / 0 0 0 0 20 LAREDO 37 64 41 68 53 / 0 0 0 0 10 ALICE 33 61 35 68 54 / 0 0 0 0 10 ROCKPORT 39 57 41 66 58 / 0 0 0 0 20 COTULLA 29 62 33 65 50 / 0 0 0 0 10 KINGSVILLE 33 60 37 69 57 / 0 0 0 10 20 NAVY CORPUS 42 58 43 68 59 / 0 0 0 10 20 && .CRP WATCHES/WARNINGS/ADVISORIES... TX...FREEZE WARNING FROM 2 AM TO 9 AM CST SUNDAY FOR THE FOLLOWING ZONES: BEE...GOLIAD...LA SALLE...LIVE OAK...MCMULLEN... VICTORIA. RED FLAG WARNING UNTIL 10 PM CST THIS EVENING FOR THE FOLLOWING ZONES: KLEBERG...NUECES...SAN PATRICIO. GM...SMALL CRAFT ADVISORY UNTIL 12 PM CST SUNDAY FOR THE FOLLOWING ZONES: WATERS BAFFIN BAY TO PORT ARANSAS 20 TO 60 NM... WATERS PORT ARANSAS TO MATAGORDA SHIP CHANNEL 20 TO 60 NM. SMALL CRAFT ADVISORY UNTIL 2 AM CST SUNDAY FOR THE FOLLOWING ZONES: BAYS AND WATERWAYS FROM BAFFIN BAY TO PORT ARANSAS... BAYS AND WATERWAYS FROM PORT ARANSAS TO PORT O`CONNOR. SMALL CRAFT ADVISORY UNTIL 6 AM CST SUNDAY FOR THE FOLLOWING ZONES: COASTAL WATERS BAFFIN BAY TO PORT ARANSAS OUT 20 NM...COASTAL WATERS PORT ARANSAS TO MATAGORDA SHIP CHANNEL OUT 20 NM. && $$ TE/81...MESO/AVIATION GW/86...SYNOPTIC/GRIDS tx AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE AUSTIN/SAN ANTONIO TX 136 AM CST SAT DEC 15 2007 .UPDATE... JUST DID A QUICK UPDATE FOR THUNDERSTORMS AND HIGHER POPS FOR THE NORTHEAST QUARTER OF THE CWA OVERNIGHT. && PREV DISCUSSION... /ISSUED 928 PM CST FRI DEC 14 2007/ UPDATE... UPDATED FORECAST TO INCREASE MIN TEMPS TONIGHT BY 1-3 DEGREES BASED ON LATEST GUIDANCE AND TRENDS. ALSO TWEAKED 1ST PERIOD POPS DOWN BY 10-20 PERCENT ACROSS THE WESTERN TWO-THRIDS BASED ON RADAR TRENDS AND LATEST RUC AND LOCAL WRF OUTPUT. PATCHES OF DENSE FOG WILL CONTINUE...BUT A DENSE FOG ADVISORY IS NOT ANTICIPATED AT THIS TIME AS THE LOWER BOUNDARY LAYER WINDS ARE LIKELY TOO HIGH. NEW SUITE OF PRODUCTS OUT SHORTLY. && .PRELIMINARY POINT TEMPS/POPS... AUSTIN CAMP MABRY 60 35 61 35 61 / 10 0 0 0 0 AUSTIN BERGSTROM INTL AIRPORT 61 30 59 26 61 / 10 0 0 0 0 DEL RIO INTL AIRPORT 64 34 59 36 62 / - 0 0 0 0 SAN ANTONIO INTL AIRPORT 66 30 61 32 59 / - 0 0 0 0 && .EWX WATCHES/WARNINGS/ADVISORIES... WIND ADVISORY FROM 9 AM THIS MORNING TO 6 PM CST THIS AFTERNOON FOR THE FOLLOWING COUNTIES: ATASCOSA...BANDERA...BASTROP...BEXAR... BLANCO...BURNET...CALDWELL...COMAL...DE WITT...DIMMIT...EDWARDS... FAYETTE...FRIO...GILLESPIE...GONZALES...GUADALUPE...HAYS...KARNES... KENDALL...KERR...KINNEY...LAVACA...LEE...LLANO...MAVERICK... MEDINA...REAL...TRAVIS...UVALDE...VAL VERDE...WILLIAMSON...WILSON... ZAVALA. RED FLAG WARNING FROM NOON TODAY TO 5 PM CST THIS AFTERNOON FOR THE FOLLOWING COUNTIES: KINNEY...MAVERICK...VAL VERDE. && $$ 26/18 tx AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE AMARILLO TX 1144 PM CST FRI DEC 14 2007 .AVIATION... FOR THE 06Z TAFS...CURRENT RUC UPPER AIR ANALYSIS INDICATES UPPER TROUGH OVER EASTERN NEW MEXICO. THIS TROUGH IS STILL ON TRACK TO LIFT NORTHEAST AND WILL PUSH EAST OF THE PANHANDLES SAT. CURRENT RADAR IMAGERY SHOWS BANDS OF LIGHT SNOW LIFTING ACROSS THE PANHANDLES AND EXPECT SNOW TO CONTINUE ACROSS THE AREA OVERNIGHT. MODEL SOUNDINGS AND TIME/HEIGHT CROSS SECTIONS SHOW DRY AIR MOVING IN RAPIDLY ON THE BACKSIDE OF THIS SYSTEM...WHICH WILL END PRECIP CHANCES BY AROUND 11-12Z. BEYOND THIS...EXPECT CIGS TO IMPROVE TO VFR BY AROUND 16-17Z WITH SKC CONDITIONS BY 00Z. AS FOR WINDS...GUSTY NORTHWEST WINDS WILL CONTINUE OVERNIGHT AND BACK MORE TOWARD THE WEST AND DIMINISH TO UNDER 10 KTS BY THE END OF THE 24 HOUR FCST. CLK && .PREV DISCUSSION... /ISSUED 616 PM CST FRI DEC 14 2007/ .AVIATION... MAIN AVIATION CONCERN CENTERS ON TIMING OF WINTRY PRECIP OVER THE FIRST 12 HOURS OF THE FORECAST. DEEPENING UPPER TROUGH OVER THE FOUR CORNERS WILL CONTINUE TO LIFT TO THE NORTHEAST OVERNIGHT AND HEAD TOWARD ARKANSAS SAT. MEANWHILE AN ASSOCIATED S/WV WILL ROUND THE BASE OF THE TROUGH...PROVIDING ADDITIONAL LIFT ACROSS THE TEXAS PANHANDLES TONIGHT. A SURFACE FRONT WAS CONTINUING TO SLIDE SOUTH ACROSS THE TEXAS PANHANDLE WHICH WILL BRING IN COOLER AIR. FORECAST SOUNDING ANALYSIS INDICATE PRECIP TYPE MAINLY AS SNOW SO EXPECT ANY FZDZ TO CHANGE OVER TO SNOW THIS EVENING. EXPECT LIGHT SNOW TO IMPACT THE TERMINALS THIS EVENING AND OVERNIGHT WITH LIFR AND IFR CONDITIONS. SNOW WILL TAPER OFF BY EARLY SAT MORNING AS THE UPPER TROUGH LIFTS EAST OF THE AREA. MODEL FORECAST SOUNDINGS AND TIME/HEIGHT CROSS SECTIONS CONTINUE TO SHOW AMPLE MOISTURE LINGERING IN THE LLVLS SO GRADUALLY INDICATED IMPROVING CIGS TOWARD THE END OF THE FCST WITH VFR CONDITIONS EXPECTED BY AROUND 20Z. CLK PREV DISCUSSION... /ISSUED 349 PM CST FRI DEC 14 2007/ DISCUSSION... MADE FEW CHANGES TO THE SHORT TERM SINCE THE NOON UPDATE EARLIER TODAY. DID UP POPS A FEW POINTS ACROSS THE EASTERN PANHANDLES FOR TONIGHT. COLD FRONT IS SLOWLY PUSHING SOUTHEAST ACROSS THE PANHANDLES. APPEARS THE FRONT IS CURRENTLY LOCATED SOUTH OF A LINE FROM GUYMON TO DALHART. AHEAD OF THE FRONT...A FEW OB SITES STILL REPORTING VERY LIGHT FREEZING DRIZZLE OR FOG...BUT THIS SHOULD TRANSITION TO SNOW AS THE FRONT MOVES THROUGH THE AREA. THINKING THE FRONT SHOULD REACH AMARILLO AND THE SOUTHERN TEXAS PANHANDLE AROUND 00Z. STILL APPEARS THAT THE EASTERN PANHANDLES ARE IN LINE FOR THE MOST SNOWFALL ACCUMULATIONS WITH LESSER AMOUNTS TO THE WEST. HAD SOME CONCERN THAT THE SOUTHEAST TEXAS PANHANDLE MAY NOT REALIZE THE 4 TO 5 INCH SNOW TOTALS...BUT THIS AREA WILL FALL IN THE LEFT EXIT REGION OF THE UPPER JET SO SOME ENHANCEMENT COULD TAKE PLACE LEADING TO LOCALIZED HEAVY SNOW. SOME OF THE SNOW BANDS WILL BE CAPABLE OF PRODUCING 1 TO 2 INCHES OF SNOW PER HOUR AS THE UPPER TROUGH MOVES THROUGH LATER THIS AFTERNOON AND EVENING. AM SOMEWHAT CONCERNED ABOUT THE RECENT NAM12 SOLUTION THAT PAINTS MORE SNOW ALONG THE BASE OF THE TROUGH AS IT PUSHES THROUGH THE AREA TOMORROW MORNING. ALTHOUGH IT DOES APPEAR THAT THE VORT MAX ASSOCIATED WITH THE PRECIP WILL REMAIN SOUTH OF OUR CWA. SO STILL ANTICIPATE THE SNOW DECREASING AFTER 12Z...WITH A FEW FLURRIES LINGERING ACROSS THE EASTERN PANHANDLES POSSIBLY INTO THE 18Z TIME FRAME. DO NOT ANTICIPATE ANY ACCUMULATIONS WORTHY OF EXTENDING THE WINTER STORM WARNING THROUGH 18Z HOWEVER. CURRENT THINKING IS TO ALLOW THE WINTER WEATHER ADVISORY AND WINTER STORM WARNING TO EXPIRE AT 12Z. AFTER THIS EVENT FINALLY SHUFFLES OFF ITS MORTAL COIL...THE REST OF THE PACKAGE IS RELATIVELY QUIET. HIGH TEMPS WILL REMAIN WITHIN A FEW DEGREES OF FREEZING TOMORROW. THE UPPER TROUGH WILL GIVE WAY TO BRIEF NORTHERLY FLOW AHEAD OF THE APPROACHING RIDGE. THE NORTHERLY SFC WINDS WILL BACK TO THE WEST ON SUNDAY AS A WEAK SFC HIGH BUILDS IN BEHIND THE EXITING FRONT. THIS WILL HELP HIGH TEMPS WARM INTO THE LOW 40S ON SUNDAY. SFC TROUGH THEN TRIES TO DEVELOP MONDAY INTO TUESDAY...ALLOWING THE SOUTHWEST WINDS TO INCREASE DURING THE AFTERNOON ON MONDAY. ANY WARM AIR ADVECTION SHOULD HELP MELT LINGERING SNOW...SO THINKING TEMPS WILL INCREASE INTO THE 50 DEGREE RANGE MONDAY AND TUESDAY. DID NOTICE THAT GUIDANCE WAS KEEPING HIGH TEMPS COOL ACROSS THE NORTHEAST PANHANDLES WHERE THE HEAVIEST SNOW IS EXPECTED. CONTINUED THIS TREND IN THE GRIDS THROUGH MONDAY...BUT THINKING THE SNOW SHOULD NO LONGER BE AN ISSUE BY TUESDAY. MODELS HINT AT ANOTHER UPPER WAVE AND COLD FRONT THAT MAY IMPACT THE PANHANDLES WEDNESDAY INTO THURSDAY. THIS TROUGH LOOKS VERY PROGRESSIVE PROVIDING A SHORT WINDOW FOR PRECIP. MODELS ARE DRY AT THIS POINT...SO WAS CONTENT TO LEAVE THE 10 POPS IN FOR NOW AND BEGIN TRENDING UP IF THE TROUGH DEEPENS MORE THAN MODELS CURRENTLY SUGGEST. APPEARS THE COLD FRONT ASSOCIATED WITH THIS SYSTEM WILL MOVE THROUGH THE PANHANDLES LATE WEDNESDAY INTO THURSDAY...SO REFLECTED THIS IDEA IN THE HIGH TEMPS ON THURSDAY. IN FACT...TEMPS COULD BE WARMER THAN GUIDANCE SUGGESTS ON WEDNESDAY AS MODELS SHOW A LEE TROUGH DEVELOPING AHEAD OF THE FRONT PROVIDING 15 TO 25KT WESTERLY WINDS. OTHERWISE...WILL CONTINUE TO MONITOR THE SNOWFALL AND FREEZING DRIZZLE AND MAKE UPDATES TO THE FORECAST AS NEEDED. && AMA WATCHES/WARNINGS/ADVISORIES... TX...WINTER STORM WARNING UNTIL 6 AM CST SATURDAY FOR THE FOLLOWING ZONES: COLLINGSWORTH...DONLEY...GRAY...HEMPHILL... LIPSCOMB...OCHILTREE...ROBERTS...WHEELER. WINTER WEATHER ADVISORY UNTIL 6 AM CST SATURDAY FOR THE FOLLOWING ZONES: ARMSTRONG...CARSON...DALLAM...DEAF SMITH... HANSFORD...HARTLEY...HUTCHINSON...MOORE...OLDHAM...POTTER... RANDALL...SHERMAN. OK...WINTER STORM WARNING UNTIL 6 AM CST SATURDAY FOR THE FOLLOWING ZONES: BEAVER. WINTER WEATHER ADVISORY UNTIL 6 AM CST SATURDAY FOR THE FOLLOWING ZONES: CIMARRON...TEXAS. && $$ 15/05 tx AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE AUSTIN/SAN ANTONIO TX 1134 PM CST FRI DEC 14 2007 .AVIATION... ISENTROPIC LIFT/OVERRUNNING CONTINUES ACROSS THE REGION WITH THE APPROACH OF THE UPPER LEVEL STORM SYSTEM. SHOWERS ARE INCREASING IN COVERAGE SOUTHWEST OF KSSF AND KSAT. THE RUC AND NAM MODELS INDICATE THE SHOWER ACTIVITY WILL CONTINUE TO INCREASE IN COVERAGE AS THE AREA SHIFTS EASTWARD. EXPECT SCATTERED SHOWERS TO IMPACT THE I-35 TERMINALS THROUGH 09Z. ATTM IFR/LIFR CONDITIONS PREVAIL AT KSSF...KSAT AND KAUS WITH MVFR CONDITIONS AT KDRT. CIGS AND VSBYS WILL BEGIN TO IMPROVE TO MVFR AFTER 09Z FOR THE I-35 TERMINALS AS A PRE-FRONTAL SFC TROF MOVES WESTWARD ACROSS THE REGION. CONDITIONS WILL IMPROVE RAPIDLY TO VFR WITH THE PASSAGE OF THE COLD FRONT. FROPA IS FCST FOR 13Z AT KDRT AND KAUS...AND 14Z AT KSAT AND KSSF. WINDS WILL SHIFT TO THE NORTHWEST WITH THE FROPA INITIALLY AT SPEEDS OF 10 TO 15 KTS. DOWNWARD MIXING WILL CAUSE WIND SPEEDS TO INCREASE TO 20 TO 30 KTS BY LATE MORNING. STRONG SFC WINDS SATURDAY AFTERNOON WILL RESULT IN FRICTIONAL LOW LEVEL TURBULENCE. WINDS WILL DIMINISH TO AROUND 10 KTS AFTER SUNSET SATURDAY. && .PREV DISCUSSION... /ISSUED 928 PM CST FRI DEC 14 2007/ UPDATE... UPDATED FORECAST TO INCREASE MIN TEMPS TONIGHT BY 1-3 DEGREES BASED ON LATEST GUIDANCE AND TRENDS. ALSO TWEAKED 1ST PERIOD POPS DOWN BY 10-20 PERCENT ACROSS THE WESTERN TWO-THRIDS BASED ON RADAR TRENDS AND LATEST RUC AND LOCAL WRF OUTPUT. PATCHES OF DENSE FOG WILL CONTINUE...BUT A DENSE FOG ADVISORY IS NOT ANTICIPATED AT THIS TIME AS THE LOWER BOUNDARY LAYER WINDS ARE LIKELY TOO HIGH. NEW SUITE OF PRODUCTS OUT SHORTLY. PREV DISCUSSION... /ISSUED 348 PM CST FRI DEC 14 2007/ DISCUSSION... ISENTROPIC LIFT AND WARM ADVECTION CONTINUES ACROSS SOUTH CENTRAL TEXAS THIS AFTERNOON AS WARM FRONT MOVES ACROSS THE TEXAS COASTAL BEND AHEAD OF UPPER TROUGH AND COLD FRONT MOVING INTO THE SOUTHERN ROCKIES. SHOWERS AND DRIZZLE WILL CONTINUE TONIGHT DUE WARM FRONT TO SOUTHEAST AND UPPER TROUGH/COLD FRONT APPROACHING FROM WEST. HAVE INCLUDED A SLIGHT CHANCE OF THUNDER ACROSS THE EAST DUE TO UPPER JET DYNAMICS AND PROXIMITY TO WARM FRONT. COULD EVEN BE SOME SMALL HAIL AND HEAVY RAINS. AREAS OF FOG AS MODERATE LOW LEVEL JET KEEPS AIRMASS SLIGHTLY MIXED, ALTHOUGH SOME PATCHY DENSE FOG CAN BE EXPECTED. COLD FRONT WILL MOVE THROUGH THE AREA DURING THE OVERNIGHT INTO THE EARLY MORNING HOURS. THIS WILL CLEAR THE FOG AND CLOUDS, ALTHOUGH SOME WRAPAROUND CLOUDS WILL OCCUR ACROSS THE NORTH ON SATURDAY AS UPPER TROUGH PASSES ACROSS TEXAS. NORTHWEST WINDS OF 20 TO 30 MPH WITH GUSTS TO 40 MPH WILL DEVELOP AFTER SUNRISE ON SATURDAY AS SOLAR HEATING AND SUBSIDENCE MIX STRONGER WINDS TO THE SURFACE. THUS, HAVE ISSUED A WIND ADVISORY SATURDAY. DOWNSLOPE WINDS WILL COUNTER ACT THE COLD ADVECTION AND WILL ALLOW HIGHS TO BE NEAR AVERAGE. WINDS WILL DECREASE RAPIDLY AFTER SUNSET LEADING TO FREEZING TEMPERATURES ACROSS A WIDE AREA OF SOUTH CENTRAL TEXAS BY SUNDAY MORNING. SOME AREAS MAY EXPERIENCE A HARD FREEZE, ESPECIALLY IN THE HILL COUNTRY. COLD ADVECTION WILL END BY SUNDAY WITH HIGHS SLIGHTLY BELOW AVERAGE AS THE SURFACE HIGH SETTLES OVER CENTRAL TEXAS. TEMPERATURES NEAR OR SLIGHTLY BELOW FREEZING CAN BE EXPECTED AGAIN EARLY MONDAY MORNING. A ZONAL FLOW ALOFT WILL PERSIST THE REMAINDER OF THE WEEK ALLOWING A SERIES OF FAIRLY WEAK SHORT-WAVES TO MOVE ACROSS THE CENTRAL STATES. THE SURFACE HIGH WILL MOVE OFF TO THE EAST ALLOWING A SOUTHERLY TO DEVELOP ON MONDAY AND PERSIST INTO THURSDAY. TEMPERATURES WILL SHOW A WARMING TREND TO ABOUT 10 DEGREES ABOVE AVERAGE WEDNESDAY AND THURSDAY. A PACIFIC COLD FRONT WILL MOVE THROUGH ON THURSDAY TAKING MAINLY LOW TEMPERATURES BACK TOWARD AVERAGE. ENOUGH MOISTURE AND LIFT SUGGESTS 10 TO 20 POPS EASTERN AREAS WEDNESDAY INTO THURSDAY. DRY AGAIN ON FRIDAY IN WAKE OF FRONT. MODELS SUGGEST ANOTHER STORM SYSTEM ACROSS THE SOUTHERN PLAINS NEXT WEEKEND JUST BEYOND THIS FORECAST PERIOD. HAVE GENERALLY GONE WITH THE MAV/MEX TEMPERATURES, EXCEPT 1 TO 3 DEGREES COLDER SUNDAY NIGHT INTO MONDAY MORNING DUE LOWER DEWPOINTS AND LIGHT WINDS. FIRE WEATHER... HAVE ISSUED A RED FLAG WARNING FOR THE RIO GRANDE PLAINS FOR SATURDAY AFTERNOON DUE 20 FOOT WINDS ABOVE 15 MPH AND RELATIVE HUMIDITIES BELOW 25 PERCENT. OTHER PARTS OF SOUTH CENTRAL TEXAS MAY SEE THESE CONDITIONS FOR AN HOUR AND WERE NOT INCLUDED. && .PRELIMINARY POINT TEMPS/POPS... AUSTIN CAMP MABRY 49 60 35 61 35 / 40 10 0 0 0 AUSTIN BERGSTROM INTL AIRPORT 50 61 30 59 26 / 50 10 0 0 0 DEL RIO INTL AIRPORT 45 64 34 59 36 / 10 - 0 0 0 SAN ANTONIO INTL AIRPORT 50 66 30 61 32 / 30 - 0 0 0 && .EWX WATCHES/WARNINGS/ADVISORIES... WIND ADVISORY FROM 9 AM TO 6 PM CST SATURDAY FOR THE FOLLOWING COUNTIES: ATASCOSA...BANDERA...BASTROP...BEXAR...BLANCO...BURNET... CALDWELL...COMAL...DE WITT...DIMMIT...EDWARDS...FAYETTE...FRIO... GILLESPIE...GONZALES...GUADALUPE...HAYS...KARNES...KENDALL...KERR... KINNEY...LAVACA...LEE...LLANO...MAVERICK...MEDINA...REAL...TRAVIS... UVALDE...VAL VERDE...WILLIAMSON...WILSON...ZAVALA. RED FLAG WARNING FROM 12 PM TO 5 PM CST SATURDAY FOR THE FOLLOWING COUNTIES: KINNEY...MAVERICK...VAL VERDE. && $$ 11/13 tx AREA FORECAST DISCUSSION...CORRECTED NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI 224 PM CST SUN DEC 16 2007 .SHORT TERM... MAIN SHORT TERM PROBLEM IS SKY COVER. STRATUS HOLDING TIGHT OVER AREAS WEST OF MADISON. ONLY MODEL TO HAVE REASONABLE DEPICTION OF LOW LEVEL RH IS THE RUC. RUC TRIES TO INCREASE 925 MB OVER SOUTHEAST WISCONSIN AS SUBSIDENCE FROM STRONG LOW OVER THE NORTHEAST U.S. WEAKENS. SATELLITE SHOWS CLOUDS TRYING TO PUSH SOUTH FROM NORTHEAST WISCONSIN BUT ERODES. EXPECT THIS TREND TO CONTINUE...BUT AS SUBSIDENCE WEAKENS CLOUDS MAY YET MAKE IT INTO THE SOUTHEAST. WITH CLEAR SKIES EARLY...TEMPS SHOULD DROP OVER THE FRESH SNOW COVER TO BELOW MOS MINS. MOS TEMPS APPEAR TOO WARM FOR MONDAY. WEAK SHORTWAVE MOVES ACROSS THE UPPER GREAT LAKES MONDAY. MID/UPPER LEVEL FLOW BECOMES MORE ZONAL WITH A SERIES OF WEAK SHORTWAVES. EXCELLENT AGREEMENT WITH ECMWF AND GFS FOR ANOTHER WEAK SHORTWAVE ACROSS THE UPPER GREAT LAKES TUESDAY. LIGHT SNOW FROM THIS MAINLY IN AREAS TO THE NORTH. .LONG TERM... THEN A SHORTWAVE PUSHING ACROSS THE MID MISSISSIPPI VALLEY THURSDAY. GFS HAS A MORE CLOSED SURFACE LOW PUSHING ACROSS SOUTHERN INDIANA WITH LITTLE OR NO QPF OVER SOUTHERN WISCONSIN. ECMWF HAS A MORE NORTH SOUTH OPEN TROF...SPREADING MORE QPF...UP TO 0.30 INCH ACROSS THE IL BORDER...WITH SOME QPF EVEN ACROSS OUR NORTH AREAS. WILL TREND TOWARD ECMWF AS THIS SEEMS MORE REASONABLE WITH UPPER PATTERN...ALTHOUGH QPF MAY BE OVERDONE. STRONG SHORTWAVE FOR NEXT WEEKEND WITH BOTH ECMWF AND GFS HAVING A LOW TRACK THAT WOULD PUT A RAIN SNOW MIX POTENTIAL IN THE FAR SOUTHEAST. && .AVIATION... MAIN ISSUE FOR TAFS IS TRYING TO GET A HANDLE ON MVFR/BORDERLINE IFR CLOUD DECK MOVING SLOWLY SOUTH SOUTHEAST ACROSS WISCONSIN. MOISTURE TRAPPED BELOW SHALLOW INVERSION. INVERSION EXPECTED TO LOWER TONIGHT AND STRENGTHEN WITH SATURATED BOUNDARY LAYER AT KMSN. INVERSION AND MOISTURE NOT AS STRONG AT KMKE. FEEL NONE OF THE MODELS HAVE A DECENT HANDLE ON THEIR QUICK DEPARTURE OF THE STRATUS DECK ACROSS THE REGION TONIGHT. SO...WILL UPDATE TAFS TO CARRY PREVAILING MVFR/BORDERLINE IFR CEILINGS AT KMSN THROUGH THE NIGHT...WITH SOME MVFR/IFR VISIBILITIES DUE TO FOG POSSIBLE. WILL KEEP KMKE AND KENW WITH PREVAILING SCATTERED CLOUDS...WITH SOME BROKEN MVFR CEILINGS POSSIBLE. DECK SHOULD RAISE AT KMSN MONDAY MORNING. && .MARINE... SMALL CRAFT ADVISORY EXPIRES AT 03Z MONDAY. MIXING OF 25 KNOT WINDS DOWN TO SURFACE FROM 1000 FEET SHOULD SUBSIDE AFTER 00Z MONDAY...AS INVERSION LOWERS. HIGH WAVES TOWARD THE OPEN WATERS SHOULD THEN SUBSIDE AS OFFSHORE WINDS DECREASE. && .MKX WATCHES/WARNINGS/ADVISORIES... WI...NONE. LM...SMALL CRAFT ADVISORY UNTIL 9 PM CST THIS EVENING FOR LMZ643>646. && $$ CORRECTED ENDING TIME OF SMALL CRAFT ADVISORY IN MARINE SECTION SHORT/LONG TERM...HENTZ AVIATION/MARINE...WOOD wi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LA CROSSE WI 1132 AM CST SUN DEC 16 2007 .UPDATE... UPDATED EARLIER TO SIGNIFICANTLY DELAY ANY CLEARING INTO THE FORECAST AREA...IN FACT...LATEST THINKING BASED ON RUC13 LOWEST 100MB MOISTURE FIELDS...TIME OF YEAR /CLIMATOLOGY/...AND SATELLITE IMAGERY SUGGESTS IT WILL BE WELL INTO THE NIGHTTIME BEFORE ANY CLEARING TAKES PLACE. ONLY EXCEPTION TO THIS WILL BE WHERE STRATUS BECOMES THIN ENOUGH TO PUNCH HOLES IN IT. NOT SEEING THIS AT ALL PER SATELLITE IMAGERY. DESPITE OTHER MODELS BEST INTENTIONS ON DRYING THE BOUNDARY LAYER AND LOW LEVELS...DON/T FEEL IT WILL HAPPEN ANYTIME SOON GIVEN VERY LOW SUN ANGLES...APPROACH OF SHORTWAVE LOW LEVEL RIDGING /DECREASING MIXING/ AND INCREASING WARM ADVECTION AFTER 00Z /STRENGTHENING LOW LEVEL INVERSION/...SO WILL LIKELY BE CLOUDY INTO MUCH OF THE NIGHT. EVEN IF WE CLEAR...LOW LEVEL WARM/MOIST ADVECTION SUGGESTS FOG WILL BECOME RAMPANT AS IT DID THIS MORNING UNDER SIMILAR CONDITIONS OVER THE DAKOTAS. WIDESPREAD FLURRY ACTION WITH THE LOW CEILINGS AS WELL. EXPECT THIS TO CONTINUE THROUGH THE DAY AS WELL. WILL NEED TO VISIT HIGHS THIS AFTERNOON HERE SOON...AND MAY NEED TO PULL BACK ON AFTERNOON TEMPERATURES. BINAU && .PREV DISCUSSION... /ISSUED 215 AM CST SUN DEC 16 2007/ SHORT TERM...THROUGH TUESDAY MAIN FORECAST CONCERN IS WITH ANY PRECIPITATION CHANCES LATE TONIGHT INTO MONDAY AND AGAIN MONDAY NIGHT INTO TUESDAY. SURFACE ANALYSIS EARLY THIS MORNING SHOWS LOW PRESSURE OVER SOUTHEAST INDIANA. A WEAK HIGH PRESSURE RIDGE EXTENDED FROM MANITOBA AND ONTARIO SOUTH INTO LOWER PLAINS STATES. RELATIVELY QUIET PERIOD EXPECTED WITH ONLY SOME MINOR PRECIPITATION EVENTS TO DEAL WITH. BOTH THE NAM AND GFS INDICATE A SHORT WAVE TROUGH AND CLOSED UPPER LEVEL LOW WILL TRACK ACROSS SOUTHERN CANADA LATE TONIGHT AND MONDAY. THIS SYSTEM WILL BE CLOSE ENOUGH TO ALLOW ABOUT 8 PVU/S OF VORTICITY ADVECTION IN THE 500 TO 300 MB LAYER TO CROSS OVER THE REGION. THIS IS ABOUT ALL THE FORCING THERE IS WITH THIS SYSTEM. TIME/HEIGHT CROSS SECTIONS SHOW A LOT OF DRY AIR BELOW 500 MB SO ONLY EXPECTING AN INCREASE IN HIGH CLOUDS FROM THIS SYSTEM. DIFFERENCES IN THE MODELS WITH THE HANDLING OF THE NEXT SHORT WAVE TROUGH FOR MONDAY NIGHT INTO TUESDAY. THE GFS IS STRONGER AND FARTHER SOUTH WITH THE WAVE THAN EITHER THE NAM OR ECMWF. MODEL DISCUSSION FROM HPC INDICATES THE GFS AT THIS POINT LOOKS TO BE THE OUTLIER WITH THIS WAVE. DESPITE THIS...WILL LEAVE IN THE SMALL POPS INTRODUCED ACROSS THE NORTH FOR CONTINUITY AND TO AGREE WITH OFFICES TO THE EAST. TIME/HEIGHT CROSS SECTION FOR KMDZ FROM THE GFS SHOWS ONLY A MODEST INCREASE IN THE MOISTURE BELOW 500 MB WITH THIS SYSTEM RAISING QUESTIONS AS TO WHETHER SATURATION WILL OCCUR. IF THE GFS DOES END UP BEING CORRECT...IT DOES SHOW MODERATE QG CONVERGENCE WITH THIS WAVE ALONG WITH 1-2 MICROBARS/S OF UPGLIDE ON THE 280K ISENTROPIC SURFACE. IF THIS SYSTEM PRODUCES ANY PRECIPITATION ACROSS THE FORECAST AREA...IT WILL LIKELY BE NOTHING MORE THAN SOME FLURRIES OR VERY LIGHT SNOW. LONG TERM...TUESDAY NIGHT THROUGH SATURDAY BOTH THE GFS AND ECMWF CONTINUE TO INDICATE A SURFACE LOW COMING OUT OF THE LOWER PLAINS BUT ARE NOW TRACKING THIS MORE EAST/NORTHEAST INTO THE OHIO RIVER VALLEY. THIS WOULD AGAIN PUT THE AREA ON THE NORTHERN FRINGE OF THE SYSTEM...SIMILAR TO THE SYSTEM THAT JUST PAST BY SATURDAY. ANOTHER SYSTEM LOOKS TO COME OUT OF THE LOWER PLAINS FOR THE UPCOMING WEEKEND POSSIBLY SPREADING SOME PRECIPITATION INTO THE AREA BY SATURDAY. CURRENT DATABASE HAS A GOOD HANDLE ON BOTH OF THESE SYSTEMS AND NO CHANGES ARE PLANNED. AVIATION... LOW LEVEL MOISTURE TRAPPED UNDER AN INVERSION/HIGH PRESSURE HAS LEAD TO A BROAD AREA OF LOW CLOUDS //MOSTLY SUB 1 KFT// ACROSS MN AND WESTERN WI. WITH THE INVERSION HOLDING FAST FOR MUCH OF THE DAY...DO NOT EXPECT THE MVFR/IFR CEILINGS TO MIX OUT...RATHER THEY WILL TRANSITION FROM WEST TO EAST AS THAT RIDGE OF HIGH PRESSURE MOVES OVERHEAD FOR TONIGHT. CURRENT TIMING WOULD HAVE KRST START TO SCATTER OUT BY 18Z...AND NEAR 21Z FOR KLSE. SOME RESTRICTIONS TO VSBY WILL BE POSSIBLE THIS MORNING...DUE TO FG/HZ/SN-...MOSTLY ONLY AS LOW AS 3 TO 5SM. SOME HINTS THAT MORE LOW STRATUS COULD DEVELOP TONIGHT...BUT MODEL TRENDS ARE TO SIGNIFICANTLY SHALLOW OUT THE LOW SATURATION...ALONG WITH BRINGING IN MORE SUBSIDENCE ALOFT...SO WILL KEEP CONDITIONS SKC FOR NOW. ARX WATCHES/WARNINGS/ADVISORIES... WI...NONE. MN...NONE. IA...NONE. $$ SHORT/LONG TERM...04 && .ARX WATCHES/WARNINGS/ADVISORIES... WI...NONE. MN...NONE. IA...NONE. && $$ wi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LA CROSSE WI 1216 PM CST SAT DEC 15 2007 .UPDATE... UPDATED A LITTLE WHILE AGO TO INCREASE SNOW AMOUNTS IN OUR FAR SOUTH...NAMELY GRANT COUNTY...ESPECIALLY THE SOUTHERN HALF OF GRANT COUNTY WHERE LATEST /12Z AND 15Z/ RUC AND 12Z WRF DATA SUGGESTS 500-600MB FRONTOGENESIS REGION WILL LINGER INTO THE EARLY EVENING...PRODUCING OCCASIONAL LIGHT TO MODERATE SNOW. RADAR REALLY BLOSSOMING OVER SRN/ERN IA TO OUR SOUTH IN THE LAST HOUR AS DEFORMATION ZONE REALLY TAKES SHAPE AND SFC CYCLONE STARTING TO DEEPEN QUICKLY OFF TO THE SOUTH. SHOULD SEE SNOWFALL RATES INCREASE IN THE FAR SOUTH THROUGH THE AFTERNOON...PEAKING MID AFTERNOON...THEN TAILING OFF INTO THE EVENING. COULD SEE LOCAL 3 INCH AMOUNTS IN FAR SOUTH...WHICH IS INCLUDED IN LATEST PRODUCTS. WILL WATCH BACK EDGE OF SNOW AND ADJUST FORECAST AS NEEDED. BINAU && .PREV DISCUSSION... /ISSUED 251 AM CST SAT DEC 15 2007/ SHORT TERM...THROUGH MONDAY MAIN FORECAST CONCERN IS WITH THE SNOW CHANCES TODAY AND TONIGHT. SURFACE ANALYSIS EARLY THIS MORNING SHOWS HIGH PRESSURE CENTERED OVER MINNESOTA AND WISCONSIN. A TROUGH OF LOW PRESSURE EXTENDED FROM ARKANSAS INTO THE OHIO RIVER VALLEY. OBSERVATIONS AND REGIONAL RADARS INDICATE LIGHT SNOW FALLING NORTH OF THE TROUGH FROM KANSAS AND NEBRASKA INTO EASTERN IOWA. MODELS IN FAIRLY GOOD AGREEMENT THIS MORNING IN TAKING THE LONG WAVE TROUGH IN THE LEE OF THE ROCKIES EAST ACROSS THE MIDWEST TODAY AND TONIGHT. A STRONG SHORT WAVE TROUGH EMBEDDED IN THE LONG WAVE TROUGH WILL MOVE OUT OF OKLAHOMA TODAY ACROSS MISSOURI AND HELP TO FORM A CLOSED LOW OVER ILLINOIS OR INDIANA LATE TONIGHT. THE BEST PV ADVECTION WILL PASS WELL SOUTH OF THE FORECAST AREA...BUT THE SHORT WAVE TROUGH WILL BE CLOSE ENOUGH FOR 8 TO 12 PVU/S OF VORTICITY ADVECTION IN THE 500-300 MB LAYER TO PASS OVER THE SOUTHERN SECTIONS OF THE FORECAST AREA. MODERATE TO STRONG QG CONVERGENCE WILL OCCUR WITH THE SHORT WAVE TROUGH TODAY ABOVE 500 MB. AT THE SAME TIME...WEAK FRONTOGENESIS IS EXPECTED IN THE 700 TO 500 MB LAYER. THE SURFACE RIDGE AXIS IS NOT EXPECTED TO MOVE MUCH TODAY WHICH WILL HELP TO MAINTAIN A DRY NORTHEAST FLOW INTO THE AREA. LOOKING AT TIME/HEIGHT PLOTS FROM THE GFS...IT LOOKS AS IF THE DRY AIR WILL HAVE A BIG IMPACT ON HOW FAR NORTH AND PRECIPITATION WILL MAKE INTO THE AREA WITH SATURATION LIKELY OCCURRING OVER THE FAR SOUTH AND QUICKLY BECOMING SOME WHAT DOUBTFUL FROM THE KCCY AREA OVER TOWARD CENTRAL WISCONSIN. PLAN TO HAVE A SHARP GRADIENT WITH THE POPS FROM LIKELY IN THE SOUTH QUICKLY DROPPING OFF TO 20S FROM NEW HAMPTON IOWA INTO CENTRAL ADAMS AND JUNEAU COUNTIES. BEING ON THE NORTH EDGE OF THE SYSTEM NOT EXPECTING MUCH IN THE WAY OF QPF AND WITH COBB DATA SHOWING SNOW RATIOS AROUND 16 TO 1...WHICH LEADS TO ABOUT AN INCH OF ACCUMULATION ACROSS SOUTHERN CLAYTON AND GRANT COUNTIES. WITH THE UPPER LEVEL LOW CLOSING OFF TONIGHT...SYSTEM WILL BE SLOW MOVING AND HAVE ADDED IN SOME CHANCE POPS FOR THIS EVENING AS DOUBTFUL THE SNOW WILL BE PUSH EAST OF THE AREA VERY FAST. FLOW BECOMES ZONAL BEHIND THIS SYSTEM ALLOWING ANOTHER SHORT WAVE TROUGH TO CROSS THE UPPER MIDWEST SUNDAY NIGHT. OTHER THAN SOME WEAK FRONTOGENESIS IN THE 700 TO 500 MB LAYER...NOT MUCH FORCING OCCURS WITH THIS WAVE. CONDENSATION PRESSURE DEFICITS ON THE 280K ISENTROPIC SURFACE REMAIN AT 30 MB OR HIGHER SO DOUBTFUL THAT SATURATION WILL OCCUR AND WILL KEEP THE FORECAST DRY FOR SUNDAY NIGHT AND MONDAY. LONG TERM...MONDAY NIGHT THROUGH FRIDAY THE ZONAL FLOW WILL CONTINUE INTO THE EXTENDED PERIOD. THE NEXT SHORT WAVE TROUGH WILL COME ACROSS MONDAY NIGHT INTO TUESDAY. SOME MODERATE QG CONVERGENCE IS SHOWN BY THE GFS IN THE 850-500 MB LAYER BUT NO FRONTOGENESIS AND AGAIN CONDENSATION PRESSURE DEFICITS ON THE 280K SURFACE REMAIN AT 30 MB OR HIGHER SO WILL MAINTAIN THE DRY FORECAST. BOTH THE GFS AND ECMWF REMAIN CONSISTENT IN BRINGING A SYSTEM OUT OF THE MISSISSIPPI RIVER VALLEY TOWARD THE GREAT LAKES FOR WEDNESDAY NIGHT AND THURSDAY. THE GFS TRACK IS A LITTLE FARTHER NORTH THAN THE ECMWF SO FOR NOW WILL MAINTAIN THE CHANCE POPS. THIS SYSTEM HAS THE POTENTIAL FOR SOME ACCUMULATING SNOWS HEADING INTO THE HOLIDAY WEEKEND. AVIATION... A LOW PRESSURE SYSTEM WILL TRACK OUT OF TX TO ACROSS THE OH RIVER VALLEY TONIGHT. CLOUDS WILL SPREAD NORTH FROM THE LOW ACROSS THE LOCAL AREA...MOSTLY IN THE 4-8 KFT RANGE. AREAS OF SNOW WILL ALSO SPREAD NORTH...BUT SHOULD STAY SOUTH OF KRST/KLSE. IF ANYTHING...PERIODS OF FLURRIES WOULD BE POSSIBLE. WINDS WILL STAY LIGHT...SHIFTING FROM THE NORTHEAST TO NORTHWEST TONIGHT. HIGH PRESSURE WILL BUILD IN FOR SUNDAY...LEADING TO SOME CLEARING SKIES. ARX WATCHES/WARNINGS/ADVISORIES... WI...NONE. MN...NONE. IA...NONE. $$ SHORT/LONG TERM...04 && .ARX WATCHES/WARNINGS/ADVISORIES... WI...NONE. MN...NONE. IA...NONE. && $$ wi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MARQUETTE MI 450 AM EST MON DEC 17 2007 .DISCUSSION... MAIN FCST CONCERNS ARE LIGHT SNOW CHANCES TODAY THROUGH WED ALONG WITH FZDZ POTENTIAL TUE INTO EARLY WED. WV IMAGERY AND RUC ANALYSIS INDICATED A MID/UPPER LEVEL TROUGH ALONG THE WEST COAST...A RIDGE OVER THE ROCKIES...AND A BROAD TROUGH OVER THE EAST HALF OF THE CONUS. A COMPACT SHORTWAVE/VORT WAS LOCATED OVER SRN MANITOBA WITH A DOWNSTREAM SHORTWAVE RIDGE INTO THE WRN GREAT LAKES. AT THE SFC...LOW PRES WAS LOCATED SE MANITOBA WITH A RIDGE FROM WRN ONTARIO INTO WI WHILE THE EAST COAST STORM (971 MB LOW) WAS LIFTING THROUGH THE CANADIAN MARITIMES. TROUGHING ALSO EXTENDED THROUGH THE UPPER GREAT LAKES LEAVING NW FLOW THROUGH ERN LAKE SUPERIOR AND WEAK SW WINDS OVER THE WEST PORTION OF THE LAKE. 850 MB TEMPS TO AROUND -10C SUPPORTED WEAK MULTIPLE WIND PARALLEL LES BANDS ALIGNED WITH 310-320 CBL FLOW INTO THE ERN CWA THAT CONTINUED TO SLOWLY DIMINISH. UPSTREAM 2-4SM VSBY WITH LIGHT SNOW WAS REPORTED OVER SRN MANITOBA INTO WRN ONTARIO...MAINLY ALONG THE MID LEVEL VORT TRACK. TODAY AND TONIGHT...THE LES OVER THE NE PORTION OF THE CWA WILL END AS WINDS BACK WSW BY MID TO LATE MORNING AHEAD OF THE APPROACHING LOW. ADDITIONAL SNOWFALL SHOULD AMOUNT TO LESS THAN AN INCH. THE BEST CHANCE FOR SNOW WITH THE MANITOBA SHORTWAVE WILL BE ALONG THE PATH OF THE MID LEVEL VORT WITH THE AREA OF MODERATE MID/UPPER LEVEL QVECTOR CONV AND STEEPER MID LEVEL LAPSE RATES. THIS WILL KEEP MOST OF THE SNOW NORTH FROM LATE MORNING INTO THE EVENING NORTH OF UPPER MI. ONLY CHANCE POPS INCLUDED VCNTY KCMX/KP59/KERY WITH SLIGHT CHANCE TO THE SOUTH AND NO PCPN MENTIONED CLOSER TO THE WI BORDER. TUESDAY AND TUESDAY NIGHT...MODELS HAVE COME INTO BETTER AGREEMENT WITH THE POSITION/STRENGTH OF THE PAC NW TROUGH AS IT MOVES INTO THE REGION. HOWEVER...GIVEN THE WELL-DEFINED LOOK OF THIS FEATURE FROM THE WV LOOP AND INITIALIZATION PROBLEMS WITH THE 00Z NAM/GFS NOTED BY HPC...THE SLIGHTLY STRONGER/DEEPER 00Z CANADIAN REG GEM...SUPPORTED BY THE ECMWF...WAS PREFERRED. AN INFLUX OF LOW LEVEL MOISTURE WITH RELATIVELY DRY AIR AOB -10C MAY ALSO RESULT IN SOME PATCHY FZDZ ALONG WITH SOME LIGHT SNOW BY MID TO LATE AFTERNOON. AGAIN THE MID LEVEL LOW TRACK WILL BRING BEST SNOW CHANCES MAINLY NORTH OF UPPER MI WITH THE POPS TAPERED FROM NORTH TO SOUTH. EXPECT DEEP MOISTURE AOA -10C OVER ALL BUT THE SOUTH BY TUE NIGHT...REDUCING CHANCES FOR FZDZ. WEDNESDAY...WITH FCST SOUNDINGS SHOWING MOISTURE RECEDING TO AROUND -8C...NRLY FLOW IN THE WAKE OF THE LOW COMBINED WITH ABUNDANT LEFTOVER LOW LEVEL MOISTURE MAY RESULT IN SOME PATCHY LIGHT SNOW OR FREEZING DRIZZLE OVER THE WEST HALF OF UPPER MI IN THE MORNING...ESPECIALLY WHERE WINDS UPSLOPE INTO HIGHER TERRAIN. && .AVIATION (FOR THE 06Z TAF ISSUANCE)... EXPECT MVFR CIGS TO LINGER ALL NGT AT CMX WITH BACKING LLVL FLOW FM NW TO SW ADVECTING LO CLD TO THE SW INTO THE CWA. EXPECT A PD OF VFR CONDITIONS AT SAW BEFORE SOME OF THIS LO CLD ARRIVES TOWARD SUNRISE. WENT MORE PESSIMISTIC AT BOTH SAW/CMX FOR TMRW WITH LARGE MASS OF LO CLD OVER WI PRESSING NEWD. OTRW...FCST TRACK OF INCOMING LO PRES NOW OVER SCNTRL CAN ACRS NRN LK SUP ON MON WITH ABSENCE OF SGNFT MSTR IN THE NRN PLAINS SUGS ANY PCPN ON MON WL BE ON THE LGT SIDE... ESPECIALLY AT SAW. BUT EXPECTED VEERING LLVL FLOW TO MORE W AT CMX IN THE AFTN WL CAUSE LOWER CIG/VSBY/BETTER CHC OF PCPN THAN AT SAW. LLVL DOWNSLOPE WLY FLOW WL CAUSE SOME CLRG IN THE WAKE OF SHRTWV MON EVNG AT SAW. && .MARINE (FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)... HIGH PRESSURE OF 30.1 INCHES OVER CENTRAL AND EASTERN LAKE SUPERIOR WILL GIVE WAY TO A 29.9 INCH LOW PRESSURE SYSTEM FROM CENTRAL MANITOBA LATE THIS AFTERNOON. THIS LOW WILL EXIT TO THE EAST AND WEAKEN SIGNIFICANTLY. IT WILL BE REPLACED BY A SLIGHTLY STRONGER LOW OF 29.8 INCHES FROM CENTRAL MINNESOTA TUESDAY AFTERNOON... CROSSING UPPER MICHIGAN TUESDAY NIGHT...AND MAKING IT TO THE EASTERN GREAT LAKES BY WEDNESDAY EVENING. WINDS ARE EXPECTED TO REMAIN BELOW 30 KNOTS WITH THESE TWO SYSTEMS...AND PROBABLY EVEN AT OR BELOW 25 KNOTS. HIGH PRESSURE OF 30.0 INCHES WILL THEN OVERTAKE THE AREA. A 29.7 INCH LOW PRESSURE SYSTEM DEVELOPING OVER THE SOUTHERN PLAINS THURSDAY MORNING WILL MOVE OVER THE OHIO RIVER VALLEY ON FRIDAY. ALSO ON FRIDAY...ANOTHER LOW PRESSURE SYSTEM OF 29.6 INCHES WILL BE SLIDING OUR WAY FROM NORTH DAKOTA AND SOUTHERN MANITOBA. WINDS LESS THAN 25 KNOTS ARE EXPECTED THURSDAY AND FRIDAY. LOOKING MORE INTO THE FUTURE...IT LOOKS LIKE THE FIRST CHANCE OF GALES ON LAKE SUPERIOR WILL BE SATURDAY NIGHT AND SUNDAY...DEPENDING ON THE TRACK AND STRENGTH OF THE NEXT SIGNIFICANT SURFACE LOW. && .MQT WATCHES/WARNINGS/ADVISORIES...NONE. && $$ DISCUSSION...JLB AVIATION...KC MARINE...KF mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 445 AM EST MON DEC 17 2007 .SYNOPSIS... A GALE CENTER MOVING THROUGH NORTHERN MAINE WILL CONTINUE TO PULL AWAY FROM THE REGION TODAY...ALLOWING HIGH PRESSURE TO BUILD IN FROM THE GREAT LAKES. A SERIES OF WEAK DISTURBANCES WILL APPROACH THE STATE FROM MID TO LATE WEEK WITH THE CHANCE FOR SOME LIGHT PRECIPITATION. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... LATEST RADAR IMAGERY CONTINUES TO SHOW AN IMPRESSIVE LAKE EFFECT BAND WITH LK HURON CONNECTION OVR THE SOUTH CENTRAL MTNS FROM SWRN CLEARFIELD CTY INTO SRN CENTRE. LINES UP NICELY UNDER A BAND OF LOW LEVEL CONFLUENT FLOW THAT THE RUC13 ANALYSIS. THIS SLOWLY LOSES IT`S CYCLONIC FEED OFF HURON AND BECOMES MORE WESTERLY OVER THE NEXT 3-6 HOURS. DECIDED TO KEEP THE SNOW ADVISORIES FOR THE LAURELS AND NW COUNTIES THRU 12Z...THINKING IS THAT THE SNOW MIGHT STILL BE ONGOING BUT PROGGED SOUNDINGS AND RUC13 LOW LEVEL WINDS INDICATE THE EVENT WINDING DOWN. GUSTY WINDS IN THE WAKE OF THE STORM WILL GRADUALLY RELAX TODAY AS THE HIGH BUILDS IN. WIND ADV EXPIRES AT MID DAY AND THAT TIMING ALSO LOOKS REASONABLE. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/... OTHER THAN THE USUAL LINGERING CLOUDS AND SNOW FLURRIES/SHOWERS OVER THE NW AND LAURELS...THE OVERNIGHT AND TUESDAY WILL BE RELATIVELY TRANQUIL AND FAIR FOR A CHANGE. CLOUDS WILL LIKELY INCREASE DURING THE DAY AS THE NEXT SYSTEM STARTS TO SPREAD MOISTURE OUR WAY...BUT PRECIP SHUD HOLD OFF UNTIL TUES NITE/WED. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... FLOW ALOFT GOES QUASI-ZONAL FROM MID-LATE WEEK WITH A SERIES OF WEAK DISTURBANCES BEING MARCHED OUR WAY BY THE MODELS. THE FIRST BRINGS SOME LIGHT RAIN OR SNOW WEDNESDAY. SECOND IN THE SERIES IS TAKEN MAINLY SOUTH OF HERE THURS WITH THE FLOW EVENTUALLY AMPLIFYING FOR THE WEEKEND. THE PERIOD FROM WED ONWARD HAS SOME SORT OF LIGHT PRECIP MENTIONED JUST ABOUT EVERY DAY...BUT THE NEXT BEST CHANCE FOR SIGNIFICANT PRECIP LOOKS LIKE THE WEEKEND AT THE EARLIEST. && .AVIATION /09Z MONDAY THROUGH FRIDAY/... AN INTENSE STORM OFF THE COAST HAS RESULTED IN A VERY STRONG NW FLOW OF COLD AIR ACROSS THE LAKES. VAD WINDS ARE FROM ABOUT 290 AT 50 KNOTS AT 4000 FEET. ONE OF THE WORST BANDS OF LAKE EFFECT SQUALLS I HAVE SEEN ON RADAR IN A LONG TIME EXTENDS OFF LAKE HURON...SE ACROSS MUCH OF C PA. ONE CAN SEE THAT THIS BAND EXTENDS OFF THE NJ COAST. IFR/LIFR CONDITIONS LIKELY IN THIS BAND. OTHERWISE...MAINLY MVFR CONDITIONS AT TIMES AT MOST SITES OVERNIGHT BUT IPT AND MDT...WHERE VFR CONDITIONS SHOULD HOLD. PLACES LIKE BFD AND JST WILL ALSO BE IFR AT TIMES. CONDITIONS SHOULD IMPROVE BY AFT...AS HEIGHTS RISE... AND INVERSION HEIGHTS LOWER...AND THE STRONG CYCLONIC FLOW WEAKENS. CONDITIONS IMPROVE SIGNIFICANTLY IN ALL AREAS BY MONDAY NIGHT. A FEW SNOW SHOWERS POSSIBLE BY TUESDAY NIGHT AND WED...MAINLY ACROSS THE FAR NORTHERN PART OF THE STATE. THEN MORE ADVERSE FLYING WEATHER RETURNS FOR LATE THU NIGHT AND FRIDAY AS A MORE ORGANIZED AREA OF LOW PRESSURE MOVES NORTHEAST ACROSS THE OHIO RIVER VALLEY AND BRINGS RAIN OR SNOW TO THE SOUTHEAST HALF OF THE STATE...WITH SNOW LIKELY ACROSS THE NORTHERN PART OF PENNSYLVANIA. && .CTP WATCHES/WARNINGS/ADVISORIES... WIND ADVISORY UNTIL 1 PM EST THIS AFTERNOON FOR PAZ004>006- 010>012-017>019-024>028-033>037-041-042-045-046-049>053- 056>059-063>066. SNOW AND BLOWING SNOW ADVISORY UNTIL 7 AM EST THIS MORNING FOR PAZ024-033. LAKE EFFECT SNOW AND BLOWING SNOW ADVISORY UNTIL 7 AM EST THIS MORNING FOR PAZ004-005. && $$ SYNOPSIS...LACORTE NEAR TERM...LACORTE SHORT TERM...LACORTE LONG TERM...LACORTE AVIATION...MARTIN/RXR pa AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SPOKANE WA 1030 PM PST SUN DEC 16 2007 .SYNOPSIS... THE NEXT IN A SEEMINGLY ENDLESS SERIES OF WEATHER SYSTEMS WILL MOVE INTO THE INLAND NORTHWEST TONIGHT AND EXIT THE REGION BY MONDAY AFTERNOON. THIS WEATHER DISTURBANCE WILL RESULT IN WIDESPREAD SNOW ACROSS THE REGION. ANOTHER WEATHER SYSTEM WILL MOVE INTO THE REGION QUICKLY ON TUESDAY FOR ANOTHER ROUND OF UNSETTLED WEATHER. && .DISCUSSION... AS OF 06Z...THE ELONGATED UPPER TROUGH HAS MOVED ONSHORE OVER THE WASHINGTON AND OREGON COAST. THERE IS A DISTINCT CIRCULATION ACCOMPANYING THE TROUGH OVER SOUTHWESTERN OREGON. COLD CUMULUS DEVELOPMENT ON INFRARED IMAGERY MOVING ONSHORE IS AN INDICATION OF THE INSTABILITY ASSOCIATED WITH THE HEART OF THE TROUGH AXIS. THE RUC ANALYZES A POCKET OF -30C AT 500MB THAT WILL PIVOT THROUGH CENTRAL AND EASTERN WASHINGTON BETWEEN 15Z AND 21Z. PRECIPITATION HAS DEVELOPED RAPIDLY OVER CENTRAL WASHINGTON BETWEEN 04-06Z IN RESPONSE TO STRONG Q-VECTOR CONVERGENCE. THIS INITIAL SHOT OF SYNOPTICALLY INDUCED PRECIPITATION WILL TRANSLATE NORTHEAST AND SHIFT INTO NORTHWEST MONTANA BETWEEN 12Z AND 15Z. EXPECT AN INCH OR TWO OF SNOW ACCUMULATION FROM OMAK THROUGH THE NORTHERN MOUNTAINS AND INTO THE SPOKANE/COUER D`ALENE AREAS BY SUNRISE WITH THIS SNOW-BAND. POST FRONTAL OROGRAPHIC SNOW SHOWERS WILL ADD TO THE SNOW ACCUMULATION OVER THE MOUNTAINS OF IDAHO AND FAR NORTHEAST WASHINGTON THROUGH TOMORROW AFTERNOON. THE COLD AIR AT 500MB WILL CONTRIBUTE TO A DEEP LAYER OF CONDITIONAL INSTABILITY WITH THE MOUNTAINS FAVORED FOR THE MOST SIGNIFICANT ACCUMULATIONS ON MONDAY. FOR THE MORNING COMMUTE...IT LOOKS LIKE THE MOST SIGNIFICANT SNOW WILL BE WINDING DOWN IN THE SPOKANE AND COEUR D`ALENE AREAS AS THE BEST DIFFERENTIAL VORTICITY ADVECTION WILL BE EAST OF THE REGION. THERE MAY BE SOME CONVECTIVE SNOW BURSTS AROUND SUNRISE AS THE HEART OF THE COLD UPPER TROUGH MOVES INTO FAR EASTERN WASHINGTON. OF THE SNOW ADVISORIES CURRENTLY IN EFFECT...THE ACCUMULATIONS FOR THE OMAK AREA ARE THE MOST QUESTIONABLE AT THIS POINT. WINDS AT 700MB WILL LIKELY BECOME UNFAVORABLE FOR ACCUMULATING SNOW BY 09Z AS THE TROUGH AXIS CRESTS THE CASCADES. THE SNOW ADVISORIES FOR THE OKANOGAN HIGHLANDS AND THE OKANONGAN VALLEY HAVE A GOOD CHANCE OF BEING CANCELLED EARLY GIVEN THE LATEST RADAR AND SATELLITE TRENDS. /GKOCH && .AVIATION... SNOW WILL REDUCE VISIBILITIES AND CEILINGS TO 1500 FEET OR LESS IN THE SPOKANE...COUER D`ALENE...AND PULLMAN AREAS FROM 08Z TO AT LEAST 15Z. POST FRONTAL MIXING SHOULD BRING IMPROVING CONDITIONS TO EASTERN WASHINGTON AND ADJACENT PORTIONS OF IDAHO AFTER 18Z. THERE SHOULD BE SUFFICIENT DOWNSLOPING OFF THE CASCADES TO BRING AN END TO THE SNOW IN THE WENATCHEE AND MOSES LAKE AREAS BETWEEN 08-10Z...BUT THE MIXING MAY NOT BE VIGOROUS ENOUGH TO MIX OUT STRATUS UNTIL 16-18Z. /GKOCH && .PRELIMINARY POINT TEMPS/POPS... SPOKANE 28 32 25 35 29 34 / 80 60 40 90 60 60 COEUR D`ALENE 28 34 24 36 30 34 / 80 70 30 100 60 60 PULLMAN 30 33 28 39 31 37 / 40 40 40 80 50 50 LEWISTON 33 41 32 44 35 42 / 20 30 20 50 30 40 COLVILLE 26 34 23 35 28 34 / 90 70 20 100 50 70 SANDPOINT 29 34 22 35 30 33 / 80 70 40 100 80 60 KELLOGG 26 32 22 35 30 36 / 80 80 30 100 80 60 MOSES LAKE 27 33 27 37 29 36 / 50 20 60 90 10 60 WENATCHEE 27 32 27 33 28 31 / 40 20 60 90 10 70 OMAK 18 32 25 31 26 31 / 60 20 50 100 10 70 && .OTX WATCHES/WARNINGS/ADVISORIES... ID...SNOW ADVISORY UNTIL 4 PM PST MONDAY FOR CENTRAL PANHANDLE MOUNTAINS. SNOW ADVISORY UNTIL 4 PM PST MONDAY FOR NORTHERN PANHANDLE. WA...SNOW ADVISORY UNTIL 4 PM PST MONDAY FOR NORTHEAST MOUNTAINS. SNOW ADVISORY UNTIL 10 AM PST MONDAY FOR OKANOGAN HIGHLANDS. SNOW ADVISORY UNTIL 10 AM PST MONDAY FOR OKANOGAN VALLEY. && $$ wa AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE DES MOINES IA 935 AM CST MON DEC 17 2007 .SHORT TERM /TODAY/... FORECAST SOUNDINGS CONTINUE TO SHOW A STRONG LOW LEVEL INVERSION WITH WARMER AIR SHOOTING OVER THE COLD...SNOWPACK ENHANCED SURFACE AIR. RUC/NAM/GFS SOUNDINGS ALL KEEP SFC TEMPS BELOW FREEZING TODAY...SO HAVE UPDATED THE FORECAST TO HEDGE A LITTLE LOWER ON MAX TEMP TODAY. ALSO CLEARED OUT THE FOG/STRATUS AND EXPECT US TO HAVE A FULL DAY OF SUNSHINE WITH MAYBE SOME CIRRUS SPREADING IN FROM THE WEST DURING THE AFTERNOON. .PREVIOUS DISCUSSION... THE STRATUS AND FOG OVER THE CWA IS FINALLY CLEARING OUT AND TEMPS ARE BEGINNING TO FALL. AS SURFACE HIGH PRESSURE PUSHES ACROSS THE SOUTHERN PLAINS EASTWARD...THE FLOW WILL PREDOMINANTLY BECOME SOUTHWESTERLY THEN SOUTHERLY. WITH THE CURRENT SNOW PACK I FEEL THAT GUIDANCE IS TOO WARM...AS IT HAS BEEN OVER THE LAST SEVERAL DAYS. THEREFORE...DESPITE BETTER SUNSHINE TODAY I KNOCKED TEMPS BACK HALF A CATEGORY OR SO. SOUTHERLY WINDS INCREASE SOME MONDAY NIGHT THROUGH TUESDAY. THIS COMBINED WITH A MORE ZONAL FLOW ALOFT SHOULD ALLOW FOR BETTER WARMING BY MID WEEK. A WEAK AND FAST MOVING DISTURBANCE SHOULD KEEP SOME CLOUD COVER OVER THE STATE FOR TUESDAY AND SMALL CHANCE POPS OVER THE NORTHERN QUARTER OF THE CWA. WEAK RIDGING THEN BUILDS BACK OVER CENTRAL IOWA TUESDAY NIGHT AND WEDNESDAY BEFORE A MORE SIGNIFICANT SHORT WAVE MOVES IN WEDNESDAY NIGHT AND THURSDAY. MODELS CONTINUE TO DIFFER ON THIS BUT THEY SEEM TO HINT AT SPLITTING THE ENERGY IN THIS SHORTWAVE KEEPING THE BETTER PRECIP SOUTH OF THE STATE AND ONLY DRIBBLE SOME LIGHT QPF OVER US. OUT OF THE DAY 5 PERIOD...THE NEXT STORM TO AFFECT IOWA WILL BE FRIDAY NIGHT/SATURDAY BUT TODAYS EUROPEAN WAS LOOKING LIKE YESTERDAYS GFS WITH LITTLE CHANGE IN THAT FROM YESTERDAY. ONE BIG DIFFERENCE IS THAT THE GFS IS NOW KEEPING THE SHORTWAVE OPEN AND NOT PRODUCING A CLOSED LOW WITH THIS AND THE OTHER NOTEWORTHY ITEM IS THAT THE SURFACE LOW DOES NOT INTENSIFY UNTIL IT GETS EAST OF US. STILL LOTS OF VARIABLES BUT WE SHOULD SEE SOMETHING FOR SATURDAY. AS FOR TEMPS...STILL KEPT THEM BELOW GUIDANCE AS IT HAS NOT BEEN DOING WELL WITH TEMPS IN THE SNOW PACK. && .AVIATION...17/12Z FOG RECEDING OVR ERN IA AND SHOULD GIVE WAY TO VFR CONDS OVR ALL RTES BY MID MRNG. NO WX THIS TAF PD WITH SW-SLY WIND FLOW INTO TONIGHT. OTHER THAN A CI LAYER MOVING IN AFT SNST TNGT, NO WX TO SPEAK OF. && .DMX WATCHES/WARNINGS/ADVISORIES...NONE. && $$ SHORT TERM...MOYER LONG TERM...FAB AVIATION...MS DEC 07 ia AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE MARQUETTE MI 1102 AM EST MON DEC 17 2007 .UPDATE... VERY TRICKY FORECAST FOR THE REST OF TODAY INTO TONIGHT. WATER VAPOR IMAGERY SHOWS AN UPPER LOW MOVING INTO NW ONTARIO...WHICH MODELS PROG TO NOW MOVE EVEN FARTHER NORTH...ACROSS VERY FAR NORTHERN LAKE SUPERIOR OR IN ONTARIO. U.S. AND CANADIAN RADARS DEPICT ALL OF THE PCPN ASSOCIATED WITH THE UPPER LOW NORTH OF THE MN/ONTARIO BORDER...LIKELY DUE TO DRY AIR IN THE MID-LEVELS DEPICTED ON THE 12Z INL AND GRB SOUNDINGS. THIS UPPER LOW IS REFLECTED AT THE SURFACE BY A 1009MB LOW NEAR THE INTERSECTION OF MANITOBA/ONTARIO AND MN...WITH A WARM FRONT EXTENDING SE THROUGH THE KEWEENAW AND INTO THE EASTERN U.P.. SOUTH OF THIS WARM FRONT...LOW CLOUDS...MIST AND LIGHT SNOW HAVE BEEN ADVECTING NORTHEASTWARD INTO THE CWA FROM WI ON SW WINDS. HOWEVER...THE CLOUDS HAVE BEEN SLOW TO MOVE INTO DOWNSLOPE AREAS... SUCH AS ONTONAGON...BARAGA AND MARQUETTE...WHICH COMBINED WITH THE 12Z GRB SOUNDING SHOW THE SHALLOW NATURE OF THE CLOUDS. THE RUC MODELS HAVE HAD A PRETTY GOOD HANDLE ON THESE LOW CLOUDS ON THEIR 950MB RH FIELD...AND UPDATED THE CLOUD FORECAST FOR TODAY INTO TONIGHT BASED ON THIS FIELD. BASICALLY...THE LOW CLOUDS SHOULD ENCOMPASS MUCH OF THE U.P. BY 00Z TONIGHT...WITH DOWNSLOPE AREAS TAKING THE LONGEST TO SEE THE CLOUDS. IN ADDITION...ADDED SOME FLURRIES SINCE SITES SUCH AS LNL...IMT AND EGV HAVE REPORTED THEM...WHICH MAKES SENSE GIVEN THAT THE LOW CLOUD DECK IS WITHIN THE -10 TO -12C ZONE. DEBATED ABOUT ADDING SOME PATCHY FOG TOO...BUT WITH VISIBILITIES GENERALLY ABOVE 2 SM...FIGURE THINGS WILL BE OKAY. REGARDING SYNOPTIC PCPN CHANCES WITH THE UPPER LOW...HAVE SHIFTED THESE NORTH OF UPPER MI TODAY GIVEN THE FARTHER NORTH TRACK. HOWEVER...AS THE COLD FRONT ASSOCIATED WITH THE SURFACE LOW MOVES IN TONIGHT...IT COULD END UP PICKING UP SOME LAKE MOISTURE AND GENERATING LAKE ENHANCED CLOUDS...SINCE LAPSE RATES FROM THE LAKE SURFACE TO 900MB ARE PROGGED TO BECOME MORE THAN MOIST ADIABATIC. THIS PCPN WOULD MOVE INTO THE KEWEENAW THIS EVENING AND REMAIN NEARLY STATIONARY THROUGH THE NIGHT. PCPN TYPE IS OF CONCERN AS THE TOP OF THE INVERSION MAY ONLY REACH -8C AT BEST. THUS...HAVE DECIDED TO INCLUDE A MENTION OF FZDZ FOR THE KEWEENAW TOO. && .DISCUSSION... MAIN FCST CONCERNS ARE LIGHT SNOW CHANCES TODAY THROUGH WED ALONG WITH FZDZ POTENTIAL TUE INTO EARLY WED. WV IMAGERY AND RUC ANALYSIS INDICATED A MID/UPPER LEVEL TROUGH ALONG THE WEST COAST...A RIDGE OVER THE ROCKIES...AND A BROAD TROUGH OVER THE EAST HALF OF THE CONUS. A COMPACT SHORTWAVE/VORT WAS LOCATED OVER SRN MANITOBA WITH A DOWNSTREAM SHORTWAVE RIDGE INTO THE WRN GREAT LAKES. AT THE SFC...LOW PRES WAS LOCATED SE MANITOBA WITH A RIDGE FROM WRN ONTARIO INTO WI WHILE THE EAST COAST STORM (971 MB LOW) WAS LIFTING THROUGH THE CANADIAN MARITIMES. TROUGHING ALSO EXTENDED THROUGH THE UPPER GREAT LAKES LEAVING NW FLOW THROUGH ERN LAKE SUPERIOR AND WEAK SW WINDS OVER THE WEST PORTION OF THE LAKE. 850 MB TEMPS TO AROUND -10C SUPPORTED WEAK MULTIPLE WIND PARALLEL LES BANDS ALIGNED WITH 310-320 CBL FLOW INTO THE ERN CWA THAT CONTINUED TO SLOWLY DIMINISH. UPSTREAM 2-4SM VSBY WITH LIGHT SNOW WAS REPORTED OVER SRN MANITOBA INTO WRN ONTARIO...MAINLY ALONG THE MID LEVEL VORT TRACK. TODAY AND TONIGHT...THE LES OVER THE NE PORTION OF THE CWA WILL END AS WINDS BACK WSW BY MID TO LATE MORNING AHEAD OF THE APPROACHING LOW. ADDITIONAL SNOWFALL SHOULD AMOUNT TO LESS THAN AN INCH. THE BEST CHANCE FOR SNOW WITH THE MANITOBA SHORTWAVE WILL BE ALONG THE PATH OF THE MID LEVEL VORT WITH THE AREA OF MODERATE MID/UPPER LEVEL QVECTOR CONV AND STEEPER MID LEVEL LAPSE RATES. THIS WILL KEEP MOST OF THE SNOW NORTH FROM LATE MORNING INTO THE EVENING NORTH OF UPPER MI. ONLY CHANCE POPS INCLUDED VCNTY KCMX/KP59/KERY WITH SLIGHT CHANCE TO THE SOUTH AND NO PCPN MENTIONED CLOSER TO THE WI BORDER. TUESDAY AND TUESDAY NIGHT...MODELS HAVE COME INTO BETTER AGREEMENT WITH THE POSITION/STRENGTH OF THE PAC NW TROUGH AS IT MOVES INTO THE REGION. HOWEVER...GIVEN THE WELL-DEFINED LOOK OF THIS FEATURE FROM THE WV LOOP AND INITIALIZATION PROBLEMS WITH THE 00Z NAM/GFS NOTED BY HPC...THE SLIGHTLY STRONGER/DEEPER 00Z CANADIAN REG GEM...SUPPORTED BY THE ECMWF...WAS PREFERRED. AN INFLUX OF LOW LEVEL MOISTURE WITH RELATIVELY DRY AIR AOB -10C MAY ALSO RESULT IN SOME PATCHY FZDZ ALONG WITH SOME LIGHT SNOW BY MID TO LATE AFTERNOON. AGAIN THE MID LEVEL LOW TRACK WILL BRING BEST SNOW CHANCES MAINLY NORTH OF UPPER MI WITH THE POPS TAPERED FROM NORTH TO SOUTH. EXPECT DEEP MOISTURE AOA -10C OVER ALL BUT THE SOUTH BY TUE NIGHT...REDUCING CHANCES FOR FZDZ. WEDNESDAY...WITH FCST SOUNDINGS SHOWING MOISTURE RECEDING TO AROUND -8C...NRLY FLOW IN THE WAKE OF THE LOW COMBINED WITH ABUNDANT LEFTOVER LOW LEVEL MOISTURE MAY RESULT IN SOME PATCHY LIGHT SNOW OR FREEZING DRIZZLE OVER THE WEST HALF OF UPPER MI IN THE MORNING...ESPECIALLY WHERE WINDS UPSLOPE INTO HIGHER TERRAIN. && .AVIATION (FOR THE 12Z TAF ISSUANCE)... OCCASIONAL FLURRIES SEEM TO BE AFFECTING THE SAW SITE...ON THE SOUTHERN EDGE OF A BLAND OF CLOUDS THAT STRETCHES NORTHEASTERLY ACROSS LAKE SUPERIOR TO THE ARROWHEAD REGION OF MN. BEST CHANCE OF SNOW WILL REMAIN AT CMX...REMAINING IFR TO LOW MVFR THROUGH THE PERIOD...GIVEN FAVORABLE WINDS AND APPROACHING LOW LEVEL MOISTURE EVIDENT ON THE IR SAT IMG. CONTINUE TO HAVE LOW CLOUDS OVER N WI SLOWLY SLIDING NORTHEASTWARD...PARTICULARLY ACROSS THE WESTERN THIRD OF THE CWA. && .MARINE (FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)... HIGH PRESSURE OF 30.1 INCHES OVER CENTRAL AND EASTERN LAKE SUPERIOR WILL GIVE WAY TO A 29.9 INCH LOW PRESSURE SYSTEM FROM CENTRAL MANITOBA LATE THIS AFTERNOON. THIS LOW WILL EXIT TO THE EAST AND WEAKEN SIGNIFICANTLY. IT WILL BE REPLACED BY A SLIGHTLY STRONGER LOW OF 29.8 INCHES FROM CENTRAL MINNESOTA TUESDAY AFTERNOON... CROSSING UPPER MICHIGAN TUESDAY NIGHT...AND MAKING IT TO THE EASTERN GREAT LAKES BY WEDNESDAY EVENING. WINDS ARE EXPECTED TO REMAIN BELOW 30 KNOTS WITH THESE TWO SYSTEMS...AND PROBABLY EVEN AT OR BELOW 25 KNOTS. HIGH PRESSURE OF 30.0 INCHES WILL THEN OVERTAKE THE AREA. A 29.7 INCH LOW PRESSURE SYSTEM DEVELOPING OVER THE SOUTHERN PLAINS THURSDAY MORNING WILL MOVE OVER THE OHIO RIVER VALLEY ON FRIDAY. ALSO ON FRIDAY...ANOTHER LOW PRESSURE SYSTEM OF 29.6 INCHES WILL BE SLIDING OUR WAY FROM NORTH DAKOTA AND SOUTHERN MANITOBA. WINDS LESS THAN 25 KNOTS ARE EXPECTED THURSDAY AND FRIDAY. LOOKING MORE INTO THE FUTURE...IT LOOKS LIKE THE FIRST CHANCE OF GALES ON LAKE SUPERIOR WILL BE SATURDAY NIGHT AND SUNDAY...DEPENDING ON THE TRACK AND STRENGTH OF THE NEXT SIGNIFICANT SURFACE LOW. && .MQT WATCHES/WARNINGS/ADVISORIES...NONE. && $$ UPDATE...AJ DISCUSSION...JLB AVIATION...KF MARINE...KF mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GAYLORD MI 1030 AM EST MON DEC 17 2007 .UPDATE...RUC/SURFACE/SATELLITE/SURFACE ANALYSIS THIS MORNING REVEALS SHORTWAVE RIDGING WORKING ACROSS THE WESTERN GREAT LAKES REGION. WITH THE RIDGE AXIS SLIDING THROUGH THE AREA...SFC WINDS HAVE BEEN BACKING AROUND TO THE WEST THIS MORNING...EVENTUALLY ENDING UP AT SOUTHWEST LATER THIS AFTERNOON. WARM FRONT IS NOT VERY EVIDENT WITH REGARDS TO SURFACE TEMPERATURES. HOWEVER...LOOKING AT WINDS AND LOW CLOUD DEVELOPMENT...APPEARS THE MAIN WARM FRONT BOUNDARY IS LOCATED FROM CENTRAL UPPER MICHIGAN...SOUTHWARD THROUGH THE LONG AXIS OF LAKE MICHIGAN AND INTO SOUTHEAST LOWER MICHIGAN. CEILINGS AROUND KFKS AND KMBL ARE BEGINNING TO FALL TO AROUND 2KFT SUGGESTING THE FRONT IS STARTING TO PUSH ONSHORE INTO NORTHERN LOWER MICHIGAN. ALSO EVIDENT IS THE DWINDLING OVER LAKE INSTABILITY. RADAR REFLECTIVITIES HAVE SHOWN A DECREASING TREND OVER THE PAST FEW HOURS. LATEST 850MB RUC TEMPERATURE ANALYSIS REVEALS -4C 850MB AIR IMMEDIATELY BEHIND THE SURFACE WARM FRONT IN EASTERN WISCONSIN. WITH LAKE MICHIGAN TEMPERATURES CURRENTLY RUNNING AROUND +7C...DELTA TS WILL FALL TO LESS THAN THE IDEAL 13C BY EARLY THIS AFTERNOON AS THE WARMER AIR UPSTREAM ADVECTS INTO THE AREA. THUS...THE ONGOING DIMINISHING TREND TO THE LAKE EFFECT SNOW SHOWERS WILL CONTINUE THROUGH THE REMAINDER OF THE MORNING AND EARLY AFTERNOON. THERE IS STILL PLENTY OF LOW LEVEL MOISTURE TRAPPED BELOW A 900MB INVERSION AS SHOWN BY LOW CLOUD COVERAGE ACROSS WISCONSIN. THUS...WOULD EXPECT THIS LOW CLOUD COVERAGE TO EXPAND EAST AND NORTH TODAY...OVERTAKING MOST OF NORTHERN MICHIGAN BY LATE THIS AFTERNOON. THE MOISTURE WILL REMAIN SHALLOW ENOUGH TO PREVENT ANY DRIZZLE OR FLURRIES FROM DEVELOPING THIS AFTERNOON. NO CHANGES PLANNED TO SFC TEMPERATURES...AS INCREASING CLOUDS WILL HELP KEEP TEMPERATURES FROM GETTING OUT OF THE UPPER 20S THIS AFTERNOON. THE EXCEPTION WILL BE ALONG THE LAKE MICHIGAN SHORELINE...WHERE ONSHORE WINDS WITH THE HELP OF STILL SOMEWHAT WARM LAKE WATERS WILL ALLOW LOCATIONS TO CLIMB INTO THE LOWER 30S. KAS && .AVIATION... /ISSUED 642 AM EST MON DEC 17 2007/ PREVAILING VFR CIGS/VSBYS WILL CONTINUE TODAY INTO TONIGHT (BUT JUST ABOVE MVFR). TEMPORARY MVFR CONDITIONS ARE EXPECTED ACROSS PLN AND TVC IN LAKE INDUCED SNOW SHOWERS THIS MORNING. MVFR CIGS ARE POSSIBLE THIS EVENING AT PLN AS A WEAK AREA OF LOW PRESSURE (CLIPPER) MOVES BY. WINDS WILL BE GENERALLY 10 KNOTS OR LESS THROUGH THE TAF PERIOD. AJS && .PREV DISCUSSION... /ISSUED 444 AM EST MON DEC 17 2007/ ON THE LATEST SURFACE WEATHER MAP...973 MB LOW PRESSURE WAS OVER UPSTATE MAINE...1030 MB HIGH PRESSURE OVER EAST TEXAS AND 1008 MB LOW PRESSURE ACROSS SOUTHERN MANITOBA. APX RADAR CONTINUES TO SHOW A BROAD AREA OF NORTHWEST FLOW LAKE EFFECT MOVING OFF OF LAKES SUPERIOR AND MICHIGAN. SURFACE OBSERVATIONS INDICATE THAT THIS ACTIVITY IS ON THE LIGHT TO OCCASIONALLY MODERATE SIDE (LOWEST VSBYS OF 1 1/2 TO 3 MILES). THE MAIN SHORT TERM FORECAST CONCERNS REVOLVE AROUND THE TIMING OF THE ENDING OF LAKE EFFECT TODAY...THEN POPS WITH WARM ADVECTION/CLIPPER SYSTEM LATER TODAY INTO TONIGHT. OTHER CONCERNS INCLUDE POPS THIS EVENING AND POPS AND POTENTIAL FOR FREEZING DRIZZLE TUESDAY AFTERNOON INTO WEDNESDAY. TODAY...DESPITE INCREASING RIDGING/ANTICYCLONIC FLOW ALOFT ALONG WITH DRIER AIR MOVING IN (MODELS LOWER MEAN 900-700 MB RH TO ABOUT 40 PERCENT AT 12Z)...THE LAKE EFFECT MACHINE CONTINUES TO CHURN ON AS IS THE CASE MORE TIMES THAN NOT. THEREFORE WILL LINGER POPS OVER THE NEXT SEVERAL HOURS. AS WARMER TEMPERATURES ADVECT IN ALOFT (850 MB TEMPS INCREASE FROM BETWEEN -10 AND -12 AT 12Z TO -6 AND -9 AT 18Z TO -2 AND -6 AT 00Z)...OVER LAKE INSTABILITY WILL SLOWLY DECREASE WHICH SHOULD END LAKE EFFECT SOMETIME THIS AFTERNOON. SO WILL CONTINUE WITH NUMEROUS SNOW SHOWERS ACROSS FAVORED AREAS THIS MORNING AND EARLY THIS AFTERNOON WITH ACCUMULATIONS OF AN INCH OR TWO. THE FLOW BACKS FROM NORTHWEST EARLY THIS MORNING INTO THE WEST SOUTHWEST THIS AFTERNOON SO WILL ORIENTATE POPS TO ACCOUNT FOR THIS AS WELL. IN ADDITION...WARM ADVECTION/A BIT OF ISENTROPIC ASCENT (I280) IN COMBINATION WITH A WEAK CLIPPER MOVING ACROSS SOUTH CENTRAL CANADA WILL BRING A CHANCE OF LIGHT SNOW TO EASTERN UPPER LATER THIS AFTERNOON. HIGHS TODAY IN THE MIDDLE TO UPPER 20S. TONIGHT...CLIPPER CONTINUES TO MOVE ACROSS FAR SOUTHERN CANADA GRAZING EASTERN UPPER THIS EVENING LEADING TO A CHANCE OF LIGHT SNOW ACROSS FAR NORTHERN ZONES. MODELS INDICATE THAT THERE IS A WEAK AREA OF DIV-Q AND A MARGINAL AMOUNT OF MOISTURE (MEAN 1000-500 MB RH 60 TO 70 PERCENT) ASSOCIATED WITH THIS SYSTEM. OTHERWISE...OVER LAKE INSTABILITY WILL CONTINUE TO WANE AS 850 MB TEMPERATURES SETTLE IN BETWEEN -2 AND -4 C. LOWS IN THE UPPER TEENS TO LOWER 20S. TUESDAY...NOT A LOT GOING ON TO START THE DAY AS A SHORT WAVE RIDGE MOVES ACROSS THE AREA. ANOTHER CLIPPER ALONG WITH AN ASSOCIATED SURFACE WARM FRONT THEN APPROACHES FROM THE NORTHWEST LATE IN THE DAY. THIS WILL LEAD TO A CHANCE FOR LIGHT SNOW OR EVEN SOME FREEZING DRIZZLE (MODEL CROSS SECTIONS/SOUNDINGS SHOW LOW LEVEL MOISTURE ONLY UP TO ABOUT -8C) ACROSS NORTHWESTERN ZONES. MILDER WITH HIGHS IN THE LOWER AND MIDDLE 30S. TUESDAY NIGHT INTO WEDNESDAY...CLIPPER TAKES ITS TIME MOVING ACROSS THE REGION. MOISTURE IS SHOWN TO REMAIN SHALLOW IN THE EVENING LEADING TO A CONTINUED CHANCE OF FREEZING DRIZZLE THEN DEEP ENOUGH AFTER MIDNIGHT INTO WEDNESDAY TO LEAD TO A CHANCE OF LIGHT SNOW. LOWS TUESDAY NIGHT IN THE MIDDLE AND UPPER 20S WITH HIGHS ON WEDNESDAY RANGING FROM AROUND 30 TO THE MIDDLE 30S. THURSDAY...MODELS ARE IN GOOD AGREEMENT THAT AN AREA OF LOW PRESSURE MOVES BY TO OUR SOUTH. WILL ADD IN LOW CHANCE POPS INTO FAR SOUTHERN ZONES TO LINE UP WITH SURROUNDING OFFICES. HIGHS IN THE LOWER AND MIDDLE 30S. NO CHANGES MADE TO THE REMAINDER OF THE FORECAST. POTENTIAL MESS NEXT WEEKEND THOUGH AS THE EXTENDED MODELS BRING A DEEP AREA OF LOW PRESSURE ACROSS THE WESTERN GREAT LAKES (WITH POSSIBLE PRECIPITATION TYPE ISSUES). SULLIVAN && .APX WATCHES/WARNINGS/ADVISORIES...NONE. && $$ mi AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE MARQUETTE MI 610 AM EST MON DEC 17 2007 UPDATED FOR 12Z TAFS .DISCUSSION... MAIN FCST CONCERNS ARE LIGHT SNOW CHANCES TODAY THROUGH WED ALONG WITH FZDZ POTENTIAL TUE INTO EARLY WED. WV IMAGERY AND RUC ANALYSIS INDICATED A MID/UPPER LEVEL TROUGH ALONG THE WEST COAST...A RIDGE OVER THE ROCKIES...AND A BROAD TROUGH OVER THE EAST HALF OF THE CONUS. A COMPACT SHORTWAVE/VORT WAS LOCATED OVER SRN MANITOBA WITH A DOWNSTREAM SHORTWAVE RIDGE INTO THE WRN GREAT LAKES. AT THE SFC...LOW PRES WAS LOCATED SE MANITOBA WITH A RIDGE FROM WRN ONTARIO INTO WI WHILE THE EAST COAST STORM (971 MB LOW) WAS LIFTING THROUGH THE CANADIAN MARITIMES. TROUGHING ALSO EXTENDED THROUGH THE UPPER GREAT LAKES LEAVING NW FLOW THROUGH ERN LAKE SUPERIOR AND WEAK SW WINDS OVER THE WEST PORTION OF THE LAKE. 850 MB TEMPS TO AROUND -10C SUPPORTED WEAK MULTIPLE WIND PARALLEL LES BANDS ALIGNED WITH 310-320 CBL FLOW INTO THE ERN CWA THAT CONTINUED TO SLOWLY DIMINISH. UPSTREAM 2-4SM VSBY WITH LIGHT SNOW WAS REPORTED OVER SRN MANITOBA INTO WRN ONTARIO...MAINLY ALONG THE MID LEVEL VORT TRACK. TODAY AND TONIGHT...THE LES OVER THE NE PORTION OF THE CWA WILL END AS WINDS BACK WSW BY MID TO LATE MORNING AHEAD OF THE APPROACHING LOW. ADDITIONAL SNOWFALL SHOULD AMOUNT TO LESS THAN AN INCH. THE BEST CHANCE FOR SNOW WITH THE MANITOBA SHORTWAVE WILL BE ALONG THE PATH OF THE MID LEVEL VORT WITH THE AREA OF MODERATE MID/UPPER LEVEL QVECTOR CONV AND STEEPER MID LEVEL LAPSE RATES. THIS WILL KEEP MOST OF THE SNOW NORTH FROM LATE MORNING INTO THE EVENING NORTH OF UPPER MI. ONLY CHANCE POPS INCLUDED VCNTY KCMX/KP59/KERY WITH SLIGHT CHANCE TO THE SOUTH AND NO PCPN MENTIONED CLOSER TO THE WI BORDER. TUESDAY AND TUESDAY NIGHT...MODELS HAVE COME INTO BETTER AGREEMENT WITH THE POSITION/STRENGTH OF THE PAC NW TROUGH AS IT MOVES INTO THE REGION. HOWEVER...GIVEN THE WELL-DEFINED LOOK OF THIS FEATURE FROM THE WV LOOP AND INITIALIZATION PROBLEMS WITH THE 00Z NAM/GFS NOTED BY HPC...THE SLIGHTLY STRONGER/DEEPER 00Z CANADIAN REG GEM...SUPPORTED BY THE ECMWF...WAS PREFERRED. AN INFLUX OF LOW LEVEL MOISTURE WITH RELATIVELY DRY AIR AOB -10C MAY ALSO RESULT IN SOME PATCHY FZDZ ALONG WITH SOME LIGHT SNOW BY MID TO LATE AFTERNOON. AGAIN THE MID LEVEL LOW TRACK WILL BRING BEST SNOW CHANCES MAINLY NORTH OF UPPER MI WITH THE POPS TAPERED FROM NORTH TO SOUTH. EXPECT DEEP MOISTURE AOA -10C OVER ALL BUT THE SOUTH BY TUE NIGHT...REDUCING CHANCES FOR FZDZ. WEDNESDAY...WITH FCST SOUNDINGS SHOWING MOISTURE RECEDING TO AROUND -8C...NRLY FLOW IN THE WAKE OF THE LOW COMBINED WITH ABUNDANT LEFTOVER LOW LEVEL MOISTURE MAY RESULT IN SOME PATCHY LIGHT SNOW OR FREEZING DRIZZLE OVER THE WEST HALF OF UPPER MI IN THE MORNING...ESPECIALLY WHERE WINDS UPSLOPE INTO HIGHER TERRAIN. && .AVIATION (FOR THE 12Z TAF ISSUANCE)... OCCASIONAL FLURRIES SEEM TO BE AFFECTING THE SAW SITE...ON THE SOUTHERN EDGE OF A BLAND OF CLOUDS THAT STRETCHES NORTHEASTERLY ACROSS LAKE SUPERIOR TO THE ARROWHEAD REGION OF MN. BEST CHANCE OF SNOW WILL REMAIN AT CMX...REMAINING IFR TO LOW MVFR THROUGH THE PERIOD...GIVEN FAVORABLE WINDS AND APPROACHING LOW LEVEL MOISTURE EVIDENT ON THE IR SAT IMG. CONTINUE TO HAVE LOW CLOUDS OVER N WI SLOWLY SLIDING NORTHEASTWARD...PARTICULARLY ACROSS THE WESTERN THIRD OF THE CWA. && .MARINE (FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)... HIGH PRESSURE OF 30.1 INCHES OVER CENTRAL AND EASTERN LAKE SUPERIOR WILL GIVE WAY TO A 29.9 INCH LOW PRESSURE SYSTEM FROM CENTRAL MANITOBA LATE THIS AFTERNOON. THIS LOW WILL EXIT TO THE EAST AND WEAKEN SIGNIFICANTLY. IT WILL BE REPLACED BY A SLIGHTLY STRONGER LOW OF 29.8 INCHES FROM CENTRAL MINNESOTA TUESDAY AFTERNOON... CROSSING UPPER MICHIGAN TUESDAY NIGHT...AND MAKING IT TO THE EASTERN GREAT LAKES BY WEDNESDAY EVENING. WINDS ARE EXPECTED TO REMAIN BELOW 30 KNOTS WITH THESE TWO SYSTEMS...AND PROBABLY EVEN AT OR BELOW 25 KNOTS. HIGH PRESSURE OF 30.0 INCHES WILL THEN OVERTAKE THE AREA. A 29.7 INCH LOW PRESSURE SYSTEM DEVELOPING OVER THE SOUTHERN PLAINS THURSDAY MORNING WILL MOVE OVER THE OHIO RIVER VALLEY ON FRIDAY. ALSO ON FRIDAY...ANOTHER LOW PRESSURE SYSTEM OF 29.6 INCHES WILL BE SLIDING OUR WAY FROM NORTH DAKOTA AND SOUTHERN MANITOBA. WINDS LESS THAN 25 KNOTS ARE EXPECTED THURSDAY AND FRIDAY. LOOKING MORE INTO THE FUTURE...IT LOOKS LIKE THE FIRST CHANCE OF GALES ON LAKE SUPERIOR WILL BE SATURDAY NIGHT AND SUNDAY...DEPENDING ON THE TRACK AND STRENGTH OF THE NEXT SIGNIFICANT SURFACE LOW. && .MQT WATCHES/WARNINGS/ADVISORIES...NONE. && $$ DISCUSSION...JLB AVIATION...KF MARINE...KF mi AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA NATIONAL WEATHER SERVICE SIOUX FALLS SD 1015 AM CDT MON DEC 17 2007 .DISCUSSION... VALLEY LOCATION TEMPERATURES STILL TRYING TO RECOVER THIS MORNING... BUT EXPECT NEAR SURFACE LAYER TO BECOME A LITTLE MORE WELL MIXED AND EVEN OUT TEMPS SOME TOWARD MIDDAY. THIS WILL BE THE MAIN CHALLENGE OF THE DAY. 12Z RUC SFC TEMPS REMAIN QUITE A BIT COOLER THAN GOING FORECAST...ABOUT 10 DEGREES IN SOME AREAS. HOWEVER...RUC TEMPS ARE ALSO COOLER ONLY 3 HOURS IN AT THE 15Z FORECAST...AND 925MB TEMPS FROM BOTH NAM AND RUC STILL FORECAST TO CLIMB INTO 3-5C RANGE BY LATE AFTERNOON...SO WILL NOT MAKE SIGNIFICANT DOWNWARD ADJUSTMENTS JUST YET. WILL KEEP A CLOSE EYE ON VALLEY TEMPS THE NEXT COUPLE OF HOURS...AND MAY HAVE TO UPDATE TOWARD MIDDAY IF WE ARE STILL STRUGGLING AS MUCH AS WE HAVE BEEN EARLY. ONE NOTE ABOUT AREA TEMPS...KHON TEMPERATURE SENSOR APPEARS TO BE REPORTING INCORRECT DATA THIS MORNING AND A TECHNICIAN IN ON THE WAY OUT THERE TO CHECK IT OUT. && .AVIATION... VFR CONDITIONS THROUGH 08Z TUESDAY. WITH POSSIBILITY OF A LITTLE MELTING SNOW ADDING MOISTURE TO BOUNDARY LAYER...POTENTIAL FOR SOME MVFR-IFR CIGS/VSBYS DEVELOPING AGAIN LATE TONIGHT INTO EARLY TUESDAY EAST OF THE JAMES RIVER. ANY FOG/STRATUS DEVELOPMENT WOULD MAINLY AFFECT KFSD TAF SITE...AND MOST LIKELY REMAIN EAST OF KHON/KSUX. && .PREV DISCUSSION... QUITE DIFFERENT EARLY THIS MORNING COMPARED TO YESTERDAY MORNING. ADMITTEDLY WE WERE WORRIED ABOUT ANOTHER POSSIBLE FOG SETUP OVR THE ERN FA EARLY TODAY...AT LEAST IN LOWER AREAS...BUT LOW LVL DRY AIR HAS INFILTRATED THE AREA AND THE SOUP HAS PUSHED OFF TO THE NRN MS VALLEY. S/W RIDGING DOMINATES THIS AREA TODAY...WITH LOW LVL WAA PUSHING FM SW TO NE. PRETTY DECENT BLOB OF ISENTROPIC LIFT COINCIDES THE WAA AREA...BUT THE ATMOSPHERE IS SO VERY DRY THAT ZERO POPS ARE WARRANTED. FOR TONIGHT...QUICK MOVG S/W PASSES THRU THIS AREA IN THE ZONAL FLOW ALOFT. ALONG THE WIND SHIFT...THE GFS H925 RH FIELD IS STILL DENOTING A LOT OF MOISTURE...THICKENING UP AS TONIGHT PROGRESSES ACROSS MUCH OF OUR ERN HALF OVR THE SNOWPACK. MAINLY FM ERN KINGSBURY CO TO NEAR ERN WOODBURY CO. THIS POTENTIAL STRATUS THEN LINGERS IN THESE AREAS TUE MORNING. HASHED OVR FOG POTENTIAL RIGHT NOW...BUT FORGOED FOR NOW. BUT DAYSHIFT MAY HAVE TO PUT IN AREAS OF FOG TONIGHT IF THE GFS H925 RH FIELD IS STILL HIGH. WHAT IS ALSO BOTHERSOME...IS NOW THE NAM RH TIME SECTIONS ARE BEGINNING TO SHOW HINTS OF THIS STRATUS JUST ABOVE 950MB...LARGELY IN THE SAME AREA. BECAUSE OF THIS STRATUS POTENTIAL...KEPT LOWS IN SW MN RELATIVELY MILD. ALTHOUGH THEIR HIGHER TERRAIN HAS ALSO BEEN HELPING TO KEEP THEM MORE MILD RECENTLY AT NIGHT. THE NEXT STRONGER WAVE TO WATCH...WHICH IS HANDLED PRETTY SIMILARLY BY THE VARIOUS MODELS IS WED AND WED NIGHT. MOISTURE PROFILE BECOMES FAIRLY SATURATED ABOVE H85 FM SW TO NE OVR THIS FA ON WED. BOTH THE NAM AND GFS CONTINUE TO SHOW THE STRONGEST DYNAMICS TO THE SOUTH OF THIS FA. BUT NOW...EVEN THE BEST ISENTROPIC LIFT ON THESE RUNS HAS SHOVED FURTHER SOUTH ALSO. STILL...BROAD ASCENT DOES EXIST ALONG WITH SOME ISENTROPIC LIFT AND STRONG MID AND UPPER -DIV Q. DECIDED TO ADD A BIT OF SLEET IN OUR FA WED AFTN. THIS IS BECAUSE THE LOW LYRS ARE STILL RELATIVELY DRY...AND THE THERMAL FIELD NEAR H85 EEKS UP TO AT OR JUST ABOVE ZERO C. WITH THE FCST WET BULB TEMPS NEAR 30...DOUBT THERE IS MUCH OF A -FZRA CHC LOOKING AT THE AMOUNT OF DRY AIR FM H85 ON DOWN. MOISTURE DOES SATURATE OVR OUR ERN HALF THOUGH SAT NIGHT. AND ONCE IT DOES SATURATE...THE WARM LYR OFF THE SFC COOLS OFF ENOUGH TO WARRANT JUST A SNOW CHC. COULD BE A MIX HERE AND THERE WED EVENING...BUT ATTM...NOT ENOUGH OF A CHC TO WARRANT PUTTING IN THE GRIDS. FOR TEMPS THRU THE PERIOD...JUST CONTINUED THE TREND OF GOING AN AVG OF 5 TO 10 DEGS BLO THE MET FOR HIGHS. MANY OF THE MAX AND MIN READINGS ARE SO ELEVATION DEPENDENT. OF COURSE WENT MUCH WARMER IN OUR SW QUAD WHERE A TAD BIT OF MIXING MAY OCCUR DURING DAYTIME... GIVING READINGS NEAR OR SLIGHTLY ABOVE THE MAV. AND IN SW MN... HIGHER TERRAIN WL ALSO MODERATE THE TEMPS SOME...ESP AT NIGHT... WITH THE ABSENCE OF AN ARCTIC AIRMASS THRU MID WEEK. BUT ELSEWHERE...SNOW FIELD WHICH HAS GLACIERIZED MANY LOCATIONS WILL GREATLY INHIBIT WARMING...AND OBVIOUSLY ENHANCE THE COOLING AT NIGHT. THEREFORE WENT A FEW DEGS BLO THE COOLER MAV GUIDANCE IN THOSE LOCATIONS...ESP IN OUR LOWER SITES. SLY FLOW ON MON AND WED WILL BE COMING OFF SNOWPACK FM ERN NEB AND FAR WRN IA NOT HELPING MATTERS ANY. ON TUE...THE WIND WILL BE FM THE W TO NW. HOWEVER THE SFC WINDS WL ONCE AGAIN BE RELATIVELY LIGHT INHIBITING MIXING COUPLED WITH SUBTLE CAA. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...NONE. MN...NONE. IA...NONE. NE...NONE. && $$ JH sd AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE JACKSONVILLE FL 230 PM EST MON DEC 17 2007 ...FREEZE IN STORE FOR MOST OF THE AREA WITH HARD FREEZE CONDITIONS POSSIBLE THROUGH TUESDAY MORNING... .SHORT TERM...SURFACE ANALYSIS SHOWS HIGH PRESSURE HAS SETTLED OVER THE LOWER MISSISSIPPI VALLEY WITH RIDGE ACROSS THE INTERSTATE 10 CORRIDOR OF FLORIDA. THIS RESULTED IN A NORTH TO NORTHWEST FLOW REGIME LAST NIGHT WHICH HAS QUICKLY TRANSITIONED TO A NORTH- NORTHEAST REGIME THIS MORNING OVER NORTHEAST FLORIDA. AS A RESULT...COLD AIR ADVECTION CU WHICH HAD BEEN POISED JUST OFFSHORE IS BEGINNING TO ADVECT IN...GENERALLY SOUTH OF DUVAL COUNTY. ALOFT...LATEST RUC SHOWS EAST COAST MID LEVEL TROUGH REALLY SHALLOWS OUT AS YOU GET CLOSER TO OUR AREA WITH LARGELY ZONAL FLOW DEPICTED. THIS EXTENDS UP TO 250MB WHERE A WELL DEFINED JET STREAK EXTENDS WESTWARD THOUGH TEXAS AND EVENTUALLY BAJA AND MAY LEAD TO AN INCREASE IN HIGH LEVEL CLOUDS LATER TONIGHT. MAIN SHORT TERM ISSUE WILL BE THE LOW TEMPS FOR TONIGHT AND CERTAINLY NOT A CLEAR CUT CASE. MODEL GUIDANCE HAS BEEN IN GOOD AGREEMENT FOR THIS EVENT WITH ABOVE AVERAGE RUN TO RUN CONSISTENCY...ADVERTISING UPPER 20S FOR MOST LOCATIONS WITH ISOLATED POCKETS OF HARD FREEZE CONDITIONS POSSIBLE. UNCERTAINTIES WITH THIS EVENT RELATE TO DEVELOPING EASTERLY COMPONENT UP TO 850 MB AND ANY RESULTANT LOW LEVEL CLOUDS FROM THIS AND THE WESTWARD EXTENT OF THESE CLOUDS. IN ADDITION...AFOREMENTIONED CIRRUS WILL INCREASE JUST PRIOR TO 12Z WHICH MAY INHIBIT LATE TEMPERATURE FALLS. FOR NOW...BELIEVE AREAS WEST OF INTERSTATE 95 WILL BE LARGELY UNAFFECTED BY THE EASTERLY FLOW WITH A DRAINAGE FLOW DEVELOPING AFTER MIDNIGHT. CIRRUS MAY HAVE SOME EFFECTS BUT WILL BE LIMITED. THIS LEAVES ME LEANING TOWARD THE GUIDANCE FOR INLAND AREAS AND CURRENT FREEZE WARNING LOOKS ON TRACK. SOME OF THE COLDER LOCATIONS INCLUDING SOME CO-OP SITES WILL LIKELY SEE A PERIOD OF HARD FREEZE CONDITIONS AS WELL AND WILL USE ENHANCED WORDING IN THE NPW. FOR TUE...HIGH CONTINUES TO SHIFT OFFSHORE WITH EASTERLY FLOW FOR THE ENTIRE AREA ALLOWING FOR AIRMASS MODERATION. MODELS IN GOOD AGREEMENT WITH A SHORTWAVE DIVING DOWN TUESDAY THROUGH THE DEEP SOUTH AND INITIATING AN INVERTED TROUGH ALONG THE EAST COAST. THIS WILL LEAD TO A FURTHER INCREASE IN CLOUDS AND A SLIGHT CHANCE OF SHOWERS ALONG THE COAST. AS SHORTWAVE PUSHES THROUGH...TROUGH SHIFTS EAST AND AREA BEGINS ANOTHER CLEARING TREND. NEXT SYSTEM ON TAP FOR THU WITH NAM12 AND GFS SHOWING SIGNIFICANT DIFFERENCES. GFS KEEPS TO DISTINCT BRANCHES OF MID LEVEL JET WHILE NAM12 SHOWS A MORE UNIFORM CENTRAL STATES TROUGH. SURFACE LOW IS THEREFORE MUCH FURTHER SOUTH WITH GFS DEPICTION THAN THE NAM12 BUT PRECIP FIELDS ARE SOMEWHAT SIMILAR. WILL USE A BLEND FOR NOW WHICH RESULTS IN MID RANGE POPS BUT THIS MAY NEED TO BE INCREASED WITH SUBSEQUENT FORECASTS. .LONG TERM...LOOKS LIKE DRY CONDITIONS UNTIL THE NEXT SYSTEM WHICH GFS ADVERTISES FOR SUN EVENING. PARENT LOW IS WELL TO THE NORTH WITH THIS SYSTEM WITH JUST A TRAILING COLD FRONT IN STORE FOR OUR AREA. && .AVIATION...VFR CONDITIONS EXPECTED THROUGH LATE TONIGHT. HIGH CLOUDS WILL STREAM IN FROM THE W THROUGH TUE. MODELS SUGGEST INCREASING LOW LEVEL MOISTURE AS ONSHORE FLOW DEVELOPS BY EARLY MORNING WITH STRATOCU ADVECTING INLAND AFTER ABOUT 06Z. HAVE INDICATED MVFR CIGS AROUND 3 KFT FOR JAX...CRG AND SSI BY ABOUT 13Z. MVFR CIGS COULD OCCUR SOONER BASED ON NAM MOISTURE FIELDS BUT AT THIS TIME NOT VERY CONFIDENT IN THAT SCENARIO. && .MARINE...SEAS LIKELY UP IN THE 6-7 FT RANGE OFFSHORE SO WILL MAINTAIN THE SCA THROUGH THIS AFTERNOON. WEAKER FLOW WILL TAKE SHAPE TUE AND WED AS INVERTED TROUGH DEVELOPS OVER THE COASTAL WATERS. GFS INDICATES 1012 MB LOW CROSSING OVER THE REGION THU NIGHT INTO FRIDAY BUT TENDED TO DOWNPLAY THIS PROG BASED ON COMPARISON FROM ECMWF AND THE GFS ENSEMBLE. && .FIRE WEATHER...RED FLAG WARNING WILL MOSTLY LIKELY VERIFY OVER THE FL ZONES BUT IS QUESTIONABLE OVER SE GA ZONES. A FEW SPOTS MAY VERIFY IN SE GA SO MAY LET THE WARNING RIDE. HIGHER RH VALUES EXPECTED FOR TUE SO THIS TIME NO FIRE WEATHER WATCH/WARNINGS ARE PLANNED AT THIS TIME. && .PRELIMINARY POINT TEMPS/POPS... AMG 26 58 35 66 / 0 0 10 0 SSI 37 58 45 64 / 0 10 20 0 JAX 29 60 42 68 / 0 0 20 0 SGJ 38 62 47 68 / 0 10 20 10 GNV 27 65 42 71 / 0 0 10 0 OCF 30 66 44 72 / 0 0 10 0 && .JAX WATCHES/WARNINGS/ADVISORIES... FL...FREEZE WARNING FROM 11 PM THIS EVENING TO 9 AM EST TUESDAY FOR ALACHUA-BAKER-BRADFORD-COLUMBIA-GILCHRIST-HAMILTON-MARION- SUWANNEE-UNION. FREEZE WARNING FROM 2 AM TO 8 AM EST TUESDAY FOR CLAY-DUVAL- NASSAU-PUTNAM. RED FLAG WARNING UNTIL 5 PM EST THIS AFTERNOON FOR ALACHUA-BAKER- BRADFORD-CLAY-COLUMBIA-DUVAL-GILCHRIST-HAMILTON-MARION- NASSAU-PUTNAM-SUWANNEE-UNION. GA...RED FLAG WARNING UNTIL 4 PM EST THIS AFTERNOON FOR APPLING- ATKINSON-BACON-BRANTLEY-CHARLTON-CLINCH-COFFEE-ECHOLS-JEFF DAVIS-PIERCE-WARE-WAYNE. FREEZE WARNING FROM 11 PM THIS EVENING TO 9 AM EST TUESDAY FOR APPLING-ATKINSON-BACON-BRANTLEY-CHARLTON-CLINCH-COFFEE- ECHOLS-JEFF DAVIS-PIERCE-WARE-WAYNE. FREEZE WARNING FROM 2 AM TO 8 AM EST TUESDAY FOR INLAND CAMDEN- INLAND GLYNN. AM...SMALL CRAFT ADVISORY UNTIL 9 PM EST THIS EVENING FOR ST AUGUSTINE TO FLAGLER BEACH FL 20 NM TO 60 NM OFFSHORE. SMALL CRAFT ADVISORY UNTIL 4 PM EST THIS AFTERNOON FOR ALTAMAHA SOUND GA TO FERNANDINA BEACH FL 20 NM TO 60 NM OFFSHORE- FERNANDINA BEACH TO ST AUGUSTINE FL 20 NM TO 60 NM OFFSHORE. && $$ DEESE/SHASHY/WALKER fl AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE DES MOINES IA 1117 AM CST MON DEC 17 2007 UPDATED AVIATION DISCUSSION .SHORT TERM /TODAY/... FORECAST SOUNDINGS CONTINUE TO SHOW A STRONG LOW LEVEL INVERSION WITH WARMER AIR SHOOTING OVER THE COLD...SNOWPACK ENHANCED SURFACE AIR. RUC/NAM/GFS SOUNDINGS ALL KEEP SFC TEMPS BELOW FREEZING TODAY...SO HAVE UPDATED THE FORECAST TO HEDGE A LITTLE LOWER ON MAX TEMP TODAY. ALSO CLEARED OUT THE FOG/STRATUS AND EXPECT US TO HAVE A FULL DAY OF SUNSHINE WITH MAYBE SOME CIRRUS SPREADING IN FROM THE WEST DURING THE AFTERNOON. .PREVIOUS DISCUSSION... THE STRATUS AND FOG OVER THE CWA IS FINALLY CLEARING OUT AND TEMPS ARE BEGINNING TO FALL. AS SURFACE HIGH PRESSURE PUSHES ACROSS THE SOUTHERN PLAINS EASTWARD...THE FLOW WILL PREDOMINANTLY BECOME SOUTHWESTERLY THEN SOUTHERLY. WITH THE CURRENT SNOW PACK I FEEL THAT GUIDANCE IS TOO WARM...AS IT HAS BEEN OVER THE LAST SEVERAL DAYS. THEREFORE...DESPITE BETTER SUNSHINE TODAY I KNOCKED TEMPS BACK HALF A CATEGORY OR SO. SOUTHERLY WINDS INCREASE SOME MONDAY NIGHT THROUGH TUESDAY. THIS COMBINED WITH A MORE ZONAL FLOW ALOFT SHOULD ALLOW FOR BETTER WARMING BY MID WEEK. A WEAK AND FAST MOVING DISTURBANCE SHOULD KEEP SOME CLOUD COVER OVER THE STATE FOR TUESDAY AND SMALL CHANCE POPS OVER THE NORTHERN QUARTER OF THE CWA. WEAK RIDGING THEN BUILDS BACK OVER CENTRAL IOWA TUESDAY NIGHT AND WEDNESDAY BEFORE A MORE SIGNIFICANT SHORT WAVE MOVES IN WEDNESDAY NIGHT AND THURSDAY. MODELS CONTINUE TO DIFFER ON THIS BUT THEY SEEM TO HINT AT SPLITTING THE ENERGY IN THIS SHORTWAVE KEEPING THE BETTER PRECIP SOUTH OF THE STATE AND ONLY DRIBBLE SOME LIGHT QPF OVER US. OUT OF THE DAY 5 PERIOD...THE NEXT STORM TO AFFECT IOWA WILL BE FRIDAY NIGHT/SATURDAY BUT TODAYS EUROPEAN WAS LOOKING LIKE YESTERDAYS GFS WITH LITTLE CHANGE IN THAT FROM YESTERDAY. ONE BIG DIFFERENCE IS THAT THE GFS IS NOW KEEPING THE SHORTWAVE OPEN AND NOT PRODUCING A CLOSED LOW WITH THIS AND THE OTHER NOTEWORTHY ITEM IS THAT THE SURFACE LOW DOES NOT INTENSIFY UNTIL IT GETS EAST OF US. STILL LOTS OF VARIABLES BUT WE SHOULD SEE SOMETHING FOR SATURDAY. AS FOR TEMPS...STILL KEPT THEM BELOW GUIDANCE AS IT HAS NOT BEEN DOING WELL WITH TEMPS IN THE SNOW PACK. && .AVIATION...17/18Z MVFR VSBY SLOW TO ERODE...BUT SHOULD DURING THE 18-20Z TIME FRAME. WILL THEN HAVE LARGELY VFR CONDITIONS THROUGH THE NIGHT. HOWEVER...BY MORNING WITH SFC LOW CROSSING NRN IA/SRN MN...ENOUGH LOW LEVEL MOISTURE CONVERGENCE AROUND TO BRING MVFR VSBY TO MANY LOCATIONS...WITH MVFR CEILINGS LIKELY AT KMCW. && .DMX WATCHES/WARNINGS/ADVISORIES...NONE. && $$ SHORT TERM...MOYER LONG TERM...FAB AVIATION...MOYER ia AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MARQUETTE MI 354 PM EST MON DEC 17 2007 .SYNOPSIS... 20Z WATER VAPOR LOOP AND RUC 500MB HEIGHT ANALYSIS SHOWS NEARLY ZONAL FLOW FROM THE PACIFIC ACROSS THE U.S....WITH SOME WEAK RIDGING OVER THE CENTRAL PLAINS. WITHIN THE ZONAL FLOW...THERE ARE A FEW FEATURES TO NOTE: AN UPPER LOW JUST SOUTH OF PICKLE LAKE ONTARIO AND A SHRTWV TROUGH OVER IDAHO. THE UPPER LOW CAN BE SEEN WELL ON VISIBLE SATELLITE IMAGERY...WITH A TWIST IN THE LOW CLOUDS OVER NW ONTARIO. OTHER LOW CLOUDS WERE PRESENT FROM LAKE MICHIGAN INTO THE EASTERN U.P. AND BETWEEN PARK FALLS AND WAUSAU. THE LOW CLOUD PATCH BETWEEN PARK FALLS AND WAUSAU WAS MUCH MORE EXPANSIVE EARLIER TODAY...ENCOMPASSING MUCH OF WI INTO THE WI BORDER COUNTIES. HOWEVER...THE SHALLOW NATURE OF THE LOW CLOUDS SEEN ON TAMDAR SOUNDINGS AND THE HEATING FROM THE WEAK DECEMBER SUN WAS ABLE TO MIX MUCH OF THOSE LOW CLOUDS OUT. 18Z TAMDAR SOUNDING FROM RHI STILL DEPICTS A STRONG INVERSION AROUND 900MB...THOUGH...WITH TEMPS CLIMBING FROM -10C AT 925MB TO 0C AT 870MB. OTHER LOW CLOUDS WHICH HAVE BEEN ABLE TO HOLD TOGETHER BETTER DUE TO LAKE MOISTENING WERE PRESENT FROM WESTERN LAKE SUPERIOR INTO THE KEWEENAW. AT THE SURFACE ASSOCIATED WITH THE UPPER LOW IS A 1010MB LOW TO THE WEST OF THUNDER BAY ONTARIO...WITH A COLD FRONT EXTENDING WEST INTO FAR NW MN. FARTHER WEST...LOW PRESSURE IS DEVELOPING NEAR RAPID CITY IN THE DOWNSLOPE ZONAL FLOW AHEAD OF THE IDAHO SHRTWV. && .SHORT TERM (TONIGHT AND TUE)... THE SYNOPTIC PATTERN FORECAST DURING THIS PERIOD IS QUITE EASY... WITH MODELS IN GOOD AGREEMENT THROUGH TUE. SHRTWV AND SURFACE LOW IN NW ONTARIO HEAD INTO QUEBEC TONIGHT...WITH A COLD FRONT DROPPING SOUTH INTO THE KEWEENAW PENINSULA AND BECOMING STATIONARY. THEN ON TUE...THE SHRTWV TROUGH OVER IDAHO MOVES INTO WI BY 00Z...BRINGING THE SURFACE LOW OVER RAPID CITY INTO SOUTH CENTRAL UPPER MI. ALTHOUGH THE SYNOPTIC PATTERN IS EASY...THERE ARE MANY ISSUES WITH THIS FORECAST...PARTICULARLY WITH CLOUD COVER (THUS TEMPERATURES TOO). DESPITE THAT SKIES CLEARED OUT THIS AFTERNOON...LIGHT WEST TO SW WINDS SHOULD ALLOW TEMPERATURES TO DROP QUICKLY THIS EVENING. GIVEN THE STRONG INVERSION PRESENT ON THE RHI TAMDAR SOUNDING...A LOW CLOUD DECK COULD REDEVELOP LATE THIS EVENING OVER THE HIGHER TERRAIN OF NORTHERN WI AND WESTERN UPPER MI. THIS IS SUGGESTED TOO BY THE RUC AND NAM. HOWEVER...THE GFS SOUNDINGS INDICATE ENOUGH WIND TO KEEP THE LOW LEVELS MIXED ENOUGH TO PREVENT THAT LOW CLOUD DECK FROM FORMING. HAVE FOLLOWED THE NAM/RUC SCENARIO...BUT EITHER SCENARIO AT THIS POINT SEEMS LIKELY. THUS...HAVE LOWEST TEMPS OCCURRING JUST AFTER MIDNIGHT (WHICH WERE DROPPED A FEW DEGREES FROM PREVIOUS FORECAST GIVEN CLEAR SKIES PRESENT NOW) AND THEN RISING AFTERWORDS. EVENING SHIFT WILL NEED TO WATCH THE CLOUDS AND TEMPS CLOSELY. BOTH SCENARIOS...HOWEVER...DEPICT THE SAME THING OVER THE KEWEENAW. AS THE COLD FRONT OVER NW MN DROPS DOWN INTO THE KEWEENAW...IT WILL BRING THE LOW CLOUDS OVER WESTERN LAKE SUPERIOR INTO THERE. ENOUGH COLD AIR NEAR 925MB LOOKS TO COME IN TOO WITH THE FRONT TO GENERATE SOME LAKE ENHANCEMENT. THIS ENHANCEMENT COMBINED WITH UPSLOPING FLOW COULD PRODUCE EITHER FREEZING DRIZZLE OR LIGHT SNOW...GIVEN THAT THE TOP OF THE INVERSION TEMPERATURE IS AROUND -8C. ANOTHER AREA WHERE LOW CLOUDS SHOULD DEVELOP TONIGHT IS ACROSS MN AND WESTERN WI AS THE SURFACE LOW OVER RAPID CITY WOUNDS UP AND MOVES EAST. AS THIS LOW HEADS TOWARDS UPPER MI...EXPECT LOW CLOUDS TO EXPAND ACROSS THE CWA...ESPECIALLY IN THE WESTERN U.P. WHERE NORTHEAST WINDS CAN ADVECT THE LAKE ENHANCED LOW CLOUDS SOUTHWESTWARD. QUESTION THEN IS ABOUT PCPN SINCE THE SHRTWV TROUGH IS APPROACHING THE AREA...WHICH MEANS WE WILL BE UNDER DPVA. SOUNDINGS DEPICT SOME DRY AIR THAT NEEDS TO BE OVERCOME IN THE LOW TO MID-LEVELS INTO THE EARLY AFTERNOON. THUS...POPS FOR PCPN WILL REMAIN AFTER 18Z...EXCEPT OVER THE KEWEENAW WHERE UPSLOPING FLOW COULD RESULT IN PCPN OUT OF THE LOW CLOUD DECK IN THE MORNING. AS FAR AS PCPN TYPE GOES IN THE AFTERNOON...IF THE DRY AIR IS FULLY OVERCOME AS SUGGESTED BY THE GFS...THEN WE WILL ONLY BE DEALING WITH SNOW...SINCE ANY SUPERCOOLED WATER DROPLETS IN THE LOW CLOUD LAYER WOULD BE PICKED UP BY DENDRITES ALOFT. HOWEVER...THE NAM SUGGESTS MORE DRY AIR IN THE AFTERNOON...WHICH COULD RESULT IN EITHER FREEZING DRIZZLE OR SNOW. THUS BOTH TYPES WILL REMAIN IN THE GOING FORECAST. GOING HIGH TEMPERATURES SEEM REASONABLE. .LONG TERM (TUE NIGHT THROUGH NEXT MON)... THE WEAK SHORTWAVE WILL SAIL ACROSS UPPER MICHIGAN TUESDAY NIGHT. THE SURFACE LOW WILL MOVE INTO NORTHERN LAKE HURON. THE ACCOMPANYING FRONTAL SYSTEM WILL STRETCH ACROSS THE U.P. FROM KIMT TO ST IGNACE AT 00Z. ISENTROPIC ASCENT AHEAD OF THE LOW WITH THE SHORTWAVE WILL PRODUCE A CHANCE OF LIGHT SNOW ACROSS THE AREA. THE SNOW GROWTH AREA SEEMS TO BE ABOVE THE LOW LEVEL MOISTURE FIELD. THUS THE TEMPERATURE FORECAST PROFILE SUGGEST A POSSIBILITY OF SNOW MIXED WITH SOME FREEZING DRIZZLE ACROSS THE SOUTHERN PART OF THE FORECAST AREA AS SURFACE TEMPERATURES WILL BE A LITTLE BELOW FREEZING. ELSEWHERE...CONDITIONS LOOK FAVORABLE FOR SNOW DEVELOPMENT. THE SHORTWAVE WILL SHIFT OFF TO THE EAST OF THE FORECAST AREA AS A WEAK RIDGE SLIDE OVER THE WESTERN U.P. ON WEDNESDAY. THE LOW WILL MOVE INTO THE LOWER GREAT LAKES WHILE A SURFACE RIDGE LINES UP OVER ONTARIO AND THE UPPER GREAT LAKES REGION. DRIER AIR WILL ADVECT INTO THE REGION BEHIND THE LOW AND END THE PRECIPITATION CHANCES OVER THE WEST. A LOW WILL DEVELOP OVER THE CENTRAL PLAINS AND TRACK INTO THE MIDDLE MISSISSIPPI RIVER VALLEY WEDNESDAY NIGHT AS ANOTHER LOW DEVELOPS OVER ALBERTA AND MOVE INTO SOUTHERN MANITOBA. A SHORTWAVE WILL START TO PUSH INTO THE WESTERN U.P. SOUTHERLY WINDS BEHIND THE LOW WILL DRAW A LITTLE LOW LEVEL MOISTURE INTO THE AREA...MAINLY OVER THE WEST END. ISENTROPIC ASCENT AHEAD OF THE MANITOBA LOW AND NORTHEAST OF THE MISSISSIPPI RIVER VALLEY LOW COULD BRING SOME SHOWERS INTO WESTERN LAKE SUPERIOR OVER NIGHT. THE SOUTHERLY FLOW WILL HELP HOLD THE TEMPERATURES UP. THE WEAK MID LEVEL TROUGH WILL RELOCATE OVER THE CENTRAL U.P. ON THURSDAY. THE MANITOBA LOW WILL WEAKEN AND MERGE WITH ANOTHER SURFACE LOW OVER SOUTHERN SASKATCHEWAN. A SOUTHERLY FLOW WILL CONTINUE TO BRING WARMER AIR INTO THE REGION. THE TEMPERATURES WILL STILL BE COLD ENOUGH THAT ANY PRECIPITATION THAT FORMS WILL BE SNOW. THE AIR MASS IS STILL DRY ENOUGH TO CONSIDER ONLY A SLIGHT CHANCE OF SNOW SHOWERS. THE SHORTWAVE OVER WISCONSIN AND WESTERN LAKE SUPERIOR WILL SHIFT INTO EASTERN U.P. THURSDAY NIGHT. TWO SHORTWAVES WILL BE EJECTED OUT OF THE LONGWAVE TROUGH. THE FIRST WILL REACH THE ARROWHEAD OF MINNESOTA AS THE SECOND REACHES THE CENTRAL DAKOTAS. THE FIRST SHORTWAVE WILL SWEEP THROUGH THE FORECAST AREA ON FRIDAY AS THE SECOND ONE EDGES INTO NORTHWEST MINNESOTA. THE SURFACE LOW OVER EASTERN MONTANA WILL SHIFT EASTWARD TO NORTHWEST MINNESOTA ON FRIDAY. 30F SURFACE DEW POINTS WILL BE STREAMING NORTH FROM THE GULF IN THE CYCLONIC FLOW AHEAD OF THE LOW. THE 850MB 0C ISOTHERM WILL PUSH INTO THE FORECAST AREA SUGGESTING THAT THE PRECIPITATION WILL BE IN THE FORM OF RAIN. THE WEAK UPPER LEVEL ENERGY...ISENTROPIC ASCENT AND AVAILABLE LOW LEVEL MOISTURE WOULD SUGGEST AN INCREASE CHANCES OF SNOW IN THE AFTERNOON. THE LOW WILL SWING OUT OF CENTRAL HIGH PLAINS INTO IOWA ON SATURDAY AND ACROSS NORTHERN LOWER MICHIGAN ON SUNDAY REACHING SOUTHERN QUEBEC ON MONDAY. USING THE THICKNESSES AND SOUNDING PROFILES...IT APPEARS THAT THERE WILL BE A MIX BAG A PRECIPITATION MOVING THROUGH THE AREA SATURDAY AFTERNOON AND NIGHT. GFS IS ACTUALLY MOVING THE WARMER AIR IN A LITTLE EARLIER THAN THE EC...BUT WILL STICK WITH THE EC SOLUTION FOR NOW...SINCE SYSTEMS SEEMS TO BE SLOWING DOWN MORE THAN SPEEDING UP. THE MAIN CONCERN WILL BE FOR THE POSSIBILITY OF FREEZING RAIN OR WET ROADS FREEZING OVERNIGHT MAKING IT PARTICULARLY HAZARDOUS FOR HOLIDAY TRAVELERS. && .AVIATION (FOR THE 18Z TAF ISSUANCE)... TAF FORECASTS ARE TROUBLESOME TODAY. LOW CLOUDS AND MIST THAT WERE OVER NORTHERN WISCONSIN AND HEADING UP INTO UPPER MICHIGAN HAVE BEEN DISSIPATING OVER THE PAST HOUR...AND PROBABLY WILL CONTINUE TO DISSIPATE THROUGH THIS AFTERNOON WITH EXTRA HEATING. SO ALTHOUGH A BKN IFR OR LOW MVFR DECK MAY COME INTO SAW SHORTLY SINCE THE CLOUDS ARE ON THE DOORSTEP...HAVE ONLY INCLUDED A TEMPO GROUP UNTIL 20Z. AS NIGHTTIME COOLING SETS IN...THESE CLOUDS AND MIST SHOULD REDEVELOP...PROBABLY NEAR OR JUST AFTER MIDNIGHT. AT CMX...SOME LOW IFR CLOUDS ARE CURRENTLY OVER THE AIRPORT...BUT ARE MOVING NE. THUS THESE CLOUDS SHOULD SCATTER/CLEAR OUT IN THE NEXT HOUR OR TWO. HOWEVER...LURKING OFF ON WESTERN LAKE SUPERIOR IS EXTENSIVE LOW CLOUDS WITH LIFR CIGS. AS A COLD FRONT CURRENTLY UP IN NW MN APPROACHES THE KEWEENAW THIS EVENING...THESE CLOUDS WILL MOVE BACK IN...WITH THE POSSIBILITY FOR SOME FREEZING DRIZZLE OR LIGHT SNOW AS LAKE EFFECT ENHANCES THE CLOUDS. EXPECT LOW CLOUDS TO PERSIST AT BOTH TAF SITES INTO TUE...WITH LIFR CEILINGS...IFR VSBYS AND FREEZING DRIZZLE/LIGHT SNOW. && .MARINE (FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)... LOW PRESSURE NEAR INTERNATIONAL FALLS MN WILL DROP SE ACROSS LAKE SUPERIOR TONIGHT. SW WINDS UP TO 25 KT AHEAD OF THE LOW WILL CONTINUE THIS EVENING...THEN DIMINISH AFTER MIDNIGHT. AS THE COLD FRONT ASSOCIATED WITH THE LOW DROPS SOUTH LATE TONIGHT...AND THEN AS LOW PRESSURE MOVES FROM SOUTH DAKOTA INTO SOUTH CENTRAL UPPER MI...NORTHEAST WINDS ARE EXPECTED TO INCREASE TO 15 TO 25 KT DOWN WESTERN LAKE SUPERIOR. WINDS SHOULD DIMINISH TUE NIGHT AND WED AS THE LOW MOVES AWAY FROM LAKE SUPERIOR AND A RIDGE OF HIGH PRESSURE BUILDS IN. AS THIS RIDGE MOVES OFF TO THE EAST THU...SOUTHERLY FLOW WILL INCREASE ON LAKE SUPERIOR. WINDS SHOULD REMAIN BELOW 30 KT...THOUGH FOR THU INTO FRI. A STRONG SURFACE LOW IS EXPECTED TO MOVE TOWARDS THE WESTERN GREAT LAKES ON SAT. DEPENDING ON THE TRACK AND TIMING...WE COULD BE DEALING WITH GALE FORCE WINDS...BUT RIGHT NOW THE BEST POSSIBILITY FOR GALES APPEARS TO BE VERY LATE SAT NIGHT OR INTO THE DAY ON SUNDAY AS THE LOW HEADS INTO EASTERN ONTARIO. && .MQT WATCHES/WARNINGS/ADVISORIES...NONE. && $$ SYNOPSIS/SHORT TERM...AJ LONG TERM...DLG AVIATION/MARINE...AJ mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GAYLORD MI 344 PM EST MON DEC 17 2007 .DISCUSSION...SURFACE/SATELLITE/RUC ANALYSIS THIS AFTERNOON REVEALS A WARM FRONT LIFTING NORTHEAST ACROSS NORTHERN MICHIGAN. MOISTURE TRAPPED BELOW A 925 MB INVERSION BEHIND THIS BOUNDARY ACROSS MUCH OF WISCONSIN AND LOWER MICHIGAN HAS BEEN MIXING OUT THIS AFTERNOON WITH SUNNY SKIES BREAKING OUT ACROSS MUCH OF THE REGION. HOWEVER...SOME VERY SHALLOW SFC-925MB LAKE INSTABILITY REMAINS...KEEPING THE LAKE MICHIGAN SHORELINE STUCK IN SOME LOW CLOUD COVER. WITH WARM FRONT LIFTING ACROSS NORTHERN MICHIGAN...STILL EXPERIENCING SOME LOW CLOUD COVER ALONG AND JUST NORTH OF THE BOUNDARY IN EASTERN UPPER MICHIGAN. FORECAST CONCERNS IN THE NEAR TERM REVOLVE AROUND CLOUD COVER ISSUES IMPACTING LOW TEMPERATURES TONIGHT...THEN FOCUS SHIFTS TO AN ALBERTA CLIPPER SYSTEM DROPPING INTO THE GREAT LAKES REGION LATE TOMORROW AFTERNOON AND TOMORROW NIGHT. MODELS ARE IN DECENT AGREEMENT WITH REGARDS TO THE NEXT 18 HOURS AND USED A BLEND THROUGH THIS TIME PERIOD. HOWEVER...THEY START TO DIVERGE WITH THE APPROACH OF OUR NEXT SYSTEM TOMORROW AFTERNOON. FOR THIS FORECAST...FAVORING A SLIGHTLY SLOWER AND MILDER NAM SOLUTION AS THE GFS SEEMS TO ALLOW THE SYSTEM TO COOL THE SYSTEM MUCH TOO FAST. TONIGHT...FRONTAL BOUNDARY WILL CONTINUE TO LIFT TO THE NORTH OF THE SOO THIS EVENING. THIS FRONTAL BOUNDARY WILL EVENTUALLY STALL JUST TO THE NORTH AND REMAIN THERE THROUGH TUESDAY AFTERNOON. MODELS ARE INSISTENT ON KEEPING SOME SHALLOW (SFC-925MB) LAKE INSTABILITY GOING THROUGH TOMORROW MORNING WITH DELTA TS IN THIS LAYER ABOVE 6C. WITH SOUTHWEST WINDS EXPECTED...CLOUDS WILL BE MOST PERSISTENT ALONG THE LAKE MICHIGAN SHORELINE... STRETCHING UP INTO EASTERN UPPER MICHIGAN TONIGHT. ALL OTHER AREAS SHOULD REMAIN MOSTLY CLEAR AND QUIET. AREAS UNDER THE CLOUDS WILL REMAIN MILDER TONIGHT WITH LOWS ONLY IN THE 20S...WHILE LOCATIONS UNDER THE CLEAR SKIES WILL FALL BACK INTO THE TEENS. TOMORROW...SHORTWAVE WILL PUSH EASTWARD ACROSS THE NORTHERN PLAINS...WITH A CORRESPONDING SURFACE LOW. THIS SYSTEM WILL TRACK INTO THE WESTERN GREAT LAKES LATE IN THE DAY. MODEL SOUNDINGS SHOW A NICE SATURATED LAYER BELOW 800MB...WHICH ALL REMAINS WARMER THAN -10C. THIS WOULD POSE A FREEZING DRIZZLE THREAT BY LATE IN THE AFTERNOON. HOWEVER...WITH THE SHORTWAVE PASSAGE THERE IS SOME 700-500MB RH GREATER THAN 60 PERCENT CROSSING THE AREA. THIS WOULD PROVIDE THE POTENTIAL TO GENERATE SOME SEEDER/FEEDER PROCESSES AND INTRODUCE SOME ICE NUCLEI INTO THE LOWER CLOUD LAYER. THUS...CANNOT RULE OUT SOME LIGHT SNOW. FOR NOW...WILL GO WITH A MIXTURE OF FREEZING DRIZZLE AND LIGHT SNOW FOR LATE TOMORROW AFTERNOON. KAS TUESDAY NIGHT...USED A BLEND OF THE 00Z ECMWF AND THE 12Z NAM FOR THE PREVIOUSLY MENTIONED PACIFIC SHORTWAVE DUE TO CROSS THE AREA...SINCE THE 12Z GFS IS COOLER AND MORE MOIST THAN THE MAJORITY OF GUIDANCE. PACIFIC SHORTWAVE WILL MOVE ACROSS THE UPPER PENINSULA OVERNIGHT WITH A WEAK 1012MB SURFACE LOW EXPECTED TO TRAVEL ACROSS THE TIP OF THE MITT. A MODERATE POCKET OF 700-500MB -DIVQ WILL BE ASSOCIATED WITH THIS SHORTWAVE...BUT LIMITED MOISTURE DEPTH MAKES PRECIP TYPE PROBLEMATIC. ALTHOUGH THE BEST MOISTURE WILL RESIDE NORTH OF THE SOO ALONG A LOW-LEVEL BAROCLINIC ZONE...ENOUGH MOISTURE SEEMS TO BE PRESENT NORTH OF THE SURFACE LOW TRACK FOR THE PREDOMINANT PRECIP TYPE TO BE ALL SNOW DESPITE A 3-4KFT DRY WEDGE CENTERED AROUND 875MB. FARTHER SOUTH...PROGGED SOUNDINGS INDICATE MOISTURE DEPTH INCREASES TO AROUND -10C ISOTHERM (UP TO AROUND 750MB) OVER NORTHERN LOWER. THIS WOULD INDICATE THAT A CHANCE FOR BOTH FREEZING DRIZZLE AND LIGHT SNOW WOULD BE PRESENT BASED UPON ICE NUCLEATION TEMPERATURES. SOME ENHANCEMENT MAY BE POSSIBLE AS WINDS SHIFT TO THE NORTH OR NW AND DELTA T/S INCREASE AROUND 13C...BUT HARD TO SAY IF THIS WILL HAVE AN IMPACT ON PRECIP TYPE. WEDNESDAY...SHORTWAVE AND ASSOCIATED MID-LEVEL MOISTURE AND SURFACE LOW MOVE EAST OF THE AREA DURING THE MORNING. HOWEVER...LOW-LEVEL MOISTURE BELOW 850MB STILL SEEMS TO SUGGEST A CHANCE FOR FREEZING DRIZZLE ALONG WITH THE LIGHT SNOW IN THE MORNING. CYCLONIC FLOW LOOSENS ITS GRIP DURING THE AFTERNOON AS A WEAK SURFACE RIDGE AXIS APPROACHES FROM THE WEST. MOISTURE CONTINUES TO SHALLOW OUT DURING THE PM HOURS AND ALTHOUGH SKIES WILL BE CLOUDY...THINK FREEZING DRIZZLE WILL ONLY BE POSSIBLE ACROSS THE NE CWA BY THIS TIME. WEDNESDAY NIGHT...LOW LEVEL RIDGE AXIS PASSES OVER THE AREA AND LOW LEVELS CONTINUE TO DRY OUT SOMEWHAT...BUT MID-UPPER LEVEL MOISTURE AHEAD OF THE NEXT SHORTWAVE TROUGH WILL APPROACH OVERNIGHT. SO BETWEEN TRAPPED CLOUD COVER BENEATH THE INVERSION AND INCOMING MID-HIGH DECK...BELIEVE WEDNESDAY NIGHT WILL REMAIN ON THE CLOUDY SIDE. LOWS SHOULDNT FALL TO FAR HOWEVER...AND WILL GO WITH LOW TO MID 20S. THURSDAY THROUGH MONDAY...LOW AMPLITUDE FLOW OVER THE FIRST HALF OF THE WEEK BECOMES MORE BUCKLED AS A SERIES OF STRONG SHORTWAVES MOVES ACROSS THE EASTERN PACIFIC AND ACROSS WESTERN NORTH AMERICA. THE LEADING MEDIUM RANGE MODELS ALL SUPPORT THIS SCENARIO...BUT DETAIL UNCERTAINTIES BECOME APPARENT STARTING THURSDAY WITH THE SECOND OF THESE IMPINGING WAVES. THIS SECOND WAVE LOOKS TO BE THE APPETIZER TO A POTENTIAL STRONG STORM FOR THE WEEKEND. HPC ARGUES FOR THE USE OF THE 00Z ECMWF EXCLUSIVELY...AND GIVEN ITS RECENT STRONG PERFORMANCE AND GENERAL HIGHER VERIFICATION SCORES...TOUGH TO ARGUE AGAINST THIS STRATEGY. THURSDAY...SHORTWAVE CURRENTLY OVER THE EASTERN PACIFIC WILL TARGET THE CENTRAL MISSISSIPPI AND OHIO RIVER VALLEYS. BEST FORCING WILL LIE AHEAD OF THIS WAVE WELL TO THE SOUTH...BUT A WEAK BAROCLINIC ZONE NORTH OF THE SURFACE LOW WILL TRY TO LIFT NORTH ACROSS LOWER MICHIGAN MORESO INTO THURSDAY NIGHT. LIFT OVER THE WARM FRONT APPEARS TO WEAKEN AS THE SHORTWAVE SHEARS OUT AND FORCING WANES A BIT...SO THURSDAY STILL LOOKS DRY...WHILE A LOW CHANCE FOR SNOW WILL BE PRESENT THURSDAY NIGHT...PRIMARILY ACROSS THE SOUTHERN CWA. PLENTY OF CLOUD COVER WILL KEEP HIGHS IN THE LOW 30S AND LOWS IN THE 20S. FRIDAY...SHEARED OUT SHORTWAVE MOVES TO THE MID-ATLANTIC STATES WHILE SHORTWAVE RIDGING RETURNS. THERE MAYBE SOME LINGERING LIGHT PRECIP IN THE MORNING BEFORE ENERGY FROM THE SURFACE LOW OVER THE SOUTHERN GREAT LAKES IS TRANSFERRED TO A DEVELOPING COASTAL LOW. WE HAVE TO SEE IF AND HOW QUICK THIS LOW LEVEL MOISTURE DEPARTS SINCE THERE DOES NOT APPEAR TO BE ANY DRY LOW LEVEL AIR MOVING INTO THE GREAT LAKES. WILL KEEP SKIES ON THE CLOUDY SIDE BUT PRECIP OUT OF THE FORECAST SINCE ANY PRECIP LOOKS TO BE VERY LIGHT AND PERHAPS DRIZZLY. HIGHS ONCE AGAIN IN THE LOW 30S WITH LOWS IN THE 20S. SATURDAY THROUGH MONDAY...ALL ATTENTION THEN TURNS TO THE SW AS A POTENT WAVE EMERGES FROM THE ROCKIES AND INTO THE PLAINS ON SATURDAY. WARM AIR WILL SURGE NORTH AHEAD OF THE LOW ACROSS THE GREAT LAKES. HOW MUCH WARM AIR DEPENDS ALOT ON THE SPEED OF THE SYSTEM...THE SLOWER OF WHICH WOULD LIKELY TRANSFER MORE WARM AIR NORTH...AND AIRMASS MODIFICATION FROM DEEP SNOW PACK ACROSS THE SOUTHERN GREAT LAKES. THIS WARM AIR WILL ALSO HAVE AN IMPACT ON PRECIP TYPE AS WELL...SO WILL KEEP THINGS RATHER GENERAL ON SATURDAY WITH A RAIN/SNOW MIX UP TO THE STRAITS UNTIL DETAILS CAN BE RESOLVED. THE SURFACE LOW IS THEN PROJECTED TO MOVE ACROSS THE CENTRAL GREAT LAKES SATURDAY NIGHT AND INTO SUNDAY WITH THE COLD FRONTAL PASSAGE SOMETIME ON SUNDAY. AIR DOES NOT LOOK ALL THAT COLD BEHIND THIS SYSTEM SINCE MUCH OF THE ARCTIC AIR IS BOTTLED WELL TO THE NORTH OVER NORTHERN CANADA. DEEP CYCLONIC FLOW...PLENTY OF LOW-MID LEVEL MOISTURE...AND PROBABLY COLD ENOUGH 850MB TEMPS CALLS FOR LAKE EFFECT PRECIP SUNDAY AND INTO MONDAY. MPC && .AVIATION... /ISSUED 1242 PM EST MON DEC 17 2007/ A WARM FRONT WILL MOVE ACROSS NORTHERN MICHIGAN THIS AFTERNOON...WITH A MIX OF VFR/MVFR CONDITIONS EXPECTED. MVFR CONDITIONS WILL BE MOST DOMINANT ALONG THE LAKE MICHIGAN SHORELINE NEAR KTVC AND KPLN THIS AFTERNOON WITH SOME VERY WEAK LOW LEVEL INSTABILITY KEEPING SOME LAKE CLOUDS AROUND. INLAND AREAS WILL SEE SOME BREAKS IN THE CLOUD COVER THIS AFTERNOON AS WE MIX OUT THE LOW LEVEL INVERSION. HOWEVER...THESE CLOUDS WILL FILL BACK IN TONIGHT AS WARM ADVECTION OVER THE SNOWPACK CONTINUES IN THE WAKE OF THE WARM FRONT. THUS...MAINLY MVFR CONDITIONS WILL BE SEEN TONIGHT AND EARLY TOMORROW MORNING. KAS && .APX WATCHES/WARNINGS/ADVISORIES...NONE. && $$ mi AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE MARQUETTE MI 1243 AM EST MON DEC 17 2007 .UPDATE... UPDATE TO PREVIOUS UPDATE...CLOUDS OVER NORTHERN WI INTO UPPER MI ARE BEGINNING TO DISSIPATE...EXCLUDING THOSE COMING OFF LAKE MICHIGAN INTO DELTA AND SCHOOLCRAFT COUNTIES. APPEARS THAT THE WEAK DECEMBER SUN WAS STILL ABLE TO PROVIDE ENOUGH SOLAR RADIATION TO START MIXING OUT THE STRONG LOW LEVEL INVERSION NOTED ON AREA TAMDAR SOUNDINGS. WILL BE UPDATING THE GRIDS TO GO MORE OPTIMISTIC ON THE CLOUD COVER...AT LEAST FOR THIS AFTERNOON INTO THIS EVENING. HOWEVER...NOCTURNAL COOLING COMBINED WITH RELATIVELY MOIST DEWPOINTS IN THE MID TEENS SHOULD SUPPORT REFORMING OF THE LOW CLOUDS AND MIST LATE THIS EVENING INTO THE OVERNIGHT PERIOD. HIGH CONFIDENCE OF LOW CLOUDS AND FREEZING DRIZZLE REMAINS OVER THE KEWEENAW PENINSULA TONIGHT WITH A LOT OF LOW CLOUDS PRESENT ON WESTERN LAKE SUPERIOR. PREVIOUS UPDATE ISSUED AT 1102 AM EST... VERY TRICKY FORECAST FOR THE REST OF TODAY INTO TONIGHT. WATER VAPOR IMAGERY SHOWS AN UPPER LOW MOVING INTO NW ONTARIO...WHICH MODELS PROG TO NOW MOVE EVEN FARTHER NORTH...ACROSS VERY FAR NORTHERN LAKE SUPERIOR OR IN ONTARIO. U.S. AND CANADIAN RADARS DEPICT ALL OF THE PCPN ASSOCIATED WITH THE UPPER LOW NORTH OF THE MN/ONTARIO BORDER...LIKELY DUE TO DRY AIR IN THE MID-LEVELS DEPICTED ON THE 12Z INL AND GRB SOUNDINGS. THIS UPPER LOW IS REFLECTED AT THE SURFACE BY A 1009MB LOW NEAR THE INTERSECTION OF MANITOBA/ONTARIO AND MN...WITH A WARM FRONT EXTENDING SE THROUGH THE KEWEENAW AND INTO THE EASTERN U.P.. SOUTH OF THIS WARM FRONT...LOW CLOUDS...MIST AND LIGHT SNOW HAVE BEEN ADVECTING NORTHEASTWARD INTO THE CWA FROM WI ON SW WINDS. HOWEVER...THE CLOUDS HAVE BEEN SLOW TO MOVE INTO DOWNSLOPE AREAS... SUCH AS ONTONAGON...BARAGA AND MARQUETTE...WHICH COMBINED WITH THE 12Z GRB SOUNDING SHOW THE SHALLOW NATURE OF THE CLOUDS. THE RUC MODELS HAVE HAD A PRETTY GOOD HANDLE ON THESE LOW CLOUDS ON THEIR 950MB RH FIELD...AND UPDATED THE CLOUD FORECAST FOR TODAY INTO TONIGHT BASED ON THIS FIELD. BASICALLY...THE LOW CLOUDS SHOULD ENCOMPASS MUCH OF THE U.P. BY 00Z TONIGHT...WITH DOWNSLOPE AREAS TAKING THE LONGEST TO SEE THE CLOUDS. IN ADDITION...ADDED SOME FLURRIES SINCE SITES SUCH AS LNL...IMT AND EGV HAVE REPORTED THEM...WHICH MAKES SENSE GIVEN THAT THE LOW CLOUD DECK IS WITHIN THE -10 TO -12C ZONE. DEBATED ABOUT ADDING SOME PATCHY FOG TOO...BUT WITH VISIBILITIES GENERALLY ABOVE 2 SM...FIGURE THINGS WILL BE OKAY. REGARDING SYNOPTIC PCPN CHANCES WITH THE UPPER LOW...HAVE SHIFTED THESE NORTH OF UPPER MI TODAY GIVEN THE FARTHER NORTH TRACK. HOWEVER...AS THE COLD FRONT ASSOCIATED WITH THE SURFACE LOW MOVES IN TONIGHT...IT COULD END UP PICKING UP SOME LAKE MOISTURE AND GENERATING LAKE ENHANCED CLOUDS...SINCE LAPSE RATES FROM THE LAKE SURFACE TO 900MB ARE PROGGED TO BECOME MORE THAN MOIST ADIABATIC. THIS PCPN WOULD MOVE INTO THE KEWEENAW THIS EVENING AND REMAIN NEARLY STATIONARY THROUGH THE NIGHT. PCPN TYPE IS OF CONCERN AS THE TOP OF THE INVERSION MAY ONLY REACH -8C AT BEST. THUS...HAVE DECIDED TO INCLUDE A MENTION OF FZDZ FOR THE KEWEENAW TOO. && .DISCUSSION... MAIN FCST CONCERNS ARE LIGHT SNOW CHANCES TODAY THROUGH WED ALONG WITH FZDZ POTENTIAL TUE INTO EARLY WED. WV IMAGERY AND RUC ANALYSIS INDICATED A MID/UPPER LEVEL TROUGH ALONG THE WEST COAST...A RIDGE OVER THE ROCKIES...AND A BROAD TROUGH OVER THE EAST HALF OF THE CONUS. A COMPACT SHORTWAVE/VORT WAS LOCATED OVER SRN MANITOBA WITH A DOWNSTREAM SHORTWAVE RIDGE INTO THE WRN GREAT LAKES. AT THE SFC...LOW PRES WAS LOCATED SE MANITOBA WITH A RIDGE FROM WRN ONTARIO INTO WI WHILE THE EAST COAST STORM (971 MB LOW) WAS LIFTING THROUGH THE CANADIAN MARITIMES. TROUGHING ALSO EXTENDED THROUGH THE UPPER GREAT LAKES LEAVING NW FLOW THROUGH ERN LAKE SUPERIOR AND WEAK SW WINDS OVER THE WEST PORTION OF THE LAKE. 850 MB TEMPS TO AROUND -10C SUPPORTED WEAK MULTIPLE WIND PARALLEL LES BANDS ALIGNED WITH 310-320 CBL FLOW INTO THE ERN CWA THAT CONTINUED TO SLOWLY DIMINISH. UPSTREAM 2-4SM VSBY WITH LIGHT SNOW WAS REPORTED OVER SRN MANITOBA INTO WRN ONTARIO...MAINLY ALONG THE MID LEVEL VORT TRACK. TODAY AND TONIGHT...THE LES OVER THE NE PORTION OF THE CWA WILL END AS WINDS BACK WSW BY MID TO LATE MORNING AHEAD OF THE APPROACHING LOW. ADDITIONAL SNOWFALL SHOULD AMOUNT TO LESS THAN AN INCH. THE BEST CHANCE FOR SNOW WITH THE MANITOBA SHORTWAVE WILL BE ALONG THE PATH OF THE MID LEVEL VORT WITH THE AREA OF MODERATE MID/UPPER LEVEL QVECTOR CONV AND STEEPER MID LEVEL LAPSE RATES. THIS WILL KEEP MOST OF THE SNOW NORTH FROM LATE MORNING INTO THE EVENING NORTH OF UPPER MI. ONLY CHANCE POPS INCLUDED VCNTY KCMX/KP59/KERY WITH SLIGHT CHANCE TO THE SOUTH AND NO PCPN MENTIONED CLOSER TO THE WI BORDER. TUESDAY AND TUESDAY NIGHT...MODELS HAVE COME INTO BETTER AGREEMENT WITH THE POSITION/STRENGTH OF THE PAC NW TROUGH AS IT MOVES INTO THE REGION. HOWEVER...GIVEN THE WELL-DEFINED LOOK OF THIS FEATURE FROM THE WV LOOP AND INITIALIZATION PROBLEMS WITH THE 00Z NAM/GFS NOTED BY HPC...THE SLIGHTLY STRONGER/DEEPER 00Z CANADIAN REG GEM...SUPPORTED BY THE ECMWF...WAS PREFERRED. AN INFLUX OF LOW LEVEL MOISTURE WITH RELATIVELY DRY AIR AOB -10C MAY ALSO RESULT IN SOME PATCHY FZDZ ALONG WITH SOME LIGHT SNOW BY MID TO LATE AFTERNOON. AGAIN THE MID LEVEL LOW TRACK WILL BRING BEST SNOW CHANCES MAINLY NORTH OF UPPER MI WITH THE POPS TAPERED FROM NORTH TO SOUTH. EXPECT DEEP MOISTURE AOA -10C OVER ALL BUT THE SOUTH BY TUE NIGHT...REDUCING CHANCES FOR FZDZ. WEDNESDAY...WITH FCST SOUNDINGS SHOWING MOISTURE RECEDING TO AROUND -8C...NRLY FLOW IN THE WAKE OF THE LOW COMBINED WITH ABUNDANT LEFTOVER LOW LEVEL MOISTURE MAY RESULT IN SOME PATCHY LIGHT SNOW OR FREEZING DRIZZLE OVER THE WEST HALF OF UPPER MI IN THE MORNING...ESPECIALLY WHERE WINDS UPSLOPE INTO HIGHER TERRAIN. && .AVIATION (FOR THE 18Z TAF ISSUANCE)... TAF FORECASTS ARE TROUBLESOME TODAY. LOW CLOUDS AND MIST THAT WERE OVER NORTHERN WISCONSIN AND HEADING UP INTO UPPER MICHIGAN HAVE BEEN DISSIPATING OVER THE PAST HOUR...AND PROBABLY WILL CONTINUE TO DISSIPATE THROUGH THIS AFTERNOON WITH EXTRA HEATING. SO ALTHOUGH A BKN IFR OR LOW MVFR DECK MAY COME INTO SAW SHORTLY SINCE THE CLOUDS ARE ON THE DOORSTEP...HAVE ONLY INCLUDED A TEMPO GROUP UNTIL 20Z. AS NIGHTTIME COOLING SETS IN...THESE CLOUDS AND MIST SHOULD REAPPEAR...PROBABLY NEAR OR JUST AFTER MIDNIGHT. AT CMX...SOME LOW IFR CLOUDS ARE CURRENTLY OVER THE AIRPORT...BUT ARE MOVING NE. THUS THESE CLOUDS SHOULD SCATTER/CLEAR OUT IN THE NEXT HOUR OR TWO. HOWEVER...LURKING OFF ON WESTERN LAKE SUPERIOR IS EXTENSIVE LOW CLOUDS WITH LIFR CIGS. AS A COLD FRONT CURRENTLY UP IN NW MN APPROACHES THE KEWEENAW THIS EVENING...THESE CLOUDS WILL MOVE BACK IN...WITH THE POSSIBILITY FOR SOME FREEZING DRIZZLE OR LIGHT SNOW AS LAKE EFFECT ENHANCES THE CLOUDS. EXPECT LOW CLOUDS TO PERSIST AT BOTH TAF SITES INTO TUE...WITH LIFR CEILINGS...IFR VSBYS AND FREEZING DRIZZLE/LIGHT SNOW. && .MARINE (FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)... HIGH PRESSURE OF 30.1 INCHES OVER CENTRAL AND EASTERN LAKE SUPERIOR WILL GIVE WAY TO A 29.9 INCH LOW PRESSURE SYSTEM FROM CENTRAL MANITOBA LATE THIS AFTERNOON. THIS LOW WILL EXIT TO THE EAST AND WEAKEN SIGNIFICANTLY. IT WILL BE REPLACED BY A SLIGHTLY STRONGER LOW OF 29.8 INCHES FROM CENTRAL MINNESOTA TUESDAY AFTERNOON... CROSSING UPPER MICHIGAN TUESDAY NIGHT...AND MAKING IT TO THE EASTERN GREAT LAKES BY WEDNESDAY EVENING. WINDS ARE EXPECTED TO REMAIN BELOW 30 KNOTS WITH THESE TWO SYSTEMS...AND PROBABLY EVEN AT OR BELOW 25 KNOTS. HIGH PRESSURE OF 30.0 INCHES WILL THEN OVERTAKE THE AREA. A 29.7 INCH LOW PRESSURE SYSTEM DEVELOPING OVER THE SOUTHERN PLAINS THURSDAY MORNING WILL MOVE OVER THE OHIO RIVER VALLEY ON FRIDAY. ALSO ON FRIDAY...ANOTHER LOW PRESSURE SYSTEM OF 29.6 INCHES WILL BE SLIDING OUR WAY FROM NORTH DAKOTA AND SOUTHERN MANITOBA. WINDS LESS THAN 25 KNOTS ARE EXPECTED THURSDAY AND FRIDAY. LOOKING MORE INTO THE FUTURE...IT LOOKS LIKE THE FIRST CHANCE OF GALES ON LAKE SUPERIOR WILL BE SATURDAY NIGHT AND SUNDAY...DEPENDING ON THE TRACK AND STRENGTH OF THE NEXT SIGNIFICANT SURFACE LOW. && .MQT WATCHES/WARNINGS/ADVISORIES...NONE. && $$ UPDATE...AJ DISCUSSION...JLB AVIATION...AJ MARINE...KF mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GAYLORD MI 1242 PM EST MON DEC 17 2007 .AVIATION...A WARM FRONT WILL MOVE ACROSS NORTHERN MICHIGAN THIS AFTERNOON...WITH A MIX OF VFR/MVFR CONDITIONS EXPECTED. MVFR CONDITIONS WILL BE MOST DOMINANT ALONG THE LAKE MICHIGAN SHORELINE NEAR KTVC AND KPLN THIS AFTERNOON WITH SOME VERY WEAK LOW LEVEL INSTABILITY KEEPING SOME LAKE CLOUDS AROUND. INLAND AREAS WILL SEE SOME BREAKS IN THE CLOUD COVER THIS AFTERNOON AS WE MIX OUT THE LOW LEVEL INVERSION. HOWEVER...THESE CLOUDS WILL FILL BACK IN TONIGHT AS WARM ADVECTION OVER THE SNOWPACK CONTINUES IN THE WAKE OF THE WARM FRONT. THUS...MAINLY MVFR CONDITIONS WILL BE SEEN TONIGHT AND EARLY TOMORROW MORNING. KAS && .UPDATE... /ISSUED 1030 AM EST MON DEC 17 2007/ RUC/SURFACE/SATELLITE/SURFACE ANALYSIS THIS MORNING REVEALS SHORTWAVE RIDGING WORKING ACROSS THE WESTERN GREAT LAKES REGION. WITH THE RIDGE AXIS SLIDING THROUGH THE AREA...SFC WINDS HAVE BEEN BACKING AROUND TO THE WEST THIS MORNING...EVENTUALLY ENDING UP AT SOUTHWEST LATER THIS AFTERNOON. WARM FRONT IS NOT VERY EVIDENT WITH REGARDS TO SURFACE TEMPERATURES. HOWEVER...LOOKING AT WINDS AND LOW CLOUD DEVELOPMENT...APPEARS THE MAIN WARM FRONT BOUNDARY IS LOCATED FROM CENTRAL UPPER MICHIGAN...SOUTHWARD THROUGH THE LONG AXIS OF LAKE MICHIGAN AND INTO SOUTHEAST LOWER MICHIGAN. CEILINGS AROUND KFKS AND KMBL ARE BEGINNING TO FALL TO AROUND 2KFT SUGGESTING THE FRONT IS STARTING TO PUSH ONSHORE INTO NORTHERN LOWER MICHIGAN. ALSO EVIDENT IS THE DWINDLING OVER LAKE INSTABILITY. RADAR REFLECTIVITIES HAVE SHOWN A DECREASING TREND OVER THE PAST FEW HOURS. LATEST 850MB RUC TEMPERATURE ANALYSIS REVEALS -4C 850MB AIR IMMEDIATELY BEHIND THE SURFACE WARM FRONT IN EASTERN WISCONSIN. WITH LAKE MICHIGAN TEMPERATURES CURRENTLY RUNNING AROUND +7C...DELTA TS WILL FALL TO LESS THAN THE IDEAL 13C BY EARLY THIS AFTERNOON AS THE WARMER AIR UPSTREAM ADVECTS INTO THE AREA. THUS...THE ONGOING DIMINISHING TREND TO THE LAKE EFFECT SNOW SHOWERS WILL CONTINUE THROUGH THE REMAINDER OF THE MORNING AND EARLY AFTERNOON. THERE IS STILL PLENTY OF LOW LEVEL MOISTURE TRAPPED BELOW A 900MB INVERSION AS SHOWN BY LOW CLOUD COVERAGE ACROSS WISCONSIN. THUS...WOULD EXPECT THIS LOW CLOUD COVERAGE TO EXPAND EAST AND NORTH TODAY...OVERTAKING MOST OF NORTHERN MICHIGAN BY LATE THIS AFTERNOON. THE MOISTURE WILL REMAIN SHALLOW ENOUGH TO PREVENT ANY DRIZZLE OR FLURRIES FROM DEVELOPING THIS AFTERNOON. NO CHANGES PLANNED TO SFC TEMPERATURES...AS INCREASING CLOUDS WILL HELP KEEP TEMPERATURES FROM GETTING OUT OF THE UPPER 20S THIS AFTERNOON. THE EXCEPTION WILL BE ALONG THE LAKE MICHIGAN SHORELINE...WHERE ONSHORE WINDS WITH THE HELP OF STILL SOMEWHAT WARM LAKE WATERS WILL ALLOW LOCATIONS TO CLIMB INTO THE LOWER 30S. KAS && .PREV DISCUSSION... /ISSUED 444 AM EST MON DEC 17 2007/ ON THE LATEST SURFACE WEATHER MAP...973 MB LOW PRESSURE WAS OVER UPSTATE MAINE...1030 MB HIGH PRESSURE OVER EAST TEXAS AND 1008 MB LOW PRESSURE ACROSS SOUTHERN MANITOBA. APX RADAR CONTINUES TO SHOW A BROAD AREA OF NORTHWEST FLOW LAKE EFFECT MOVING OFF OF LAKES SUPERIOR AND MICHIGAN. SURFACE OBSERVATIONS INDICATE THAT THIS ACTIVITY IS ON THE LIGHT TO OCCASIONALLY MODERATE SIDE (LOWEST VSBYS OF 1 1/2 TO 3 MILES). THE MAIN SHORT TERM FORECAST CONCERNS REVOLVE AROUND THE TIMING OF THE ENDING OF LAKE EFFECT TODAY...THEN POPS WITH WARM ADVECTION/CLIPPER SYSTEM LATER TODAY INTO TONIGHT. OTHER CONCERNS INCLUDE POPS THIS EVENING AND POPS AND POTENTIAL FOR FREEZING DRIZZLE TUESDAY AFTERNOON INTO WEDNESDAY. TODAY...DESPITE INCREASING RIDGING/ANTICYCLONIC FLOW ALOFT ALONG WITH DRIER AIR MOVING IN (MODELS LOWER MEAN 900-700 MB RH TO ABOUT 40 PERCENT AT 12Z)...THE LAKE EFFECT MACHINE CONTINUES TO CHURN ON AS IS THE CASE MORE TIMES THAN NOT. THEREFORE WILL LINGER POPS OVER THE NEXT SEVERAL HOURS. AS WARMER TEMPERATURES ADVECT IN ALOFT (850 MB TEMPS INCREASE FROM BETWEEN -10 AND -12 AT 12Z TO -6 AND -9 AT 18Z TO -2 AND -6 AT 00Z)...OVER LAKE INSTABILITY WILL SLOWLY DECREASE WHICH SHOULD END LAKE EFFECT SOMETIME THIS AFTERNOON. SO WILL CONTINUE WITH NUMEROUS SNOW SHOWERS ACROSS FAVORED AREAS THIS MORNING AND EARLY THIS AFTERNOON WITH ACCUMULATIONS OF AN INCH OR TWO. THE FLOW BACKS FROM NORTHWEST EARLY THIS MORNING INTO THE WEST SOUTHWEST THIS AFTERNOON SO WILL ORIENTATE POPS TO ACCOUNT FOR THIS AS WELL. IN ADDITION...WARM ADVECTION/A BIT OF ISENTROPIC ASCENT (I280) IN COMBINATION WITH A WEAK CLIPPER MOVING ACROSS SOUTH CENTRAL CANADA WILL BRING A CHANCE OF LIGHT SNOW TO EASTERN UPPER LATER THIS AFTERNOON. HIGHS TODAY IN THE MIDDLE TO UPPER 20S. TONIGHT...CLIPPER CONTINUES TO MOVE ACROSS FAR SOUTHERN CANADA GRAZING EASTERN UPPER THIS EVENING LEADING TO A CHANCE OF LIGHT SNOW ACROSS FAR NORTHERN ZONES. MODELS INDICATE THAT THERE IS A WEAK AREA OF DIV-Q AND A MARGINAL AMOUNT OF MOISTURE (MEAN 1000-500 MB RH 60 TO 70 PERCENT) ASSOCIATED WITH THIS SYSTEM. OTHERWISE...OVER LAKE INSTABILITY WILL CONTINUE TO WANE AS 850 MB TEMPERATURES SETTLE IN BETWEEN -2 AND -4 C. LOWS IN THE UPPER TEENS TO LOWER 20S. TUESDAY...NOT A LOT GOING ON TO START THE DAY AS A SHORT WAVE RIDGE MOVES ACROSS THE AREA. ANOTHER CLIPPER ALONG WITH AN ASSOCIATED SURFACE WARM FRONT THEN APPROACHES FROM THE NORTHWEST LATE IN THE DAY. THIS WILL LEAD TO A CHANCE FOR LIGHT SNOW OR EVEN SOME FREEZING DRIZZLE (MODEL CROSS SECTIONS/SOUNDINGS SHOW LOW LEVEL MOISTURE ONLY UP TO ABOUT -8C) ACROSS NORTHWESTERN ZONES. MILDER WITH HIGHS IN THE LOWER AND MIDDLE 30S. TUESDAY NIGHT INTO WEDNESDAY...CLIPPER TAKES ITS TIME MOVING ACROSS THE REGION. MOISTURE IS SHOWN TO REMAIN SHALLOW IN THE EVENING LEADING TO A CONTINUED CHANCE OF FREEZING DRIZZLE THEN DEEP ENOUGH AFTER MIDNIGHT INTO WEDNESDAY TO LEAD TO A CHANCE OF LIGHT SNOW. LOWS TUESDAY NIGHT IN THE MIDDLE AND UPPER 20S WITH HIGHS ON WEDNESDAY RANGING FROM AROUND 30 TO THE MIDDLE 30S. THURSDAY...MODELS ARE IN GOOD AGREEMENT THAT AN AREA OF LOW PRESSURE MOVES BY TO OUR SOUTH. WILL ADD IN LOW CHANCE POPS INTO FAR SOUTHERN ZONES TO LINE UP WITH SURROUNDING OFFICES. HIGHS IN THE LOWER AND MIDDLE 30S. NO CHANGES MADE TO THE REMAINDER OF THE FORECAST. POTENTIAL MESS NEXT WEEKEND THOUGH AS THE EXTENDED MODELS BRING A DEEP AREA OF LOW PRESSURE ACROSS THE WESTERN GREAT LAKES (WITH POSSIBLE PRECIPITATION TYPE ISSUES). SULLIVAN && .APX WATCHES/WARNINGS/ADVISORIES...NONE. && $$ mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NORMAN OK 1056 AM CST MON DEC 17 2007 .DISCUSSION... TEMPERATURES IN THE NORTHERN OKLAHOMA SNOWFIELD ARE RISING SLOWER THAN PREVIOUSLY FORECAST. LAPS ANALYSIS WAS INCORPORATED AND THE RUC FOR NORTHERN OKLAHOMA ONLY SINCE TEMPERATURE ANOMALIES REMAIN IN THE RUC NEAR OKLAHOMA CITY AND TULSA. CLOUD FORECAST WAS ADJUSTED TO REFLECT THE NEARLY CLEAR SKIES AND THE APPROACHING MID AND HIGH CLOUD FROM THE SOUTHWEST. && .PRELIMINARY POINT TEMPS/POPS... OKLAHOMA CITY OK 49 34 54 31 / 0 0 0 0 HOBART OK 53 32 56 31 / 0 0 0 0 WICHITA FALLS TX 55 37 62 35 / 0 0 0 0 GAGE OK 52 24 54 25 / 0 0 0 0 PONCA CITY OK 44 29 49 29 / 0 0 0 0 DURANT OK 55 40 58 39 / 0 0 0 0 && .OUN WATCHES/WARNINGS/ADVISORIES... OK...NONE. TX...NONE. && $$ 99/99 ok