SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION...UPDATE NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA 947 AM PST SAT NOV 22 2008 UPDATED AVIATION SECTION .SHORT TERM (TODAY-MONDAY)...AS THE CIRRUS DECK THINS THIS MORNING...SOME STRATUS AND FOG IS TRYING TO BUILD OVER THE CENTRAL COAST AND SAN LUIS OBISPO COUNTY VALLEYS. NAM BUFR DATA IS INDICATING A THIN LAYER MOISTURE AT KSMX AND KSBP THIS MORNING. WITH HIGH LEVEL MOISTURE CLEARING THIS MORNING ALONG THE CENTRAL COAST...PATCHY LOW CLOUDS AND DENSE FOG WORDING WILL BE ADDED TO THE CENTRAL COAST AND SAN LUIS OBISPO COUNTY VALLEYS. 13-KM RUC AND NAM-WRF BOUNDARY LAYER AND 975 MB RELATIVE HUMIDITIES INDICATE SOME MARINE LAYER PUSH INTO THE LOS ANGELES COUNTY COAST THIS MORNING. KLSI INDICATED SOME DENSE FOG SOUTH OF THE AREA EARLY THIS MORNING...AND WITH TEMPERATURE AND DEW POINT SPREADS NARROWING AT KLGB...LOW CLOUDS AND PATCHY DENSE FOG WILL BE ADDED TO THE LOS ANGELES COUNTY SOUTH COAST THIS MORNING. MARINE LAYER SHOULD BECOME MORE DEVELOPED TONIGHT AS SOUTHEASTERLY LOW LEVEL FLOW DEVELOPS. AREAS ESPECIALLY SOUTH OF POINT CONCEPTION SHOULD SEE A RETURN OF THE MARINE LAYER...AND AREAS OF LOW CLOUDS AND FOG SHOULD PUSH INTO SOME OF THE LOWER VALLEY AREAS IN THE LOS ANGELES AND VENTURA COUNTIES. NAM BUFR DATA INCREASE MARINE INVERSION OVER KLAX AND KLGB TO NEAR 1200 FEET...AND 600 FEET OVER KSBA. COVERAGE SHOULD BE LIMITED NORTH OF POINT CONCEPTION...BUT WITH SOME INDICATIONS OF LOW CLOUDS AND FOG DEVELOPING THIS MORNING...IT MAY NOT BE A BAD CALL FOR FURTHER PACKAGES TO ADDRESS THIS ISSUE. SOME CONCERN IS ALSO PRESENT FOR THE SAN FERNANDO VALLEY...ESPECIALLY WITH 06Z NAM BUFR DATA INDICATING A STRONGER PUSH TONIGHT INTO KBUR AND KVNY. INITIALLY...THIS WAS WEAKER BUT LEFT A CHANCE...BUT WITH 06Z NAM- WRF AND NAM BUFR DATA INDICATING A BETTER SURGE PATCHY LOW CLOUDS AND FOG WILL BE ADDED TO THE PACKAGE FOR TONIGHT. WITH MARINE LAYER DEEPENING TEMPERATURES WERE TWEAKED DOWN SLIGHTLY FOR THE SUNDAY...AND COOLING TREND SHOULD PERSIST INTO MONDAY. MARINE COULD DEEPEN FURTHER ON SUNDAY NIGHT AND INTO MONDAY...ESPECIALLY IF THE NAM-WRF AND GFS SOLUTIONS ARE CORRECT. 06Z NAM-WRF AND GFS SOLUTIONS SPREAD PRECIPITATION INTO THE AREA AS SOON AS MONDAY NIGHT AND TUESDAY. NAM-WRF SEEMS TO BE MOST AGGRESSIVE WITH THE PRECIPITATION WITH A DECENT MOIST 850 MB AND 700 MB WARM AIR ADVECTIVE PATTERN SETTING UP BENEATH AND 500 MB JET AND 500 MB COLD AIR ADVECTIVE PATTERN. MARINE LAYER DRIZZLE OR POSSIBLY EVEN LIGHT SHOWERS COULD OCCUR WITH THIS PATTERN. WITH THE MODEL SOLUTIONS SPEEDING UP THE SYSTEM...FUTURE SHIFTS WILL HAVE TO LIKELY INCREASE POPS FOR THE MONDAY NIGHT PERIOD. CURRENT PACKAGE TAKE A MORE OF THE ECMWF SOLUTION INTO ACCOUNT...BUT LEANS TOWARDS THE GFS SOLUTION. .LONG TERM (TUESDAY-SATURDAY)...ALL MODELS AGREE ON PRECIPITATION FOR MONDAY THROUGH WEDNESDAY NIGHT...AND POPS HAVE BEEN BUMPED UP AND SKY COVER INCREASED FOR THIS TIME PERIOD. FUTURE SHIFTS WILL LIKELY HAVE TO BUMP UP POPS SHOULD CONFIDENCE CONTINUE TO GROW FOR THIS TIME PERIOD. AT THE CURRENT TIME...QPF AMOUNTS EXPECTED ARE FOR A THIRD OF AN INCH TO TWO THIRDS OF AN INCH OVER THE COASTAL AND VALLEY AREAS...AROUND AN INCH THE MOUNTAINS...AND A QUARTER INCH OR LESS IN THE DESERT. LOCALLY HIGHER AMOUNTS WILL LIKELY OCCUR ALONG SOUTH-FACING SLOPES. WITH TIMING PROBLEMS OCCURRING STILL...LOW CONFIDENCE SHOULD PLACED IN THE EXACT PERIODS OF PRECIPITATION. HIGH CONFIDENCE EXISTS THAT A SOME POINT AREAWIDE PRECIPITATION WILL OCCUR AT SOME POINT DURING THE MONDAY NIGHT THROUGH WEDNESDAY NIGHT PERIOD. FROM WEDNESDAY NIGHT ON...ALL MODELS SEEM TO BE TRENDING THE CHANCES FOR PRECIPITATION DOWNWARD WITH THROUGH AXIS PASSING BY THE AREA AS SOON AS WEDNESDAY AFTERNOON OR AS LATE AS WEDNESDAY EVENING. IT IS DURING THIS PERIOD...FROM WEDNESDAY NIGHT THROUGH THURSDAY NIGHT THAT WIND ISSUES COULD DEVELOP OVER THE AREA ESPECIALLY FOR SOUTHERN SANTA BARBARA COUNTY AND THROUGH I-5 CORRIDOR. MODELS VARY FROM DRY TO WET DEPENDING ON MODEL CHOICE FOR LATE WEEK. GFS OPERATIONAL SOLUTIONS SEEMS TO THE WETTEST...WITH THE DGEX AND ECMWF PROGRESSIVELY DRIER. A MAJORITY OF THE GFS ENSEMBLE SOLUTIONS DOES PUSH THE TROUGH CENTER OVER THE POINT CONCEPTION. GEM MODEL SOLUTION INDICATE GOOD AGREEMENT WITH THE OPERATIONAL GFS AND TRENDS TOWARDS THE WET SIDE. WITH LITTLE CONFIDENCE BLANKET POPS WERE LEFT IN THE EXTENDED BUT A HUNCH MAY BE FOLLOW THE INDICATIONS OF THE GFS...DGEX...AND GEM RELATIVE TO THE ECMWF...THE OUTLIER SOLUTION AT THIS POINT. && .AVIATION...22/1800Z UPPER LEVEL LOW CENTERED SOUTH OF THE AREA WILL SHIFT NORTHEAST WHILE A TROUGH OF LOW PRESSURE OVER THE EASTERN PACIFIC DIVES SOUTHEAST. LIGHT UPPER LEVEL SOUTHWEST FLOW OVER THE AREA WILL PREVAIL. A WEAK PRESSURE GRADIENT OVER THE AREA WILL PERSIST. LOW LEVEL SOUTH FLOW WILL PERSIST NEAR SHORE AND LOW CLOUDS SOUTH OF THE AREA WILL DRIFT NORTH OVERNIGHT WITH TOPS AROUND 020. KLAX...THERE IS A CHANCE CIGS WILL DEVELOP INITIALLY BELOW 010 THEN ASCEND TO 015 WITH TOPS AROUND 020 OVERNIGHT THROUGH SUNDAY MORNING. KBUR...THERE IS A CHANCE CIGS WILL DEVELOP BELOW 010 LATE IN THE PERIOD. VIRTUALLY CERTAIN - 95-100% VERY LIKELY - 80-95% LIKELY - 60-80% CHANCE - 30-60% VERY UNLIKELY - 20% OR LESS && .LOX WATCHES/WARNINGS/ADVISORIES... SMALL CRAFT ADVISORY (SEE LAXMWWLOX). && $$ PUBLIC...HALL AVIATION...30 WWW.WEATHER.GOV/LOSANGELES ca SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA 416 AM PST SAT NOV 22 2008 .SHORT TERM (TODAY-MONDAY)...AS THE CIRRUS DECK THINS THIS MORNING...SOME STRATUS AND FOG IS TRYING TO BUILD OVER THE CENTRAL COAST AND SAN LUIS OBISPO COUNTY VALLEYS. NAM BUFR DATA IS INDICATING A THIN LAYER MOISTURE AT KSMX AND KSBP THIS MORNING. WITH HIGH LEVEL MOISTURE CLEARING THIS MORNING ALONG THE CENTRAL COAST...PATCHY LOW CLOUDS AND DENSE FOG WORDING WILL BE ADDED TO THE CENTRAL COAST AND SAN LUIS OBISPO COUNTY VALLEYS. 13-KM RUC AND NAM-WRF BOUNDARY LAYER AND 975 MB RELATIVE HUMIDITIES INDICATE SOME MARINE LAYER PUSH INTO THE LOS ANGELES COUNTY COAST THIS MORNING. KLSI INDICATED SOME DENSE FOG SOUTH OF THE AREA EARLY THIS MORNING...AND WITH TEMPERATURE AND DEW POINT SPREADS NARROWING AT KLGB...LOW CLOUDS AND PATCHY DENSE FOG WILL BE ADDED TO THE LOS ANGELES COUNTY SOUTH COAST THIS MORNING. MARINE LAYER SHOULD BECOME MORE DEVELOPED TONIGHT AS SOUTHEASTERLY LOW LEVEL FLOW DEVELOPS. AREAS ESPECIALLY SOUTH OF POINT CONCEPTION SHOULD SEE A RETURN OF THE MARINE LAYER...AND AREAS OF LOW CLOUDS AND FOG SHOULD PUSH INTO SOME OF THE LOWER VALLEY AREAS IN THE LOS ANGELES AND VENTURA COUNTIES. NAM BUFR DATA INCREASE MARINE INVERSION OVER KLAX AND KLGB TO NEAR 1200 FEET...AND 600 FEET OVER KSBA. COVERAGE SHOULD BE LIMITED NORTH OF POINT CONCEPTION...BUT WITH SOME INDICATIONS OF LOW CLOUDS AND FOG DEVELOPING THIS MORNING...IT MAY NOT BE A BAD CALL FOR FURTHER PACKAGES TO ADDRESS THIS ISSUE. SOME CONCERN IS ALSO PRESENT FOR THE SAN FERNANDO VALLEY...ESPECIALLY WITH 06Z NAM BUFR DATA INDICATING A STRONGER PUSH TONIGHT INTO KBUR AND KVNY. INITIALLY...THIS WAS WEAKER BUT LEFT A CHANCE...BUT WITH 06Z NAM- WRF AND NAM BUFR DATA INDICATING A BETTER SURGE PATCHY LOW CLOUDS AND FOG WILL BE ADDED TO THE PACKAGE FOR TONIGHT. WITH MARINE LAYER DEEPENING TEMPERATURES WERE TWEAKED DOWN SLIGHTLY FOR THE SUNDAY...AND COOLING TREND SHOULD PERSIST INTO MONDAY. MARINE COULD DEEPEN FURTHER ON SUNDAY NIGHT AND INTO MONDAY...ESPECIALLY IF THE NAM-WRF AND GFS SOLUTIONS ARE CORRECT. 06Z NAM-WRF AND GFS SOLUTIONS SPREAD PRECIPITATION INTO THE AREA AS SOON AS MONDAY NIGHT AND TUESDAY. NAM-WRF SEEMS TO BE MOST AGGRESSIVE WITH THE PRECIPITATION WITH A DECENT MOIST 850 MB AND 700 MB WARM AIR ADVECTIVE PATTERN SETTING UP BENEATH AND 500 MB JET AND 500 MB COLD AIR ADVECTIVE PATTERN. MARINE LAYER DRIZZLE OR POSSIBLY EVEN LIGHT SHOWERS COULD OCCUR WITH THIS PATTERN. WITH THE MODEL SOLUTIONS SPEEDING UP THE SYSTEM...FUTURE SHIFTS WILL HAVE TO LIKELY INCREASE POPS FOR THE MONDAY NIGHT PERIOD. CURRENT PACKAGE TAKE A MORE OF THE ECMWF SOLUTION INTO ACCOUNT...BUT LEANS TOWARDS THE GFS SOLUTION. .LONG TERM (TUESDAY-SATURDAY)...ALL MODELS AGREE ON PRECIPITATION FOR MONDAY THROUGH WEDNESDAY NIGHT...AND POPS HAVE BEEN BUMPED UP AND SKY COVER INCREASED FOR THIS TIME PERIOD. FUTURE SHIFTS WILL LIKELY HAVE TO BUMP UP POPS SHOULD CONFIDENCE CONTINUE TO GROW FOR THIS TIME PERIOD. AT THE CURRENT TIME...QPF AMOUNTS EXPECTED ARE FOR A THIRD OF AN INCH TO TWO THIRDS OF AN INCH OVER THE COASTAL AND VALLEY AREAS...AROUND AN INCH THE MOUNTAINS...AND A QUARTER INCH OR LESS IN THE DESERT. LOCALLY HIGHER AMOUNTS WILL LIKELY OCCUR ALONG SOUTH-FACING SLOPES. WITH TIMING PROBLEMS OCCURRING STILL...LOW CONFIDENCE SHOULD PLACED IN THE EXACT PERIODS OF PRECIPITATION. HIGH CONFIDENCE EXISTS THAT A SOME POINT AREAWIDE PRECIPITATION WILL OCCUR AT SOME POINT DURING THE MONDAY NIGHT THROUGH WEDNESDAY NIGHT PERIOD. FROM WEDNESDAY NIGHT ON...ALL MODELS SEEM TO BE TRENDING THE CHANCES FOR PRECIPITATION DOWNWARD WITH THROUGH AXIS PASSING BY THE AREA AS SOON AS WEDNESDAY AFTERNOON OR AS LATE AS WEDNESDAY EVENING. IT IS DURING THIS PERIOD...FROM WEDNESDAY NIGHT THROUGH THURSDAY NIGHT THAT WIND ISSUES COULD DEVELOP OVER THE AREA ESPECIALLY FOR SOUTHERN SANTA BARBARA COUNTY AND THROUGH I-5 CORRIDOR. MODELS VARY FROM DRY TO WET DEPENDING ON MODEL CHOICE FOR LATE WEEK. GFS OPERATIONAL SOLUTIONS SEEMS TO THE WETTEST...WITH THE DGEX AND ECMWF PROGRESSIVELY DRIER. A MAJORITY OF THE GFS ENSEMBLE SOLUTIONS DOES PUSH THE TROUGH CENTER OVER THE POINT CONCEPTION. GEM MODEL SOLUTION INDICATE GOOD AGREEMENT WITH THE OPERATIONAL GFS AND TRENDS TOWARDS THE WET SIDE. WITH LITTLE CONFIDENCE BLANKET POPS WERE LEFT IN THE EXTENDED BUT A HUNCH MAY BE FOLLOW THE INDICATIONS OF THE GFS...DGEX...AND GEM RELATIVE TO THE ECMWF...THE OUTLIER SOLUTION AT THIS POINT. && .AVIATION...22/1200Z...HIGH CONFIDENCE VFR CONDITIONS WILL PREVAIL AT MOST TAF SITES TODAY. THERE WILL BE SOME EARLY MORNING MVFR VSBYS ACROSS LA COUNTY COASTAL SITES EARLY...AND KPRB COULD HAVE SOME LIFR CIGS/VSBYS ONCE AGAIN THIS MORNING...BUT LESS CONFIDENCE THAN YESTERDAY. NO WIND ISSUES EXPECTED. KLAX...EXCEPT FOR MORNING MVFR VSBYS THROUGH 17Z...EXPECT VFR CONDS THROUGH AT LEAST THIS EVENING...THEN MODERATE CONFIDENCE FOR IFR/MVFR CIGS AFTER 07Z. NO WIND ISSUES. KBUR...EXPECT VFR CONDS TODAY THROUGH MOST OVERNIGHT HOURS...WITH JUST BELOW MODERATE CONFIDENCE FOR LIFR/IFR CONDS AFTER 10Z. NO WIND ISSUES. && .LOX WATCHES/WARNINGS/ADVISORIES... SMALL CRAFT ADVISORY (SEE LAXMWWLOX). && $$ PUBLIC...HALL AVIATION...KAPLAN WWW.WEATHER.GOV/LOSANGELES ca AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PUEBLO CO 308 PM MST SUN NOV 23 2008 .SHORT TERM... (TONIGHT AND MONDAY) ...SHORT TERM CONCERN REMAINS TEMPERATURES... CURRENT WATER VAPOR IMAGERY AND RUC UPPER AIR ANALYSIS INDICATING MODERATE WEST TO NORTHWEST FLOW ALOFT ACROSS THE REGION WITH WELL ADVERTISED MINOR EMBEDDED WAVE TRANSLATING ACROSS SOUTHERN WYOMING ATTM. AT THE SFC...ASSOCIATED BACKDOOR COLD FRONT/NORTHERLY SURGE HAS CLEARED THE SE PLAINS WITH BEST PRESSURE RISES BEING REALIZED ACROSS WESTERN KANSAS BORDER ATTM. AS ANTICIPATED...TEMPERATURES WARMED QUICKLY INTO THE 50S AND 60S ACROSS THE PLAINS WITH MIXING BEHIND SURGE WITH TEMPERATURES MAINLY IN THE 30S AND 40S ACROSS THE MTS AND HIGH VALLEYS ATTM. TONIGHT AND MONDAY...MODERATE NORTH TO NORTHWEST FLOW PROGGED ACROSS THE REGION THROUGH LATE THIS EVENING WITH FLOW DECREASING FROM WEST TO EAST AND BECOMING MORE WESTERLY THROUGH THE DAY ON MONDAY AS EMBEDDED WAVE CONTINUES ACROSS THE NORTHERN HIGH PLAINS AND HIGH PRESSURE ALOFT ACROSS THE DESERT SW AND GREAT BASIN REGION BUILDS INTO WESTERN COLORADO. BRISK EAST TO NORTHEAST WINDS ACROSS THE PLAINS LOOKS TO DECOUPLE THROUGH THE EARLY EVENING...AND WITH A COOL AIRMASS IN PLACE UNDER SFC HIGH ALONG WITH CLEARING SKIES...SHOULD ALLOW FOR DECENT RADIATIONAL COOLING. THIS AGAIN LEADS TO TRICKY FORECAST FOR OVERNIGHT LOWS WITH WARMING ALOFT ACROSS THE WESTERN HALF OF THE AREA AS HEIGHTS BUILD. AT ANY RATE...HAVE GONE AT OR BELOW GUIDANCE FOR LOWS ACROSS THE VALLEYS AND EASTERN PLAINS WITH AT OR SLIGHTLY WARMER THAN GUIDANCE ACROSS THE HIGHER TERRAIN. TEMPS ALOFT CONTINUE TO WARM A FEW DEGREES THROUGH THE DAY MONDAY...AND HAVE STAYED AROUND CURRENT GUIDANCE TEMPS...THOUGH WENT SLIGHTLY BELOW ACROSS THE EASTERN PLAINS WITH MODEL SOUNDINGS INDICATING LIMITED MIXING DUE TO INVERSIONS HOLDING IN PLACE BETWEEN H75 AND H7 WHICH SHOULD LEAD TO NOT MUCH DIVERSITY IN TEMPERATURES ACROSS THE EASTERN MTS AND PLAINS. -MW .LONG TERM... (MONDAY NIGHT THROUGH NEXT SUNDAY) UPPER RIDGE MIGRATES ACROSS THE STATE TUESDAY...WITH 700 MB THERMAL RIDGE OVER THE EASTERN PLAINS LEADING TO ANOTHER DAY OF MILD TEMPS OVER MOST OF THE AREA. WEAK WAVE EJECTING AHEAD OF THE MAIN WESTERN TROUGH PASSES BY TO THE SOUTH LATE TUESDAY NIGHT/EARLY WEDNESDAY...BUT BEST LIFT STAYS WELL SOUTH...SO ONLY IMPACT WILL BE A FEW MID/HIGH LEVEL CLOUDS OVER SOUTHERN ZONES. UPPER LOW MOVES ONSHORE ACROSS THE WESTERN U.S. DURING THE DAY WEDNESDAY...WITH 12Z MODELS LOOKING JUST SLIGHTLY SLOWER WITH THE EASTWARD PROGRESSION OF MOISTURE AND PRECIP WED AFTERNOON AND EVENING. CUT BACK POPS OVER A FEW EASTERN MOUNTAIN ZONES WED AFTERNOON...BUT LEFT THE ISOLATED POPS INTACT FOR THE CONTINENTAL DIVIDE MOUNTAINS AS AT LEAST A COUPLE SHOWERS MAY REACH THE SAN JUANS BY LATE IN THE DAY. UPPER LOW THEN SLOWLY MOVES EASTWARD ACROSS THE SOUTHERN ROCKIES THURSDAY AND FRIDAY...WITH BOTH 12Z ECMWF AND GFS SOLUTION SHOWING A TRACK FARTHER SOUTH...DIFFERENT THAN YESTERDAY BUT SIMILAR TO SOLUTIONS FROM A FEW DAYS AGO. ALTHOUGH TRACK IS MORE FAVORABLE TODAY...MODELS WEAKEN THE LOW AS IT EJECTS EAST OF THE MOUNTAINS...WHICH COULD LIMIT PRECIP AMOUNTS...ESPECIALLY OVER THE PLAINS. APPEARS MAIN PRECIP BAND WILL MOVE ACROSS THE WESTERN HALF OF THE AREA LATE THURSDAY...WITH WINDOW FOR PRECIP OVER THE EASTERN MOUNTAINS AND PLAINS FROM LATE THURSDAY NIGHT INTO FRIDAY. PRECIP MAY START AS RAIN ALONG AND EAST OF I-25 LATE THURSDAY...BEFORE CHANGING OVER TO SNOW IN THE EVENING. MIGHT SEE ADVISORY LEVEL AMOUNTS (4 TO 8 INCHES) OVER THE SAN JUANS BY FRIDAY MORNING...THOUGH MUCH COULD CHANGE BY THEN. EASTERN MOUNTAINS AND I-25 CORRIDOR COULD SEE SOME ACCUMS AS WELL...THOUGH AMOUNTS HERE LOOK FAIRLY MODEST. LOW EJECTS EASTWARD FRIDAY AS SECOND UPPER TROUGH DIGS QUICKLY INTO THE SOUTHWEST BY LATE SATURDAY. FORECAST MAY BE HOLDING ON TO PRECIP TOO LONG ON SATURDAY...ESPECIALLY OVER THE EAST...BUT WITH ECMWF SUGGESTING LIGHT EASTERLY WINDS AT 700 MB UNTIL LATE SATURDAY AFTERNOON...WILL LEAVE THE ISOLATED POPS IN PLACE FOR NOW. STILL COOL SATURDAY...WITH MODEST WARMING SUNDAY AHEAD OF POTENTIAL COLD FRONT BACKING INTO THE EASTERN PLAINS BY SUNDAY EVENING. && .AVIATION...VFR CONDITIONS TO PERSIST FOR AT LEAST THE NEXT 24 HOURS AT TAF SITES WITH BRISK NORTH TO NORTHWEST FLOW ALOFT MODERATING TO MORE WESTERLY AS HIGH PRESSURE BUILDS IN ALOFT THROUGH THE DAY MONDAY. BRISK EAST TO NORTHEAST WINDS AT THE SFC BEHIND DRY COLD FRONT WHICH MOVED ACROSS THE SOUTHEAST PLAINS LOOK TO DECOUPLE THROUGH THE LATE EVENING WITH GENERALLY LIGHT SFC WINDS PERSISTING THROUGH MONDAY. -MW && .PUB WATCHES/WARNINGS/ADVISORIES... NONE. && $$ 23/10 co AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PUEBLO CO 311 PM MST SAT NOV 22 2008 .SHORT TERM... (TONIGHT AND SUNDAY) ...MAIN SHORT TERM CONCERN IS TEMPERATURES... CURRENT WATER VAPOR IMAGERY AND RUC UPPER AIR ANALYSIS INDICATING MODERATE WESTERLY FLOW ALOFT FROM THE WEST COAST THROUGH THE ROCKIES WITH SEVERAL MINOR EMBEDDED WAVES MOVING THROUGH THE FLOW ACROSS THE INTERMOUNTAIN WEST ATTM. WITH THE WESTERLY FLOW ALOFT...WEAK LEE TROUGHING DEEPENING ACROSS THE I-25 CORRIDOR ATTM. TONIGHT AND SUNDAY...MODELS IN DECENT AGREEMENT OF A SLIGHT INCREASE WESTERLY FLOW ALOFT TONIGHT AS MINOR EMBEDDED WAVE ACROSS SOUTHWEST IDAHO ATTM CONTINUES TO ACROSS SOUTHERN WYOMING BY 12Z SUN AND THEN CONTINUES OUT ACROSS THE NORTHERN HIGH PLAINS THROUGH SUNDAY AFTERNOON. MOVEMENT OF MINOR WAVE ALLOWS FOR LEE TROUGH TO KICK OUT ACROSS THE FAR EASTERN PLAINS THROUGH THE OVERNIGHT WITH A DRY BACKDOOR COLD FRONT/NORTHERLY SURGE MOVING ACROSS THE PLAINS LATE SUNDAY MORNING AND AFTERNOON. MODEL SOUNDINGS CONTINUE TO SHOW STRONG SFC BASED INVERSIONS DEVELOPING ACROSS THE VALLEYS THIS EVENING MAKING FOR TOUGH FORECAST FOR OVERNIGHT LOWS. HOWEVER...WITH LEE TROUGH NOT KICKING OUT UNTIL EARLY SUNDAY MORNING...HAVE STAYED THE COURSE WITH AOB GUIDANCE FOR THE NORMAL COLD POCKETS OF ALS...PUB AND LAA...THOUGH HAVE WARMED CURRENT MIN TEMP GRID ALONG AND WEST OF THE I-25 CORRIDOR WITH GENERALLY LIGHT WEST WINDS KEEPING TEMPS UP IN THE THERMAL BELT. ON SUNDAY...DEVELOPING WEAK NORTHERLY SURGE OF 10-15 MPH TO ALLOW FOR ENOUGH MIXING TO BREAK SFC AND MID LAYER INVERSIONS PER NAM SOUNDINGS AND SHOULD ALLOW FOR TEMPS TO WARM TO AT OR ABOVE TODAYS READINGS...MAINLY ACROSS THE EASTERN PLAINS...DESPITE SLOW COOLING ALOFT. AT ANY RATE...HAVE GONE IN BETWEEN THE COOLER MAV AND WARMER MET GUIDANCE WITH HIGHS LIKELY BEING REACHED BY THE EARLY AFTERNOON AND STEADY OR SLOWLY FALLING TEMPS INTO THE LATE AFTERNOON. OUT WEST...WITH THE SLIGHT COOLING ALOFT...SHOULD SEE HIGHS SLIGHTLY COOLER THAN TODAY. MAIN CHANGE OUT WEST AS TO REMOVE THE SLIGHT POPS ACROSS THE HIGHER ELEVATIONS OF THE CENTRAL MTS...AS LATEST MODEL XSECTIONS INDICATING VERY LITTLE AVAILABLE MOISTURE AND POOR LAPSE RATES SUPPORTING A FEW FLURRIES AT BEST AT MT TOPS. -MW .LONG TERM... (SUNDAY NIGHT THROUGH NEXT SATURDAY) UPPER RIDGE MIGRATES ACROSS THE ROCKIES MONDAY AND TUESDAY...WITH 700 MB TEMPS WARMING INTO THE 2-4C RANGE. ONLY WEAK SURFACE DOWNSLOPE WINDS FORECAST...WHICH SHOULD KEEP MAX TEMPS FROM CLIMBING TOO MUCH...THOUGH A FEW SPOTS ON THE PLAINS WILL CREEP INTO THE 60S BOTH DAYS. UPPER LOW DIGS INTO THE WESTERN U.S. ON WEDNESDAY...WITH MOISTURE MOVING INTO WESTERN COLORADO...MAINLY WEST OF THE CONTINENTAL DIVIDE...LATE IN THE DAY. CURRENT FORECAST OF LOW POPS OVER WESTERN ZONES DURING THE DAY SPREADING EASTWARD IN THE EVENING LOOKS FINE...WITH EASTERN MOUNTAINS AND PLAINS STAYING FAIRLY WARM AND DRY. INITIAL UPPER LOW LOOKS TO EJECT ACROSS THE AREA THURSDAY/THURSDAY NIGHT...WITH GFS JUST SLIGHTLY FASTER THAN ECMWF SOLUTION BY THE TIME THE LOW EJECTS INTO THE CENTRAL PLAINS FRIDAY MORNING. TODAY`S RUNS HAVE SHIFTED BACK NORTH WITH THE CLOSED MID-LEVEL CIRCULATION...WITH BOTH MODELS NOW HINTING AT MODEST DRY SLOT OVER SOUTHEAST COLORADO AS LOW AND MID LEVEL FLOW NEVER DEVELOPS AN EASTERLY COMPONENT. STILL WAY TOO EARLY TO TELL WHICH WAY TO LEAN...SO WILL UP POPS OVER MOUNTAIN ZONES BUT MAINTAIN JUST LOW END SCATTERED MENTION OVER LOWER ELEVATIONS. NOT MUCH COLD AIR INITIALLY IN PLACE OVER THE AREA...SO PRECIP ON THE PLAINS COULD STAY RAIN FOR SEVERAL HOURS THURSDAY BEFORE CHANGEOVER THURSDAY EVENING. MIGHT SEE SLIGHTLY BETTER CHANCES FOR AT LEAST SOME LIGHT PRECIP OVER THE EASTERN MOUNTAINS AND PLAINS FRIDAY INTO SATURDAY...AS POST FRONTAL FLOW TURNS NORTH-NORTHEAST BY LATE FRIDAY EVENING. SERIOUS DIFFERENCES BETWEEN MODELS AND LACK OF RUN TO RUN CONTINUITY REGARDING EVOLUTION OF THE SECOND UPPER LOW OVER THE SOUTHWEST DURING NEXT WEEKEND LEAD TO A BROADBRUSH OF COOL TEMPS AND LOW POPS...AS UNSETTLED WEATHER WILL CONTINUE. && .AVIATION....PER SHORT TERM DISCUSSION...VFR CONDITIONS EXPECTED THROUGH THE NEXT 24 HOURS AT ALL TAF SITES. WILL SEE A DRY BACKDOOR COLD FRONT MOVE ACROSS THE EASTERN PLAINS SUNDAY MORNING...WITH NORTHERLY WINDS OF 10-15 MPH IN ITS WAKE. -MW && .PUB WATCHES/WARNINGS/ADVISORIES... NONE. && $$ 23/10 co AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PUEBLO CO 410 AM MST SAT NOV 22 2008 .SHORT TERM... (TODAY AND TONIGHT) ...NOT A GREAT DEAL OF WEATHER PATTERN CHANGE IN NEXT 24 HOURS... CURRENTLY...CLEAR...CALM...AND CHILLY EARLY MORNING FOR MOST LOCATIONS ACROSS SOUTHERN CO. WATER VAPOR IMAGERY AND RUC MODEL UPPER AIR ANALYSES HAD NORTHWEST FLOW CONTINUING OVER THE CENTRAL ROCKIES. WEAK FEATURE MOVING INTO THE DESERT SOUTHWEST WITH HIGH CLOUDS SPREADING NORTHEAST-EASTWARD. ANY SIGNIFICANT WIND IS OVER THE MOUNTAIN PEAKS/PASSES PER HIGH TERRAIN AWOS SITES. MONARCH PASS IS BLOWING AROUND 33KTS SUSTAINED AND PIKES PEAK IS 25-35 MPH WITH GUST AROUND 60 MPH. TODAY...NOT A GREAT DEAL OF THERMAL CHANGES ALOFT...SO WOULD ANTICIPATE A NEAR REPEAT PERFORMANCE WITH HIGH TEMPERATURES COMPARED TO YESTERDAY. SOME AREAS...LIKE THE SAN LUIS VALLEY...MIGHT BE A TOUCH WARMER THAN YESTERDAY DUE TO MORE SUNSHINE. SHOULD SEE PLENTY OF SUNSHINE...EXCEPT MAYBE FOR A FEW HIGH CLOUDS FROM TIME TO TIME. AS USUAL THIS TIME OF YEAR AND PATTERN...TEMPERATURES WILL BE A CHALLENGING FOR LOW LYING AREAS LIKE PUEBLO AND THE SAN LUIS VALLEY CENTER FLOOR. AS ANTICIPATED YESTERDAY...TEMPERATURES DIDN`T WARM MUCH AT ALS AND PUB. THE SAME COULD OCCUR TODAY. 12KM NAM-WRF KEEPS THE SURFACE WINDS RELATIVELY LIGHT AND DOESN`T ACTUALLY FULLY MIX OUT TO ITS POTENTIAL AT THESE LOCATIONS. 700MB WINDS PROJECTED TO BE BE AROUND 20KT OVER SOUTHEAST CO AND ONLY 10KTS OVER THE SAN LUIS VALLEY. WENT ABOUT 3-5 DEGREES BELOW MOS AT PUB AND ALS TODAY. TONIGHT...ANOTHER STRONG RADIATIONAL COOLING NIGHT FOR THE LOW LYING AREAS LIKE THE AR RIVER VALLEY AND SAN LUIS VALLEY CENTER FLOOR. WENT A COUPLE DEGREES BELOW MOS AT ALS...PUB...LHX...AND LAA. THE NEW NAM MOS HAS BEEN PERFORMING A LITTLE BETTER DURING THESE STRONG RADIATIONAL COOLING EVENTS. THERE MIGHT BE SOME CI CLOUDS...SO HOPEFULLY THAT DOESN`T TEMPER THE COOLING TOO MUCH. METZE .LONG TERM... (SUNDAY THROUGH FRIDAY) ...SIGNIFICANT WINTER WEATHER POSSIBLE THURSDAY OR FRIDAY... MAIN WEATHER OF INTEREST IN THE EXTENDED WILL BE ON AND AROUND THE THANKSGIVING HOLIDAY. BEFORE THEN...PATTERN REMAINS RATHER TRANQUIL. A SHORTWAVE WILL MOVE THROUGH NE CO ON SUNDAY. THIS FEATURE IS LOOKING A LITTLE STRONGER THAN IN PREVIOUS MODEL RUNS...SO MIGHT ACTUALLY SEE A FEW SNOWFLAKES OVR THE NRN MTS....AROUND KLXV. HAVE INTRODUCED LOW POPS FOR THE MTS...BUT LIKELY WILL ONLY AMT TO FLURRIES IF ANYTHING. HAVE ALSO COOLED THINGS DOWN JUST A BIT FOR SUN AND SUN NIGHT WITH TEMPS ALOFT LOOKING A BIT LOWER. THE UPPER RIDGE WILL REBUILD MON AND TUE...AND TEMPS WILL AGAIN BE 10 DEG OR SO HIGHER THAN AVG FOR THE PLAINS. CLEAR SKIES WILL PREVAIL. BIG CHANGES IN THE WX BEGIN ON WED...AS A DISTURBANCE IN THE SRN BRANCH OF THE JET TAKES SHAPE OVR SRN CA OR BAJA REGION. THIS FEATURE WILL PHASE WITH A STRONG NRN BRANCH ON WED...AND THEN FOLLOW THE JET THRU THE SRN ROCKIES ON THU AND FRI. THERE IS STILL QUITE A SPREAD BETWEEN THE MODELS ON THE STRENGTH AND THE TIMING OF THIS SYSTEM. THE TREND IS FOR A SLOWER SYSTEM...WHICH WOULD PLACE THE GREATEST IMPACTS FOR SE CO FOR LATE THU INTO FRI. IF THE LATEST MODEL RUNS VERIFY...EVEN THE CENTRAL MTS MAY NOT SEE ANY PRECIP UNTIL THU MORNING. DGEX IS THE MOST AGGRESSIVE AND WOULD RESULT IN SIGNIFICANT SNOWFALL FOR THE MTS AND PLAINS BY FRI. GFS REMAINS A BIT MORE CONSERVATIVE. EC AND CANADIAN ARE A COMPROMISE. WITH THE STRONG SRN BRANCH OF THE JET...THE MORE SRN TRACK SEEN IN THE DGEX SOLUTION HAS SOME APPEAL...ALTHOUGH QPF MAY BE A BIT EXCESSIVE IN THAT MODEL. BOTTOM LINE...THERE IS POTENTIAL FOR HIGH IMPACT WINTER WX FOR MUCH OF THE AREA THU THRU FRI. HOLIDAY TRAVELERS SHOULD PLAN FOR ADVERSE CONDITIONS AND BE PREPARED TO CHANGE OR MODIFY PLANS ACCORDINGLY. IN GRIDS...CURRENTLY HAVE PRECIP STARTING AS RAIN OVR THE PLAINS ON THU...BUT WOULD NOT BE SURPRISED TO SEE AN ALL SNOW EVENT. WILL TAKE A COUPLE MORE DAYS TO PIN DOWN IF THIS IS GOING TO END UP AS A MINOR NUISANCE OR MAJOR EVENT...SO AS ALWAYS STAY TUNED FOR THE LATEST UPDATES. ROSE && .AVIATION... PER SHORT TERM DISCUSSION...VFR CLEAR BELOW 12K FT MSL WILL BE THE RULE FOR ALL AVIATION TERMINAL POINTS. METZE && .PUB WATCHES/WARNINGS/ADVISORIES... NONE. && $$ 17/44 co AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE ALBANY NY 831 PM EST SUN NOV 23 2008 .SYNOPSIS... ARCTIC HIGH PRESSURE WILL SLOWLY DRIFT OFFSHORE ALLOWING OUR UNSEASONABLY COLD AIR MASS TO MODERATE. LOW PRESSURE WILL DEVELOP TO OUR WEST ON MONDAY...AND THEN REFORM OVER OUR REGION BY TUESDAY. THIS SYSTEM WILL BRING A WINTRY MIX WHICH COULD IMPACT THANKSGIVING TRAVEL. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/... AS OF 830 PM EST...MID LEVEL CLOUDS ARE QUICKLY OVERSPREADING THE REGION FROM THE W...IN RESPONSE TO WEAKENING SHORTWAVE PASSING THROUGH...AS WELL AS INTENSIFYING MID LEVEL WARM ADVECTION/ISENTROPIC LIFT. THE RUC13 DEPICTS THIS MOISTURE RATHER WELL...ESP AROUND 700 MB...AND ALSO INDICATES THAT THE ASSOCIATED CLOUDS SHOULD GRADUALLY SHIFT TO THE N/E WELL AFTER MIDNIGHT. THUS...WE HAVE INCREASED THE CLOUD COVER THROUGH THE EARLY MORNING HOURS...AND ALSO HAVE SLOWED THE TEMP FALL OVERNIGHT...AS TEMPS SHOULD HOLD NEARLY OVER THE NEXT SEVERAL HOURS AS THE THICKEST MID LEVEL CLOUDS PASS THROUGH. THE TEMPS SHOULD ACCELERATE DOWNWARD ONCE AGAIN JUST PRIOR TO DAYBREAK...AS SOME BREAKS DEVELOP...ESP FROM ALBANY SOUTH AND WEST. THEREFORE...WE HAVE NOT CHANGED THE EXPECTED MIN TEMPS MUCH...JUST THE TEMP CURVE FOR THE OVERNIGHT PERIOD. OTHERWISE...SOME VERY LIGHT SNOW/FLURRIES ARE STILL POSSIBLE ACROSS EXTREME NORTHERN HERKIMER/NW HAMILTON COS OVER THE NEXT FEW HOURS...AS LATEST KTYX RADAR CONTINUES TO SHOW SOME WEAK REFLECTIVITIES BRUSHING THIS REGION. HOWEVER...AS LOW LEVEL FLOW CONTINUES TO BACK...AND MID LEVEL FORCING DIMINISHES...SO SHOULD THREAT OF ANY SNOW SHOWERS AFTER MIDNIGHT. && .SHORT TERM /6 AM MONDAY MORNING THROUGH WEDNESDAY/... UPPER SYSTEM DROPPING OUT OF CANADA AND THROUGH THE GREAT LAKES WILL STRENGTHEN THE SOUTHWESTERLY BOUNDARY LAYER WINDS AND WARM ADVECTION...SO EVEN WITH INCREASING HIGH AND MID CLOUDS THROUGH THE DAY...TEMPERATURES SHOULD REACH WELL INTO THE 30S TO MID 40S FOR HIGHS. MONDAY NIGHT...ISENTROPIC LIFT INCREASES AND FRONTOGENETIC FORCING INCREASES SUPPORTING PRECIPITATION SPREADING ACROSS THE REGION. GENERAL CONSENSUS FROM MOST SOURCES OF GUIDANCE/ENSEMBLES SUGGEST AREAS WEST OF THE HUDSON VALLEY COULD SEE MOSTLY SNOW MONDAY NIGHT...WHILE AREAS ALONG AND EAST OF THE HUDSON VALLEY COULD SEE A BRIEF PERIOD OF SNOW/MIX BEFORE CHANGING TO A COLD RAIN AFTER MIDNIGHT. WITH THE RAPID WARMING ALOFT...SOME AREAS COULD SEE A BRIEF PERIOD OF FREEZING RAIN AROUND SUNRISE...BEFORE SURFACE TEMPERATURES CAN RESPOND TO THE WARM ADVECTION LATER IN THE MORNING. HIGHER ELEVATIONS OF THE GREENS AND BERKSHIRES COULD SEE A DECENT PERIOD OF SNOW MONDAY NIGHT AS WELL. LOWS MONDAY NIGHT WILL BE IN THE 20S TO MID 30S...AND MAY OCCUR DURING THE EVENING WHEN PRECIPITATION BEGINS AND TEMPERATURES FALL A BIT TOWARD WET BULBS...THEN COULD RISE A COUPLE/FEW DEGREES TOWARD SUNRISE. ........... ADDED AT 434 PM... TEXT FORECAST FOR MONDAY NIGHT AND TUESDAY NORNING WILL INDICATE QUITE THE MIX AND TRANSITION OF PRECIPITATION TYPES IN SOME AREAS...BUT VARIOUS PRECIPITATION TYPES SHOULD BE OBSERVED AT DIFFERENT ELEVATION LEVELS...AND BE CHANGABLE THROUGH THE NIGHT AND MORNING. COLD GROUND COULD CONTRIBUTE TO OBSERVATIONS OF FREEZING RAIN AS WELL. SUGGESTING 2-4" OF SNOW IN SOME OF THE ADIRONDACKS THROUGH MONDAY NIGHT...AND 3-6" IN OTHER PARTS OF THE ADIRONDACKS...JUST AS A STARTING POINT...AS AMOUNTS WILL CERTAINLY NEED TO BE ADJUSTED ONE WAY OR ANOTHER AS THE EVENT GETS CLOSER. ........... ON TUESDAY...SCREAMING H8 JET BLASTS QUICKLY THROUGH NEW ENGLAND AND HEADS INTO CANADA BY LATER TUESDAY AFTERNOON...BUT MUCH OF THE STRONG WINDS SHOULD NOT MIX TO THE SURFACE. HOWEVER...IN THE HIGHER ELEVATIONS OF THE GREEN MOUNTAINS AND BERKSHIRES SHOULD SEE SOME HIGH WIND GUSTS...AND MAY ENTERTAIN WIND ADVISORIES AS THE EVENT GETS CLOSER. SNOW SHOULD CONTINUE IN THE NORTHERN CATSKILLS AND ADIRONDACKS...WITH SOME POTENTIAL MIXING WITH RAIN...AND HIGHS IN THE MID 30S. OTHERWISE...MOST AREAS WILL SEE A COLD RAIN TUESDAY WITH HIGHS IN THE UPPER 30S TO MID 40S. THE UPPER LOW SLOWS AND DRIFTS NORTH AND WEST OF OUR REGION LATER TUESDAY THROUGH WEDNESDAY. WIND ANOMALIES (-4 SD TO -6 SD U WIND ANOMALIES AT 850 MB AND -2.5 SD TO -3.5 SD AT 250 MB) STILL SUGGEST A SLOW MOVING SYSTEM WITH STRONG FORCING FOR A PROLONGED PERIOD OF HEAVY PRECIPITATION...BUT GUIDANCE SOURCES SEEM TO LIFT THE UPPER LOW INTO CANADA FAIRLY QUICKLY. STRONGEST FORCING NOW LOOKS TO BE IN NORTHERN NEW ENGLAND AND POINTS NORTH AND EAST. BOUNDARY LAYER THERMAL GRADIENT NOT AS STRONG AS SOME SIMILAR HISTORICAL STORMS...AND LOW/MID LEVEL MOISTURE FROM ATLANTIC AS GULF OF MEXICO LARGELY CUT OFF FROM THIS SYSTEM...ALTHOUGH UPPER JET AND MOISTURE PLUME SEEN ALOFT. SO THIS STORM MAY HAVE MUCH MORE OF AN IMPACT OUTSIDE OUR FORECAST AREA...BUT STILL RESPECTABLE SNOWS SHOULD BE OBSERVED IN HIGHER ELEVATIONS WITHIN OUR FORECAST AREA. THE BOTTOM LINE IS THAT AS UPPER LOW GRADUALLY DRIFTS INTO CANADA...DEEP WEST FLOW TAKES OVER...AND PRECIPITATION WILL BE LIMITED TO SNOW SHOWER ACTIVITY...AND LAKE ENHANCED PRECIPITATION. PROXIMITY OF UPPER LOW SUGGESTS KEEPING CHANCES FOR SNOW SHOWERS EVERYWHERE TUESDAY NIGHT AND RAIN/SNOWSHOWERS WEDNESDAY...WITH BEST CHANCES IN HIGHER ELEVATIONS AND AREAS NORTH OF THE MOHAWK VALLEY. LOWS TUESDAY NIGHT MID 20S IN MOUNTAINS TO AROUND OR A LITTLE BELOW FREEZING ELSEWHERE. HIGHS WEDNESDAY 30S MOUNTAINS AND AROUND 40 TO LOWER 40S ELSEWHERE. && .LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/... SIDED WITH MOS GUIDANCE. THE GFS REMAINS A LITTLE SLOWER THAN THE ECMWF AT LIFTING THE VERTICALLY STACKED THANKSGIVING STORM OUT OF THE AREA...BUT BOTH TRACK IT UP TO THE NORTH AND WEST AT A FAIRLY GOOD CLIP BY FRIDAY. THE SYNOPTIC EVENT WILL BE OVER WITH AT THE START OF THANKSGIVING DAY...BUT LAKE EFFECT WILL COMMENCE ON ITS HEELS...AS THE VERTICAL PROFILE OF THE ENSUING WESTERLY FLOW ON THE BACK SIDE OF THE SYSTEM REMAINS LOW ON SHEAR COMPARED WITH SATURDAY`S MODELS. THE LAKE EFFECT WILL PROBABLY BE A FAIRLY WELL-CONFINED BAND AFFECTING PORTIONS OF THE NORTHERN ADIRONDACKS... AND THIS WILL PROBABLY PERSIST THROUGH THE DAY AND MUCH OF THE OVERNIGHT INTO FRIDAY...WHEN THE WESTERLY FLOW BREAKS DOWN...AS DOES AN APPROACHING COLD FRONT. FOR NOW...HAVE CHC THROUGH MOST OF THE ADIRONDACKS PORTION OF OUR CWA FOR THE OVERNIGHT WED...WITH CHC ALL BUT SOUTHERNMOST CWA DURING THE HEIGHT OF TURKEY DAY...ALTHOUGH FLURRIES MAY LIKELY BE ALL THAT`S HAD AT MOST LOCATIONS OUTSIDE THE BELT. THE WEAKENING COLD FRONT MAY SET OFF SOME MORE RAIN/SNOW SHOWERS AGAIN IN THE WELL-MOISTENED ADIRONDACKS...SO HAVE CHC MAINLY NORTH AND WEST OF THE CAPITAL REGION FRI AND FRI NGT...CHIEFLY UPSLOPE REGIONS MEANWHILE...LOW PRESSURE OF PACIFIC ORIGIN DEEPENS AND TRACKS EAST TO THE DEEP SOUTH...THEN UP THE COAST. BOTH MODELS HAVE IT NEAR CAPE COD SATURDAY NIGHT...WITH SIMILAR CIRCULATION PATTERNS BETWEEN THE SURFACE AND 500 MB...SO HAVE CHC -RA/-SN SAT NGT...THEN BACK TO A LAKE EFFECT FLOW FOR SUNDAY. TEMPERATURES SHOW LITTLE DAY-TO-DAY VARIATION IN PATTERN UNTIL SUNDAY...WHEN THE DEPARTING LOW DRAWS IN MORE COLDER AIR ACROSS THE CWA. MERCURIES SHOULD HAVE NO PROBLEM GETTING TO 40 DEGREES EACH DAY IN THE HUDSON VALLEY. LOWS IN THE 20S WITH SOME ADIRONDACK UPPER TEENS EACH NIGHT BECOME LOWS MOSTLY AROUND 20 SUNDAY NIGHT... WITH SOME LOW TO MID TEENS IN THE ADIRONDACKS. THE MEX MOS VALUES ARE PRETTY CLOSE TO THE FCST VALUES...WITH THE MODEL EFFECTIVELY RECOGNIZING THE COLDER TEMPERATURES AT THE END OF THE PERIOD. && .AVIATION /02Z MONDAY THROUGH FRIDAY/... VFR CONDITIONS ARE EXPECTED THROUGH AT LEAST 00Z/TUE. A PERIOD OF MID LEVEL CLOUDS WILL OCCUR THIS EVENING THROUGH THE PRE DAWN HOURS...AS MID LEVEL WARM ADVECTION OCCURS. THEREAFTER...EXPECT JUST SOME PATCHY HIGH/MID LEVEL CLOUDS TUE MORNING THROUGH MID AFTERNOON...BEFORE CLOUDS RAPIDLY THICKEN FROM SW TO NE AFTER 22Z/MON. WINDS WILL REMAIN LIGHT...TRENDING INTO THE S TO SW OVERNIGHT AT LESS THAN 5 KT. SOUTH TO SOUTHEAST WINDS WILL THEN INCREASE ON MON...TO 5-10 KT...BECOMING STRONGER AFTER 00Z/TUE. OUTLOOK... MON NIGHT-TUE...MVFR/IFR. -RA...CHC -SN. LLWS POSS. WED-THU...VFR/MVFR. CHC -SHRA/-SHSN. && .HYDROLOGY... NO HYDROLOGY PROBLEMS THROUGH MONDAY AS IT WILL REMAIN MAINLY DRY WITH ANY PRECIPITATION FALLING AS LIGHT SNOW SHOWERS. A COMPLEX STORM WILL LIKELY BRING SIGNIFICANT PRECIPITATION TO THE REGION MONDAY NIGHT INTO TUESDAY...WITH AN UNSETTLED WEATHER PATTERN TUESDAY NIGHT THROUGH FRIDAY NIGHT WITH PRECIPITATION TAKING THE FORM OF WIDELY SCATTERED TO NUMEROUS SNOW OR MIXED RAIN/SNOW SHOWERS. MIXED PCPN LIKELY MONDAY NIGHT AND TUESDAY...WITH MAINLY SNOW OVER HIGHER TERRAIN WEST OF THE HUDSON VALLEY...MAINLY RAIN IN THE HUDSON VALLEY...AND ABOUT 50-50 MIX OVER THE HIGHER TERRAIN EAST OF THE HUDSON VALLEY. MANY AREAS COULD SEE COULD SEE A TOTAL OF A HALF TO THREE QUARTERS OF AN INCH OF PRECIPITATION...MAINLY RAIN BY LATE TUESDAY. SOME PARTS OF THE CATSKILLS...TACONICS AND BERKSHIRES COULD SEE LOCALLY HEAVIER RAINFALL...AN INCH OR MORE. AT THIS POINT...IT DOES NOT LOOK LIKE FLOODING WILL BE A PROBLEM ASIDE FROM PAVED AREAS WHERE DRAINAGE MAY BE BLOCKED BY PILES OF SNOW OR DEBRIS. HOWEVER A POTENTIAL EXISTS THAT THE STORM COULD BRING MORE RAIN THAN CURRENTLY EXPECTED. FOR DETAILS ON THE RIVERS...PLEASE VISIT THE ADVANCED HYDROLOGIC PREDICTION SERVICE /AHPS/ GRAPHS ON OUR WEBSITE. && .ALY WATCHES/WARNINGS/ADVISORIES... CT...NONE. NY...NONE. MA...NONE. VT...NONE. && $$ SYNOPSIS...NAS NEAR TERM...KL/NAS SHORT TERM...NAS LONG TERM...HELLER AVIATION...FRUGIS/KL HYDROLOGY...NAS ct AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MIAMI FL 955 PM EST SUN NOV 23 2008 .UPDATE...ON A MINOR TWEAK TO THE WINDS NEEDED THIS EVENING TO REFLECT CURRENT TRENDS, HOWEVER THAT MAINLY AFFECTED THE BAY AND ATLANTIC ZONES. ALL OTHER ELEMENTS UNCHANGED AS THE PREVIOUS FORECAST REMAINS ON TARGET. /TINGLER && .MARINE...GUIDANCE CONTINUES TO SHOW WINDS ACROSS THE ATLANTIC ZONES REMAINING MARGINAL FOR A SMALL CRAFT ADVISORY, AND INDEED FOWEY HAS BEEN AT 20 TO 23 KNOTS THIS EVENING FOR THE PAST FEW HOURS. SO, HAVE DECIDED TO PLAY IT SAFE AND KEEP THE SCA GOING THROUGH THE NIGHT FOR THE BAY AND ATLANTIC ZONES. ADDED THE BAY SINCE EASTERLY WINDS WILL AFFECT THE CENTRAL SECTIONS. THE MIAMI- DADE AND BROWARD COASTAL WATERS WILL THE ZONES MOST AFFECTED SINCE THE GRADIENT IS TIGHTER TO THE SOUTH, HOWEVER ALSO KEPT THE PALM BEACH WATERS IN AS WELL DUE TO A RECENT SHIP REPORT OF 20KTS. /TINGLER && .PREV DISCUSSION... /ISSUED 720 PM EST SUN NOV 23 2008/ AVIATION... VFR CONDITIONS WILL PERSIST ACROSS ALL SOUTH FLORIDA TERMINALS THIS FORECAST CYCLE...WITH THE PRIMARY CONCERN BEING WINDS. ALL AVAILABLE GUIDANCE NOW SUGGESTS THAT PRESSURE GRADIENT AND RESULTING ENE FLOW WILL STRENGTHEN OVER THE ATLANTIC TONIGHT... WHICH MAY BE THE KEY FACTOR IN DEVELOPMENT OF A LAND BREEZE. AT THIS TIME...WILL INDICATE NO LAND BREEZE AT PBI/FLL...AS EASTERLY FLOW SHOULD BE SUFFICIENTLY STRONG TO PREVENT A PENETRATION THIS CLOSE TO THE COAST. HOWEVER...AT TERMINALS FURTHER INLAND...WILL INDICATE WINDS BACKING TO NNW AND DECREASING IN THE PREDAWN HOURS ON MONDAY. WINDS WILL REMAIN LIGHTER AND FROM THE NE OVERNIGHT AT KAPF...WITH ESE FLOW OF 8-12 KNOTS EXPECTED AT ALL TERMINALS DURING THE DAY ON MONDAY. OTHERWISE...CLOUD CONDS OF FEW050/SCT070 WILL PREVAIL THROUGH THE PERIOD...AND ENOUGH THREAT FOR SHRA TO INCLUDE VCSH ALONG THE EAST COAST OVERNIGHT. MANY THANKS TO ZMA CWSU FOR EXCELLENT THOUGHTS AND INPUT FOR THIS FORECAST. 70/DD PREV DISCUSSION... /ISSUED 234 PM EST SUN NOV 23 2008/ DISCUSSION...HIGH PRESSURE WILL PULL AWAY FROM THE MID ATLANTIC COAST TONIGHT THROUGH MONDAY...RESULTING IN OUR PREVAILING WINDS TURNING MORE EASTERLY. MOISTURE WILL INCREASE SLIGHTLY...THOUGH BELIEVE THE GFS/NAM ARE A BIT TOO BULLISH ON THIS. KEPT SLIGHT CHANCE POPS NEXT FEW DAYS FOR THE ATLANTIC COAST...BUT OTHERWISE MOSTLY DRY WEATHER IS EXPECTED TO CONTINUE. MOST CHALLENGING PART OF THE FCST IS AGAIN ON THE LAND BREEZE AND ITS EFFECTS ON TEMPS AGAIN TONIGHT...AND MONDAY NIGHT AS WELL. GFS/NAM AND EVEN THE WRF DO NOT SHOW THE LAND BREEZE DEVELOPING TONIGHT. HOWEVER...THE PATTERN IS NOT CHANGING MUCH AND SO WE BELIEVE IT WILL OCCUR. THE NAM/WRF LOOK WAY TOO AGGRESSIVE WITH WINDS OVERNIGHT...AND THEY START THE DEVELOPMENT OF THE LAND BREEZE EARLY ON BEFORE THE WINDS SURGE TAKES OVER SWITCHING WINDS BACK NE. SINCE THIS SURGE LOOKS TO AGGRESSIVE...DECIDED TO DISCOUNT THIS. GIVEN THE FACT THAT GOOD RADIATIONAL COOLING IS AGAIN EXPECTED IN A STILL RATHER DRY AIRMASS...DECIDED TO BRING THE LAND BREEZE ACROSS MUCH OF THE EAST COAST METRO AREAS AGAIN TONIGHT...BUT NOT QUITE TO THE COAST...REASON BEING THAT IT MADE IT TO THE COAST JUST FOR AN HOUR THIS MORNING...AND ANY SLIGHT INCREASE IN THE NE-E WIND OVERNIGHT WOULD HOLD IT AT BAY. SHOULD MENTION THAT THE RUC IS ACTUALLY FOLLOWING RIGHT ALONG WITH OUR EXPECTATIONS TONIGHT. THE MAIN IMPACT THE FCST ON THE LAND BREEZE HAS IS WITH REGARDS TO TEMPS...AS IT CAN FLUCTUATE 5-10F DEGREES ON EITHER SIDE OF THE BOUNDARY...AS SEEN OVER THE PAST FEW MORNING`S. KEPT PATCHY FOG IN THE FCST TONIGHT AND MON NIGHT. MON NIGHT LOOKS TO BE MOST OPTIMAL...AHEAD OF A PRE-FRONTAL TROUGH. GFS/ECMWF STILL SHOW THE COLD FRONT MOVING ACROSS THE AREA TUESDAY NIGHT INTO WED MORNING...WITH A PRE-FRONTAL TROUGH MOVING BY ON TUESDAY. AFTER TEMPS WARM FINALLY TO NEAR 80 AHEAD OF THE FRONT TUESDAY...A SLIGHT COOL DOWN WILL OCCUR ON WEDNESDAY BEHIND THE FRONT. MOISTURE WILL REMAIN LIMITED...SO MOSTLY DRY WEATHER IS ANTICIPATED. MADE NO CHANGES TO THE EXTENDED FCST. THE DRY NOVEMBER WEATHER PATTERN LOOKS TO CONTINUE. BOTH GFS/ECMWF SHOW A GRADUAL WARMING TREND LATE IN THE WEEK AND INTO NEXT WEEKEND...WITH YET ANOTHER COLD FRONT EXPECTED EITHER SUNDAY OR MONDAY...DEPENDING ON THE MODEL...AND JUST TOO EARLY TO TELL AT THIS POINT IN TIME...BUT THE PARADE OF FRONTS LOOK TO CONTINUE. MARINE...DECIDED TO EXTEND THE SMALL CRAFT ADVISORY FOR THE ATLANTIC WATERS THROUGH THIS EVENING...AS GULF STREAM SEAS WILL LIKELY NOT START SUBSIDING UNTIL LATE EVENING AND OVERNIGHT DUE TO THE FACT THAT WINDS WILL REMAIN FROM A MORE NE DIRECTION BEFORE BECOMING EASTERLY LATER TONIGHT. OTHERWISE...WINDS OVER THE NEXT FEW DAYS WILL SLACKEN LEADING TO IMPROVING MARINE CONDITIONS. THE PRE-FRONTAL TROUGH WILL MOVE ACROSS THE AREA TUESDAY...SWITCHING WINDS TO W-NW...AND THE ACTUAL COLD FRONT WILL MOVE ACROSS THE AREA TUE NIGHT INTO EARLY WED MORNING...WITH A BRIEF WIND SURGE EXPECTED BEHIND IT...BUT GUIDANCE SUGGESTS ONLY 15-20 KT AND NOT TOO PROLONGED. FIRE WEATHER...RH`S HAVE BEEN DOWN AGAIN TO NEAR 40 PERCENT AS SOME DRY AIR HAS MIXED DOWN. MOISTURE WILL INCREASE JUST A TAD ON MONDAY. SLIGHT DRYING IS EXPECTED TUESDAY BEHIND A PRE-FRONTAL TROUGH...BUT NOT EXPECTED TO BE DRY ENOUGH AT THIS TIME TO RESULT IN CRITICAL RH`S. HOWEVER...WILL MONITOR TRENDS...BECAUSE TUE WILL BE THE WARMEST DAY OF THE WEEK...AND IF MORE DRYING OCCURS BETWEEN THE PRE-FRONTAL TROUGH AND THE ACTUAL COLD FRONT...THEN RH`S COULD FALL LOWER THAN FCST. THE DRIEST AIR WILL ADVECT IN ACROSS THE AREA BEHIND THE FRONT ON WEDNESDAY. TRENDED DEW POINTS/RH`S DOWN...THOUGH NOT AS LOW AS THE NAM AT THIS TIME...WHICH DROPS DEW POINTS TO THE LOWER 30S NW INTERIOR TO THE LOWER 40S SE. WE LIKELY WILL NEED TO CONTINUE A DECREASING TREND IN COMING FCSTS. && .PRELIMINARY POINT TEMPS/POPS... WEST PALM BEACH 62 75 60 79 / 20 20 20 10 FORT LAUDERDALE 67 77 62 79 / 20 20 20 10 MIAMI 62 77 62 80 / 20 20 20 10 NAPLES 56 76 61 77 / - 10 10 10 && .MFL WATCHES/WARNINGS/ADVISORIES... FL...NONE. AM...SMALL CRAFT ADVISORY UNTIL 7 AM EST MONDAY FOR AMZ630-AMZ650- AMZ651-AMZ670-AMZ671. GM...NONE. && $$ fl AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MIAMI FL 720 PM EST SUN NOV 23 2008 .AVIATION... VFR CONDITIONS WILL PERSIST ACROSS ALL SOUTH FLORIDA TERMINALS THIS FORECAST CYCLE...WITH THE PRIMARY CONCERN BEING WINDS. ALL AVAILABLE GUIDANCE NOW SUGGESTS THAT PRESSURE GRADIENT AND RESULTING ENE FLOW WILL STRENGTHEN OVER THE ATLANTIC TONIGHT... WHICH MAY BE THE KEY FACTOR IN DEVELOPMENT OF A LAND BREEZE. AT THIS TIME...WILL INDICATE NO LAND BREEZE AT PBI/FLL...AS EASTERLY FLOW SHOULD BE SUFFICIENTLY STRONG TO PREVENT A PENETRATION THIS CLOSE TO THE COAST. HOWEVER...AT TERMINALS FURTHER INLAND...WILL INDICATE WINDS BACKING TO NNW AND DECREASING IN THE PREDAWN HOURS ON MONDAY. WINDS WILL REMAIN LIGHTER AND FROM THE NE OVERNIGHT AT KAPF...WITH ESE FLOW OF 8-12 KNOTS EXPECTED AT ALL TERMINALS DURING THE DAY ON MONDAY. OTHERWISE...CLOUD CONDS OF FEW050/SCT070 WILL PREVAIL THROUGH THE PERIOD...AND ENOUGH THREAT FOR SHRA TO INCLUDE VCSH ALONG THE EAST COAST OVERNIGHT. MANY THANKS TO ZMA CWSU FOR EXCELLENT THOUGHTS AND INPUT FOR THIS FORECAST. 70/DD && .PREV DISCUSSION... /ISSUED 234 PM EST SUN NOV 23 2008/ DISCUSSION...HIGH PRESSURE WILL PULL AWAY FROM THE MID ATLANTIC COAST TONIGHT THROUGH MONDAY...RESULTING IN OUR PREVAILING WINDS TURNING MORE EASTERLY. MOISTURE WILL INCREASE SLIGHTLY...THOUGH BELIEVE THE GFS/NAM ARE A BIT TOO BULLISH ON THIS. KEPT SLIGHT CHANCE POPS NEXT FEW DAYS FOR THE ATLANTIC COAST...BUT OTHERWISE MOSTLY DRY WEATHER IS EXPECTED TO CONTINUE. MOST CHALLENGING PART OF THE FCST IS AGAIN ON THE LAND BREEZE AND ITS EFFECTS ON TEMPS AGAIN TONIGHT...AND MONDAY NIGHT AS WELL. GFS/NAM AND EVEN THE WRF DO NOT SHOW THE LAND BREEZE DEVELOPING TONIGHT. HOWEVER...THE PATTERN IS NOT CHANGING MUCH AND SO WE BELIEVE IT WILL OCCUR. THE NAM/WRF LOOK WAY TOO AGGRESSIVE WITH WINDS OVERNIGHT...AND THEY START THE DEVELOPMENT OF THE LAND BREEZE EARLY ON BEFORE THE WINDS SURGE TAKES OVER SWITCHING WINDS BACK NE. SINCE THIS SURGE LOOKS TO AGGRESSIVE...DECIDED TO DISCOUNT THIS. GIVEN THE FACT THAT GOOD RADIATIONAL COOLING IS AGAIN EXPECTED IN A STILL RATHER DRY AIRMASS...DECIDED TO BRING THE LAND BREEZE ACROSS MUCH OF THE EAST COAST METRO AREAS AGAIN TONIGHT...BUT NOT QUITE TO THE COAST...REASON BEING THAT IT MADE IT TO THE COAST JUST FOR AN HOUR THIS MORNING...AND ANY SLIGHT INCREASE IN THE NE-E WIND OVERNIGHT WOULD HOLD IT AT BAY. SHOULD MENTION THAT THE RUC IS ACTUALLY FOLLOWING RIGHT ALONG WITH OUR EXPECTATIONS TONIGHT. THE MAIN IMPACT THE FCST ON THE LAND BREEZE HAS IS WITH REGARDS TO TEMPS...AS IT CAN FLUCTUATE 5-10F DEGREES ON EITHER SIDE OF THE BOUNDARY...AS SEEN OVER THE PAST FEW MORNING`S. KEPT PATCHY FOG IN THE FCST TONIGHT AND MON NIGHT. MON NIGHT LOOKS TO BE MOST OPTIMAL...AHEAD OF A PRE-FRONTAL TROUGH. GFS/ECMWF STILL SHOW THE COLD FRONT MOVING ACROSS THE AREA TUESDAY NIGHT INTO WED MORNING...WITH A PRE-FRONTAL TROUGH MOVING BY ON TUESDAY. AFTER TEMPS WARM FINALLY TO NEAR 80 AHEAD OF THE FRONT TUESDAY...A SLIGHT COOL DOWN WILL OCCUR ON WEDNESDAY BEHIND THE FRONT. MOISTURE WILL REMAIN LIMITED...SO MOSTLY DRY WEATHER IS ANTICIPATED. MADE NO CHANGES TO THE EXTENDED FCST. THE DRY NOVEMBER WEATHER PATTERN LOOKS TO CONTINUE. BOTH GFS/ECMWF SHOW A GRADUAL WARMING TREND LATE IN THE WEEK AND INTO NEXT WEEKEND...WITH YET ANOTHER COLD FRONT EXPECTED EITHER SUNDAY OR MONDAY...DEPENDING ON THE MODEL...AND JUST TOO EARLY TO TELL AT THIS POINT IN TIME...BUT THE PARADE OF FRONTS LOOK TO CONTINUE. MARINE...DECIDED TO EXTEND THE SMALL CRAFT ADVISORY FOR THE ATLANTIC WATERS THROUGH THIS EVENING...AS GULF STREAM SEAS WILL LIKELY NOT START SUBSIDING UNTIL LATE EVENING AND OVERNIGHT DUE TO THE FACT THAT WINDS WILL REMAIN FROM A MORE NE DIRECTION BEFORE BECOMING EASTERLY LATER TONIGHT. OTHERWISE...WINDS OVER THE NEXT FEW DAYS WILL SLACKEN LEADING TO IMPROVING MARINE CONDITIONS. THE PRE-FRONTAL TROUGH WILL MOVE ACROSS THE AREA TUESDAY...SWITCHING WINDS TO W-NW...AND THE ACTUAL COLD FRONT WILL MOVE ACROSS THE AREA TUE NIGHT INTO EARLY WED MORNING...WITH A BRIEF WIND SURGE EXPECTED BEHIND IT...BUT GUIDANCE SUGGESTS ONLY 15-20 KT AND NOT TOO PROLONGED. FIRE WEATHER...RH`S HAVE BEEN DOWN AGAIN TO NEAR 40 PERCENT AS SOME DRY AIR HAS MIXED DOWN. MOISTURE WILL INCREASE JUST A TAD ON MONDAY. SLIGHT DRYING IS EXPECTED TUESDAY BEHIND A PRE-FRONTAL TROUGH...BUT NOT EXPECTED TO BE DRY ENOUGH AT THIS TIME TO RESULT IN CRITICAL RH`S. HOWEVER...WILL MONITOR TRENDS...BECAUSE TUE WILL BE THE WARMEST DAY OF THE WEEK...AND IF MORE DRYING OCCURS BETWEEN THE PRE-FRONTAL TROUGH AND THE ACTUAL COLD FRONT...THEN RH`S COULD FALL LOWER THAN FCST. THE DRIEST AIR WILL ADVECT IN ACROSS THE AREA BEHIND THE FRONT ON WEDNESDAY. TRENDED DEW POINTS/RH`S DOWN...THOUGH NOT AS LOW AS THE NAM AT THIS TIME...WHICH DROPS DEW POINTS TO THE LOWER 30S NW INTERIOR TO THE LOWER 40S SE. WE LIKELY WILL NEED TO CONTINUE A DECREASING TREND IN COMING FCSTS. && .PRELIMINARY POINT TEMPS/POPS... WEST PALM BEACH 62 75 60 79 / 20 20 20 10 FORT LAUDERDALE 67 77 62 79 / 20 20 20 10 MIAMI 62 77 62 80 / 20 20 20 10 NAPLES 56 76 61 77 / - 10 10 10 && .MFL WATCHES/WARNINGS/ADVISORIES... FL...NONE. AM...SMALL CRAFT ADVISORY UNTIL 10 PM EST THIS EVENING FOR AMZ650- AMZ651-AMZ670-AMZ671. GM...NONE. && $$ LONG TERM...04/AT SHORT TERM/AVIATION...70/DD fl AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TALLAHASSEE FL 300 PM EST SUN NOV 23 2008 .SYNOPSIS... 19Z WATER VAPOR AND H4 RUC ANALYSIS CONTINUE TO SHOW A RATHER COMPLEX UPPER LEVEL PATTERN OVER NORTH AMERICA THIS AFTERNOON. TWO LARGE UPPER LOWS SPINNING ACROSS WEST-CENTRAL CANADA AND OVER EASTERN QUEBEC REMAIN THE DOMINANT STEERING MECHANISMS FOR THE NORTHERN STREAM. THIS FLOW DIVES INTO SHORTWAVE ENERGY MOVING ACROSS THE NORTHERN PLAINS STATES AROUND THE SOUTHERN PERIPHERY OF THE FIRST MENTIONED UPPER LOW. THE FLOW THEN BRIEFLY RIDGES UP THROUGH THE GREAT LAKES STATES BEFORE DIVING SOUTHEAST TO THE MID-ATLANTIC AROUND THE SOUTHERN PERIPHERY OF THE UPPER LOW ACROSS EASTERN CANADA. ABUNDANT SOUTHERN STREAM MOISTURE IS SEEN ON WV IMAGERY CONTINUING TO STREAM NORTHWARD OVER MEXICO AND INTO THE SOUTHERN PLAINS. THIS MID-UPPER LEVEL MOISTURE WILL HELP FUEL THE EVOLUTION OF THE SHORTWAVE CURRENTLY OVER THE NORTHERN PLAINS AS IT AMPLIFIES INTO THE MS VALLEY THROUGH MONDAY. IN THE LOWER LEVELS...SURFACE RIDGE AXIS EXTENDS FROM THE CAROLINA COAST SOUTHWEST INTO THE FORECAST AREA KEEPING THE GRADIENT RELAXED AND OUR WINDS LIGHT FROM THE EAST AND NORTHEAST THIS AFTERNOON. A MID-LEVEL AC DECK OVER THE WESTERN HALF OF THE AREA EARLY THIS MORNING RESULTED FROM AN IMPRESSIVE RIDGE OF ISENTROPIC UPGLIDE BELOW 10KFT ARCHING FROM SOUTHERN LA ACROSS SOUTHERN MS/AL. THIS AC DECK HAS BROKEN UP SIGNIFICANTLY SINCE SUNRISE AND RETREATED BACK TO OUR FAR WESTERN SE AL ZONES AS THE BEST UPGLIDE FROM THIS MORNING HAS WEAKENED AND DRIFTED FURTHER NORTH. WITH PARTLY TO MOSTLY SUNNY SKIES NOW IN CONTROL REGION-WIDE TEMPERATURES HAVE RESPONDED TO THE LOWER 60S NORTH AND INTO THE MIDDLE/UPPER 60S SOUTH. .SHORT TERM (TONIGHT THROUGH TUESDAY NIGHT)... SURFACE RIDGE WILL STILL BE IN CONTROL OF THE AREA TONIGHT...HOWEVER IT WILL BE WEAKENING. EASTERLY FLOW WILL SLOWLY COME AROUND TO THE SOUTHEAST ALLOWING FOR A SLOW INCREASE IN LOW LEVEL MOISTURE. THIS MOISTURE ADVECTION COMBINED WITH A SLOW INCREASE IN CLOUDS FROM THE WEST SHOULD RESULT IN A WARMER OVERNIGHT PERIOD THAN HAS BEEN EXPERIENCED THE PAST SEVERAL NIGHTS. IN FACT LOW TEMPERATURES TONIGHT SHOULD BOTTOM OUT IN THE LOWER 40S FOR THE COLDEST LOCATIONS WITH UPPER 40S AND LOWER 50S ALONG THE COAST FROM FRANKLIN COUNTY TO THE FLORIDA PANHANDLE. THROUGH THE DAY ON MONDAY WILL BE WATCHING SHORTWAVE ENERGY CURRENTLY OVER THE HIGH PLAINS DIVE SOUTHEAST. THIS ENERGY WILL BE RE-ENFORCED BY ANOTHER STRONG SHORTWAVE DROPPING OUT OF CENTRAL CANADA TO PRODUCE A FAIRLY HIGH AMPLITUDE TROUGH ALONG THE MS VALLEY BY THE AFTERNOON/EVENING HOURS. DEEP SYNOPTIC LIFT AHEAD OF THIS MID/UPPER LEVEL TROUGH WILL INTERACT WITH A WEAK LOW LEVEL FRONTAL BOUNDARY TO CONSOLIDATE LOW PRESSURE OVER THE EASTERN GREAT LAKES THROUGH THE DAY. THIS WILL ALSO WORK TO STRENGTHEN THE TRAILING COLD FRONT EXTENDING SOUTHWARD TO THE LOWER MS VALLEY. AS THIS FRONT PROGRESSES EASTWARD INTO THE AFTERNOON HOURS...RAIN CHANCES IN THE FORM OF SHOWER AND ISOLATED THUNDERSTORMS WILL BE INCREASING ACROSS THE NORTHWEST THIRD OF THE FORECAST AREA. AT THIS TIME THE BULK OF THE SHOWERS OVER THESE FAR WESTERN ZONES SHOULD HOLD OFF UNTIL THE LATER AFTERNOON OR EARLY EVENING HOURS. FURTHER EAST WILL SEE INCREASING CLOUDS THROUGH THE DAY AFTER SOME MORNING SUN. COOLEST TEMPERATURES EXPECTED IN THE NORTHWEST ZONES WITH THE THICKER CLOUDS WHERE LOWER TO MIDDLE 60S WILL BE COMMON. FURTHER SOUTHEAST THERE WILL BE MORE OF AN OPPORTUNITY FOR SIGNIFICANT WARMING AND TEMPS AROUND 70 ARE EXPECTED. DO ANTICIPATE ANOTHER COOLER POCKET DOWN ALONG THE FRANKLIN COUNTY COAST AS EASTERLY FLOW BRINGS COOLER AIR OFF THE SHELF WATERS OF APALACHEE BAY. COLD FRONT WILL CROSS THE FORECAST AREA FROM WEST TO EAST MONDAY NIGHT. UPPER LEVEL ENERGY ROUNDING THE BASE OF THE MAIN TROUGH IS SHEARED RAPIDLY OFF TO THE NORTHEAST DURING THE NIGHT WITH ONLY A WEAK BAND OF DEEP LAYER SYNOPTIC LIFT CROSSING THROUGH. MAIN SYNOPTIC LIFT WITH THIS FEATURE WILL REMAIN MUCH FURTHER TO THE NORTH ACROSS NORTHERN GA...THE CAROLINAS...AND MID-ATLANTIC STATES. GFS/NAM ALSO SHOWING A RATHER THIN MOISTURE AXIS AHEAD OF THE FRONT MOVING RAPIDLY ACROSS THE AREA. THEREFORE...WILL FORECAST A WEAKENING AND THINNING BAND OF SHOWERS/ISOLATED THUNDERSTORMS ALONG AND AHEAD OF THIS FRONT. IN FACT ANY THUNDERSTORM ARE LIKELY TO BE CONFINED TO AREAS WEST OF THE APALACHICOLA RIVER...AND MAINLY DURING THE EVENING HOURS. AFTER MIDNIGHT THUNDER SHOULD BE CONFINED TO THE COASTAL WATERS...IN CLOSER PROXIMITY TO THE BEST INSTABILITY. WITH THIS IN MIND...THE HIGHEST POPS (LIKELY RANGE) ARE ACROSS THE WEST DURING THE EVENING HOURS AND THEN TAPER TO CHANCE POPS AFTER MIDNIGHT ACROSS THE EAST. AS THE BAND REACHES THE SUWANNEE RIVER VALLEY TOWARD SUNRISE TUESDAY...THIS BAND OF SHOWERS MAY BE ESPECIALLY BRIEF IN NATURE WITH VERY LIGHT ACCUMULATIONS. ANY SHOWERS/SPRINKLES OVER THE SOUTHEAST BIG BEND WILL END EARLY TUESDAY MORNING AS THE FRONT PUSHES FURTHER SOUTH. HIGH PRESSURE WILL TAKE CONTROL EARLY AND THEN BUILDS OVERHEAD TUESDAY NIGHT INTO WEDNESDAY. LOOKING FOR A BREEZY AND COOL AFTERNOON HIGH TEMPS AROUND 60 NORTH AND THE LOWER TO MIDDLE 60S SOUTH. WITH THE HIGH IN CLOSE PROXIMITY TUESDAY NIGHT AND DRY AIR ONCE AGAIN IN PLACE...THE STAGE SEEM SET FOR ANOTHER DECENT RADIATIONAL COOLING EVENT. COLDER INTERIOR SPOTS...ARE ONCE AGAIN ANTICIPATED TO APPROACH FREEZING WITH AREAS OF FROST DURING THE LATE NIGHT HOURS. && .LONG TERM (WEDNESDAY THROUGH SUNDAY)... THE VERY PROGRESSIVE PATTERN CONTINUES ACROSS THE SE U.S....AND ANOTHER COLD AND DRY CANADIAN SFC RIDGE WILL BUILD IN ACROSS THE CWA FOR WED AND THU...AS CONFIDENCE CONTINUES TO INCREASE THAT PORTIONS OF THE INTERIOR WILL LIKELY EXPERIENCE A LIGHT FREEZE ON WED AND THU MORNINGS. THIS RIDGE WILL THEN MOVE QUICKLY OFF THE SE U.S. COASTLINE ON FRIDAY...ALLOWING THE NEXT COLD FRONT TO PUSH THROUGH FRI NIGHT AND SAT MORNING. THIS SYSTEM IS BEGINNING TO LOOK A BIT MORE POTENT WITH TIME...AND ALTHOUGH WE KEPT JUST SHOWERS IN THE GRIDS ON LAST NIGHT`S PACKAGE ...THIS LOW MAY HAVE JUST ENOUGH RETURN FLOW MOISTURE AND DYNAMICS TO WORK WITH TO ALLOW SCT TSTMS TO BE INTRODUCED INTO THE FCST OUT AHEAD OF THE COLD FRONT. THE 12 UTC RUN OF THE ECMWF HAS MORE OF A SPLIT FLOW SOLUTION WITH THIS EVENT...AND THEREFORE HAS A WEAKER SFC SYSTEM AND LAGS THE COLD FRONTAL PASSAGE UNTIL SAT NIGHT-SUN MORNING. BELIEVE THAT THE MORE CONTIGUOUS GFS EVOLUTION LOOKS BETTER AT THIS TIME...SO AM HOPING THE 00 UTC RUN OF THE ECMWF CONVERGES TOWARDS THIS PREFERRED SOLUTION. IF NOT...WE`LL RESERVE THE RIGHT TO MAKE SOME END OF SHIFT ADJUSTMENTS TO THE END OF THE FCST PERIOD. && .MARINE... SURFACE RIDGE WEAKEN ACROSS THE NORTHEAST GULF TONIGHT ALLOWING WINDS TO COME AROUND TO THE EAST AND SOUTHEAST BY MONDAY MORNING. A COLD FRONT WILL BE APPROACHING FROM THE WEST DURING MONDAY AFTERNOON AND CROSSING THE FORECAST WATERS MONDAY NIGHT AND EARLY TUESDAY MORNING. EXPECT A SHARP SHIFT IN THE WINDS TO THE NORTH WITH AND INCREASE IN SPEED TO NEAR ADVISORY LEVELS AFTER THE FRONTAL PASSAGE. CAUTIONARY TO ADVISORY LEVEL WINDS AND SEAS WILL HOLD THROUGH THE DAY TUESDAY AND THEN BEGIN TO SLOWLY SUBSIDE WEDNESDAY AS HIGH PRESSURE BUILDS OVER THE NORTHEAST GULF OF MEXICO. THIS HIGH WILL KEEP WINDS AND SEAS LOW THROUGH THURSDAY BEFORE THE NEXT SYSTEM APPROACHES FROM THE WEST FOR THE BEGINNING OF THE UPCOMING WEEKEND. && .AVIATION... VFR CONDITIONS WILL CONTINUE THROUGH THIS AFTERNOON AND TONIGHT... WITH LIGHT EAST TO SOUTHEAST WINDS (LESS THAN 10 KT). BRIEF PERIODS OF CIGS OF 5-10K FT WILL BE POSSIBLE AT KDHN AND KABY THIS AFTERNOON. ANY RAIN THAT DEVELOPS AHEAD OF AN APPROACHING COLD FRONT WILL LIKELY HOLD OFF AT KDHN UNTIL AFTER 18 UTC MONDAY. && .FIRE WEATHER... RED FLAG CONDITIONS ARE NOT EXPECTED THROUGH MONDAY. IT IS POSSIBLE THAT PORTIONS OF OUR FL ZONES COULD GET RED FLAG CONDITIONS TUESDAY AFTERNOON...BUT WE WILL WAIT ON ISSUING A WATCH GIVEN HOW UNCERTAIN POST-FRONTAL ENVIRONMENTS CAN BE. && .PRELIMINARY POINT TEMPS/POPS... TALLAHASSEE 41 70 48 65 32 / 0 10 50 10 0 PANAMA CITY 49 69 51 65 40 / 0 20 60 10 0 DOTHAN 44 65 44 63 34 / 0 50 60 0 0 ALBANY 40 67 44 62 30 / 0 30 60 0 0 VALDOSTA 39 70 46 65 33 / 0 10 40 10 0 CROSS CITY 40 72 53 70 33 / 0 0 20 30 0 && .TAE WATCHES/WARNINGS/ADVISORIES... AL...NONE. GA...NONE. FL...NONE. GM...NONE. && $$ AVIATION/FIRE WEATHER...FOURNIER SYNOPSIS/SHORT TERM/MARINE...MROCZKA LONG TERM...GOULD fl AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MIAMI FL 234 PM EST SUN NOV 23 2008 .DISCUSSION...HIGH PRESSURE WILL PULL AWAY FROM THE MID ATLANTIC COAST TONIGHT THROUGH MONDAY...RESULTING IN OUR PREVAILING WINDS TURNING MORE EASTERLY. MOISTURE WILL INCREASE SLIGHTLY...THOUGH BELIEVE THE GFS/NAM ARE A BIT TOO BULLISH ON THIS. KEPT SLIGHT CHANCE POPS NEXT FEW DAYS FOR THE ATLANTIC COAST...BUT OTHERWISE MOSTLY DRY WEATHER IS EXPECTED TO CONTINUE. MOST CHALLENGING PART OF THE FCST IS AGAIN ON THE LAND BREEZE AND ITS EFFECTS ON TEMPS AGAIN TONIGHT...AND MONDAY NIGHT AS WELL. GFS/NAM AND EVEN THE WRF DO NOT SHOW THE LAND BREEZE DEVELOPING TONIGHT. HOWEVER...THE PATTERN IS NOT CHANGING MUCH AND SO WE BELIEVE IT WILL OCCUR. THE NAM/WRF LOOK WAY TOO AGGRESSIVE WITH WINDS OVERNIGHT...AND THEY START THE DEVELOPMENT OF THE LAND BREEZE EARLY ON BEFORE THE WINDS SURGE TAKES OVER SWITCHING WINDS BACK NE. SINCE THIS SURGE LOOKS TO AGGRESSIVE...DECIDED TO DISCOUNT THIS. GIVEN THE FACT THAT GOOD RADIATIONAL COOLING IS AGAIN EXPECTED IN A STILL RATHER DRY AIRMASS...DECIDED TO BRING THE LAND BREEZE ACROSS MUCH OF THE EAST COAST METRO AREAS AGAIN TONIGHT...BUT NOT QUITE TO THE COAST...REASON BEING THAT IT MADE IT TO THE COAST JUST FOR AN HOUR THIS MORNING...AND ANY SLIGHT INCREASE IN THE NE-E WIND OVERNIGHT WOULD HOLD IT AT BAY. SHOULD MENTION THAT THE RUC IS ACTUALLY FOLLOWING RIGHT ALONG WITH OUR EXPECTATIONS TONIGHT. THE MAIN IMPACT THE FCST ON THE LAND BREEZE HAS IS WITH REGARDS TO TEMPS...AS IT CAN FLUCTUATE 5-10F DEGREES ON EITHER SIDE OF THE BOUNDARY...AS SEEN OVER THE PAST FEW MORNING`S. KEPT PATCHY FOG IN THE FCST TONIGHT AND MON NIGHT. MON NIGHT LOOKS TO BE MOST OPTIMAL...AHEAD OF A PRE-FRONTAL TROUGH. GFS/ECMWF STILL SHOW THE COLD FRONT MOVING ACROSS THE AREA TUESDAY NIGHT INTO WED MORNING...WITH A PRE-FRONTAL TROUGH MOVING BY ON TUESDAY. AFTER TEMPS WARM FINALLY TO NEAR 80 AHEAD OF THE FRONT TUESDAY...A SLIGHT COOL DOWN WILL OCCUR ON WEDNESDAY BEHIND THE FRONT. MOISTURE WILL REMAIN LIMITED...SO MOSTLY DRY WEATHER IS ANTICIPATED. MADE NO CHANGES TO THE EXTENDED FCST. THE DRY NOVEMBER WEATHER PATTERN LOOKS TO CONTINUE. BOTH GFS/ECMWF SHOW A GRADUAL WARMING TREND LATE IN THE WEEK AND INTO NEXT WEEKEND...WITH YET ANOTHER COLD FRONT EXPECTED EITHER SUNDAY OR MONDAY...DEPENDING ON THE MODEL...AND JUST TOO EARLY TO TELL AT THIS POINT IN TIME...BUT THE PARADE OF FRONTS LOOK TO CONTINUE. && .MARINE...DECIDED TO EXTEND THE SMALL CRAFT ADVISORY FOR THE ATLANTIC WATERS THROUGH THIS EVENING...AS GULF STREAM SEAS WILL LIKELY NOT START SUBSIDING UNTIL LATE EVENING AND OVERNIGHT DUE TO THE FACT THAT WINDS WILL REMAIN FROM A MORE NE DIRECTION BEFORE BECOMING EASTERLY LATER TONIGHT. OTHERWISE...WINDS OVER THE NEXT FEW DAYS WILL SLACKEN LEADING TO IMPROVING MARINE CONDITIONS. THE PRE-FRONTAL TROUGH WILL MOVE ACROSS THE AREA TUESDAY...SWITCHING WINDS TO W-NW...AND THE ACTUAL COLD FRONT WILL MOVE ACROSS THE AREA TUE NIGHT INTO EARLY WED MORNING...WITH A BRIEF WIND SURGE EXPECTED BEHIND IT...BUT GUIDANCE SUGGESTS ONLY 15-20 KT AND NOT TOO PROLONGED. && .FIRE WEATHER...RH`S HAVE BEEN DOWN AGAIN TO NEAR 40 PERCENT AS SOME DRY AIR HAS MIXED DOWN. MOISTURE WILL INCREASE JUST A TAD ON MONDAY. SLIGHT DRYING IS EXPECTED TUESDAY BEHIND A PRE-FRONTAL TROUGH...BUT NOT EXPECTED TO BE DRY ENOUGH AT THIS TIME TO RESULT IN CRITICAL RH`S. HOWEVER...WILL MONITOR TRENDS...BECAUSE TUE WILL BE THE WARMEST DAY OF THE WEEK...AND IF MORE DRYING OCCURS BETWEEN THE PRE-FRONTAL TROUGH AND THE ACTUAL COLD FRONT...THEN RH`S COULD FALL LOWER THAN FCST. THE DRIEST AIR WILL ADVECT IN ACROSS THE AREA BEHIND THE FRONT ON WEDNESDAY. TRENDED DEWPOINTS/RH`S DOWN...THOUGH NOT AS LOW AS THE NAM AT THIS TIME...WHICH DROPS DEWPOINTS TO THE LOWER 30S NW INTERIOR TO THE LOWER 40S SE. WE LIKELY WILL NEED TO CONTINUE A DECREASING TREND IN COMING FCSTS. && .PRELIMINARY POINT TEMPS/POPS... WEST PALM BEACH 62 75 60 79 / 20 20 20 10 FORT LAUDERDALE 67 77 62 79 / 20 20 20 10 MIAMI 62 77 62 80 / 20 20 20 10 NAPLES 56 76 61 77 / - 10 10 10 && .MFL WATCHES/WARNINGS/ADVISORIES... FL...NONE. AM...SMALL CRAFT ADVISORY UNTIL 10 PM EST THIS EVENING FOR AMZ650- AMZ651-AMZ670-AMZ671. GM...NONE. && $$ LONG TERM...57/DG SHORT TERM/AVIATION...65/GS fl AREA FORECAST DISCUSSION...CORRECTED NATIONAL WEATHER SERVICE TALLAHASSEE FL 845 AM EST SUN NOV 23 2008 .SYNOPSIS/DISCUSSION... (TODAY AND TONIGHT) 13Z WATER VAPOR AND H4 RUC ANALYSIS SHOWING A RATHER COMPLEX UPPER LEVEL PATTERN OVER NORTH AMERICA THIS MORNING. TWO LARGE UPPER LOWS SPINNING ACROSS WEST-CENTRAL CANADA AND OVER EASTERN QUEBEC ARE THE DOMINANT STEERING MECHANISMS FOR THE NORTHERN STREAM. THIS FLOW DIVES INTO SHORTWAVE ENERGY MOVING INTO THE UPPER PLAINS STATES AROUND THE SOUTHERN PERIPHERY OF THE FIRST MENTIONED UPPER LOW. THE FLOW THEN BRIEFLY RIDGES UP THROUGH THE UPPER MS/VALLEY AND GREAT LAKES STATES BEFORE DIVING SOUTHEAST TO THE MID-ATLANTIC AROUND THE SOUTHERN PERIPHERY OF THE EASTERN CANADIAN UPPER LOW. ABUNDANT SOUTHERN STREAM MOISTURE IS ALSO SEEN ON WV IMAGERY STREAMING NORTHWARD FROM THE BAJA PENINSULA INTO THE SOUTHERN PLAINS. THIS MID-UPPER LEVEL MOISTURE WILL HELP FUEL THE EVOLUTION OF THE SHORTWAVE CURRENTLY APPROACHING THE UPPER PLAINS AS IT AMPLIFIES INTO THE MS VALLEY DURING MONDAY. IN THE LOWER LEVELS...SURFACE RIDGE AXIS EXTENDS FROM THE CAROLINA COAST SOUTHWEST INTO THE FORECAST AREA KEEPING THE GRADIENT RELAXED. WITH THE RIDGE AXIS IN PLACE AND COMBINED WITH DRY LOW LEVELS... EARLY MORNING TEMPERATURES WERE ABLE TO DROP INTO THE UPPER 20S TO MIDDLE 30S OVER A LARGE PORTION OF THE REGION BEFORE INCREASING MID-LEVEL CLOUDS EXPANDED SOUTHEASTWARD AND DISRUPTED THE RADIATIONAL COOLING PROCESS. THIS MID-LEVEL DECK IS RESULTING FROM A ZONE OF LOW LEVEL WARM ADVECTION TO OUR WEST AND CHARACTERIZED BY A RATHER IMPRESSIVE RIDGE OF ISENTROPIC UPGLIDE ALONG THE 290-300K SURFACES. REGIONAL RADARS ARE INDICATING SOME LIGHT SHOWERS/DRIZZLE FALLING OUT OF THIS MID-LEVEL DECK OVER SE ALABAMA AND SOUTHWEST GEORGIA...HOWEVER WITH SURFACE DEWPOINT DEPRESSIONS BETWEEN 10 AND 15 DEGREES...WOULD NOT ANTICIPATE ANY MEASURABLE RAINFALL REACHING THE SURFACE. GFS/NAM IS AGREEMENT SHOWING THIS FEATURE SLOWLY WEAKENING THROUGH THE DAY WHILE KEEPING THE RESULTING LIFT AND BEST CLOUD COVERAGE OVER THE NW HALF OF THE AREA. WITH THE SUN NOW UP...TEMPERATURES ARE ON THE RISE AREA-WIDE. UNDER THE PARTLY TO MOSTLY CLOUDY MID-LEVEL DECK OVER THE NW ZONES TEMPS WILL BE A BIT COOLER TOPPING OUT IN THE UPPER 50S TO NEAR 60. FURTHER SOUTHEAST UNDER PARTLY SUNNY SKIES...AFTERNOON HIGHS SHOULD EASILY REACH THE LOWER AND MIDDLE 60S. SURFACE RIDGE WILL STILL BE IN CONTROL OF THE AREA TONIGHT...HOWEVER IT WILL BE WEAKENING. EASTERLY FLOW WILL BE SLOWLY COMING AROUND TO THE SOUTHEAST WITH TIME ALLOWING FOR A STEADY INCREASE IN LOW LEVEL MOISTURE. THIS MOISTURE ADVECTION COMBINED WITH AT LEAST PARTLY CLOUDY SKIES SHOULD RESULT IN A MUCH WARMER OVERNIGHT PERIOD THAN HAS BEEN EXPERIENCED THE PAST SEVERAL NIGHTS. IN FACT LOW TEMPERATURES TONIGHT SHOULD BOTTOM OUT IN THE LOWER 40S FOR THE COLDEST LOCATIONS WITH UPPER 40S AND LOWER 50S ALONG THE COAST FROM FRANKLIN COUNTY TO THE FLORIDA PANHANDLE. && .MARINE... SURFACE HIGH PRESSURE REMAINS TO OUR NORTHEAST THROUGH THE NEXT 24 HOURS WHILE SLOWLY WEAKENING ITS INFLUENCE ON THE MARINE AREA. WINDS EXPECTED TO CONTINUE FROM THE NORTHEAST IN ROUGHLY THE 10 TO 15 KNOT RANGE ALTHOUGH EXPECT WINDS TO DECREASE DURING THE AFTERNOON OVER APALACHEE BAY TO THE 5 TO 10 KNOT RANGE. SEAS REMAIN IN THE 2 TO 3 FOOT RANGE AWAY FROM THE COAST. AS THE HIGH WEAKENS OVERNIGHT SHOULD SEE THE FLOW COME AROUND TO THE EAST AND SOUTHEAST. A COLD FRONT WILL THEN APPROACH FROM THE WEST ON MONDAY CROSSING THE FORECAST WATERS MONDAY NIGHT AND TUESDAY MORNING WITH A SHARP WIND SHIFT TO THE NORTH. A PERIOD OF ADVISORY LEVEL WINDS IS POSSIBLE TUESDAY AND TUESDAY NIGHT IN THE WAKE OF THIS FRONT BEFORE HIGH PRESSURE BUILDS SOUTH TOWARD THE AREA WEDNESDAY AND THURSDAY. && .AVIATION... VFR CONDITIONS EXPECTED TO PREVAIL INTO THE EVENING HOURS. BAND OF MID-LEVEL AC BETWEEN 6 AND 12KFT CONTINUES TO SLOWLY PROGRESS SOUTHEAST ACROSS THE AREA AND WILL BE THE MAIN AVIATION CONCERN OVER THE NEXT 12 HOURS. A FEW SPRINKLES CAN NOT BE RULED OUT WITH THIS BAND OF CLOUDS...ESPECIALLY FROM KDHN TO KABY AND ESPECIALLY THIS MORNING. HOWEVER...WITH FAIRLY DRY LOW LEVELS STILL IN PLACE...ANY PRECIPITATION THAT DOES REACH THE SURFACE SHOULD BE VERY LIGHT AND MEASURABLE RAINFALL IS NOT EXPECTED. && .FIRE WEATHER...ASIDE FROM THE POTENTIAL FOR BRIEF 1 TO 2 HR DURATIONS OF RH LESS THAN 35 PERCENT IN WELL INLAND NORTH FLORIDA THIS AFTERNOON...CRITICAL RH VALUES ARE NOT EXPECTED UNTIL TUESDAY AFTERNOON. THE COMBINATION OF AN INCOMING DRY AIRMASS AND WINDY CONDITIONS MAY ALLOW RED FLAG CRITERIA TO BE MET TUESDAY AFTERNOON IN PORTIONS OF NORTH FLORIDA. THIS WILL CONTINUE TO BE MONITORED. && .PRELIMINARY POINT TEMPS/POPS... TALLAHASSEE 63 42 68 50 66 / 0 0 20 30 05 PANAMA CITY 63 48 68 54 65 / 0 0 40 40 05 DOTHAN 57 44 64 47 64 / 0 0 60 40 0 ALBANY 58 40 64 47 64 / 0 0 40 40 0 VALDOSTA 61 42 68 48 65 / 0 0 10 30 05 CROSS CITY 68 43 74 51 69 / 0 0 05 20 20 && .TAE WATCHES/WARNINGS/ADVISORIES... AL...NONE. GA...NONE. FL...NONE. GM...NONE. && $$ FIRE WEATHER...GOULD REST OF DISCUSSION...MROCZKA fl AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TALLAHASSEE FL 1026 PM EST SAT NOV 22 2008 .UPDATE...THE EVENING SURFACE ANALYSIS SHOWED A HIGH PRESSURE CENTERED NORTHEAST OF THE LOCAL FORECAST AREA WITH A RIDGE AXIS EXTENDING SOUTHWEST ACROSS THE REGION. IR2 IMAGERY AND OBSERVATIONS SHOW A MID-LEVEL CLOUD DECK AROUND 10 KFT SHIFTING SOUTHEAST TOWARD OUR SOUTHEAST ALABAMA COUNTIES THIS EVENING. AS A RESULT...WE DID AN UPDATE TO THE ZONES/GRIDS TO REFLECT THIS COVERAGE OVER SOUTHEAST ALABAMA AND PORTIONS OF THE EASTERN FLORIDA PANHANDLE AROUND MIDNIGHT. ALSO DECREASED THE AREAS OF FROST TO PATCHY OVER THESE AREAS AND SLIGHTLY INCREASED THE OVERNIGHT LOWS OVER THESE COUNTIES. THE NAM12 PICKED UP ON THIS INCREASE IN MID-LEVEL MOISTURE LATER TONIGHT AS WELL. KTLH TEMPERATURE DROPPED FROM 49 TO 34 DEGREES OVER A TWO HOUR PERIOD THIS EVENING...WHICH IS A LITTLE FASTER THAN PREVIOUSLY FORECAST. THERE IS A DECENT DEWPOINT GRADIENT ACROSS THE SOUTHEASTERN BIG BEND AND TEMPERATURES AT PERRY AND CROSS CITY ARE STILL IN THE MID 40S. THE RUC SHOWS THESE HIGHER DEWPOINTS SPREADING NORTHWEST THROUGH THE REMAINDER OF THE NIGHT. THEREFORE...EXPECT THE DECREASING TEMPERATURE RATE TO LEVEL OFF THROUGH THE LATE NIGHT HOURS. .AVIATION...VFR CONDITIONS WITH UNLIMITED VISIBILITIES WILL CONTINUE WITH LIGHT EASTERLY WINDS POSSIBLY GOING CALM DURING THE PREDAWN HOURS. SLOWLY INCREASING MOISTURE IS EXPECTED TO ALLOW FEW-SCT CLOUDS TO REACH KVLD AND KTLH AFTER MIDNIGHT. HIGH PRESSURE REMAINS TO OUR NORTHEAST THROUGH SUNDAY WITH GENERALLY LIGHT WINDS AND ONLY FEW-SCT CLOUDS BETWEEN 3-4KFT. && .TAE WATCHES/WARNINGS/ADVISORIES... AL...NONE. GA...NONE. FL...NONE. GM...NONE. && $$ UPDATE...GIBBS AVIATION...BLOCK fl AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE PEACHTREE CITY GA 629 PM EST SAT NOV 22 2008 .UPDATE... WELL...THIS CLOUDINESS ASSOCIATED WITH THE BELOW-MENTIONED SHORTWAVE IS COMING IN A LITTLE MORE THAN EXPECTED. WILL SEND OUT AN UPDATE FOR BOTH SKY GRIDS AND MIN TEMPERATURE GRIDS. AM NOT QUITE SURE HOW EXACTLY TO HANDLE MIN TEMPERATURES. TEMPS ALREADY DROPPING FAIRLY RAPIDLY BUT THE CLOUD COVER...WHICH ACCORDING TO BOTH THE RUC AND NAM12 SHOULD STAY IN A GOOD PORTION OF THE AREA ALL NIGHT...WOULD INHIBIT THE AMOUNT OF RADIATIONAL COOLING THAT WAS EARLIER EXPECTED. TOOK A GENERAL BLEND OF THE MAV AND THE MET FROM EARLIER TODAY ALONG WITH SOME NEW TEMPERATURE DATA... HOPEFULLY IT ISN`T TOO MUCH OF A BUST ONE WAY OR ANOTHER. DIDN`T DO MUCH ADJUSTING OF SOUTHERN ZONES AS IT`LL TAKE A WHILE FOR THE CLOUDS TO GET THERE AND BY THAT POINT THE CLOUDS MAY BREAK UP. ALSO...RFW FOR TODAY EXPIRES IN A LITTLE OVER HALF AN HOUR...SO WILL SEND THAT EXPIRATION STATEMENT SOON. TDP && .PREV DISCUSSION... /ISSUED 540 PM EST SAT NOV 22 2008/ SHORT TERM /TONIGHT THROUGH MONDAY NIGHT/... COLD...DRY HIGH PRESSURE IN PLACE OVER THE REGION. ANOTHER COLD NIGHT IN STORE FOR THE AREA...THOUGH AS THE AIRMASS IS MODIFYING SOMEWHAT IT SHOULDN`T BE QUITE AS COLD AS LAST NIGHT. NONETHELESS HAVE GONE ON THE COOL SIDE OF GUIDANCE...GENERALLY WITH EITHER THE MAV OR FWC (AS A NOTE...FWC BEAT THE TAR OUT OF BOTH THE MAV AND MET LAST NIGHT). LIMITING FACTOR WILL BE THE WEAK SHORTWAVE IN THE FLOW ALOFT THAT MIGHT BRING SOME MID-LEVEL CLOUDINESS TO THE REGION...ESPECIALLY ACROSS NORTH GEORGIA. AM NOT TOO EXCITED ABOUT THIS BUT JUST THE MERE PRESENCE OF THE SHORTWAVE STIRRING UP SOME MID-LEVEL MOISTURE...THE LACK OF COMPLETE SUBSIDENCE WILL KEEP US FROM BEING AS FRIGID AS LAST NIGHT. THE HIGH BEGINS TO PUSH OFF THE SOUTHEAST COAST ON MONDAY AND WE GET SOME RETURN MOISTURE...NOT A WHOLE LOT THOUGH...TO THE REGION LATE ON SUNDAY. UPPER TROUGH PUSHES OFF THE ROCKIES DURING THE DAY ON SUNDAY AND WILL BEGIN TO WORK ITS WAY EAST. SHOULD WARM UP A BIT DURING THE DAY...STILL BELOW NORMAL BUT AT LEAST IN THE 50S JUST ABOUT EVERYWHERE...PUSHING 60 IN SOUTHERN ZONES. MONDAY NIGHT STARTS GETTING TRICKY AS FAR AS PRECIP GOES. CLOUD COVER MOVING IN AHEAD OF THE FRONT WILL PREVENT US FROM GETTING AS COLD AS PREVIOUS NIGHTS...AND PRECIP SHOULD NOT MOVE INTO NORTHWEST GEORGIA UNTIL CLOSE TO SUNRISE. HOWEVER...AT LEAST IN THE MOUNTAINS...TEMPS SHOULD STILL DROP BELOW FREEZING. IT IS POSSIBLE...AS HAS BEEN INCLUDED IN THE GRIDS WITH THIS PACKAGE... THAT RAIN MAY MIX WITH SNOW OR SLEET IN THE MOUNTAINS EARLY MONDAY MORNING. GFS BUFR SOUNDINGS DO INDICATE A SLIGHT WARM NOSE SO AM INCLINED TO LEAN TOWARD SLEET...HOWEVER IF THE PROFILE HUGS THE FREEZING LINE ENOUGH OR IF PRECIP RATES ARE HIGH ENOUGH IT`S POSSIBLE IT COULD BRIEFLY CHANGE OVER TO SNOW. TOO EARLY TO TELL AND IN ANY CASE NO ACCUMULATIONS ARE EXPECTED WITH THE GROUND TEMPS TOO WARM FOR NOW...BUT WILL ADJUST AS NECESSARY AS THE FORECAST WARRANTS. THE FRONT PUSHES THROUGH DURING THE DAY ON MONDAY AND MONDAY NIGHT. NOT SEEING A HUGE CHANCE OF WRAPAROUND SNOW SHOWERS MONDAY NIGHT IN THE MOUNTAINS AS THIS SHOULD MOVE THROUGH MONDAY EVENING BEFORE TEMPERATURES DROP. BUT IF ANY PRECIP ENDS UP LINGERING THROUGH TUESDAY MORNING THIS COULD CHANGE. HAVE LEFT IT OUT FOR NOW. OVERALL NOT A HUGE RAIN MAKER...BUT WE`LL TAKE ANYTHING WE CAN GET AT THIS POINT. LONG TERM /TUESDAY THROUGH SATURDAY/... PRECIP LINGERS IN SOUTHERN ZONES THROUGH TUESDAY MORNING BEFORE THE FRONT COMPLETELY MOVES THROUGH. UPPER LOW SPINS OVER NEW ENGLAND FOR A COUPLE OF DAYS LEAVING US IN NORTHWEST FLOW ALOFT AS ANOTHER COOL HIGH MOVES INTO PLACE. TEMPS BELOW NORMAL FOR MOST OF THE WEEK. ANOTHER UPPER SYSTEM DIGS INTO THE CENTRAL PLAINS LATE INT HE WEEK AS A LEE LOW DEVELOPS...DRAGGING A FRONT ACROSS THE SOUTHERN PLAINS. AS MENTIONED YESTERDAY...THIS LOOKS LIKE A PRETTY INTERESTING SETUP FOR THE CENTRAL PLAINS INTO THE OHIO VALLEY AS FAR AS WINTER WEATHER GOES. GFS A LITTLE FASTER THAN THE ECMWF AND A LITTLE FURTHER NORTH THAN ITS PREVIOUS RUN. CONFIDENCE NOT HIGH IN THE EXACT SOLUTION BUT THE PATTERN SEEMS TO INDICATE THAT A FRONT WILL BE SWEEPING THROUGH THE MID SOUTH AND INTO OUR AREA OVER THE WEEKEND. FIRE WEATHER... WITH THE HIGH PRESSURE FIRMLY IN PLACE TODAY...RED FLAG WARNING CONTINUES THIS AFTERNOON. HIGH PRESSURE SLIDES EAST ON SUNDAY AND MOISTURE BEGINS RETURNING TO PORTIONS OF SOUTH GEORGIA...BUT DRY AIR CONTINUES IN NORTH GEORGIA. HAVE OPTED TO UPGRADE THE WATCH TO A WARNING IN PORTIONS OF NORTH GEORGIA...BUT CANCEL THE WATCH FOR CENTRAL GEORGIA AS HUMIDITIES SHOULD BE A LITTLE TOO HIGH IN THOSE AREAS. TDP AVIATION... LATEST SATL SHOWS A BLANKET OF HIGH MID LEVEL CLOUDS APPROACHING FROM THE WEST...ASSOCIATED WITH A SHARP SHORT-WAVE EMBEDDED WITHIN THE NW FLOW ALOFT. TIMING TOOL SUGGEST CLOUDS IN THE OVC080 TO OVC100 RANGE WILL PUSH INTO THE ATL AREA BETWEEN 00-02Z. BOTH NAM-WRF, NAM12 AND RUC13 ALL SUGGESTS CLOUDS WILL PERSIST AND EVEN LOWER A BIT TO AROUND BKN060 THROUGH 12Z...THEN LIKELY SCATTERED. OTHERWISE...EXPECT A LIGHT SE WIND WILL PREVAIL THROUGH THE FORECAST PERIOD. 39 && .PRELIMINARY POINT TEMPS/POPS... ATHENS 23 55 31 55 38 / 0 0 5 50 20 ATLANTA 29 55 39 56 40 / 0 0 5 50 20 BLAIRSVILLE 20 48 26 50 33 / 0 0 10 60 20 CARTERSVILLE 22 55 33 53 35 / 0 0 10 50 20 COLUMBUS 26 62 38 61 44 / 0 0 5 40 20 GAINESVILLE 25 52 35 51 39 / 0 0 5 50 20 MACON 24 58 34 64 42 / 0 0 5 40 20 ROME 23 55 32 54 39 / 0 0 10 50 20 PEACHTREE CITY 22 57 28 57 39 / 0 0 5 50 20 VIDALIA 25 58 32 66 39 / 0 0 0 20 20 && .FFC WATCHES/WARNINGS/ADVISORIES... RED FLAG WARNING FROM 12 PM TO 7 PM EST SUNDAY FOR PORTIONS OF NORTH GEORGIA. && $$ TDP ga AREA FORECAST DISCUSSION...UPDATED FOR AVIATION NATIONAL WEATHER SERVICE PEACHTREE CITY GA 540 PM EST SAT NOV 22 2008 .SHORT TERM /TONIGHT THROUGH MONDAY NIGHT/... COLD...DRY HIGH PRESSURE IN PLACE OVER THE REGION. ANOTHER COLD NIGHT IN STORE FOR THE AREA...THOUGH AS THE AIRMASS IS MODIFYING SOMEWHAT IT SHOULDN`T BE QUITE AS COLD AS LAST NIGHT. NONETHELESS HAVE GONE ON THE COOL SIDE OF GUIDANCE...GENERALLY WITH EITHER THE MAV OR FWC (AS A NOTE...FWC BEAT THE TAR OUT OF BOTH THE MAV AND MET LAST NIGHT). LIMITING FACTOR WILL BE THE WEAK SHORTWAVE IN THE FLOW ALOFT THAT MIGHT BRING SOME MID-LEVEL CLOUDINESS TO THE REGION...ESPECIALLY ACROSS NORTH GEORGIA. AM NOT TOO EXCITED ABOUT THIS BUT JUST THE MERE PRESENCE OF THE SHORTWAVE STIRRING UP SOME MID-LEVEL MOISTURE...THE LACK OF COMPLETE SUBSIDENCE WILL KEEP US FROM BEING AS FRIGID AS LAST NIGHT. THE HIGH BEGINS TO PUSH OFF THE SOUTHEAST COAST ON MONDAY AND WE GET SOME RETURN MOISTURE...NOT A WHOLE LOT THOUGH...TO THE REGION LATE ON SUNDAY. UPPER TROUGH PUSHES OFF THE ROCKIES DURING THE DAY ON SUNDAY AND WILL BEGIN TO WORK ITS WAY EAST. SHOULD WARM UP A BIT DURING THE DAY...STILL BELOW NORMAL BUT AT LEAST IN THE 50S JUST ABOUT EVERYWHERE...PUSHING 60 IN SOUTHERN ZONES. MONDAY NIGHT STARTS GETTING TRICKY AS FAR AS PRECIP GOES. CLOUD COVER MOVING IN AHEAD OF THE FRONT WILL PREVENT US FROM GETTING AS COLD AS PREVIOUS NIGHTS...AND PRECIP SHOULD NOT MOVE INTO NORTHWEST GEORGIA UNTIL CLOSE TO SUNRISE. HOWEVER...AT LEAST IN THE MOUNTAINS...TEMPS SHOULD STILL DROP BELOW FREEZING. IT IS POSSIBLE...AS HAS BEEN INCLUDED IN THE GRIDS WITH THIS PACKAGE... THAT RAIN MAY MIX WITH SNOW OR SLEET IN THE MOUNTAINS EARLY MONDAY MORNING. GFS BUFR SOUNDINGS DO INDICATE A SLIGHT WARM NOSE SO AM INCLINED TO LEAN TOWARD SLEET...HOWEVER IF THE PROFILE HUGS THE FREEZING LINE ENOUGH OR IF PRECIP RATES ARE HIGH ENOUGH IT`S POSSIBLE IT COULD BRIEFLY CHANGE OVER TO SNOW. TOO EARLY TO TELL AND IN ANY CASE NO ACCUMULATIONS ARE EXPECTED WITH THE GROUND TEMPS TOO WARM FOR NOW...BUT WILL ADJUST AS NECESSARY AS THE FORECAST WARRANTS. THE FRONT PUSHES THROUGH DURING THE DAY ON MONDAY AND MONDAY NIGHT. NOT SEEING A HUGE CHANCE OF WRAPAROUND SNOW SHOWERS MONDAY NIGHT IN THE MOUNTAINS AS THIS SHOULD MOVE THROUGH MONDAY EVENING BEFORE TEMPERATURES DROP. BUT IF ANY PRECIP ENDS UP LINGERING THROUGH TUESDAY MORNING THIS COULD CHANGE. HAVE LEFT IT OUT FOR NOW. OVERALL NOT A HUGE RAIN MAKER...BUT WE`LL TAKE ANYTHING WE CAN GET AT THIS POINT. .LONG TERM /TUESDAY THROUGH SATURDAY/... PRECIP LINGERS IN SOUTHERN ZONES THROUGH TUESDAY MORNING BEFORE THE FRONT COMPLETELY MOVES THROUGH. UPPER LOW SPINS OVER NEW ENGLAND FOR A COUPLE OF DAYS LEAVING US IN NORTHWEST FLOW ALOFT AS ANOTHER COOL HIGH MOVES INTO PLACE. TEMPS BELOW NORMAL FOR MOST OF THE WEEK. ANOTHER UPPER SYSTEM DIGS INTO THE CENTRAL PLAINS LATE INT HE WEEK AS A LEE LOW DEVELOPS...DRAGGING A FRONT ACROSS THE SOUTHERN PLAINS. AS MENTIONED YESTERDAY...THIS LOOKS LIKE A PRETTY INTERESTING SETUP FOR THE CENTRAL PLAINS INTO THE OHIO VALLEY AS FAR AS WINTER WEATHER GOES. GFS A LITTLE FASTER THAN THE ECMWF AND A LITTLE FURTHER NORTH THAN ITS PREVIOUS RUN. CONFIDENCE NOT HIGH IN THE EXACT SOLUTION BUT THE PATTERN SEEMS TO INDICATE THAT A FRONT WILL BE SWEEPING THROUGH THE MID SOUTH AND INTO OUR AREA OVER THE WEEKEND. && .FIRE WEATHER... WITH THE HIGH PRESSURE FIRMLY IN PLACE TODAY...RED FLAG WARNING CONTINUES THIS AFTERNOON. HIGH PRESSURE SLIDES EAST ON SUNDAY AND MOISTURE BEGINS RETURNING TO PORTIONS OF SOUTH GEORGIA...BUT DRY AIR CONTINUES IN NORTH GEORGIA. HAVE OPTED TO UPGRADE THE WATCH TO A WARNING IN PORTIONS OF NORTH GEORGIA...BUT CANCEL THE WATCH FOR CENTRAL GEORGIA AS HUMIDITIES SHOULD BE A LITTLE TOO HIGH IN THOSE AREAS. && .AVIATION... LATEST SATL SHOWS A BLANKET OF HIGH MID LEVEL CLOUDS APPROACHING FROM THE WEST...ASSOCIATED WITH A SHARP SHORT-WAVE EMBEDDED WITHIN THE NW FLOW ALOFT. TIMING TOOL SUGGEST CLOUDS IN THE OVC080 TO OVC100 RANGE WILL PUSH INTO THE ATL AREA BETWEEN 00-02Z. BOTH NAM-WRF, NAM12 AND RUC13 ALL SUGGESTS CLOUDS WILL PERSIST AND EVEN LOWER A BIT TO AROUND BKN060 THROUGH 12Z...THEN LIKELY SCATTERED. OTHERWISE...EXPECT A LIGHT SE WIND WILL PREVAIL THROUGH THE FORECAST PERIOD. 39 && .PRELIMINARY POINT TEMPS/POPS... ATHENS 23 55 31 55 38 / 0 0 5 50 20 ATLANTA 28 55 39 56 40 / 0 0 5 50 20 BLAIRSVILLE 19 48 26 50 33 / 0 0 10 60 20 CARTERSVILLE 20 55 33 53 35 / 0 0 10 50 20 COLUMBUS 26 62 38 61 44 / 0 0 5 40 20 GAINESVILLE 25 52 35 51 39 / 0 0 5 50 20 MACON 22 58 34 64 42 / 0 0 5 40 20 ROME 18 55 32 54 39 / 0 0 10 50 20 PEACHTREE CITY 20 57 28 57 39 / 0 0 5 50 20 VIDALIA 24 58 32 66 39 / 0 0 0 20 20 && .FFC WATCHES/WARNINGS/ADVISORIES... RED FLAG WARNING UNTIL 7 PM EST THIS EVENING FOR ALL OF NORTH AND CENTRAL GEORGIA. RED FLAG WARNING FROM 12 PM TO 7 PM EST SUNDAY FOR PORTIONS OF NORTH GEORGIA. && $$ TDP ga AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BOISE ID 914 AM MST SUN NOV 23 2008 .DISCUSSION...AT 15Z DENSE FOG WAS NEARLY CONTINUOUS IN THE SNAKE BASIN FROM ONO TO BETWEEN MUO AND JER. 12Z KBOI RAOB SHOWED THE CLASSIC SIGNATURE...FOG TOP ONLY NEAR 4000 FEET MSL AND BLUE SKY FAINTLY VISIBLE THROUGH IT. RAOB SHOWED NW WINDS ALL THE WAY UP WHICH IS FAVORABLE FOR FOG TO CONTINUE. WE WILL STAY WITH OUR DENSE FOG ADVISORY THROUGH 18Z AFTER WHICH WE EXPECT SOME IMPROVEMENT. FOG WILL RE-FORM TONIGHT BUT SURFACE WINDS WILL BECOME SELY WHICH SHOULD KEEP IT MOSTLY IN THE LOWER TREASURE VALLEY. LESS FOG EXPECTED MONDAY IN UPPER TREASURE VALLEY AS SE WINDS CONTINUE. MAX TEMPS TODAY WILL PROBABLY NOT MAKE 40 DEGS IN THE FOGGIER AREAS...WE WILL UPDATE COOLER. ELSEWHERE...MOSTLY CLEAR AND MILD UNDER LONG WAVE UPPER RIDGE WHICH HAS REBUILT BEHIND YESTERDAY/S TROUGH AND WEAK COLD FRONT. && .AVIATION...VLIFR CONDITIONS AT KBOI THIS MORNING. KBOI SOUNDING SHOWING TOP OF FOG LAYER AT ABOUT 1000 FEET AGL. AS OF 1600Z HINT OF BLUE SKY WAS VISIBLE ON NORTH SIDE OF RUNWAY. WITH WINDS NOT EXPECTED TO INCREASE UNTIL AROUND 20Z THIS AFTERNOON ANY IMPROVEMENT IN CONDITIONS WILL BE FROM SUN. AND GIVEN LOW SUN ANGLE...80 PERCENT CONFIDENT THAT VISIBILITY REMAINS LESS THAN ONE MILE WITH CEILINGS AT OR BELOW 200FT AGL THROUGH 19Z. ONCE SE WIND DEVELOPS EXPECT CONDITIONS TO IMPROVE RAPIDLY TO VFR. WIDESPREAD IFR-VLIFR CONDITIONS FROM LOW STRATUS AND FOG THROUGHOUT SE OREGON AND SW IDAHO THIS MORNING WILL GRADUALLY IMPROVE TO VFR BY 20Z. OTHER THAN FOG...FEW HIGH CLOUDS AND LIGHT WINDS. EXPECT MOUNTAIN VALLEY FOG TO REDEVELOP TONIGHT. FAIRLY CONFIDENT THAT KBOI REMAINS VFR TONIGHT DUE TO STEADY SOUTHEAST WINDS. && ,PREV DISCUSSION... SHORT TERM...TODAY THROUGH MONDAY...DENSE FOG IS THE MAIN FORECAST ISSUE THIS MORNING. AT 09Z...DENSE FOG EXTENDED FROM CALDWELL THROUGH BOISE...MOUNTAIN HOME AND INTO JEROME. SURFACE HIGH BUILDING EAST JUST NORTH OF THE FORECAST AREA AS KEPT LIGHT NORTHWEST WINDS IN THE VALLEY. THUS...FOG/STRATUS HAS SPREAD SE INTO THE WESTERN MAGIC VALLEY AND REMAINS OUT OF MOST OF THE LOWER TREASURE VALLEY. ANALYSIS OF FORECAST SOUNDINGS AND SURFACE FEATURES SHOW GOOD AGREEMENT WITH FOG/STRATUS SHIFTING DOWN THE VALLEY INTO LOWER TREASURE VALLEY STARTING AT 18Z BEFORE LIFTING OUT BY AFTER 21Z. THIS IS BASED ON PLACEMENT OF THE SURFACE HIGH WHICH IS FORECASTS TO MOVE INTO CENTRAL IDAHO BY 18Z THIS AFTERNOON. THIS SHOULD SETUP A SE/NW PRESSURE GRADIENT FOR SOUTHEAST WINDS IN THE VALLEY. APPROACHING UPPER LEVEL TROUGH TOWARDS THE WEST COAST SHOULD FURTHER TIGHTEN THE GRADIENT FOR LIGHT SE WINDS IN THE BOUNDARY LAYER TONIGHT. ALSO...MODEL SOUNDINGS INDICATING QUITE A BIT OF DRYING ALOFT UNDERNEATH THE UPPER RIDGE. THE RUC AND NAM SOUNDINGS SHOW THE DRY AIR DESCENDING TOWARDS THE TOP OF THE INVERSION NEAR 800 MB BY 18Z WHICH IS A GOOD INDICATION FOR THE DISSIPATION OF THE STRATUS DECK. BASED ON THIS...WILL ADD THE WESTERN MAGIC VALLEY TO THE DENSE FOG ADVISORY UNTIL 18Z TODAY. FOG/STRATUS SHOULD BEGIN TO LIFT BY 18Z MOVING INTO THE LOWER TREASURE. HAVE FORECAST STRATUS TO DISSIPATE IN THE LOWER TREASURE VALLEY BY 21Z THIS AFTERNOON. DAY SHIFT WILL HAVE TO MONITOR SURFACE HIGH LOCATION AND VALLEY WINDS TO SEE IF DENSE FOG ADVISORY MAY NEEDS SOME TIMING ADJUSTMENTS. HAVE LOWERED TEMPERATURES ALONG WITH GUIDANCE AS STRATUS/FOG WILL LIMIT SURFACE HEATING TODAY. SLIGHTLY WARMER ON MONDAY AS LIGHT SOUTHEAST WINDS AHEAD OF THE UPPER TROUGH OFF THE WEST COAST SHOULD INCREASE TEMPS 2 TO 3 DEGREES ABOVE TODAYS HIGH. PATCHY FOG TONIGHT...MAINLY IN SHELTERED MOUNTAIN VALLEYS AND THE LOWER TREASURE VALLEY AS SOUTHEAST WINDS SHOULD KEEP THE BOUNDARY LAYER MIXED ENOUGH IN THE UPPER TREASURE AND WESTERN MAGIC VALLEY. LONG TERM...MONDAY NIGHT THROUGH SUNDAY...MODELS CONTINUE TO SHOW A SPLIT FLOW PATTERN EVOLVING OVER THE WESTERN UNITED STATES DURING THE UPCOMING WEEK. BUT FIRST EARLY IN THE WEEK...A HIGH AMPLITUDE RIDGE WILL DOMINATE THE FORECAST AREA MONDAY THROUGH MUCH OF TUESDAY AS A DEEP CLOSED LOW DEVELOPS OVER THE EASTERN UNITED STATES. THIS UPPER RIDGE IN OUR AREA SPELLS INVERSION CONDITIONS BUT IT IS NOT EXPECTED TO BE A LONG LASTING EVENT WITH THE SPLIT AND NEW CLOSED LOW MOVING IN LATER IN THE WEEK. WITH SUCH A BLOCKY PATTERN DEVELOPING ACROSS CONUS DURING THE UPCOMING HOLIDAY WEEK...BELIEVE FEATURES WILL BE BOTH SLOWER TO EVOLVE AND BREAK DOWN. EVEN THOUGH THE OPERATIONAL MODELS FAVOR A SPLIT FLOW IN THE WEST...THERE ARE CONSIDERABLE DIFFERENCES IN THE PLACEMENT OF THE PARENT CLOSED LOW. GFS TAKES THIS SYSTEM MUCH FARTHER SOUTH ACROSS SOUTHERN CALIFORNIA WHILE THE NAM SOLUTION HAS THE LOW FARTHER NORTH IN THE CENTRAL GREAT BASIN. IMPLICATIONS ARE SIGNIFICANT IN THAT NAM SOLUTION WOULD BRING WET WEATHER AND TRAVEL IMPLICATIONS INTO OUR AREA FOR THE HOLIDAY...WHILE THE GFS WOULD KEEP DRY WEATHER IN THE REGION. A QUICK LOOK AT THE NEW ECMWF WOULD ALSO FAVOR A MORE SOUTHERN TRACK LIKE THE GFS. HAVE KEPT CLIMO POPS GOING IN THIS TIME FRAME DUE TO THE UNCERTAINTY IN THIS IMPORTANT LONG RANGE TRAVEL PERIOD. && .BOI WATCHES/WARNINGS/ADVISORIES... ID...DENSE FOG ADVISORY UNTIL 11 AM MST THIS MORNING FOR IDZ016 IDZ012-IDZ014. OR...NONE. && $$ WEATHER.GOV/BOISE DISCUSSION...LC AVIATION.....DG PREV SHORT TERM...JDS PREV LONG TERM....GS id AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BOISE ID 314 AM MST SUN NOV 23 2008 .SHORT TERM...TODAY THROUGH MONDAY...DENSE FOG IS THE MAIN FORECAST ISSUE THIS MORNING. AT 09Z...DENSE FOG EXTENDED FROM CALDWELL THROUGH BOISE...MOUNTAIN HOME AND INTO JEROME. SURFACE HIGH BUILDING EAST JUST NORTH OF THE FORECAST AREA AS KEPT LIGHT NORTHWEST WINDS IN THE VALLEY. THUS...FOG/STRATUS HAS SPREAD SE INTO THE WESTERN MAGIC VALLEY AND REMAINS OUT OF MOST OF THE LOWER TREASURE VALLEY. ANALYSIS OF FORECAST SOUNDINGS AND SURFACE FEATURES SHOW GOOD AGREEMENT WITH FOG/STRATUS SHIFTING DOWN THE VALLEY INTO LOWER TREASURE VALLEY STARTING AT 18Z BEFORE LIFTING OUT BY AFTER 21Z. THIS IS BASED ON PLACEMENT OF THE SURFACE HIGH WHICH IS FORECASTS TO MOVE INTO CENTRAL IDAHO BY 18Z THIS AFTERNOON. THIS SHOULD SETUP A SE/NW PRESSURE GRADIENT FOR SOUTHEAST WINDS IN THE VALLEY. APPROACHING UPPER LEVEL TROUGH TOWARDS THE WEST COAST SHOULD FURTHER TIGHTEN THE GRADIENT FOR LIGHT SE WINDS IN THE BOUNDARY LAYER TONIGHT. ALSO...MODEL SOUNDINGS INDICATING QUITE A BIT OF DRYING ALOFT UNDERNEATH THE UPPER RIDGE. THE RUC AND NAM SOUNDINGS SHOW THE DRY AIR DESCENDING TOWARDS THE TOP OF THE INVERSION NEAR 800 MB BY 18Z WHICH IS A GOOD INDICATION FOR THE DISSIPATION OF THE STRATUS DECK. BASED ON THIS...WILL ADD THE WESTERN MAGIC VALLEY TO THE DENSE FOG ADVISORY UNTIL 18Z TODAY. FOG/STRATUS SHOULD BEGIN TO LIFT BY 18Z MOVING INTO THE LOWER TREASURE. HAVE FORECAST STRATUS TO DISSIPATE IN THE LOWER TREASURE VALLEY BY 21Z THIS AFTERNOON. DAY SHIFT WILL HAVE TO MONITOR SURFACE HIGH LOCATION AND VALLEY WINDS TO SEE IF DENSE FOG ADVISORY MAY NEEDS SOME TIMING ADJUSTMENTS. HAVE LOWERED TEMPERATURES ALONG WITH GUIDANCE AS STRATUS/FOG WILL LIMIT SURFACE HEATING TODAY. SLIGHTLY WARMER ON MONDAY AS LIGHT SOUTHEAST WINDS AHEAD OF THE UPPER TROUGH OFF THE WEST COAST SHOULD INCREASE TEMPS 2 TO 3 DEGREES ABOVE TODAYS HIGH. PATCHY FOG TONIGHT...MAINLY IN SHELTERED MOUNTAIN VALLEYS AND THE LOWER TREASURE VALLEY AS SOUTHEAST WINDS SHOULD KEEP THE BOUNDARY LAYER MIXED ENOUGH IN THE UPPER TREASURE AND WESTERN MAGIC VALLEY. .LONG TERM...MONDAY NIGHT THROUGH SUNDAY...MODELS CONTINUE TO SHOW A SPLIT FLOW PATTERN EVOLVING OVER THE WESTERN UNITED STATES DURING THE UPCOMING WEEK. BUT FIRST EARLY IN THE WEEK...A HIGH AMPLITUDE RIDGE WILL DOMINATE THE FORECAST AREA MONDAY THROUGH MUCH OF TUESDAY AS A DEEP CLOSED LOW DEVELOPS OVER THE EASTERN UNITED STATES. THIS UPPER RIDGE IN OUR AREA SPELLS INVERSION CONDITIONS BUT IT IS NOT EXPECTED TO BE A LONG LASTING EVENT WITH THE SPLIT AND NEW CLOSED LOW MOVING IN LATER IN THE WEEK. WITH SUCH A BLOCKY PATTERN DEVELOPING ACROSS CONUS DURING THE UPCOMING HOLIDAY WEEK...BELIEVE FEATURES WILL BE BOTH SLOWER TO EVOLVE AND BREAK DOWN. EVEN THOUGH THE OPERATIONAL MODELS FAVOR A SPLIT FLOW IN THE WEST...THERE ARE CONSIDERABLE DIFFERENCES IN THE PLACEMENT OF THE PARENT CLOSED LOW. GFS TAKES THIS SYSTEM MUCH FARTHER SOUTH ACROSS SOUTHERN CALIFORNIA WHILE THE NAM SOLUTION HAS THE LOW FARTHER NORTH IN THE CENTRAL GREAT BASIN. IMPLICATIONS ARE SIGNIFICANT IN THAT NAM SOLUTION WOULD BRING WET WEATHER AND TRAVEL IMPLICATIONS INTO OUR AREA FOR THE HOLIDAY...WHILE THE GFS WOULD KEEP DRY WEATHER IN THE REGION. A QUICK LOOK AT THE NEW ECMWF WOULD ALSO FAVOR A MORE SOUTHERN TRACK LIKE THE GFS. HAVE KEPT CLIMO POPS GOING IN THIS TIME FRAME DUE TO THE UNCERTAINTY IN THIS IMPORTANT LONG RANGE TRAVEL PERIOD. && .AVIATION...POST FRONTAL MOISTURE AND LIGHT WEST WINDS HAVE PRODUCED UPSLOPE FOGGY AND LOW CLOUD CONDITIONS OVER MUCH OF THE AREA OVERNIGHT. LIFR CONDITIONS EXPECTED IN SOUTHWEST IDAHO AFFECTING KBOI...KEUL AND KONO TERMINALS...WHILE A MORE LOW STRATUS DECK UNDER 1000 FEET AFFECTS THE HIGHER TERRAIN AROUND KJER AND KTWF. MOUNTAIN LOCATIONS ALSO EXPECTED TO SEE IFR CONDITIONS IN FOG AND LOW CLOUDS BUT MAINLY CENTERED AROUND THE USUAL EARLY MORNING TIMES. STRONG SURFACE HIGH DRIFTING SOUTHEAST TOWARD EASTERN IDAHO SUNDAY AFTERNOON WILL BRING INCREASING EASTERLY WINDS INTO SOUTHERN IDAHO AND IMPROVE MOST AREAS INTO MVFR CONDITIONS OR BETTER. LIGHT TO MODERATE WEST WINDS ALOFT. && .BOI WATCHES/WARNINGS/ADVISORIES... ID...DENSE FOG ADVISORY UNTIL 11 AM MST THIS MORNING FOR IDZ016. DENSE FOG ADVISORY UNTIL 11 AM MST THIS MORNING FOR IDZ012- IDZ014. OR...NONE. && $$ WEATHER.GOV/BOISE SHORT TERM...JDS LONG TERM....GS AVIATION.....GS id AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LINCOLN IL 1149 AM CST SUN NOV 23 2008 .DISCUSSION... ISSUED 1040 AM CST SUN NOV 23 2008 FORECAST LOOKS PRETTY NICE TODAY WITH AMPLE SUNSHINE AND MILDER HIGHS IN THE UPPER 40S TO NEAR 50 DEGREES AND SOUTH WINDS 10 TO 15 MPH. ONLY MINOR TWEAKS TO THE HOURLY GRIDS WITH MORE SUNSHINE THROUGH EARLY AFTERNOON AND SLIGHTLY COOLER HIGHS. 16Z/10 AM SURFACE MAP SHOWS LARGE 1034 MB HIGH PRESSURE ACROSS THE MID AND SE ATLANTIC STATES. 1002 MB LOW PRESSURE OVER NORTHERN MANITOBA HAD A COLD FRONT EXTENDING SOUTHWARD ALONG THE MN/DAKOTAS BORDER TO WEAK 1015 MB LOW PRESSURE OVER CENTRAL NEBRASKA AND COLD FRONT THEN EXTENDS INTO NW KS. LARGE HIGH PRESSURE PROVIDING NEARLY SUNNY SKIES OVER CENTRAL/SE IL THIS MORNING WITH JUST SOME THIN CIRRUS CLOUDS BRUSHING AREAS MAINLY FROM I-74 NORTH. AFTER ANOTHER CHILLY EARLY MORNING WITH LOWS FROM 15 TO 25F TEMPS AT 10 AM REBOUNDED INTO THE MID TO UPPER 30S. LOW DEWPOINTS IN THE LOW TO MID 20S WITH SOUTH WINDS 7 TO 14 MPH. NEARLY ZONAL UPPER LEVEL FLOW ACROSS THE CENTRAL AND EASTERN U.S. STRONG UPPER LEVEL LOWS WERE ALONG THE NORTHERN MANITOBA/SASKETCHEWAN PROVINCE LINE AND NEAR FAR NE QUEBEC WHILE UPPER LEVEL RIDGE OVER THE PACIFIC STATES. 12Z RUC13...NAM12 AND SREF MODELS SHOW HIGH PRESSURE STANING NEAR THE MID ALANTIC COAST THROUGH THIS EVENING WHILE THE COLD FRONT MOVES EAST INTO CENTRAL WI/EASTERN IA AND CENTRAL MO BY 06Z/MIDNIGHT. MODELS KEEP CENTRAL/SE IL DRY THROUGH AT LEAST 03Z/9 PM THIS EVENING WITH JUST A SLIGHT CHANCE OF LIGHT RAIN SHOWERS LATE THIS EVENING. BRUNT OF SHOWERS WILL DEVELOP AFTER MIDNIGHT TONIGHT AS COLD FRONT AND SHORT WAVE TROF APPROACHES CENTRAL IL FROM THE WEST BY DAWN MONDAY. AMPLE SUNSHINE CONTINUES THIS AFTERNOON WITH JUST SOME INCREASING THIN CIRRUS CLOUDS. THICKER AND LOWER CLOUDS WILL INCREASE FROM THE WEST FROM MID EVENING INTO EARLY OVERNIGHT. 850 MB TEMPS AROUND -2C EARLY THIS MORNING ELEVATE TO BETWEEN 2 AND 4C BY SUNSET. THIS SUPPORTS HIGHS CLOSE TO NORMAL IN THE UPPER 40S TO NEAR 50F WTIH MILDEST READINGS SW OF LINCOLN. EXPECT SOUTH WINDS OF 10 TO 15 MPH. HUETTL && .AVIATION... ISSUED 1145 AM CST SUN NOV 23 2008 VFR CONDITIONS SHOULD CONTINUE ACROSS THE CENTRAL IL TERMINALS THROUGH MIDNIGHT (06Z). THEN MVFR VISIBILITIES AND IFR TO MVFR CEILINGS WILL DEVELOP FROM WEST TO EAST WITH RAIN SHOWERS LIKELY DEVELOPING AHEAD OF AN APPROACHING COLD FRONT. LARGE 1034 MB HIGH PRESSURE OVER VA...THE CAROLINAS AND GA WILL DRIFT SLOWLY OFF THE MID ATLANTIC COAST THROUGH MON. MEANWHILE A COLD FRONT OVER FAR WESTERN MN INTO SE NEBRASKA AND NW KS MOVES EAST ACROSS CENTRAL IL FROM 10Z TO 14Z. THEN A STRONG UPPER LEVEL TROF DIGS INTO THE MS VALLEY BY 18Z/MON. THIS TO KEEP MVFR BROKEN TO OVERCAST CLOUDS OVER CENTRAL IL BEHIND THE COLD FRONT MON MORNING ALONG WITH PATCHY DRIZZLE. FLURRIES COULD BE POSSIBLE FROM PIA AND BMI NORTH MONDAY. SOUTH WINDS 10 TO 15 KTS WITH GUSTS NEAR 20 KTS THIS AFTERNOON ARE NEAR 10 KTS TONIGHT. WINDS TURN WNW BEHIND A COLD FRONT LATE TONIGHT AND EARLY MONDAY MORNING AND INCREASE TO 10 TO 15 KTS WITH GUSTS AROUND 20KTS AFTER 15Z/MON. HUETTL && .PREV DISCUSSION... ISSUED 150 AM CST SUN NOV 23 2008 LATEST SURFACE ANALYSIS HAD A LARGE AREA OF HIGH PRESSURE... CENTERED EAST OF THE APPALACHIAN MOUNTAINS...EXERTING ITS INFLUENCE OVER MUCH OF THE EASTERN UNITED STATES. MEANWHILE...LOW PRESSURE AND AN ASSOCIATED FRONTAL SYSTEM WAS BEGINNING TO COME TOGETHER OVER THE HIGH PLAINS. A BROAD AREA OF SOUTHERLY FLOW WAS EVIDENT BETWEEN THESE TWO PRESSURE AREAS. ALOFT...A VIGOROUS SHORT WAVE WAS PULLING AWAY FROM THE FORECAST AREA OVER THE OHIO VALLEY... WITH SHORT WAVE RIDGING BUILDING ACROSS THE MIDWEST IN ITS WAKE. NOT TOO MANY FORECAST CONCERNS THE NEXT SEVERAL DAYS AS LOCAL WEATHER PATTERN WILL GENERALLY BE QUIET BUT COOL. HOWEVER...THE COMPLEX APPROACHING HIGH PLAINS FRONTAL SYSTEM...AND THE DRIVING UPPER WAVES...HAVE THE POTENTIAL TO BRING PRECIPITATION TO THE REGION LATER TONIGHT INTO MONDAY. 00Z MODELS IN REASONABLE AGREEMENT THE NEXT FEW DAYS WITH RESPECT TO FEATURES EXPECTED TO IMPACT FORECAST AREA. DESPITE THE GENERAL AGREEMENT IN THE OVERALL PATTERN...THERE IS SPREAD EVIDENT IN THE GUIDANCE TEMPERATURES. FOR THE MOST PART...HAVE FOLLOWED A BLEND OF MODEL SOLUTIONS. SHORT TERM...TODAY THROUGH TUESDAY...STRENGTHENING SOUTHERLY FLOW IS EXPECTED ACROSS THE REGION TODAY INTO TONIGHT WITH THE APPROACH THE PLAINS FRONTAL SYSTEM...AS WELL AS THE PASSAGE OF SHORT WAVE RIDGE ALOFT. AS THESE UPSTREAM FEATURES MOVE CLOSER BY LATER TONIGHT...A QUICK SHOT OF RELATIVELY STRONG WAA/ISENTROPIC LIFT WILL LIKELY PRODUCE SOME LIGHT RAINS. HOWEVER...MODEL SOUNDINGS SUGGEST MOISTURE DEPTH WILL BE LACKING...MAINLY BELOW 800 MB...SO EXPECT PRECIPITATION TOTALS TO BE MINIMAL. COLD FRONT AND DRIVING UPPER WAVE WILL CROSS THE REGION EARLY MONDAY...QUICKLY BRINGING THE MEASURABLE PRECIPITATION THREAT TO AN END. SOUNDING PROFILES DRY OUT QUICKLY BEHIND THE FRONT...SO DO NOT REALLY EXPECT ANY POST FRONTAL PRECIPITATION MONDAY. HOWEVER... IF ANY DOES OCCUR...IT SHOULD FALL AS FLURRIES. ANOTHER UPPER WAVE...AND REINFORCING SHOT OF COLD AIR...WILL CROSS THE REGION LATE MONDAY NIGHT/EARLY TUESDAY. NOT MUCH MOISTURE IS EXPECTED WITH THIS IMPULSE...BUT WOULD NOT BE SURPRISED TO SEE A FEW FLURRIES AS THE ASSOCIATED THERMAL TROF SWINGS THROUGH. LONG TERM...TUESDAY NIGHT THROUGH SATURDAY...QUIET/COOL CONDITIONS APPEAR LIKELY THROUGH THE PERIOD...THOUGH MODEL/ENSEMBLE SPREAD SUGGESTS THIS IS FAR FROM A FORGONE CONCLUSION. SOME DEGREE OF TROFFING IS EXPECTED TO REMAIN ACROSS EASTERN CANADA/NORTHEAST UNITED STATES...WITH THE PERSISTENT NORTHWEST FLOW ALOFT HELPING TO PROVIDE CHILLY AIR. A SOUTHERN STREAM WAVE...ARRIVING ANYWHERE FROM THURSDAY INTO SATURDAY...MAY PHASE WITH THE EASTERN TROF OR LIFT ACROSS REGION IF TROFFING ENDS UP LIKE ONE OF THE WEAKER MODEL SOLUTIONS. THE LACK OF CONFIDENCE IN THE ULTIMATE TIMING/TRACK OF THE SOUTHERN STREAM WAVE PRECLUDES A MENTION OF PRECIPITATION IN THE FORECAST AT THIS TIME. BAK && .ILX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ il AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LINCOLN IL 1134 AM CST SAT NOV 22 2008 .DISCUSSION... ISSUED 1040 AM CST SAT NOV 22 2008 FORECAST IS PRETTY MUCH ON TRACK TODAY AND MADE SOME MINOR ADJUSTMENTS TO INCREASE CLOUDS AND WINDS A BIT TODAY. MOSTLY CLOUDY TO OVERCAST SKIES WITH A CHANCE OF FLURRIES AND SPRINKLES THIS AFTERNOON. HIGHS IN THE UPPER 30S TO AROUND 40 DEGREES WITH SOUTH WINDS 8 TO 15 MPH. 16Z/10 AM SURFACE MAP HAS STRONG 1040 MB CANADIAN HIGH PRESSURE OVER EASTER KY/TN. WEAK 1020 MB LOW PRESSURE WAS OVER FAR SW MN. UPPER LEVEL SHORT WAVE TROF WAS OVER WI/IA AND SOUTHERN MN. BROKEN TO OVERCAST MID LEVEL CLOUDS AROUND 10K FT COVERED IL AHEAD OF THIS SHORT WAVE WHILE SCATTERED LIGHT SNOW SHOWERS WERE OVER THE WESTERN HALF OF IA FROM I-35 WEST. TEMPERATURES OVER CENTRAL IL WERE IN THE UPPER 20S AND LOWER 30S...WITH PONTIAC UP TO 36F. LOW DEWPOINTS IN THE MID TO UPPER TEENS. SSE WINDS 8 TO 15 MPH WITH FEW GUSTS AROUND 20 MPH NORTH OF I-70. 12Z RUC...NAM AND SREF MODELS WEAKEN CANADIAN HIGH PRESSURE TO 1035 MB AS IT MOVES EAST INTO THE MID ATLANTIC STATES BY SUNSET. DECENT UPPER LEVEL TROF/SHORT WAVE WEAKENS TO AS IT MOVES SE INTO WESTCENTRAL AND SW IL BY 00Z/6 PM...THEN OVER KY AND NE TN BY 06Z/MIDNIGHT. 12Z KILX/KDVN SOUNDINGS SHOW VERY DRY LOW LEVELS BELOW 600 TO 650 MB. MODELS THAT HAVE SOME LIGHT QPF OVER IA DISSIPATE IT BY THE TIME THE SHORT WAVE MOVES INTO IL DURING THIS AFTERNOON AND EARLY EVENING DUE TO VERY DRY LOW LEVELS. BUT CENTRAL IL IN FAVORABLE POSITION OF SHORT WAVE (LEFT OF TRACK) AND MAY STILL SEE SOME FLURRIES/SPRINKLES OVER CENTRAL IL DURING MID AND LATE AFTERNOON. NOT MUCH SUN TODAY BUT MILDER 850 MB TEMPS AROUND MINUS 4C TODAY ALONG WITH SOUTH WINDS SUPPORTS CURRENT HIGHS IN THE UPPER 30S TO AROUND 40F. STILL NEARLY 10 DEGREES BELOW NORMAL. HUETTL && .AVIATION... ISSUED 1135 AM CST SAT NOV 22 2008 VFR CONDITIONS SHOULD CONTINUE ACROSS THE CENTRAL IL TERMINALS THROUGH SUNDAY. A SHORT WAVE TROF OVER CENTRAL PARTS OF WI/IA WILL WEAKEN AS IT SWINGS SE ACROSS CENTRAL IL DURING THIS AFTERNOON AND EARLY EVENING. THIS FEATURE WILL BRING BROKEN TO OVERCAST CLOUDS INTIALLY FROM 8 TO 10K FT AND LOWER TO 5 TO 7K FT LATER THIS AFTERNOON AND EVENING. COULD BE SOME FLURRIES OR SPRINKLES WEST OF I-57/CMI FROM MID AFTERNOON INTO EARLY EVENING BUT STILL VFR VSBYS AND CEILINGS. SHORT WAVE EXITS INTO SOUTHERN IL...SW KY AND NORTHERN TN BY 06Z/MIDNIGHT AND CLOUDS WILL SCATTERED OUT AFTER ITS PASSAGE...AT PIA AROUND 03Z AND CMI BY 07Z. WEAK UPPER LEVEL RIDGE BUILDS INTO IL SUNDAY PROVIDING MOSTLY CLEAR SKIES. WINDS WILL STAY OUT OF THE SOUTH THROUGH SUNDAY. LARGE HIGH PRESSURE WILL STAY NEAR THE MID ATLANTIC STATES THROUGH SUNDAY...KEEPING SOUTH WINDS OVER IL. EXPECT WIND SPEEDS OF 10 TO 15 KTS WITH GUSTS NEAR 20 KTS THIS AFTERNOON...DIMINISHING TO 5 TO 10 KTS THIS EVENING AND 10 TO 15 KTS AFTER 14Z/SUN. HUETTL && .PREV DISCUSSION... ISSUED 257 AM CST SAT NOV 22 2008 MAIN CONCERNS THIS PACKAGE WILL BE CHANCE AND TYPE OF PCPN TODAY AND THEN AGAIN SUNDAY NIGHT INTO MONDAY. CURRENTLY MODELS IN FAIRLY GOOD AGREEMENT WITH CURRENT SITUATION AND ARE CONSISTENT AT LEAST IN THE SHORT TERM. NO REAL LONG TERM CONCERNS EXCEPT FOR TEMP FORECAST. LONG TERM MODELS SEEM OK THROUGH WED NIGHT BUT THEN DIFFER TOWARD THE END OF THE WEEK. WILL LIKELY FOLLOW CURRENT LONG TERM FORECAST AND LET NEXT SHIFT TAKE A LOOK AT LATER PERIODS. SHORT TERM...TODAY THROUGH MONDAY NIGHT CURRENT CLIPPER SYSTEM...LOCATED IN S.D. IS PRODUCING WAA CLOUD COVER AHEAD OF IT AND ADDITIONAL CLOUD COVER TO ITS SOUTH. RETURNS SHOWING UP ON RADAR LOOPS...BUT THIS LIKELY JUST MID CLOUDS AND NOT PCPN...THOUGH CAN`T RULE OUT FLURRIES. OTHER PCPN IS OCCURRING NEAR THE SFC LOW IN S.D. AND AHEAD OF IT IN MN AND NRN IOWA. BOTH GFS AND NAM-WRF MODELS FORECAST THIS SYSTEM TO DROP SOUTHEAST TOWARD THE AREA AND WEAKEN...BUT BOTH STILL BRING A 500MB TROUGH THROUGH THE AREA THIS EVENING. MODELS ALSO INDICATE GOOD ISENTROPIC LIFT AHEAD OF THIS SYSTEM WITH CONDENSATION PRESSURE DEFICITS OF LESS THAN 10. SO SHOULD BE PLENTY OF LIFT TO PRODUCE CLOUDS AND POSSIBLY PCPN. ONLY NEGATIVE IS MODEL SOUNDINGS LACK THE LOW LEVEL MOISTURE NEEDED. HOWEVER...BELIEVE THIS TIME OF YEAR WITH TEMPS COLD...STRONG DYNAMIC SYSTEMS CAN STILL SQUEEZE OUT PCPN DESPITE LACK OF MOISTURE. SO ACCOUNT OF THIS AND THE LACK OF LOW LEVEL MOISTURE...WILL INCLUDE FLURRIES IN FORECAST FOR THIS MORNING AND THEN CHANGE TO SPRINKLES AS TEMP WARM UP BY THIS AFTERNOON. WEAKENED SYSTEM...CLOUD COVER AND ANY PCPN WILL BE EAST OF THE AREA TONIGHT AND AREA WILL REMAIN DRY THROUGH SUNDAY. A STRONGER SFC SYSTEM WILL DEVELOP IN THE PLAINS SUNDAY AND MOVE INTO THE AREA SUNDAY NIGHT. WITH HIGH PRSS TO THE SOUTHEAST THROUGH TOMORROW...SOUTHWESTERLY FLOW SHOULD ADVECT PLENTY OF LOW LEVEL MOISTURE INTO THE AREA. THIS SYSTEM WILL BE DEEPENING AS IT MOVES INTO THE AREA AND DYNAMICS WILL BE INCREASING. TEMPS WILL ALSO BE WARMING IN THE UPPER LEVELS SO MOST PCPN SUNDAY NIGHT SHOULD START AS RAIN. HOWEVER...MODEL SOUNDING INDICATE THE POSSIBILITY OF A MIXTURE OF RAIN AND SNOW AFTER MIDNIGHT SUNDAY NIGHT IN THE NORTH. THE ASSOCIATED COLD FRONT AND 500MB TROUGH WILL QUICKLY MOVE THROUGH THE AREA BY MONDAY AFTERNOON. HOWEVER...WITH THIS SYSTEM DEEPENING AS IT MOVES EAST...WRAP AROUND CLOUDS WILL BE LIKELY AND WITH AREA BEING IN CYCLONIC FLOW WILL HAVE TO KEEP MENTION OF SLIGHT CHC OF RAIN/SNOW IN THE GRIDS. THIS WILL NOT APPEAR IN WORDING AT THIS TIME...BUT MAY GET INCLUDED IN LATER FORECAST. REMAINDER OF SHORT TERM WILL BE DRY AS COLD HIGH PRSS BUILDS INTO THE PLAINS. WITH THIS SYSTEM DEEPENING ON MONDAY WILL HAVE TO INCREASE WIND GUSTS DURING THE DAY. BUFKIT MOMENTUM TRANSFER INDICATES POTENTIAL FOR GUSTS TO BETWEEN 25 AND 30 MPH...SO WILL BE ADJUSTING WIND GUSTS GRIDS TO REFLECT THIS. TEMPS WILL BEGIN TO WARM UP SOME TODAY BUT STILL REMAINING BELOW NORMAL. NORMAL TO SLIGHTLY ABOVE NORMAL TEMPS CAN BE EXPECTED SUNDAY WITH STRONG SOUTHWESTERLY FLOW FORECAST. BELOW NORMAL TEMPS WILL BE SEE AGAIN ON MONDAY AFTER THE FRONT MOVES THROUGH. LONG TERM...TUESDAY THROUGH FRIDAY COLD HIGH PRSS WILL BE BUILDING INTO THE PLAINS AT THE BEGINNING OF THE PERIOD AND WILL REMAIN OVER THE AREA THROUGH MOST OF THE WEEK. THE SFC RIDGE WILL BE JUST TO THE EAST OF ILLINOIS THROUGH THURSDAY. SO TEMPS SHOULD REMAIN BELOW NORMAL AS THE FLOW REMAINS OUT OF THE NORTH. LATE IN THE PERIOD A SYSTEM DEVELOPS IN THE SOUTH THAT MOVES TOWARD THE LOWER MISS VALLEY. GFS AND ECMWF SHOW SOME DIFFERENCES WITH THIS...BUT WILL LET NEXT FORECAST SHIFT TAKE A LOOK AND WILL NOT MAKE ANY CHANGES AT THIS TIME. THEREFORE...DRY WEATHER EXPECTED THROUGH THE PERIOD FOR NOW. MEX GUIDANCE NUMBERS LOOK OK FOR TUE BUT THEN TOO LOW FOR REMAINDER OF THE PERIOD. AUTEN && .ILX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ il AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DES MOINES IA 1215 PM CST SAT NOV 22 2008 .SHORT TERM /TODAY/... THE MAIN FORECAST ISSUE TODAY WILL BE PRECIP TRENDS AND SNOW AMOUNTS AS AN UPPER LOW TRAVERSES IOWA. A NARROW BAND OF SNOW MOVED ACROSS PARTS OF NORTHERN IOWA OVERNIGHT AND CURRENTLY EXTENDS FROM CHARLES CITY TO MARSHALLTOWN. SNOWFALL AMOUNTS REPORTED HAVE BEEN LIMITED TO A FEW TENTHS OF AN INCH. SNOW IS QUICKLY ENDING BEHIND THE BAND TO THE WEST IN A NARROW SUBSIDENCE AXIS...BUT FORCING WILL RETURN AFTER 12Z IN THE FAR NORTHWEST COUNTIES THEN SPREAD SOUTHEAST THROUGH THE MORNING. THE NAM/RUC HAVE A GOOD HANDLE ON THE CURRENT WEATHER AND WILL BE FOLLOWED CLOSELY FOR PRECIP TIMING AND COVERAGE. THE HEAVIER SNOWS...AROUND A COUPLE INCHES...ARE EXPECTED IN THE POCAHONTAS-FORT DODGE-SAC CITY AREAS...WITH LESSOR AMOUNTS GENERALLY AN INCH OR LESS ELSEWHERE. CROSS SECTIONS INDICATE A 1-3 HOUR PERIOD OF DECENT LIFT IN THE DENDRITIC LAYER ACROSS THE NORTHWEST PORTION OF THE CWA AND SOME WEAK INSTABILITY ALOFT. THIS AREA IS ALSO HIGHLIGHTED BY A POSITIVE PV PRESSURE ADVECTION MAX THROUGH THE MORNING INTO EARLY AFTERNOON. FORCING WILL QUICKLY EXIT THE CWA TO THE EAST BY LATE AFTERNOON. .LONG TERM /TONIGHT-FRIDAY/... THE AREA OF LOW PRESSURE WILL LOOSE ITS IDENTITY BY THIS EVENING WITH THE STATE REMAINING UNDER SOUTHERLY FLOW ALONG WITH VERY DRY MID LEVELS IN PLACE. SOME STRATUS MAY PERSIST ESPECIALLY THIS EVENING THOUGH IT SHOULD SCATTER BY MIDNIGHT. SUNDAY WILL WARMER WITH ABOVE SEASONAL TEMPERATURES EXPECTED. A COUPLE OF SYSTEMS WILL BE CONVERGING ON CENTRAL IOWA BY LATE SUNDAY. A COLD FRONT WILL ENTER NORTHWEST IOWA WITH AND WILL BE MOISTURE STARVED. AT THE SAME TIME...A SURGE OF GULF MOISTURE WILL BE LIFTING NORTHWARD AND WILL REACH THE FAR SOUTHEAST SUNDAY EVENING. A STRATUS SHIELD WILL LIKELY BE LIFTING NORTH ALONG WITH THE MOISTURE WITH A MOISTURE DEPTH OF AROUND 5 KFT. DECENT LIFT IN THE MOIST LAYER WOULD SUGGEST SOME DRIZZLE OR LIGHT RAIN IS POSSIBLE SUNDAY EVENING FOR A BRIEF PERIOD OVER THE SOUTHEAST. THE BOUNDARY FROM THE NORTHWEST WILL PUSH THE MOISTURE QUICKLY TO THE EAST ENDING PRECIPITATION CHANCES. HAVE MAINTAINED SLIGHT CHANCES ALONG THE BOUNDARY TO THE NORTH WITH RAIN OR SNOW. LOW LEVELS REMAIN RELATIVELY WARM AND WET BULBS ABOVE 0 C THROUGH THE PERIOD OF PRECIPITATION CHANCES THEREFORE SNOW CHANCES WILL BE LIMITED. NUMEROUS STRONG SYSTEMS PASSING SLOWING THROUGH THE FLOW NEXT WEEK. A STRONG CLOSED LOW WILL DROP SOUTH OUT OF MANITOBA AND THROUGH THE WESTERN GREAT LAKES ON MONDAY. THIS WILL RESULT IN WINDY CONDITIONS MONDAY AND MONDAY NIGHT AND COLDER AIR SPILLING SOUTH. COULD APPROACH WIND ADVISORY CONDITIONS OVER THE NORTHEAST MONDAY AFTERNOON. FALLING TEMPERATURES ARE ALSO POSSIBLE BY MONDAY AFTERNOON. THIS SYSTEM WILL THEN LINGER OVER THE NORTHEASTERN CONUS THROUGH MID WEEK. AS THIS OCCURS...ANOTHER STRONG SYSTEM WILL MOVE INTO THE INTERMOUNTAIN WEST AND MOVE SLOWLY EAST. CURRENT FORECAST FOR MOSTLY DRY CONDITIONS THROUGH THANKSGIVING STILL ON TRACK THOUGH THERE IS THE POTENTIAL THE WESTERN SYSTEM WILL BRING PRECIPITATION TO PORTIONS OF THE FORECAST AREA BY FRIDAY. NO CHANGE TO THE FORECAST DURING THIS PERIOD YET AND EXPECT MODEL SOLUTIONS TO BECOME MODIFIED OVER NEXT SEVERAL DAYS AS THEY TRY TO RESOLVE THIS HIGHLY ACTIVE PATTERN. && .AVIATION...22/18Z CLOSED UPR LOW MOVG THRU IA ATTM AND WILL BRING A BAND OF -SN/SN ACRS THE CNTRL INTO THE SERN COUNTIES...ALONG WITH SOME IFR/MVFR CIGS IN ITS WAKE. WRMFNT LFGT NWD ACRS IA WILL REACH NRN TAF SITES BY LATE THIS EVE. CONDS WILL BCM BFR FM SW-NE OVR NGT AS THE FRONT LFTS NWD. && .DMX WATCHES/WARNINGS/ADVISORIES...NONE. && $$ SHORT TERM/AVIATION...MS NOV 08 LONG TERM...DONAVON ia AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE QUAD CITIES IA IL 1109 AM CST SAT NOV 22 2008 .UPDATE... SENT ZFP/GRID UPDATE TO RAISE POPS FOR SNOW THIS AFTN OVER THE SOUTHWEST SECTIONS. VIGOROUS MID LEVEL SHORTWAVE OVER NORTHWEST IA DIVING E/SE. KDMX RADAR SHOWS DECENT AREA OF MOD/HVY SNOW MOVING INTO CENTRAL IA LATE THIS MORNING. BAND APPEARS TO LINE UP WELL WITH RUC H7-H5 PVU WHICH IT WEAKENS BUT BRINGS ACROSS SOUTHWEST SECTIONS OF CWA THIS AFTN EXITING BY EARLY EVE. MODELS TYPICALLY TRY AND WEAKEN SYSTEMS TOO QUICKLY AND THIS LOOKS TO BE THE CASE YET AGAIN... WITH 15Z RUC NOW MAINTAINING AROUND 40 UNIT VORT THROUGH 00Z AS IT DIVES E/SE INTO NORTHEAST MO. 12Z MOS GUIDANCE NOT HANDLING SITUATION WELL WITH POPS IN GENERAL RANGE OF 5-20% AT SITES WHERE IT IS PRESENTLY SNOWING... AN INDICATION WEAKENING TOO QUICKLY. THEREFORE... HAVE BUMPED UP POPS TO MOD/HIGH CHC SOUTHWEST THIS AFTN AND WILL CONTINUE TO MONITOR AS FURTHER UPDATES TO INCREASE POPS WOULD BE REQUIRED IF SYSTEM MAINTAINS CURRENT STRENGTH. AIR TEMPS LOOK TO BE ABOVE FREEZING AND LATEST PAVEMENT TEMPS SHOW RANGE OF 35-43 DEGS IN THE SOUTH... THUS A LOT OF MELTING EXPECTED... WITH ANY ACCUMS DUE SOLELY TO RATE AND MAINLY ON GRASSY/ELEVATED SFCS. .DVN WATCHES/WARNINGS/ADVISORIES... IA...NONE. IL...NONE. MO...NONE. && $$ ia AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TOPEKA KS 516 PM CST SUN NOV 23 2008 .UPDATE... UPDATED THE AVIATION DISCUSSION FOR THE 00Z TAFS. && .DISCUSSION... SEE PREV DISCUSSION. && .AVIATION... SATELLITE SHOWS STCU DECK ADVECTION NORTHEAST ALONG THE PRE FRONTAL TROUGH WITH EMP AND UKL SHOWING CIGS BETWEEN 3 AND 4 KFT. FORECAST SOUNDINGS FROM THE NAM AND RUC HAVE THESE CIGS BRIEFLY IN AT TOP AND FOE. BY 04Z THE FRONT SHOULD PUSH SOUTHEAST WITH DRY AIR ADVECTING IN FROM THE NORTHWEST LEAVING VFR CONDITIONS AND SOME HIGH CIRRUS. THESE CONDITIONS WILL PREVAIL THROUGH 06Z TUE WITH SFC HIGH PRESSURE MAINTAINING A DRY AIRMASS AND UPPER LEVEL SUBSIDENCE OCCURRING ON THE BACK SIDE OF THE UPPER LEVEL TROUGH. WOLTERS && .PREV DISCUSSION.../253 PM CST SUN NOV 23 2008/ TONIGHT AND MONDAY...AT 20Z LEADING EDGE OF A COLD FRONT WAS PUSHING INTO THE NORTHWESTERN CORNER OF THE CWA. THIS FRONT WILL CONTINUE TO PUSH SOUTHEAST THROUGH THE FORECAST AREA THIS EVENING AND OVERNIGHT IN RESPONSE TO A SHORTWAVE TROUGH MOVING INTO THE CENTRAL PLAINS THIS AFTERNOON. DO NOT EXPECT ANY PRECIPITATION TO DEVELOP ALONG THE COLD FRONT AS IT MOVES THROUGH OVERNIGHT AS DEEPER LOW LEVEL MOISTURE WAS LOCATED SOUTHEAST OF THE CWA. SHALLOW MOISTURE HAS ADVECTED INTO NORTHEASTERN KS...BUT DEEPER MOISTURE LOOKS FAIRLY WELL DEFINED BY STRATUS DECK EXTENDING FROM EASTERN OK THROUGH SOUTHEASTERN KS AND INTO CENTRAL MO. H850 PROFILER WINDS REMAIN VEERED AROUND TO THE SOUTHWEST AHEAD OF THE APPROACHING COLD FRONT...SO BELIEVE THE DEEPER LOW LEVEL MOISTURE WILL REMAIN SOUTHEAST OF THE CWA. CLOUDS WILL BE ON THE INCREASE AS THE SHORTWAVE TROUGH MOVES OVER THE CWA TONIGHT...BUT SHOULD CLEAR OUT QUICKLY DURING THE MORNING HOURS TOMORROW AS UPPER LEVEL SUBSIDENCE BUILDS OVER THE FORECAST AREA AS THE WAVE EXITS TO THE SOUTHEAST. TEMPERATURES WILL BE A BIT COOLER TOMORROW BEHIND THE COLD FRONT...BUT THE COOLER AIRMASS IS EXPECTED TO BE MODIFIED BY THE SUNNY SKIES...AND TEMPERATURES SHOULD BE ABLE TO CLIMB UP INTO THE LOWER 50S FOR MOST LOCATIONS. CAVANAUGH MONDAY NIGHT THROUGH SUNDAY...AS POTENT UPPR LVL TROF CONTS TO DEEPEN OVR THE GREAT LAKES ON MON NIGHT...A BACKDOOR CDFNT WL SLIP SW FM ERN NEB AND NW MO INTO THE CWA. LITTLE SENSIBLE WX IS EXPECTED WITH THE FNT...BUT THIS SHLD LEAD TO A COOLER NIGHT OVR THE ERN CWA AND TRIMMED TMPS BACK IN THIS AREA CLOSER TO THE COOLER MAV GUIDANCE. COOLING IS SHRT LIVED THOUGH AS UPPR TROF IS QUICK TO SHIFT EWD AS RIDGE BUILDS INTO THE CNTRL PLAINS. THIS WL BRING SWRLY LO LVL FLOW TO THE AREA AND A NICE WARM UP FOR MID WEEK. NAM/EC ARE WARMER THAN THE GFS WITH H85 TMPS...AND GIVEN MOSTLY SUNNY SKIES...GOOD MIXING AND DRY SURFACE CONDITIONS...PREFER TO GO WARMER DURING THIS PERIOD. NEXT SYSTEM TO AFFECT THE CWA WL COME IN THE THUR/FRI TIME FRAME. LARGE SPREAD IN GUIDANCE REMAINS WITH THIS SYSTEM...BUT THERE ARE SOME NOTABLE TRENDS. GFS HAS BEEN TRENDING DRIER FOR OUR CWA DUE TO A STRONGER NRN STREAM INFLUENCE WITH THE UPPR LVL TROF OVR THE HUDSON BAY. THIS IS ALSO SUPPORTED IN THE CANADIAN...GEFS...AND MANY OF THE GFS ENSEMBLES. IN ADDITION...THE 12Z EC IS ALSO STRONGER WITH THIS NRN STRM INFLUENCE AND THUS DRIER. SINCE THE UPSTRM ENERGY MOVG INTO THE WRN US LATE IN THE WEEK IS EXPECTED TO FORCE A RETROGRESSION OF THE UPPR AIR PATTERN...A STRONGER NRN STRM INFLUENCE APPEARS REASONABLE. THUS WL GO MORE WITH THE GFS MODEL DURING THIS TIME PERIOD AND START TO TREND DOWN POPS...ESPECIALLY OVR THE NRN CWA. WL ALSO GO WITH AN ALL RAIN EVENT WITH A LACK OF ANY REAL COLD AIR UNTIL FRI INTO SAT. ONCE SYSTEM MOVES BY...THE WEEKEND FORECAST ALSO HAS A SIGNIFICANT AMOUNT OF UNCERTAINLY. IT APPEARS THE CWA SHLD BE MAINLY DRY THROUGH THE PERIOD...BUT TEMPERATURES ARE THE MAIN QUESTION. GIVEN THE STRONGER INFLUENCE OF THE NRN STRM...WLD PREFER TO TREND DOWN TMPS OVR THE WEEKEND. THUS FORECAST WL REFLECT MEX OR SLIGHTLY BELOW MEX NUMBERS FOR NEXT WEEKEND. BOUSTEAD && .TOP WATCHES/WARNINGS/ADVISORIES...NONE. && $$ ks AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LAKE CHARLES LA 938 PM CST SUN NOV 23 2008 .UPDATE... ONLY UPDATE TO THE GRIDS THIS EVENING IS TO POPS/WX/QPF. RADAR MOSAIC SHOWS A BAND OF SHOWERS OVER THE GULF WATERS SOUTH OF HOUSTON/GALVESTON BAY. THIS ACTIVITY IS LIFTING SLOWLY NE AND BOTH RUC AND NAM APPEAR TO HAVE A HANDLE ON CURRENT TRENDS WITH INCREASING PRECIP OVER OUR SWRN ZONES AND WESTERN COASTAL WATERS OVERNIGHT AS LOW LEVEL FLOW OFF THE SFC BECOMES MORE SWRLY. LOWERED POPS TO 20 PERCENT AREAWIDE FOR THE REMAINDER OF THE EVENING...INCREASING TO 30 PERCENT AFTER MIDNIGHT FOR THE LOWER SE TX ZONES AND COASTAL WATERS MAINLY WEST OF CAMERON. REMAINDER OF FORECAST LOOKS GOOD. UPDATED ZONES HAVE BEEN SENT. 24 && .PREV DISCUSSION... /ISSUED 707 PM CST SUN NOV 23 2008/ AVIATION...MAIN CHALLENGE THIS TAF PACKAGE ISSUANCE IS TIMING OF THE ONSET OF PRECIPITATION. REGIONAL 88DS SHOW MAINLY LIGHT SHOWERS... MUCH OF IT PROBABLY JUST VIRGA ATTM...OVER THE GULF OFF THE MIDDLE TEXAS COAST MOVING NWD. MODEL PROJECTIONS SHOW PRECIP SPREADING OVER THE AREA FROM THE SOUTHWEST AND WEST STARTING TOWARD 12Z... ALTHOUGH LIKE LAST NIGHT THE GFS APPEARS TO BE A LITTLE WETTER AND FASTER THAN THE NAM. THUS HAVE TIMED THE PREVAILING POPS IN THE TAFS WITH THIS IN MIND. BUT UNTIL THEN FOR THE OVERNIGHT JUST STUCK WITH VFR CEILINGS GRADUALLY LOWERING...ALONG WITH SOME LIGHT RESTRICTIONS TO VISIBILITY AS WINDS LOOK SUFFICIENT FOR PREVENTING FOG FORMATION. 25 PREV DISCUSSION... /ISSUED 240 PM CST SUN NOV 23 2008/ DISCUSSION...A RATHER MILD AND PLEASANT AFTERNOON ONGOING ACROSS THE REGION. DESPITE CONSIDERABLE MID LEVEL CLOUDINESS...WARMING SOUTHERLIES HAVE MANAGED TO WARM TEMPS INTO THE UPPER 60S NORTH...LOW 70S SOUTH. DEWPOINTS GENERALLY RUNNING FROM 15 TO 20 DEGREES ABOVE THAT OF 24 HOURS PRIOR. LOCAL RADAR INDICATING JUST A BIT OF VIRGA OVER CENTRAL LOUISIANA. NEXT FRONTAL PASSAGE CONTINUES ON TRACK FOR MONDAY. LATEST MOS GUIDANCE SHOWING LESS PRE-FRONTAL ACTIVITY DEVELOPING ACROSS THE REGION TONIGHT. HAVE ADJUSTED GRIDS/POPS DOWN ACCORDINGLY. WILL HOWEVER MAINTAIN LIKELY POPS FOR MONDAY WITH GOOD LOW LEVEL CONVERGENCE DEVELOPING ALONG BOUNDARY...WITH DEEP OMEGAS/LIFT ALSO ACCOMPANYING FRONT. SUFFICIENT SPEED OF SYSTEM WILL EFFECTIVELY LIMIT ANY SIGNIFICANT WIDESPREAD RAIN AMOUNTS. HIGH PRESSURE BECOMES REESTABLISHED FOR TUESDAY AND WEDNESDAY. RETURN FLOW SETS UP THURSDAY AHEAD OF NEXT FRONTAL PASSAGE WHICH APPEARS LIKELY PER LONG RANGE MODELS ON FRIDAY. AVIATION...OVERCAST SKIES WILL CONTINUE FOR THE REMAINDER OF THE AFTERNOON INTO THIS EVENING AS SOUTHWEST FLOW AHEAD OF AN ADVANCING SHORT WAVE PULLS EAST PAC MOISTURE OVER THE REGION. ISENTROPIC LIFT IS EXPECTED TO BE WEAK...ALONG WITH SOME RELATIVELY DRY AIR BETWEEN THE SURFACE AND 10K FEET...AND THUS ANY PRECIPITATION WILL BE JUST SOME SPRINKLES OR VIRGA. CEILING HEIGHTS WILL CONTINUE TO BE AT VFR LEVELS. SOUTHERLY WINDS ARE EXPECTED TO INCREASE LATER TONIGHT INTO EARLY MONDAY AS SHORT WAVE CONTINUES TO ADVANCE TOWARD THE AREA. THESE WINDS WILL HELP INCREASE MOISTURE VALUES WITH GUIDANCE TIME HEIGHTS SHOWING OVER 80 PERCENT RH BETWEEN THE SURFACE TO OVER 20K FEET BY 24/12Z. THIS WILL HELP LOWER CEILING HEIGHTS TO BETWEEN 3K-5K FEET WITH A FEW SHOWERS DEVELOPING FROM WEST TO EAST DURING THE OVERNIGHT. WITH BOUNDARY LAYER WINDS EXPECTED BETWEEN 15 AND 20 KNOTS AND SOME LIFT SEEN BY PROGGED PVA IN THE LOW LEVELS...ANY FOG FORMATION WILL BE PATCHY IN NATURE WITH SOME MVFR VISIBILITIES POSSIBLE. SHOWERS ARE EXPECTED TO BE ON THE INCREASE AFTER 24/12Z FROM WEST TO EAST AS STRONGER LIFT FROM AN APPROACHING COLD FRONT TAPS INTO THE ABUNDANT MOISTURE. RUA MARINE...A MODEST SOUTHERLY FLOW WILL CONTINUE TONIGHT AHEAD OF AN ADVANCING COLD FRONT. THE FRONT WITH SHOWERS AND THUNDERSTORMS WILL MOVE ACROSS THE NORTHWEST GULF MONDAY FOLLOWED BY A STRONG OFFSHORE FLOW. && .PRELIMINARY POINT TEMPS/POPS... KLCH 60 73 47 69 44 / 20 70 10 0 0 KBPT 62 74 46 70 44 / 30 70 10 0 10 KAEX 58 69 42 67 40 / 20 70 10 0 10 KLFT 58 71 48 66 43 / 20 70 10 0 0 && .LCH WATCHES/WARNINGS/ADVISORIES... LA...NONE. TX...NONE. GM...NONE. && $$ la AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WAKEFIELD VA 240 PM EST SUN NOV 23 2008 .SYNOPSIS... HIGH PRESSURE WILL REMAIN PARKED OVER THE MID ATLANTIC REGION THIS AFTERNOON AND EVENING...THEN PUSH OFF THE COAST LATER TONIGHT. A COLD FRONT APPROACHES FROM THE WEST MONDAY AFTERNOON...THEN SWEEPS ACROSS THE AREA MONDAY NIGHT INTO EARLY TUESDAY MORNING. A DEEP LOW PRESSURE SYSTEM WILL REMAIN NEARLY STATIONARY OVER NEW ENGLAND TUESDAY THROUGH FRIDAY...AS HIGH PRESSURE RIDGES INTO THE MID ATLANTIC REGION FROM THE WEST. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... FAST-MOVING 100+ KT JET STREAK/RELATIVELY FLAT MID/UPPER LEVEL SHORTWAVE NOW STRETCHING FROM TN VLY OVR THE CAROLINAS AND OFF THE COAST. AS EXPECTED...ONLY MID/UPPER LVL MSTR/CLDS ARE ACCOMPANYING THIS FEATURE AS DEEP WRLY LLVL FLOW AHEAD OF THE TROUGH IS A) INHIBITING ANY GULF MOISTURE INFLUX AND B) CAUSING FURTHER LLVL DRYING E OF THE MNTNS VIA DOWNSLOPE. LOW LEVELS (BLW 700 MB OR 10 KFT) IN FACT ARE SO DRY PER LAPS/RUC SOUNDINGS THAT IT WOULD BE TOUGH TO EVEN GET A FLURRY OUT OF THIS FEATURE. UPDATED FOR CLEAR SKIES THIS MORNING AND IN THE AFTN WITH STRONG DNVA AND DEEP LAYER SUBSIDENCE/DRYING. LLVL THICKNESS SCHEMES SHOW BOOST IN BNDRY LAYER TEMPS TODAY AS 850 MB TEMPS CLIMB TO BTWN -2 TO -4C THIS AFTN FROM S TO N. ADJUSTED HIGHS DOWN A DEGREE OR SO DOWN MID 40S FAR NE PTNS (LWR MD ERN SHORE) TO AROUND 50 SW PTNS (SOUTH HILL-EMPORIA). && .SHORT TERM /6 PM THIS EVENING THROUGH WEDNESDAY/... HIGH MOVES OFF THE COAST LATE THIS EVENING/AFTER MIDNIGHT...HOWEVER RETURN SRLY LLVL FLOW NEVER GETS A CHANCE TO MATERIALIZE AT THE SFC OVERNIGHT AS CLEAR/CALM CONDITIONS EARLY ON THIS EVENING WILL ALLOW FOR SFC LAYER DECOUPLING. SO...WHILE THE TEMPTATION IS THERE TO BOOST TEMPS A LITTLE OVER MOS GUIDANCE TONIGHT...HAVE STUCK WITH A FCST FAIRLY CLOSE TO A MAV/MET MOS BLEND (I.E. 20S INLAND... AROUND 30/LWR 30S ALONG THE SERN VA/NERN NC COAST). CDFNT APPROACHES FROM THE WEST MON AFTERNOON...THEN PUSHES THROUGH THE FCST AREA MON NIGHT...THEN OFF THE COAST EARLY TUE MORNING. THE GFS/NAM/SREF/ECMWF ARE ALL IN VERY GOOD AGREEMENT IN TERMS OF THE TIMING OF THE FRONT...ALONG WITH THE DEEP LAYER DYNAMICAL SUPPORT/MOISTENING AHEAD OF THE FRONT. WHILE NARROW...THE MODEL ISENTROPIC SFC ANALYSES SHOW THE WARM CONVEYOR BELT BECOMING ENHANCED BY THE MOIST LLVL FLOW OUT OF THE GULF OF MEXICO. MEANWHILE...A RELATIVELY QUICK BURST OF LEFT EXIT REGION UPPER DIVERGENCE/DIFFLUENCE...DPVA...AND FRONTOLYTIC QS CONVERGENCE AND WAA DYNAMICS DEVELOPS FROM W TO E ACROSS THE AREA. GIVEN THE MODEL CONSENSUS WITH THESE SIGNALS...FEEL CONFIDENT TO BOOST POPS ABOVE 50% IN ALL AREAS...BEGINNING BY LATE MON AFTN OVER FAR WRN PTNS... DURING THE EVENING HRS IN ALL AREAS...AND THEN E TOWARD THE COAST LATE MON NIGHT AS THE FRONT SWEEPS W TO E. AT LEAST FOR NOW...HAVE CONTINUED TO LEAVE OUT THE MENTION OF TSTMS...AS MODELS AGAIN SHOW MOIST ADIABATIC LAPSE RATES AND THUS LIMITED CAPE POTENTIAL (SFC BASED OR ELEVATED). TEMPS WILL LIKELY REMAIN STEADY OR EVEN RISE A BIT MON NIGHT UNTIL THE COLD FRONT MOVES THROUGH. FRONT QUICKLY PUSHES E ON TUE...AND WILL BE FOLLOWED BY ANOTHER NW FLOW CAA SURGE AND STRENGTHENING QVECTOR DIVERGENCE (SUBSIDENCE) IN LOW-MID LEVELS. OUTSIDE OF SLIM LINGERING RAIN CHANCES EARLY OVER THE LWR ERN SHORE...HAVE GONE WITH A DRY FCST ON TUE THRU WED. && .LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/... HIGH PRESSURE CONTINUES TO BUILD IN FROM THE W/SW WEDNESDAY NIGHT AND THURSDAY AND EXPECT A DRY THANKSGIVING. THE HIGH WILL THEN WEAKEN AND SLIDE OFFSHORE THURSDAY NIGHT INTO FRIDAY AS THE NEXT COLD FRONT APPROACHES THE REGION FROM THE NW. BOTH GFS AND ECMWF DEVELOP AN AREA OF LOW PRES ALONG THE FRONT OVER AL/MS LATE FRIDAY...THEN MOVE IT TO THE NORTHEAST AND OVER OUR AREA ON SATURDAY. WILL CARRY A SLIGHT CHANCE OF RAIN ON FRIDAY NIGHT INCREASING TO A CHANCE ON SATURDAY. THE LOW CONTINUES TO MOVE TO THE NORTHEAST AND OFF THE NEW ENGLAND COAST ON SUNDAY...WITH HIGH PRESSURE AND DRY WEATHER RETURNING TO OUR AREA ON NEXT SUNDAY. HIGH TEMPERATURES WILL REMAIN BELOW NORMAL THROUGH THE EXTENDED PERIOD...NEAR 50 TO MID 50S. LOW TEMPERATURES WILL BE IN THE UPR 20S TO UPR 30S WEDNESDAY NIGHT AND THURSDAY NIGHT...THEN WILL WARM SLIGHTLY AS WINDS BECOME SW AND AS CLOUD COVER INCREASES AND PRECIP ARRIVES...LWR 30S TO LWR 40S FRIDAY NIGHT THEN MID 30S TO MID 40S SATURDAY NIGHT. && .AVIATION /19Z SUNDAY THROUGH FRIDAY/... VFR CONDITIONS PREVAIL FOR THE NEXT 24 HRS/THROUGH 18Z MONDAY...WITH SOME INCREASE IN HIGH CLOUDS OVERNIGHT THROUGH MONDAY MORNING. WINDS REMAIN RATHER LGT...WITH INCREASING SW FLOW BY LATE MONDAY MORNING INTO THE AFTN. THROUGH THE AFTN HRS MONDAY EXPECT TO SEE CIGS GRADUALLY LOWER...BRINGING A GOOD CHC FOR SHRAS AND A LKLY PERIOD OF MVFR CIGS MON EVENING/NIGHT. CONDITIONS RAPIDLY IMPROVE TWDS DAYBREAK TUESDAY AS THE COLD FRNT PUSHES OFFSHORE...WITH BREEZY BUT DRIER WNW FLOW. GNLY VFR CONDITIONS WED/THU. && .MARINE... HIGH PRESSURE WILL REMAIN OVER THE COASTAL WATERS TONIGHT...THEN SLIDE EAST OF THE WATERS BY EARLY MONDAY AS A COLD FRONT APPROACHES FROM THE NW. THE GRADIENT BETWEEN THE HIGH TO THE EAST AND AN AREA OF LOW PRESSURE OVER THE GREAT LAKES WILL TIGHTEN THROUGH THE DAY MONDAY...WITH SOUTHERLY WINDS INCREASING TO SCA CONDITIONS OVER THE CHES BAY AND CURRITUCK SOUND BY MONDAY AFTERNOON...AND WINDS AND SEAS INCREASING/BUILDING TO SCA LEVELS OVER ALL OF THE COASTAL WATERS BY MONDAY EVENING. THE COLD FRONT WILL PUSH OFFSHORE AND EAST OF THE WATERS ON TUESDAY...BUT LOW PRESSURE WILL LINGER OVER THE GREAT LAKES WITH HIGH PRESSURE BUILDING BACK IN FROM THE SW. THUS SCA FLAGS ARE LIKELY TO CONTINUE THROUGH AT LEAST MID WEEK WITH THE PRESSURE GRADIENT REMAINING TIGHT...ALTHOUGH WILL NOT EXTEND HEADLINES BEYOND THE 3RD PERIOD FOR NOW PER LOCAL POLICY. && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...NONE. NC...NONE. VA...NONE. MARINE...SMALL CRAFT ADVISORY FROM 1 PM MONDAY TO 6 AM EST TUESDAY FOR ANZ630>633. SMALL CRAFT ADVISORY FROM 6 PM MONDAY TO 6 AM EST TUESDAY FOR ANZ650-652-654-656-658. && $$ SYNOPSIS...BKH NEAR TERM...BKH/BAJ SHORT TERM...BKH LONG TERM...JRL AVIATION...LKB MARINE...JRL md AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WAKEFIELD VA 1030 AM EST SUN NOV 23 2008 .SYNOPSIS... HIGH PRESSURE WILL REMAIN PARKED OVER THE MID ATLANTIC REGION TODAY... THEN PUSH OFF THE COAST TONIGHT. A COLD FRONT APPROACHES FROM THE WEST MONDAY AFTERNOON...THEN SWEEPS ACROSS THE AREA MONDAY NIGHT INTO EARLY TUESDAY MORNING. A DEEP LOW PRESSURE SYSTEM WILL REMAIN NEARLY STATIONARY OVER NEW ENGLAND TUESDAY THROUGH FRIDAY...AS HIGH PRESSURE RIDGES INTO THE MID ATLANTIC REGION FROM THE WEST. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... FAST-MOVING 100+ KT JET STREAK/RELATIVELY FLAT MID/UPPER LEVEL SHORTWAVE NOW STRETCHING FROM TN VLY OVR THE CAROLINAS AND OFF THE COAST. AS EXPECTED...ONLY MID/UPPER LVL MSTR/CLDS ARE ACCOMPANYING THIS FEATURE AS DEEP WRLY LLVL FLOW AHEAD OF THE TROUGH IS A) INHIBITING ANY GULF MOISTURE INFLUX AND B) CAUSING FURTHER LLVL DRYING E OF THE MNTNS VIA DOWNSLOPE. LOW LEVELS (BLW 700 MB OR 10 KFT) IN FACT ARE SO DRY PER LAPS/RUC SOUNDINGS THAT IT WOULD BE TOUGH TO EVEN GET A FLURRY OUT OF THIS FEATURE. UPDATED FOR CLEAR SKIES THIS MORNING AND IN THE AFTN WITH STRONG DNVA AND DEEP LAYER SUBSIDENCE/DRYING. LLVL THICKNESS SCHEMES SHOW BOOST IN BNDRY LAYER TEMPS TODAY AS 850 MB TEMPS CLIMB TO BTWN -2 TO -4C THIS AFTN FROM S TO N. ADJUSTED HIGHS DOWN A DEGREE OR SO DOWN MID 40S FAR NE PTNS (LWR MD ERN SHORE) TO AROUND 50 SW PTNS (SOUTH HILL-EMPORIA). && .SHORT TERM /6 PM THIS EVENING THROUGH TUESDAY NIGHT/... HIGH MOVES OFF THE COAST LATE THIS EVENING/AFTER MIDNIGHT...HOWEVER RETURN SRLY LLVL FLOW NEVER GETS A CHANCE TO MATERIALIZE AT THE SFC OVERNIGHT AS CLEAR/CALM CONDITIONS EARLY ON THIS EVENING WILL ALLOW FOR SFC LAYER DECOUPLING. SO...WHILE THE TEMPTATION IS THERE TO BOOST TEMPS A LITTLE OVER MOS GUIDANCE TONIGHT...HAVE STUCK WITH A FCST FAIRLY CLOSE TO A MAV/MET MOS BLEND (I.E. 20S INLAND... AROUND 30/LWR 30S ALONG THE SERN VA/NERN NC COAST). CDFNT APPROACHES FROM THE WEST MON AFTERNOON...THEN PUSHES THROUGH THE FCST AREA MON NIGHT...THEN OFF THE COAST EARLY TUE MORNING. THE GFS/NAM/SREF/ECMWF ARE ALL IN VERY GOOD AGREEMENT IN TERMS OF THE TIMING OF THE FRONT...ALONG WITH THE DEEP LAYER DYNAMICAL SUPPORT/MOISTENING AHEAD OF THE FRONT. WHILE NARROW...THE MODEL ISENTROPIC SFC ANALYSES SHOW THE WARM CONVEYOR BELT BECOMING ENHANCED BY THE MOIST LLVL FLOW OUT OF THE GULF OF MEXICO. MEANWHILE...A RELATIVELY QUICK BURST OF LEFT EXIT REGION UPPER DIVERGENCE/DIFFLUENCE...DPVA...AND FRONTOLYTIC QS CONVERGENCE AND WAA DYNAMICS DEVELOPS FROM W TO E ACROSS THE AREA. GIVEN THE MODEL CONSENSUS WITH THESE SIGNALS...FEEL CONFIDENT TO BOOST POPS ABOVE 50% IN ALL AREAS...BEGINNING BY LATE MON AFTN OVER FAR WRN PTNS... DURING THE EVENING HRS IN ALL AREAS...AND THEN E TOWARD THE COAST LATE MON NIGHT AS THE FRONT SWEEPS W TO E. AT LEAST FOR NOW...HAVE CONTINUED TO LEAVE OUT THE MENTION OF TSTMS...AS MODELS AGAIN SHOW MOIST ADIABATIC LAPSE RATES AND THUS LIMITED CAPE POTENTIAL (SFC BASED OR ELEVATED). TEMPS WILL LIKELY REMAIN STEADY OR EVEN RISE A BIT MON NIGHT UNTIL THE COLD FRONT MOVES THROUGH. FRONT QUICKLY PUSHES E ON TUE...AND WILL BE FOLLOWED BY ANOTHER NW FLOW CAA SURGE AND STRENGTHENING QVECTOR DIVERGENCE (SUBSIDENCE) IN LOW-MID LEVELS. OUTSIDE OF SLIM LINGERING RAIN CHANCES EARLY OVER THE LWR ERN SHORE...HAVE GONE WITH A DRY FCST ON TUE. && .LONG TERM /WEDNESDAY THROUGH SATURDAY/... AFTER CD FROPA TUESDAY...DEEP OCCLUDED LOW STALLS OVER PA/NY WED AND THU...DRIFTING N OVR QUEBEC THU NGHT INTO FRI. PRECIP TO REMAIN ALONG APP RIDGES...THO OVER RUNNING CLOUDS SHOULD KEEP SCT/BKN CLDS (ESP NRN ZONES) ON WED. THICKNESSES INCREASE WED THROUGH FRI AS LOW DRIFTS N AND HIGH BUILDS IN FROM THE W (ESP THU INTO FRI MRNG). TEMPS GENERALLY FIVE DEGREES BELOW NORM...MAXES LWR 50S...MINS UPR 20S. NEXT CHC OF PRECIP WITH SFC LOW/FROPA ON SAT. && .AVIATION /15Z SUNDAY THROUGH THURSDAY/... VFR CNDTNS THRU FCST PRD. MID LVL CLD DECK BTWN 9-12K FT OVRSPRDS TAF SITES THRU 12Z AS S/W PASSES OVR RGN. CLDS DECREASE THRU AM HRS AS HIGH PRS BUILDS IN. ONLY SCT SC ARND 5K FT XPCTD THIS AFTRN. WNDS BECOME NW AOB 12 KTS. THE NEXT COLD FRNT APPRCHS FM THE W MONDAY NGT...BRINGING A CHC FOR SHRAS AND A LKLY PERIOD MVFR CIGS...WITH CONDITIONS IMPROVING BY ERY TUESDAY AS THE COLD FRNT PUSHES OFFSHORE. && .MARINE... HIGH PRESSURE AND TRANQUIL BOATING CONDITIONS OVER THE COASTAL WATERS TODAY. HIGH PRESSURE WILL THEN SLIDE OFFSHORE TONIGHT. PRES GRDNT BEGINS TO INCRS AHEAD OF NXT CDFRNT MON AFTRN. LTST DATA SUGGESTS FAIRLY HIGH CONFIDENCE THAT WNDS INCRS TO SCA LVLS ACROSS CHES BAY/CURRITUCK SND DRNG AFTRN HRS...SO HAVE RAISED SCA FLAGS MON AFTRN AND CONT THRU MON NITE. SHUD TAKE A FEW MORE HRS FOR CNDTNS TO REACH SCA ACROSS CSTL WTRS...SO WON`T START SCA`S THERE UNTIL THE 4TH PRD. SCA`S WILL LIKELY BE XTNDD INTO TUE AND TUE NITE AS W WNDS REMAIN GUSTY DUE TO LOW PRS MOVG INTO NRN NEW ENGLAND. && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...NONE. NC...NONE. VA...NONE. MARINE...SMALL CRAFT ADVISORY FROM 1 PM MONDAY TO 6 AM EST TUESDAY FOR ANZ630>633. SMALL CRAFT ADVISORY FROM 6 PM MONDAY TO 6 AM EST TUESDAY FOR ANZ650-652-654-656-658. && $$ SYNOPSIS...BKH NEAR TERM...BKH/BAJ SHORT TERM...BKH LONG TERM...BAJ AVIATION...MPR MARINE...JRL/MPR md AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE MARQUETTE MI 1220 PM EST SUN NOV 23 2008 UPDATED AVIATION DISCUSSION FOR 18Z TAF ISSUANCE .SYNOPSIS... ISSUED AT 408 AM EST 08Z WATER VAPOR LOOP AND RUC 500MB HEIGHT ANALYSIS SHOWED A SOMEWHAT PROGRESSIVE FLOW FROM THE PACIFIC ACROSS THE NORTHERN U.S....WHICH THEN SLOWS DOWN IN SE CANADA AND THE NORTHEAST U.S. WHERE A FAIRLY DEEP TROUGH EXISTS. WITHIN THE PROGRESSIVE FLOW...THERE ARE TWO SHRTWV TROUGHS TO NOTE...ONE OVER IDAHO AND A SECOND MORE WRAPPED UP ONE CROSSING NRN SASKATCHEWAN. A THIRD...BUT MUCH WEAKER SHRTWV IS MAKING ITS WAY SE INTO NRN LAKE SUPERIOR...ON THE EAST SIDE OF AN UPPER RIDGE BEING BUILT UP AHEAD OF THE SRN CANADA SHRTWV TROUGH. THIS WEAK SHRTWV IS NOT HAVING MUCH IMPACT BESIDES A FEW HIGH CLOUDS CROSSING THE EASTERN CWA...DUE TO DRY LOW TO MID-LEVEL AIR SEEN ON THE 00Z SOUNDINGS FROM APX AND GRB. THIS DRY AIR AND SOME CLEAR SKIES...ALONG WITH LIGHT WINDS ASSOCIATED WITH A SURFACE RIDGE... ALLOWED LOCATIONS IN DELTA COUNTY TO DROP TO NEAR ZERO DURING THE EVENING. HOWEVER...THE RIDGE HAS MOVED EAST...ALLOWING RETURN SOUTHERLY FLOW TO BRING READINGS BACK UP. THE SOUTHERLY FLOW IS ALSO BRINGING SOME STRATUS WITH IT...NOW COVERING ALL OF MN INTO WRN WI AND WRN UPPER MI. 00Z INL SOUNDING SHOWS THE STRATUS WITH A SATURATED LAYER BTWN 800-925MB...WHILE THE REST OF THE SOUNDING IS DRY. SOME FREEZING DRIZZLE EVEN OCCURRED AT GFK AT 03Z...BUT NO OTHER FZDZ REPORTS HAVE OCCURRED. OTHERWISE...THE WARM ADVECTION AHEAD OF THE SHRTWV IN CENTRAL CANADA IS NOT PRODUCING MUCH PCPN. 850MB TEMPS ASSOCIATED WITH THE ADVECTION ARE DEFINITELY WARMER THAN THEY HAVE BEEN OVER THE CWA...3C AT BIS AND 1C AT CYQD...COMPARED TO -8C AT CWPL AND -7C AT APX. FARTHER TO THE WEST WITH THE OTHER SHRTWV TROUGH...SOME -SN IS CROSSING ERN MT. && .DISCUSSION... ISSUED AT 408 AM EST TODAY...UPPER TROUGH OVER SASKATCHEWAN IS PROGGED TO DEEPEN AND MOVE INTO MANITOBA BY 00Z MON. AS THE TROUGH MOVES EAST...THE BUILDING RIDGE OVER THE UPPER MISSISSIPPI VALLEY WILL MOVE OVER UPPER MI. SUBSIDENCE UNDER THE UPPER RIDGE SHOULD KEEP MUCH OF THE CWA DRY. HOWEVER...THERE ARE INDICATIONS OF SOME WARM ADVECTION LIGHT SNOW OCCURRING OVER LAKE SUPERIOR...POSSIBLY CLIPPING THE KEWEENAW... ENOUGH TO MAINTAIN GOING CHC POPS. OTHERWISE...LOW CLOUDS WILL MOVE OVER THE REST OF THE CWA. HAVE DECLINED TO MENTION ANY FREEZING DRIZZLE AS SOUNDINGS DO NOT INDICATE MUCH LIFT WITHIN THE LOW CLOUDS...AND THE FACT THAT VERY FEW FZDZ REPORTS HAVE OCCURRED UPSTREAM. WITH THE WARM ADVECTION...HIGHS SHOULD BE A BIT WARMER TODAY EVEN WITH ALL OF THE CLOUDS. HAVE FOLLOWED CLOSE TO MAV GUIDANCE...WHICH SEEMS A BIT MORE REALISTIC GIVEN READINGS SEEN UPSTREAM. TONIGHT...MODELS TAKE THE UPPER TROUGH IN MANITOBA SOUTHWARD AS IT BEGINS TO INTERACT WITH THE OTHER SHRTWV TROUGH COMING OUT OF THE NRN ROCKIES. BY 12Z MON...THE UPPER TROUGH IS IN FAR WRN ONTARIO AND MN...WHILE THE NRN ROCKIES TROUGH SHIFTS INTO IOWA AND NRN IL. WITH THE UPPER TROUGH APPROACHING THE CWA...MID-LEVEL HEIGHTS FALL (500MB DROP OF 90-120 METERS). MOISTURE SHOULD INCREASE MORE AHEAD OF THE TROUGH AS WELL...SO THE HEIGHT FALLS ARE EXPECTED TO BREAK OUT LIGHT PCPN OVER THE CWA. SINCE THE OVERALL MOISTURE IS NOT PROGGED TO BE THAT GREAT...WITH PRECIPITABLE WATER VALUES AROUND 0.40 OF AN INCH OR JUST SLIGHTLY ABOVE NORMAL...ONLY A FEW HUNDREDTHS OF LIQUID EQUIVALENT IS EXPECTED. PCPN ON LAND SHOULD BE IN THE FORM OF SNOW...BUT WET-BULB ZERO HEIGHTS FROM THE NAM/LOCAL WRF-ARW/GFS SUGGEST POTENTIAL FOR SOME RAIN TO MIX IN...ESPECIALLY ON EASTERN SUPERIOR WHERE GREATER HEAT FLUX OFF THE WARMER WATER OCCURS. SOME LAKE ENHANCEMENT COULD OCCUR LATE OUT WEST...WITH 850MB TEMPS SHOWN TO DROP TO -8 TO -10C AND WINDS TURNING NW BEHIND A SFC LOW CROSSING EASTERN LAKE SUPERIOR. WITH PLENTY OF CLOUDS...TEMPS WILL BE DICTATED BY THE COLD ADVECTION OCCURRING DURING THE NIGHT. AGAIN... FOLLOWED CLOSE TO MET/MAV GUIDANCE. MONDAY...THE UPPER TROUGH DROPPING SOUTH OUT OF FAR WRN ONTARIO AND MN IS PROGGED TO CONTINUE TO INTERACT WITH THE SHRTWV TROUGH...WITH AN UPPER LOW SITUATED SOMEWHERE NEAR THE IWD AREA BY 00Z TUE. IT SHOULD BE NOTED THAT THE SHRTWV TROUGH CROSSING NRN IL IS STILL PRESENT...OVER INDIANA AND OHIO BY 00Z...SUGGESTING THAT THE TWO TROUGHS HAVE NOT PHASED YET. NONETHELESS...THE SFC LOW THAT WAS CROSSING INTO ERN LAKE SUPERIOR REDEVELOPS AND STRENGTHENS TO AROUND 1005MB NEAR DTX AT 00Z. THE TRACK OF THE LOW MEANS AN INCREASING NW TO NORTH WIND THROUGH THE DAY...ALLOWING CONTINUED COOLING OF THE AIR OVER THE CWA. HOWEVER...850MB TEMPS GENERALLY ONLY DROP TO AROUND -8C ACROSS THE ENTIRE CWA. BETTER COOLING...DOWN TO -12 TO -14C...STAYS OUT TO THE WEST OVER MN...THOUGH -8C IS SUFFICIENT ENOUGH TO PRODUCE SOME LAKE EFFECT CLOUDS OR LIGHT SNOW SHOWERS. THE GREATEST PROBABILITY FOR THAT TO OCCUR WOULD BE IN THE EASTERN CWA WHICH WILL STILL BE IN A HEIGHT FALL SCENARIO EAST OF THE UPPER LOW. IN FACT...HAVE ENOUGH CONFIDENCE TO GO LIKELY IN THIS AREA. ACCUMULATION AMOUNTS OF AN INCH OR TWO SHOULD BE THE RULE WITH SOUNDINGS SUGGESTING WET SNOW. SOME OF THE SNOW AGAIN COULD MIX WITH RAIN OVER THE WATER AND EVEN ALONG THE EASTERN LAKE SUPERIOR SHORELINE...WITH THE INCREASING WIND PRODUCING MORE HEAT FLUX. GIVEN THE COLD ADVECTION AND PLENTY OF CLOUDS ASSOCIATED WITH THE UPPER LOW AND OFF LAKE SUPERIOR...TEMPS MAY STRUGGLE TO RISE MUCH...MAYBE ABOUT 10 DEGREES. WARMEST AREAS EXPECTED IN THE SOUTH CENTRAL WITH NW WINDS DOWNSLOPING AND ALONG THE EASTERN LAKE SUPERIOR SHORELINE. MON NIGHT INTO TUE...MODELS ARE IN GOOD AGREEMENT TAKING THE UPPER LOW QUICKLY TO THE SE...REACHING LAKE ERIE BY 12Z TUE AND THEN TO NEW YORK STATE BY 00Z WED. THIS MEANS GRADUAL HEIGHT RISES ALOFT THROUGH THE PERIOD...WHICH IS NOTED BY RH FIELDS SHOWING DRY ADVECTION ALOFT AS SUBSIDENCE INCREASES. HOWEVER...MOIST COOL LOW LEVEL AIR BEING DRIVEN SOUTH MON NIGHT WILL MEAN A FAVORABLE LAKE ENHANCED/UPSLOPE SETUP. HAVE INCREASED POPS TO LIKELY IN THE FAVORED NORTHERLY FLOW AREAS...IN ADDITION TO THE SE U.P. SINCE THE WINDS ARE PROGGED TO BE STRONG ENOUGH TO DRIVE ENHANCED BANDS INLAND. PCPN SHOULD BE IN THE FORM OF SNOW...THOUGH POSSIBLY MIXED WITH RAIN IN THE EVENING NEAR LAKE SUPERIOR UNTIL ENOUGH COOLING CAN TAKE PLACE TO SWITCH IT ALL TO SNOW. GREATEST AMOUNT OF PCPN EXPECTED IN UPSLOPE AREAS OF THE NORTH CENTRAL U.P....BUT LOW SNOW TO WATER RATIOS (10 TO 1 OR POSSIBLY EVEN LESS) SUGGESTS ONLY AN INCH OR TWO OF ACCUMULATION. PCPN SHOULD DIMINISH WEST TO EAST SOMEWHAT THROUGH THE DAY ON TUE...ENOUGH THAT POPS REMAIN IN THE CHANCE CATEGORY... THOUGH STILL HIGH IN THE UPSLOPE AREAS OF MQT/ALGER COUNTIES. SOUNDINGS SUGGEST THAT THE -10C ISOTHERM MAY DRY OUT ENOUGH... PARTICULARLY FROM THE NAM...THAT THE SNOW COULD CHANGE TO DZ IN THE AFTN. DAY SHIFT WILL NEED TO LOOK AT THIS AGAIN TO SEE IF MODELS TREND TOWARDS THIS IDEA. TEMPERATURE WISE...READINGS SHOULD NOT GET TOO CHILLY MON NIGHT THANKS TO CLOUDS AND WIND. MOST LOCATIONS SHOULD FALL INTO THE 20S...AND THOSE NEAR LAKE SUPERIOR MAY ONLY BOTTOM OUT AT 30. THE CLIMB ON TUE EXPECTED AGAIN OF 5 TO 10 DEGREES...WARMEST SOUTH CENTRAL WITH DOWNSLOPING. TUE NIGHT INTO WED...MAIN CONCERN FOR THIS PERIOD IS FZDZ. UPPER TROUGH/LOW REMAIN GENERALLY IN PLACE OVER NEW YORK STATE OR JUST MOVING SLIGHTLY NORTH INTO EASTERN ONTARIO DURING THIS PERIOD. RH PROFILES SHOW CONTINUED DRY ADVECTION ALOFT AND LOWERING INVERSIONS...WHICH RESULTS IN TRAPPED LOW LEVEL MOISTURE DURING THIS PERIOD. AT THE SFC...THE AREA IS STUCK BETWEEN A RIDGE BUILDING IN FROM MN AND A LOW IN EASTERN ONTARIO ASSOCIATED WITH THE UPPER LOW...RESULTING IN CONTINUED NORTH TO NW WINDS OVER THE CWA. WITH THE LOW CLOUDS AND THE WIND DIRECTION...ALONG WITH THE FACT THAT 900MB TEMPS AROUND -8C ARE FAVORABLE FOR LAKE ENHANCEMENT...SOME LIGHT PCPN IS POSSIBLE...ESPECIALLY IN UPSLOPE AREAS. SOUNDINGS SUGGEST THAT THE -10C ISOTHERM WILL DRY OUT...WHICH MEANS EITHER FZDZ OR -SHSN ARE POSSIBLE. HAVE INCLUDED THE FZDZ NOW ONLY IN UPSLOPE AREAS WHERE THE GREATER PROBABILITY OF IT OCCURRING EXISTS. FUTURE SHIFTS WILL NEED TO SEE IF FZDZ IS NEEDED ELSEWHERE. THE CHANCES FOR -SHSN/FZDZ ARE CONFINED TO TUE NIGHT THROUGH WED MORNING. AFTER WED MORNING...IT APPEARS THERE SHOULD BE ENOUGH DRYING BOTH BELOW THE CLOUDS AND ALOFT TO END THE NEED FOR CHANCE POPS. WILL NEED TO WATCH THE UPPER TROUGH/LOW...WITH SUGGESTIONS BY THE ECMWF OF IT ROTATING BACK FARTHER WEST FOR THE NEED TO INCLUDE POPS FOR THE EASTERN CWA. TEMPS TUE NIGHT EXPECTED TO BE A FEW DEGREES COOLER THAN MON NIGHT...COLDEST IN FAR WRN UPPER MI CLOSER TO THE SFC RIDGE. HIGHS ON WED SHOULD BE CLOSE TO NORMAL. BEYOND WED...NO CHANGES MADE. LOOKS LIKE IN THE MEAN FROM THE 00Z ECMWF/GFS/GFS ENSEMBLES THAT THE CWA WILL REMAIN IN UPPER TROUGH THROUGH THE NEXT 7 TO 10 DAYS. OVER TIME...THE TROUGHING GETS COOLER...BUT REALLY NOTHING TOO COLD EVIDENT. && .AVIATION (FOR THE 18Z TAF ISSUANCE)... OTHER THAN VFR CONDITIONS TO START THE PERIOD AT SAW...MVFR CIGS SHOULD PREVAIL AT KCMX/KSAW THROUGH THIS FORECAST PERIOD. A TROUGH WILL SWEEP ACROSS THE CWA TONIGHT...POSSIBLY BRINGING IFR TO LOW END MVFR -SN. THEN...AS NORTHWEST TO NORTHERLY FLOW SETS UP AND COLD AIR MOVES IN ALOFT...-SHSN WILL BECOME POSSIBLE...MAINLY AT CMX AFTER 15Z. && .MARINE (FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)... WITH LOW PRES DROPPING SE TOWARD THE UPPER LAKES TODAY...EXPECT SWRLY WINDS ACROSS LAKE SUPERIOR IN THE 15-25KT RANGE WITH GUSTS TO 30KT. AS THE LOW SETTLES SE TOWARD THE LOWER LAKES...REORGANIZES AND STRENGTHENS SOME...EXPECT NRLY WINDS IN THE 15-30KT RANGE LATE MON AFTN THRU TUE WITH THE STRONGEST WINDS OVER THE E HALF OF THE LAKE. IT`S NOT OUT OF THE QUESTION THAT SOME GALE FORCE GUSTS COULD OCCUR...BUT SINCE COLD AIR ADVECTION IS WEAK...WILL HOLD OFF ON A MENTION OF GALES AT THIS TIME. WINDS WILL VERY SLOWLY DIMINISH WED/THU AS PROGRESSION OF SYSTEMS SLOWS TO A CRAWL. STRONGEST WINDS WILL REMAIN OVER ERN LAKE SUPERIOR WED/THU. && .MQT WATCHES/WARNINGS/ADVISORIES... UPPER MICHIGAN...NONE. LAKE SUPERIOR...NONE. LAKE MICHIGAN...NONE. && $$ SYNOPSIS/DISCUSSION...AJ AVIATION...KF MARINE...ROLFSON mi AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE MARQUETTE MI 645 AM EST SUN NOV 23 2008 UPDATED AVIATION DISCUSSION FOR 12Z TAF ISSUANCE .SYNOPSIS... ISSUED AT 408 AM EST 08Z WATER VAPOR LOOP AND RUC 500MB HEIGHT ANALYSIS SHOWED A SOMEWHAT PROGRESSIVE FLOW FROM THE PACIFIC ACROSS THE NORTHERN U.S....WHICH THEN SLOWS DOWN IN SE CANADA AND THE NORTHEAST U.S. WHERE A FAIRLY DEEP TROUGH EXISTS. WITHIN THE PROGRESSIVE FLOW...THERE ARE TWO SHRTWV TROUGHS TO NOTE...ONE OVER IDAHO AND A SECOND MORE WRAPPED UP ONE CROSSING NRN SASKATCHEWAN. A THIRD...BUT MUCH WEAKER SHRTWV IS MAKING ITS WAY SE INTO NRN LAKE SUPERIOR...ON THE EAST SIDE OF AN UPPER RIDGE BEING BUILT UP AHEAD OF THE SRN CANADA SHRTWV TROUGH. THIS WEAK SHRTWV IS NOT HAVING MUCH IMPACT BESIDES A FEW HIGH CLOUDS CROSSING THE EASTERN CWA...DUE TO DRY LOW TO MID-LEVEL AIR SEEN ON THE 00Z SOUNDINGS FROM APX AND GRB. THIS DRY AIR AND SOME CLEAR SKIES...ALONG WITH LIGHT WINDS ASSOCIATED WITH A SURFACE RIDGE... ALLOWED LOCATIONS IN DELTA COUNTY TO DROP TO NEAR ZERO DURING THE EVENING. HOWEVER...THE RIDGE HAS MOVED EAST...ALLOWING RETURN SOUTHERLY FLOW TO BRING READINGS BACK UP. THE SOUTHERLY FLOW IS ALSO BRINGING SOME STRATUS WITH IT...NOW COVERING ALL OF MN INTO WRN WI AND WRN UPPER MI. 00Z INL SOUNDING SHOWS THE STRATUS WITH A SATURATED LAYER BTWN 800-925MB...WHILE THE REST OF THE SOUNDING IS DRY. SOME FREEZING DRIZZLE EVEN OCCURRED AT GFK AT 03Z...BUT NO OTHER FZDZ REPORTS HAVE OCCURRED. OTHERWISE...THE WARM ADVECTION AHEAD OF THE SHRTWV IN CENTRAL CANADA IS NOT PRODUCING MUCH PCPN. 850MB TEMPS ASSOCIATED WITH THE ADVECTION ARE DEFINITELY WARMER THAN THEY HAVE BEEN OVER THE CWA...3C AT BIS AND 1C AT CYQD...COMPARED TO -8C AT CWPL AND -7C AT APX. FARTHER TO THE WEST WITH THE OTHER SHRTWV TROUGH...SOME -SN IS CROSSING ERN MT. && .DISCUSSION... ISSUED AT 408 AM EST TODAY...UPPER TROUGH OVER SASKATCHEWAN IS PROGGED TO DEEPEN AND MOVE INTO MANITOBA BY 00Z MON. AS THE TROUGH MOVES EAST...THE BUILDING RIDGE OVER THE UPPER MISSISSIPPI VALLEY WILL MOVE OVER UPPER MI. SUBSIDENCE UNDER THE UPPER RIDGE SHOULD KEEP MUCH OF THE CWA DRY. HOWEVER...THERE ARE INDICATIONS OF SOME WARM ADVECTION LIGHT SNOW OCCURRING OVER LAKE SUPERIOR...POSSIBLY CLIPPING THE KEWEENAW... ENOUGH TO MAINTAIN GOING CHC POPS. OTHERWISE...LOW CLOUDS WILL MOVE OVER THE REST OF THE CWA. HAVE DECLINED TO MENTION ANY FREEZING DRIZZLE AS SOUNDINGS DO NOT INDICATE MUCH LIFT WITHIN THE LOW CLOUDS...AND THE FACT THAT VERY FEW FZDZ REPORTS HAVE OCCURRED UPSTREAM. WITH THE WARM ADVECTION...HIGHS SHOULD BE A BIT WARMER TODAY EVEN WITH ALL OF THE CLOUDS. HAVE FOLLOWED CLOSE TO MAV GUIDANCE...WHICH SEEMS A BIT MORE REALISTIC GIVEN READINGS SEEN UPSTREAM. TONIGHT...MODELS TAKE THE UPPER TROUGH IN MANITOBA SOUTHWARD AS IT BEGINS TO INTERACT WITH THE OTHER SHRTWV TROUGH COMING OUT OF THE NRN ROCKIES. BY 12Z MON...THE UPPER TROUGH IS IN FAR WRN ONTARIO AND MN...WHILE THE NRN ROCKIES TROUGH SHIFTS INTO IOWA AND NRN IL. WITH THE UPPER TROUGH APPROACHING THE CWA...MID-LEVEL HEIGHTS FALL (500MB DROP OF 90-120 METERS). MOISTURE SHOULD INCREASE MORE AHEAD OF THE TROUGH AS WELL...SO THE HEIGHT FALLS ARE EXPECTED TO BREAK OUT LIGHT PCPN OVER THE CWA. SINCE THE OVERALL MOISTURE IS NOT PROGGED TO BE THAT GREAT...WITH PRECIPITABLE WATER VALUES AROUND 0.40 OF AN INCH OR JUST SLIGHTLY ABOVE NORMAL...ONLY A FEW HUNDREDTHS OF LIQUID EQUIVALENT IS EXPECTED. PCPN ON LAND SHOULD BE IN THE FORM OF SNOW...BUT WET-BULB ZERO HEIGHTS FROM THE NAM/LOCAL WRF-ARW/GFS SUGGEST POTENTIAL FOR SOME RAIN TO MIX IN...ESPECIALLY ON EASTERN SUPERIOR WHERE GREATER HEAT FLUX OFF THE WARMER WATER OCCURS. SOME LAKE ENHANCEMENT COULD OCCUR LATE OUT WEST...WITH 850MB TEMPS SHOWN TO DROP TO -8 TO -10C AND WINDS TURNING NW BEHIND A SFC LOW CROSSING EASTERN LAKE SUPERIOR. WITH PLENTY OF CLOUDS...TEMPS WILL BE DICTATED BY THE COLD ADVECTION OCCURRING DURING THE NIGHT. AGAIN... FOLLOWED CLOSE TO MET/MAV GUIDANCE. MONDAY...THE UPPER TROUGH DROPPING SOUTH OUT OF FAR WRN ONTARIO AND MN IS PROGGED TO CONTINUE TO INTERACT WITH THE SHRTWV TROUGH...WITH AN UPPER LOW SITUATED SOMEWHERE NEAR THE IWD AREA BY 00Z TUE. IT SHOULD BE NOTED THAT THE SHRTWV TROUGH CROSSING NRN IL IS STILL PRESENT...OVER INDIANA AND OHIO BY 00Z...SUGGESTING THAT THE TWO TROUGHS HAVE NOT PHASED YET. NONETHELESS...THE SFC LOW THAT WAS CROSSING INTO ERN LAKE SUPERIOR REDEVELOPS AND STRENGTHENS TO AROUND 1005MB NEAR DTX AT 00Z. THE TRACK OF THE LOW MEANS AN INCREASING NW TO NORTH WIND THROUGH THE DAY...ALLOWING CONTINUED COOLING OF THE AIR OVER THE CWA. HOWEVER...850MB TEMPS GENERALLY ONLY DROP TO AROUND -8C ACROSS THE ENTIRE CWA. BETTER COOLING...DOWN TO -12 TO -14C...STAYS OUT TO THE WEST OVER MN...THOUGH -8C IS SUFFICIENT ENOUGH TO PRODUCE SOME LAKE EFFECT CLOUDS OR LIGHT SNOW SHOWERS. THE GREATEST PROBABILITY FOR THAT TO OCCUR WOULD BE IN THE EASTERN CWA WHICH WILL STILL BE IN A HEIGHT FALL SCENARIO EAST OF THE UPPER LOW. IN FACT...HAVE ENOUGH CONFIDENCE TO GO LIKELY IN THIS AREA. ACCUMULATION AMOUNTS OF AN INCH OR TWO SHOULD BE THE RULE WITH SOUNDINGS SUGGESTING WET SNOW. SOME OF THE SNOW AGAIN COULD MIX WITH RAIN OVER THE WATER AND EVEN ALONG THE EASTERN LAKE SUPERIOR SHORELINE...WITH THE INCREASING WIND PRODUCING MORE HEAT FLUX. GIVEN THE COLD ADVECTION AND PLENTY OF CLOUDS ASSOCIATED WITH THE UPPER LOW AND OFF LAKE SUPERIOR...TEMPS MAY STRUGGLE TO RISE MUCH...MAYBE ABOUT 10 DEGREES. WARMEST AREAS EXPECTED IN THE SOUTH CENTRAL WITH NW WINDS DOWNSLOPING AND ALONG THE EASTERN LAKE SUPERIOR SHORELINE. MON NIGHT INTO TUE...MODELS ARE IN GOOD AGREEMENT TAKING THE UPPER LOW QUICKLY TO THE SE...REACHING LAKE ERIE BY 12Z TUE AND THEN TO NEW YORK STATE BY 00Z WED. THIS MEANS GRADUAL HEIGHT RISES ALOFT THROUGH THE PERIOD...WHICH IS NOTED BY RH FIELDS SHOWING DRY ADVECTION ALOFT AS SUBSIDENCE INCREASES. HOWEVER...MOIST COOL LOW LEVEL AIR BEING DRIVEN SOUTH MON NIGHT WILL MEAN A FAVORABLE LAKE ENHANCED/UPSLOPE SETUP. HAVE INCREASED POPS TO LIKELY IN THE FAVORED NORTHERLY FLOW AREAS...IN ADDITION TO THE SE U.P. SINCE THE WINDS ARE PROGGED TO BE STRONG ENOUGH TO DRIVE ENHANCED BANDS INLAND. PCPN SHOULD BE IN THE FORM OF SNOW...THOUGH POSSIBLY MIXED WITH RAIN IN THE EVENING NEAR LAKE SUPERIOR UNTIL ENOUGH COOLING CAN TAKE PLACE TO SWITCH IT ALL TO SNOW. GREATEST AMOUNT OF PCPN EXPECTED IN UPSLOPE AREAS OF THE NORTH CENTRAL U.P....BUT LOW SNOW TO WATER RATIOS (10 TO 1 OR POSSIBLY EVEN LESS) SUGGESTS ONLY AN INCH OR TWO OF ACCUMULATION. PCPN SHOULD DIMINISH WEST TO EAST SOMEWHAT THROUGH THE DAY ON TUE...ENOUGH THAT POPS REMAIN IN THE CHANCE CATEGORY... THOUGH STILL HIGH IN THE UPSLOPE AREAS OF MQT/ALGER COUNTIES. SOUNDINGS SUGGEST THAT THE -10C ISOTHERM MAY DRY OUT ENOUGH... PARTICULARLY FROM THE NAM...THAT THE SNOW COULD CHANGE TO DZ IN THE AFTN. DAY SHIFT WILL NEED TO LOOK AT THIS AGAIN TO SEE IF MODELS TREND TOWARDS THIS IDEA. TEMPERATURE WISE...READINGS SHOULD NOT GET TOO CHILLY MON NIGHT THANKS TO CLOUDS AND WIND. MOST LOCATIONS SHOULD FALL INTO THE 20S...AND THOSE NEAR LAKE SUPERIOR MAY ONLY BOTTOM OUT AT 30. THE CLIMB ON TUE EXPECTED AGAIN OF 5 TO 10 DEGREES...WARMEST SOUTH CENTRAL WITH DOWNSLOPING. TUE NIGHT INTO WED...MAIN CONCERN FOR THIS PERIOD IS FZDZ. UPPER TROUGH/LOW REMAIN GENERALLY IN PLACE OVER NEW YORK STATE OR JUST MOVING SLIGHTLY NORTH INTO EASTERN ONTARIO DURING THIS PERIOD. RH PROFILES SHOW CONTINUED DRY ADVECTION ALOFT AND LOWERING INVERSIONS...WHICH RESULTS IN TRAPPED LOW LEVEL MOISTURE DURING THIS PERIOD. AT THE SFC...THE AREA IS STUCK BETWEEN A RIDGE BUILDING IN FROM MN AND A LOW IN EASTERN ONTARIO ASSOCIATED WITH THE UPPER LOW...RESULTING IN CONTINUED NORTH TO NW WINDS OVER THE CWA. WITH THE LOW CLOUDS AND THE WIND DIRECTION...ALONG WITH THE FACT THAT 900MB TEMPS AROUND -8C ARE FAVORABLE FOR LAKE ENHANCEMENT...SOME LIGHT PCPN IS POSSIBLE...ESPECIALLY IN UPSLOPE AREAS. SOUNDINGS SUGGEST THAT THE -10C ISOTHERM WILL DRY OUT...WHICH MEANS EITHER FZDZ OR -SHSN ARE POSSIBLE. HAVE INCLUDED THE FZDZ NOW ONLY IN UPSLOPE AREAS WHERE THE GREATER PROBABILITY OF IT OCCURRING EXISTS. FUTURE SHIFTS WILL NEED TO SEE IF FZDZ IS NEEDED ELSEWHERE. THE CHANCES FOR -SHSN/FZDZ ARE CONFINED TO TUE NIGHT THROUGH WED MORNING. AFTER WED MORNING...IT APPEARS THERE SHOULD BE ENOUGH DRYING BOTH BELOW THE CLOUDS AND ALOFT TO END THE NEED FOR CHANCE POPS. WILL NEED TO WATCH THE UPPER TROUGH/LOW...WITH SUGGESTIONS BY THE ECMWF OF IT ROTATING BACK FARTHER WEST FOR THE NEED TO INCLUDE POPS FOR THE EASTERN CWA. TEMPS TUE NIGHT EXPECTED TO BE A FEW DEGREES COOLER THAN MON NIGHT...COLDEST IN FAR WRN UPPER MI CLOSER TO THE SFC RIDGE. HIGHS ON WED SHOULD BE CLOSE TO NORMAL. BEYOND WED...NO CHANGES MADE. LOOKS LIKE IN THE MEAN FROM THE 00Z ECMWF/GFS/GFS ENSEMBLES THAT THE CWA WILL REMAIN IN UPPER TROUGH THROUGH THE NEXT 7 TO 10 DAYS. OVER TIME...THE TROUGHING GETS COOLER...BUT REALLY NOTHING TOO COLD EVIDENT. && .AVIATION (FOR THE 12Z TAF ISSUANCE)... MVFR CIGS SHOULD PREVAIL AT KCMX/KSAW THRU THIS FCST PERIOD AS AREA OF STRATOCU/STRATUS PER SATELLITE IMAGERY CONTINUES TO ADVECT INTO THE AREA AHEAD OF LOW PRES DROPPING SE TOWARD THE GREAT LAKES. SATELLITE IMAGERY ALSO SUGGESTS THAT KSAW MAY BE ON THE SRN EDGE OF THE STRATOCU AREA THIS AFTN AND MAY BREAK OUT INTO VFR CONDITIONS FOR A WHILE. LOW CONFIDENCE ON THAT OCCURRING...SO KEPT WITH AN MVFR FCST DURING THE AFTN. TROF WILL SWEEP ACROSS THE AREA OVERNIGHT TONIGHT. MAY SEE A PERIOD OF IFR CIGS/MVFR VIS IN -SN AT KCMX AS WINDS SHIFT TO AN UPSLOPING WRLY DIRECTION. -SN LATE IN THE NIGHT AT KSAW SHOULD BE LIGHT ENOUGH FOR VIS TO REMAIN VFR. && .MARINE (FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)... WITH LOW PRES DROPPING SE TOWARD THE UPPER LAKES TODAY...EXPECT SWRLY WINDS ACROSS LAKE SUPERIOR IN THE 15-25KT RANGE WITH GUSTS TO 30KT. AS THE LOW SETTLES SE TOWARD THE LOWER LAKES...REORGANIZES AND STRENGTHENS SOME...EXPECT NRLY WINDS IN THE 15-30KT RANGE LATE MON AFTN THRU TUE WITH THE STRONGEST WINDS OVER THE E HALF OF THE LAKE. IT`S NOT OUT OF THE QUESTION THAT SOME GALE FORCE GUSTS COULD OCCUR...BUT SINCE COLD AIR ADVECTION IS WEAK...WILL HOLD OFF ON A MENTION OF GALES AT THIS TIME. WINDS WILL VERY SLOWLY DIMINISH WED/THU AS PROGRESSION OF SYSTEMS SLOWS TO A CRAWL. STRONGEST WINDS WILL REMAIN OVER ERN LAKE SUPERIOR WED/THU. && .MQT WATCHES/WARNINGS/ADVISORIES... UPPER MICHIGAN...NONE. LAKE SUPERIOR...NONE. LAKE MICHIGAN...NONE. && $$ SYNOPSIS/DISCUSSION...AJ AVIATION...ROLFSON MARINE...ROLFSON mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MARQUETTE MI 408 AM EST SUN NOV 23 2008 .SYNOPSIS... 08Z WATER VAPOR LOOP AND RUC 500MB HEIGHT ANALYSIS SHOWED A SOMEWHAT PROGRESSIVE FLOW FROM THE PACIFIC ACROSS THE NORTHERN U.S....WHICH THEN SLOWS DOWN IN SE CANADA AND THE NORTHEAST U.S. WHERE A FAIRLY DEEP TROUGH EXISTS. WITHIN THE PROGRESSIVE FLOW...THERE ARE TWO SHRTWV TROUGHS TO NOTE...ONE OVER IDAHO AND A SECOND MORE WRAPPED UP ONE CROSSING NRN SASKATCHEWAN. A THIRD...BUT MUCH WEAKER SHRTWV IS MAKING ITS WAY SE INTO NRN LAKE SUPERIOR...ON THE EAST SIDE OF AN UPPER RIDGE BEING BUILT UP AHEAD OF THE SRN CANADA SHRTWV TROUGH. THIS WEAK SHRTWV IS NOT HAVING MUCH IMPACT BESIDES A FEW HIGH CLOUDS CROSSING THE EASTERN CWA...DUE TO DRY LOW TO MID-LEVEL AIR SEEN ON THE 00Z SOUNDINGS FROM APX AND GRB. THIS DRY AIR AND SOME CLEAR SKIES...ALONG WITH LIGHT WINDS ASSOCIATED WITH A SURFACE RIDGE... ALLOWED LOCATIONS IN DELTA COUNTY TO DROP TO NEAR ZERO DURING THE EVENING. HOWEVER...THE RIDGE HAS MOVED EAST...ALLOWING RETURN SOUTHERLY FLOW TO BRING READINGS BACK UP. THE SOUTHERLY FLOW IS ALSO BRINGING SOME STRATUS WITH IT...NOW COVERING ALL OF MN INTO WRN WI AND WRN UPPER MI. 00Z INL SOUNDING SHOWS THE STRATUS WITH A SATURATED LAYER BTWN 800-925MB...WHILE THE REST OF THE SOUNDING IS DRY. SOME FREEZING DRIZZLE EVEN OCCURRED AT GFK AT 03Z...BUT NO OTHER FZDZ REPORTS HAVE OCCURRED. OTHERWISE...THE WARM ADVECTION AHEAD OF THE SHRTWV IN CENTRAL CANADA IS NOT PRODUCING MUCH PCPN. 850MB TEMPS ASSOCIATED WITH THE ADVECTION ARE DEFINITELY WARMER THAN THEY HAVE BEEN OVER THE CWA...3C AT BIS AND 1C AT CYQD...COMPARED TO -8C AT CWPL AND -7C AT APX. FARTHER TO THE WEST WITH THE OTHER SHRTWV TROUGH...SOME -SN IS CROSSING ERN MT. && .DISCUSSION... TODAY...UPPER TROUGH OVER SASKATCHEWAN IS PROGGED TO DEEPEN AND MOVE INTO MANITOBA BY 00Z MON. AS THE TROUGH MOVES EAST...THE BUILDING RIDGE OVER THE UPPER MISSISSIPPI VALLEY WILL MOVE OVER UPPER MI. SUBSIDENCE UNDER THE UPPER RIDGE SHOULD KEEP MUCH OF THE CWA DRY. HOWEVER...THERE ARE INDICATIONS OF SOME WARM ADVECTION LIGHT SNOW OCCURRING OVER LAKE SUPERIOR...POSSIBLY CLIPPING THE KEWEENAW... ENOUGH TO MAINTAIN GOING CHC POPS. OTHERWISE...LOW CLOUDS WILL MOVE OVER THE REST OF THE CWA. HAVE DECLINED TO MENTION ANY FREEZING DRIZZLE AS SOUNDINGS DO NOT INDICATE MUCH LIFT WITHIN THE LOW CLOUDS...AND THE FACT THAT VERY FEW FZDZ REPORTS HAVE OCCURRED UPSTREAM. WITH THE WARM ADVECTION...HIGHS SHOULD BE A BIT WARMER TODAY EVEN WITH ALL OF THE CLOUDS. HAVE FOLLOWED CLOSE TO MAV GUIDANCE...WHICH SEEMS A BIT MORE REALISTIC GIVEN READINGS SEEN UPSTREAM. TONIGHT...MODELS TAKE THE UPPER TROUGH IN MANITOBA SOUTHWARD AS IT BEGINS TO INTERACT WITH THE OTHER SHRTWV TROUGH COMING OUT OF THE NRN ROCKIES. BY 12Z MON...THE UPPER TROUGH IS IN FAR WRN ONTARIO AND MN...WHILE THE NRN ROCKIES TROUGH SHIFTS INTO IOWA AND NRN IL. WITH THE UPPER TROUGH APPROACHING THE CWA...MID-LEVEL HEIGHTS FALL (500MB DROP OF 90-120 METERS). MOISTURE SHOULD INCREASE MORE AHEAD OF THE TROUGH AS WELL...SO THE HEIGHT FALLS ARE EXPECTED TO BREAK OUT LIGHT PCPN OVER THE CWA. SINCE THE OVERALL MOISTURE IS NOT PROGGED TO BE THAT GREAT...WITH PRECIPITABLE WATER VALUES AROUND 0.40 OF AN INCH OR JUST SLIGHTLY ABOVE NORMAL...ONLY A FEW HUNDREDTHS OF LIQUID EQUIVALENT IS EXPECTED. PCPN ON LAND SHOULD BE IN THE FORM OF SNOW...BUT WET-BULB ZERO HEIGHTS FROM THE NAM/LOCAL WRF-ARW/GFS SUGGEST POTENTIAL FOR SOME RAIN TO MIX IN...ESPECIALLY ON EASTERN SUPERIOR WHERE GREATER HEAT FLUX OFF THE WARMER WATER OCCURS. SOME LAKE ENHANCEMENT COULD OCCUR LATE OUT WEST...WITH 850MB TEMPS SHOWN TO DROP TO -8 TO -10C AND WINDS TURNING NW BEHIND A SFC LOW CROSSING EASTERN LAKE SUPERIOR. WITH PLENTY OF CLOUDS...TEMPS WILL BE DICTATED BY THE COLD ADVECTION OCCURRING DURING THE NIGHT. AGAIN... FOLLOWED CLOSE TO MET/MAV GUIDANCE. MONDAY...THE UPPER TROUGH DROPPING SOUTH OUT OF FAR WRN ONTARIO AND MN IS PROGGED TO CONTINUE TO INTERACT WITH THE SHRTWV TROUGH...WITH AN UPPER LOW SITUATED SOMEWHERE NEAR THE IWD AREA BY 00Z TUE. IT SHOULD BE NOTED THAT THE SHRTWV TROUGH CROSSING NRN IL IS STILL PRESENT...OVER INDIANA AND OHIO BY 00Z...SUGGESTING THAT THE TWO TROUGHS HAVE NOT PHASED YET. NONETHELESS...THE SFC LOW THAT WAS CROSSING INTO ERN LAKE SUPERIOR REDEVELOPS AND STRENGTHENS TO AROUND 1005MB NEAR DTX AT 00Z. THE TRACK OF THE LOW MEANS AN INCREASING NW TO NORTH WIND THROUGH THE DAY...ALLOWING CONTINUED COOLING OF THE AIR OVER THE CWA. HOWEVER...850MB TEMPS GENERALLY ONLY DROP TO AROUND -8C ACROSS THE ENTIRE CWA. BETTER COOLING...DOWN TO -12 TO -14C...STAYS OUT TO THE WEST OVER MN...THOUGH -8C IS SUFFICIENT ENOUGH TO PRODUCE SOME LAKE EFFECT CLOUDS OR LIGHT SNOW SHOWERS. THE GREATEST PROBABILITY FOR THAT TO OCCUR WOULD BE IN THE EASTERN CWA WHICH WILL STILL BE IN A HEIGHT FALL SCENARIO EAST OF THE UPPER LOW. IN FACT...HAVE ENOUGH CONFIDENCE TO GO LIKELY IN THIS AREA. ACCUMULATION AMOUNTS OF AN INCH OR TWO SHOULD BE THE RULE WITH SOUNDINGS SUGGESTING WET SNOW. SOME OF THE SNOW AGAIN COULD MIX WITH RAIN OVER THE WATER AND EVEN ALONG THE EASTERN LAKE SUPERIOR SHORELINE...WITH THE INCREASING WIND PRODUCING MORE HEAT FLUX. GIVEN THE COLD ADVECTION AND PLENTY OF CLOUDS ASSOCIATED WITH THE UPPER LOW AND OFF LAKE SUPERIOR...TEMPS MAY STRUGGLE TO RISE MUCH...MAYBE ABOUT 10 DEGREES. WARMEST AREAS EXPECTED IN THE SOUTH CENTRAL WITH NW WINDS DOWNSLOPING AND ALONG THE EASTERN LAKE SUPERIOR SHORELINE. MON NIGHT INTO TUE...MODELS ARE IN GOOD AGREEMENT TAKING THE UPPER LOW QUICKLY TO THE SE...REACHING LAKE ERIE BY 12Z TUE AND THEN TO NEW YORK STATE BY 00Z WED. THIS MEANS GRADUAL HEIGHT RISES ALOFT THROUGH THE PERIOD...WHICH IS NOTED BY RH FIELDS SHOWING DRY ADVECTION ALOFT AS SUBSIDENCE INCREASES. HOWEVER...MOIST COOL LOW LEVEL AIR BEING DRIVEN SOUTH MON NIGHT WILL MEAN A FAVORABLE LAKE ENHANCED/UPSLOPE SETUP. HAVE INCREASED POPS TO LIKELY IN THE FAVORED NORTHERLY FLOW AREAS...IN ADDITION TO THE SE U.P. SINCE THE WINDS ARE PROGGED TO BE STRONG ENOUGH TO DRIVE ENHANCED BANDS INLAND. PCPN SHOULD BE IN THE FORM OF SNOW...THOUGH POSSIBLY MIXED WITH RAIN IN THE EVENING NEAR LAKE SUPERIOR UNTIL ENOUGH COOLING CAN TAKE PLACE TO SWITCH IT ALL TO SNOW. GREATEST AMOUNT OF PCPN EXPECTED IN UPSLOPE AREAS OF THE NORTH CENTRAL U.P....BUT LOW SNOW TO WATER RATIOS (10 TO 1 OR POSSIBLY EVEN LESS) SUGGESTS ONLY AN INCH OR TWO OF ACCUMULATION. PCPN SHOULD DIMINISH WEST TO EAST SOMEWHAT THROUGH THE DAY ON TUE...ENOUGH THAT POPS REMAIN IN THE CHANCE CATEGORY... THOUGH STILL HIGH IN THE UPSLOPE AREAS OF MQT/ALGER COUNTIES. SOUNDINGS SUGGEST THAT THE -10C ISOTHERM MAY DRY OUT ENOUGH... PARTICULARLY FROM THE NAM...THAT THE SNOW COULD CHANGE TO DZ IN THE AFTN. DAY SHIFT WILL NEED TO LOOK AT THIS AGAIN TO SEE IF MODELS TREND TOWARDS THIS IDEA. TEMPERATURE WISE...READINGS SHOULD NOT GET TOO CHILLY MON NIGHT THANKS TO CLOUDS AND WIND. MOST LOCATIONS SHOULD FALL INTO THE 20S...AND THOSE NEAR LAKE SUPERIOR MAY ONLY BOTTOM OUT AT 30. THE CLIMB ON TUE EXPECTED AGAIN OF 5 TO 10 DEGREES...WARMEST SOUTH CENTRAL WITH DOWNSLOPING. TUE NIGHT INTO WED...MAIN CONCERN FOR THIS PERIOD IS FZDZ. UPPER TROUGH/LOW REMAIN GENERALLY IN PLACE OVER NEW YORK STATE OR JUST MOVING SLIGHTLY NORTH INTO EASTERN ONTARIO DURING THIS PERIOD. RH PROFILES SHOW CONTINUED DRY ADVECTION ALOFT AND LOWERING INVERSIONS...WHICH RESULTS IN TRAPPED LOW LEVEL MOISTURE DURING THIS PERIOD. AT THE SFC...THE AREA IS STUCK BETWEEN A RIDGE BUILDING IN FROM MN AND A LOW IN EASTERN ONTARIO ASSOCIATED WITH THE UPPER LOW...RESULTING IN CONTINUED NORTH TO NW WINDS OVER THE CWA. WITH THE LOW CLOUDS AND THE WIND DIRECTION...ALONG WITH THE FACT THAT 900MB TEMPS AROUND -8C ARE FAVORABLE FOR LAKE ENHANCEMENT...SOME LIGHT PCPN IS POSSIBLE...ESPECIALLY IN UPSLOPE AREAS. SOUNDINGS SUGGEST THAT THE -10C ISOTHERM WILL DRY OUT...WHICH MEANS EITHER FZDZ OR -SHSN ARE POSSIBLE. HAVE INCLUDED THE FZDZ NOW ONLY IN UPSLOPE AREAS WHERE THE GREATER PROBABILITY OF IT OCCURRING EXISTS. FUTURE SHIFTS WILL NEED TO SEE IF FZDZ IS NEEDED ELSEWHERE. THE CHANCES FOR -SHSN/FZDZ ARE CONFINED TO TUE NIGHT THROUGH WED MORNING. AFTER WED MORNING...IT APPEARS THERE SHOULD BE ENOUGH DRYING BOTH BELOW THE CLOUDS AND ALOFT TO END THE NEED FOR CHANCE POPS. WILL NEED TO WATCH THE UPPER TROUGH/LOW...WITH SUGGESTIONS BY THE ECMWF OF IT ROTATING BACK FARTHER WEST FOR THE NEED TO INCLUDE POPS FOR THE EASTERN CWA. TEMPS TUE NIGHT EXPECTED TO BE A FEW DEGREES COOLER THAN MON NIGHT...COLDEST IN FAR WRN UPPER MI CLOSER TO THE SFC RIDGE. HIGHS ON WED SHOULD BE CLOSE TO NORMAL. BEYOND WED...NO CHANGES MADE. LOOKS LIKE IN THE MEAN FROM THE 00Z ECMWF/GFS/GFS ENSEMBLES THAT THE CWA WILL REMAIN IN UPPER TROUGH THROUGH THE NEXT 7 TO 10 DAYS. OVER TIME...THE TROUGHING GETS COOLER...BUT REALLY NOTHING TOO COLD EVIDENT. && .AVIATION (FOR THE 06Z TAF ISSUANCE)... EXPECT VFR CONDITIONS OVERNIGHT AT BOTH SITES AS DRY AIRMASS LINGERS EVEN AS THE SFC RIDGE SLIDES TO THE EAST. WITH THE RIDGE SHIFTING TO THE E AND THE LOW LEVEL WINDS SHIFTING FROM THE S TO THE WSW LATE IN THE NIGHT AND SUNDAY...EXPECT STRATOCU OVER THE NRN PLAINS/MN TO GRADUALLY OVERSPREAD THE UPPER GREAT LAKES. THE CLOUD BASE WILL INITIALLY BE VFR BUT SHOULD GRADUALLY TREND TOWARD MVFR IN THE MORNING WITH THE ARRIVAL OF GREATER MOISTURE BELOW THE SUBSIDENCE INVERSION. LIGHT SNOW THAY MAY REDUCE VSBY IS EXPECTED TO ARRIVE AFTER 06Z/MON AT KCMX. && .MARINE (FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)... WITH LOW PRES DROPPING SE TOWARD THE UPPER LAKES TODAY...EXPECT SWRLY WINDS ACROSS LAKE SUPERIOR IN THE 15-25KT RANGE WITH GUSTS TO 30KT. AS THE LOW SETTLES SE TOWARD THE LOWER LAKES...REORGANIZES AND STRENGTHENS SOME...EXPECT NRLY WINDS IN THE 15-30KT RANGE LATE MON AFTN THRU TUE WITH THE STRONGEST WINDS OVER THE E HALF OF THE LAKE. IT`S NOT OUT OF THE QUESTION THAT SOME GALE FORCE GUSTS COULD OCCUR...BUT SINCE COLD AIR ADVECTION IS WEAK...WILL HOLD OFF ON A MENTION OF GALES AT THIS TIME. WINDS WILL VERY SLOWLY DIMINISH WED/THU AS PROGRESSION OF SYSTEMS SLOWS TO A CRAWL. STRONGEST WINDS WILL REMAIN OVER ERN LAKE SUPERIOR WED/THU. && .MQT WATCHES/WARNINGS/ADVISORIES... UPPER MICHIGAN...NONE. LAKE SUPERIOR...NONE. LAKE MICHIGAN...NONE. && $$ SYNOPSIS/DISCUSSION...AJ AVIATION...JLB MARINE...ROLFSON mi AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE MARQUETTE MI 1226 AM EST SAT NOV 22 2008 UPDATED FOR 06Z AVIATION DISCUSSION .SYNOPSIS... ISSUED AT 347 PM EST 12Z ROABS/LATEST WV IMAGERY AND RUC ANALYSIS SHOW FULL LATITUDE TROF IN ERN NAMERICA EDGING SLOWLY EWD AND GIVING WAY TO UPR RDG SPREADING E FM THE PLAINS. SFC HI PRES CENTERS NOTED OVER ONTARIO AND THE OH VALLEY WITH HINT OF A LO PRES TROF OVER SRN LK SUP...MOST LIKELY DUE TO HEATING OF/PRES FALLS WITHIN THE CHILLY AIRMASS (12Z H85 TEMP AT APX WAS -15C) OVER THE RELATIVELY WARM LK SUP WATERS (4C OVER THE W TO 7C OVER THE E). ALTHOUGH SKIES HAVE CLEARED OVER MUCH OF THE W HALF OF THE FA (INCLUDING WRN LK SUP) WHERE DRY 12Z INL (PWAT 0.06 INCH)/GRB (PWAT 0.10 INCH) RAOBS AND 16Z TAMDAR SDNG FM RHI SHOW SUBSIDENCE INVRN AOB H9 AND DRY LOWER TROP...QUITE A BIT OF CLD LINGERS OVER NCNTRL AND ERN LK SUP AND THE E HALF OF THE FA/NRN LK MI AS INVRN BASE AT APX WAS STILL H825 AT 12Z. HOWEVER...LOWERING INVRN BASE W-E AND RELATIVELY DRY AIR SHOWN IN THE SUB INVRN LYR EVEN AT APX IN PRESENCE OF LARGER SCALE ACYC FLOW ASSOCIATED WITH ARRIVAL OF H85 RDG AXIS HAS ENDED ANY SGNFT LES EVEN WHERE QUITE A BIT OF SC LINGERS. THERE IS A SHRTWV DIGGING SEWD THRU IA...BUT THIS SYS IS PASSING FAR ENUF TO THE S THAT EVEN CI SHIELD IS SHIFTING BY S OF THE WI BORDER. QUITE A BIT OF LO CLD IS PRESENT OVER THE NRN PLAINS AND INTO WRN MN. 12Z BIS SDNG SHOWS QUITE A BIT OF LLVL MSTR BLO INVRN BASE AT H825. BUT SINCE AIRMASS IS DRY ABV H8 THERE...NO PCPN IS NOTED UNDER THE CLD COVER EVEN THOUGH THERE IS SOME FOG. THE TEMP OF THE MOIST LYR AT BIS WAS ENTIRELY ABV -10C. ANOTHER SHRTWV WAS NOTED OVER NRN MANITOBA AND DIGGING INTO NW ONTARIO E OF THE UPR RDG AXIS IN THE PLAINS. COVG OF DEEPER CLD COVER/PCPN ACCOMPANYING THIS FEATURE IS LIMITED BY DRYNESS SHOWN ON 12Z YQD/YPL RAOBS. FARTHER UPSTREAM...A POTENT SHRTWV IS SLAMMING EWD THRU SW CAN. 00Z- 12Z H3 HGT FALLS IN BRITISH COLUMBIA WERE 150-200M. && .SHORT TERM DISCUSSION... (TNGT THRU SUN) ISSUED AT 347 PM EST MAIN FCST CONCERNS IN THE SHORT TERM REVOLVE ARND LO PCPN CHCS ASSOCIATED WITH WAD PATTERN THAT WL BE DVLPG BTWN HI PRES RDG SHIFTING FARTHER E AND FALLING PRES TO THE W IN ADVANCE OF SHRTWV NOW MOVING THRU SW CAN. SHRTWV NOW DIGGING INTO NW ONTARIO IS ALSO OF SOME CONCERN. FOR TNGT...TWIN HI PRES OVER ONTARIO AND THE OH VALLEY ARE PROGGED TO CONSOLIDATE INTO ONE CENTER OVER THE SRN MID ATLANTIC STATES BY 12Z SUN WHILE SHRTWV NOW IN NW ONTARIO SLIDES TO JUST NE OF ANJ IN ADVANCE OF SHRTWV RDG PUSHING TOWARD WRN LK SUP AHEAD OF HGT/PRES FALLS OVER SCNTRL CAN. WITH LLVL FLOW VEERING FM S LATE TODAY TO THE WSW BY SUN MRNG...THE CLDS NOW OVER THE DAKOTAS/WRN MN ARE LIKELY TO ADVECT INTO THE UPR GRT LKS LATER TNGT AS INDICATED BY FCST RH SHOWN ON THE F18-24 GFS/NAM 280-285K ISENTROPIC SFCS (H9 THRU H775). HOWEVER...THE NAM/GFS/LOCAL WRF-ARW SHOW TENDENCY FOR HIER RH TO DIMINISH DESPITE INCRS IN SPECIFIC HUMIDITY SHOWN ON THE ISENTROPIC SFCS IN QUESTION. DRIER NATURE OF THE LLVLS SHOWN ON THE 12Z MPX SDNG THAT MAY BE THE SOURCE AIRMASS BEFORE FLOW VEERS MORE SUBSTANTIALLY AFT 12Z SUN LENDS SUPPORT TO THIS FCST. CONSIDERING THE RELUCTANCE OF ALL THESE MODELS TO INCRS THE LLVL RH AND DRYNESS OF ANTECEDENT AIRMASS...HAVE REMOVED GOING MENTION OF FZDZ TNGT. IN REGARDS TO SHRTWV DIGGING THRU NW ONTARIO...GUIDANCE SUGS TRACK OF THIS SYS WL BE FAR ENUF TO THE NE THAT ANY PCPN IN OVERALL DRY AIRMASS WL REMAIN NE OF THE FA ALTHOUGH SOME ACCOMPANYING HI CLD MAY IMPACT UPR MI. OTRW... SLOWLY INCRSG SW FLOW (H925 WINDS PROGGED TO INCRS TO ARND 25 KTS BY 12Z SUN) AND INCRSG ABSOLUTE MSTR WL LIMIT DIURNAL TEMP FALL SO THAT TNGT WL BE MUCH WARMER THAN LAST NGT (WHEN MIN TEMP REACHED -16F AT MARENISCO IN GOGEBIC COUNTY). ON SUN...EXPECT VEERING LLVL FLOW TO A MORE 250 DIRECTION TO ADVECT ENUF LLVL MSTR MORE FM THE BIS SOURCE AREA TO BRING IN A SC OVC EXCEPT OVER THE SCNTRL. ALSO MAINTAINED MENTION OF PTCHY -FZDZ IN THE MRNG OVER THE W HALF THAT WOULD UPSLOPE WITH EXPECTED WSW WIND. DIURNAL WRMG WL DCRS NEAR SFC RH ENUF IN THE AFTN TO LIMIT POTENTIAL FOR SML DROPLETS TO REACH SFC. -FZDZ SEEMS THE MOST LIKELY PCPN TYPE GIVEN TEMPS NO LOWER THAN ABOUT -6C WITHIN SHALLOW MOIST LYR. OTRW...WL MAINTAIN LO CHC POPS OVER MAINLY LK SUP ESPECIALLY IN THE AFTN WITH APRCH OF LO PRES TROF ATTENDANT TO SFC LO MOVING THRU SCNTRL CAN. BUT LIMITED MSTR DEPTH IN ABSENCE OF DEEP DYNAMIC SUPPORT WL LIMIT INTENSITY/COVG OF ANY PCPN. GIVEN HI STABILITY SHOWN ON FCST SDNGS...TENDED TOWARD THE LOWER GFS MOS GUIDANCE FOR SUN MAX TEMPS. COORDINATED WITH GRB. .LONG TERM DISCUSSION...(SUN NIGHT THRU THURS) LOW PRESSURE DROPPING SOUTHEAST FROM NORTHERN MANITOBA WILL BRING SOME LIGHT SNOW SHOWERS TO THE FA STARTING LATE SUNDAY NIGHT. BEST MOISTURE THOUGH REMAINS SOUTH AND EAST OF THE FA...TIED TO A LEE TROUGH THAT LATER BECOMES ABSORBED BY THE MANITOBA LOW. WILL NEED TO KEEP AN EYE ON THIS THOUGH AS LATEST GFS GUIDANCE HAS SHIFTED OVERALL MOISTURE FIELDS FURTHER NORTH AND WEST WHICH WOULD BE MORE IN LINE WITH THE 12Z/00Z ECMWF. CURRENT FCST HAS HIGH END CHANCE POPS OVER SOUTHEASTERN CWA WITH SLIGHTLY LOWER POPS ACROSS THE CENTRAL ZONES. AS THIS SYNOPTIC SNOW IS GOING ON...LIGHT LAKE EFFECT SNOW SHOWERS WILL BEGIN FOR NORTHWEST LAKE SUPERIOR LES BELTS ACROSS THE WEST AS THE LOW SHIFTS TO LAKE ERIE MONDAY AFTERNOON. AS WINDS TURN NORTH...SHIFTED HIGHEST POPS OVER NORTH CENTRAL UPPER MICHIGAN AND INTO WESTERN GOGEBIC COUNTY. OVERALL AIRMASS BEHIND THE LOW ISN/T VERY COLD...THOUGH QUITE SUFFICIENT FOR LES PROCESSES TO BEGIN...850MB TEMPS -10C/LS TEMPS AOB 8C. INVERSION HEIGHTS ARE PROGGED TO BE POOR AS WELL...AOB 3KFT...WHICH ALONG WITH SHALLOW MOISTURE APPEARS TO BE WHY WE WON/T BE SEEING MUCH SNOW THIS WEEK. AS THE LOW MOVES INTO THE NORTHEASTERN STATES TUESDAY MORNING...IT SLOWS AND BECOMES NEARLY STATIONARY THROUGH THURSDAY. AS A RESULT...LINGERED LES INTO EARLY WEDNESDAY MORNING. FUTURE SHIFTS MAY NEED TO LINGER LES LONGER ACROSS EASTERN ZONES...THOUGH RIGHT NOW IT LOOKS LIKE THIS NORTHERLY FLOW WILL JUST TRANSLATE INTO STRATUS. A BRIEF INFLUX OF MOISTURE ON THURSDAY MORNING ACROSS THE WESTERN ZONES...AS SEEN ON THE 295K SFC...MAY WARRANT THE ADDITION OF SOME LES POPS...KEPT FCST DRY FOR NOW THOUGH. && .AVIATION (FOR THE 06Z TAF ISSUANCE)... EXPECT VFR CONDITIONS OVERNIGHT AT BOTH SITES AS DRY AIRMASS LINGERS EVEN AS THE SFC RIDGE SLIDES TO THE EAST. WITH THE RIDGE SHIFTING TO THE E AND THE LOW LEVEL WINDS SHIFTING FROM THE S TO THE WSW LATE IN THE NIGHT AND SUNDAY...EXPECT STRATOCU OVER THE NRN PLAINS/MN TO GRADUALLY OVERSPREAD THE UPPER GREAT LAKES. THE CLOUD BASE WILL INITIALLY BE VFR BUT SHOULD GRADUALLY TREND TOWARD MVFR IN THE MORNING WITH THE ARRIVAL OF GREATER MOISTURE BELOW THE SUBSIDENCE INVERSION. LIGHT SNOW THAY MAY REDUCE VSBY IS EXPECTED TO ARRIVE AFTER 06Z/MON AT KCMX. && .MARINE (FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)... LOOK FOR A HIGH PRESSURE RIDGE OVER THE GREAT LAKES TODAY TO MOVE EASTWARD AND WEAKEN THROUGH SUNDAY. FOLLOWING CLOSE BEHIND...A LOW WILL MOVE INTO THE UPPER GREAT LAKES FROM NORTHERN MANITOBA AND PRESS INTO THE EASTERN GREAT LAKES BY EARLY TUESDAY. NORTH WINDS IN THE WAKE OF THIS LOW MAY REACH 30 KNOTS. EXPECT THE LOW TO THEN SLOWLY SHIFT NORTHEAST...REACHING THE EAST END OF LAKE ONTARIO BY LATE WEDNESDAY. ALSO ON WEDNESDAY...A HIGH PRESSURE RIDGE FROM THE PLAINS WILL BUILD INTO WESTERN LAKE SUPERIOR. NO GALE FORCE WINDS ARE LIKELY THROUGH THURSDAY. && .MQT WATCHES/WARNINGS/ADVISORIES... UPPER MICHIGAN...NONE. LAKE SUPERIOR...NONE. LAKE MICHIGAN...NONE. && $$ SYNOPSIS/SHORT TERM...KC LONG TERM...PEARSON AVIATION...JLB MARINE...KC mi AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE MARQUETTE MI 635 PM EST SAT NOV 22 2008 UPDATED FOR 00Z AVIATION DISCUSSION .SYNOPSIS... 12Z ROABS/LATEST WV IMAGERY AND RUC ANALYSIS SHOW FULL LATITUDE TROF IN ERN NAMERICA EDGING SLOWLY EWD AND GIVING WAY TO UPR RDG SPREADING E FM THE PLAINS. SFC HI PRES CENTERS NOTED OVER ONTARIO AND THE OH VALLEY WITH HINT OF A LO PRES TROF OVER SRN LK SUP...MOST LIKELY DUE TO HEATING OF/PRES FALLS WITHIN THE CHILLY AIRMASS (12Z H85 TEMP AT APX WAS -15C) OVER THE RELATIVELY WARM LK SUP WATERS (4C OVER THE W TO 7C OVER THE E). ALTHOUGH SKIES HAVE CLEARED OVER MUCH OF THE W HALF OF THE FA (INCLUDING WRN LK SUP) WHERE DRY 12Z INL (PWAT 0.06 INCH)/GRB (PWAT 0.10 INCH) RAOBS AND 16Z TAMDAR SDNG FM RHI SHOW SUBSIDENCE INVRN AOB H9 AND DRY LOWER TROP...QUITE A BIT OF CLD LINGERS OVER NCNTRL AND ERN LK SUP AND THE E HALF OF THE FA/NRN LK MI AS INVRN BASE AT APX WAS STILL H825 AT 12Z. HOWEVER...LOWERING INVRN BASE W-E AND RELATIVELY DRY AIR SHOWN IN THE SUB INVRN LYR EVEN AT APX IN PRESENCE OF LARGER SCALE ACYC FLOW ASSOCIATED WITH ARRIVAL OF H85 RDG AXIS HAS ENDED ANY SGNFT LES EVEN WHERE QUITE A BIT OF SC LINGERS. THERE IS A SHRTWV DIGGING SEWD THRU IA...BUT THIS SYS IS PASSING FAR ENUF TO THE S THAT EVEN CI SHIELD IS SHIFTING BY S OF THE WI BORDER. QUITE A BIT OF LO CLD IS PRESENT OVER THE NRN PLAINS AND INTO WRN MN. 12Z BIS SDNG SHOWS QUITE A BIT OF LLVL MSTR BLO INVRN BASE AT H825. BUT SINCE AIRMASS IS DRY ABV H8 THERE...NO PCPN IS NOTED UNDER THE CLD COVER EVEN THOUGH THERE IS SOME FOG. THE TEMP OF THE MOIST LYR AT BIS WAS ENTIRELY ABV -10C. ANOTHER SHRTWV WAS NOTED OVER NRN MANITOBA AND DIGGING INTO NW ONTARIO E OF THE UPR RDG AXIS IN THE PLAINS. COVG OF DEEPER CLD COVER/PCPN ACCOMPANYING THIS FEATURE IS LIMITED BY DRYNESS SHOWN ON 12Z YQD/YPL RAOBS. FARTHER UPSTREAM...A POTENT SHRTWV IS SLAMMING EWD THRU SW CAN. 00Z- 12Z H3 HGT FALLS IN BRITISH COLUMBIA WERE 150-200M. && .SHORT TERM DISCUSSION... (TNGT THRU SUN) MAIN FCST CONCERNS IN THE SHORT TERM REVOLVE ARND LO PCPN CHCS ASSOCIATED WITH WAD PATTERN THAT WL BE DVLPG BTWN HI PRES RDG SHIFTING FARTHER E AND FALLING PRES TO THE W IN ADVANCE OF SHRTWV NOW MOVING THRU SW CAN. SHRTWV NOW DIGGING INTO NW ONTARIO IS ALSO OF SOME CONCERN. FOR TNGT...TWIN HI PRES OVER ONTARIO AND THE OH VALLEY ARE PROGGED TO CONSOLIDATE INTO ONE CENTER OVER THE SRN MID ATLANTIC STATES BY 12Z SUN WHILE SHRTWV NOW IN NW ONTARIO SLIDES TO JUST NE OF ANJ IN ADVANCE OF SHRTWV RDG PUSHING TOWARD WRN LK SUP AHEAD OF HGT/PRES FALLS OVER SCNTRL CAN. WITH LLVL FLOW VEERING FM S LATE TODAY TO THE WSW BY SUN MRNG...THE CLDS NOW OVER THE DAKOTAS/WRN MN ARE LIKELY TO ADVECT INTO THE UPR GRT LKS LATER TNGT AS INDICATED BY FCST RH SHOWN ON THE F18-24 GFS/NAM 280-285K ISENTROPIC SFCS (H9 THRU H775). HOWEVER...THE NAM/GFS/LOCAL WRF-ARW SHOW TENDENCY FOR HIER RH TO DIMINISH DESPITE INCRS IN SPECIFIC HUMIDITY SHOWN ON THE ISENTROPIC SFCS IN QUESTION. DRIER NATURE OF THE LLVLS SHOWN ON THE 12Z MPX SDNG THAT MAY BE THE SOURCE AIRMASS BEFORE FLOW VEERS MORE SUBSTANTIALLY AFT 12Z SUN LENDS SUPPORT TO THIS FCST. CONSIDERING THE RELUCTANCE OF ALL THESE MODELS TO INCRS THE LLVL RH AND DRYNESS OF ANTECEDENT AIRMASS...HAVE REMOVED GOING MENTION OF FZDZ TNGT. IN REGARDS TO SHRTWV DIGGING THRU NW ONTARIO...GUIDANCE SUGS TRACK OF THIS SYS WL BE FAR ENUF TO THE NE THAT ANY PCPN IN OVERALL DRY AIRMASS WL REMAIN NE OF THE FA ALTHOUGH SOME ACCOMPANYING HI CLD MAY IMPACT UPR MI. OTRW... SLOWLY INCRSG SW FLOW (H925 WINDS PROGGED TO INCRS TO ARND 25 KTS BY 12Z SUN) AND INCRSG ABSOLUTE MSTR WL LIMIT DIURNAL TEMP FALL SO THAT TNGT WL BE MUCH WARMER THAN LAST NGT (WHEN MIN TEMP REACHED -16F AT MARENISCO IN GOGEBIC COUNTY). ON SUN...EXPECT VEERING LLVL FLOW TO A MORE 250 DIRECTION TO ADVECT ENUF LLVL MSTR MORE FM THE BIS SOURCE AREA TO BRING IN A SC OVC EXCEPT OVER THE SCNTRL. ALSO MAINTAINED MENTION OF PTCHY -FZDZ IN THE MRNG OVER THE W HALF THAT WOULD UPSLOPE WITH EXPECTED WSW WIND. DIURNAL WRMG WL DCRS NEAR SFC RH ENUF IN THE AFTN TO LIMIT POTENTIAL FOR SML DROPLETS TO REACH SFC. -FZDZ SEEMS THE MOST LIKELY PCPN TYPE GIVEN TEMPS NO LOWER THAN ABOUT -6C WITHIN SHALLOW MOIST LYR. OTRW...WL MAINTAIN LO CHC POPS OVER MAINLY LK SUP ESPECIALLY IN THE AFTN WITH APRCH OF LO PRES TROF ATTENDANT TO SFC LO MOVING THRU SCNTRL CAN. BUT LIMITED MSTR DEPTH IN ABSENCE OF DEEP DYNAMIC SUPPORT WL LIMIT INTENSITY/COVG OF ANY PCPN. GIVEN HI STABILITY SHOWN ON FCST SDNGS...TENDED TOWARD THE LOWER GFS MOS GUIDANCE FOR SUN MAX TEMPS. COORDINATED WITH GRB. .LONG TERM DISCUSSION...(SUN NIGHT THRU THURS) LOW PRESSURE DROPPING SOUTHEAST FROM NORTHERN MANITOBA WILL BRING SOME LIGHT SNOW SHOWERS TO THE FA STARTING LATE SUNDAY NIGHT. BEST MOISTURE THOUGH REMAINS SOUTH AND EAST OF THE FA...TIED TO A LEE TROUGH THAT LATER BECOMES ABSORBED BY THE MANITOBA LOW. WILL NEED TO KEEP AN EYE ON THIS THOUGH AS LATEST GFS GUIDANCE HAS SHIFTED OVERALL MOISTURE FIELDS FURTHER NORTH AND WEST WHICH WOULD BE MORE IN LINE WITH THE 12Z/00Z ECMWF. CURRENT FCST HAS HIGH END CHANCE POPS OVER SOUTHEASTERN CWA WITH SLIGHTLY LOWER POPS ACROSS THE CENTRAL ZONES. AS THIS SYNOPTIC SNOW IS GOING ON...LIGHT LAKE EFFECT SNOW SHOWERS WILL BEGIN FOR NORTHWEST LAKE SUPERIOR LES BELTS ACROSS THE WEST AS THE LOW SHIFTS TO LAKE ERIE MONDAY AFTERNOON. AS WINDS TURN NORTH...SHIFTED HIGHEST POPS OVER NORTH CENTRAL UPPER MICHIGAN AND INTO WESTERN GOGEBIC COUNTY. OVERALL AIRMASS BEHIND THE LOW ISN/T VERY COLD...THOUGH QUITE SUFFICIENT FOR LES PROCESSES TO BEGIN...850MB TEMPS -10C/LS TEMPS AOB 8C. INVERSION HEIGHTS ARE PROGGED TO BE POOR AS WELL...AOB 3KFT...WHICH ALONG WITH SHALLOW MOISTURE APPEARS TO BE WHY WE WON/T BE SEEING MUCH SNOW THIS WEEK. AS THE LOW MOVES INTO THE NORTHEASTERN STATES TUESDAY MORNING...IT SLOWS AND BECOMES NEARLY STATIONARY THROUGH THURSDAY. AS A RESULT...LINGERED LES INTO EARLY WEDNESDAY MORNING. FUTURE SHIFTS MAY NEED TO LINGER LES LONGER ACROSS EASTERN ZONES...THOUGH RIGHT NOW IT LOOKS LIKE THIS NORTHERLY FLOW WILL JUST TRANSLATE INTO STRATUS. A BRIEF INFLUX OF MOISTURE ON THURSDAY MORNING ACROSS THE WESTERN ZONES...AS SEEN ON THE 295K SFC...MAY WARRANT THE ADDITION OF SOME LES POPS...KEPT FCST DRY FOR NOW THOUGH. && .AVIATION (FOR THE 00Z TAF ISSUANCE)... EXPECT VFR CONDITIONS TONIGHT AT BOTH SITES WITH SFC RDG AND DRY AIRMASS DOMINATING THE REGION. AS THE RIDGE SHIFTS TO THE E AND THE LOW LEVEL WINDS SHIFT FROM THE S TO THE WSW LATE TONIGHT AND SUNDAY...EXPECT SC OVER THE NRN PLAINS/MN TO GRADUALLY OVERSPREAD THE UPPER GREAT LAKES. THE CLOUD BASE WILL INITIALLY BE VFR BUT SHOULD GRADUALLY TREND TOWARD MVFR SUN MORNING WITH THE ARRIVAL OF GREATER MOISTURE BELOW THE SUBSIDENCE INVERSION. && .MARINE (FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)... LOOK FOR A HIGH PRESSURE RIDGE OVER THE GREAT LAKES TODAY TO MOVE EASTWARD AND WEAKEN THROUGH SUNDAY. FOLLOWING CLOSE BEHIND...A LOW WILL MOVE INTO THE UPPER GREAT LAKES FROM NORTHERN MANITOBA AND PRESS INTO THE EASTERN GREAT LAKES BY EARLY TUESDAY. NORTH WINDS IN THE WAKE OF THIS LOW MAY REACH 30 KNOTS. EXPECT THE LOW TO THEN SLOWLY SHIFT NORTHEAST...REACHING THE EAST END OF LAKE ONTARIO BY LATE WEDNESDAY. ALSO ON WEDNESDAY...A HIGH PRESSURE RIDGE FROM THE PLAINS WILL BUILD INTO WESTERN LAKE SUPERIOR. NO GALE FORCE WINDS ARE LIKELY THROUGH THURSDAY. && .MQT WATCHES/WARNINGS/ADVISORIES... UPPER MICHIGAN...NONE. LAKE SUPERIOR...NONE. LAKE MICHIGAN...NONE. && $$ SYNOPSIS/SHORT TERM...KC LONG TERM...PEARSON AVIATION...KC MARINE...KC mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MARQUETTE MI 347 PM EST SAT NOV 22 2008 .SYNOPSIS... 12Z ROABS/LATEST WV IMAGERY AND RUC ANALYSIS SHOW FULL LATITUDE TROF IN ERN NAMERICA EDGING SLOWLY EWD AND GIVING WAY TO UPR RDG SPREADING E FM THE PLAINS. SFC HI PRES CENTERS NOTED OVER ONTARIO AND THE OH VALLEY WITH HINT OF A LO PRES TROF OVER SRN LK SUP...MOST LIKELY DUE TO HEATING OF/PRES FALLS WITHIN THE CHILLY AIRMASS (12Z H85 TEMP AT APX WAS -15C) OVER THE RELATIVELY WARM LK SUP WATERS (4C OVER THE W TO 7C OVER THE E). ALTHOUGH SKIES HAVE CLEARED OVER MUCH OF THE W HALF OF THE FA (INCLUDING WRN LK SUP) WHERE DRY 12Z INL (PWAT 0.06 INCH)/GRB (PWAT 0.10 INCH) RAOBS AND 16Z TAMDAR SDNG FM RHI SHOW SUBSIDENCE INVRN AOB H9 AND DRY LOWER TROP...QUITE A BIT OF CLD LINGERS OVER NCNTRL AND ERN LK SUP AND THE E HALF OF THE FA/NRN LK MI AS INVRN BASE AT APX WAS STILL H825 AT 12Z. HOWEVER...LOWERING INVRN BASE W-E AND RELATIVELY DRY AIR SHOWN IN THE SUB INVRN LYR EVEN AT APX IN PRESENCE OF LARGER SCALE ACYC FLOW ASSOCIATED WITH ARRIVAL OF H85 RDG AXIS HAS ENDED ANY SGNFT LES EVEN WHERE QUITE A BIT OF SC LINGERS. THERE IS A SHRTWV DIGGING SEWD THRU IA...BUT THIS SYS IS PASSING FAR ENUF TO THE S THAT EVEN CI SHIELD IS SHIFTING BY S OF THE WI BORDER. QUITE A BIT OF LO CLD IS PRESENT OVER THE NRN PLAINS AND INTO WRN MN. 12Z BIS SDNG SHOWS QUITE A BIT OF LLVL MSTR BLO INVRN BASE AT H825. BUT SINCE AIRMASS IS DRY ABV H8 THERE...NO PCPN IS NOTED UNDER THE CLD COVER EVEN THOUGH THERE IS SOME FOG. THE TEMP OF THE MOIST LYR AT BIS WAS ENTIRELY ABV -10C. ANOTHER SHRTWV WAS NOTED OVER NRN MANITOBA AND DIGGING INTO NW ONTARIO E OF THE UPR RDG AXIS IN THE PLAINS. COVG OF DEEPER CLD COVER/PCPN ACCOMPANYING THIS FEATURE IS LIMITED BY DRYNESS SHOWN ON 12Z YQD/YPL RAOBS. FARTHER UPSTREAM...A POTENT SHRTWV IS SLAMMING EWD THRU SW CAN. 00Z- 12Z H3 HGT FALLS IN BRITISH COLUMBIA WERE 150-200M. && .SHORT TERM DISCUSSION... (TNGT THRU SUN) MAIN FCST CONCERNS IN THE SHORT TERM REVOLVE ARND LO PCPN CHCS ASSOCIATED WITH WAD PATTERN THAT WL BE DVLPG BTWN HI PRES RDG SHIFTING FARTHER E AND FALLING PRES TO THE W IN ADVANCE OF SHRTWV NOW MOVING THRU SW CAN. SHRTWV NOW DIGGING INTO NW ONTARIO IS ALSO OF SOME CONCERN. FOR TNGT...TWIN HI PRES OVER ONTARIO AND THE OH VALLEY ARE PROGGED TO CONSOLIDATE INTO ONE CENTER OVER THE SRN MID ATLANTIC STATES BY 12Z SUN WHILE SHRTWV NOW IN NW ONTARIO SLIDES TO JUST NE OF ANJ IN ADVANCE OF SHRTWV RDG PUSHING TOWARD WRN LK SUP AHEAD OF HGT/PRES FALLS OVER SCNTRL CAN. WITH LLVL FLOW VEERING FM S LATE TODAY TO THE WSW BY SUN MRNG...THE CLDS NOW OVER THE DAKOTAS/WRN MN ARE LIKELY TO ADVECT INTO THE UPR GRT LKS LATER TNGT AS INDICATED BY FCST RH SHOWN ON THE F18-24 GFS/NAM 280-285K ISENTROPIC SFCS (H9 THRU H775). HOWEVER...THE NAM/GFS/LOCAL WRF-ARW SHOW TENDENCY FOR HIER RH TO DIMINISH DESPITE INCRS IN SPECIFIC HUMIDITY SHOWN ON THE ISENTROPIC SFCS IN QUESTION. DRIER NATURE OF THE LLVLS SHOWN ON THE 12Z MPX SDNG THAT MAY BE THE SOURCE AIRMASS BEFORE FLOW VEERS MORE SUBSTANTIALLY AFT 12Z SUN LENDS SUPPORT TO THIS FCST. CONSIDERING THE RELUCTANCE OF ALL THESE MODELS TO INCRS THE LLVL RH AND DRYNESS OF ANTECEDENT AIRMASS...HAVE REMOVED GOING MENTION OF FZDZ TNGT. IN REGARDS TO SHRTWV DIGGING THRU NW ONTARIO...GUIDANCE SUGS TRACK OF THIS SYS WL BE FAR ENUF TO THE NE THAT ANY PCPN IN OVERALL DRY AIRMASS WL REMAIN NE OF THE FA ALTHOUGH SOME ACCOMPANYING HI CLD MAY IMPACT UPR MI. OTRW... SLOWLY INCRSG SW FLOW (H925 WINDS PROGGED TO INCRS TO ARND 25 KTS BY 12Z SUN) AND INCRSG ABSOLUTE MSTR WL LIMIT DIURNAL TEMP FALL SO THAT TNGT WL BE MUCH WARMER THAN LAST NGT (WHEN MIN TEMP REACHED -16F AT MARENISCO IN GOGEBIC COUNTY). ON SUN...EXPECT VEERING LLVL FLOW TO A MORE 250 DIRECTION TO ADVECT ENUF LLVL MSTR MORE FM THE BIS SOURCE AREA TO BRING IN A SC OVC EXCEPT OVER THE SCNTRL. ALSO MAINTAINED MENTION OF PTCHY -FZDZ IN THE MRNG OVER THE W HALF THAT WOULD UPSLOPE WITH EXPECTED WSW WIND. DIURNAL WRMG WL DCRS NEAR SFC RH ENUF IN THE AFTN TO LIMIT POTENTIAL FOR SML DROPLETS TO REACH SFC. -FZDZ SEEMS THE MOST LIKELY PCPN TYPE GIVEN TEMPS NO LOWER THAN ABOUT -6C WITHIN SHALLOW MOIST LYR. OTRW...WL MAINTAIN LO CHC POPS OVER MAINLY LK SUP ESPECIALLY IN THE AFTN WITH APRCH OF LO PRES TROF ATTENDANT TO SFC LO MOVING THRU SCNTRL CAN. BUT LIMITED MSTR DEPTH IN ABSENCE OF DEEP DYNAMIC SUPPORT WL LIMIT INTENSITY/COVG OF ANY PCPN. GIVEN HI STABILITY SHOWN ON FCST SDNGS...TENDED TOWARD THE LOWER GFS MOS GUIDANCE FOR SUN MAX TEMPS. COORDINATED WITH GRB. .LONG TERM DISCUSSION...(SUN NIGHT THRU THURS) LOW PRESSURE DROPPING SOUTHEAST FROM NORTHERN MANITOBA WILL BRING SOME LIGHT SNOW SHOWERS TO THE FA STARTING LATE SUNDAY NIGHT. BEST MOISTURE THOUGH REMAINS SOUTH AND EAST OF THE FA...TIED TO A LEE TROUGH THAT LATER BECOMES ABSORBED BY THE MANITOBA LOW. WILL NEED TO KEEP AN EYE ON THIS THOUGH AS LATEST GFS GUIDANCE HAS SHIFTED OVERALL MOISTURE FIELDS FURTHER NORTH AND WEST WHICH WOULD BE MORE IN LINE WITH THE 12Z/00Z ECMWF. CURRENT FCST HAS HIGH END CHANCE POPS OVER SOUTHEASTERN CWA WITH SLIGHTLY LOWER POPS ACROSS THE CENTRAL ZONES. AS THIS SYNOPTIC SNOW IS GOING ON...LIGHT LAKE EFFECT SNOW SHOWERS WILL BEGIN FOR NORTHWEST LAKE SUPERIOR LES BELTS ACROSS THE WEST AS THE LOW SHIFTS TO LAKE ERIE MONDAY AFTERNOON. AS WINDS TURN NORTH...SHIFTED HIGHEST POPS OVER NORTH CENTRAL UPPER MICHIGAN AND INTO WESTERN GOGEBIC COUNTY. OVERALL AIRMASS BEHIND THE LOW ISN/T VERY COLD...THOUGH QUITE SUFFICIENT FOR LES PROCESSES TO BEGIN...850MB TEMPS -10C/LS TEMPS AOB 8C. INVERSION HEIGHTS ARE PROGGED TO BE POOR AS WELL...AOB 3KFT...WHICH ALONG WITH SHALLOW MOISTURE APPEARS TO BE WHY WE WON/T BE SEEING MUCH SNOW THIS WEEK. AS THE LOW MOVES INTO THE NORTHEASTERN STATES TUESDAY MORNING...IT SLOWS AND BECOMES NEARLY STATIONARY THROUGH THURSDAY. AS A RESULT...LINGERED LES INTO EARLY WEDNESDAY MORNING. FUTURE SHIFTS MAY NEED TO LINGER LES LONGER ACROSS EASTERN ZONES...THOUGH RIGHT NOW IT LOOKS LIKE THIS NORTHERLY FLOW WILL JUST TRANSLATE INTO STRATUS. A BRIEF INFLUX OF MOISTURE ON THURSDAY MORNING ACROSS THE WESTERN ZONES...AS SEEN ON THE 295K SFC...MAY WARRANT THE ADDITION OF SOME LES POPS...KEPT FCST DRY FOR NOW THOUGH. && .AVIATION (FOR THE 18Z TAF ISSUANCE)... EXPECT VFR CONDITIONS THIS AFTN/TNGT AT BOTH SITES WITH DRY AIRMASS SHOWN ON THE 12Z GRB RAOB/SFC HI PRES RDG DOMINATING. AS THE RDG SHIFTS TO THE E AND THE LLVL WINDS SHIFT FM THE S TO THE WSW LATE TNGT/SUN...EXPECT SC OVER THE NRN PLAINS/MN TO GRDLY OVERSPREAD THE UPR LKS. THE CLD BASE WL INITIALLY BE VFR GIVEN DRYNESS OF ANTECEDENT AIRMASS BUT GRDLY TREND TOWARD MVFR ON SUN MRNG WITH ARRIVAL OF GREATER MSTR BLO SUBSIDENCE INVRN. && .MARINE (FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)... LOOK FOR A HIGH PRESSURE RIDGE OVER THE GREAT LAKES TODAY TO MOVE EASTWARD AND WEAKEN THROUGH SUNDAY. FOLLOWING CLOSE BEHIND...A LOW WILL MOVE INTO THE UPPER GREAT LAKES FROM NORTHERN MANITOBA AND PRESS INTO THE EASTERN GREAT LAKES BY EARLY TUESDAY. NORTH WINDS IN THE WAKE OF THIS LOW MAY REACH 30 KNOTS. EXPECT THE LOW TO THEN SLOWLY SHIFT NORTHEAST...REACHING THE EAST END OF LAKE ONTARIO BY LATE WEDNESDAY. ALSO ON WEDNESDAY...A HIGH PRESSURE RIDGE FROM THE PLAINS WILL BUILD INTO WESTERN LAKE SUPERIOR. NO GALE FORCE WINDS ARE LIKELY THROUGH THURSDAY. && .MQT WATCHES/WARNINGS/ADVISORIES... UPPER MICHIGAN...NONE. LAKE SUPERIOR...NONE. LAKE MICHIGAN...NONE. && $$ SYNOPSIS/SHORT TERM...KC LONG TERM...PEARSON AVIATION...KC MARINE...KC mi AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE MARQUETTE MI 1225 PM EST SAT NOV 22 2008 UPDATED AVIATION DISCUSSION FOR 18Z TAF ISSUANCE .SYNOPSIS... (ISSUED AT 5 AM EST) WATER VAPOR IMAGERY AND RUC ANALYSIS SHOW A DEEP TROF EXTENDING S INTO NEW ENGLAND AND THE MID ATLANTIC STATES. RIDGE IS TO THE LEE OF THE ROCKIES AND EXTENDS WELL N TO THE NW TERRITORIES. A WELL-DEFINED SHORTWAVE HAS CUT THRU THE RIDGE AND IS NOW OVER ERN SD. IT`S ON A TRACK TO PASS S OF UPPER MI AND HAVE NO AFFECT ON THE WEATHER HERE. FARTHER UPSTREAM...TROF HAS MOVED ONSHORE IN WRN CANADA WITH STRONG SHORTWAVE IMPACTING WA/BRITISH COLUMBIA (12HR HEIGHT FALLS WERE UPWARDS OF 140M AT 500MB). THIS TROF WILL BE THE NEXT SYSTEM TO AFFECT THE AREA AS IT DROPS INTO THE GREAT LAKES SUN/MON. CLOSER TO HOME...LES CONTINUES OFF LAKE SUPERIOR...BUT HAS WEAKENED SIGNIFICANTLY IN THE LAST FEW HRS. STRENGTHENING LAND BREEZES ARE FOCUSING MAIN BANDS OF -SHSN INTO MAINLY ALGER COUNTY. OTHERWISE... -SHSN/FLURRIES LINGER FROM THE KEWEENAW TO ERN UPPER MI. OVER SW UPPER MI...SKIES CLEARED EARLIER IN THE NIGHT AND TEMPS HAVE NOSE-DIVED UNDER CLEAR SKIES/CALM WIND/FRESH SNOW COVER. AS OF 09Z...LOWEST TEMP IS -15F AT THE WAKEFIELD RAWS SITE. && .DISCUSSION... (ISSUED AT 5 AM EST) WITH SFC RIDGE AXIS ACROSS CNTRL LAKE SUPERIOR AND CNTRL UPPER MI DRIFTING E...ONGOING LES WILL SHIFT OFFSHORE BY MID MORNING UNDER DEVELOPING SRLY FLOW ENHANCED BY LAND BREEZE. OTHERWISE...AREAS THAT START THE DAY MOSTLY SUNNY SHOULD GENERALLY REMAIN THAT WAY WHILE AREAS WITH STRATOCU SHOULD TREND MOSTLY SUNNY BY AFTN. ONLY EXCEPTION WILL BE DOWNWIND OF LAKE MICHIGAN (SRN SCHOOLCRAFT/LUCE COUNTIES) WHERE DEVELOPING SRLY FLOW SHOULD BRING STRATOCU AND SOME FLURRIES DURING THE AFTN. THERE WILL BE SOME CI SPILLING DOWN THE FRONT SIDE OF MID/UPPER RIDGE TO THE W...BUT AT THE MOMENT IT DOES NOT APPEAR THAT THE CI WILL BE TOO THICK OR WIDESPREAD. FAVORED THE LOWER END OF MOS GUIDANCE FOR HIGH TEMPS BASED ON UPSTREAM HIGHS YESTERDAY. NAM/GFS ARE IN REASONABLE AGREEMENT ON DEVELOPING WAA PATTERN TONIGHT/SUN AHEAD OF TROF EMERGING TO THE LEE OF THE ROCKIES. WITH TIGHTER THERMAL GRADIENT TO THE N IN ONTARIO...BEST ISENTROPIC ASCENT THAT WOULD SUPPORT THE POTENTIAL OF MEASURABLE PCPN WILL REMAIN N OF THE FCST AREA AS WELL. INHERITED FCST HAD A MENTION OF -FZDZ LATE TONIGHT/SUN MORNING OVER ROUGHLY THE W HALF OF THE FCST AREA WITH EXCEPTION OF AREAS WHERE SWRLY FLOW DOWNSLOPES... MINIMIZING THREAT. NAM FCST SOUNDINGS STILL LEND SUPPORT TO THIS POSSIBILITY AS TEMPS WILL BE ABOVE -10C IN DEVELOPING LOW-LEVEL SATURATION...AND THERE WILL BE A PERIOD OF UPWARD MOTION STILL OCCURRING AFTER SATURATION IS ACHIEVED. LOCAL REG-WRF RUN PROVIDES SOME SUPPORT...BUT GFS IS LESS SUPPORTIVE OF THE POTENTIAL OF -FZDZ. AT THIS POINT...SEE NO REASON TO PULL THE MENTION OF PATCHY -FZDZ...BUT WILL PUSH BACK TIMING TO LATE TONIGHT DUE TO SLOWER ARRIVAL OF MOISTURE. ONLY OTHER MINOR ISSUE IS THE POSSIBILITY OF A LITTLE SW FLOW LAKE ENHANCED SNOW OVER WRN LAKE SUPERIOR AND NRN LAKE MICHIGAN AS 850MB TEMPS ARE SUFFICIENTLY LOW ENOUGH. OVER LAKE SUPERIOR...WINDS IN THE CLOUD LAYER MAY HAVE ENOUGH OF A WRLY COMPONENT THAT IF SHSN DEVELOP...THEY MAY BRUSH THE KEWEENAW LATE TONIGHT/SUN. WILL ONLY UTILIZE SLIGHT CHC POPS DUE TO UNCERTAINTY IN WIND DIRECTION...AND ALSO BECAUSE DEVELOPMENT MAY ONLY OCCUR N OF THE KEWEENAW WHERE FETCH IS MAXIMIZED. OVER NRN LAKE MICHIGAN...IT APPEARS BY THE TIME ANY DEVELOPMENT OCCURS...WINDS WILL HAVE ENOUGH OF A WRLY COMPONENT TO KEEP ANY -SHSN E OF SCHOOLCRAFT/LUCE COUNTIES. MINOR HEIGHT FALLS BEGIN SUN AFTN AS TROF EDGES E ACROSS THE PLAINS STATES AND SCNTRL CANADA. HOWEVER...HAVE A HARD TIME FINDING ANY FORCING SUFFICIENT TO WARRANT A MENTION OF PCPN. SO...WITH THE EXCEPTION OF THE KEWEENAW...EXPECT A DRY AFTN ACROSS THE FCST AREA. BETTER HEIGHT FALLS DEVELOP SUN NIGHT INTO MON AS TROF REACHES THE GREAT LAKES WITH MID LEVEL LOW SETTLING SE INTO THE UPPER LAKES BY MON EVENING. AS BROAD SFC LOW BEGINS TO ORGANIZE OVER THE UPPER LAKES...NWRLY FLOW AND CAA WILL BEGIN SUN NIGHT. GFS IS QUICKEST WITH THE COOLING...DROPPING 850MB TEMPS TO -9/-10C OVER THE W HALF OF LAKE SUPERIOR BY 12Z MON WHICH WOULD SUPPORT DEVELOPMENT OF LES. NAM IS CONSIDERABLY WARMER...ONLY AROUND -4C. UKMET/ECMWF/REG-WRF FALL BTWN THE NAM/GFS...BUT CLOSER TO THE GFS AND STILL MARGINALLY COLD ENOUGH FOR SOME LES. SO...WITH LIMITED FORCING...PCPN SUN NIGHT MAY BE TIED MOSTLY TO LAKE EFFECT. WILL CONTINUE WITH CHC POPS. PER ECMWF/GFS...AS NW FLOW BECOMES N WITH SFC LOW PRES CONSOLIDATING TOWARD THE LOWER LAKES...EXPECT -SHSN TO EXPAND ACROSS NRN UPPER MI MON. WITH LIMITED OVERLAKE INSTABILITY (850MB TEMPS AROUND -9C) AND WITH MUCH OF THE UPWARD MOTION OCCURRING BELOW THE DENDRITIC SNOW GROWTH TEMP ZONE...EXPECT MAINLY LIGHT ACCUMULATIONS OF SNOW. CONSOLIDATING LOW TO THE SE MAY ALSO SPREAD A GENERAL -SN INTO THE ERN FCST AREA MON. -SHSN WILL CONTINUE UNDER NRLY FLOW MON NIGHT THEN DIMINISH TUE. && .AVIATION (FOR THE 18Z TAF ISSUANCE)... EXPECT VFR CONDITIONS THIS AFTN/TNGT AT BOTH SITES WITH DRY AIRMASS SHOWN ON THE 12Z GRB RAOB/SFC HI PRES RDG DOMINATING. AS THE RDG SHIFTS TO THE E AND THE LLVL WINDS SHIFT FM THE S TO THE WSW LATE TNGT/SUN...EXPECT SC OVER THE NRN PLAINS/MN TO GRDLY OVERSPREAD THE UPR LKS. THE CLD BASE WL INITIALLY BE VFR GIVEN DRYNESS OF ANTECEDENT AIRMASS BUT GRDLY TREND TOWARD MVFR ON SUN MRNG WITH ARRIVAL OF GREATER MSTR BLO SUBSIDENCE INVRN. && .MARINE (FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)... A HIGH PRESSURE RIDGE CENTERED OVER THE WESTERN GREAT LAKES WILL MOVE EAST TODAY THROUGH SUNDAY AS AN AREA OF LOW PRESSURE SHIFTS ACROSS SOUTHERN CANADA. VARIABLE WINDS UNDER 25 KTS TODAY WILL BECOME SW TONIGHT AS THE LOW APPROACHES...WITH SPEEDS UP TO 30 KT POSSIBLE THROUGH SUNDAY. LOOK FOR THE LOW TO DROP SE INTO THE EASTERN GREAT LAKES ON MONDAY WHILE MERGING WITH ANOTHER LOW MOVING NE OUT OF THE OHIO VALLEY. THE RESULT WILL BE TO SHIFT WINDS TO THE WEST AND THEN NW ON MONDAY...STAYING GENERALLY IN THE 15 TO 25 KT RANGE. EXPECT WINDS TO SWING AROUND TO THE NORTH AT 30 KT MON NIGHT INTO TUE AS THE LOW DEEPENS AND LIFTS INTO NEW ENGLAND. THE STRONGEST WINDS SHOULD BE CONFINED TO EASTERN LAKE SUPERIOR. THE LOW WILL BE SLOW TO MOVE...WHILE HIGH PRESSURE BUILDS IN FROM THE PLAINS TOWARDS WESTERN LAKE SUPERIOR. DUE TO THIS MOVEMENT... NORTHERLY WINDS OF 15 TO 25 KT SHOULD CONTINUE ON THE EAST HALF OF SUPERIOR FOR TUE NIGHT INTO WED...WHILE WINDS DIMINISH BELOW 20 KT OVER WESTERN SUPERIOR. && .MQT WATCHES/WARNINGS/ADVISORIES... UPPER MICHIGAN...NONE. LAKE SUPERIOR...NONE. LAKE MICHIGAN...NONE. && $$ SYNOPSIS/DISCUSSION...ROLFSON AVIATION...KC MARINE...AJ mi AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE MARQUETTE MI 653 AM EST SAT NOV 22 2008 UPDATED AVIATION DISCUSSION FOR 12Z TAF ISSUANCE .SYNOPSIS... (ISSUED AT 5 AM EST) WATER VAPOR IMAGERY AND RUC ANALYSIS SHOW A DEEP TROF EXTENDING S INTO NEW ENGLAND AND THE MID ATLANTIC STATES. RIDGE IS TO THE LEE OF THE ROCKIES AND EXTENDS WELL N TO THE NW TERRITORIES. A WELL-DEFINED SHORTWAVE HAS CUT THRU THE RIDGE AND IS NOW OVER ERN SD. IT`S ON A TRACK TO PASS S OF UPPER MI AND HAVE NO AFFECT ON THE WEATHER HERE. FARTHER UPSTREAM...TROF HAS MOVED ONSHORE IN WRN CANADA WITH STRONG SHORTWAVE IMPACTING WA/BRITISH COLUMBIA (12HR HEIGHT FALLS WERE UPWARDS OF 140M AT 500MB). THIS TROF WILL BE THE NEXT SYSTEM TO AFFECT THE AREA AS IT DROPS INTO THE GREAT LAKES SUN/MON. CLOSER TO HOME...LES CONTINUES OFF LAKE SUPERIOR...BUT HAS WEAKENED SIGNIFICANTLY IN THE LAST FEW HRS. STRENGTHENING LAND BREEZES ARE FOCUSING MAIN BANDS OF -SHSN INTO MAINLY ALGER COUNTY. OTHERWISE... -SHSN/FLURRIES LINGER FROM THE KEWEENAW TO ERN UPPER MI. OVER SW UPPER MI...SKIES CLEARED EARLIER IN THE NIGHT AND TEMPS HAVE NOSE-DIVED UNDER CLEAR SKIES/CALM WIND/FRESH SNOW COVER. AS OF 09Z...LOWEST TEMP IS -15F AT THE WAKEFIELD RAWS SITE. && .DISCUSSION... (ISSUED AT 5 AM EST) WITH SFC RIDGE AXIS ACROSS CNTRL LAKE SUPERIOR AND CNTRL UPPER MI DRIFTING E...ONGOING LES WILL SHIFT OFFSHORE BY MID MORNING UNDER DEVELOPING SRLY FLOW ENHANCED BY LAND BREEZE. OTHERWISE...AREAS THAT START THE DAY MOSTLY SUNNY SHOULD GENERALLY REMAIN THAT WAY WHILE AREAS WITH STRATOCU SHOULD TREND MOSTLY SUNNY BY AFTN. ONLY EXCEPTION WILL BE DOWNWIND OF LAKE MICHIGAN (SRN SCHOOLCRAFT/LUCE COUNTIES) WHERE DEVELOPING SRLY FLOW SHOULD BRING STRATOCU AND SOME FLURRIES DURING THE AFTN. THERE WILL BE SOME CI SPILLING DOWN THE FRONT SIDE OF MID/UPPER RIDGE TO THE W...BUT AT THE MOMENT IT DOES NOT APPEAR THAT THE CI WILL BE TOO THICK OR WIDESPREAD. FAVORED THE LOWER END OF MOS GUIDANCE FOR HIGH TEMPS BASED ON UPSTREAM HIGHS YESTERDAY. NAM/GFS ARE IN REASONABLE AGREEMENT ON DEVELOPING WAA PATTERN TONIGHT/SUN AHEAD OF TROF EMERGING TO THE LEE OF THE ROCKIES. WITH TIGHTER THERMAL GRADIENT TO THE N IN ONTARIO...BEST ISENTROPIC ASCENT THAT WOULD SUPPORT THE POTENTIAL OF MEASURABLE PCPN WILL REMAIN N OF THE FCST AREA AS WELL. INHERITED FCST HAD A MENTION OF -FZDZ LATE TONIGHT/SUN MORNING OVER ROUGHLY THE W HALF OF THE FCST AREA WITH EXCEPTION OF AREAS WHERE SWRLY FLOW DOWNSLOPES... MINIMIZING THREAT. NAM FCST SOUNDINGS STILL LEND SUPPORT TO THIS POSSIBILITY AS TEMPS WILL BE ABOVE -10C IN DEVELOPING LOW-LEVEL SATURATION...AND THERE WILL BE A PERIOD OF UPWARD MOTION STILL OCCURRING AFTER SATURATION IS ACHIEVED. LOCAL REG-WRF RUN PROVIDES SOME SUPPORT...BUT GFS IS LESS SUPPORTIVE OF THE POTENTIAL OF -FZDZ. AT THIS POINT...SEE NO REASON TO PULL THE MENTION OF PATCHY -FZDZ...BUT WILL PUSH BACK TIMING TO LATE TONIGHT DUE TO SLOWER ARRIVAL OF MOISTURE. ONLY OTHER MINOR ISSUE IS THE POSSIBILITY OF A LITTLE SW FLOW LAKE ENHANCED SNOW OVER WRN LAKE SUPERIOR AND NRN LAKE MICHIGAN AS 850MB TEMPS ARE SUFFICIENTLY LOW ENOUGH. OVER LAKE SUPERIOR...WINDS IN THE CLOUD LAYER MAY HAVE ENOUGH OF A WRLY COMPONENT THAT IF SHSN DEVELOP...THEY MAY BRUSH THE KEWEENAW LATE TONIGHT/SUN. WILL ONLY UTILIZE SLIGHT CHC POPS DUE TO UNCERTAINTY IN WIND DIRECTION...AND ALSO BECAUSE DEVELOPMENT MAY ONLY OCCUR N OF THE KEWEENAW WHERE FETCH IS MAXIMIZED. OVER NRN LAKE MICHIGAN...IT APPEARS BY THE TIME ANY DEVELOPMENT OCCURS...WINDS WILL HAVE ENOUGH OF A WRLY COMPONENT TO KEEP ANY -SHSN E OF SCHOOLCRAFT/LUCE COUNTIES. MINOR HEIGHT FALLS BEGIN SUN AFTN AS TROF EDGES E ACROSS THE PLAINS STATES AND SCNTRL CANADA. HOWEVER...HAVE A HARD TIME FINDING ANY FORCING SUFFICIENT TO WARRANT A MENTION OF PCPN. SO...WITH THE EXCEPTION OF THE KEWEENAW...EXPECT A DRY AFTN ACROSS THE FCST AREA. BETTER HEIGHT FALLS DEVELOP SUN NIGHT INTO MON AS TROF REACHES THE GREAT LAKES WITH MID LEVEL LOW SETTLING SE INTO THE UPPER LAKES BY MON EVENING. AS BROAD SFC LOW BEGINS TO ORGANIZE OVER THE UPPER LAKES...NWRLY FLOW AND CAA WILL BEGIN SUN NIGHT. GFS IS QUICKEST WITH THE COOLING...DROPPING 850MB TEMPS TO -9/-10C OVER THE W HALF OF LAKE SUPERIOR BY 12Z MON WHICH WOULD SUPPORT DEVELOPMENT OF LES. NAM IS CONSIDERABLY WARMER...ONLY AROUND -4C. UKMET/ECMWF/REG-WRF FALL BTWN THE NAM/GFS...BUT CLOSER TO THE GFS AND STILL MARGINALLY COLD ENOUGH FOR SOME LES. SO...WITH LIMITED FORCING...PCPN SUN NIGHT MAY BE TIED MOSTLY TO LAKE EFFECT. WILL CONTINUE WITH CHC POPS. PER ECMWF/GFS...AS NW FLOW BECOMES N WITH SFC LOW PRES CONSOLIDATING TOWARD THE LOWER LAKES...EXPECT -SHSN TO EXPAND ACROSS NRN UPPER MI MON. WITH LIMITED OVERLAKE INSTABILITY (850MB TEMPS AROUND -9C) AND WITH MUCH OF THE UPWARD MOTION OCCURRING BELOW THE DENDRITIC SNOW GROWTH TEMP ZONE...EXPECT MAINLY LIGHT ACCUMULATIONS OF SNOW. CONSOLIDATING LOW TO THE SE MAY ALSO SPREAD A GENERAL -SN INTO THE ERN FCST AREA MON. -SHSN WILL CONTINUE UNDER NRLY FLOW MON NIGHT THEN DIMINISH TUE. && .AVIATION (FOR THE 12Z TAF ISSUANCE)... LK EFFECT CONTINUES TO DIMINISH WITH A HIGH PRESSURE RIDGE OVER UPPER MICHIGAN AND THE PRESENCE OF DRY AIR. VSBYS ARE NOW VFR AT BOTH SITES AND WILL STAY THAT WAY THROUGH THE FORECAST PERIOD. CIGS ARE ANOTHER ISSUE. MVFR LAKE EFFECT CLOUDS PERSIST AT BOTH SITES WITH NW WINDS. AS THE WINDS TURN SW THIS MORNING...THE CLOUDS SHOULD EXIT BOTH TAF SITES BY EARLY AFTERNOON. TONIGHT...A SURGE OF WARM AIR WILL HELP SPREAD A VFR STRATUS DECK INTO UPPER MI. THERE ARE SOME HINTS THAT IT COULD LOWER TO MVFR AT CMX LATE...BUT GIVEN ITS LATE TIMING AND UNCERTAINTY...HAVE DECLINED TO MENTION THE LOWER CIGS. ANY LOWERING TO MVFR MORE LIKELY AFTER 12Z SUNDAY. && .MARINE (FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)... A HIGH PRESSURE RIDGE CENTERED OVER THE WESTERN GREAT LAKES WILL MOVE EAST TODAY THROUGH SUNDAY AS AN AREA OF LOW PRESSURE SHIFTS ACROSS SOUTHERN CANADA. VARIABLE WINDS UNDER 25 KTS TODAY WILL BECOME SW TONIGHT AS THE LOW APPROACHES...WITH SPEEDS UP TO 30 KT POSSIBLE THROUGH SUNDAY. LOOK FOR THE LOW TO DROP SE INTO THE EASTERN GREAT LAKES ON MONDAY WHILE MERGING WITH ANOTHER LOW MOVING NE OUT OF THE OHIO VALLEY. THE RESULT WILL BE TO SHIFT WINDS TO THE WEST AND THEN NW ON MONDAY...STAYING GENERALLY IN THE 15 TO 25 KT RANGE. EXPECT WINDS TO SWING AROUND TO THE NORTH AT 30 KT MON NIGHT INTO TUE AS THE LOW DEEPENS AND LIFTS INTO NEW ENGLAND. THE STRONGEST WINDS SHOULD BE CONFINED TO EASTERN LAKE SUPERIOR. THE LOW WILL BE SLOW TO MOVE...WHILE HIGH PRESSURE BUILDS IN FROM THE PLAINS TOWARDS WESTERN LAKE SUPERIOR. DUE TO THIS MOVEMENT... NORTHERLY WINDS OF 15 TO 25 KT SHOULD CONTINUE ON THE EAST HALF OF SUPERIOR FOR TUE NIGHT INTO WED...WHILE WINDS DIMINISH BELOW 20 KT OVER WESTERN SUPERIOR. && .MQT WATCHES/WARNINGS/ADVISORIES... UPPER MICHIGAN...NONE. LAKE SUPERIOR...NONE. LAKE MICHIGAN...NONE. && $$ SYNOPSIS/DISCUSSION...ROLFSON AVIATION...AJ MARINE...AJ mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MARQUETTE MI 500 AM EST SAT NOV 22 2008 .SYNOPSIS... WATER VAPOR IMAGERY AND RUC ANALYSIS SHOW A DEEP TROF EXTENDING S INTO NEW ENGLAND AND THE MID ATLANTIC STATES. RIDGE IS TO THE LEE OF THE ROCKIES AND EXTENDS WELL N TO THE NW TERRITORIES. A WELL-DEFINED SHORTWAVE HAS CUT THRU THE RIDGE AND IS NOW OVER ERN SD. IT`S ON A TRACK TO PASS S OF UPPER MI AND HAVE NO AFFECT ON THE WEATHER HERE. FARTHER UPSTREAM...TROF HAS MOVED ONSHORE IN WRN CANADA WITH STRONG SHORTWAVE IMPACTING WA/BRITISH COLUMBIA (12HR HEIGHT FALLS WERE UPWARDS OF 140M AT 500MB). THIS TROF WILL BE THE NEXT SYSTEM TO AFFECT THE AREA AS IT DROPS INTO THE GREAT LAKES SUN/MON. CLOSER TO HOME...LES CONTINUES OFF LAKE SUPERIOR...BUT HAS WEAKENED SIGNIFICANTLY IN THE LAST FEW HRS. STRENGTHENING LAND BREEZES ARE FOCUSING MAIN BANDS OF -SHSN INTO MAINLY ALGER COUNTY. OTTHERWISE... -SHSN/FLURRIES LINGER FROM THE KEWEENAW TO ERN UPPER MI. OVER SW UPPER MI...SKIES CLEARED EARLIER IN THE NIGHT AND TEMPS HAVE NOSE-DIVED UNDER CLEAR SKIES/CALM WIND/FRESH SNOW COVER. AS OF 09Z...LOWEST TEMP IS -15F AT THE WAKEFIELD RAWS SITE. && .DISCUSSION... WITH SFC RIDGE AXIS ACROSS CNTRL LAKE SUPERIOR AND CNTRL UPPER MI DRIFTING E...ONGOING LES WILL SHIFT OFFSHORE BY MID MORNING UNDER DEVELOPING SRLY FLOW ENHANCED BY LAND BREEZE. OTHERWISE...AREAS THAT START THE DAY MOSTLY SUNNY SHOULD GENERALLY REMAIN THAT WAY WHILE AREAS WITH STRATOCU SHOULD TREND MOSTLY SUNNY BY AFTN. ONLY EXCEPTION WILL BE DOWNWIND OF LAKE MICHIGAN (SRN SCHOOLCRAFT/LUCE COUNTIES) WHERE DEVELOPING SRLY FLOW SHOULD BRING STRATOCU AND SOME FLURRIES DURING THE AFTN. THERE WILL BE SOME CI SPILLING DOWN THE FRONT SIDE OF MID/UPPER RIDGE TO THE W...BUT AT THE MOMENT IT DOES NOT APPEAR THAT THE CI WILL BE TOO THICK OR WIDESPREAD. FAVORED THE LOWER END OF MOS GUIDANCE FOR HIGH TEMPS BASED ON UPSTREAM HIGHS YESTERDAY. NAM/GFS ARE IN REASONABLE AGREEMENT ON DEVELOPING WAA PATTERN TONIGHT/SUN AHEAD OF TROF EMERGING TO THE LEE OF THE ROCKIES. WITH TIGHTER THERMAL GRADIENT TO THE N IN ONTARIO...BEST ISENTROPIC ASCENT THAT WOULD SUPPORT THE POTENTIAL OF MEASURABLE PCPN WILL REMAIN N OF THE FCST AREA AS WELL. INHERITED FCST HAD A MENTION OF -FZDZ LATE TONIGHT/SUN MORNING OVER ROUGHLY THE W HALF OF THE FCST AREA WITH EXCEPTION OF AREAS WHERE SWRLY FLOW DOWNSLOPES... MINIMIZING THREAT. NAM FCST SOUNDINGS STILL LEND SUPPORT TO THIS POSSIBILITY AS TEMPS WILL BE ABOVE -10C IN DEVELOPING LOW-LEVEL SATURATION...AND THERE WILL BE A PERIOD OF UPWARD MOTION STILL OCCURRING AFTER SATURATION IS ACHIEVED. LOCAL REG-WRF RUN PROVIDES SOME SUPPORT...BUT GFS IS LESS SUPPORTIVE OF THE POTENTIAL OF -FZDZ. AT THIS POINT...SEE NO REASON TO PULL THE MENTION OF PATCHY -FZDZ...BUT WILL PUSH BACK TIMING TO LATE TONIGHT DUE TO SLOWER ARRIVAL OF MOISTURE. ONLY OTHER MINOR ISSUE IS THE POSSIBILITY OF A LITTLE SW FLOW LAKE ENHANCED SNOW OVER WRN LAKE SUPERIOR AND NRN LAKE MICHIGAN AS 850MB TEMPS ARE SUFFICIENTLY LOW ENOUGH. OVER LAKE SUPERIOR...WINDS IN THE CLOUD LAYER MAY HAVE ENOUGH OF A WRLY COMPONENT THAT IF SHSN DEVELOP...THEY MAY BRUSH THE KEWEENAW LATE TONIGHT/SUN. WILL ONLY UTILIZE SLIGHT CHC POPS DUE TO UNCERTAINTY IN WIND DIRECTION...AND ALSO BECAUSE DEVELOPMENT MAY ONLY OCCUR N OF THE KEWEENAW WHERE FETCH IS MAXIMIZED. OVER NRN LAKE MICHIGAN...IT APPEARS BY THE TIME ANY DEVELOPMENT OCCURS...WINDS WILL HAVE ENOUGH OF A WRLY COMPONENT TO KEEP ANY -SHSN E OF SCHOOLCRAFT/LUCE COUNTIES. MINOR HEIGHT FALLS BEGIN SUN AFTN AS TROF EDGES E ACROSS THE PLAINS STATES AND SCNTRL CANADA. HOWEVER...HAVE A HARD TIME FINDING ANY FORCING SUFFICIENT TO WARRANT A MENTION OF PCPN. SO...WITH THE EXCEPTION OF THE KEWEENAW...EXPECT A DRY AFTN ACROSS THE FCST AREA. BETTER HEIGHT FALLS DEVELOP SUN NIGHT INTO MON AS TROF REACHES THE GREAT LAKES WITH MID LEVEL LOW SETTLING SE INTO THE UPPER LAKES BY MON EVENING. AS BROAD SFC LOW BEGINS TO ORGANIZE OVER THE UPPER LAKES...NWRLY FLOW AND CAA WILL BEGIN SUN NIGHT. GFS IS QUICKEST WITH THE COOLING...DROPPING 850MB TEMPS TO -9/-10C OVER THE W HALF OF LAKE SUPERIOR BY 12Z MON WHICH WOULD SUPPORT DEVELOPMENT OF LES. NAM IS CONSIDERABLY WARMER...ONLY AROUND -4C. UKMET/ECMWF/REG-WRF FALL BTWN THE NAM/GFS...BUT CLOSER TO THE GFS AND STILL MARGINALLY COLD ENOUGH FOR SOME LES. SO...WITH LIMITED FORCING...PCPN SUN NIGHT MAY BE TIED MOSTLY TO LAKE EFFECT. WILL CONTINUE WITH CHC POPS. PER ECMWF/GFS...AS NW FLOW BECOMES N WITH SFC LOW PRES CONSOLIDATING TOWARD THE LOWER LAKES...EXPECT -SHSN TO EXPAND ACROSS NRN UPPER MI MON. WITH LIMITED OVERLAKE INSTABILITY (850MB TEMPS AROUND -9C) AND WITH MUCH OF THE UPWARD MOTION OCCURRING BELOW THE DENDRITIC SNOW GROWTH TEMP ZONE...EXPECT MAINLY LIGHT ACCUMULATIONS OF SNOW. CONSOLIDATING LOW TO THE SE MAY ALSO SPREAD A GENERAL -SN INTO THE ERN FCST AREA MON. -SHSN WILL CONTINUE UNDER NRLY FLOW MON NIGHT THEN DIMINISH TUE. && .AVIATION (FOR THE 06Z TAF ISSUANCE)... LK EFFECT DIMINISHES AT CMX THROUGH THE NIGHT AS WINDS BECOME SRLY WITH ARRIVAL OF HIGH PRESSURE RIDGE. EXPECT MVFR CIGS AND OCCASIONAL MVFR TO IFR VSBY TO LINGER UNTIL DAYBREAK. SOME MVFR CLOUDS AND FLURRIES AT SAW UNTIL LATE TONIGHT BUT CLEARING SKIES TAKE OVR AFTER DAYBREAK. AFTER TONIGHT...VFR CONDITIONS SHOULD BE THE RULE AT BOTH SITES INTO SATURDAY EVENING. && .MARINE (FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)... A HIGH PRESSURE RIDGE CENTERED OVER THE WESTERN GREAT LAKES WILL MOVE EAST TODAY THROUGH SUNDAY AS AN AREA OF LOW PRESSURE SHIFTS ACROSS SOUTHERN CANADA. VARIABLE WINDS UNDER 25 KTS TODAY WILL BECOME SW TONIGHT AS THE LOW APPROACHES...WITH SPEEDS UP TO 30 KT POSSIBLE THROUGH SUNDAY. LOOK FOR THE LOW TO DROP SE INTO THE EASTERN GREAT LAKES ON MONDAY WHILE MERGING WITH ANOTHER LOW MOVING NE OUT OF THE OHIO VALLEY. THE RESULT WILL BE TO SHIFT WINDS TO THE WEST AND THEN NW ON MONDAY...STAYING GENERALLY IN THE 15 TO 25 KT RANGE. EXPECT WINDS TO SWING AROUND TO THE NORTH AT 30 KT MON NIGHT INTO TUE AS THE LOW DEEPENS AND LIFTS INTO NEW ENGLAND. THE STRONGEST WINDS SHOULD BE CONFINED TO EASTERN LAKE SUPERIOR. THE LOW WILL BE SLOW TO MOVE...WHILE HIGH PRESSURE BUILDS IN FROM THE PLAINS TOWARDS WESTERN LAKE SUPERIOR. DUE TO THIS MOVEMENT... NORTHERLY WINDS OF 15 TO 25 KT SHOULD CONTINUE ON THE EAST HALF OF SUPERIOR FOR TUE NIGHT INTO WED...WHILE WINDS DIMINISH BELOW 20 KT OVER WESTERN SUPERIOR. && .MQT WATCHES/WARNINGS/ADVISORIES... UPPER MICHIGAN...NONE. LAKE SUPERIOR...NONE. LAKE MICHIGAN...NONE. && $$ SYNOPSIS/DISCUSSION...ROLFSON AVIATION...JLA MARINE...AJ mi AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE MARQUETTE MI 1232 AM EST SAT NOV 22 2008 UPDATED AVIATION DISCUSSION FOR 06Z TAFS .UPDATE... (ISSUED AT 1015 PM EST FRI NOV 21) BEEN DIFFICULT TO GET A GOOD HANDLE ON THE LK EFFECT THIS EVENING. BASED ON RADAR IMGRY...LOCALIZED BANDS ARE QUITE STRONG...LIKELY PRODUCING OVR AN INCH PER HOUR SNOW RATES...AS STRONG OVERWATER INSTABILITY COMBINES WITH WEAKENING GRADIENT WINDS AS HIGH PRESSURE APPROACHES. RESULT IS NW WINDS ON ERN LK SUPERIOR CONVERGING WITH LAND BREEZES OFF BOTH UPR MI AND ONTARIO...LEADING TO SHARP CONVERGENCE. PRIMARY BAND DUMPED A QUICK 5 TO 9 INCHES OF SNOW OUT AT SAULT STE MARIE THIS EVENING BUT BASED ON SPOTTER REPORT ALONG LK SUPERIOR IN FAR NRN LUCE COUNTY AND THE OBSERVATION AT ERY IT APPEARS NOT MUCH IS HAPPENING IN LUCE COUNTY. MEANWHILE ...CONVERGENCE BAND HAS IMPACTED FAR NRN MQT COUNTY FROM HALFWAY VILLAGE NORTH TO BIG BAY AND SE INTO MAINLY NW ALGER COUNTY THIS EVENING. DESPITE RADAR SHOWING PERSISTENT BANDING IN THESE AREAS...AVILABLE WEB CAMERAS DO NOT INDICATE MUCH IN WAY OF VERY BAD VSBY OR HEAVY SNOW. OVR FAR WRN UPR MI...CLEARING SKIES HAVE ALLOWED TEMPS TO PLUMMET TO AT OR BLO ZERO ALREADY THIS EVENING IN GOGEBIC COUNTY. MADE EARLIER ADJUSTMENT TO LOWER TEMPS FROM ROUGHLY 5 TO 10 BELOW ZERO IN THE INTERIOR SW WHERE CLEAR SKIES RULE THROUGH THE NIGHT. BASED ON LAST NIGHTS OBS BENEATH THE RIDGE IN MANITOBA AND FACT THAT PWAT MINIMUM MOVING ACROSS ONLY ENHANCES RADIATIONAL COOLING AND FRESH SNOW PACK...WOULD NOT BE SURPRISED TO SEE MINS AS LOW AS 15 BLO IN FAVORED COLD SPOTS IN GOGEBIC/SOUTHERN ONTONAGON/NW IRON COUNTY. FOLLOWING THE RUC13 MODEL FOR THE UPDATE AS ITS 18Z/00Z RUNS HAD GOOD HANDLE ON THE INCREASINGLY MESOSCALE DOMINANTED LOW LEVEL WIND FIELD. RUC13 INDICATES CONVERGENCE AREA NEAR SSM AND JUST TO THE NORTH SINKS INTO NRN LUCE COUNTY THROUGH 06Z AND THEN MERGES WITH THE ONGOING CONVERGENCE AREA OVR ALGER INTO NRN SCHOOLCRAFT THROUGH 12Z. ADDITIONAL SNOW AMOUNTS FOR THE REST OF THE NIGHT IN THE HIGHEST CONVERGENCE AREA WILL LIKELY BE UP TO AN INCH PER HOUR. WARNING FOR THESE TWO ZONES RUNS THROUGH 12Z SATURDAY...WHICH SEEMS FINE. THOUGHT LUCE SHOULD HAVE SOMETHING OUT TOO WITH THE POTENTIAL FOR LOCALLY HEAVY SNOW SHOWERS TO SHIFT THROUGH TIL SHORTLY AFTER MIDNIGHT...SO HAVE ISSUED A LK EFFECT SNOW ADVY FOR THE REST OF THE NIGHT THERE. INCREASING LAND BREEZE EVENTUALLY PUSHES STRONGER SNOW SHOWERS OUT OF THE BIG BAY AREA IN MARQUETTE COUNTY AFTER MIDNIGHT. LOW CLOUDS SHOULD LINGER THOUGH AS 925MB-900MB WINDS VEER NRLY WITH THE HIGH PRESSURE AREA BUILDING ACROSS NRN LK SUPERIOR. GOING FCST HAD THIS HANDLED WELL. && .SYNOPSIS... (ISSUED AT 430 PM EST FRI NOV 21) 12Z RAOBS/LATEST WV IMAGERY AND RUC ANALYSIS SHOW DEEP TROF OVER ERN NAMERICA DOWNSTREAM OF RDG OVER THE ROCKIES. COLD NNW FLOW (12Z H85 TEMP -25C AT YPL VS -18C AT GRB) BTWN ARCTIC HI PRES JUST E OF LK WINNIPEG AND LO PRES OVER SE CAN OVER THE RELATIVELY WARM WATERS OF LK SUP (5C OVER THE W TO 8C OVER THE E PER GLERL ANALYSIS) CONTINUES TO GENERATE LK EFFECT SHSN ACRS UPR MI. THE HEAVIER SHSN ARE NOTED OVER THE E HALF WITH LONGER FETCH AVBL OVER THE WATER AS WELL AS SOME MOISTENING OFF LK NIPIGON OF FAIRLY DRY AIRMASS SHOWN ON 12Z YPL RAOB. BUT LES ALSO CONTINUES OVER THE W DESPITE LO INVRN BASE ARND H9-925 AS SHOWN ON 12Z RAOB FM INL AND 12Z TAMDAR SDNG FM YQT. LES BANDS ARE MORE WELL DVLPD TDAY THAN YDAY OVER THE W WITH SOME CONFLUENCE BTWN LAND BREEZE FLOW OFF NW WI AND MORE NNW FLOW OVER WRN LK AS WELL AS SHALLOW MSTR BLO THE INVRN BASE SHOWN ON INL RAOB SUPPORTING AREA OF SC/-SN OVER NE MN MAKING BANDS A BIT MORE WELL DEFINED. CALLS TO SPOTTERS IN ONTONAGON COUNTY SUG THE SN UNDER THE BANDS IS RELATIVELY LGT WITH NO MORE THAN AN INCH EVERY 3-4 HOURS DESPITE RELATIVELY LO VSBYS AT TIMES SHOWN BY CMX/IWD OBS. A SHRTWV IS NOTED OVER THE NRN PLAINS RIDING THRU THE MEAN UPR RDG AXIS. && .SHORT TERM DISCUSSION (TNGT THRU SAT)... (ISSUED AT 430 PM EST) MAIN FCST CONCERNS TNGT ARE LES TRENDS/AMTS/NEED TO CHG GOING HEADLINES. FOCUS FOR SAT SHIFTS TO MAINLY TEMPS WITH SFC HI PRES RDG TO THE W FCST FINALLY TO EASE INTO THE GRT LKS. FOR TNGT...LOOK FOR RISING UPR HGTS AS LARGER SCALE MODELS SHOW UPR TROF OVER ERN NAMERICA GRDLY EDGING EWD...ALLOWING SFC RDG AXIS TO THE W TO DRIFT INTO THE UPR GRT LKS. WITH SLOWLY DIMINISHING WINDS/ LOWERING INVRN BASE WITH APRCH OF RDG...EXPECT LES BANDS IN THE NW WINDS SN BELTS THIS EVNG TO GRDLY WEAKEN WITH TIME. ONCE WINDS REALLY DIMINISH AFT 06Z...SOME MESOSCALE WIND IMPACTS MAY BEGIN TO SHOW UP. LOCAL WRF-ARW/12Z NAM/12Z CNDN AND ESPECIALLY THE RUC13 SHOW NE LAND BREEZE OFF ONTARIO ENHANCING THE LLVL CNVGC IN ALGER COUNTY WITH VORTEX DVLPG NEAR P53. THERE ARE ALSO HINTS OVER THE WRN COUNTIES THAT CONFLUENCE BTWN DVLPG LAND BREEZE OFF NW WI/SLY FLOW TO THE W OF SFC RDG AXIS AND LINGERING NNW FLOW OVER CNTRL LK SUP MAY GENERATE BAND OF SHSN IN THAT AREA THAT GRDLY SHIFTS TO THE NE WITH SYNOPTIC WSHFT TO THE SSW. WL CARRY NO MORE THAN CHC POPS FOR THIS EVENT OVER THE W GIVEN RELATIVELY LO INVRN BASE THERE ALREADY. BUT WL MAINTAIN HIER LIKELY POPS IN ALGER COUNTY FOR A LONGER PD. AS FOR HEADLINES...OPTED TO MAINTAIN GOING ENDING TIME OF 03Z FOR LUCE COUNTY BUT EXTENDED GOING/VERIFIED WRNGS FOR ALGER/NRN SCHOOLCRAFT LONGER TO ACCOUNT FOR PSBL SHARPER CNVGC IN PRESENCE OF HIER INVRN (ARND H825 THRU 09Z SAT AT P53 PER NAM FCST) THAN WOULD BE EXPECTED OVER THE W. OTRW...EXPECT THE LOWEST MIN TEMPS NEAR THE WI BORDER WHERE CLRG IS MOST LIKELY AWAY FM LK SUP. WL TEND AOB THE LO END OF MOS GUIDANCE IN THESE AREAS TO INCLUDE SOME SUB ZERO READINGS. MORE NLY H925 FLOW OFF LK SUP MAY MAINTAIN MORE CLD/HIER TEMPS OVER THE NCNTRL. AS THE SFC RDG AXIS SHIFTS TO THE E ON SAT WITH A SLOW DEPARTURE OF THE ERN TROF...THE LLVL FLOW WL TURN TO THE S AND END LINGERING LES. OTRW...FCST SDNGS SHOW DRY LLVLS. SO EXCEPT FOR SOME HI CLD ON THE NRN FRINGES OF SHRTWV NOW OVER THE NRN PLAINS THAT IS PROGGED TO DROP SEWD THRU THE UPR MIDWEST...THE DAY WL BE MOSUNNY. THE DAY WL BE WARMER THAN TDAY WITH DEPARTURE OF H85 THERMAL TROF...BUT HI STABILITY OF FCST SDNGS/TEMPS OBSVD UPSTREAM THIS AFTN IN THE NRN PLAINS SUG THE LO END OF MOS GUIDANCE FOR HI TEMPS WL BE MORE APPROPRIATE. && .LONG TERM (SATURDAY NIGHT THROUGH FRIDAY)... (ISSUED AT 430 PM EST) SATURDAY NIGHT INTO SUNDAY...THE NAM AND GFS WERE IN REASONABLE AGREEMENT WITH THE OVERALL WAA PATTERN DEVELOPING ACROSS THE WRN GREAT LAKES. 280K-290K ISENTROPIC LIFT (900-750 MB) MAY PROVIDE ENOUGH LOW LEVEL MOISTENING...PER MDL RH FOR POTENTIAL OF SOME PATCHY -FZDZ OVER THE WEST HALF OF THE CWA BTWN 06Z-18Z/SUN AS THE THE MOISTURE REMAINS BLO THE -8C ISOTHERM. WITH WSW FLOW...DOWNSLOPE AREAS CLOSER TO LAKE SUPERIOR WOULD BE LESS SUSCEPTIBLE TO ANY FRZG PCPN. BY LATE SUNDAY...SOME LIGHT SNOW MAY MOVE INTO WRN UPPER MI...PER LCLY RUN REGIONAL WRF/ARW AND THE GFS SUPPORTED BY WEAK TO MODERATE QVECTOR CONV AHEAD OF A MID LEVEL TROUGH MOVING OUT OF THE NRN PLAINS. SUNDAY NIGHT THROUGH MONDAY NIGHT...PER 12Z GFS AND 00Z ECMWF...A SHRTWV TROUGH IS EXPECTED TO DROP SE FROM MANITOBA THROUGH THE GREAT LAKES. FALLING HEIGHTS AND MODERATE QG FORCING WITH THE MID LEVEL LOW WILL SUPPORT LIGHT SNOW CHANCES ACROSS THE AREA SUN NIGHT INTO EARLY MON. BEHIND THE LOW...SOME LAKE ENHANCED SNOW MAY BE POSSIBLE WITH CYCLONIC NRLY FLOW DEVELOPING AND 850 MB TEMPS DROPPING TO AROUND -8C. WITH ONLY MARGINAL INSTABILITY/LIFT FCST...MAINLY LIGHT ACCUMULATIONS WOULD BE EXPECTED. TUESDAY...AS THE DEEPER MOISTURE DEPARTS AND 850 MB TEMPS ONLY REMAIN NEAR -10C...PER ECMWF/GFS BLEND...ANY LES SHOULD REMAIN ON THE LIGHT SIDE. WEDNESDAY-FRIDAY...MID LEVEL AND SFC RIDGING BUILDS INTO THE WRN LAKES BRINGING MAINLY DRY WEATHER. UNCERTAINTY BY THE END OF THE WEEK INCREASES WITH THE PATH/SPEED OF ANOTHER MID LEVEL LOW DROPPING SSE TOWARD THE GREAT LAKES. FOR NOW...THE GLOBAL MDLS AND GFS ENSEMBLE SUGGESTS THAT ANY PCPN WITH THIS FEATURE WOULD BE AFTER THE FCST PERIOD. && .AVIATION (FOR THE 06Z TAF ISSUANCE)... LK EFFECT DIMINISHES AT CMX THROUGH THE NIGHT AS WINDS BECOME SRLY WITH ARRIVAL OF HIGH PRESSURE RIDGE. EXPECT MVFR CIGS AND OCCASIONAL MVFR TO IFR VSBY TO LINGER UNTIL DAYBREAK. SOME MVFR CLOUDS AND FLURRIES AT SAW UNTIL LATE TONIGHT BUT CLEARING SKIES TAKE OVR AFTER DAYBREAK. AFTER TONIGHT...VFR CONDITIONS SHOULD BE THE RULE AT BOTH SITES INTO SATURDAY EVENING. && .MARINE (FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)... A HIGH PRESSURE RIDGE CENTERED OVER THE MISSISSIPPI RIVER VALLEY WILL PUSH A RIDGE EASTWARD ACROSS THE UPPER GREAT LAKES THROUGH SUNDAY MORNING. NORTH TO NORTHWEST WINDS TO 30 KNOTS WILL DIMINISH THIS EVENING WITH THE APPROACH OF THE RIDGE. AS THE HIGH MOVES TOWARD THE ATLANTIC SEABOARD IN THE SOUTHEAST...A LOW OVER THE CANADIAN PRAIRIES WILL MOVE INTO THE UPPER GREAT LAKES. THIS LOW WILL MOVE SOUTHEAST TOWARD THE MID ATLANTIC STATES ON TUESDAY. NORTH WINDS IN THE WAKE OF THIS LOW WILL INCREASE TO 30 KNOTS LATE MONDAY INTO TUESDAY...WITH GALES POSSIBLE OVER PORTIONS OF THE EAST HALF. LOOK FOR A RIDGE OF HIGH PRESSURE TO FOLLOW INTO THE LOWER GREAT LAKES FROM THE PLAINS. THE APPROACH OF THIS RIDGE WILL WEAKEN THE STRONG NORTH WINDS. && UPPER MICHIGAN... LAKE EFFECT SNOW WARNING UNTIL 7 AM EST SATURDAY FOR MIZ006-085. LAKE EFFECT SNOW ADVISORY UNTIL 6 AM EST SATURDAY FOR MIZ007. LAKE SUPERIOR...NONE. LAKE MICHIGAN...NONE. && $$ UPDATE...JLA SYNOPSIS/SHORT TERM...KC LONG TERM...JLB AVIATION...JLA MARINE...KC mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN 508 PM CST SUN NOV 23 2008 .AVIATION.../00Z TAF ISSUANCE/ INVERTED TROUGH CURRENTLY OVER THE AREA... WITH A DECENT SHORTWAVE SWING THROUGH FROM WEST TO EAST OVER THE NEXT 6 HOURS. IT APPEARS THERE WILL BE A BRIEF WINDOW WHEN THE UPPER WAVE AND LOW LEVEL TROUGH ARE ABLE TO WORK TOGETHER AND SQUEEZE OUT SOME MOISTURE IN THE FORM OF SNOWFLAKES. THIS CAN ALREADY BE SEEN ON THE LATEST RADAR IMAGERY... SHOWING BANDED PCPN MAINLY DUE TO MID-LEVEL FRONTOGENESIS AS ADVERTISED BY THE RUC/NAM/GFS. MOST OF THIS IS VIRGA... ALTHOUGH SOME OF THE HEAVIER RETURNS ARE MAKING IT TO THE SURFACE. EXPECT A BIT MORE TO MAKE IT TO THE GROUND AS THE SYSTEM MOVES EAST THIS EVENING... SO INCLUDED SOME MENTION OF SN IN MOST OF THE TAF SITES... WITH GENERALLY MVFR CONDITIONS AND A BRIEF WINDOW OF IFR POSSIBLE. WINDS WILL SLOWLY PICK UP TONIGHT... THEN PICK UP IN EARNEST ON MONDAY AS THE MAIN COLD FRONT DROPS SOUTH THROUGH THE AREA. THIS FRONT IS BEING PUSHED SOUTHWARD BY AN IMPRESSIVE SHORTWAVE WHICH CAN CURRENTLY BE SEEN DIVING SOUTHEAST THROUGH MANITOBA. THIS FEATURE WILL BRING A LOWER CLOUD DECK BACK INTO THE AREA... WITH GUSTIER WINDS BY AFTERNOON AND THE CHANCE FOR SOME SNOW SHOWER ACTIVITY... PARTICULARLY OVER THE EASTERN PORTION OF THE AREA WHERE DEEPER MOISTURE WILL BE PRESENT ALONG WITH IMPRESSIVE LAPSE RATES BY MID TO LATE AFTERNOON. THANKS TO CWSU ZMP FOR COLLABORATION... THEIR DISCUSSION IS INCLUDED BELOW. INCLUDED FROM CWSU ZMP... RADAR INDICATING SOME PCPN ALOFT IN A SW-NE ORIENTED BANDS CENTERED THRU THE EAST-CENTRAL MN. SINCE SURFACE IS FAIRLY DRY IT WILL TAKE SOME TIME TO MOISTEN THE LOWER LEVELS AND DROP THE CEILINGS WITH TIME INTO THE EVENING. JUST AS IT GETS WET ENOUGH TO CAUSE PCPN TO HAPPEN THEN THE SUPPORT MOVES AWAY AND COULD GIVE US UP TO SEVERAL HRS OF PCPN THIS EVENING. TYPE SHUD BE SNOW BUT IF IT STARTS EARLY ENUF IT CUD BE SOME LIQUID ALSO. WINDS HAVE BEEN VIRTUALLY CALM FOR SEVERAL HOURS BUT SHUD FAVOR NW ONCE THE WIND STARTS INCRG IN SPEEDS INTO THE EVENING. HEAVIEST PCPN CUD DROP VSBY INTO IFR BRFLY THIS EVENING OTRW IT SHUD BE MVFR FOR THE MOST PART. BY MIDNITE LOCAL IT SHUD BE ALL DONE WITH BREAKS INTO THE MORNING. MONDAY SHUD HAVE INCRG CLOUDS NR MVFR HEIGHTS WITH SOME GUSTS INTO THE AFTN. && .PREV DISCUSSION... /ISSUED 306 PM CST SUN NOV 23 2008/ GOOD CONFIDENCE IN THE FORECAST THROUGH THE MIDDLE PART OF THE WEEK PRIOR TO THE UPCOMING HOLIDAY...BUT CONFIDENCE QUICKLY WANES FROM THANKSGIVING THROUGH THE END OF THE PERIOD. AFTERNOON GOES MOISTURE CHANNEL IMAGERY SHOWS FAIRLY PROGRESSIVE PATTERN IN PLACE AT THE CURRENT TIME BUT IT IS STARTING TO SHOW SIGNS OF AMPLIFYING. WEAK UPPER RIDGE HAS PASSED OVERHEAD WITH TROUGHING MOVING IN ON ITS HEELS. MAIN UPPER LOW CIRCULATION IS SAGGING SOUTHEASTWARD TOWARDS LAKES WINNIPEG AND MANITOBA WITH TROUGH AXIS EXTENDING SOUTHWESTWARD ACROSS THE LEE OF THE ROCKIES. A VORTICITY MAXIMA IS QUICKLY MOVING EAST-NORTHEAST TOWARDS CENTRAL MN AND NORTHERN WI THIS AFTERNOON EXHIBITED BY NARROW CHANNEL OF SHARP DRYING WORKING ALONG THE ND/SD BORDER. SFC ANALYSIS SHOWS WELL ORGANIZED SFC LOW OVER NORTHERN MANITOBA IN ASSOCIATION WITH THE CLOSED UPPER LOW. WARM FRONTAL BOUNDARY EXTENDS TO ITS SOUTHEAST ACROSS WESTERN/CENTRAL ONTARIO. A COOL FRONTAL BOUNDARY EXTENDS SOUTHWARD ALONG THE MN/DAKOTAS BORDER AND MEETS UP WITH A WEAK SFC LOW ACROSS EASTERN NEBRASKA. SHORTWAVE MOVING ACROSS SOUTHERN SOUTH DAKOTA AT 21Z WILL CONTINUE EAST-NORTHEAST THIS EVENING. UPPER JET ASSOCIATED WITH THE CLOSED LOW OVER MANITOBA APPEARS TO BE FURTHER WEST THAN EARLIER FORECASTS /AS IS THE LOW ITSELF/ RESULTING IN A DECREASED AFFECT FROM THE LEFT EXIT REGION. UPPER JET CURRENTLY INCREASING ACROSS IOWA SHOULD PROVIDE A BRIEF WINDOW OF LEFT FRONT QUAD ASCENT EARLY THIS EVENING BEFORE THAT SHIFTS TO THE EAST. NONETHELESS FORCING FOR ASCENT IS EXPECTED TO INCREASE AS THE SHORTWAVE TROUGH ENCOUNTERS THE SFC INVERTED TROUGH. CURRENT RADAR MOSAIC SHOWS BANDS OF MID LEVEL RETURNS WITH LITTLE SHOWING UP IN SFC OBS DUE TO LOW LEVEL DRY AIR THAT IS STILL BEING OVERCOME. THIS WILL BE THE CHALLENGE THROUGH THE EVENING AS DECENT FRONTOGENETICAL FORCING IN THE H7-H6 LAYER SAGS SOUTHEASTWARD ACROSS THE CWA. MUCH OF THE FORCING WILL GO TOWARDS SATURATION EARLY ON...WITH A LARGE DRY WEDGE STILL SHOWING UP ON RECENT AIRCRAFT SOUNDINGS FROM KMSP. DO EXPECT SNOW TO FALL TO THE SURFACE DURING THE EARLY EVENING ACROSS THE NORTH CENTRAL CWA BEFORE SHIFTING SOUTHEAST. DUE TO THE SPEED OF THE SYSTEM DURATION OF SNOW WILL BE SHORT LIVED...PROBABLY JUST A COUPLE HOURS...WHICH WILL LIMIT AMOUNTS. GIVEN THE NATURE OF THE FORCING BRIEF PERIODS OF MODERATE SNOW ARE EXPECTED AND A QUICK COUPLE TENTHS MAY BE RECEIVED. GENERALLY ABOUT A HALF INCH WILL BE POSSIBLE FROM NEW ULM TO THE TWIN CITIES TO RICE LAKE AND POINTS SOUTHEAST. SOME ISOLATED LOCATIONS MAY SEE AROUND AN INCH. AREAS ALONG THE IA BORDER MAY SEE LITTLE PRECIP WITH DRY AIR MOVING IN ALOFT AS SEEN ON LATEST WATER VAPOR IMAGERY. A BRIEF WINDOW OF RAIN/SNOW MIX MAY OCCUR BETWEEN NOW AND 01Z OR SO WITH WARM LOW LEVEL TEMPS BUT FORECAST SOUNDINGS SHOW WET BULB TEMPS TO BE BELOW ZERO THROUGH THE COLUMN ALLOWING EVAPORATIVE COOLING DURING THE TOP DOWN SATURATION TO YIELD JUST ABOUT ALL SNOW AT ONSET. THE WAVE WILL QUICKLY MOVE TO THE SOUTHEAST SO MOST OF THE PRECIP WILL END BY MIDNIGHT. SKIES MAY EVEN SCATTER OUT FOR A PERIOD PRIOR TO DAYBREAK AS SUBSIDENCE FILLS IN BEHIND THE WAVE. THE UPPER LOW CURRENTLY OVER CENTRAL/NORTHERN MANITOBA WILL CONTINUE TO DROP SOUTHEASTWARD ENTERING THE ARROWHEAD BY MIDDAY. CYCLONIC VORTICITY ADVECTION WILL INCREASE AHEAD OF ATTENDANT VORT MAX WHICH SWINGS FROM NORTHWEST TO SOUTHEAST ACROSS THE NORTHEASTERN TWO-THIRDS OR SO OF THE AREA. COLD ADVECTION WILL ALREADY BE UNDERWAY BUT A SECONDARY SHOT OF COLD AIR WILL ARRIVE WITH THE VORT MAX BY AFTERNOON. MOISTURE WILL BE FAIRLY MEAGER WITH PWATS AROUND A QUARTER INCH WITH A MODEST INCREASE AHEAD OF THE WAVE. WITH THE COLD ADVECTION /H85 TEMPS FALLING FROM -6 C TO -12 C DURING THE DAY/ THE DENDRITIC GROWTH ZONE LOWERS INTO THE LAYER OF HIGHER MOISTURE CONTENT AND ASCENT. EXPECT MOISTURE AND FORCING WILL BE SUFFICIENT FOR SNOW SHOWERS TO BE WRUNG OUT FROM MID/LATE MORNING THROUGH THE AFTERNOON. WITH THE COLD ADVECTION SNOW TO WATER RATIOS SHOULD BE ELEVATED AND FEEL THAT UP TO A HALF INCH MAY ACCUMULATE ACROSS THE EAST CENT WI COUNTIES AND A DUSTING TO A QUARTER INCH ACROSS THE FAR EAST CENT MN CWA. BY TUESDAY THE UPPER FLOW PATTERN WILL BE MUCH MORE AMPLIFIED THAN IT IS CURRENTLY WITH A DEEP TROUGH OVER THE LOWER GREAT LAKES AND A BROAD RIDGE OVER THE ROCKIES. SFC HIGH PRESSURE WILL BE OVERHEAD TUESDAY MORNING. THE PRESENCE OF THE HIGH COMBINED WITH THE COLD AIR BROUGHT BY THE PASSING FRONT WILL SUPPORT TUESDAY MORNING TEMPS IN THE TEENS TO AROUND 20 DEGREES. THE FLOW PATTERN WILL FAIRLY BLOCKED UP SO THE HIGH WILL TAKE ITS TIME CROSSING THE AREA INTO WEDNESDAY. WEDNESDAY CONTINUES TO LOOK QUIET ACROSS MUCH OF THE REGION. THINGS GET MORE COMPLEX INTO THANKSGIVING DAY AND THROUGH THE HOLIDAY WEEKEND. GFS AND ECMWF ARE AT ODDS WITH THE HANDLING OF THE FLOW COMING INTO THE WEST COAST OF NORTH AMERICA. THIS AFTERNOONS WATER VAPOR SHOWS A VERY SHARP AND DEEP LONGWAVE TROUGH STRETCHING FROM ALASKA SOUTHWARD ALONG AREAS BETWEEN 140W AND 145W AND EXTENDING AS FAR SOUTH AS 30N AND BEYOND. ANOTHER DEEP TROUGH IS RACING INTO THE NORTHERN PORTIONS OF THIS TROUGH FROM THE ALEUTIANS WITH ANOTHER WAVE ROUNDING THE BASE OF THE TROUGH NEAR 30N. BOTH THE GFS AND ECMWF CLOSE THE SOUTHERN PORTION OF THE TROUGH OFF BY MONDAY MORNING. THIS OCCURS AS THE ALEUTIAN TROUGH ROUNDS THE SOUTHERN PERIPHERY OF THE CIRCULATION OVER ALASKA AND DIGS TOWARDS THE BRITISH COLUMBIA COAST. THE HANDLING OF THE NEWLY DEVELOPED NORTHERN AND SOUTHERN STREAMS...WITH A REX BLOCK OVER THE WESTERN ROCKIES...IS THE SOURCE OF DISAGREEMENT AMONG THE MODELS FROM THURSDAY ONWARD. THERE ARE OTHER AFFECTS FOR TUESDAY AND WEDNESDAY BUT THE IMPACT ON SENSIBLE WEATHER IS ESSENTIALLY NIL DURING THOSE DAYS. HAVE NOT MADE MANY CHANGES TO THE FORECAST BEYOND THURSDAY GIVEN THE LACK OF CONTINUITY AMONG THE SOLUTIONS THUS FAR. THE 12Z/23 GFS CAME IN WITH QUITE A CHANGE...BRINGING A SHORTWAVE SOUTHWARD IN THE NORTHERN STREAM THURSDAY. THE 12/23 ECMWF HAS COME AROUND TO THIS TYPE OF EVOLUTION AS WELL...BUT IS A BIT SLOWER. THE IDEA OF A TROUGH RIDING DOWN THE RIDGE PORTION OF THE REX BLOCK IS REASONABLE...ESPECIALLY LOOKING AT THE CURRENT INTENSITY OF THE UPPER LOW WHICH SPAWNS THIS TROUGH. WILL NEED TO WATCH THE NEXT FEW RUNS BUT THE CHANCE OF ADDING OF POPS FOR THANKSGIVING DAY AND PERHAPS INTO FRIDAY IS INCREASING. && .MPX WATCHES/WARNINGS/ADVISORIES... MN...NONE. WI...NONE. && $$ TRH/HP/MDB mn AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN 306 PM CST SUN NOV 23 2008 .DISCUSSION... GOOD CONFIDENCE IN THE FORECAST THROUGH THE MIDDLE PART OF THE WEEK PRIOR TO THE UPCOMING HOLIDAY...BUT CONFIDENCE QUICKLY WANES FROM THANKSGIVING THROUGH THE END OF THE PERIOD. AFTERNOON GOES MOISTURE CHANNEL IMAGERY SHOWS FAIRLY PROGRESSIVE PATTERN IN PLACE AT THE CURRENT TIME BUT IT IS STARTING TO SHOW SIGNS OF AMPLIFYING. WEAK UPPER RIDGE HAS PASSED OVERHEAD WITH TROUGHING MOVING IN ON ITS HEELS. MAIN UPPER LOW CIRCULATION IS SAGGING SOUTHEASTWARD TOWARDS LAKES WINNIPEG AND MANITOBA WITH TROUGH AXIS EXTENDING SOUTHWESTWARD ACROSS THE LEE OF THE ROCKIES. A VORTICITY MAXIMA IS QUICKLY MOVING EAST-NORTHEAST TOWARDS CENTRAL MN AND NORTHERN WI THIS AFTERNOON EXHIBITED BY NARROW CHANNEL OF SHARP DRYING WORKING ALONG THE ND/SD BORDER. SFC ANALYSIS SHOWS WELL ORGANIZED SFC LOW OVER NORTHERN MANITOBA IN ASSOCIATION WITH THE CLOSED UPPER LOW. WARM FRONTAL BOUNDARY EXTENDS TO ITS SOUTHEAST ACROSS WESTERN/CENTRAL ONTARIO. A COOL FRONTAL BOUNDARY EXTENDS SOUTHWARD ALONG THE MN/DAKOTAS BORDER AND MEETS UP WITH A WEAK SFC LOW ACROSS EASTERN NEBRASKA. SHORTWAVE MOVING ACROSS SOUTHERN SOUTH DAKOTA AT 21Z WILL CONTINUE EAST-NORTHEAST THIS EVENING. UPPER JET ASSOCIATED WITH THE CLOSED LOW OVER MANITOBA APPEARS TO BE FURTHER WEST THAN EARLIER FORECASTS /AS IS THE LOW ITSELF/ RESULTING IN A DECREASED AFFECT FROM THE LEFT EXIT REGION. UPPER JET CURRENTLY INCREASING ACROSS IOWA SHOULD PROVIDE A BRIEF WINDOW OF LEFT FRONT QUAD ASCENT EARLY THIS EVENING BEFORE THAT SHIFTS TO THE EAST. NONETHELESS FORCING FOR ASCENT IS EXPECTED TO INCREASE AS THE SHORTWAVE TROUGH ENCOUNTERS THE SFC INVERTED TROUGH. CURRENT RADAR MOSAIC SHOWS BANDS OF MID LEVEL RETURNS WITH LITTLE SHOWING UP IN SFC OBS DUE TO LOW LEVEL DRY AIR THAT IS STILL BEING OVERCOME. THIS WILL BE THE CHALLENGE THROUGH THE EVENING AS DECENT FRONTOGENETICAL FORCING IN THE H7-H6 LAYER SAGS SOUTHEASTWARD ACROSS THE CWA. MUCH OF THE FORCING WILL GO TOWARDS SATURATION EARLY ON...WITH A LARGE DRY WEDGE STILL SHOWING UP ON RECENT AIRCRAFT SOUNDINGS FROM KMSP. DO EXPECT SNOW TO FALL TO THE SURFACE DURING THE EARLY EVENING ACROSS THE NORTH CENTRAL CWA BEFORE SHIFTING SOUTHEAST. DUE TO THE SPEED OF THE SYSTEM DURATION OF SNOW WILL BE SHORT LIVED...PROBABLY JUST A COUPLE HOURS...WHICH WILL LIMIT AMOUNTS. GIVEN THE NATURE OF THE FORCING BRIEF PERIODS OF MODERATE SNOW ARE EXPECTED AND A QUICK COUPLE TENTHS MAY BE RECEIVED. GENERALLY ABOUT A HALF INCH WILL BE POSSIBLE FROM NEW ULM TO THE TWIN CITIES TO RICE LAKE AND POINTS SOUTHEAST. SOME ISOLATED LOCATIONS MAY SEE AROUND AN INCH. AREAS ALONG THE IA BORDER MAY SEE LITTLE PRECIP WITH DRY AIR MOVING IN ALOFT AS SEEN ON LATEST WATER VAPOR IMAGERY. A BRIEF WINDOW OF RAIN/SNOW MIX MAY OCCUR BETWEEN NOW AND 01Z OR SO WITH WARM LOW LEVEL TEMPS BUT FORECAST SOUNDINGS SHOW WET BULB TEMPS TO BE BELOW ZERO THROUGH THE COLUMN ALLOWING EVAPORATIVE COOLING DURING THE TOP DOWN SATURATION TO YIELD JUST ABOUT ALL SNOW AT ONSET. THE WAVE WILL QUICKLY MOVE TO THE SOUTHEAST SO MOST OF THE PRECIP WILL END BY MIDNIGHT. SKIES MAY EVEN SCATTER OUT FOR A PERIOD PRIOR TO DAYBREAK AS SUBSIDENCE FILLS IN BEHIND THE WAVE. THE UPPER LOW CURRENTLY OVER CENTRAL/NORTHERN MANITOBA WILL CONTINUE TO DROP SOUTHEASTWARD ENTERING THE ARROWHEAD BY MIDDAY. CYCLONIC VORTICITY ADVECTION WILL INCREASE AHEAD OF ATTENDANT VORT MAX WHICH SWINGS FROM NORTHWEST TO SOUTHEAST ACROSS THE NORTHEASTERN TWO-THIRDS OR SO OF THE AREA. COLD ADVECTION WILL ALREADY BE UNDERWAY BUT A SECONDARY SHOT OF COLD AIR WILL ARRIVE WITH THE VORT MAX BY AFTERNOON. MOISTURE WILL BE FAIRLY MEAGER WITH PWATS AROUND A QUARTER INCH WITH A MODEST INCREASE AHEAD OF THE WAVE. WITH THE COLD ADVECTION /H85 TEMPS FALLING FROM -6 C TO -12 C DURING THE DAY/ THE DENDRITIC GROWTH ZONE LOWERS INTO THE LAYER OF HIGHER MOISTURE CONTENT AND ASCENT. EXPECT MOISTURE AND FORCING WILL BE SUFFICIENT FOR SNOW SHOWERS TO BE WRUNG OUT FROM MID/LATE MORNING THROUGH THE AFTERNOON. WITH THE COLD ADVECTION SNOW TO WATER RATIOS SHOULD BE ELEVATED AND FEEL THAT UP TO A HALF INCH MAY ACCUMULATE ACROSS THE EAST CENT WI COUNTIES AND A DUSTING TO A QUARTER INCH ACROSS THE FAR EAST CENT MN CWA. BY TUESDAY THE UPPER FLOW PATTERN WILL BE MUCH MORE AMPLIFIED THAN IT IS CURRENTLY WITH A DEEP TROUGH OVER THE LOWER GREAT LAKES AND A BROAD RIDGE OVER THE ROCKIES. SFC HIGH PRESSURE WILL BE OVERHEAD TUESDAY MORNING. THE PRESENCE OF THE HIGH COMBINED WITH THE COLD AIR BROUGHT BY THE PASSING FRONT WILL SUPPORT TUESDAY MORNING TEMPS IN THE TEENS TO AROUND 20 DEGREES. THE FLOW PATTERN WILL FAIRLY BLOCKED UP SO THE HIGH WILL TAKE ITS TIME CROSSING THE AREA INTO WEDNESDAY. WEDNESDAY CONTINUES TO LOOK QUIET ACROSS MUCH OF THE REGION. THINGS GET MORE COMPLEX INTO THANKSGIVING DAY AND THROUGH THE HOLIDAY WEEKEND. GFS AND ECMWF ARE AT ODDS WITH THE HANDLING OF THE FLOW COMING INTO THE WEST COAST OF NORTH AMERICA. THIS AFTERNOONS WATER VAPOR SHOWS A VERY SHARP AND DEEP LONGWAVE TROUGH STRETCHING FROM ALASKA SOUTHWARD ALONG AREAS BETWEEN 140W AND 145W AND EXTENDING AS FAR SOUTH AS 30N AND BEYOND. ANOTHER DEEP TROUGH IS RACING INTO THE NORTHERN PORTIONS OF THIS TROUGH FROM THE ALEUTIANS WITH ANOTHER WAVE ROUNDING THE BASE OF THE TROUGH NEAR 30N. BOTH THE GFS AND ECMWF CLOSE THE SOUTHERN PORTION OF THE TROUGH OFF BY MONDAY MORNING. THIS OCCURS AS THE ALEUTIAN TROUGH ROUNDS THE SOUTHERN PERIPHERY OF THE CIRCULATION OVER ALASKA AND DIGS TOWARDS THE BRITISH COLUMBIA COAST. THE HANDLING OF THE NEWLY DEVELOPED NORTHERN AND SOUTHERN STREAMS...WITH A REX BLOCK OVER THE WESTERN ROCKIES...IS THE SOURCE OF DISAGREEMENT AMONG THE MODELS FROM THURSDAY ONWARD. THERE ARE OTHER AFFECTS FOR TUESDAY AND WEDNESDAY BUT THE IMPACT ON SENSIBLE WEATHER IS ESSENTIALLY NIL DURING THOSE DAYS. HAVE NOT MADE MANY CHANGES TO THE FORECAST BEYOND THURSDAY GIVEN THE LACK OF CONTINUITY AMONG THE SOLUTIONS THUS FAR. THE 12Z/23 GFS CAME IN WITH QUITE A CHANGE...BRINGING A SHORTWAVE SOUTHWARD IN THE NORTHERN STREAM THURSDAY. THE 12/23 ECMWF HAS COME AROUND TO THIS TYPE OF EVOLUTION AS WELL...BUT IS A BIT SLOWER. THE IDEA OF A TROUGH RIDING DOWN THE RIDGE PORTION OF THE REX BLOCK IS REASONABLE...ESPECIALLY LOOKING AT THE CURRENT INTENSITY OF THE UPPER LOW WHICH SPAWNS THIS TROUGH. WILL NEED TO WATCH THE NEXT FEW RUNS BUT THE CHANCE OF ADDING OF POPS FOR THANKSGIVING DAY AND PERHAPS INTO FRIDAY IS INCREASING. ..MDB.. && .AVIATION.../18Z TAF ISSUANCE/ AN INVERTED SURFACE TROUGH WAS NOSING INTO SOUTHWEST/CENTRAL MN AT TAF ISSUANCE TIME. AN ARC OF STRATUS CLOUDS ON THE NORTHERN FRINGES OF THE TROUGH CONTINUES TO PLAGUE THE MAJORITY OF THE TAF SITES THIS AFTERNOON /WITH THE EXCEPTION OF KAXN AND KRWF/. NAM AND RUC 925MB RELATIVE HUMIDITY PROGS ARE DECENTLY ILLUSTRATING THE STRATUS DECK...AND INDICATE THAT MOST TAF SITES WILL EXPERIENCE A BREAK IN THE MVFR/IFR CIGS THIS AFTERNOON. THE MVFR CIGS MAY LINGER SLIGHTLY LONGER AT KSTC...BUT MOST SITES SHOULD BE EXPERIENCING VFR CONDITIONS BY ABOUT 20Z. LOW CLOUDS WILL MAKE A RETURN APPEARANCE THIS EVENING...AS THE DEFORMATION AXIS SETS UP FROM SOUTH CENTRAL MN NORTHEAST ACROSS WEST CENTRAL WI. A QUICK BURST OF LIGHT SNOW WILL BE POSSIBLE AT KRWF/KSTC TOWARD 00Z...AND AT KMSP/KRNH/KEAU BETWEEN 01Z-07Z. SUBSIDENCE BEHIND THIS FIRST SHORTWAVE WILL CAUSE THE CLOUDS TO SCATTER OUT DURING THE LATE EVENING AND OVERNIGHT HOURS...UNTIL THE PARENT LOW SINKS INTO NORTHERN MN ON MONDAY...AND BRINGS ANOTHER BATCH OF STRATUS CLOUDS WITH IT ON MONDAY AFTERNOON. GUSTY NORTHWEST WINDS AND SNOW SHOWERS WILL LIKELY BE INTRODUCED INTO THE TAF FORECAST AFTER 18Z MONDAY. && .MPX WATCHES/WARNINGS/ADVISORIES... MN...NONE. WI...NONE. && $$ MDB/LS mn AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN 1148 AM CST SUN NOV 23 2008 .UPDATE...FOR 18Z AVIATION DISCUSSION BELOW && .DISCUSSION.../ISSUED 330 AM CST SUN NOV 23 2008/ THE FORECAST CHALLENGE CENTERS ON THE SNOW POSSIBILITIES TONIGHT...MAINLY IN SOUTH CENTRAL AND SOUTHEAST MN. EARLY MORNING GOES SATELLITE CHANNELS AND OBS INDICATING LOW CLOUDS GRADUALLY ADVECTING NEWARD...WITH BACK-EDGE LIKELY TO CLEAR SOUTH CTRL MN IF NOT MUCH OF THE MN PORTION OF THE FORECAST AREA THROUGH THE MORNING. HIGH CLOUDS BEGINNING TO STREAM IN FROM THE WEST ORIGINATING FROM NEXT SYSTEM. WILL BE A WINDOW FOR SOME SUN IN SRN AND POSSIBLY ERN COMMUNITIES INTO THE EARLY AFTN. THIS SHOULD ALLOW FOR WARMER AND POSITIVE 925-850MB TEMPS TO BE MIXED DOWN...WITH HIGHS TODAY STILL FORECASTED TO BE IN THE LOWER 40S ACROSS SRN MN INTO WRN WI. THESE HIGHS AND OTHERS ACROSS THE AREA TODAY WILL BE SLIGHTLY WARMER THAN NORMAL AND OVERALL THE WARMEST DAY SINCE THE 14TH. INTEREST TURNS TO SYSTEM COMING OUT OF WY LATER THIS AFTN. THIS IS ANOTHER PACIFIC/ALBERTA-CLIPPER LIKE SYSTEM IN WNW FLOW. THE 06Z NAM HAS TRENDED FURTHER SOUTH THAN THE 00Z NAM...AND MORE IN LINE WITH THE SHORT RANGE FORECAST ENSEMBLE AND 00Z GFS. COMPARED TO THE FRI NIGHT SYSTEM WHICH DROPPED WIDESPREAD LIGHT SNOW ACROSS THE AREA...THIS ONE IS NOT AS DEEP IN THE H5 HEIGHTS AND TEMPS OR OVERALL PV ANOMALY. HOWEVER...THIS HAS MUCH BETTER MOISTURE TO WORK WITH AND WILL BE IN THE DEEPENING PHASE AS IT PASSES JUST SOUTH OF MN THIS EVE. THIS SYSTEM WILL PHASE OVER THE GREAT LAKES ON MON WITH A STRONGER ONE DIVING IN FROM THE NW. BUT AS IT BEGINS TO FEEL THE EFFECTS OF THAT UPSTREAM SYSTEM IT WILL DEEPEN THIS EVE...PLACING SRN MN IN DEFORMATION ZONE OF THIS SYSTEM. THIS CORRELATES WELL WITH A LEFT EXIT REGION OF A PREDICTED 95 KT JET. GREATEST PRESSURE ADVECTION ON THE ISENTROPIC SURFACES IS FOCUSED OVER SOUTH CTRL MN THIS EVE WHERE MOISTENING OCCURS FAIRLY RAPIDLY ACCORDING TO CROSS SECTIONS. MIXING RATIOS ON THE SURFACES OF UPGLIDE ARE 2 TO 2.5 G/KG WITH PRECIPITABLE WATERS NEAR 150 PERCENT OF NORMAL. THESE VALUES ARE GREATER THAN THE FRI NIGHT SYSTEM. DENDRITIC GROWTH LAYER IS FAIRLY DEEP /50-70MB/ AND OMEGA IS FOUND WITHIN THAT LAYER. PROFILE BELOW THIS QUICKLY WARMS HOWEVER AND SOME PARTIAL TO COMPLETE MELTING IS EXPECTED AT FIRST...ESPECIALLY GIVEN BOUNDARY LAYER TEMPS IN THE UPPER 30S EARLY THIS EVE ACROSS SRN MN. FRONTOGENESIS FOR FOCUS SNOW BANDS DEVELOPS AS EARLY AS THIS AFTN BUT CORRELATES WITH THE AFOREMENTIONED FORCING AND MOISTENING MAINLY DURING THE EVE IN SRN MN. SO POTENTIAL FOR BRIEF MODERATE SNOW DOES THEREFORE EXIST. BRIEF THOUGH IS THE KEY...AS SYSTEM IS ON THE MOVE FAIRLY QUICKLY EAST. A BAND OF ONE TO TWO INCHES APPEARS LIKELY TO SET-UP SOMEWHERE IN SOUTH CTRL MN...WITH A BROADER AREA OF UP TO ONE INCH ACROSS THE REMAINDER OF SRN AND ERN MN AND INTO WRN WI. MERGING SYSTEMS IN THE GREAT LAKES WILL OFFER BACK-SIDE COLD AIR ADVECTION BY MON AFTN WITH CLOUDS AND SOME ISOLD SNOW SHOWERS AND FLURRIES. H8 TEMPS NOT AS LOW AS IN RECENT DUMPS OF COLD AIR. SO TEMPS TO DROP TO SLIGHTLY BELOW NORMAL FOR MON INTO TUES AND THEN BACK TO SLIGHTLY ABOVE INTO THE HOLIDAY. FOR THE HOLIDAY TRAVELERS ON WEDS AND INTO THANKSGIVING...QUIET WEATHER LOOKS TO CONFIDENTLY PREVAIL IN THIS REGION. FRI THE PATTERN BECOMES MORE UNSETTLED...WITH THE WRN LAKES SURROUNDED BY SYSTEMS OF DECENT MAGNITUDE. ALL OF THEM THOUGH SEEM TO BE BLOCKING THE FLOW...LIKELY PREVENTING ANY MAJOR PRECIP ON FRI AND KEEPING TEMPS FROM CLIMBING OR DROPPING MUCH INTO NEXT WEEKEND. && .AVIATION.../18Z TAF ISSUANCE/ AN INVERTED SURFACE TROUGH WAS NOSING INTO SOUTHWEST/CENTRAL MN AT TAF ISSUANCE TIME. AN ARC OF STRATUS CLOUDS ON THE NORTHERN FRINGES OF THE TROUGH CONTINUES TO PLAGUE THE MAJORITY OF THE TAF SITES THIS AFTERNOON /WITH THE EXCEPTION OF KAXN AND KRWF/. NAM AND RUC 925MB RELATIVE HUMIDITY PROGS ARE DECENTLY ILLUSTRATING THE STRATUS DECK...AND INDICATE THAT MOST TAF SITES WILL EXPERIENCE A BREAK IN THE MVFR/IFR CIGS THIS AFTERNOON. THE MVFR CIGS MAY LINGER SLIGHTLY LONGER AT KSTC...BUT MOST SITES SHOULD BE EXPERIENCING VFR CONDITIONS BY ABOUT 20Z. LOW CLOUDS WILL MAKE A RETURN APPEARANCE THIS EVENING...AS THE DEFORMATION AXIS SETS UP FROM SOUTH CENTRAL MN NORTHEAST ACROSS WEST CENTRAL WI. A QUICK BURST OF LIGHT SNOW WILL BE POSSIBLE AT KRWF/KSTC TOWARD 00Z...AND AT KMSP/KRNH/KEAU BETWEEN 01Z-07Z. SUBSIDENCE BEHIND THIS FIRST SHORTWAVE WILL CAUSE THE CLOUDS TO SCATTER OUT DURING THE LATE EVENING AND OVERNIGHT HOURS...UNTIL THE PARENT LOW SINKS INTO NORTHERN MN ON MONDAY...AND BRINGS ANOTHER BATCH OF STRATUS CLOUDS WITH IT ON MONDAY AFTERNOON. GUSTY NORTHWEST WINDS AND SNOW SHOWERS WILL LIKELY BE INTRODUCED INTO THE TAF FORECAST AFTER 18Z MONDAY. && .MPX WATCHES/WARNINGS/ADVISORIES... MN...NONE. WI...NONE. && $$ LS/MTF mn AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN 607 PM CST SAT NOV 22 2008 .UPDATE... UPDATED FOR AVIATION DISCUSSION BELOW. && .DISCUSSION... /ISSUED 250 PM CST SAT NOV 22 2008/ THE MAIN FORECAST CONCERN IN THE SHORT TERM IS SNOWFALL POTENTIAL ON SUNDAY AND MONDAY...IN ASSOCIATION WITH A NORTHERN STREAM WAVE AND COLD FRONTAL PASSAGE. IN THE MEANTIME...LOW CLOUDS OVER THE SOUTHWESTERN CWA WILL LINGER THIS EVENING...WITH EXPANSION NORTH/EAST AS LOW LEVEL WINDS SHIFT TO THE SOUTHWEST AHEAD OF THE ADVANCING TROUGH. EXPECT THE STRATUS TO KEEP TEMPERATURES ELEVATED TONIGHT...WITH LOWS GENERALLY IN THE LOW/MID 20S. COOLER READINGS IN THE UPPER TEENS WILL BE POSSIBLE IN WEST CENTRAL WI...WHERE CLOUD COVER WILL BE LESS EXTENSIVE. AS THE CLOUDS EXPAND NORTH/EAST...SOME SCATTERING MAY OCCUR IN WEST/SOUTH CENTRAL MN. THIS WOULD PROVIDE THE OPPORTUNITY FOR FOG DEVELOPMENT. HAVE NOT INCLUDED IT IN THE GRIDS AT THIS POINT...AS ATTENDANT VISIBILITY REDUCTIONS ARE ONLY EXPECTED TO FALL INTO THE 3SM-5SM RANGE. THE TROUGH PASSES ACROSS THE AREA ON SUNDAY...WITH 290K UPGLIDE AND LOWERING CONDENSATIONAL PRESSURE DEFICITS PROGGED TO BE SITUATED OVER THE CWA. A PV ANOMALY ALSO COMES INTO PLAY ON SUNDAY NIGHT AND MONDAY MORNING...AND INTERACTS WITH INCREASING LOW LEVEL RH ACROSS CENTRAL MN AND WEST CENTRAL WI. SOUNDINGS INDICATE THE PRECIP TYPE ON SUNDAY AFTERNOON WOULD LIKELY BE A RAIN/SNOW MIX...WITH A TRANSITION TO SNOW ON SUNDAY EVENING. SNOWFALL AMOUNTS CIRCA ONE INCH OR LESS ARE EXPECTED THROUGH MONDAY. LIGHT SNOW SHOWERS WILL CONTINUE TO BE POSSIBLE ACROSS THE MN/WI BORDER INTO WEST CENTRAL WI THROUGH MONDAY EVENING...AS SHORTWAVE ENERGY ROUNDS THE WESTERN PERIPHERY OF THE GREAT LAKES LOW. A RATHER BENIGN WEATHER PATTERN IS IN STORE FROM TUESDAY THROUGH NEXT FRIDAY...AS A QUASI-OMEGA BLOCKING PATTERN DEVELOPS OVER THE CONUS. THIS WILL YIELD PREDOMINATELY DRY WEATHER AND SLIGHTLY ABOVE NORMAL TEMPERATURES FROM TUESDAY THROUGH THE THANKSGIVING HOLIDAY. THE PATTERN BREAKS DOWN TOWARD NEXT WEEKEND...BUT TIMING IS UNCERTAIN AT THIS POINT. HAVE THEREFORE STAYED THE COURSE WITH A DRY FORECAST THROUGH NEXT SATURDAY. && .AVIATION.../00Z TAF ISSUANCE/ LARGE AREA OF MVFR CIGS HAVE SPREAD FROM SW MN DURING THE DAY... ACROSS THE MSP METRO LATE AFTERNOON...AND WERE JUST ENTERING THE KRNH AREA EARLY THIS EVENING. WILL BRING THEM INTO KEAU LATER THIS EVENING. CIGS AND VSBYS HAVE ALSO LOWERED TO IFR IN FAR SW MN. LATEST RUC HAS BACKED OFF ON ERODING THE CLOUDS OVERNIGHT AND THIS LOOKS REASONABLE BASED ON CURRENT TRENDS. EROSION IS OCCURRING IN NERN NEBRASKA AND HAVE INDICATED SCATTERING OUT MID TO LATE MORNING. MID AND HIGH LEVEL CLOUDS WILL SPREAD IN SUNDAY AFTERNOON WITH NEXT SYSTEM. && .MPX WATCHES/WARNINGS/ADVISORIES... MN...NONE. WI...NONE. && $$ LS/TDK mn AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN 1149 PM CST FRI NOV 21 2008 .AVIATION... /06Z TAF ISSUANCE/ SURFACE LOW NOW IN CENTRAL SD AND MOVING A MORE E THAN SE. BEST PRESSURE FALLS ALONG THE SD/MN BORDER ATTM. MID LEVEL FRONTOGENESIS FROM CENTRAL THROUGH SOUTH CENTRAL MN WILL PUSH A BAND OF SNOW THROUGH KSTC AND KMSP DURING THE NEXT FEW HOURS WITH CEILINGS AND VSBYS DROPPING TO MVFR. ADDITIONAL SNOW WILL OCCUR AT KRWF AND KAXN THROUGH THE NIGHT WITH MVFR CONDITIONS. EXPECT THE FRONTOGENESIS TO WEAKEN OVER WEST CENTRAL WI EARLY SATURDAY. ALLOWED FOR SOME MVFR CONDITIONS IN SNOW AT KRNH BETWEEN 12Z AND 15Z WITH JUST FLURRIES BY THE TIME IT REACHES KEAU. IN THE WAKE OF THE LOW ON SATURDAY THE LOW LEVEL FLOW WILL BECOME MORE SOUTHERLY ALONG WITH WAA. KEPT MVFR CEILINGS FOR KRWF...KSTC AND KAXN WITH THE POTENTIAL FOR MVFR CEILINGS TO SPREAD/DEVELOP INTO KMSP AND KRNH DURING THE EVENING. && .DISCUSSION... /ISSUED 249 PM CST NOV 21 2008/ THE SHORTWAVE TROUGH ENTERING THE WESTERN DAKOTAS PER 20Z WATER VAPOR IMAGERY WILL BE THE FOCUS LOCALLY OVER THE NEXT 18 HOURS...AS IT CLOSES OFF AND SLIDES EAST/SOUTHEAST ACROSS SOUTHERN MN. ASSOCIATED 850-700MB OMEGA AND 2D FRONTOGENESIS BLOSSOM OVER THE SOUTHERN CWA AROUND 03Z...BUT EXPECT THE BULK OF THE SNOWFALL TO OCCUR BETWEEN 06Z AND 12Z WHEN THE LOW LEVEL SATURATION OCCURS. THE DYNAMICS...WHILE BRIEFLY IMPRESSIVE...ARE SOMEWHAT OUT OF SYNC WITH THE ARRIVAL OF THE LOW LEVEL MOISTURE...SO SNOWFALL ACCUMULATIONS OF ONE INCH OR LESS STILL APPEAR REASONABLE ALONG/SOUTH OF THE MN RIVER VALLEY. THIS IS SUPPORTED BY NAM/GFS/RUC PROGGED COBB OUTPUTS FOR KFRM AND KRWF. TEMPERATURES AT WESTERN CWA LOCATIONS WILL LIKELY REMAIN ELEVATED IN THE LOW 20S TONIGHT...ESPECIALLY CONSIDERING THE CLOUD COVER AND WARM AIR ADVECTION. EASTERN AREAS WILL HAVE THE POTENTIAL TO DIP INTO THE SINGLE DIGITS AGAIN...ESPECIALLY ACROSS WEST CENTRAL WI. LOW/MID CLOUDS WILL LINGER ON SATURDAY...BUT TEMPERATURES WILL MODERATE TO AROUND FREEZING. TEMPERATURES WILL WARM EVEN MORE ON SUNDAY AHEAD OF AN APPROACHING TROUGH...WITH HIGHS IN THE UPPER 30S AND LOWER 40S EXPECTED. THE RELATED COLD FRONT PASSES ACROSS THE CWA ON SUNDAY AFTERNOON/NIGHT...AS SHORTWAVE ENERGY ON THE WESTERN PERIPHERY OF AN AMPLIFYING EASTERN CONUS TROUGH STREAMS ACROSS MN AND WI. THE DEEPER MOISTURE WILL BE PRESENT ACROSS THE EASTERN CWA WHERE 30 POPS WERE PRESERVED...WHILE 20 POPS WERE ADEQUATE ELSEWHERE. THE EXTENDED PORTION OF THE FORECAST WILL FEATURE DRY WEATHER WITH NEAR TO ABOVE NORMAL TEMPERATURES THROUGH THE THANKSGIVING HOLIDAY...AS THE UPPER MIDWEST EXPERIENCES MID LEVEL RIDGING WHILE WEDGED BETWEEN CYCLONES OVER BOTH COASTS. && .MPX WATCHES/WARNINGS/ADVISORIES... MN...NONE. WI...NONE. && $$ RAH/LS mn AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TULSA OK 242 PM CST SAT NOV 22 2008 .DISCUSSION... TODAY/S FORECAST FOCUS IS ON PRECIPITATION CHANCES TOMORROW AND TOMORROW NIGHT ASSOCIATED WITH FRONTAL PASSAGE...AND MORE RAIN/THUNDERSTORM CHANCES FOR LATE NEXT WEEK AND INTO NEXT WEEKEND. STRONG SOUTHERLY FLOW HAS RETURNED TO THE AREA LEADING TO MUCH WARMER TEMPERATURES /IN MOST LOCALES/ AND HIGHER DEW POINTS THAN SEEN YESTERDAY. AREA OF LOW CLOUDINESS ACROSS SOUTHEAST OKLAHOMA HAS BEEN SLOW TO ERODE/PUSH TO THE EAST...WHICH HAS HELD HIGH TEMPERATURES DOWN FAIRLY SIGNIFICANTLY TODAY. THIS WILL HAVE AN EFFECT ON LOW TEMPERATURES IN THAT AREA TONIGHT. LOW CLOUDINESS HAS BEEN SHOWING A SLOW EAST TO NORTHEASTWARD MOVEMENT...ALTHOUGH TAMDAR SOUNDINGS ACROSS NORTH TEXAS SUGGEST THAT IT SHOULD NOT THIN MUCH THIS AFTERNOON. NAM12 AND RUC 850MB RH PROGS SHOW THAT SOME LOW LEVEL MOISTURE SHOULD LINGER THIS EVENING ACROSS SOUTHEAST OKLAHOMA SO HAVE CONTINUED A MENTION OF MOSTLY CLOUDY SKIES GENERALLY TO THE SOUTHEAST OF A LINE FROM HUGO TO POTEAU...ALTHOUGH WOULD NOT BE SURPRISED TO SEE AN HOUR OR TWO WITH MOSTLY CLEAR SKIES IN THIS AREA BEFORE A NEW BATCH OF LOW CLOUD COVER DEVELOPS LATER TONIGHT. AS FAR AS LOW TEMPERATURES GO...WILL MONITOR THE TEMPERATURE/SATELLITE TRENDS IN SOUTHEAST OKLAHOMA CLOSELY PRIOR TO ISSUING ANY FORECAST PRODUCTS AND AMEND FORECAST AS NECESSARY. WITH CLOUD COVER AND ADVECTION OF HIGHER DEW POINTS...EXPECT THAT LOW TEMPERATURES WILL BE IN THE UPPER 30S TO NEAR 40 ACROSS MUCH OF THE AREA SOUTH OF INTERSTATE 40. LATEST GUIDANCE CONTINUES TO POINT TOWARD SHOWERS ACROSS FAR EASTERN OKLAHOMA AND NORTHWEST ARKANSAS...ESPECIALLY LATE TOMORROW AND TOMORROW NIGHT...AS MOISTURE TRANSPORT MAXIMIZES AHEAD OF THE FRONT /PER 295K SURFACE/. CONTINUED WITH LIKELY POPS IN THIS REGION. HIGHS TOMORROW COULD BE A LITTLE TRICKY...WITH TIGHT GRADIENT IN CLOUD COVER EXPECTED FROM NORTHWEST TO SOUTHEAST. LARGELY WENT ABOVE GUIDANCE VALUES ALONG AND NORTHWEST OF INTERSTATE 44...WHERE LESS CLOUD COVER IS EXPECTED. DRIER AND SLIGHTLY COOLER AIR WILL MOVE INTO THE REGION ON THE HEELS OF THE FRONT...WITH FAR NORTHEAST OKLAHOMA AND NORTHWEST ARKANSAS FEELING THE MOST EFFECTS OF THE COOLER AIR. RIDGING BUILDS INTO THE CENTRAL CONUS FOR THE BEGINNING TO MIDDLE PART OF THE WEEK. GENERALLY WENT NEAR TO SLIGHTLY ABOVE THE MEX GUIDANCE VALUES THROUGH WEDNESDAY. 850 MB TEMPERATURES FROM THE 12Z ECMWF WOULD SUGGEST HIGHER TEMPERATURES THAN THAT FOR THE MIDDLE PART OF THE WEEK...BUT THIS RUN SEEMS ANOMALOUS WITH ITS PREVIOUS RUNS...AS WELL AS THE GFS AND GFS ENSEMBLE...SO HAVE DISCOUNTED THIS FOR NOW. MAJOR CHANGE TO THE EXTENDED FROM PREVIOUS FORECASTS WAS TO DELAY THE ONSET OF PRECIPITATION LATE IN THE WEEK ASSOCIATED WITH THE WARM ADVECTION IN ADVANCE OF THE LARGE TROUGH IN THE WESTERN CONUS. THE LAST FEW RUNS OF THE MID RANGE MODELS INDICATE THAT MUCH OF THE AREA SHOULD REMAIN RAIN FREE THROUGH AT LEAST THANKSGIVING AFTERNOON...WITH THE GREATEST CHANCES THAT EVENING AND OVERNIGHT. WITH NEAR 50 DEW POINTS POKING INTO SOUTHERN SECTIONS OF THE AREA...KEPT THE MENTION OF ISOLATED THUNDER IN ADVANCE OF THE SURFACE FRONT FOR THURSDAY NIGHT AND EARLY FRIDAY. PRECIPITATION SHOULD TAPER OFF FROM WEST TO EAST AS THE DRY SLOT MOVES IN...ALTHOUGH SMALL CHANCES FOR SHOWERS WILL REMAIN THROUGH EARLY SATURDAY ACROSS FAR NORTHERN OKLAHOMA AND NORTHWEST ARKANSAS WITH WRAP AROUND MOISTURE/ENERGY MOVING THROUGH THIS AREA. RAINFALL AMOUNTS COULD REACH A HALF INCH OR MORE...ESPECIALLY ACROSS FAR EASTERN OKLAHOMA AND INTO ARKANSAS. TEMPERATURES ON THE HEELS OF THIS SYSTEM LOOK TO BE COOLER THAN WITH TOMORROW/S FRONT...AND THE CURRENT FORECAST TEMPERATURES FOR SATURDAY AND SATURDAY NIGHT ARE BELOW THE MEX NUMBERS AT THIS TIME. && .PRELIMINARY POINT TEMPS/POPS... TUL 35 59 42 58 / 0 10 10 0 FSM 31 56 45 58 / 0 20 70 10 MLC 36 58 45 59 / 0 20 30 0 BVO 28 62 38 57 / 0 10 10 0 FYV 27 55 43 52 / 0 20 70 0 BYV 31 55 43 51 / 0 20 70 10 MKO 33 58 40 58 / 0 20 30 0 MIO 30 59 39 55 / 0 10 20 0 F10 36 58 41 59 / 0 10 20 0 HHW 39 55 54 64 / 0 30 30 10 && .TSA WATCHES/WARNINGS/ADVISORIES... OK...NONE. AR...NONE. && $$ SHORT TERM...18 LONG TERM....22 ok AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 656 AM EST SAT NOV 22 2008 .SYNOPSIS... A DEEP UPPER LEVEL TROUGH WILL DOMINATE OUR WEATHER THROUGH TODAY...KEEPING CENTRAL PENNSYLVANIA UNSEASONABLY COLD WITH LAKE EFFECT AND OROGRAPHICALLY ENHANCED SNOW SHOWERS. LOCALIZED HEAVY SNOW SQUALLS COULD PRODUCE BRIEF WHITEOUT CONDITIONS. HIGH PRESSURE WILL BUILD OVER THE REGION TONIGHT AND SUNDAY. THE NEXT STORM IS SLATED FOR THE MONDAY-TUESDAY TIME FRAME. POST STORM NORTHWESTERLY FLOW SHOULD RE-GENERATE LAKE EFFECT FOR THE REST OF NEXT WEEK. && .NEAR TERM /THROUGH TONIGHT/... DEEP COLD AIR TRAVERSING THE RELATIVELY WARM WATERS OF THE GREAT LAKES WILL CONTINUE TO PRODUCE PERIODS OF OROGRAPHIC SNOWS/SQUALLS THROUGH TODAY ACROSS THE ALLEGHENY PLATEAU...WITH A FEW EMBEDDED BANDS OF HEAVY SNOW SQUALLS. MORE PERSISTENT LAKE EFFECT SNOWS WILL IMPACT WARREN AND WESTERN MCKEAN COUNTIES. SOME INTERESTING FEATURES (I.E., NARROW SNOW SQUALL BANDS) ARE INFERRED BY THE 13KM RUC AND THE WRFARW AS FAR SE AS THE CENTRAL MTNS AT TIMES TODAY...INTO TONIGHT. THE MAIN AXIS OF BOUNDARY LAYER (SFC-1000M) THETA-E CONVERGENCE AND QPF STRETCHES ON A 300-310 DEG AXIS FROM NEAR KERI TO KFIG AND KUNV THIS AFTERNOON AND EVENING...BEFORE BACKING ABOUT 10-20 DEG SHIFTING THE BAND NE BETWEEN KUNV AND KIPT LATER TONIGHT. MODERATELY STRONG UVVEL AND DEEP MOISTURE COINCIDE NEAR...OR JUST UNDER THE PRIMARY DENDRITIC SNOW GROWTH THERMAL RIBBON OF -13 TO -18. THE 06Z NAM ACTUALLY INDICATES THE BEST FOCUS FOR THE SQUALLS NEAR KUNV FROM 00Z TO 05Z SUNDAY. SUBSIDENCE INVERSION QUICKLY DROPS TO BELOW 3 KFT AGL BEFORE 12Z SUNDAY WITH ANY WEAK OMEGA FALLING WELL BELOW THE MAIN DENDRITIC SNOW GROWTH REGION. WILL MAINTAIN THE PREVIOUS LAKE EFFECT SNOW WARNINGS AND WINTER WEATHER ADVISORIES ACROSS THE NW MTNS THROUGH 23Z TODAY...AND EVEN EXPAND THE ADVISORIES TO COVER NRN CENTRE COUNTY AND THE LIKELY...MORE PERSISTENT BANDS OF HEAVIER SNOW SHOWERS/SQUALLS. THE CENTRAL VALLEYS...NEAR KUNV WILL LIKELY SEE AN ADDITIONAL 1-2 INCHES OF WIND WHIPPED SNOW TODAY WITH HIGHLY LOCALIZED 3-4 INCH TOTALS POSSIBLE BY MIDNIGHT. MAX TEMPS TODAY...RANGING FROM THE L20S IN THE MW TO THE MID 30S IN THE LOWER SUSQ VALLEY WILL BE ABOUT 15F BELOW NORMAL. ADDING TO THIS WILL BE THE GUSTY WEST TO NORTHWEST WHICH WILL MAKE IT FEEL LIKE THE SINGLE DIGITS FOR MUCH OF THE DAY OVER THE MTNS...AND IN THE TEENS ELSEWHERE. && .SHORT TERM /SUNDAY/... AS WINDS LIGHTEN UP TONIGHT AND SKIES GO PARTLY CLOUDY IN MANY AREAS SE OF THE ALLEGHENY FRONT...THIS WILL SET US UP FOR PERHAPS THE COLDEST NIGHT OVER ALL THE AREA SO FAR THIS WINTER WITH THE FRESH SNOW PACK. LOWS EARLY SUNDAY WILL RANGE FROM 10 TO 15F ACROSS THE MTNS...AND 15 TO 20 DEGREES ELSEWHERE. SOME LOCATIONS ACROSS THE NORTH CENTRAL MTNS...WHERE BREAKS IN THE WANING STRATO CU DECK SHOULD BE MOST NUMEROUS...WILL SEE THE MERCURY DIVE INTO THE SINGLE DIGITS. && .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/... COLD WEATHER PATTERN TO CONTINUE THROUGH THE EXTENDED...WITH A POSSIBLE YET GRADUAL WARMING TREND FOR THE SECOND HALF OF THANKSGIVING WEEKEND. TEMPS WILL MODERATE A BIT SUNDAY INTO MONDAY AHEAD OF THE NEXT COLD FRONT...BUT WILL STILL REMAIN BELOW NORMAL. PRECIP MOVES IN FROM THE WEST MONDAY...REACHING EASTERN SECTIONS BY AFTERNOON. ATMOSPHERE MAY BE WARM ENOUGH AHEAD OF FRONT TO SUPPORT RAIN MIXED WITH SNOW FOR SEVERAL HOURS. SYSTEM STALLS TO THE EAST AS UPPER TROUGH AGAIN DEEPENS. N/NW FLOW WILL BRING LAKE EFFECT CLOUDS AND SNOW SHOWERS TO MAINLY THE WESTERN COUNTIES MON NIGHT INTO WED. AS CYCLONIC FLOW CONTINUES...LOW PRESSURE WILL INTENSIFY SOMEWHERE NEAR THE COAST. THERE STILL REMAINS SOME UNCERTAINTY OF JUST HOW THIS LOW WILL PLAY OUT...BUT REGARDLESS UNSETTLED WEATHER WILL START THE THANKSGIVING WEEKEND. TROUGH LIFTS TO THE NE LATE IN THE PERIOD WITH IMPROVEMENT IN STORE FOR THE WEEKEND. && .AVIATION /12Z SATURDAY THROUGH WEDNESDAY/... LITTLE CHANGE IN THINKING FROM THE PREVIOUS 06Z TAF PACKAGE AS BANDS OF LAKE EFFECT SNOW SHOWERS CONTINUE TO AFFECT SXNS OF WEST/CENTRAL PA. HIGH RESOLUTION NAM/WRF MDL INDICATES THE SNOW BAND CURRENTLY POSITIONED JUST NORTH/EAST OF AN ERI-UNV LINE WILL BE THE MAIN BAND TO CONTEND WITH TDY. THIS DATA ALSO SUGGESTS THAT THE AFOREMENTIONED SNOW BAND MAY EVEN EXTEND FURTHER SOUTH/EAST TWD IPT/MDT LATER TDY. WNWLY SFC WNDS 8-12KTS WILL INCREASE THIS AFTN TO 12-15KTS WITH OCNL 20-25KT GUSTS BEFORE DIMINISHING AFTER DARK. THE LOW LEVEL FLOW WILL BACK MORE TO THE WEST SOUTHWEST ON SUNDAY...EFFECTIVELY SHUTTING DOWN THE LAKE EFFECT SNOWS ACROSS WRN PA. VFR FLYING IS XPECTED TO LAST INTO SUN NGT/EARLY MON. THE NEXT STORM SYSTEM WILL ARRIVE MONDAY AFTN/EVE ACCOMPANIED BY RAIN/SNOW. THIS SYS IS FCST TO INTENSIFY AS IT MOVES NE INTO NEW ENGLAND TUE/WED...WITH PERIODS OF SNOW SHOWERS CONTINUING INTO MID WEEK. LOOK FOR MVFR AND IFR CONDS IN THE WEST/CENTRAL. && .CTP WATCHES/WARNINGS/ADVISORIES... LAKE EFFECT SNOW WARNING UNTIL 6 PM EST THIS AFTERNOON FOR PAZ004-005. WINTER WEATHER ADVISORY UNTIL 6 PM EST THIS AFTERNOON FOR PAZ006-010-011-017-018. && $$ SYNOPSIS...LAMBERT NEAR TERM...LAMBERT SHORT TERM...FITZGERALD/LAMBERT LONG TERM...BEACHLER/RXR AVIATION...STEINBUGL pa AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC 1013 PM EST SUN NOV 23 2008 .SYNOPSIS... A COLD FRONT WILL REACH OUR AREA FROM THE WEST LATE MONDAY WITH SOME BREEZY CONDITIONS MAINLY MONDAY NIGHT AND TUESDAY IN THE MOUNTAINS. HIGH PRESSURE WILL THEN BUILD ACROSS OUR REGION UNTIL THE END OF THE WEEK WHEN ANOTHER FRONT WILL APPROACH FROM THE WEST. && .NEAR TERM /THROUGH MONDAY/... LATEST SAT/RUC ANALYSIS AND 00Z RAOBS SHOW WEAK UPR RDG W/ AXIS FROM MI...THRU THE OHIO VALLEY...TO WRN GULF OF MEXICO. MEANWHILE...A POTENT S/W TROF PROGRESSES ACRS THE UPR MS VALLEY. IN THE LOW LVLS...A WEAK RDG AXIS WAS ANALYZED N-S ACRS THE TN VALLEY...W/ SOME DEEPER MOISTURE TO THE W OVR THE LWR MS VALLEY. DECENT H8-H7 WAA WAS OCCURRING ACRS MUCH OF THE SOUTHEAST STATES...W/ SOME SCT LGT RA SHWRS DEVELOPING INVOF MEMPHIS...TO PADUCAH..TOWARD NASHVILLE. THE LATEST MODELS ARE IN GENERAL AGREEMENT ON THE QPF FROM 00-06Z IN AFOREMENTIONED AREA (W/ THE EXCEPTION OF THE 00Z NAM WHICH SHOWED NONE OF THAT PRECIP.) WITH ALL THAT SAID...LTL CHANGE NEEDED TO POPS FOR THE PERIOD AROUND SUNRISE MONDAY MORNING. MID LVL CLOUDS ARE MOVING INTO THE WRN QUARTER OF THE FA ATTM...AND TEMP HAVE SLOWED DOWN OR STOPPED DECREASING UNDER THE CLOUDS. WITH STRONGER H8 WAA ACRS THE SW MTNS COMMENCING BY 06Z...AND CURRENT TEMPS STILL IN THE MID-UPR 30S...I DID MY BEST TO ADJUST TEMP TRENDS AND MIN TEMPS IN THAT AREA. ALSO...TOP-DOWN METHODOLOGY ON 00Z GUIDANCE RESULTED IN LESS WINTRY PRECIP W/ ONSET DURING THE PRE-DAWN HOURS. HOWEVER...A WINTRY MIX W/ SLEET AN/OR FZRA IS STILL POSSIBLE IN THE SWRN NC VALLEYS WHERE POCKETS OF COLDER AIR MAY STILL BE IN PLACE. QPF SHUD BE TOO LGT TO WARRANT ANY ADVISORY AT THIS TIME. HOWEVER...TRENDS WILL BE CLOSELY MONITORED. THE POTENTIAL FOR WINTRY PRECIP THIS MORNING WILL CONTINUE TO BE MENTIONED IN THE HWO. THE HEAVIER QPF WILL DEVELOP THROUGH THE DAY AS A COLD FRONT APPROACHES FROM THE WEST AND THE 850 MB JET INTENSIFIES THE WARM ADVECTION. THIS 50 KT JET WILL TRAVERSE THE NC MTNS DURING THE AFTERNOON HOURS MONDAY...BUT LIKELY PRODUCE LITTLE MORE THAN BREEZY TO WINDY CONDITIONS ACROSS THE RIDGE TOPS SINCE IT IS EMBEDDED IN WARM ADVECTION FLOW. IN SITU CAD IN PLACE WITH THE ONSET OF PRECIPITATION EAST OF THE BLUE RIDGE WILL KEEP MAXES BELOW MOS VALUES FOR MONDAY AFTERNOON THROUGHOUT THE PIEDMONT...PROVIDED ENOUGH MEASURABLE RAIN FALLS BY EARLY AFTERNOON. QPF AMOUNTS SHOULD RANGE FROM LESS THAN ONE QUARTER OF AN INCH ALONG THE EASTERN FRINGE TOMORROW TO AROUND AN INCH IN THE SOUTHWEST MOUNTAINS. && .SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY NIGHT/... AS OF 2 PM SUNDAY...A STRONG SHORTWAVE TROUGH WILL CROSS OUR AREA MONDAY NIGHT AS A CLOSED LOW MOVES JUST SOUTH OF THE GREAT LAKES. SLOWER FRONTAL TIMING IN BOTH THE NAM AND GFS WILL MEAN HIGHER POPS MONDAY EVENING ACROSS OUR AREA. HAVE GONE WITH A COMPROMISE OF LOW END CATEGORICAL. AFTER MIDNIGHT PRECIPITATION WILL END WITH FRONTAL PASSAGE IN THE LEE OF THE MOUNTAINS...WHILE A NORTHWEST FLOW PRECIPITATION EVENT BEGINS IN THE NC MOUNTAINS. FREEZING AND WET BULB ZERO LEVELS DROP TO THE VALLEY FLOORS BY DAYBREAK TUESDAY...BUT WILL LIFT SLIGHTLY DURING THE DAY WITH MEAGER WARMING. THE LATEST GUIDANCE HAS WARMED A FEW DEGREES ABOVE THE PREVIOUS FORECAST...BUT WITH SOME VACILLATION BY THE MODELS...FORECAST TEMPERATURES WILL ONLY BE RAISED A DEGREE OR TWO. UPSLOPE SNOW SHOWERS CONTINUE IN THE NC MOUNTAINS INTO TUE NIGHT...BUT THIS RUN OF THE WETTER AND PREFERRED GFS NOW DECREASE MOISTURE ALONG THE TN BORDER THROUGH THE NIGHT...ENDING THE EVENT BY WEDNESDAY MORNING. A BLEND OF GFS AND SREF QPF...ADJUSTED UP IN FAVORED AREAS...YIELDS SNOWFALL TOTALS OF UP TO FOUR INCHES...WITH THE HIGHEST AMOUNTS IN THE NORTHERN MOUNTAINS. A WINTER STORM WATCH WILL BE ISSUED FOR OUR NORTHERN NC MOUNTAINS FOR MONDAY NIGHT INTO WEDNESDAY MORNING. ADVISORY CRITERIA SNOW ARE EXPECTED SOUTH TO THE SMOKIES...AND ALONG THE NORTHERN BLUE RIDGE. WEDNESDAY AND WEDNESDAY NIGHT FEATURE A DRY SURFACE RIDGE OVER THE COASTAL SOUTHEAST. MOISTURE FROM A DEVELOPING GULF SYSTEM SPREAD NORTHEAST OVER THE TRAILING EDGE OF THE RIDGE...BUT LARGELY APPEARS TO REMAIN SOUTHWEST OF OUR AREA. NOT MUCH WARMING IS EXPECTED IN THE LEE WEDNESDAY AS HEIGHT RISES ARE OFFSET BY A WEAKENING DOWNSLOPE FLOW...HOWEVER MOUNTAIN LOCATIONS WILL SEE A GAIN OF A FEW DEGREES AS COLD ADVECTION ABATES. && .LONG TERM /THURSDAY THROUGH SUNDAY/... AS OF 215 PM SATURDAY...LEANED MORE TOWARD HPC THIS FCST. UPPER LOW FINALLY MOVES OFF E COAST THU WITH H5 RIDGE BUILDING OVER AREA WHILE SFC HI SLOWLY MOVES SE DURG DAY. THIS PUTS AREA IN MOIST SE FLOW AND MOISTURE WILL INCREASE FROM THE SW AHEAD OF A SFC WAVE THAT DEVELOPS OVER N GULF STATES THU NIGHT-FRI. EVEN THOUGH GFS TAKES SYSTEM FARTHER S THAN ECMWF...HPC USED A COMPROMISE THAT BRINGS THE SFC WAVE ACROSS N PART OF CWA SAT. WAA AHEAD OF THIS FEATURE WILL KEEP TEMPS MILD WITH SLIGHT CHANCE OF RAIN SHOWERS FRI. POPS INCREASE TO SOLID CHANCE FRI NIGHT. THERE IS ENOUGH UNCERTAINTY BETWEEN MODEL SOLUTIONS ATTM THAT I WILL NOT PAINT A SIGNIFICANT NW FLOW SNOW EVENT OVER MTNS FOR THE WEEKEND. LEANED TOWARD WARMER HPC TEMPS WHICH ARE STILL BELOW AVG BUT STILL ALLOW FOR SOME SNOW OVER HIGHER MTNS FRI NIGHT...THEN AGAIN SAT NIGHT. SYSTEM MOVES E OF AREA AND OFF THE COAST SUN WITH TEMPS COOLING A FEW DEG BEHIND IT. && .AVIATION /03Z MONDAY THROUGH FRIDAY/... AREA OF MAINLY MID LVL CLOUDS OVR MUCH OF THE SOUTHEAST STATES IN SWLY WAA FLOW CONTINUE TO SLOWLY ADVANCE WWD THIS EVE. METARS ACRS TN/AL/GA ARE GENERALLY REPORTING VFR CIGS B/T 4000-8000 FT ATTM. BASICALLY...ALL THE SHORT-RANGE GUIDANCE SHOW THIS MOISTURE GRADUALLY INFILTRATING ALL OUR TAF SITES BY ABT 13Z MONDAY...W/ VERY SLOW LOWERING OF CIGS. KAVL MAY HAVE SOME MVFR CIGS LATE MONDAY MORNING...OTHERWISE...CIGS SHUD STAY VFR UNTIL AT LEAST WHEN PRECIP BEGINS. PRECIP ONSET IN THE GUIDANCE HAS TRENDED LATER (AROUND 18Z) WITH LATEST RUNS. HOWEVER...STRONG WAA BEGINS BY 06Z...AND SOME LGT DZ/SHRA COULD DEVELOP AROUND DAYBREAK IF MOISTURE BECOMES DEEP ENUF. SFC TEMPS IN KAVL ARE FCST TO BE AOB FREEZING MONDAY MORNING. SO TRENDS IN TEMPS/PRECIP WILL CONT TO BE CLOSELY MONITORED IN THE CASE OF FZDZ/FZRA DEVELOPING THERE. TEMPS SHOULD RISE ABV FREEZING QUICKLY AFTER SUNRISE AT ALL SITES...SUCH THAT ALL PRECIP SHUD BE JUST RAIN BY 15Z. SWLY WNDS WILL INCREASE AHEAD OF AN APPROACHING COLD FRONT TO OUR WEST BY MIDDAY. OUTLOOK...A COLD FRONT WILL SWEEP ACROSS THE AREA MONDAY NIGHT...WITH PRECIPITATION ENDING EVERYWHERE BUT THE NC MOUNTAINS. GUSTY NORTHWEST WINDS WILL DEVELOP THROUGH TUESDAY...WITH SCATTERED SNOW SHOWERS AND MVFR CEILINGS BLOWING UP THE FRENCH BROAD VALLEY TO KAVL. THE NORTHWEST FLOW MOISTURE WILL CONTINUE THROUGH AT LEAST MID WEEK...WITH VERY DRY CONDITIONS OUTSIDE OF THE HIGHER TERRAIN. && .FIRE WEATHER... MIXING TO 900 MB ON SW FLOW TODAY SHOULD ALLOW DEWPOINTS TO DROP INTO THE MID TO UPPER TEENS THIS AFTERNOON. THIS WILL ONCE AGAIN YIELD SEVERAL HOURS OF 20 TO 25 PERCENT RH GIVEN THE WARMER MAX TEMPS THAN YESTERDAY. THE RED FLAG WARNING WILL BE MAINTAINED. && .GSP WATCHES/WARNINGS/ADVISORIES... GA...NONE. NC...WINTER STORM WATCH FROM MONDAY EVENING THROUGH WEDNESDAY MORNING FOR NCZ033-049-050. SC...NONE. && $$ SYNOPSIS...DEO NEAR TERM...ARK/HG SHORT TERM...JAT LONG TERM...RB AVIATION...ARK/HG FIRE WEATHER...HG sc AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NASHVILLE TN 914 PM CST SAT NOV 22 2008 .UPDATE...IT WAS CLOUDY OVER MOST OF THE MID STATE THIS EVENING, EXCEPT FOR SOUTHWESTERN COUNTIES, WHERE SKIES HAD CLEARED. 00Z OHX SOUNDING SHOWED PESKY MID LEVEL MOISTURE IN THE 750-650MB LAYER, AND LATEST RUC MODEL SEEMS TO HAVE THE BEST CLOUDY SOLUTION FOR THE REST OF THE NIGHT (OR AT LEAST THE ONE THAT`S CLOSEST TO CURRENT SATELLITE TREND). WILL UPDATE TO TWEAK OVERNIGHT CLOUD FORECAST AND KEEP IT MOSTLY CLOUDY OVER THE CUMBERLAND PLATEAU, WITH AT LEAST PARTIAL CLEARING ALL OTHER AREAS. WILL ALSO HAVE TO TWEAK TEMPERATURE FORECAST, INCLUDING RAISING TEMPERATURES EAST, WHERE CLOUDS ARE EXPECTED TO HANG TOUGH OVERNIGHT. && .PRELIMINARY POINT TEMPS/POPS... NASHVILLE 24 54 39 50 / 0 0 60 90 CLARKSVILLE 22 52 40 51 / 0 0 70 80 CROSSVILLE 22 48 32 44 / 0 0 30 90 COLUMBIA 22 55 39 52 / 0 0 60 90 LAWRENCEBURG 21 56 39 53 / 0 0 60 90 WAVERLY 21 53 40 52 / 0 0 70 80 && .OHX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ 19 tn AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CORPUS CHRISTI TX 1148 PM CST SAT NOV 22 2008 .DISCUSSION...UPDATE FOR AVIATION && .AVIATION...CONTINUED THE TREND OF LOWERING CEILINGS OVERNIGHT... ESPECIALLY 09 TO 15Z...WITH A MOIST SHALLOW WARM FRONT NUDGING NORTHWARD AT TIMES AS SHOWERS MIX THE AIR MASS AND MOVE QUICKLY TO THE NORTH ALONG THE COAST. BRIEF BREAKS IN THE OVERCAST AND AWAY FROM SHOWERS COULD DROP VISIBILITIES INTO MVFR AND BRIEFLY IFR DUE TO FOG/STRATUS. LOCALLY HEAVIER SHOWERS LATER TONIGHT AND EARLY SUNDAY MORNING WILL ALSO BRING DOWN CEILINGS AND BRIEFLY VISIBILITY FROM JUST EAST OF KINGSVILLE TO CRP AND TO VCT. && .PREV DISCUSSION... /ISSUED 947 PM CST SAT NOV 22 2008/ DISCUSSION...CLUSTER OF SHOWERS...SOME WITH BRIEF HEAVY RAIN... ARE MOVING INTO THE EAST PART OF CORPUS CHRISTI BAY AND TARGETING PORT ARANSAS. OTHER SHOWERS AHEAD OF THIS REGION HAVE MOVED INLAND AND GRADUALLY WEAKEN AS THEY REACH NORTHWARD TO AREAS FROM BEEVILLE TO ALICE. A PERSISTENT AREA OF LOW LEVEL CONVERGENCE EXISTS ALONG THE COASTAL BEND WITH RATHER SHALLOW INSTABILITY UP TO 650 MB. SURFACE BOUNDARY HAS MOVED INLAND PAST COUPLE HOURS. SUBTLE MOISTURE AND WARM AIR ADVECTION HAS BROUGHT PRECIPITABLE WATER VALUES UP TO 1.25 INCHES THIS EVENING. BOTH GFS AND NAM DEPICT WEAK SYNOPTIC SCALE LIFT TONIGHT INTO TOMORROW MORNING WITH A DISTURBANCE EMBEDDED IN SOUTHWEST FLOW THIS EVENING CROSSING SOUTH TEXAS AND A SOMEWHAT STRONGER WAVE ON SUNDAY. 00Z NAM APPEARS TO BE HANDLING THIS FIRST STRONGER WAVE OF SHOWERS WELL...AND THEN SUGGESTS ANOTHER AREA WILL DEVELOP LATE TONIGHT FROM THE SOUTH (ALONG THE COAST BUT ALSO LOCALLY INLAND) AND CONTINUE INTO SUNDAY MORNING BEFORE GETTING SHUNTING TO THE NORTHEAST. MODEL BUFR SOUNDINGS DEPICT THE BEST DEEPEST INSTABILITY SUNDAY MORNING FOR COASTAL AREAS WITH PRECIPITABLE WATER PEAKING TO AROUND 1.5 INCHES. LOCALIZED BRIEF HEAVY RAIN POSSIBLE FOR FAR EASTERN AREAS FROM NOW THROUGH MIDDAY SUNDAY...POSSIBLY THE CORPUS CHRISTI AREA AS WELL. MOST AMOUNTS SHOULD BE QUARTER INCH OR LESS WITH ISOLATED HALF TO THREE QUARTERS IN TRAINING CELLS. THE AIR MASS IS PROGGED TO STABILIZE AND DRY DURING SUNDAY AFTERNOON FROM WEST TO EAST. SOME SUNSHINE SHOULD ARRIVE FOR THE COASTAL BEND SUNDAY AFTERNOON AS WELL. FURTHER WEST THE SHOWER CHANCES DECREASE...HOWEVER THE POTENTIAL FOR LOW CLOUDS OR FOG IS PRESENT FOR THESE AREAS. LOW LEVEL SOUTH WINDS SHOULD INCREASE TONIGHT BUT STAY BELOW SCA. CURRENT FORECAST COVERS MOST OF THIS. 00Z NAM BRINGS THE NEXT COLD FRONT INTO THE AREA FROM THE NORTH DURING MONDAY EVENING. THIS SHOULD BRING A LINE OF SHOWERS WITH IT AND A BRIEF PERIOD OF OFFSHORE FLOW. PREV DISCUSSION... /ISSUED 300 PM CST SAT NOV 22 2008/ SHORT TERM (TONIGHT THROUGH SUNDAY NIGHT)...LOW TOPPED SHOWERS CONTINUE TO INCREASE IN COVERAGE ALONG A COASTAL FRONT EXTENDING ALONG THE DEEP S TX COAST TO NEAR RKP. MOISTURE POOLING ALONG THIS BOUNDARY WILL LEAD TO PWS INCREASING TO NEAR 1.5 INCHES OVERNIGHT. INSTABILITY AND MOISTURE CONVERGENCE WILL BE HIGH ENOUGH TO SUPPORT SCT SHRA ALONG THIS FEATURE...WHICH WILL WEAKEN AND SLOWLY MOVE NORTH ON SUN. A WEAK S/WV OVER NERN MEXICO SEEN ON RUC ANALYSIS AND GFS MAY ALSO PROVIDE SOME WEAK UPWARD MOTION LATE TONIGHT AND SUN BUT A MID LEVEL CAP SHOULD LIMIT MOST PRECIP TO SHRAS BELOW THE INVERSION. H85 FLOW WILL TURN FROM SSE TO A MORE SRLY DIRECTION BY EARLY SUN AND THIS SUGGESTS HIGHEST POPS WILL BE ACROSS AREAS NEAR/EAST OF I37 WITH CRP RIGHT ON THE EDGE OF THE MORE SIGNIFICANT SHOWERS. MAV POPS LOOK OK...EXCEPT THINK POPS SHOULD DROP OFF MORE RAPIDLY WEST OF I-37. HAVE CONFINED CHC POPS (30-50%) TO AREAS EAST OF HIGHWAY 281 WITH HIGHEST ALONG AND EAST OF A CRP TO BEEVILLE LINE BOTH TONIGHT AND SUN. AS THE H85 FLOW VEERS MORE SWRLY SUN AFTN AND EVENING THE MOISTURE AXIS WILL SHIFT MORE INTO THE MID AND UPR TEXAS COAST. MAV POPS LOOK TO HIGH GIVEN THE LOW LEVEL FLOW AND SHAVED ABOUT 20% OFF MAV VALUES SHOWING 20-30% ONLY FOR THE ERN 3RD (JUST CLIPPING CRP) SUN NIGHT. CLOUD COVER AND WAA PATTERN SUGGEST LOWS WILL NOT DROP OFF MUCH TONIGHT AND WE WILL LIKELY SEE LOTS OF STICKY LOW 60S FOR LOWS SUN NIGHT AS ONSHORE FLOW RESUMES. USED A BLEND OF MOS GUIDANCE FOR SUN`S HIGHS...W/ GENERALLY 70S INDICATED ACROSS THE AREA. LONG TERM (MONDAY THROUGH SATURDAY)...SOUTHWESTERLY BOUNDARY LAYER FLOW AHEAD OF AN APPROACHING COLD FRONT MONDAY WILL LEAD TO THE WARMEST TEMPERATURES OF THE PERIOD (LOWER 80S SOUTH/UPPER 70S NORTH). THE FRONT WILL PUSH THROUGH THE REGION MONDAY NIGHT WITH THE BEST MOISTURE CONVERGENCE/HIGHEST POPS EXPECTED ACROSS THE COASTAL COUNTIES. MOSTLY CLOUDY CONDITIONS ARE EXPECTED TUESDAY AS WEAK ISENTROPIC LIFT ENSUES DURING THE AFTERNOON HOURS. UPGLIDE STRENGTHENS TUESDAY NIGHT WITH LIGHT STRATIFORM RAIN EXPECTED TO DEVELOP OVER THE RIO GRANDE DURING THE OVERNIGHT HOURS...THEN GRADUALLY OVERSPREAD THE REGION WEDNESDAY AS THE JET STREAM SAGS SOUTHWARD OVER TEXAS. THE DEEPEST MOISTURE IS THEN PROGGED TO GET SHUNTED NORTHEAST OF THE AREA THURSDAY AS SOUTHWESTERLY FLOW REDEVELOPS IN THE BOUNDARY LAYER IN RESPONSE TO A MID-LEVEL TROUGH ENTERING THE TEXAS PANHANDLE. BOTH THE ECMWF AND THE GFS SHOW THE PARENT LOW PUSHING A COLD FRONT THROUGH SOUTH TEXAS TOWARDS THE END OF THE PERIOD...WITH THE GFS PUSHING THE FRONT THROUGH FRIDAY AND THE ECMWF PROGGING THE FROPA TO BE EARLY SATURDAY. EITHER WAY...SURFACE MOISTURE CONVERGENCE ALONG THE FRONT COMBINED WITH DYNAMICS ALOFT SHOULD BE SUFFICIENT FOR AT LEAST CHANCE POPS ALONG THE BOUNDARY. GIVEN THE MODEL TO MODEL AND RUN TO RUN DISCREPANCIES...BROAD BRUSHED CHANCE POPS EAST/SLIGHT CHANCE POPS WEST FOR THE FRIDAY THROUGH EARLY SATURDAY PERIOD. MUCH COOLER CONDITIONS WITH CLEARING SKIES ARE THEN EXPECTED BEHIND THE BOUNDARY FOR THE LAST TWO DAYS OF NOVEMBER. && .PRELIMINARY POINT TEMPS/POPS... CORPUS CHRISTI 59 77 64 81 59 / 40 30 10 10 20 VICTORIA 58 75 62 78 51 / 40 50 30 30 10 LAREDO 58 77 61 80 61 / 10 10 10 10 10 ALICE 58 78 63 82 58 / 20 20 10 10 20 ROCKPORT 60 75 66 78 59 / 50 40 30 20 20 COTULLA 55 73 60 80 54 / 10 10 10 10 10 KINGSVILLE 58 78 63 81 59 / 30 20 10 10 20 NAVY CORPUS 62 75 66 80 61 / 50 40 20 10 20 && .CRP WATCHES/WARNINGS/ADVISORIES... TX...NONE. GM...NONE. && $$ AT/15...SHORT TERM tx AREA FORECAST DISCUSSION...CORRECTED NATIONAL WEATHER SERVICE CORPUS CHRISTI TX 947 PM CST SAT NOV 22 2008 .DISCUSSION...CLUSTER OF SHOWERS...SOME WITH BRIEF HEAVY RAIN... ARE MOVING INTO THE EAST PART OF CORPUS CHRISTI BAY AND TARGETING PORT ARANSAS. OTHER SHOWERS AHEAD OF THIS REGION HAVE MOVED INLAND AND GRADUALLY WEAKEN AS THEY REACH NORTHWARD TO AREAS FROM BEEVILLE TO ALICE. A PERSISTENT AREA OF LOW LEVEL CONVERGENCE EXISTS ALONG THE COASTAL BEND WITH RATHER SHALLOW INSTABILITY UP TO 650 MB. SURFACE BOUNDARY HAS MOVED INLAND PAST COUPLE HOURS. SUBTLE MOISTURE AND WARM AIR ADVECTION HAS BROUGHT PRECIPITABLE WATER VALUES UP TO 1.25 INCHES THIS EVENING. BOTH GFS AND NAM DEPICT WEAK SYNOPTIC SCALE LIFT TONIGHT INTO TOMORROW MORNING WITH A DISTURBANCE EMBEDDED IN SOUTHWEST FLOW THIS EVENING CROSSING SOUTH TEXAS AND A SOMEWHAT STRONGER WAVE ON SUNDAY. 00Z NAM APPEARS TO BE HANDLING THIS FIRST STRONGER WAVE OF SHOWERS WELL...AND THEN SUGGESTS ANOTHER AREA WILL DEVELOP LATE TONIGHT FROM THE SOUTH (ALONG THE COAST BUT ALSO LOCALLY INLAND) AND CONTINUE INTO SUNDAY MORNING BEFORE GETTING SHUNTING TO THE NORTHEAST. MODEL BUFR SOUNDINGS DEPICT THE BEST DEEPEST INSTABILITY SUNDAY MORNING FOR COASTAL AREAS WITH PRECIPITABLE WATER PEAKING TO AROUND 1.5 INCHES. LOCALIZED BRIEF HEAVY RAIN POSSIBLE FOR FAR EASTERN AREAS FROM NOW THROUGH MIDDAY SUNDAY...POSSIBLY THE CORPUS CHRISTI AREA AS WELL. MOST AMOUNTS SHOULD BE QUARTER INCH OR LESS WITH ISOLATED HALF TO THREE QUARTERS IN TRAINING CELLS. THE AIR MASS IS PROGGED TO STABILIZE AND DRY DURING SUNDAY AFTERNOON FROM WEST TO EAST. SOME SUNSHINE SHOULD ARRIVE FOR THE COASTAL BEND SUNDAY AFTERNOON AS WELL. FURTHER WEST THE SHOWER CHANCES DECREASE...HOWEVER THE POTENTIAL FOR LOW CLOUDS OR FOG IS PRESENT FOR THESE AREAS. LOW LEVEL SOUTH WINDS SHOULD INCREASE TONIGHT BUT STAY BELOW SCA. CURRENT FORECAST COVERS MOST OF THIS. 00Z NAM BRINGS THE NEXT COLD FRONT INTO THE AREA FROM THE NORTH DURING MONDAY EVENING. THIS SHOULD BRING A LINE OF SHOWERS WITH IT AND A BRIEF PERIOD OF OFFSHORE FLOW. && .PREV DISCUSSION... /ISSUED 535 PM CST SAT NOV 22 2008/ DISCUSSION...SEE AVIATION DISCUSSION BELOW. AVIATION...THE VFR CONDITIONS THIS EVENING WILL BE BRIEF AS CIGS LOWER THROUGH THE NIGHT DUE TO INCREASING LOW LEVEL MOISTURE/PATCHY -RA/DZ AND BR. AM EXPECTING A MIX OF IFR/MVFR CONDITIONS THROUGH LATE SUNDAY MORNING THEN CIGS BEGIN TO LIFT TO AROUND 35HFT BY EARLY AFTERNOON. PREV DISCUSSION... /ISSUED 300 PM CST SAT NOV 22 2008/ SHORT TERM (TONIGHT THROUGH SUNDAY NIGHT)...LOW TOPPED SHOWERS CONTINUE TO INCREASE IN COVERAGE ALONG A COASTAL FRONT EXTENDING ALONG THE DEEP S TX COAST TO NEAR RKP. MOISTURE POOLING ALONG THIS BOUNDARY WILL LEAD TO PWS INCREASING TO NEAR 1.5 INCHES OVERNIGHT. INSTABILITY AND MOISTURE CONVERGENCE WILL BE HIGH ENOUGH TO SUPPORT SCT SHRA ALONG THIS FEATURE...WHICH WILL WEAKEN AND SLOWLY MOVE NORTH ON SUN. A WEAK S/WV OVER NERN MEXICO SEEN ON RUC ANALYSIS AND GFS MAY ALSO PROVIDE SOME WEAK UPWARD MOTION LATE TONIGHT AND SUN BUT A MID LEVEL CAP SHOULD LIMIT MOST PRECIP TO SHRAS BELOW THE INVERSION. H85 FLOW WILL TURN FROM SSE TO A MORE SRLY DIRECTION BY EARLY SUN AND THIS SUGGESTS HIGHEST POPS WILL BE ACROSS AREAS NEAR/EAST OF I37 WITH CRP RIGHT ON THE EDGE OF THE MORE SIGNIFICANT SHOWERS. MAV POPS LOOK OK...EXCEPT THINK POPS SHOULD DROP OFF MORE RAPIDLY WEST OF I-37. HAVE CONFINED CHC POPS (30-50%) TO AREAS EAST OF HIGHWAY 281 WITH HIGHEST ALONG AND EAST OF A CRP TO BEEVILLE LINE BOTH TONIGHT AND SUN. AS THE H85 FLOW VEERS MORE SWRLY SUN AFTN AND EVENING THE MOISTURE AXIS WILL SHIFT MORE INTO THE MID AND UPR TEXAS COAST. MAV POPS LOOK TO HIGH GIVEN THE LOW LEVEL FLOW AND SHAVED ABOUT 20% OFF MAV VALUES SHOWING 20-30% ONLY FOR THE ERN 3RD (JUST CLIPPING CRP) SUN NIGHT. CLOUD COVER AND WAA PATTERN SUGGEST LOWS WILL NOT DROP OFF MUCH TONIGHT AND WE WILL LIKELY SEE LOTS OF STICKY LOW 60S FOR LOWS SUN NIGHT AS ONSHORE FLOW RESUMES. USED A BLEND OF MOS GUIDANCE FOR SUN`S HIGHS...W/ GENERALLY 70S INDICATED ACROSS THE AREA. LONG TERM (MONDAY THROUGH SATURDAY)...SOUTHWESTERLY BOUNDARY LAYER FLOW AHEAD OF AN APPROACHING COLD FRONT MONDAY WILL LEAD TO THE WARMEST TEMPERATURES OF THE PERIOD (LOWER 80S SOUTH/UPPER 70S NORTH). THE FRONT WILL PUSH THROUGH THE REGION MONDAY NIGHT WITH THE BEST MOISTURE CONVERGENCE/HIGHEST POPS EXPECTED ACROSS THE COASTAL COUNTIES. MOSTLY CLOUDY CONDITIONS ARE EXPECTED TUESDAY AS WEAK ISENTROPIC LIFT ENSUES DURING THE AFTERNOON HOURS. UPGLIDE STRENGTHENS TUESDAY NIGHT WITH LIGHT STRATIFORM RAIN EXPECTED TO DEVELOP OVER THE RIO GRANDE DURING THE OVERNIGHT HOURS...THEN GRADUALLY OVERSPREAD THE REGION WEDNESDAY AS THE JET STREAM SAGS SOUTHWARD OVER TEXAS. THE DEEPEST MOISTURE IS THEN PROGGED TO GET SHUNTED NORTHEAST OF THE AREA THURSDAY AS SOUTHWESTERLY FLOW REDEVELOPS IN THE BOUNDARY LAYER IN RESPONSE TO A MID-LEVEL TROUGH ENTERING THE TEXAS PANHANDLE. BOTH THE ECMWF AND THE GFS SHOW THE PARENT LOW PUSHING A COLD FRONT THROUGH SOUTH TEXAS TOWARDS THE END OF THE PERIOD...WITH THE GFS PUSHING THE FRONT THROUGH FRIDAY AND THE ECMWF PROGGING THE FROPA TO BE EARLY SATURDAY. EITHER WAY...SURFACE MOISTURE CONVERGENCE ALONG THE FRONT COMBINED WITH DYNAMICS ALOFT SHOULD BE SUFFICIENT FOR AT LEAST CHANCE POPS ALONG THE BOUNDARY. GIVEN THE MODEL TO MODEL AND RUN TO RUN DISCREPANCIES...BROAD BRUSHED CHANCE POPS EAST/SLIGHT CHANCE POPS WEST FOR THE FRIDAY THROUGH EARLY SATURDAY PERIOD. MUCH COOLER CONDITIONS WITH CLEARING SKIES ARE THEN EXPECTED BEHIND THE BOUNDARY FOR THE LAST TWO DAYS OF NOVEMBER. && .PRELIMINARY POINT TEMPS/POPS... CORPUS CHRISTI 59 77 64 81 59 / 40 30 10 10 20 VICTORIA 58 75 62 78 51 / 40 50 30 30 10 LAREDO 58 77 61 80 61 / 10 10 10 10 10 ALICE 58 78 63 82 58 / 20 20 10 10 20 ROCKPORT 60 75 66 78 59 / 50 40 30 20 20 COTULLA 55 73 60 80 54 / 10 10 10 10 10 KINGSVILLE 58 78 63 81 59 / 30 20 10 10 20 NAVY CORPUS 62 75 66 80 61 / 50 40 20 10 20 && .CRP WATCHES/WARNINGS/ADVISORIES... TX...NONE. GM...NONE. && $$ AT/15 tx AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CORPUS CHRISTI TX 535 PM CST SAT NOV 22 2008 .DISCUSSION...SEE AVIATION DISCUSSION BELOW. && .AVIATION...THE VFR CONDITIONS THIS EVENING WILL BE BRIEF AS CIGS LOWER THROUGH THE NIGHT DUE TO INCREASING LOW LEVEL MOISTURE/PATCHY -RA/DZ AND BR. AM EXPECTING A MIX OF IFR/MVFR CONDITIONS THROUGH LATE SUNDAY MORNING THEN CIGS BEGIN TO LIFT TO AROUND 35HFT BY EARLY AFTERNOON. && .PREV DISCUSSION... /ISSUED 300 PM CST SAT NOV 22 2008/ SHORT TERM (TONIGHT THROUGH SUNDAY NIGHT)...LOW TOPPED SHOWERS CONTINUE TO INCREASE IN COVERAGE ALONG A COASTAL FRONT EXTENDING ALONG THE DEEP S TX COAST TO NEAR RKP. MOISTURE POOLING ALONG THIS BOUNDARY WILL LEAD TO PWS INCREASING TO NEAR 1.5 INCHES OVERNIGHT. INSTABILITY AND MOISTURE CONVERGENCE WILL BE HIGH ENOUGH TO SUPPORT SCT SHRA ALONG THIS FEATURE...WHICH WILL WEAKEN AND SLOWLY MOVE NORTH ON SUN. A WEAK S/WV OVER NERN MEXICO SEEN ON RUC ANALYSIS AND GFS MAY ALSO PROVIDE SOME WEAK UPWARD MOTION LATE TONIGHT AND SUN BUT A MID LEVEL CAP SHOULD LIMIT MOST PRECIP TO SHRAS BELOW THE INVERSION. H85 FLOW WILL TURN FROM SSE TO A MORE SRLY DIRECTION BY EARLY SUN AND THIS SUGGESTS HIGHEST POPS WILL BE ACROSS AREAS NEAR/EAST OF I37 WITH CRP RIGHT ON THE EDGE OF THE MORE SIGNIFICANT SHOWERS. MAV POPS LOOK OK...EXCEPT THINK POPS SHOULD DROP OFF MORE RAPIDLY WEST OF I-37. HAVE CONFINED CHC POPS (30-50%) TO AREAS EAST OF HIGHWAY 281 WITH HIGHEST ALONG AND EAST OF A CRP TO BEEVILLE LINE BOTH TONIGHT AND SUN. AS THE H85 FLOW VEERS MORE SWRLY SUN AFTN AND EVENING THE MOISTURE AXIS WILL SHIFT MORE INTO THE MID AND UPR TEXAS COAST. MAV POPS LOOK TO HIGH GIVEN THE LOW LEVEL FLOW AND SHAVED ABOUT 20% OFF MAV VALUES SHOWING 20-30% ONLY FOR THE ERN 3RD (JUST CLIPPING CRP) SUN NIGHT. CLOUD COVER AND WAA PATTERN SUGGEST LOWS WILL NOT DROP OFF MUCH TONIGHT AND WE WILL LIKELY SEE LOTS OF STICKY LOW 60S FOR LOWS SUN NIGHT AS ONSHORE FLOW RESUMES. USED A BLEND OF MOS GUIDANCE FOR SUN`S HIGHS...W/ GENERALLY 70S INDICATED ACROSS THE AREA. LONG TERM (MONDAY THROUGH SATURDAY)...SOUTHWESTERLY BOUNDARY LAYER FLOW AHEAD OF AN APPROACHING COLD FRONT MONDAY WILL LEAD TO THE WARMEST TEMPERATURES OF THE PERIOD (LOWER 80S SOUTH/UPPER 70S NORTH). THE FRONT WILL PUSH THROUGH THE REGION MONDAY NIGHT WITH THE BEST MOISTURE CONVERGENCE/HIGHEST POPS EXPECTED ACROSS THE COASTAL COUNTIES. MOSTLY CLOUDY CONDITIONS ARE EXPECTED TUESDAY AS WEAK ISENTROPIC LIFT ENSUES DURING THE AFTERNOON HOURS. UPGLIDE STRENGTHENS TUESDAY NIGHT WITH LIGHT STRATIFORM RAIN EXPECTED TO DEVELOP OVER THE RIO GRANDE DURING THE OVERNIGHT HOURS...THEN GRADUALLY OVERSPREAD THE REGION WEDNESDAY AS THE JET STREAM SAGS SOUTHWARD OVER TEXAS. THE DEEPEST MOISTURE IS THEN PROGGED TO GET SHUNTED NORTHEAST OF THE AREA THURSDAY AS SOUTHWESTERLY FLOW REDEVELOPS IN THE BOUNDARY LAYER IN RESPONSE TO A MID-LEVEL TROUGH ENTERING THE TEXAS PANHANDLE. BOTH THE ECMWF AND THE GFS SHOW THE PARENT LOW PUSHING A COLD FRONT THROUGH SOUTH TEXAS TOWARDS THE END OF THE PERIOD...WITH THE GFS PUSHING THE FRONT THROUGH FRIDAY AND THE ECMWF PROGGING THE FROPA TO BE EARLY SATURDAY. EITHER WAY...SURFACE MOISTURE CONVERGENCE ALONG THE FRONT COMBINED WITH DYNAMICS ALOFT SHOULD BE SUFFICIENT FOR AT LEAST CHANCE POPS ALONG THE BOUNDARY. GIVEN THE MODEL TO MODEL AND RUN TO RUN DISCREPANCIES...BROAD BRUSHED CHANCE POPS EAST/SLIGHT CHANCE POPS WEST FOR THE FRIDAY THROUGH EARLY SATURDAY PERIOD. MUCH COOLER CONDITIONS WITH CLEARING SKIES ARE THEN EXPECTED BEHIND THE BOUNDARY FOR THE LAST TWO DAYS OF NOVEMBER. && .PRELIMINARY POINT TEMPS/POPS... CORPUS CHRISTI 59 77 64 81 59 / 40 30 10 10 20 VICTORIA 58 75 62 78 51 / 40 50 30 30 10 LAREDO 58 77 61 80 61 / 10 10 10 10 10 ALICE 58 78 63 82 58 / 20 20 10 10 20 ROCKPORT 60 75 66 78 59 / 50 40 30 20 20 COTULLA 55 73 60 80 54 / 10 10 10 10 10 KINGSVILLE 58 78 63 81 59 / 30 20 10 10 20 NAVY CORPUS 62 75 66 80 61 / 50 40 20 10 20 && .CRP WATCHES/WARNINGS/ADVISORIES... TX...NONE. GM...NONE. && $$ TE/81...AVIATION AT/15...SHORT TERM tx AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CORPUS CHRISTI TX 300 PM CST SAT NOV 22 2008 .SHORT TERM (TONIGHT THROUGH SUNDAY NIGHT)...LOW TOPPED SHOWERS CONTINUE TO INCREASE IN COVERAGE ALONG A COASTAL FRONT EXTENDING ALONG THE DEEP S TX COAST TO NEAR RKP. MOISTURE POOLING ALONG THIS BOUNDARY WILL LEAD TO PWS INCREASING TO NEAR 1.5 INCHES OVERNIGHT. INSTABILITY AND MOISTURE CONVERGENCE WILL BE HIGH ENOUGH TO SUPPORT SCT SHRA ALONG THIS FEATURE...WHICH WILL WEAKEN AND SLOWLY MOVE NORTH ON SUN. A WEAK S/WV OVER NERN MEXICO SEEN ON RUC ANALYSIS AND GFS MAY ALSO PROVIDE SOME WEAK UPWARD MOTION LATE TONIGHT AND SUN BUT A MID LEVEL CAP SHOULD LIMIT MOST PRECIP TO SHRAS BELOW THE INVERSION. H85 FLOW WILL TURN FROM SSE TO A MORE SRLY DIRECTION BY EARLY SUN AND THIS SUGGESTS HIGHEST POPS WILL BE ACROSS AREAS NEAR/EAST OF I37 WITH CRP RIGHT ON THE EDGE OF THE MORE SIGNIFICANT SHOWERS. MAV POPS LOOK OK...EXCEPT THINK POPS SHOULD DROP OFF MORE RAPIDLY WEST OF I-37. HAVE CONFINED CHC POPS (30-50%) TO AREAS EAST OF HIGHWAY 281 WITH HIGHEST ALONG AND EAST OF A CRP TO BEEVILLE LINE BOTH TONIGHT AND SUN. AS THE H85 FLOW VEERS MORE SWRLY SUN AFTN AND EVENING THE MOISTURE AXIS WILL SHIFT MORE INTO THE MID AND UPR TEXAS COAST. MAV POPS LOOK TO HIGH GIVEN THE LOW LEVEL FLOW AND SHAVED ABOUT 20% OFF MAV VALUES SHOWING 20-30% ONLY FOR THE ERN 3RD (JUST CLIPPING CRP) SUN NIGHT. CLOUD COVER AND WAA PATTERN SUGGEST LOWS WILL NOT DROP OFF MUCH TONIGHT AND WE WILL LIKELY SEE LOTS OF STICKY LOW 60S FOR LOWS SUN NIGHT AS ONSHORE FLOW RESUMES. USED A BLEND OF MOS GUIDANCE FOR SUN`S HIGHS...W/ GENERALLY 70S INDICATED ACROSS THE AREA. && .LONG TERM (MONDAY THROUGH SATURDAY)...SOUTHWESTERLY BOUNDARY LAYER FLOW AHEAD OF AN APPROACHING COLD FRONT MONDAY WILL LEAD TO THE WARMEST TEMPERATURES OF THE PERIOD (LOWER 80S SOUTH/UPPER 70S NORTH). THE FRONT WILL PUSH THROUGH THE REGION MONDAY NIGHT WITH THE BEST MOISTURE CONVERGENCE/HIGHEST POPS EXPECTED ACROSS THE COASTAL COUNTIES. MOSTLY CLOUDY CONDITIONS ARE EXPECTED TUESDAY AS WEAK ISENTROPIC LIFT ENSUES DURING THE AFTERNOON HOURS. UPGLIDE STRENGTHENS TUESDAY NIGHT WITH LIGHT STRATIFORM RAIN EXPECTED TO DEVELOP OVER THE RIO GRANDE DURING THE OVERNIGHT HOURS...THEN GRADUALLY OVERSPREAD THE REGION WEDNESDAY AS THE JET STREAM SAGS SOUTHWARD OVER TEXAS. THE DEEPEST MOISTURE IS THEN PROGGED TO GET SHUNTED NORTHEAST OF THE AREA THURSDAY AS SOUTHWESTERLY FLOW REDEVELOPS IN THE BOUNDARY LAYER IN RESPONSE TO A MID-LEVEL TROUGH ENTERING THE TEXAS PANHANDLE. BOTH THE ECMWF AND THE GFS SHOW THE PARENT LOW PUSHING A COLD FRONT THROUGH SOUTH TEXAS TOWARDS THE END OF THE PERIOD...WITH THE GFS PUSHING THE FRONT THROUGH FRIDAY AND THE ECMWF PROGGING THE FROPA TO BE EARLY SATURDAY. EITHER WAY...SURFACE MOISTURE CONVERGENCE ALONG THE FRONT COMBINED WITH DYNAMICS ALOFT SHOULD BE SUFFICIENT FOR AT LEAST CHANCE POPS ALONG THE BOUNDARY. GIVEN THE MODEL TO MODEL AND RUN TO RUN DISCREPANCIES...BROAD BRUSHED CHANCE POPS EAST/SLIGHT CHANCE POPS WEST FOR THE FRIDAY THROUGH EARLY SATURDAY PERIOD. MUCH COOLER CONDITIONS WITH CLEARING SKIES ARE THEN EXPECTED BEHIND THE BOUNDARY FOR THE LAST TWO DAYS OF NOVEMBER. && .PRELIMINARY POINT TEMPS/POPS... CORPUS CHRISTI 59 77 64 81 59 / 40 30 10 10 20 VICTORIA 58 75 62 78 51 / 40 50 30 30 10 LAREDO 58 77 61 80 61 / 10 10 10 10 10 ALICE 58 78 63 82 58 / 20 20 10 10 20 ROCKPORT 60 75 66 78 59 / 50 40 30 20 20 COTULLA 55 73 60 80 54 / 10 10 10 10 10 KINGSVILLE 58 78 63 81 59 / 30 20 10 10 20 NAVY CORPUS 62 75 66 80 61 / 50 40 20 10 20 && .CRP WATCHES/WARNINGS/ADVISORIES... TX...NONE. GM...NONE. && $$ MJG...SHORT TERM TM...LONG TERM tx AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LA CROSSE WI 835 PM CST SUN NOV 23 2008 .UPDATE... GOING FORECAST SEEMS LARGELY ON TRACK IN REGARDS TO OVERNIGHT SNOW POTENTIAL...THOUGH MAY NEED SOME REDUCTIONS IN SNOW CHANCES OVERALL IF VISIBILITIES WITH ENHANCED REFLECTIVITY BAND OVER SCNTL MN DON/T DROP ANY MORE THAN CURRENT 3-5SM IN LIGHT SNOW /FLURRIES/. CURRENTLY...SHORTWAVE ENERGY STRUNG OUT FROM WRN IA INTO SRN NEB STREAKING EAST WHILE MORE POTENT CIRCULATION CROSSES EASTERN MANITOBA. LARGE SCALE ASCENT INCREASING THIS HOUR AS THESE SHORTWAVES BEGIN TO CONSOLIDATE IN THE NEXT 12 HOUR WITH MAIN TROUGH AXIS PASSING THROUGH FORECAST AREA OVERNIGHT. CURRENT REFLECTIVITIES ON KARX/KMPX RADAR FROM SERN TC METRO DOWN THE I-35 CORRIDOR ABOUT 50-75MI BEHIND SURFACE COLD FRONT WHICH IS APPROACHING WINONA/DECORAH LINE...WITH FORCING FOR THIS BAND OF ECHO MANIFESTED IN 800-700MB FRONTOGENESIS. LIFT NOT NEARLY AS ROBUST AS SEEN ON PVS NAM-WRF RUNS...AND QPF BECOMING MORE SCANT WITH EVERY MODEL RUN. SREF PROBABILITIES FOR MEASURABLE HAVE BEEN ON SLOW DECREASE WITH LAST RUN. HOWEVER...LATEST RUNS OF RUC13 /NAM-WRF AND SEVERAL LOCALLY RUN MESO-WRFS...SHOW BAND OF LGT SNOW/FLURRIES IN MPX FORECAST AREA WILL PULL SLOWLY EAST ACROSS AREAS NORTH OF I-90 THIS EVENING INTO THE OVERNIGHT...WHILE INFLUX OF MOISTURE ARRIVING INTO SRN WISCONSIN LINKS UP A SECONDARY AREA OF LGT SNOW DEVELOPING OUT OF ECNTL IA/NRN IL LATER TONIGHT. SO...CURRENT SNOW CHANCES LOOK GOOD...MAYBE A TAD TOO HIGH IN SOME PLACES. WILL BE TOUGH TO MEASURE SNOW MUCH PAST A DUSTING/COATING IN MANY AREAS GIVEN TRANSIENT NATURE OF FORCING AND SATURATION SLOW TO COME THUS FAR. BETTER CHANCES OF 1 INCH-TYPE ACCUMS STILL LOOK OVER FAR SERN FORECAST AREA /SWRN WI/ LATE TONIGHT. BINAU && .ARX WATCHES/WARNINGS/ADVISORIES... WI...NONE. MN...NONE. IA...NONE. && $$ 01/01 wi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MIAMI FL 1242 AM EST MON NOV 24 2008 .AVIATION... VFR CONDITIONS EXPECTED TO PERSIST THROUGH THE MORNING HOURS AND THROUGH THE DAY. THERE IS AN AREA OF CLOUDINESS IN THE VICINITY OF THE BAHAMAS WITH ISOLATED SHOWERS. AROUND 10Z ITS POSSIBLE TO HAVE VCSH FOR THE EAST COAST TERMINALS. OTHERWISE STRATOCU FROM 5 TO 7 KFT WILL STREAM IN OFF THE ATLANTIC WATERS THE REMAINDER OF THE EARLY MORNING HOURS. A WEAK LAND BREEZE IS POSSIBLE FOR THE EAST COAST TERMINALS...MORE LIKELY FOR KMIA...KOPF AND KTMB. THE EAST COAST TERMINALS WILL LIKELY HAVE AN EASTERLY SEA BREEZE NEAR 12 KNOTS THIS AFTERNOON. 60 && .PREV DISCUSSION... /ISSUED 955 PM EST SUN NOV 23 2008/ UPDATE...ON A MINOR TWEAK TO THE WINDS NEEDED THIS EVENING TO REFLECT CURRENT TRENDS, HOWEVER THAT MAINLY AFFECTED THE BAY AND ATLANTIC ZONES. ALL OTHER ELEMENTS UNCHANGED AS THE PREVIOUS FORECAST REMAINS ON TARGET. /TINGLER MARINE...GUIDANCE CONTINUES TO SHOW WINDS ACROSS THE ATLANTIC ZONES REMAINING MARGINAL FOR A SMALL CRAFT ADVISORY, AND INDEED FOWEY HAS BEEN AT 20 TO 23 KNOTS THIS EVENING FOR THE PAST FEW HOURS. SO, HAVE DECIDED TO PLAY IT SAFE AND KEEP THE SCA GOING THROUGH THE NIGHT FOR THE BAY AND ATLANTIC ZONES. ADDED THE BAY SINCE EASTERLY WINDS WILL AFFECT THE CENTRAL SECTIONS. THE MIAMI- DADE AND BROWARD COASTAL WATERS WILL THE ZONES MOST AFFECTED SINCE THE GRADIENT IS TIGHTER TO THE SOUTH, HOWEVER ALSO KEPT THE PALM BEACH WATERS IN AS WELL DUE TO A RECENT SHIP REPORT OF 20KTS. /TINGLER PREV DISCUSSION... /ISSUED 720 PM EST SUN NOV 23 2008/ AVIATION... VFR CONDITIONS WILL PERSIST ACROSS ALL SOUTH FLORIDA TERMINALS THIS FORECAST CYCLE...WITH THE PRIMARY CONCERN BEING WINDS. ALL AVAILABLE GUIDANCE NOW SUGGESTS THAT PRESSURE GRADIENT AND RESULTING ENE FLOW WILL STRENGTHEN OVER THE ATLANTIC TONIGHT... WHICH MAY BE THE KEY FACTOR IN DEVELOPMENT OF A LAND BREEZE. AT THIS TIME...WILL INDICATE NO LAND BREEZE AT PBI/FLL...AS EASTERLY FLOW SHOULD BE SUFFICIENTLY STRONG TO PREVENT A PENETRATION THIS CLOSE TO THE COAST. HOWEVER...AT TERMINALS FURTHER INLAND...WILL INDICATE WINDS BACKING TO NNW AND DECREASING IN THE PREDAWN HOURS ON MONDAY. WINDS WILL REMAIN LIGHTER AND FROM THE NE OVERNIGHT AT KAPF...WITH ESE FLOW OF 8-12 KNOTS EXPECTED AT ALL TERMINALS DURING THE DAY ON MONDAY. OTHERWISE...CLOUD CONDS OF FEW050/SCT070 WILL PREVAIL THROUGH THE PERIOD...AND ENOUGH THREAT FOR SHRA TO INCLUDE VCSH ALONG THE EAST COAST OVERNIGHT. MANY THANKS TO ZMA CWSU FOR EXCELLENT THOUGHTS AND INPUT FOR THIS FORECAST. 70/DD PREV DISCUSSION... /ISSUED 234 PM EST SUN NOV 23 2008/ DISCUSSION...HIGH PRESSURE WILL PULL AWAY FROM THE MID ATLANTIC COAST TONIGHT THROUGH MONDAY...RESULTING IN OUR PREVAILING WINDS TURNING MORE EASTERLY. MOISTURE WILL INCREASE SLIGHTLY...THOUGH BELIEVE THE GFS/NAM ARE A BIT TOO BULLISH ON THIS. KEPT SLIGHT CHANCE POPS NEXT FEW DAYS FOR THE ATLANTIC COAST...BUT OTHERWISE MOSTLY DRY WEATHER IS EXPECTED TO CONTINUE. MOST CHALLENGING PART OF THE FCST IS AGAIN ON THE LAND BREEZE AND ITS EFFECTS ON TEMPS AGAIN TONIGHT...AND MONDAY NIGHT AS WELL. GFS/NAM AND EVEN THE WRF DO NOT SHOW THE LAND BREEZE DEVELOPING TONIGHT. HOWEVER...THE PATTERN IS NOT CHANGING MUCH AND SO WE BELIEVE IT WILL OCCUR. THE NAM/WRF LOOK WAY TOO AGGRESSIVE WITH WINDS OVERNIGHT...AND THEY START THE DEVELOPMENT OF THE LAND BREEZE EARLY ON BEFORE THE WINDS SURGE TAKES OVER SWITCHING WINDS BACK NE. SINCE THIS SURGE LOOKS TO AGGRESSIVE...DECIDED TO DISCOUNT THIS. GIVEN THE FACT THAT GOOD RADIATIONAL COOLING IS AGAIN EXPECTED IN A STILL RATHER DRY AIRMASS...DECIDED TO BRING THE LAND BREEZE ACROSS MUCH OF THE EAST COAST METRO AREAS AGAIN TONIGHT...BUT NOT QUITE TO THE COAST...REASON BEING THAT IT MADE IT TO THE COAST JUST FOR AN HOUR THIS MORNING...AND ANY SLIGHT INCREASE IN THE NE-E WIND OVERNIGHT WOULD HOLD IT AT BAY. SHOULD MENTION THAT THE RUC IS ACTUALLY FOLLOWING RIGHT ALONG WITH OUR EXPECTATIONS TONIGHT. THE MAIN IMPACT THE FCST ON THE LAND BREEZE HAS IS WITH REGARDS TO TEMPS...AS IT CAN FLUCTUATE 5-10F DEGREES ON EITHER SIDE OF THE BOUNDARY...AS SEEN OVER THE PAST FEW MORNING`S. KEPT PATCHY FOG IN THE FCST TONIGHT AND MON NIGHT. MON NIGHT LOOKS TO BE MOST OPTIMAL...AHEAD OF A PRE-FRONTAL TROUGH. GFS/ECMWF STILL SHOW THE COLD FRONT MOVING ACROSS THE AREA TUESDAY NIGHT INTO WED MORNING...WITH A PRE-FRONTAL TROUGH MOVING BY ON TUESDAY. AFTER TEMPS WARM FINALLY TO NEAR 80 AHEAD OF THE FRONT TUESDAY...A SLIGHT COOL DOWN WILL OCCUR ON WEDNESDAY BEHIND THE FRONT. MOISTURE WILL REMAIN LIMITED...SO MOSTLY DRY WEATHER IS ANTICIPATED. MADE NO CHANGES TO THE EXTENDED FCST. THE DRY NOVEMBER WEATHER PATTERN LOOKS TO CONTINUE. BOTH GFS/ECMWF SHOW A GRADUAL WARMING TREND LATE IN THE WEEK AND INTO NEXT WEEKEND...WITH YET ANOTHER COLD FRONT EXPECTED EITHER SUNDAY OR MONDAY...DEPENDING ON THE MODEL...AND JUST TOO EARLY TO TELL AT THIS POINT IN TIME...BUT THE PARADE OF FRONTS LOOK TO CONTINUE. MARINE...DECIDED TO EXTEND THE SMALL CRAFT ADVISORY FOR THE ATLANTIC WATERS THROUGH THIS EVENING...AS GULF STREAM SEAS WILL LIKELY NOT START SUBSIDING UNTIL LATE EVENING AND OVERNIGHT DUE TO THE FACT THAT WINDS WILL REMAIN FROM A MORE NE DIRECTION BEFORE BECOMING EASTERLY LATER TONIGHT. OTHERWISE...WINDS OVER THE NEXT FEW DAYS WILL SLACKEN LEADING TO IMPROVING MARINE CONDITIONS. THE PRE-FRONTAL TROUGH WILL MOVE ACROSS THE AREA TUESDAY...SWITCHING WINDS TO W-NW...AND THE ACTUAL COLD FRONT WILL MOVE ACROSS THE AREA TUE NIGHT INTO EARLY WED MORNING...WITH A BRIEF WIND SURGE EXPECTED BEHIND IT...BUT GUIDANCE SUGGESTS ONLY 15-20 KT AND NOT TOO PROLONGED. FIRE WEATHER...RH`S HAVE BEEN DOWN AGAIN TO NEAR 40 PERCENT AS SOME DRY AIR HAS MIXED DOWN. MOISTURE WILL INCREASE JUST A TAD ON MONDAY. SLIGHT DRYING IS EXPECTED TUESDAY BEHIND A PRE-FRONTAL TROUGH...BUT NOT EXPECTED TO BE DRY ENOUGH AT THIS TIME TO RESULT IN CRITICAL RH`S. HOWEVER...WILL MONITOR TRENDS...BECAUSE TUE WILL BE THE WARMEST DAY OF THE WEEK...AND IF MORE DRYING OCCURS BETWEEN THE PRE-FRONTAL TROUGH AND THE ACTUAL COLD FRONT...THEN RH`S COULD FALL LOWER THAN FCST. THE DRIEST AIR WILL ADVECT IN ACROSS THE AREA BEHIND THE FRONT ON WEDNESDAY. TRENDED DEW POINTS/RH`S DOWN...THOUGH NOT AS LOW AS THE NAM AT THIS TIME...WHICH DROPS DEW POINTS TO THE LOWER 30S NW INTERIOR TO THE LOWER 40S SE. WE LIKELY WILL NEED TO CONTINUE A DECREASING TREND IN COMING FCSTS. && .PRELIMINARY POINT TEMPS/POPS... WEST PALM BEACH 75 60 79 57 / 20 20 10 10 FORT LAUDERDALE 77 62 79 61 / 20 20 10 10 MIAMI 77 62 80 62 / 20 20 10 10 NAPLES 76 61 77 57 / 10 10 10 10 && .MFL WATCHES/WARNINGS/ADVISORIES... FL...NONE. AM...SMALL CRAFT ADVISORY UNTIL 7 AM EST THIS MORNING FOR AMZ630- AMZ650-AMZ651-AMZ670-AMZ671. GM...NONE. && $$ LONG TERM...15/JR SHORT TERM/AVIATION...60/BD fl AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DES MOINES IA 316 AM CST MON NOV 24 2008 .SHORT TERM...TODAY SURFACE LOW PRESSURE IS EXITING FAR SE IOWA EARLY THIS MORNING AND LIGHT PRECIP HAS ENDED OVER FAR EASTERN COUNTIES. THE UPPER TROUGH WILL CONTINUE TO DIG INTO THE STATE TODAY.THE GFS/RUC ARE MORE AGGRESSIVE WITH CAA IN NORTHERN IOWA THIS AFTERNOON...COMPARED TO THE NAM. THE NAM INITIALIZED A BIT TOO WARM REGARDING THE AIRMASS TO THE NORTH...SO WENT WITH A BLEND OF NAM/GFS FORECAST SOUNDINGS FOR AFTERNOON HIGHS. THIS WAS CLOSE TO THE FWC/NGM MOS WITH SOME MINOR DOWNWARD ADJUSTMENTS IN THE SOUTH. THERE MAY BE A FEW FLURRIES OUT OF THE AFTERNOON STRATOCU IN THE MCW/ALO AREAS...ALTHOUGH RH IN THE SPZ IS MARGINAL. SOUNDINGS GO DRY ADIABATIC TO NEAR 850MB...AND WINDS AT THE TOP OF THE MIXED LAYER SUGGEST GUSTS INTO THE 30S. .LONG TERM...TONIGHT THROUGH SUNDAY STRONG UPPER LEVEL LOW NOW ACROSS LAKE WINNIPEG...WILL DIVE SOUTH THROUGH THE UPPER MISSISSIPPI VALLEY AND WESTERN GREAT LAKES REGION TONIGHT. THE SYSTEM WILL HAVE VERY LIMITED MOISTURE TAGGING ALONG THOUGH STILL POSSIBLE TO SQUEEZE A FEW FLURRIES OUT THIS EVENING NEAR MCW AND ALO. OTHERWISE...BETTER CHANCES FOR LIGHT SNOW WILL BE EAST OF THE MISSISSIPPI RIVER. THE SYSTEMS CONNECTION AT THE SFC WILL NOT BE WELL ESTABLISHED WITH LITTLE SFC REFLECTION BESIDES A WEAK COLD FRONT DROPPING SOUTH. THE SYSTEMS BIGGEST EFFECT ON TEMPERATURES FOR TUESDAY WILL BE DUE TO WARM ADVECTION IN THE MID LEVELS BETWEEN 700-500 MB AND COLD ADVECTION BETWEEN 925-800 MB. THIS WILL RESULT IN LIMITED MIXING POTENTIAL ON TUESDAY WITH AN INVERSION ABOVE 900 MB AND COOLER THAN TODAY WHEN BETTER MIXING OCCURS. THE UPPER LOW WILL LINK UP WITH SHORT WAVE ENERGY NOW MOVING THROUGH SOUTHERN IOWA AND MISSOURI AND CREATE A DEEP CLOSED LOW OVER THE NORTHEASTERN CONUS AND WILL SLOW THE FLOW OVER THE MIDWEST TUESDAY INTO EARLY THURSDAY. WEAK HIGH PRESSURE AND DRY AIR WILL BE IN PLACE DURING THIS PERIOD ALONG WITH LIGHT NORTHWEST FLOW AND SEASONAL TEMPERATURES. THE 850 MB THERMAL RIDGE IS EXPECTED TO PASS THROUGH IOWA ON THURSDAY...HOWEVER MUCH LIKE TONIGHT...WEAK COLD ADVECTION IS ANTICIPATED TO TAKE PLACE BELOW 900 MB AND EFFECTIVELY STRENGTHEN THE INVERSION IN PLACE. THIS WILL LIMIT HIGH TEMPERATURES ON THURSDAY TO NEAR CLIMATOLOGY WITH MIXING ONLY TO 950-925 MB. THE 06Z NAM IS MORE PROGRESSIVE WITH THE LOW LEVEL COLD ADVECTION ON THANKSGIVING DAY. REGARDLESS...EXPECT GOOD TRAVELING CONDITIONS ON THURSDAY. SOME DIFFERENCES AMONG SOLUTIONS REMAIN FRIDAY AND INTO THE WEEKEND THOUGH OVERALL TRENDS ARE TO SUPPRESS THE SOUTHERN PLAINS SYSTEM EVEN FURTHER SOUTH AS ANOTHER COLD FRONT BRINGING ANOTHER PUSH OF COOLER AND DRIER AIR SETTLES SOUTH ON FRIDAY. THE GEM IS CURRENTLY FARTHEST NORTH WITH THE PRECIPITATION TO NEAR THE IA/MO BORDER. && .AVIATION...24/06Z A SURFACE LOW PRESSURE CENTERED AT 24/05Z OVER SOUTHEAST IA WILL LIFT TO THE NE OVERNIGHT. A COLD FRONT ASSOCIATED WITH THE LOW IS SHIFTING EAST ACROSS CENTRAL IOWA AND SHOULD BE THROUGH CENTRAL IOWA BY 09Z. MVFR CIGS WILL BE IN PLACE THROUGH THAT TIME WITH GRADUAL IMPROVEMENT AFT 09Z. VFR CONDITIONS ARE EXPECTED TO PREVAIL AFT 18Z. && .DMX WATCHES/WARNINGS/ADVISORIES...NONE. && $$ SHORT TERM/AVIATION...KINNEY/FAB LONG TERM...DONAVON ia AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LAKE CHARLES LA 1157 PM CST SUN NOV 23 2008 .AVIATION...FIRST THING TO MENTION IS THE SMOKE ISSUE AT KLCH WHICH BROUGHT VISIBILITIES TO BELOW A MILE FOR A FAIR CHUNK OF THE EVENING. VISIBILITY HAS RISEN BACK TO 10SM RECENTLY BUT HAVE INCLUDED PREVAILING FOR THE EARLY PART OF THE FORECAST IN CASE SMOKE RETURNS. OTHERWISE EXPECT SLIGHT RESTRICTIONS TO VIS ALL SITES ON AT LEAST AN OFF AND ON BASIS OVERNIGHT. REGIONAL 88DS CONTINUE TO SHOW VERY LIGHT SHOWERS OR VIRGA MOVING NE TOWARD THE UPPER SE TX/SWRN LA COAST. HAVE CONTINUED EARLIER TREND OF BRINGING SCATTERED LIGHT SHOWERS INTO KLCH/KBPT BY SUNRISE AND BY MID-MORNING FOR REMAINING TAF SITES. EXPECT RAIN TO SPREAD ACROSS THE AREA AS THE COLD FRONT PASSES WEST TO EAST FROM LATE MORNING THROUGH MID-AFTERNOON. EXPECT CLEARING SKIES/VFR BY LATE IN THE PERIOD. 25 && .PREV DISCUSSION... /ISSUED 938 PM CST SUN NOV 23 2008/ UPDATE... ONLY UPDATE TO THE GRIDS THIS EVENING IS TO POPS/WX/QPF. RADAR MOSAIC SHOWS A BAND OF SHOWERS OVER THE GULF WATERS SOUTH OF HOUSTON/GALVESTON BAY. THIS ACTIVITY IS LIFTING SLOWLY NE AND BOTH RUC AND NAM APPEAR TO HAVE A HANDLE ON CURRENT TRENDS WITH INCREASING PRECIP OVER OUR SWRN ZONES AND WESTERN COASTAL WATERS OVERNIGHT AS LOW LEVEL FLOW OFF THE SFC BECOMES MORE SWRLY. LOWERED POPS TO 20 PERCENT AREAWIDE FOR THE REMAINDER OF THE EVENING...INCREASING TO 30 PERCENT AFTER MIDNIGHT FOR THE LOWER SE TX ZONES AND COASTAL WATERS MAINLY WEST OF CAMERON. REMAINDER OF FORECAST LOOKS GOOD. UPDATED ZONES HAVE BEEN SENT. 24 PREV DISCUSSION... /ISSUED 707 PM CST SUN NOV 23 2008/ AVIATION...MAIN CHALLENGE THIS TAF PACKAGE ISSUANCE IS TIMING OF THE ONSET OF PRECIPITATION. REGIONAL 88DS SHOW MAINLY LIGHT SHOWERS... MUCH OF IT PROBABLY JUST VIRGA ATTM...OVER THE GULF OFF THE MIDDLE TEXAS COAST MOVING NWD. MODEL PROJECTIONS SHOW PRECIP SPREADING OVER THE AREA FROM THE SOUTHWEST AND WEST STARTING TOWARD 12Z... ALTHOUGH LIKE LAST NIGHT THE GFS APPEARS TO BE A LITTLE WETTER AND FASTER THAN THE NAM. THUS HAVE TIMED THE PREVAILING POPS IN THE TAFS WITH THIS IN MIND. BUT UNTIL THEN FOR THE OVERNIGHT JUST STUCK WITH VFR CEILINGS GRADUALLY LOWERING...ALONG WITH SOME LIGHT RESTRICTIONS TO VISIBILITY AS WINDS LOOK SUFFICIENT FOR PREVENTING FOG FORMATION. 25 PREV DISCUSSION... /ISSUED 240 PM CST SUN NOV 23 2008/ DISCUSSION...A RATHER MILD AND PLEASANT AFTERNOON ONGOING ACROSS THE REGION. DESPITE CONSIDERABLE MID LEVEL CLOUDINESS...WARMING SOUTHERLIES HAVE MANAGED TO WARM TEMPS INTO THE UPPER 60S NORTH...LOW 70S SOUTH. DEWPOINTS GENERALLY RUNNING FROM 15 TO 20 DEGREES ABOVE THAT OF 24 HOURS PRIOR. LOCAL RADAR INDICATING JUST A BIT OF VIRGA OVER CENTRAL LOUISIANA. NEXT FRONTAL PASSAGE CONTINUES ON TRACK FOR MONDAY. LATEST MOS GUIDANCE SHOWING LESS PRE-FRONTAL ACTIVITY DEVELOPING ACROSS THE REGION TONIGHT. HAVE ADJUSTED GRIDS/POPS DOWN ACCORDINGLY. WILL HOWEVER MAINTAIN LIKELY POPS FOR MONDAY WITH GOOD LOW LEVEL CONVERGENCE DEVELOPING ALONG BOUNDARY...WITH DEEP OMEGAS/LIFT ALSO ACCOMPANYING FRONT. SUFFICIENT SPEED OF SYSTEM WILL EFFECTIVELY LIMIT ANY SIGNIFICANT WIDESPREAD RAIN AMOUNTS. HIGH PRESSURE BECOMES REESTABLISHED FOR TUESDAY AND WEDNESDAY. RETURN FLOW SETS UP THURSDAY AHEAD OF NEXT FRONTAL PASSAGE WHICH APPEARS LIKELY PER LONG RANGE MODELS ON FRIDAY. AVIATION...OVERCAST SKIES WILL CONTINUE FOR THE REMAINDER OF THE AFTERNOON INTO THIS EVENING AS SOUTHWEST FLOW AHEAD OF AN ADVANCING SHORT WAVE PULLS EAST PAC MOISTURE OVER THE REGION. ISENTROPIC LIFT IS EXPECTED TO BE WEAK...ALONG WITH SOME RELATIVELY DRY AIR BETWEEN THE SURFACE AND 10K FEET...AND THUS ANY PRECIPITATION WILL BE JUST SOME SPRINKLES OR VIRGA. CEILING HEIGHTS WILL CONTINUE TO BE AT VFR LEVELS. SOUTHERLY WINDS ARE EXPECTED TO INCREASE LATER TONIGHT INTO EARLY MONDAY AS SHORT WAVE CONTINUES TO ADVANCE TOWARD THE AREA. THESE WINDS WILL HELP INCREASE MOISTURE VALUES WITH GUIDANCE TIME HEIGHTS SHOWING OVER 80 PERCENT RH BETWEEN THE SURFACE TO OVER 20K FEET BY 24/12Z. THIS WILL HELP LOWER CEILING HEIGHTS TO BETWEEN 3K-5K FEET WITH A FEW SHOWERS DEVELOPING FROM WEST TO EAST DURING THE OVERNIGHT. WITH BOUNDARY LAYER WINDS EXPECTED BETWEEN 15 AND 20 KNOTS AND SOME LIFT SEEN BY PROGGED PVA IN THE LOW LEVELS...ANY FOG FORMATION WILL BE PATCHY IN NATURE WITH SOME MVFR VISIBILITIES POSSIBLE. SHOWERS ARE EXPECTED TO BE ON THE INCREASE AFTER 24/12Z FROM WEST TO EAST AS STRONGER LIFT FROM AN APPROACHING COLD FRONT TAPS INTO THE ABUNDANT MOISTURE. RUA MARINE...A MODEST SOUTHERLY FLOW WILL CONTINUE TONIGHT AHEAD OF AN ADVANCING COLD FRONT. THE FRONT WITH SHOWERS AND THUNDERSTORMS WILL MOVE ACROSS THE NORTHWEST GULF MONDAY FOLLOWED BY A STRONG OFFSHORE FLOW. && .PRELIMINARY POINT TEMPS/POPS... KLCH 60 73 47 69 44 / 20 70 10 0 0 KBPT 62 74 46 70 44 / 30 70 10 0 10 KAEX 58 69 42 67 40 / 20 70 10 0 10 KLFT 58 71 48 66 43 / 20 70 10 0 0 && .LCH WATCHES/WARNINGS/ADVISORIES... LA...NONE. TX...NONE. GM...NONE. && $$ la AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MARQUETTE MI 425 AM EST MON NOV 24 2008 .SYNOPSIS... 08Z WATER VAPOR LOOP AND RUC 500MB HEIGHT ANALYSIS SHOWED RIDGING OVER THE WESTERN U.S. INTO SW CANADA...RIDGING IN THE OHIO VALLEY INTO THE EASTERN GREAT LAKES...AND A TROUGH FROM MANITOBA SOUTHWARD INTO THE CENTRAL PLAINS. WITHIN THE TROUGH...AN UPPER LOW IS LOCATED AT THE FAR NORTH END OF LAKE WINNIPEG. THE WARM CONVEYOR BELT AHEAD OF THE UPPER LOW EXTENDS FROM MO ACROSS UPPER MI AND INTO NE ONTARIO. SOME -SN IS FALLING OUT OF THE CONVEYOR BELT OVER THE CENTRAL PORTION OF THE CWA...ALSO IN THE SAME PLACE WHERE BETTER MOISTURE IS BASED ON 00Z RAOBS FROM MPX...COMPARED TO GRB AND APX WHICH REFLECT THE DRIER AIRMASS OVER EASTERN UPPER MI. A DRY SLOT IS EVIDENT ON 11-3.9 U IMAGERY OVER NE MN...BUT FARTHER NW OVER NW MN INTO MANITOBA IS THE COLD CONVEYOR BELT (CCB) CLOUDS ON THE BACK SIDE OF THE UPPER LOW. 850MB TEMPS UNDER THE CCB WERE AROUND -14C BASED ON THE 00Z SOUNDING FROM CYQD...QUITE A BIT COLDER THAN THE -1C AT MPX...-4C AT INL AND -6C AT CWPL. TO THE SW OF UPPER MI ON WATER VAPOR...A SHRTWV IS MOVING THROUGH SRN IA. ASSOCIATED WITH THE SHRTWV IS A 1015MB SFC LOW IN SE IA. A TROUGH EXTENDS NE FROM THE LOW ACROSS CENTRAL UPPER MI...THEN HEADS BACK TO THE NW AS A COLD FRONT WHERE IT CONNECTS UP TO A 1008MB LOW IN FAR NW ONTARIO. && .DISCUSSION... MAIN FORECAST CONCERNS ARE THE AMOUNT OF SNOW THE NEXT TWO DAYS... ALONG WITH POTENTIAL FOR FREEZING DRIZZLE. TODAY...UPPER LOW AT THE NORTH END OF LAKE WINNIPEG IS PROGGED TO SLIDE A LITTLE BIT FARTHER WEST COMPARED TO YESTERDAYS 00Z RUNS...MOVING INTO WRN WI AT 00Z TUE. THE BULK OF THE COLD AIR SEEN UPSTREAM AT CYQD WILL STAY UNDER OR TO THE WEST OF THE UPPER LOW. HOWEVER...SOME COOLING IS STILL EXPECTED TO COME INTO UPPER MICHIGAN WITH THE APPROACH OF THE UPPER LOW. NAM/GFS SHOW 850MB TEMPS FALLING TO -8 TO -10C OVER WRN LAKE SUPERIOR...WHICH WOULD BE GOOD ENOUGH FOR LAKE ENHANCED OR PERHAPS EVEN PURE LAKE EFFECT. WITH NW WINDS... IT WOULD SEEM LIKELY FOR SNOW IN WRN UPPER MI...ESPECIALLY IN UPSLOPE AREAS. HAVE RAISED POPS TO DEFINITE IN THE UPSLOPE AREA FROM IWD TO ROCKLAND. SOUNDINGS SUGGEST SNOW TO WATER RATIOS SOMEWHERE AROUND 10 TO 1...DUE TO MAJORITY OF VERTICAL MOTION BELOW THE DENDRITIC SNOW GROWTH ZONE...WHICH WITH A BLEND OF NAM/LOCAL WRF-ARW RUN/GFS FOR QPF RESULTS IN 1 TO 2 INCHES. THE AMOUNT OF COLD AIR CROSSING CENTRAL AND LAKE SUPERIOR IS A LITTLE MORE UNCERTAIN... WITH THE GFS SHOWING -8 TO PERHAPS -10C AT 00Z TUE...COMPARED TO THE NAM AND LOCAL WRF-ARW WHICH HAVE -4 TO -6C. EITHER SCENARIO SEEMS AT LEAST POSSIBLE FOR LAKE ENHANCED PCPN...ESPECIALLY GIVEN THAT THERE WILL BE PLENTY OF MOISTURE AROUND IN THE WARM CONVEYOR BELT AHEAD OF THE UPPER LOW. THE PROBLEM IS THAT THE WARMER SCENARIO WOULD RESULT IN POTENTIAL FOR RAIN TO MIX IN...PARTICULARLY OVER LAKE SUPERIOR AND OVER LAND NEAR THE SUPERIOR SHORELINE. GIVEN 00Z SOUNDING FROM CWPL UPSTREAM WAS -6C...WILL LEAN TOWARDS THE NAM/LOCAL WRF-ARW. THE WARMER SCENARIO ALSO MEANS THAT ANY SNOW THAT FALLS INLAND WILL ALSO BE WETTER WITH SNOW TO WATER RATIOS LESS THAN 10 TO 1. COULD BE AN INCH...PERHAPS TWO OF THIS WET SNOW IN THE EASTERN CWA. THE CENTRAL U.P. LOOKS TO BE MAINLY DRY TODAY...WITH SOME SUN AS THE DRY-SLOT WORKS IN. A FEW -SHSN COULD WORK IN OVER MQT COUNTY OFF OF WRN SUPERIOR IN THE AFTN...BUT THAT IS ABOUT IT FOR CENTRAL UPPER MI. ALTHOUGH COLD AIR IS FLOWING IN...EXPECT HIGHS AGAIN TODAY IN THE 30S...WARMEST SOUTH CENTRAL WITH DOWNSLOPING NW WINDS AND NEAR LAKE SUPERIOR WITH HEAT FLUX OFF THE WARMER WATER. TONIGHT...UPPER LOW MOVES SE INTO OHIO BY 12Z TUE...COMING CLOSE TO PHASING WITH THE SHRTWV CURRENTLY HEADING EAST OUT OF SRN IA. AS A RESULT...THE SFC LOWS THAT ARE CURRENTLY IN NW ONTARIO AND SE IA END UP MERGING TOGETHER INTO A DEEPER 1003 MB LOW NEAR LONDON ONTARIO AT 12Z TUE. THE DEEPENING LOW HELPS TO STRENGTHEN NORTH TO NE WINDS OVER EASTERN LAKE SUPERIOR. NORMALLY THIS WOULD SPELL COLDER AIR MOVING IN. HOWEVER...THE AIR COMING IN IS EITHER JUST AS COOL OR PERHAPS EVEN SLIGHTLY WARMER THAN THE AIR THAT IS IN OVER THE CWA AT 00Z PER 850MB TEMP PROGS. THE REASON IS THAT THE DEEPENING LOW HELPS TO PULL WARMER AIR IN OFF THE ATLANTIC INTO ITS CIRCULATION. SO WITH LITTLE TO NO CHANGE IN 850MB TEMPS...LAKE ENHANCEMENT SHOULD BE THE RULE...POSSIBLY PURE LAKE EFFECT IN THE WRN U.P.. PROBLEM IN THE WRN U.P. COMPARED TO TODAY IS THAT WITH THE DEPARTURE OF THE UPPER LOW...INVERSIONS FALL WITH THE MID-LEVEL HEIGHT RISES. THE QUESTION IS IF THE -10C ISOTHERM DRIES OUT...WHICH WOULD CHANGE THE PCPN FROM SNOW TO FZDZ GIVEN THAT AN UPSLOPING WIND CONTINUES. RIGHT NOW ONLY OUR LOCAL WRF-ARW RUN SHOWS THIS OCCURRING...WHILE THE NAM/GFS SHOW THE -10C ISOTHERM REMAINING MOIST. THEREFORE HAVE DECIDED TO KEEP THE P-TYPE AS SNOW. IN THE CENTRAL AND EAST...INVERSIONS WILL GRADUALLY LOWER AS WELL...BUT NOT AS QUICK. SO CONFIDENCE IS HIGHER THAT THE P-TYPE WILL STAY AS SNOW INLAND FROM LAKE SUPERIOR. AMOUNTS OF SNOW SHOULD NOT BE THAT IMPRESSIVE...MAYBE AN INCH OR TWO GIVEN LOW SNOW TO WATER RATIOS. REGARDING AREAS NEAR THE LAKE...THE WARMER NAM/LOCAL WRF-ARW RUNS SUGGEST HOLDING ON TO A RAIN/SNOW MIX THROUGH AT LEAST 09Z. IF THE PCPN IS GENERALLY LIGHT...THEN MORE OF THE PCPN SHOULD FALL AS RAIN. GIVEN THE WARMER 850MB TEMPS AND PLENTY OF CLOUDS...ALONG WITH A FLOW OF AIR OFF THE WARM LAKE SUPERIOR WATER...TEMPS SHOULD NOT DROP TOO MUCH. COLDEST READINGS EXPECTED IN THE INTERIOR WEST...CLOSEST TO THE COLDEST 850MB AIR...BUT EVEN THESE SHOULD ONLY BE IN THE MID 20S. TUESDAY...UPPER LOW IS PROGGED TO SHIFT INTO NORTH CENTRAL PA BY 00Z WED...WITH THE SFC LOW MOVING TO THE LAKE ONTARIO AREA. THIS ALLOWS A HIGH PRESSURE RIDGE TO BUILD INTO WESTERN UPPER MI BY 00Z...IN ADDITION TO CONTINUED MID-LEVEL HEIGHT RISES THROUGH THE DAY. THE RIDGE SHOULD BRING DRIER AIR IN...LIKELY TO THE WESTERN CWA...ENOUGH TO END PCPN BY EARLY AFTN. HOWEVER...THE CENTRAL AND EASTERN CWA WILL STAY IN LOW CLOUDS TRAPPED UNDER THE LOWERING INVERSION... ENHANCED BY LAKE SUPERIOR GIVEN COOL AIR BELOW THE INVERSION. PCPN TYPE IS VERY TRICKY...AS ALL MODELS SHOW THE -10C LAYER DRYING OUT THROUGH THE DAY. GIVEN A NORTH WIND OVER EASTERN LAKE SUPERIOR...SET UP IS FAVORABLE FOR UPSLOPE. SO WITH LAKE ENHANCEMENT OFF LAKE SUPERIOR AND UPSLOPE FLOW PRODUCING VERTICAL MOTION...SOME PCPN SHOULD OCCUR OUT OF THE CLOUDS. RIGHT NOW HAVE GONE WITH EITHER SNOW SHOWERS OR DZ/FZDZ (FZDZ OVER INLAND AREAS THROUGH THE EARLY AFTN). POPS ARE HIGHEST IN THE UPSLOPE AREAS OF THE NORTH CENTRAL IN THE MORNING...THEN DECREASE IN THE AFTN AS THE DRIER AIR TRIES TO WORK IN. GIVEN CLOUD COVER AND 850MB TEMPS THAT ARE SLIGHTLY COOLER THAN TODAY...HIGHS WILL ALSO END UP SLIGHTLY COOLER. STILL...MOST LOCATIONS SHOULD BE IN THE 30S...WARMEST IN THE DOWNSLOPE AREAS OF THE SOUTH CENTRAL. TUE NIGHT THROUGH THU...PER THE UKMET/NAM/GFS/ECMWF...UPPER MI LOOKS TO BE CAUGHT IN SQUEEZE-PLAY AS THE UPPER LEVEL PATTERN OVER CANADA AND THE NORTHERN U.S. BECOMES BLOCKED. THIS BLOCKING LOOKS TO BE A RESULT OF STRONG RIDGING BUILT UP AHEAD OF THE UPPER LOW TO OUR EAST. IN FACT...MODELS ARE IN GOOD AGREEMENT TAKING THE UPPER LOW BACK TO THE NW DURING THIS PERIOD...BASICALLY PULLED BY THE CURRENT SHRTWV CROSSING SRN IA. WHAT THIS MEANS FOR UPPER MI IS A PERSISTENT CHANCE FOR -SN ACROSS THE EAST HALF OF UPPER MI CLOSER TO THE DEEPER MOISTURE AROUND THE UPPER LOW...WHILE THE WEST HALF OF UPPER MI IS DRY WITH PARTLY CLOUDY SKIES UNDER THE INFLUENCE OF LOW INVERSIONS AND THE SURFACE RIDGE. STILL MAINTAINED THE POSSIBILITY OF SOME DZ/FZDZ OVER THE EASTERN CWA TUE NIGHT SINCE IT DOES NOT APPEAR THAT THE DEEPER MOISTURE WILL MOVE IN UNTIL WED. ANY PCPN LOOKS TO BE LIGHT AT THE CURRENT TIME DUE TO LACK OF SIGNIFICANT MOISTURE WITH THE UPPER LOW. GIVEN THE BLOCKED PATTERN...NO SIGNIFICANT COOLING OR WARMING IS PLANNED. THEREFORE... LOWS AND HIGHS ARE FORECAST TO BE ABOUT THE SAME THROUGH THE PERIOD...IN THE 20S AND 30S RESPECTIVELY. BEYOND THU...NO SIGNIFICANT CHANGES MADE. 00Z ECMWF/GFS/GFS ENSEMBLES ARE ALL IN VERY GOOD AGREEMENT SHOWING THE DEVELOPMENT OF A BROAD TROUGH ACROSS THE GREAT LAKES INTO THE OHIO VALLEY FOR FRI INTO THE WEEKEND. THIS TROUGH IS FORMED BY A COMBINATION OF THE UPPER LOW TO OUR EAST ON THU AND ANOTHER TROUGH DROPPING DOWN OUT OF CENTRAL CANADA. THIS MEANS THAT GRADUAL COOLING WILL OCCUR...COLD ENOUGH TO SET UP PURE LAKE EFFECT BY THE WEEKEND. && .AVIATION (FOR THE 06Z TAF ISSUANCE)... LIGHT SNOW ASSOCIATED WITH A TROUGH MOVING THROUGH UPPER MICHIGAN COULD BRING A PERIOD OF MVFR VSBY. WITH LOW LEVEL MOISTENING...MVFR CIGS ARE ALSO EXPECTED WITH THE POTENTIAL FOR OCNL IFR CIGS. THEN...AS NORTHWEST TO NORTHERLY FLOW SETS UP AND COLD AIR MOVES IN ALOFT...-SHSN WILL BECOME POSSIBLE...MAINLY AT KCMX IN THE AFTERNOON. BY MONDAY EVENING...ADDITIONAL LAKE ENHANCED SNOW MAY BE POSSIBLE AT KSAW AS CONVERGENT NNE FLOW DEVELOPS BEHIND THE DEPARTING MID LEVEL AND SFC LOWS. && .MARINE (FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)... A LOW PRES TROF EXTENDING FROM NORTHERN ONTARIO ACROSS THE UPPER GREAT LAKES TO THE MID MISSISSIPPI RIVER VALLEY WILL CONSOLIDATE INTO A LOW PRES CENTER OVER SRN LAKE HURON THIS EVENING. AS THIS OCCURS...NRLY WINDS WILL BEGIN TO INCREASE ACROSS LAKE SUPERIOR THIS AFTN AND MORE SO THIS EVENING AND OVERNIGHT. EXPECT NRLY WINDS IN THE 20-30KT RANGE TONIGHT WITH THE STRONGEST WINDS OVER THE E HALF OF THE LAKE. IT`S NOT OUT OF THE QUESTION THAT SOME GALE FORCE GUSTS COULD OCCUR...BUT SINCE THERE IS A LACK OF COLD AIR ADVECTION TO INCREASE MIXING...WILL HOLD OFF ON ANY MENTION OF GALES. PROGRESSION OF THE MAIN WEATHER SYSTEMS WILL SLOW TO A CRAWL TUE THRU FRI. WITH LOW PRES TO THE E AND HIGH PRES TO THE W...N TO NW WINDS WILL BE THE RULE TUE THRU FRI WITH THE STRONGEST WINDS REMAINING OVER THE E HALF OF LAKE SUPERIOR. OVERALL...AFTER TUE...WINDS SHOULD GENERALLY BE IN THE 15-25KT RANGE OVER THE E AND 10-20KT OVER THE W. && .MQT WATCHES/WARNINGS/ADVISORIES... UPPER MICHIGAN...NONE. LAKE SUPERIOR...NONE. LAKE MICHIGAN...NONE. && $$ SYNOPSIS/DISCUSSION...AJ AVIATION...JLB MARINE...ROLFSON mi AREA FORECAST DISCUSSION...UPDATE NATIONAL WEATHER SERVICE EUREKA CA 505 AM PST MON NOV 24 2008 .SYNOPSIS...A STRONG UPPER LEVEL LOW OFF THE CENTRAL CALIFORNIA COAST WILL SLOWLY MOVE TOWARD SOUTHERN CALIFORNIA TODAY...BRINGING WET WEATHER TO THE REGION TUESDAY AND TUESDAY NIGHT. AFTER A BRIEF BREAK ON WEDNESDAY...A STORM SYSTEM WILL BRING ADDITIONAL RAIN TO NORTHERN CALIFORNIA ON THURSDAY. AFTER THAT HIGH PRESSURE WILL BRING DRIER WEATHER TO THE AREA FOR THE WEEKEND INTO EARLY NEXT WEEK. && .SHORT TERM...TODAY THROUGH WEDNESDAY...SATELLITE IMAGES SHOW A STRONG UPPER TROUGH JUST EAST OF 140 W THIS MORNING WITH SPLITTING FLOW EVIDENT AND AN IMPRESSIVE DRY SLOT EXTENDING NORTH TO SOUTH ALONG THE TROUGH AXIS. MODELS ARE COMING INTO BETTER AGREEMENT WITH THIS FEATURE...BRINGING THE UPPER LOW TOWARD THE COAST...ALTHOUGH WHILE NAM AND GFS BRING AN OPEN WAVE ONSHORE EARLY WEDNESDAY THE ECMWF MAINTAINS A CLOSED LOW CIRCULATION. NEVERTHELESS ALL SOLUTIONS POINT TOWARD A DECENT CHANCE OF RAIN ON TUESDAY AS MOIST FLOW WRAPS AROUND THE LOW AND INTO NORTHERN CALIFORNIA FROM THE SOUTH TO SOUTHEAST. THE MAIN VORT MAX IS HEADED FOR SOUTHERN CALIFORNIA...AND THE BEST INSTABILITY IS LIKELY TO STAY SOUTH OF THE CWA AS WELL. GFS IS STILL HINTING AT SOME SUBTROPICAL MOISTURE GETTING PULLED INTO THE FLOW AND HEADING NORTHWARD...BUT CERTAINLY NOT IN THE MANNER OF A CLASSIC PINEAPPLE CONNECTION. MODELS CONTINUE THE SLOWING TREND SO TRIMMED BACK POPS SLIGHTLY FOR THE MONDAY NIGHT PERIOD...AND ALLOWED CHANCE POPS TO INCREASE FROM THE SOUTH ON TUESDAY. SHOWERS WILL DECREASE FROM NORTHWEST TO SOUTHEAST LATE TUESDAY NIGHT INTO WEDNESDAY AS THE LOW MAKES LANDFALL SOUTH OF PT CONCEPTION...AND BEGINS TO MOVE INLAND TOWARD VEGAS AND THE 4 CORNERS STATES. THIS WILL ALLOW SOME ANTICYCLONIC ROTATION TO DEVELOP OVER THE PACIFIC NORTHEAST AND NORTHERN CALIFORNIA WEDNESDAY...AS ANOTHER STRONG LOW HEADS ACROSS THE GULF OF ALASKA. .LONG TERM...WEDNESDAY NIGHT THROUGH SUNDAY...MODELS SHOW REASONABLE AGREEMENT IN HANDLING OF THE NEXT LOW FORECAST TO APPROACH THE PACIFIC NORTHWEST LATER THIS WEEK. TIMING HAS SLOWED SOMEWHAT TO FAVOR PRECIP AFFECTING MAINLY THE NORTHWEST PORTION OF THE CWA ON THURSDAY...SPREADING SOUTHWARD ON THURSDAY NIGHT....AND DECREASING TO THE NORTHEAST ON FRIDAY. FOR THE WEEKEND THE MODELS ALL INDICATE A LOW FORMING ON THE EAST SIDE OF A LONGWAVE RIDGE IN THE EASTERN PACIFIC. BY 12Z SATURDAY THE GFS AND EC ARE JOINED BY THE CANADIAN IN FORMING A CUTOFF LOW SOMEWHERE IN THE SOUTHERN CALIFORNIA/NORTHERN BAJA VICINITY...AS A STRONG RIDGE CONTINUES TO BUILD INTO THE PACIFIC NORTHWEST. BY SUNDAY THE GFS IS MOST AGGRESSIVE IN WESTWARD MOVEMENT OF THE CUTOFF...PUSHING IT OFFSHORE SOUTH OF 30 N. THIS TYPE OF SOLUTION FAVORS DRY WEATHER FOR NORTHWEST CALIFORNIA. CMC && .AVIATION...CURRENT OBSERVATIONS AND 10Z RUC ANALYSIS CONFIRM WEAK OFFSHORE FLOW OUT OF THE SOUTHEAST IS IN PLACE KEEPING FOG AND STRATUS FROM DEVELOPING ALONG THE COAST. THIS FLOW IS EXPECTED TO PERSIST THROUGH THE PERIOD KEEPING WIDESPREAD VFR FLYING CONDITIONS IN THE FORECAST. MID AND HIGH LEVEL CLOUD COVER WILL INCREASE TODAY AS A WEAKENING FRONTAL BOUNDARY APPROACHES THE AREA FROM THE NORTHWEST. BK .MARINE...A LOW PRESSURE SYSTEM HAS TAKEN SHAPE OFF THE COAST OF SOUTHERN CALIFORNIA THIS MORNING KEEPING SOUTHERLY WINDS IN PLACE OVER THE COASTAL WATERS OFF NORTHEN CALIFORNIA. THIS WILL PERSIST THROUGH TONIGHT WHEN THE WINDS WILL BEGIN TO SHIFT AROUND TO THE NORTHEAST IN RESPONSE TO SHORT LIVED HIGH PRESSURE THAT WILL BUILD IN NORTH OF THE AREA. A MIXED SWELL WILL MOVE INTO THE WATERS LATER THIS MORNING DUE TO THE LOW PRESSURE SOUTH OF THE AREA. THE DOMINANT SWELL WILL STILL BE OUT OF THE WEST AT 5 TO 6 FT...WITH A SOUTHERLY SWELL MOVING IN AT 3 FT. PERIODS WILL BE 11 SECONDS OUT OF THE WEST AND 6 TO 7 SECONDS OUT OF THE SOUTH. SOUTHERLY SWELL TRAIN WILL SUBSIDE TOMORROW EVENING AS THE NORTHWESTERLY SWELL BEGINS TO BUILD TO NEAR 12 FT ON WEDNESDAY NIGHT IN RESPONSE TO THE SHORT LIVED HIGH PRESSURE BUILDING INTO THE PAC NW. PERIODS WILL BE ON THE ORDER OF 15 SECONDS SO NOT EXPECTING A HAZARDOUS SEAS WARNING JUST AN ADVISORY FOR HAZARDOUS SEAS DURING THIS TIME. ANOTHER LARGER SWELL TRAIN WILL MOVE INTO THE WATERS FRIDAY MORNING. BK && .EKA WATCHES/WARNINGS/ADVISORIES... && $$ VISIT US AT HTTP://WWW.WEATHER.GOV/EUREKA ca AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 1118 AM EST MON NOV 24 2008 .SYNOPSIS... LOW PRESSURE IN THE GREAT LAKES TODAY WILL SPREAD PRECIPITATION INTO NEW ENGLAND TONIGHT AND TUESDAY...MOSTLY IN THE FORM OF RAIN. THE SYSTEM MAY BRING STRONG WINDS AS WELL...ESPECIALLY NEAR THE COAST. COOLER AND DRY WEATHER WILL RETURN IN THE WAKE OF THE LOW MIDWEEK ON. && .NEAR TERM /UNTIL 8 PM THIS EVENING/... 915 AND 1015 AM MINOR ADJUSTMENTS TO GRID TRENDS THIS MORNING. RUC 13 VIA TSECS HAS THE BEST HANDLE ON CURRENT AND NEAR TERM CLOUD BANDS NR 7000 FT. GRIDS MODIFIED. SURFACE HIGH PRESSURE WILL GRADUALLY MOVE OFF THE COAST TODAY AS LOW PRESSURE APPROACHES FROM THE WEST. THE RESULT WILL BE INCREASING HIGH CLOUDINESS...BUT ANY PRECIPITATION WILL HOLD OFF UNTIL THIS EVENING OR TONIGHT. IN FACT...WE MAY SEE A GOOD AMOUNT OF FILTERED SUNSHINE TODAY. TEMPERATURES WILL BE WARMER THAN THEY HAVE BEEN OVER THE LAST SEVERAL DAYS AS THE FLOW GOES SOUTH AND THE AIRMASS WARMS. EVEN STILL...HIGH TEMPS WILL TOP OUT AROUND 5 DEGREES BELOW NORMAL. MAXES WERE DERIVED FROM A BLEND OF NAM 2M TEMPS AND MAVMOSGUIDE...WITH SLIGHTLY MORE WEIGHT GIVEN TO THE MOS. && .SHORT TERM /8 PM THIS EVENING THROUGH TUESDAY NIGHT/... 1110 AM... ISSUING HIGH WIND WATCH BOSTON TO MANCHESTER AND POINTS EAST TO CAPE ANN. SE WIND HIGH WIND CASES IN OUR CLIMO ARE RARE BUT MARGINAL HIGH WIND CASE ENVISIONED PER MODEL PRES CHANGES... LAPSE RATES...BL AND 925 MB WINDS BOTH 12Z GFS/NAM. NAM BL WINDS ARE UP TO 38 KTS NOW AT CONCORD. THAT SEEMS A LITTLE HIGH BUT PER COLLAB WITH GYX...ADDED ASH TO MHT. GREATEST CONFIDENCE IN SIGNIFICANT POWER OUTAGES AND SUSTAINED WIND 40 OR GREATER IS MQE AND BOS TO LWM REGION EWD. MAY SEE GUST 60 KTS AT MQE. WIND ADVY WILL BE ISSUED REMAINDER I95 REGION OF RI AND MASS AT 4PM. REMAINDER BLO FROM 4AM... CLOUDS WILL RAPIDLY INCREASE EARLY THIS EVENING AS LOW PRESSURE CONTINUES TO APPROACH. THE PRECIPITATION SHIELD WILL ARRIVE FROM WEST TO EAST...STARTING IN THE CT VALLEY SOMETIME BETWEEN 02Z AND 06Z...THEN SPREADING EASTWARD FROM THERE. THE DOMINANT PRECIPITATION TYPE WILL BE RAIN...ALTHOUGH A PORTION OF NW MASS AND SW NH MAY SEE A BRIEF PERIOD OF LIGHT SNOW AT THE START. NO ACCUMULATION IS EXPECTED. ATTM...THE THINKING IS THAT THE SFC TEMPS WILL WARM UP ENOUGH TO ALLOW FOR MUCH IN THE WAY OF FREEZING RAIN IF ANY AT ALL. IT WOULD BE EXTREMELY ISOLATED AT BEST. WENT WITH CATEGORICAL POPS FOR ALL ZONES BY LATE AT NIGHT. TEMPS WILL SLOWLY RISE OVERNIGHT AS THE LOW LEVEL JET GETS GOING. RAIN WILL BECOME HEAVY AT TIMES TUESDAY MORNING...ESPECIALLY THE WESTERN HALF OF THE CWA...BEFORE SHIFTING TO THE EASTERN HALF DURING THE AFTERNOON. CATEGORICAL POPS FOR ALL AREAS. BEST GUESS AT THIS TIME IS THAT A GENERAL .75 TO 1.5 INCHES OF RAIN WILL FALL...WITH LOCALLY HIGHER AMOUNTS. THIS SHOULDN/T CAUSE WIDESPREAD FLOODING PROBLEMS. HOWEVER...WE/LL LIKELY SEE THE NORMAL MINOR URBAN/POOR DRAINAGE FLOODING AT TIMES. WENT WITH A SLIGHT CHANCE OF THUNDER...MAINLY FOR SOUTHERN AND EASTERN ZONES...AS WEAK INSTABILITY MAY DEVELOP AS THE LLJ PUMPS NORTHWARD A DECENT PLUME OF THETA-E. THE BIGGEST CONCERN FOR TUESDAY MAY BE THE WINDS...AS A 65 KNOT SOUTHERLY LOW LEVEL JET DEVELOPS. THIS MAY LEAD TO SPEEDS OF WIND ADVISORY CRITERIA IF NOT ISOLD MARGINAL HWW CRITERIA TUESDAY AFTERNOON ALONG THE SOUTH COAST AND POSSIBLY THE REST OF EASTERN MASS. THE HIGHER TERRAIN MAY BE AFFECTED AS WELL. SUBSEQUENT SHIFTS MAY HAVE TO CONSIDER ADVISORIES/WATCHES/WARNINGS. ANY CONVECTION COULD BRING DOWN ISOLD STRONG WIND GUSTS AS WELL...ESPECIALLY IF SFC TEMPS REALLY WARM UP. THERE MAY BE A 1-2 FOOT SURGE ON THE SOUTH COAST BAYS WITH THE STRONG SOUTHERLY LLJ....BUT TIDES ARE LOW AND PRESSURE FALLS NOT OVERLY IMPRESSIVE. THEREFORE...NO COASTAL FLOODING PROBLEMS ARE EXPECTED AT THIS TIME. MODEL MAX TEMPS FOR TUESDAY LOOKED TOO LOW. THESE SOUTHERLY LLJ EVENTS ALMOST ALWAYS PRODUCE HIGHER SURFACE TEMPS THAN WHAT MOS AND EVEN MODEL 2M TEMPS INDICATE. WENT FOR MID 50S ACROSS EASTERN MASS/RI AND PORTIONS OF CT. COOLER TEMPS /40S - LOW 50S/ WILL BE FOUND ACROSS THE INTERIOR ALTHOUGH IT/S QUITE POSSIBLE THAT THEY WILL NEED TO BE RAISED AS WELL. OCCLUSION WILL BE MOVING ACROSS THE REGION EARLY TUE EVENING. NAM IS THE SLOWEST MOVING THE OCCLUSION THROUGH AND BRINGS A SLUG OF HEAVY RAIN TO E MA INTO SE NH AT THE NOSE OF A PERSISTENT SELY LLJ. CONSENSUS AMONG OTHER MODELS INCLUDING GFS FAVORS A FASTER SOLUTION SO WE LEANED TOWARD GFS WHICH LIFTS THE HEAVIER RAFL NORTH AND EAST OF SNE BY TUE EVENING. HOWEVER...SOME RAIN WILL LIKELY LINGER ACROSS NE ZONES NEAR THE NOSE OF THE LLJ SO WE WILL HAVE LIKELY TO CATEGORICAL POPS TUE EVENING FROM SW NH THROUGH E MA WITH LOWER POPS FURTHER SW AS DRY SLOT MOVES IN. ALSO...GFS INSTABILITY PARAMETERS SUGGEST ISOLD ELEVATED THUNDER POSSIBLE E MA THROUGH SE NH. TREND TUE NIGHT WILL BE FOR DECREASING POPS AS THE DRY SLOT MOVES THROUGH. WIND MAY STILL BE A CONCERN TUE EVENING FROM CAPE COD THROUGH CAPE ANN WHICH WILL BE CLOSEST TO THE LLJ AND WILL HAVE HIGHER GUSTS IN THIS REGION. COLDER AIR WILL BE SLOW TO MOVE IN TUE NIGHT AS UPPER LOW REMAINS TO THE NW WITH SOUTHERLY FLOW ALOFT. MIN TEMPS WILL RANGE FROM UPPER 20S FAR NW TO MID/UPPER 30S COASTAL PLAIN. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... CLOSED LOW LIFTS NWD INTO CANADA WED. MAY GET ENOUGH DRYING FOR SOME SUNSHINE WED MORNING BUT CLOUDS SHOULD QUICKLY FILL BACK IN ESPECIALLY IN THE INTERIOR. CANT RULE OUT A FEW RA/SNW SHOWERS AS SHORTWAVE ENERGY ROTATES AROUND THE UPPER LOW. BEST CHC WILL BE ACROSS NW ZONES CLOSEST TO THE COLD POOL ALOFT. SEASONABLE TEMPS EXPECTED WED. THERE ARE MODEL DIFFERENCES IN THE HANDLING OF CLOSED LOW TOWARD THE END OF THE WEEK. ECMWF NOW MOVES CLOSED LOW BACK SWD ACROSS NEW ENG BUT THIS IS THE OUTLIER AS GFS/UKMET/GGEM KEEP LOW WELL TO THE NORTH WITH WEAK HIGH PRESSURE BUILDING IN BY FRI. FOLLOWED CONSENSUS AND WILL HAVE DRY FCST FOR THU/FRI WITH SEASONABLE TEMPS. UPPER VORTEX SETS UP NEAR JAMES BAY FOR THE WEEKEND WITH LONG WAVE TROF ACROSS GT LAKES BUT THERE IS CONSIDERABLE MODEL SPREAD IN THE HANDLING OF SHORTWAVES ROTATING THROUGH. ECMWF/GFS HAVE A STORM FOR THE WEEKEND BUT IT LOOKS TO BE MOSTLY WET. WE WILL HAVE CHC POPS FOR SAT/SUN ALTHOUGH ECMWF DRIES IT OUT FOR SUN. && .AVIATION /16Z MONDAY THROUGH FRIDAY/... TODAY...VFR OCNL CIGS NEAR 7000 FT ALONG WITH RELATIVELY LIGHT SOUTHERLY WINDS. MOST PERSISTENT DECK OF 7000 FT ALONG AND N OF MASS PIKE. SLY GUSTS NEAR 15 KT THIS AFTN. TONIGHT...LOW PRESSURE APPROACHES FROM THE WEST. THIS LOW WILL GRADUALLY SPREAD RAIN ACROSS SOUTHERN NEW ENGLAND FROM WEST TO EAST STARTING THIS EVENING. THE PRECIP MAY NOT MAKE IT TO BOSTON UNTIL AFTER MIDNIGHT. THE NIGHT WILL START WITH VFR CONDITIONS...BUT THEN DETERIORATE TO MVFR THEN POSSIBLY IFR LATE. TUESDAY...IFR CONDITIONS EXPECTED IN RAIN...POSSIBLY HEAVY AT TIMES. LLWS IS LIKELY...ESPECIALLY AT TERMINALS IN RI AND EASTERN MASS AS SOUTHERLY LLJ DEVELOPS. ISOLD TSRA POSSIBLE. ESE SFC WINDS LIKELY GUST 40 KT RI/EASTERN MASS...ESPECIALLY BOSTON AREA 17Z-22Z. LLWS PROBLEM PVD TO MHT EWD. LINGERING MVFR/IFR IN RAIN TUE EVENING ESPECIALLY MHT-BOS-HYA- ACK...IMPROVING TO VFR OVERNIGHT. STRONG SE WINDS POSSIBLE FROM BOS- HYA-ACK TUE EVENING. OUTLOOK...WED THROUGH FRIDAY... MAINLY VFR WED THROUGH FRI. && .MARINE... QUIET DAY TODAY ON THE LOCAL WATERS WITH SUB-SCA CONDITIONS EXPECTED. RELATIVELY LIGHT SOUTHERLY FLOW EXPECTED. LOW PRESSURE APPROACHES TONIGHT. SOUTHERLY FLOW WILL STRENGTHEN MARKEDLY AFTER MIDNIGHT. WENT WITH A GALE WARNING FOR ALL WATERS STARTING AT 06Z TO KEEP THINGS SIMPLE...ALTHOUGH GALES MAY NOT ARRIVE ON NORTHERN WATERS TIL A BIT LATER ON. SOUTHERLY FLOW INCREASES EVEN MORE DURING THE DAY ON TUESDAY. AFTER LOOKING OVER ALL THE AVAILABLE DATA...DECIDED TO GO WITH STRONG GALES ON ALL WATERS INSTEAD OF STORMS. HAVE ALLOWED GUST NR 50 KTS MERR RVR TO NEAR BOSTON HARBOR WATERS TUE AFTN. LOW LEVEL INVERSION CAN INHIBIT BUT PRES GRAD AND TURB MXG MAY ALLOW FOR GST 50KTS....ESP MERR RIVER REGION. HOWEVER...IT/S POSSIBLE THAT WINDS COULD BE SLIGHTLY STRONGER LATER TUESDAY...RESULTING IN A BRIEF PERIOD OF MARGINAL STORM FORCE WINDS. SEAS ON THE OUTER WATERS BUILD UP TO 15 FEET...WOULDN/T BE SURPRISED TO SEE 44008 AND 44018 TOP OUT BETWEEN 15 AND 20 FEET. STRONGEST WINDS BY TUE EVENING WILL BE ACROSS EASTERN WATERS EAST OF CAPE ANN TO CAPE COD WHERE STRONG SE GALES LIKELY INVOF LLJ. GUSTS TO 45 KT POSSIBLE. WINDS WILL SHIFT TO SW AND DECREASE AS OCCLUSION MOVES THROUGH. THIS WILL HAPPEN BY TUE EVENING OVER THE WESTERN WATERS AND AROUND MIDNIGHT EASTERN WATERS. SEAS UP TO 15 FEET OUTER EASTERN WATERS TUE NIGHT. OUTLOOK...TUESDAY NIGHT THROUGH FRIDAY... WINDS WILL BE MAINLY BELOW SCA LEVELS WED THROUGH FRI...MOSTLY FROM A WESTERLY DIRECTION. A PERIOD OF EASTERLY WINDS EXPECTED WED OVER THE EASTERN WATERS. HIGH SEAS WILL PERSIST OVER THE OUTER WATERS THROUGH MUCH OF THE PERIOD. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...HIGH WIND WATCH FROM TUESDAY MORNING THROUGH TUESDAY AFTERNOON FOR MAZ005>007-014>016. NH...HIGH WIND WATCH FROM TUESDAY MORNING THROUGH TUESDAY AFTERNOON FOR NHZ012. RI...NONE. MARINE...GALE WARNING FROM 1 AM TO 6 PM EST TUESDAY FOR ANZ230>237-250- 254-255. && $$ SYNOPSIS...DRAG/EKSTER NEAR TERM...DRAG/EKSTER SHORT TERM...DRAG/EKSTE 1117 LONG TERM...KJC AVIATION...KJC/DRAG/EKSTER 1117 MARINE...KJC/DRAG/EKSTER 1117 ct AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TALLAHASSEE FL 945 AM EST MON NOV 24 2008 .SYNOPSIS... 14Z WATER VAPOR AND H4 RUC ANALYSIS SHOWING AN AMPLIFYING UPPER LEVEL PATTERN ACROSS NORTH AMERICA THIS MORNING. MAIN FEATURE OF NOTE IS A SHARPENING MID/UPPER LEVEL TROUGH ACROSS THE MID-SECTION OF THE COUNTY/MS VALLEY. INITIAL SHORTWAVE ENERGY CURRENTLY DROPPING INTO THE SOUTHERN PLAINS/MS VALLEY IS WELL DEFINED ON WV IMAGERY WITH MARKED DRYING IN ITS WAKE EXPANDING ACROSS OK AND MO. ANOTHER STRONG PIECE OF UPPER LEVEL ENERGY IS DIVING SOUTH OUT OF WESTERN ONTARIO INTO THE GREAT LAKES. THESE TWO FEATURES WILL CONSOLIDATE OVER THE NEXT 12-24 HOURS INTO AN ENERGETIC UPPER LEVEL DISTURBANCE OVER THE GREAT LAKES AND SOUTHWARD TO THE TENNESSEE VALLEY. ON EITHER SIDE OF THIS TROUGH WE FIND LONGWAVE RIDING ALONG BOTH THE EAST AND WEST COASTS. SOUTHERN STREAM MOISTURE FEED IS ALSO SEEN MOVING NORTHEAST ACROSS MEXICO INTO THE SOUTHERN MS VALLEY. LARGE SCALE LIFT ASSOCIATED WITH MID-LEVEL HEIGHT FALLS IS COMBINING WITH THIS UPPER LEVEL MOISTURE AND VIGOROUS WWA IN THE LOWER LEVELS TO PRODUCE WIDESPREAD SHOWERS AND THUNDERSTORMS FROM EASTERN TEXAS TO THE TENNESSEE AND OHIO VALLEYS. IN THE LOWER LEVELS...SURFACE RIDGING FROM THE CAROLINA COAST SOUTHWARD INTO NORTHERN FLORIDA WILL CONTINUE TO WEAKEN AND SLIDE EAST THROUGH THE DAY IN RESPONSE TO THE DEVELOPING SYSTEM TO OUR NORTHWEST AND ASSOCIATED APPROACH OF A COLD FRONT. THIS FRONT IS CURRENTLY LOCATED FROM THE OHIO VALLEY SOUTHWARD INTO THE WESTERN TENNESSEE VALLEY AND INTO THE SOUTHERN MS VALLEY. AS THE UPPER LEVEL TROUGH AND SURFACE COLD FRONT CONTINUE TO APPROACH THROUGH THE DAY WILL EXPECT THE CLOUDS ALREADY IN PLACE ACROSS THE NORTHWEST HALF OF THE FORECAST AREA TO CONTINUE TO EXPAND EASTWARD. HOWEVER THIS MAY BE A SLOWER PROCESS THE FURTHER EAST ONE GETS AND STILL EXPECT TO SEE A GOOD DEAL OF SUN WELL INTO THE AFTERNOON OVER THE SOUTHEASTERN BIG BEND FROM PERRY TO CROSS CITY. VERY GOOD AGREEMENT AMONG THE MODEL SUITES AS TO THE EVOLUTION OF THIS FRONT AND THE UPPER LEVEL DYNAMICS THIS EVENING INTO EARLY TUESDAY MORNING. 850MB THETA-E RIDGE AND ASSOCIATED FORCED ASCENT DOES NOT ARRIVE ACROSS THE FLORIDA PANHANDLE/SOUTHEAST ALABAMA UNTIL LATE THIS AFTERNOON AND EARLY THIS EVENING. ALTHOUGH A STRAY SHOWER CAN NOT BE RULED OUT OVER THIS AREA DURING THE EARLY AND MIDDLE AFTERNOON HOURS...THE BULK OF THE PRECIP WILL HOLD OFF TILL NEAR DARK AND INTO THE EVENING HOURS. SURFACE INSTABILITY IS EXTREMELY LIMITED WITH SREF PROBS OF EVEN 500 J/KG HOLDING BELOW 5% OVER LAND. HOWEVER...THERE IS INITIALLY SOME MARGINAL INSTABILITY ALOFT PROGGED BY GUIDANCE AS SHOWALTER INDICES APPROACH ZERO OVER THE WESTERN ZONES DURING THE EVENING HOURS. WITH THIS IN MIND WOULD NOT BE SURPRISED TO GET A FEW RUMBLES OF THUNDER WITH THE BAND OF SHOWERS...HOWEVER ANY STRONG STORM POTENTIAL APPEAR VERY UNLIKELY. COLD FRONT IS THEN EXPECTED TO STEADILY PUSH SOUTHEAST ACROSS THE AREA THROUGH THE NIGHT AND EXIT THE SOUTHEAST BIG BEND NEAR OR SHORTLY AFTER SUNRISE TUESDAY MORNING. INITIAL SHORTWAVE ENERGY IS PROGGED TO SHEAR OUT RAPIDLY TO THE NORTHEAST AS THE MAIN TROUGH ORGANIZES WELL TO THE NORTH. AS THIS OCCURS THE LARGE SCALE LIFT OVERHEAD ALL BUT COLLAPSES. MOISTURE AXIS BECOMES RATHER STRUNG OUT INTO THE EASTERN HALF OF THE FORECAST ARE AS WELL. WITH ALL THIS IN MIND SHOULD EXPECT A RATHER SOLID LINE OF RAIN/EMBEDDED STORMS OVER THE WEST THIS EVENING TO WEAK AND THIN OUT AS IT MOVES EAST AFTER MIDNIGHT. SHOWALTER INDICES SHOW A LESSENING OF THE ELEVATED INSTABILITY INTO OUR EASTERN ZONES AND WILL NOT BRING THUNDER MENTION EAST OF THE APALACHICOLA RIVER. FAR EASTERN AREA FROM VALDOSTA INTO THE EASTERN FLORIDA BIG BEND MAY ONLY SEE A QUICK LINE OF LIGHTER SHOWERS PASS THROUGH LATE TONIGHT WITH VERY LITTLE IN THE WAY OF ACCUMULATION. ANY LINGERING SHOWERS SHOULD EXIT THE SOUTHEAST FLORIDA BIG BEND SHORTLY AFTER SUNRISE WITH CLOUDS RAPIDLY DECREASING THROUGH THE MORNING. EXPECTING A PARTLY TO MOSTLY SUNNY AFTERNOON ALMOST REGION-WIDE WITH A GUSTY NORTH TO NORTHWEST WIND AND HIGH TEMPS IN THE LOWER TO MIDDLE 60S. && .MARINE... HIGH PRESSURE WEAKENS AND SLIDES EAST INTO THIS EVENING ALLOWING WINDS TO COME AROUND TO THE SOUTHEAST AND EVENTUALLY SOUTH LATER TODAY. COLD FRONT CROSSES THE WATERS FROM WEST TO EAST TONIGHT WITH A SHARP WINDS SHIFT TO THE NORTHWEST AND NORTH. WINDS WILL INCREASE IN THE WAKE OF THE FRONT TO CAUTIONARY LEVELS WITH A PERIOD OF ADVISORY LEVEL WINDS POSSIBLE INTO TUESDAY AFTERNOON. NORTHERLY FLOW WILL REMAIN ELEVATED NEAR CAUTIONARY LEVELS THROUGH TUESDAY NIGHT. WINDS WILL THEN RAPIDLY DIMINISH INTO THE DAYLIGHT HOURS WEDNESDAY AS SURFACE HIGH PRESSURE BUILDS OVER THE NORTHEAST GULF OF MEXICO. THIS HIGH WILL REMAIN IN CONTROL OF THE FORECAST WATERS PROVIDING LIGHT WINDS AND SEAS THROUGH THURSDAY BEFORE THE NEXT SYSTEM BEGINS TO APPROACH FROM THE WEST FOR THE EARLY PART OF THE UPCOMING WEEKEND. && .AVIATION... VFR CIGS (6-12K FT) WILL INCREASE FROM NORTHWEST TO SOUTHEAST TODAY AHEAD OF AN APPROACHING COLD FRONT. SURFACE WINDS WILL QUICKLY VEER FROM EAST-SOUTHEAST TO SOUTH AHEAD OF THE FRONT...BUT WILL REMAIN LESS THAN 10 KT. SCATTERED TO NUMEROUS SHRA WILL AFFECT KDHN BY LATE AFTERNOON OR EARLY EVENING...THEN THE REST OF THE TERMINALS TONIGHT. BRIEF PERIODS OF MVFR VIS/CIGS WILL BE POSSIBLE IN THESE SHRA. && .PRELIMINARY POINT TEMPS/POPS... TALLAHASSEE 68 44 65 31 63 / 20 50 00 00 00 PANAMA CITY 69 48 64 34 64 / 40 60 00 00 00 DOTHAN 66 41 63 31 62 / 50 60 00 00 00 ALBANY 65 42 62 31 59 / 30 60 00 00 00 VALDOSTA 69 43 64 31 63 / 10 50 00 00 00 CROSS CITY 72 48 65 31 65 / 10 30 05 00 00 && .TAE WATCHES/WARNINGS/ADVISORIES... AL...NONE. GA...NONE. FL...FIRE WX WATCH TUE AFTN ALL ZONES. GM...NONE. && $$ AVIATION...FOURNIER SYNOPSIS/UPDATE/MARINE...MROCZKA fl AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL 553 AM CST MON NOV 24 2008 .DISCUSSION... 307 AM CST MAIN FORECAST CHALLENGE REMAINS WITH THE SHORT TERM PERIOD PRECIPITATION TYPE AND WHETHER ANY OF THE POSSIBLE SNOW WILL ACCUMULATE OVER MONDAY MORNINGS RUSH HOUR. THE NAMS WARMER SOLUTION FROM YESTERDAY APPEARS TO HAVE BEEN THE WINNER WITH THIS EVENT AS THE SECONDARY SOUTHERN LOW HAS PROPAGATED INTO EASTERN IOWA LEAVING OUR REGION IN THE WARM SECTOR FOR THE TIME BEING. WITH THE WARM AIR ADVECTION TAKING PLACE...THE LOW LEVEL TEMPERATURE PROFILES HAVE BEEN WELL ABOVE FREEZING WITH AN ACARS SOUNDING OUT OF ORD SHOWING TEMPS UP TO 44F AT 4KFT. TEMPERATURES ACROSS THE REGION REALLY ARENT AS COLD AS YOU WOULD LIKE TO SEE FOR A SNOW EVENT...WHICH IS MAINLY DUE TO FACT THAT THERE ISNT A STRONG HIGH TO OUR NORTH...RATHER ANOTHER SURFACE LOW THAT IS BOGARTING ALL THE COLD AIR. SFC TEMPS ARE IN THE UPPER 20S/LOW 30S BACK IN THE DAKOTAS AND 850MB TEMPS RANGE FROM 0 TO -2 FROM DUBUQUE BACK TO FARGO. ALL IN ALL...FEEL AS THOUGH THIS DOESNT HAVE THE BEST SETUP BUT WITH ENOUGH EVAPORATIVE COOLING AND SLIGHTLY COOLER AIR WRAPPING IN ON THE BACKSIDE OF THIS WEAK LOW THAT SOME VERY WET SNOW WILL REMAIN A POSSIBILITY THIS MORNING...PARTICULARLY FURTHER NORTH UP ALONG THE WISCONSIN BORDER. A FEW OBS HAVE COME IN WITH UNKNOWN PRECIP...BUT THIS AND EVERYWHERE ELSE IN NORTHEAST ILLINOIS AND NORTHWEST INDIANA HAS JUST BEEN RAIN SO FAR THIS MORNING. AS OF 3AM...MOST OF THE SNOW WAS CONFINED TO SOUTHERN WISCONSIN UP TOWARD MSN AND WEST OF THERE. WILL HAVE THE BEST SHOT FOR ANY SNOW THIS MORNING FROM 12-15Z WORKING FROM WEST TO EAST ACROSS THE FORECAST AREA. WILL KEEP SOME VERY MINOR TENTHS OF ACCUMULATION UP ALONG THE WI/IL BORDER SINCE SOIL TEMPS HAVE DROPPED INTO THE 30S WITH THE RECENT COLD SPELL WE HAVE BEEN UNDER MOST OF NOVEMBER. SNOW RATIOS WILL BE VERY LOW...ON THE ORDER OF 9 TO 1 OR LESS WITH THE WETNESS OF THIS SNOW. AS THE TWO SYSTEMS MERGE MONDAY MORNING...THE PRECIP SHOULD COME TO AN END FAIRLY QUICKLY BEFORE 18Z AND SKIES ARE EXPECTED TO CLEAR OUT A BIT AND LET THE SUN OUT IN THE AFTERNOON. THIS SHOULD HELP TEMPERATURES TO BRIEFLY CLIMB UP TO AROUND 40 OR SO. SKIES WILL CLOUD UP AGAIN TOWARD EVENING AS THE CORE OF THE UPPER LOW DIVES DOWN THROUGH WISCONSIN ON INTO NORTHEAST ILLINOIS AND SOUTHERN LAKE MICHIGAN. THIS COLD PUNCH OF AIR ALONG WITH SOME POSITIVE VORTICITY ADVECTION SHOULD PROVIDE ENOUGH FORCING TO SEE SOME SCATTERED FLURRIES OVERNIGHT INTO TUESDAY MORNING. AFTER ALL THIS EXCITEMENT PASSES INTO NEW ENGLAND AND STALLS OUT...OUR REGION WILL BE LEFT IN WEAK NORTHWESTERLY FLOW ALOFT WITH RIDGING AT THE SFC. THIS IS GOOD NEWS FOR ANY TRAVELERS WEDNESDAY NIGHT INTO FRIDAY AS SKIES WILL MAINLY BE CLEAR THROUGH THIS PERIOD AND DRY...ALBEIT SLIGHTLY COLDER THAN NORMAL FOR THIS TIME OF YEAR. HALBACH && .AVIATION... 1200 UTC TAFS...A MIX OF RAIN AND SNOW IS CHANGING OVER TO MOSTLY SNOW THIS MORNING AS EVAPORATIVE COOLING QUICKLY DROPS THE LOWER LEVELS OF THE ATMOSPHERE BELOW FREEZING. ACARS DESCENT SOUNDING INTO ORD AT 11Z DEPICTS THIS WELL. BOTH CIGS AND VSBYS HAVE DROPPED TO IFR OR LIFR AS THE CENTER OF LOW PRESSURE PASSES DIRECTLY OVERHEAD. RUC/NAM/GFS FORECAST SOUNDINGS HAVE RH VALUES DROPPING RAPIDLY BY MID TO LATE MORNING WHICH SUGGESTS CONDITIONS WILL IMPROVE CONSIDERABLY BY MID-DAY...THOUGH A FEW LINGERING SNOW SHOWERS ARE POSSIBLE IN ANY REMAINING LOW STRATUS. WINDS WILL INCREASE THIS EVENING AND OVERNIGHT UNDER THE INFLUENCE OF A TIGHTENING PRESSURE GRADIENT...AND ADDITIONAL RAIN OR SNOW SHOWERS ARE POSSIBLE AS THE BACK END OF THE LOW SPINS ACROSS THE AREA BEFORE MOVING OFF TO THE EAST. LENNING && .MARINE... 326 AM CST A SURFACE LOW MOVING ACROSS NORTHERN ILLINOIS EARLY THIS MORNING WILL PASS ACROSS THE SOUTHERN PORTION OF THE LAKE AND STRENGTHEN ABOUT 10MB BY THIS EVENING AS IT MERGES WITH ANOTHER LOW DROPPING OUT OF CANADA. NORTH TO NORTHWEST GALES ARE EXPECTED TO DEVELOP THIS EVENING AND CONTINUE THROUGH TUESDAY AS THE GRADIENT TIGHTENS BETWEEN THIS FEATURE AND A CENTER OF HIGH PRESSURE MOVING ACROSS THE NORTHERN PLAINS. WINDS WILL DIMINISH TUESDAY EVENING AS THE HIGH PRESSURE MOVES INTO THE UPPER MISSISSIPPI VALLEY. WESTERLY WINDS GENERALLY ARE EXPECTED TO CONTINUE FOR THE REMAINDER OF THE WEEK. LENNING && .LOT WATCHES/WARNINGS/ADVISORIES... IL...NONE. IN...NONE. LM...SMALL CRAFT ADVISORY...LMZ745...NOON MONDAY TO 6 PM MONDAY. GALE WARNING...LMZ080-LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565- LMZ567-LMZ669-LMZ671-LMZ673-LMZ675-LMZ745-LMZ777-LMZ779- LMZ868-LMZ870-LMZ872-LMZ874-LMZ876-LMZ878...6 PM MONDAY TO 6 PM TUESDAY. SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744...NOON MONDAY TO 6 PM TUESDAY. && $$ il AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE MARQUETTE MI 1030 AM EST MON NOV 24 2008 .UPDATE... UPPER LOW CONTINUES TO DROP SOUTHEASTWARD OUT OF WESTERN ONTARIO TOWARDS WESTERN LAKE SUPERIOR THIS MORNING. EVENTUALLY UPPER LOW WILL MERGE WITH S/WV OVER SOUTHERN LAKE MI FORMING BROADER UPPER LOW OVER SOUTHERN GREAT LAKES. WEAK SFC LOW CURRENTLY OVER SOUTHERN LOWER MI WILL MOVE SLOWLY EWD TO SOUTHERN LAKE HURON BY THE END OF THE DAY. BACK EDGE OF LIGHT SNOW FIELD ASSOCIATED WITH THESE FEATURES HAS MOVED INTO LAKE MI. BEST CHANCE FOR LIGHT SNOW THIS AFTERNOON WILL BE EAST OF A MANISTIQUE TO NEWBERRY LINE AND EVEN THERE AMOUNTS SHOULD BE LIGHT. AS MAIN UPPER LOW DROPS SOUTHEASTWARD ACROSS FAR WESTERN LAKE SUPERIOR EXPECT FLURRIES/-SHSN TO ACCOMPANY IT. WITH A SLIGHTLY WESTWARD UPPER LOW TRACK EXPECT BEST CHANCE OF THIS ACTIVITY ACROSS WESTERN UPPER MICHIGAN WITH CENTRAL AREAS REMAINING PRECIP FREE THROUGH MUCH OF THE DAY. 85H TEMPS WILL FALL INTO THE -8 TO -10 RANGE OVER WESTERN LAKE SUPERIOR AND AS WINDS BECOME MORE NORTHWESTERLY DO EXPECT SOME LAKE ENHANCEMENT TO OCCUR IN FAVORABLE UPSLOPE AREAS IN THE WEST. STILL NOT EXPECTING ANYTHING MORE THAN AN INCH OR AT MOST 2 OF ACCUMULATION DURING THE DAY TODAY. OVERALL TEMP FORECAST IS ON TRACK AND WILL NOT MAKE ANY ADJUSTMENTS TO IT. .SYNOPSIS... ISSUED AT 425 AM EST 08Z WATER VAPOR LOOP AND RUC 500MB HEIGHT ANALYSIS SHOWED RIDGING OVER THE WESTERN U.S. INTO SW CANADA...RIDGING IN THE OHIO VALLEY INTO THE EASTERN GREAT LAKES...AND A TROUGH FROM MANITOBA SOUTHWARD INTO THE CENTRAL PLAINS. WITHIN THE TROUGH...AN UPPER LOW IS LOCATED AT THE FAR NORTH END OF LAKE WINNIPEG. THE WARM CONVEYOR BELT AHEAD OF THE UPPER LOW EXTENDS FROM MO ACROSS UPPER MI AND INTO NE ONTARIO. SOME -SN IS FALLING OUT OF THE CONVEYOR BELT OVER THE CENTRAL PORTION OF THE CWA...ALSO IN THE SAME PLACE WHERE BETTER MOISTURE IS BASED ON 00Z RAOBS FROM MPX...COMPARED TO GRB AND APX WHICH REFLECT THE DRIER AIRMASS OVER EASTERN UPPER MI. A DRY SLOT IS EVIDENT ON 11-3.9 U IMAGERY OVER NE MN...BUT FARTHER NW OVER NW MN INTO MANITOBA IS THE COLD CONVEYOR BELT (CCB) CLOUDS ON THE BACK SIDE OF THE UPPER LOW. 850MB TEMPS UNDER THE CCB WERE AROUND -14C BASED ON THE 00Z SOUNDING FROM CYQD...QUITE A BIT COLDER THAN THE -1C AT MPX...-4C AT INL AND -6C AT CWPL. TO THE SW OF UPPER MI ON WATER VAPOR...A SHRTWV IS MOVING THROUGH SRN IA. ASSOCIATED WITH THE SHRTWV IS A 1015MB SFC LOW IN SE IA. A TROUGH EXTENDS NE FROM THE LOW ACROSS CENTRAL UPPER MI...THEN HEADS BACK TO THE NW AS A COLD FRONT WHERE IT CONNECTS UP TO A 1008MB LOW IN FAR NW ONTARIO. && .DISCUSSION... ISSUED AT 425 AM EST MAIN FORECAST CONCERNS ARE THE AMOUNT OF SNOW THE NEXT TWO DAYS... ALONG WITH POTENTIAL FOR FREEZING DRIZZLE. TODAY...UPPER LOW AT THE NORTH END OF LAKE WINNIPEG IS PROGGED TO SLIDE A LITTLE BIT FARTHER WEST COMPARED TO YESTERDAYS 00Z RUNS...MOVING INTO WRN WI AT 00Z TUE. THE BULK OF THE COLD AIR SEEN UPSTREAM AT CYQD WILL STAY UNDER OR TO THE WEST OF THE UPPER LOW. HOWEVER...SOME COOLING IS STILL EXPECTED TO COME INTO UPPER MICHIGAN WITH THE APPROACH OF THE UPPER LOW. NAM/GFS SHOW 850MB TEMPS FALLING TO -8 TO -10C OVER WRN LAKE SUPERIOR...WHICH WOULD BE GOOD ENOUGH FOR LAKE ENHANCED OR PERHAPS EVEN PURE LAKE EFFECT. WITH NW WINDS... IT WOULD SEEM LIKELY FOR SNOW IN WRN UPPER MI...ESPECIALLY IN UPSLOPE AREAS. HAVE RAISED POPS TO DEFINITE IN THE UPSLOPE AREA FROM IWD TO ROCKLAND. SOUNDINGS SUGGEST SNOW TO WATER RATIOS SOMEWHERE AROUND 10 TO 1...DUE TO MAJORITY OF VERTICAL MOTION BELOW THE DENDRITIC SNOW GROWTH ZONE...WHICH WITH A BLEND OF NAM/LOCAL WRF-ARW RUN/GFS FOR QPF RESULTS IN 1 TO 2 INCHES. THE AMOUNT OF COLD AIR CROSSING CENTRAL AND LAKE SUPERIOR IS A LITTLE MORE UNCERTAIN... WITH THE GFS SHOWING -8 TO PERHAPS -10C AT 00Z TUE...COMPARED TO THE NAM AND LOCAL WRF-ARW WHICH HAVE -4 TO -6C. EITHER SCENARIO SEEMS AT LEAST POSSIBLE FOR LAKE ENHANCED PCPN...ESPECIALLY GIVEN THAT THERE WILL BE PLENTY OF MOISTURE AROUND IN THE WARM CONVEYOR BELT AHEAD OF THE UPPER LOW. THE PROBLEM IS THAT THE WARMER SCENARIO WOULD RESULT IN POTENTIAL FOR RAIN TO MIX IN...PARTICULARLY OVER LAKE SUPERIOR AND OVER LAND NEAR THE SUPERIOR SHORELINE. GIVEN 00Z SOUNDING FROM CWPL UPSTREAM WAS -6C...WILL LEAN TOWARDS THE NAM/LOCAL WRF-ARW. THE WARMER SCENARIO ALSO MEANS THAT ANY SNOW THAT FALLS INLAND WILL ALSO BE WETTER WITH SNOW TO WATER RATIOS LESS THAN 10 TO 1. COULD BE AN INCH...PERHAPS TWO OF THIS WET SNOW IN THE EASTERN CWA. THE CENTRAL U.P. LOOKS TO BE MAINLY DRY TODAY...WITH SOME SUN AS THE DRY-SLOT WORKS IN. A FEW -SHSN COULD WORK IN OVER MQT COUNTY OFF OF WRN SUPERIOR IN THE AFTN...BUT THAT IS ABOUT IT FOR CENTRAL UPPER MI. ALTHOUGH COLD AIR IS FLOWING IN...EXPECT HIGHS AGAIN TODAY IN THE 30S...WARMEST SOUTH CENTRAL WITH DOWNSLOPING NW WINDS AND NEAR LAKE SUPERIOR WITH HEAT FLUX OFF THE WARMER WATER. TONIGHT...UPPER LOW MOVES SE INTO OHIO BY 12Z TUE...COMING CLOSE TO PHASING WITH THE SHRTWV CURRENTLY HEADING EAST OUT OF SRN IA. AS A RESULT...THE SFC LOWS THAT ARE CURRENTLY IN NW ONTARIO AND SE IA END UP MERGING TOGETHER INTO A DEEPER 1003 MB LOW NEAR LONDON ONTARIO AT 12Z TUE. THE DEEPENING LOW HELPS TO STRENGTHEN NORTH TO NE WINDS OVER EASTERN LAKE SUPERIOR. NORMALLY THIS WOULD SPELL COLDER AIR MOVING IN. HOWEVER...THE AIR COMING IN IS EITHER JUST AS COOL OR PERHAPS EVEN SLIGHTLY WARMER THAN THE AIR THAT IS IN OVER THE CWA AT 00Z PER 850MB TEMP PROGS. THE REASON IS THAT THE DEEPENING LOW HELPS TO PULL WARMER AIR IN OFF THE ATLANTIC INTO ITS CIRCULATION. SO WITH LITTLE TO NO CHANGE IN 850MB TEMPS...LAKE ENHANCEMENT SHOULD BE THE RULE...POSSIBLY PURE LAKE EFFECT IN THE WRN U.P.. PROBLEM IN THE WRN U.P. COMPARED TO TODAY IS THAT WITH THE DEPARTURE OF THE UPPER LOW...INVERSIONS FALL WITH THE MID-LEVEL HEIGHT RISES. THE QUESTION IS IF THE -10C ISOTHERM DRIES OUT...WHICH WOULD CHANGE THE PCPN FROM SNOW TO FZDZ GIVEN THAT AN UPSLOPING WIND CONTINUES. RIGHT NOW ONLY OUR LOCAL WRF-ARW RUN SHOWS THIS OCCURRING...WHILE THE NAM/GFS SHOW THE -10C ISOTHERM REMAINING MOIST. THEREFORE HAVE DECIDED TO KEEP THE P-TYPE AS SNOW. IN THE CENTRAL AND EAST...INVERSIONS WILL GRADUALLY LOWER AS WELL...BUT NOT AS QUICK. SO CONFIDENCE IS HIGHER THAT THE P-TYPE WILL STAY AS SNOW INLAND FROM LAKE SUPERIOR. AMOUNTS OF SNOW SHOULD NOT BE THAT IMPRESSIVE...MAYBE AN INCH OR TWO GIVEN LOW SNOW TO WATER RATIOS. REGARDING AREAS NEAR THE LAKE...THE WARMER NAM/LOCAL WRF-ARW RUNS SUGGEST HOLDING ON TO A RAIN/SNOW MIX THROUGH AT LEAST 09Z. IF THE PCPN IS GENERALLY LIGHT...THEN MORE OF THE PCPN SHOULD FALL AS RAIN. GIVEN THE WARMER 850MB TEMPS AND PLENTY OF CLOUDS...ALONG WITH A FLOW OF AIR OFF THE WARM LAKE SUPERIOR WATER...TEMPS SHOULD NOT DROP TOO MUCH. COLDEST READINGS EXPECTED IN THE INTERIOR WEST...CLOSEST TO THE COLDEST 850MB AIR...BUT EVEN THESE SHOULD ONLY BE IN THE MID 20S. TUESDAY...UPPER LOW IS PROGGED TO SHIFT INTO NORTH CENTRAL PA BY 00Z WED...WITH THE SFC LOW MOVING TO THE LAKE ONTARIO AREA. THIS ALLOWS A HIGH PRESSURE RIDGE TO BUILD INTO WESTERN UPPER MI BY 00Z...IN ADDITION TO CONTINUED MID-LEVEL HEIGHT RISES THROUGH THE DAY. THE RIDGE SHOULD BRING DRIER AIR IN...LIKELY TO THE WESTERN CWA...ENOUGH TO END PCPN BY EARLY AFTN. HOWEVER...THE CENTRAL AND EASTERN CWA WILL STAY IN LOW CLOUDS TRAPPED UNDER THE LOWERING INVERSION... ENHANCED BY LAKE SUPERIOR GIVEN COOL AIR BELOW THE INVERSION. PCPN TYPE IS VERY TRICKY...AS ALL MODELS SHOW THE -10C LAYER DRYING OUT THROUGH THE DAY. GIVEN A NORTH WIND OVER EASTERN LAKE SUPERIOR...SET UP IS FAVORABLE FOR UPSLOPE. SO WITH LAKE ENHANCEMENT OFF LAKE SUPERIOR AND UPSLOPE FLOW PRODUCING VERTICAL MOTION...SOME PCPN SHOULD OCCUR OUT OF THE CLOUDS. RIGHT NOW HAVE GONE WITH EITHER SNOW SHOWERS OR DZ/FZDZ (FZDZ OVER INLAND AREAS THROUGH THE EARLY AFTN). POPS ARE HIGHEST IN THE UPSLOPE AREAS OF THE NORTH CENTRAL IN THE MORNING...THEN DECREASE IN THE AFTN AS THE DRIER AIR TRIES TO WORK IN. GIVEN CLOUD COVER AND 850MB TEMPS THAT ARE SLIGHTLY COOLER THAN TODAY...HIGHS WILL ALSO END UP SLIGHTLY COOLER. STILL...MOST LOCATIONS SHOULD BE IN THE 30S...WARMEST IN THE DOWNSLOPE AREAS OF THE SOUTH CENTRAL. TUE NIGHT THROUGH THU...PER THE UKMET/NAM/GFS/ECMWF...UPPER MI LOOKS TO BE CAUGHT IN SQUEEZE-PLAY AS THE UPPER LEVEL PATTERN OVER CANADA AND THE NORTHERN U.S. BECOMES BLOCKED. THIS BLOCKING LOOKS TO BE A RESULT OF STRONG RIDGING BUILT UP AHEAD OF THE UPPER LOW TO OUR EAST. IN FACT...MODELS ARE IN GOOD AGREEMENT TAKING THE UPPER LOW BACK TO THE NW DURING THIS PERIOD...BASICALLY PULLED BY THE CURRENT SHRTWV CROSSING SRN IA. WHAT THIS MEANS FOR UPPER MI IS A PERSISTENT CHANCE FOR -SN ACROSS THE EAST HALF OF UPPER MI CLOSER TO THE DEEPER MOISTURE AROUND THE UPPER LOW...WHILE THE WEST HALF OF UPPER MI IS DRY WITH PARTLY CLOUDY SKIES UNDER THE INFLUENCE OF LOW INVERSIONS AND THE SURFACE RIDGE. STILL MAINTAINED THE POSSIBILITY OF SOME DZ/FZDZ OVER THE EASTERN CWA TUE NIGHT SINCE IT DOES NOT APPEAR THAT THE DEEPER MOISTURE WILL MOVE IN UNTIL WED. ANY PCPN LOOKS TO BE LIGHT AT THE CURRENT TIME DUE TO LACK OF SIGNIFICANT MOISTURE WITH THE UPPER LOW. GIVEN THE BLOCKED PATTERN...NO SIGNIFICANT COOLING OR WARMING IS PLANNED. THEREFORE... LOWS AND HIGHS ARE FORECAST TO BE ABOUT THE SAME THROUGH THE PERIOD...IN THE 20S AND 30S RESPECTIVELY. BEYOND THU...NO SIGNIFICANT CHANGES MADE. 00Z ECMWF/GFS/GFS ENSEMBLES ARE ALL IN VERY GOOD AGREEMENT SHOWING THE DEVELOPMENT OF A BROAD TROUGH ACROSS THE GREAT LAKES INTO THE OHIO VALLEY FOR FRI INTO THE WEEKEND. THIS TROUGH IS FORMED BY A COMBINATION OF THE UPPER LOW TO OUR EAST ON THU AND ANOTHER TROUGH DROPPING DOWN OUT OF CENTRAL CANADA. THIS MEANS THAT GRADUAL COOLING WILL OCCUR...COLD ENOUGH TO SET UP PURE LAKE EFFECT BY THE WEEKEND. && .AVIATION (FOR THE 12Z TAF ISSUANCE)... OVERALL...EXPECT MVFR CONDITIONS TO PREVAIL AT KCMX/KSAW THRU THIS FCST PERIOD. WEDGE OF SOMEWHAT DRIER AIR SWEEPING INTO THE AREA AHEAD OF MID/UPPER LOW DROPPING SE TOWARD THE UPPER MIDWEST MAY RESULT IN CLOUDS SCATTERING OUT FOR A WHILE TODAY...BUT CONFIDENCE IS LOW IN DETERMINING A TIME PERIOD WHEN THAT MIGHT OCCUR. OTHERWISE...UPPER LOW DROPPING INTO THE VCNTY WILL LIKELY BRING SOME -SHSN TO KCMX THIS AFTN AND KSAW THIS EVENING. SOME LAKE ENHANCEMENT IS EXPECTED...ESPECIALLY AT KSAW AS CONVERGENT NRLY UPSLOPING FLOW DEVELOPS. MAY SEE IFR CONDITIONS FOR A TIME LATE EVENING INTO THE OVERNIGHT. && .MARINE (FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)... A LOW PRES TROF EXTENDING FROM NORTHERN ONTARIO ACROSS THE UPPER GREAT LAKES TO THE MID MISSISSIPPI RIVER VALLEY WILL CONSOLIDATE INTO A LOW PRES CENTER OVER SRN LAKE HURON THIS EVENING. AS THIS OCCURS...NRLY WINDS WILL BEGIN TO INCREASE ACROSS LAKE SUPERIOR THIS AFTN AND MORE SO THIS EVENING AND OVERNIGHT. EXPECT NRLY WINDS IN THE 20-30KT RANGE TONIGHT WITH THE STRONGEST WINDS OVER THE E HALF OF THE LAKE. IT`S NOT OUT OF THE QUESTION THAT SOME GALE FORCE GUSTS COULD OCCUR...BUT SINCE THERE IS A LACK OF COLD AIR ADVECTION TO INCREASE MIXING...WILL HOLD OFF ON ANY MENTION OF GALES. PROGRESSION OF THE MAIN WEATHER SYSTEMS WILL SLOW TO A CRAWL TUE THRU FRI. WITH LOW PRES TO THE E AND HIGH PRES TO THE W...N TO NW WINDS WILL BE THE RULE TUE THRU FRI WITH THE STRONGEST WINDS REMAINING OVER THE E HALF OF LAKE SUPERIOR. OVERALL...AFTER TUE...WINDS SHOULD GENERALLY BE IN THE 15-25KT RANGE OVER THE E AND 10-20KT OVER THE W. && .MQT WATCHES/WARNINGS/ADVISORIES... UPPER MICHIGAN...NONE. LAKE SUPERIOR...NONE. LAKE MICHIGAN...NONE. && $$ UPDATE...MZ SYNOPSIS/DISCUSSION...AJ AVIATION...ROLFSON MARINE...ROLFSON mi AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE MARQUETTE MI 646 AM EST MON NOV 24 2008 UPDATED AVIATION DISCUSSION FOR 12Z TAF ISSUANCE .SYNOPSIS... ISSUED AT 425 AM EST 08Z WATER VAPOR LOOP AND RUC 500MB HEIGHT ANALYSIS SHOWED RIDGING OVER THE WESTERN U.S. INTO SW CANADA...RIDGING IN THE OHIO VALLEY INTO THE EASTERN GREAT LAKES...AND A TROUGH FROM MANITOBA SOUTHWARD INTO THE CENTRAL PLAINS. WITHIN THE TROUGH...AN UPPER LOW IS LOCATED AT THE FAR NORTH END OF LAKE WINNIPEG. THE WARM CONVEYOR BELT AHEAD OF THE UPPER LOW EXTENDS FROM MO ACROSS UPPER MI AND INTO NE ONTARIO. SOME -SN IS FALLING OUT OF THE CONVEYOR BELT OVER THE CENTRAL PORTION OF THE CWA...ALSO IN THE SAME PLACE WHERE BETTER MOISTURE IS BASED ON 00Z RAOBS FROM MPX...COMPARED TO GRB AND APX WHICH REFLECT THE DRIER AIRMASS OVER EASTERN UPPER MI. A DRY SLOT IS EVIDENT ON 11-3.9 U IMAGERY OVER NE MN...BUT FARTHER NW OVER NW MN INTO MANITOBA IS THE COLD CONVEYOR BELT (CCB) CLOUDS ON THE BACK SIDE OF THE UPPER LOW. 850MB TEMPS UNDER THE CCB WERE AROUND -14C BASED ON THE 00Z SOUNDING FROM CYQD...QUITE A BIT COLDER THAN THE -1C AT MPX...-4C AT INL AND -6C AT CWPL. TO THE SW OF UPPER MI ON WATER VAPOR...A SHRTWV IS MOVING THROUGH SRN IA. ASSOCIATED WITH THE SHRTWV IS A 1015MB SFC LOW IN SE IA. A TROUGH EXTENDS NE FROM THE LOW ACROSS CENTRAL UPPER MI...THEN HEADS BACK TO THE NW AS A COLD FRONT WHERE IT CONNECTS UP TO A 1008MB LOW IN FAR NW ONTARIO. && .DISCUSSION... ISSUED AT 425 AM EST MAIN FORECAST CONCERNS ARE THE AMOUNT OF SNOW THE NEXT TWO DAYS... ALONG WITH POTENTIAL FOR FREEZING DRIZZLE. TODAY...UPPER LOW AT THE NORTH END OF LAKE WINNIPEG IS PROGGED TO SLIDE A LITTLE BIT FARTHER WEST COMPARED TO YESTERDAYS 00Z RUNS...MOVING INTO WRN WI AT 00Z TUE. THE BULK OF THE COLD AIR SEEN UPSTREAM AT CYQD WILL STAY UNDER OR TO THE WEST OF THE UPPER LOW. HOWEVER...SOME COOLING IS STILL EXPECTED TO COME INTO UPPER MICHIGAN WITH THE APPROACH OF THE UPPER LOW. NAM/GFS SHOW 850MB TEMPS FALLING TO -8 TO -10C OVER WRN LAKE SUPERIOR...WHICH WOULD BE GOOD ENOUGH FOR LAKE ENHANCED OR PERHAPS EVEN PURE LAKE EFFECT. WITH NW WINDS... IT WOULD SEEM LIKELY FOR SNOW IN WRN UPPER MI...ESPECIALLY IN UPSLOPE AREAS. HAVE RAISED POPS TO DEFINITE IN THE UPSLOPE AREA FROM IWD TO ROCKLAND. SOUNDINGS SUGGEST SNOW TO WATER RATIOS SOMEWHERE AROUND 10 TO 1...DUE TO MAJORITY OF VERTICAL MOTION BELOW THE DENDRITIC SNOW GROWTH ZONE...WHICH WITH A BLEND OF NAM/LOCAL WRF-ARW RUN/GFS FOR QPF RESULTS IN 1 TO 2 INCHES. THE AMOUNT OF COLD AIR CROSSING CENTRAL AND LAKE SUPERIOR IS A LITTLE MORE UNCERTAIN... WITH THE GFS SHOWING -8 TO PERHAPS -10C AT 00Z TUE...COMPARED TO THE NAM AND LOCAL WRF-ARW WHICH HAVE -4 TO -6C. EITHER SCENARIO SEEMS AT LEAST POSSIBLE FOR LAKE ENHANCED PCPN...ESPECIALLY GIVEN THAT THERE WILL BE PLENTY OF MOISTURE AROUND IN THE WARM CONVEYOR BELT AHEAD OF THE UPPER LOW. THE PROBLEM IS THAT THE WARMER SCENARIO WOULD RESULT IN POTENTIAL FOR RAIN TO MIX IN...PARTICULARLY OVER LAKE SUPERIOR AND OVER LAND NEAR THE SUPERIOR SHORELINE. GIVEN 00Z SOUNDING FROM CWPL UPSTREAM WAS -6C...WILL LEAN TOWARDS THE NAM/LOCAL WRF-ARW. THE WARMER SCENARIO ALSO MEANS THAT ANY SNOW THAT FALLS INLAND WILL ALSO BE WETTER WITH SNOW TO WATER RATIOS LESS THAN 10 TO 1. COULD BE AN INCH...PERHAPS TWO OF THIS WET SNOW IN THE EASTERN CWA. THE CENTRAL U.P. LOOKS TO BE MAINLY DRY TODAY...WITH SOME SUN AS THE DRY-SLOT WORKS IN. A FEW -SHSN COULD WORK IN OVER MQT COUNTY OFF OF WRN SUPERIOR IN THE AFTN...BUT THAT IS ABOUT IT FOR CENTRAL UPPER MI. ALTHOUGH COLD AIR IS FLOWING IN...EXPECT HIGHS AGAIN TODAY IN THE 30S...WARMEST SOUTH CENTRAL WITH DOWNSLOPING NW WINDS AND NEAR LAKE SUPERIOR WITH HEAT FLUX OFF THE WARMER WATER. TONIGHT...UPPER LOW MOVES SE INTO OHIO BY 12Z TUE...COMING CLOSE TO PHASING WITH THE SHRTWV CURRENTLY HEADING EAST OUT OF SRN IA. AS A RESULT...THE SFC LOWS THAT ARE CURRENTLY IN NW ONTARIO AND SE IA END UP MERGING TOGETHER INTO A DEEPER 1003 MB LOW NEAR LONDON ONTARIO AT 12Z TUE. THE DEEPENING LOW HELPS TO STRENGTHEN NORTH TO NE WINDS OVER EASTERN LAKE SUPERIOR. NORMALLY THIS WOULD SPELL COLDER AIR MOVING IN. HOWEVER...THE AIR COMING IN IS EITHER JUST AS COOL OR PERHAPS EVEN SLIGHTLY WARMER THAN THE AIR THAT IS IN OVER THE CWA AT 00Z PER 850MB TEMP PROGS. THE REASON IS THAT THE DEEPENING LOW HELPS TO PULL WARMER AIR IN OFF THE ATLANTIC INTO ITS CIRCULATION. SO WITH LITTLE TO NO CHANGE IN 850MB TEMPS...LAKE ENHANCEMENT SHOULD BE THE RULE...POSSIBLY PURE LAKE EFFECT IN THE WRN U.P.. PROBLEM IN THE WRN U.P. COMPARED TO TODAY IS THAT WITH THE DEPARTURE OF THE UPPER LOW...INVERSIONS FALL WITH THE MID-LEVEL HEIGHT RISES. THE QUESTION IS IF THE -10C ISOTHERM DRIES OUT...WHICH WOULD CHANGE THE PCPN FROM SNOW TO FZDZ GIVEN THAT AN UPSLOPING WIND CONTINUES. RIGHT NOW ONLY OUR LOCAL WRF-ARW RUN SHOWS THIS OCCURRING...WHILE THE NAM/GFS SHOW THE -10C ISOTHERM REMAINING MOIST. THEREFORE HAVE DECIDED TO KEEP THE P-TYPE AS SNOW. IN THE CENTRAL AND EAST...INVERSIONS WILL GRADUALLY LOWER AS WELL...BUT NOT AS QUICK. SO CONFIDENCE IS HIGHER THAT THE P-TYPE WILL STAY AS SNOW INLAND FROM LAKE SUPERIOR. AMOUNTS OF SNOW SHOULD NOT BE THAT IMPRESSIVE...MAYBE AN INCH OR TWO GIVEN LOW SNOW TO WATER RATIOS. REGARDING AREAS NEAR THE LAKE...THE WARMER NAM/LOCAL WRF-ARW RUNS SUGGEST HOLDING ON TO A RAIN/SNOW MIX THROUGH AT LEAST 09Z. IF THE PCPN IS GENERALLY LIGHT...THEN MORE OF THE PCPN SHOULD FALL AS RAIN. GIVEN THE WARMER 850MB TEMPS AND PLENTY OF CLOUDS...ALONG WITH A FLOW OF AIR OFF THE WARM LAKE SUPERIOR WATER...TEMPS SHOULD NOT DROP TOO MUCH. COLDEST READINGS EXPECTED IN THE INTERIOR WEST...CLOSEST TO THE COLDEST 850MB AIR...BUT EVEN THESE SHOULD ONLY BE IN THE MID 20S. TUESDAY...UPPER LOW IS PROGGED TO SHIFT INTO NORTH CENTRAL PA BY 00Z WED...WITH THE SFC LOW MOVING TO THE LAKE ONTARIO AREA. THIS ALLOWS A HIGH PRESSURE RIDGE TO BUILD INTO WESTERN UPPER MI BY 00Z...IN ADDITION TO CONTINUED MID-LEVEL HEIGHT RISES THROUGH THE DAY. THE RIDGE SHOULD BRING DRIER AIR IN...LIKELY TO THE WESTERN CWA...ENOUGH TO END PCPN BY EARLY AFTN. HOWEVER...THE CENTRAL AND EASTERN CWA WILL STAY IN LOW CLOUDS TRAPPED UNDER THE LOWERING INVERSION... ENHANCED BY LAKE SUPERIOR GIVEN COOL AIR BELOW THE INVERSION. PCPN TYPE IS VERY TRICKY...AS ALL MODELS SHOW THE -10C LAYER DRYING OUT THROUGH THE DAY. GIVEN A NORTH WIND OVER EASTERN LAKE SUPERIOR...SET UP IS FAVORABLE FOR UPSLOPE. SO WITH LAKE ENHANCEMENT OFF LAKE SUPERIOR AND UPSLOPE FLOW PRODUCING VERTICAL MOTION...SOME PCPN SHOULD OCCUR OUT OF THE CLOUDS. RIGHT NOW HAVE GONE WITH EITHER SNOW SHOWERS OR DZ/FZDZ (FZDZ OVER INLAND AREAS THROUGH THE EARLY AFTN). POPS ARE HIGHEST IN THE UPSLOPE AREAS OF THE NORTH CENTRAL IN THE MORNING...THEN DECREASE IN THE AFTN AS THE DRIER AIR TRIES TO WORK IN. GIVEN CLOUD COVER AND 850MB TEMPS THAT ARE SLIGHTLY COOLER THAN TODAY...HIGHS WILL ALSO END UP SLIGHTLY COOLER. STILL...MOST LOCATIONS SHOULD BE IN THE 30S...WARMEST IN THE DOWNSLOPE AREAS OF THE SOUTH CENTRAL. TUE NIGHT THROUGH THU...PER THE UKMET/NAM/GFS/ECMWF...UPPER MI LOOKS TO BE CAUGHT IN SQUEEZE-PLAY AS THE UPPER LEVEL PATTERN OVER CANADA AND THE NORTHERN U.S. BECOMES BLOCKED. THIS BLOCKING LOOKS TO BE A RESULT OF STRONG RIDGING BUILT UP AHEAD OF THE UPPER LOW TO OUR EAST. IN FACT...MODELS ARE IN GOOD AGREEMENT TAKING THE UPPER LOW BACK TO THE NW DURING THIS PERIOD...BASICALLY PULLED BY THE CURRENT SHRTWV CROSSING SRN IA. WHAT THIS MEANS FOR UPPER MI IS A PERSISTENT CHANCE FOR -SN ACROSS THE EAST HALF OF UPPER MI CLOSER TO THE DEEPER MOISTURE AROUND THE UPPER LOW...WHILE THE WEST HALF OF UPPER MI IS DRY WITH PARTLY CLOUDY SKIES UNDER THE INFLUENCE OF LOW INVERSIONS AND THE SURFACE RIDGE. STILL MAINTAINED THE POSSIBILITY OF SOME DZ/FZDZ OVER THE EASTERN CWA TUE NIGHT SINCE IT DOES NOT APPEAR THAT THE DEEPER MOISTURE WILL MOVE IN UNTIL WED. ANY PCPN LOOKS TO BE LIGHT AT THE CURRENT TIME DUE TO LACK OF SIGNIFICANT MOISTURE WITH THE UPPER LOW. GIVEN THE BLOCKED PATTERN...NO SIGNIFICANT COOLING OR WARMING IS PLANNED. THEREFORE... LOWS AND HIGHS ARE FORECAST TO BE ABOUT THE SAME THROUGH THE PERIOD...IN THE 20S AND 30S RESPECTIVELY. BEYOND THU...NO SIGNIFICANT CHANGES MADE. 00Z ECMWF/GFS/GFS ENSEMBLES ARE ALL IN VERY GOOD AGREEMENT SHOWING THE DEVELOPMENT OF A BROAD TROUGH ACROSS THE GREAT LAKES INTO THE OHIO VALLEY FOR FRI INTO THE WEEKEND. THIS TROUGH IS FORMED BY A COMBINATION OF THE UPPER LOW TO OUR EAST ON THU AND ANOTHER TROUGH DROPPING DOWN OUT OF CENTRAL CANADA. THIS MEANS THAT GRADUAL COOLING WILL OCCUR...COLD ENOUGH TO SET UP PURE LAKE EFFECT BY THE WEEKEND. && .AVIATION (FOR THE 12Z TAF ISSUANCE)... OVERALL...EXPECT MVFR CONDITIONS TO PREVAIL AT KCMX/KSAW THRU THIS FCST PERIOD. WEDGE OF SOMEWHAT DRIER AIR SWEEPING INTO THE AREA AHEAD OF MID/UPPER LOW DROPPING SE TOWARD THE UPPER MIDWEST MAY RESULT IN CLOUDS SCATTERING OUT FOR A WHILE TODAY...BUT CONFIDENCE IS LOW IN DETERMINING A TIME PERIOD WHEN THAT MIGHT OCCUR. OTHERWISE...UPPER LOW DROPPING INTO THE VCNTY WILL LIKELY BRING SOME -SHSN TO KCMX THIS AFTN AND KSAW THIS EVENING. SOME LAKE ENHANCEMENT IS EXPECTED...ESPECIALLY AT KSAW AS CONVERGENT NRLY UPSLOPING FLOW DEVELOPS. MAY SEE IFR CONDITIONS FOR A TIME LATE EVENING INTO THE OVERNIGHT. && .MARINE (FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)... A LOW PRES TROF EXTENDING FROM NORTHERN ONTARIO ACROSS THE UPPER GREAT LAKES TO THE MID MISSISSIPPI RIVER VALLEY WILL CONSOLIDATE INTO A LOW PRES CENTER OVER SRN LAKE HURON THIS EVENING. AS THIS OCCURS...NRLY WINDS WILL BEGIN TO INCREASE ACROSS LAKE SUPERIOR THIS AFTN AND MORE SO THIS EVENING AND OVERNIGHT. EXPECT NRLY WINDS IN THE 20-30KT RANGE TONIGHT WITH THE STRONGEST WINDS OVER THE E HALF OF THE LAKE. IT`S NOT OUT OF THE QUESTION THAT SOME GALE FORCE GUSTS COULD OCCUR...BUT SINCE THERE IS A LACK OF COLD AIR ADVECTION TO INCREASE MIXING...WILL HOLD OFF ON ANY MENTION OF GALES. PROGRESSION OF THE MAIN WEATHER SYSTEMS WILL SLOW TO A CRAWL TUE THRU FRI. WITH LOW PRES TO THE E AND HIGH PRES TO THE W...N TO NW WINDS WILL BE THE RULE TUE THRU FRI WITH THE STRONGEST WINDS REMAINING OVER THE E HALF OF LAKE SUPERIOR. OVERALL...AFTER TUE...WINDS SHOULD GENERALLY BE IN THE 15-25KT RANGE OVER THE E AND 10-20KT OVER THE W. && .MQT WATCHES/WARNINGS/ADVISORIES... UPPER MICHIGAN...NONE. LAKE SUPERIOR...NONE. LAKE MICHIGAN...NONE. && $$ SYNOPSIS/DISCUSSION...AJ AVIATION...ROLFSON MARINE...ROLFSON mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 329 PM EST MON NOV 24 2008 .SYNOPSIS... LOW PRESSURE WILL SPREAD PRECIPITATION INTO NEW ENGLAND TONIGHT AND TUESDAY...MOSTLY IN THE FORM OF RAIN WHICH WILL BE HEAVY AT TIMES. THE SYSTEM WILL ALSO BRING STRONG WINDS TO MUCH OF THE COASTAL PLAIN ON TUESDAY. COOLER AND MAINLY DRY WEATHER WILL RETURN WEDNESDAY THROUGH AT LEAST FRIDAY AFTERNOON...BEFORE ANOTHER SYSTEM MAY BRING SOME RAIN TO THE REGION LATE FRIDAY NIGHT AND SATURDAY. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/... 915 AND 1015 AM MINOR ADJUSTMENTS TO GRID TRENDS THIS MORNING. RUC 13 VIA TSECS HAS THE BEST HANDLE ON CURRENT AND NEAR TERM CLOUD BANDS NR 7000 FT. GRIDS MODIFIED. SURFACE HIGH PRESSURE WILL GRADUALLY MOVE OFF THE COAST TODAY AS LOW PRESSURE APPROACHES FROM THE WEST. THE RESULT WILL BE INCREASING HIGH CLOUDINESS...BUT ANY PRECIPITATION WILL HOLD OFF UNTIL THIS EVENING OR TONIGHT. IN FACT...WE MAY SEE A GOOD AMOUNT OF FILTERED SUNSHINE TODAY. TEMPERATURES WILL BE WARMER THAN THEY HAVE BEEN OVER THE LAST SEVERAL DAYS AS THE FLOW GOES SOUTH AND THE AIRMASS WARMS. EVEN STILL...HIGH TEMPS WILL TOP OUT AROUND 5 DEGREES BELOW NORMAL. MAXES WERE DERIVED FROM A BLEND OF NAM 2M TEMPS AND MAVMOSGUIDE...WITH SLIGHTLY MORE WEIGHT GIVEN TO THE MOS. && .SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/... 1110 AM... ISSUING HIGH WIND WATCH BOSTON TO MANCHESTER AND POINTS EAST TO CAPE ANN. SE WIND HIGH WIND CASES IN OUR CLIMO ARE RARE BUT MARGINAL HIGH WIND CASE ENVISIONED PER MODEL PRES CHANGES... LAPSE RATES...BL AND 925 MB WINDS BOTH 12Z GFS/NAM. NAM BL WINDS ARE UP TO 38 KTS NOW AT CONCORD. THAT SEEMS A LITTLE HIGH BUT PER COLLAB WITH GYX...ADDED ASH TO MHT. GREATEST CONFIDENCE IN SIGNIFICANT POWER OUTAGES AND SUSTAINED WIND 40 OR GREATER IS MQE AND BOS TO LWM REGION EWD. MAY SEE GUST 60 KTS AT MQE. WIND ADVY WILL BE ISSUED REMAINDER I95 REGION OF RI AND MASS AT 4PM. REMAINDER BLO FROM 4AM... CLOUDS WILL RAPIDLY INCREASE EARLY THIS EVENING AS LOW PRESSURE CONTINUES TO APPROACH. THE PRECIPITATION SHIELD WILL ARRIVE FROM WEST TO EAST...STARTING IN THE CT VALLEY SOMETIME BETWEEN 02Z AND 06Z...THEN SPREADING EASTWARD FROM THERE. THE DOMINANT PRECIPITATION TYPE WILL BE RAIN...ALTHOUGH A PORTION OF NW MASS AND SW NH MAY SEE A BRIEF PERIOD OF LIGHT SNOW AT THE START. NO ACCUMULATION IS EXPECTED. ATTM...THE THINKING IS THAT THE SFC TEMPS WILL WARM UP ENOUGH TO ALLOW FOR MUCH IN THE WAY OF FREEZING RAIN IF ANY AT ALL. IT WOULD BE EXTREMELY ISOLATED AT BEST. WENT WITH CATEGORICAL POPS FOR ALL ZONES BY LATE AT NIGHT. TEMPS WILL SLOWLY RISE OVERNIGHT AS THE LOW LEVEL JET GETS GOING. RAIN WILL BECOME HEAVY AT TIMES TUESDAY MORNING...ESPECIALLY THE WESTERN HALF OF THE CWA...BEFORE SHIFTING TO THE EASTERN HALF DURING THE AFTERNOON. CATEGORICAL POPS FOR ALL AREAS. BEST GUESS AT THIS TIME IS THAT A GENERAL .75 TO 1.5 INCHES OF RAIN WILL FALL...WITH LOCALLY HIGHER AMOUNTS. THIS SHOULDN/T CAUSE WIDESPREAD FLOODING PROBLEMS. HOWEVER...WE/LL LIKELY SEE THE NORMAL MINOR URBAN/POOR DRAINAGE FLOODING AT TIMES. WENT WITH A SLIGHT CHANCE OF THUNDER...MAINLY FOR SOUTHERN AND EASTERN ZONES...AS WEAK INSTABILITY MAY DEVELOP AS THE LLJ PUMPS NORTHWARD A DECENT PLUME OF THETA-E. THE BIGGEST CONCERN FOR TUESDAY MAY BE THE WINDS...AS A 65 KNOT SOUTHERLY LOW LEVEL JET DEVELOPS. THIS MAY LEAD TO SPEEDS OF WIND ADVISORY CRITERIA IF NOT ISOLD MARGINAL HWW CRITERIA TUESDAY AFTERNOON ALONG THE SOUTH COAST AND POSSIBLY THE REST OF EASTERN MASS. THE HIGHER TERRAIN MAY BE AFFECTED AS WELL. SUBSEQUENT SHIFTS MAY HAVE TO CONSIDER ADVISORIES/WATCHES/WARNINGS. ANY CONVECTION COULD BRING DOWN ISOLD STRONG WIND GUSTS AS WELL...ESPECIALLY IF SFC TEMPS REALLY WARM UP. THERE MAY BE A 1-2 FOOT SURGE ON THE SOUTH COAST BAYS WITH THE STRONG SOUTHERLY LLJ....BUT TIDES ARE LOW AND PRESSURE FALLS NOT OVERLY IMPRESSIVE. THEREFORE...NO COASTAL FLOODING PROBLEMS ARE EXPECTED AT THIS TIME. MODEL MAX TEMPS FOR TUESDAY LOOKED TOO LOW. THESE SOUTHERLY LLJ EVENTS ALMOST ALWAYS PRODUCE HIGHER SURFACE TEMPS THAN WHAT MOS AND EVEN MODEL 2M TEMPS INDICATE. WENT FOR MID 50S ACROSS EASTERN MASS/RI AND PORTIONS OF CT. COOLER TEMPS /40S - LOW 50S/ WILL BE FOUND ACROSS THE INTERIOR ALTHOUGH IT/S QUITE POSSIBLE THAT THEY WILL NEED TO BE RAISED AS WELL. OCCLUSION WILL BE MOVING ACROSS THE REGION EARLY TUE EVENING. NAM IS THE SLOWEST MOVING THE OCCLUSION THROUGH AND BRINGS A SLUG OF HEAVY RAIN TO E MA INTO SE NH AT THE NOSE OF A PERSISTENT SELY LLJ. CONSENSUS AMONG OTHER MODELS INCLUDING GFS FAVORS A FASTER SOLUTION SO WE LEANED TOWARD GFS WHICH LIFTS THE HEAVIER RAFL NORTH AND EAST OF SNE BY TUE EVENING. HOWEVER...SOME RAIN WILL LIKELY LINGER ACROSS NE ZONES NEAR THE NOSE OF THE LLJ SO WE WILL HAVE LIKELY TO CATEGORICAL POPS TUE EVENING FROM SW NH THROUGH E MA WITH LOWER POPS FURTHER SW AS DRY SLOT MOVES IN. ALSO...GFS INSTABILITY PARAMETERS SUGGEST ISOLD ELEVATED THUNDER POSSIBLE E MA THROUGH SE NH. TREND TUE NIGHT WILL BE FOR DECREASING POPS AS THE DRY SLOT MOVES THROUGH. WIND MAY STILL BE A CONCERN TUE EVENING FROM CAPE COD THROUGH CAPE ANN WHICH WILL BE CLOSEST TO THE LLJ AND WILL HAVE HIGHER GUSTS IN THIS REGION. COLDER AIR WILL BE SLOW TO MOVE IN TUE NIGHT AS UPPER LOW REMAINS TO THE NW WITH SOUTHERLY FLOW ALOFT. MIN TEMPS WILL RANGE FROM UPPER 20S FAR NW TO MID/UPPER 30S COASTAL PLAIN. && .LONG TERM /WEDNESDAY THROUGH MONDAY/... WEDNESDAY... THE DRY SLOT WILL HAVE WRAPPED INTO SOUTHERN NEW ENGLAND BY EARLY WEDNESDAY MORNING. WE EXPECT PARTLY SUNNY SKIES IN THE MORNING...BUT STEEP LAPSE RATES WITH THE COLD AIR ALOFT SHOULD RESULT IN LOTS OF DIURNAL CUMULUS DEVELOPING BY AFTERNOON AND GENERALLY MOSTLY CLOUDY SKIES. THE UPPER LEVEL LOW LOOKS TO REMAIN WELL TO OUR NORTHWEST...SO WE EXPECT MAINLY A DRY DAY. HOWEVER...WILL MAINTAIN A SLIGHT CHANCE POP FOR A BRIEF PASSING SHOWER/SPRINKLE IN THE AFTERNOON. IT COULD BE IN THE FORM OF A WET SNOW SHOWER/FLURRY IN THE HIGHEST TERRAIN...BUT NO ACCUMULATION EXPECTED WITH TEMPERATURES ABOVE FREEZING. HIGH TEMPERATURES SHOULD MAINLY BE IN THE MID TO UPPER 40S...WITH READINGS A BIT COOLER IN THE HIGHER TERRAIN. WEDNESDAY NIGHT... AN ISOLATED SHOWER/SPRINKLE WILL STILL BE POSSIBLE IN THE EARLY EVENING...BUT OTHERWISE PARTLY TO MOSTLY CLOUDY SKIES FOR MUCH OF THE NIGHT. THEREFORE...WE LEANED TOWARDS THE WARMER MET GUIDANCE WITH A FAIR AMOUNT OF CLOUDS EXPECTED OVERNIGHT. LOWS SHOULD MAINLY BE IN THE UPPER 20S AND LOWER 30S ALTHOUGH IT WILL BE A BIT WARMER IN THE URBAN HEAT ISLAND OF BOSTON. THURSDAY... SHOULD SEE PARTIAL SUNSHINE...BUT ANOTHER DAY OF DIURNAL AFTERNOON CUMULUS EXPECTED...PARTICULARLY ACROSS THE INTERIOR WITH A POCKET OF COLD AIR ALOFT. WILL INCLUDE A SLIGHT CHANCE POP FOR PERHAPS A BRIEF INSTABILITY PASSING RAIN/SNOW SHOWER ACROSS THE DISTANT INTERIOR...BUT CAN NOT SEE MUCH MORE THAN THAT. HIGHS WILL MAINLY BE IN THE 40S. FRIDAY AND SATURDAY... CLOUDS SHOULD INCREASE DURING THE DAY FRIDAY OUT AHEAD OF THE NEXT LOW PRESSURE SYSTEM. THE GFS/CANADIAN HAVE PRECIPITATION OVER SPREADING MOST OF THE REGION LATE FRIDAY NIGHT...WHILE THE GFS ENSEMBLES ARE A BIT SLOWER AND HAVE THE BULK OF THE ACTION SATURDAY AND SATURDAY NIGHT. THIS FAR OUT THERE IS PLENTY OF UNCERTAINTY ON THE TIMING SO WILL CARRY CHANCE POPS FRIDAY NIGHT THROUGH SATURDAY NIGHT. BASED ON THE EXPECTED TRACK OF THE SYSTEM...WE EXPECT MAINLY RAIN FROM THIS SYSTEM. HOWEVER...CAN NOT RULE OUT A BRIEF PERIOD OF SNOW OR ICE ACROSS THE DISTANT INTERIOR AT THE ONSET. THE ECMWF SEEMS TO BE A BIT OF AN OUTLIER DEVELOPING THE WAVE FURTHER EAST AND HAS LITTLE IF ANY PRECIPITATION FROM THIS SYSTEM. WHILE WE DO NOT EXPECT A LOT OF PRECIPITATION WITH THIS SYSTEM...WOULD FAVOR MOST OF THE REGION SEEING AT LEAST SOME RAIN. SUNDAY AND MONDAY... BASED ON THE LATEST MODELS DRY AND CHILLY WEATHER WILL WORK BACK INTO THE REGION ON SUNDAY. THE GFS IS DRY ON MONDAY AND MONDAY NIGHT BUT ITS ENSEMBLES AND THE 12Z ECMWF INDICATE THE THREAT OF MORE PRECIPITATION SOMETIME MONDAY OR MONDAY NIGHT. LOW CONFIDENCE THIS FAR OUT...BUT THIS SYSTEM MAY BRING SOME WINTRY WEATHER TO PORTIONS OF OUR REGION WITH A CHILLY AIRMASS IN PLACE. THEREFORE...WILL CARRY SOME CHANCE POPS MONDAY AND MONDAY NIGHT BUT AGAIN THERE IS LOW CONFIDENCE THIS FAR OUT. && .AVIATION /21Z MONDAY THROUGH SATURDAY/... TODAY...VFR OCNL CIGS NEAR 8000 FT ALONG WITH RELATIVELY LIGHT SOUTHERLY WINDS. TONIGHT...ADVANCING LOW PRESSURE WILL BRING GRADUALLY LOWERING CEILINGS...FOLLOWED BY RAIN SPREADING ACROSS SOUTHERN NEW ENGLAND FROM WEST TO EAST LATER THIS EVENING. THE NIGHT WILL START WITH VFR CONDITIONS...BUT THEN DETERIORATE TO MVFR...THEN IFR/LIFR LATE. TUESDAY...IFR TO LIFR CONDITIONS EXPECTED IN RAIN...POSSIBLY HEAVY AT TIMES. LLWS IS LIKELY...ESPECIALLY AT TERMINALS IN RI AND EASTERN MASS AS SOUTHEASTERLY LLJ DEVELOPS. ISOLD TSRA POSSIBLE. ESE SFC WINDS LIKELY GUST 40 KT RI/EASTERN MASS...ESPECIALLY BOSTON AREA 15Z-21Z. LLWS EXPECTED FROM PVD TO MHT AND EAST. LINGERING MVFR/IFR IN RAIN TUE EVENING ESPECIALLY MHT-BOS-HYA- ACK...IMPROVING TO VFR OVERNIGHT. RAPIDLY DIMINISHING WINDS EXPECTED. OUTLOOK...WEDNESDAY THROUGH SATURDAY... WEDNESDAY THROUGH FRIDAY...MAINLY VFR. FRIDAY NIGHT THROUGH SATURDAY NIGHT...WE WILL PROBABLY SEE A PERIOD OF MVFR/IFR CONDITIONS IN SOME RAIN SHOWERS OVER THIS PERIOD. TIMING REMAINS UNCERTAIN THROUGH. && .MARINE... QUIET DAY TODAY ON THE LOCAL WATERS WITH SUB-SCA CONDITIONS EXPECTED. RELATIVELY LIGHT SOUTHERLY FLOW EXPECTED. LOW PRESSURE APPROACHES TONIGHT. SOUTHERLY FLOW WILL STRENGTHEN MARKEDLY AFTER MIDNIGHT. WENT WITH A GALE WARNING FOR ALL WATERS STARTING AT 06Z TO KEEP THINGS SIMPLE...ALTHOUGH GALES MAY NOT ARRIVE ON NORTHERN WATERS TIL A BIT LATER ON. SOUTHERLY FLOW INCREASES EVEN MORE DURING THE DAY ON TUESDAY. AFTER LOOKING OVER ALL THE AVAILABLE DATA...DECIDED TO GO WITH STRONG GALES ON ALL WATERS INSTEAD OF STORMS. HAVE ALLOWED GUST NR 50 KTS MERR RVR TO NEAR BOSTON HARBOR WATERS TUE AFTN. LOW LEVEL INVERSION CAN INHIBIT BUT PRES GRAD AND TURB MXG MAY ALLOW FOR GST 50KTS....ESP MERR RIVER REGION. HOWEVER...IT/S POSSIBLE THAT WINDS COULD BE SLIGHTLY STRONGER LATER TUESDAY...RESULTING IN A BRIEF PERIOD OF MARGINAL STORM FORCE WINDS. SEAS ON THE OUTER WATERS BUILD UP TO 15 FEET...WOULDN/T BE SURPRISED TO SEE 44008 AND 44018 TOP OUT BETWEEN 15 AND 20 FEET. STRONGEST WINDS BY TUE EVENING WILL BE ACROSS EASTERN WATERS EAST OF CAPE ANN TO CAPE COD WHERE STRONG SE GALES LIKELY INVOF LLJ. GUSTS TO 45 KT POSSIBLE. WINDS WILL SHIFT TO SW AND DECREASE AS OCCLUSION MOVES THROUGH. THIS WILL HAPPEN BY TUE EVENING OVER THE WESTERN WATERS AND AROUND MIDNIGHT EASTERN WATERS. SEAS UP TO 15 FEET OUTER EASTERN WATERS TUE NIGHT. OUTLOOK...WEDNESDAY THROUGH SATURDAY... WEDNESDAY THROUGH FRIDAY...WINDS WILL GENERALLY REMAIN BELOW SCA THRESHOLDS OVER THIS TIME. HOWEVER...ROUGH SEAS OVER THE OUTER-WATERS WILL CONTINUE REQUIRING SCA FOR MUCH IF NOT THE ENTIRE PERIOD. FRIDAY NIGHT AND SATURDAY...WE MAY SEE A BRIEF PERIOD OF SCA WIND GUSTS IN ASSOCIATION WITH OUR NEXT SYSTEM. OTHERWISE...HEADLINES WILL LIKELY NEED TO REMAIN UP FOR THE OUTER-WATERS MOST OF THE TIME. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...WIND ADVISORY FROM 7 AM TO 6 PM EST TUESDAY FOR MAZ013-017>024. HIGH WIND WATCH FROM TUESDAY MORNING THROUGH TUESDAY AFTERNOON FOR MAZ005>007-014>016. NH...HIGH WIND WATCH FROM TUESDAY MORNING THROUGH TUESDAY AFTERNOON FOR NHZ012. RI...WIND ADVISORY FROM 7 AM TO 6 PM EST TUESDAY FOR RIZ002-004>008. MARINE...GALE WARNING FROM 4 AM TO 7 PM EST TUESDAY FOR ANZ230>237-254- 255. STORM WARNING FROM 11 AM TO 7 PM EST TUESDAY FOR ANZ250. && $$ SYNOPSIS...DRAG/FRANK NEAR TERM...DRAG/EKSTER SHORT TERM...DRAG/EKSTER LONG TERM...FRANK AVIATION...NMB/FRANK MARINE...DRAG/FRANK ct AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TALLAHASSEE FL 300 PM EST MON NOV 24 2008 .SYNOPSIS... 19Z WATER VAPOR AND H4 RUC ANALYSIS SHOWING A NOW HIGHLY AMPLIFIED UPPER LEVEL PATTERN ACROSS NORTH AMERICA. MAIN FEATURE OF NOTE IS A SHARP MID/UPPER LEVEL TROUGH NOW PUSHING EAST OF THE MS VALLEY. INITIAL SHORTWAVE ENERGY IS DROPPING INTO THE SOUTHERN MS VALLEY AND REMAINS WELL DEFINED ON WV IMAGERY WITH MARKED DRYING IN ITS WAKE EXPANDING ACROSS THE ARKLATEX REGION. ANOTHER STRONG PIECE OF UPPER LEVEL ENERGY IS DIVING SOUTH OUT OF WESTERN ONTARIO INTO THE GREAT LAKES. THESE TWO FEATURES WILL CONSOLIDATE OVER THE NEXT 12-18 HOURS INTO AN ENERGETIC UPPER LEVEL DISTURBANCE OVER THE GREAT LAKES AND SOUTHWARD TO THE TENNESSEE VALLEY. ON EITHER SIDE OF THIS TROUGH WE FIND LONGWAVE RIDGING OVER THE INTER-MOUNTAIN WEST AND ALONG THE EAST COAST. SOUTHERN STREAM MOISTURE FEED IS ALSO SEEN MOVING NORTHEAST ACROSS MEXICO AND TOWARD THE NORTHERN GULF COAST. LARGE SCALE LIFT ASSOCIATED WITH MID-LEVEL HEIGHT FALLS IS COMBINING WITH THIS UPPER LEVEL MOISTURE AND VIGOROUS WWA IN THE LOWER LEVELS TO PRODUCE NUMEROUS SHOWERS AND THUNDERSTORMS FROM LA TO THE TN AND OHIO VALLEYS. THIS MAIN AREA OF SHOWERS AND STORM WILL BE APPROACHING OUR WESTERN ZONES OF SOUTHEAST AL AND THE FLORIDA PANHANDLE DURING THE EARLY AND MIDDLE EVENING HOURS. IN THE LOWER LEVELS...SURFACE RIDGING THAT HAS BEEN IN CONTROL OF THE REGION IS WEAKENING AND RAPIDLY MOVING SOUTH AND EAST LATE THIS AFTERNOON IN RESPONSE TO THE DEVELOPING SYSTEM TO OUR NORTHWEST AND ASSOCIATED APPROACH OF A COLD FRONT. THIS FRONT IS CURRENTLY LOCATED FROM THE OHIO VALLEY SOUTHWARD INTO THE CENTRAL TENNESSEE VALLEY AND THEN SOUTHWEST TO LA. A MIX OF SUN AND CLOUDS ACROSS THE AREA INTO THE EARLY EVENING BEFORE THE MAIN BAND OF CLOUDS AND SHOWERS OVERSPREADS FROM THE WEST. .SHORT TERM (TONIGHT THROUGH WEDNESDAY NIGHT)... THERE REMAINS VERY GOOD AGREEMENT AMONG THE MODEL SUITES AS TO THE EVOLUTION OF THE APPROACHING FRONT AND THE UPPER LEVEL DYNAMICS FROM THIS EVENING INTO TUESDAY MORNING. 850MB THETA-E RIDGE AND ASSOCIATED FORCED ASCENT WILL BE ARRIVING ACROSS THE FLORIDA PANHANDLE AND SOUTHEAST ALABAMA EARLY THIS EVENING. ALTHOUGH A STRAY SHOWER OR SPRINKLE IS CERTAINLY POSSIBLE OVER THIS AREA DURING THE REMAINING AFTERNOON HOURS...THE BULK OF THE PRECIP WILL HOLD OFF UNTIL AROUND SUNSET AND THROUGH THE EVENING HOURS. SURFACE INSTABILITY IS EXTREMELY LIMITED WITH SREF PROBS OF EVEN 500 J/KG HOLDING BELOW 5% OVER LAND. HOWEVER...MODELS CONTINUE TO INDICATE THAT WE WILL INITIALLY SEE SOME MARGINAL INSTABILITY ALOFT OVER THE WESTERN ZONES AS SHOWALTER INDICES APPROACH ZERO. WITH THIS IN MIND WOULD NOT BE SURPRISED TO GET A FEW RUMBLES OF THUNDER WITH THE BAND OF SHOWERS. COLD FRONT IS THEN EXPECTED TO STEADILY PUSH SOUTHEAST ACROSS THE AREA THROUGH THE NIGHT AND EXIT THE SOUTHEAST BIG BEND NEAR OR SHORTLY AFTER SUNRISE. INITIAL SHORTWAVE ENERGY IS PROGGED TO SHEAR OUT RAPIDLY TO THE NORTHEAST AS THE MAIN UPPER LOW ORGANIZES WELL TO THE NORTH. AS THIS OCCURS THE LARGE SCALE LIFT OVERHEAD ALL BUT COLLAPSES. MOISTURE AXIS BECOMES RATHER STRUNG OUT INTO THE EASTERN HALF OF THE FORECAST AREA AS WELL. WITH ALL THIS IN MIND SHOULD EXPECT A RATHER SOLID LINE OF RAIN/EMBEDDED STORMS OVER THE WEST THIS EVENING TO WEAKEN AND THIN OUT AS IT MOVES EAST AFTER MIDNIGHT. CURRENT FORECAST POPS SHOWING LIKELY TO CATEGORICAL VALUES OVER THE EASTERN FL PANHANDLE/SOUTHEAST ALABAMA AND PORTIONS OF SOUTHWEST GEORGIA THIS EVENING. THESE POPS TAPER TO ONLY LOW END CHANCE VALUES AFTER MIDNIGHT ACROSS THE FAR EASTERN ZONES APPROACHING THE SUWANNEE RIVER VALLEY. SHOWALTER INDICES SHOW A LESSENING OF THE ELEVATED INSTABILITY INTO OUR EASTERN ZONES AND WILL NOT BRING THUNDER MENTION EAST OF THE APALACHICOLA RIVER. THIS IS SHAPING UP TO BE A HIGH POP/LOW IMPACT EVENT...MEANING THAT ALTHOUGH MANY LOCATIONS WILL SEE A BRIEF PERIOD OF RAINFALL TONIGHT...THE DURATION IS LIKELY TO BE SHORT AND RAINFALL ACCUMULATIONS GENERALLY ON THE LIGHT SIDE. IN FACT...AS THE OVERALL DYNAMICS CONTINUE TO COLLAPSE DURING THE LATE NIGHT HOURS...FAR EASTERN AREA FROM VALDOSTA INTO THE EASTERN FLORIDA BIG BEND MAY ONLY SEE A QUICK LINE OF BROKEN SHOWERS PASS THROUGH WITH VERY LITTLE IN THE WAY OF ACCUMULATION. ANY LINGERING SHOWERS SHOULD EXIT THE SOUTHEAST FLORIDA BIG BEND AROUND SUNRISE TOMORROW WITH CLOUDS RAPIDLY DECREASING THROUGH THE MORNING. EXPECTING A PARTLY TO MOSTLY SUNNY AFTERNOON ALMOST REGION-WIDE WITH A GUSTY NORTH TO NORTHWEST WIND AND HIGH TEMPS WARMING FROM EARLY MORNING LOWS IN THE 40S UP INTO THE 60S. HIGH PRESSURE BUILDS OVERHEAD TUESDAY NIGHT AND REMAINS IN THE VICINITY THROUGH WEDNESDAY NIGHT. WITH THE HIGH SETTLING OVERHEAD AND WITH VERY DRY LOW LEVEL AIR IN PLACE...EXPECTING A GOOD RADIATIONAL COOLING EVENT RESULTING IN YET ANOTHER COLD MORNING. ASSUMING SURFACE WINDS CAN DROP TO CALM (WHICH APPEARS QUITE LIKELY WITH THE FORECAST HIGH POSITION) MANY NORMALLY COLDER LOCATIONS UNDER RADIATIONAL COOLING LOOK TO BOTTOM OUT WITHIN A FEW DEGREES EITHER SIDE OF FREEZING EARLY WEDNESDAY MORNING. HAVE ADDED PATCHY FROST TO ALL AREAS AWAY FROM THE IMMEDIATE COAST DURING THIS TIME AS FROST CAN TAKE HOLD AT GROUND LEVEL EVEN WITH 2 METER TEMPS HOLDING IN THE MIDDLE 30S. A PLEASANT FALL DAY EXPECTED FOR WEDNESDAY WITH PLENTY OF SUNSHINE. MAY SEE SOME INCREASE IN HIGH LEVEL CIRRUS...ESPECIALLY LATE...TO FILTER THE SUN AS GFS/ECMWF SHOWING A WEAK DISTURBANCE APPROACHING IN THE FAST UPPER LEVEL FLOW. HIGHS GENERALLY IN THE MIDDLE 60S. WITH THE SURFACE RIDGE STILL IN PROXIMITY WEDNESDAY NIGHT MAY ONCE AGAIN SEE A FEW AREAS APPROACH FREEZING LATE. BEST CHANCES WEDNESDAY NIGHT TO SEE FROST WILL BE ACROSS THE EASTERN FORECAST AREA...AND ESPECIALLY ACROSS THE SANDIER SOILS OF THE BIG BEND. THIS IS A LOWER CONFIDENCE FORECAST THAN ON TUESDAY NIGHT AS ANY CIRRUS POSSIBLY STILL OVERHEAD WOULD BE ENOUGH TO DISRUPT THE RADIATIONAL COOLING PROCESS AND KEEP TEMPS UP A FEW EXTRA DEGREES. .LONG TERM...(THURSDAY THROUGH MONDAY). CONTINUED AMPLIFIED AND FAST MOVING PATTERN ACROSS THE EASTERN CONUS IS STILL INDICATED THROUGHOUT THE LONG TERM PERIOD. SURFACE HIGH PRESSURE AND FLAT FLOW ALOFT WILL CREATE A PLEASANT THANKSGIVING ACROSS THE SOUTHEAST BEFORE AN APPROACHING WAVE OF LOW PRESSURE ACROSS THE WESTERN GULF COAST STATES BEGINS TO SPREAD EASTWARD FRIDAY AFTERNOON. THIS SOLUTION HAS BEEN GAINING SUPPORT BETWEEN THE GFS AND EURO...AND THE LATEST RUNS OF THESE MODELS CONTINUE TO SUPPORT THIS DEVELOPING STORM SYSTEM. IT APPEARS THAT A DEEPENING SHORT WAVE (ANOTHER IN A SERIES OF MANY) DROPPING OUT OF THE GREAT LAKES STATES ON FRIDAY NIGHT/SATURDAY MORNING WILL HELP PULL THE SURFACE WAVE NORTHEASTWARD OVER THE APPALACHIAN FOOTHILLS AND UP THE EAST COAST THROUGH SATURDAY AFTERNOON. THIS WILL RESULT IN A COLD FRONT PUSHING INTO OUR REGION SATURDAY AFTERNOON WITH GOOD CHANCES OF RAIN EXPECTED. THE TIMING OF THIS SYSTEM HAS DECENT CONSISTENCY BETWEEN THE OPERATIONAL GFS AND EURO...AS WELL AS MANY OF THE GFS ENSEMBLE MEMBERS. THERE ARE SOME DIFFERENCES BETWEEN HOW QUICKLY THIS SYSTEM WILL GET THROUGH THE REGION. HOWEVER...IF THE FRONTAL SYSTEM HOLDS UP OVER OR JUST SOUTH OF OUR FORECAST AREA...IT WON`T REMAIN THERE FOR LONG AS THE OVERALL EAST COAST TROF DEEPENS MORE AND ANOTHER PIECE OF ENERGY SHOULD CLEAR OUR REGION OUT BY THE FIRST OF THE WEEK. MAX TEMPERATURES THROUGHOUT THE FIRST PART OF THE LONG TERM PERIOD SHOULD GENERALLY BE AT OR JUST ABOVE CLIMO. A COOL DOWN BEHIND THE FRONTAL SYSTEM THAT PASSES EARLY SUNDAY MORNING WILL DROP MAX TEMPS BACK INTO THE LOWER 60S BY MONDAY. MIN TEMPS...ASIDE FROM A LIGHT FREEZE ON THURSDAY MORNING WILL WARM EACH DAY THROUGH SUNDAY...AND BE ABOVE NORMAL THESE LAST TWO DAYS. COOLER MINS RETURN BEHIND THE FRONT BY MONDAY MORNING. && .MARINE... HIGH PRESSURE WEAKENS AND SLIDES SOUTHEAST THIS EVENING ALLOWING WINDS TO COME AROUND TO SOUTH AND SOUTHWEST. COLD FRONT WILL CROSS THE WATERS FROM WEST TO EAST LATE THIS EVENING INTO THE EARLY MORNING HOURS WITH A SHARP WINDS SHIFT TO THE NORTHWEST AND NORTH. WINDS WILL INCREASE IN THE WAKE OF THE FRONT TO CAUTIONARY LEVELS. A BRIEF PERIOD OF ADVISORY LEVEL WINDS IS POSSIBLE INTO TUESDAY MORNING...ESPECIALLY OVER THE WESTERN LEGS AND THIS POTENTIAL WILL NEED TO BE MONITORED THIS EVENING. NORTHERLY FLOW WILL REMAIN ELEVATED NEAR CAUTIONARY LEVELS INTO TUESDAY EVENING. WINDS WILL THEN RAPIDLY DIMINISH INTO THE DAYLIGHT HOURS OF WEDNESDAY AS SURFACE HIGH PRESSURE BUILDS OVER THE NORTHEAST GULF OF MEXICO. THIS HIGH WILL REMAIN IN CONTROL OF THE FORECAST WATERS PROVIDING LIGHT WINDS AND SEAS THROUGH THURSDAY BEFORE THE NEXT SYSTEM BEGINS TO APPROACH FROM THE WEST FOR THE EARLY PART OF THE UPCOMING WEEKEND. && .AVIATION... VFR CIGS (AROUND 9K FT) WILL DEVELOP THIS AFTERNOON AHEAD OF AN APPROACHING COLD FRONT. SHRA WILL AFFECT KDHN BY THIS EVENING...THEN THE REST OF THE TERMINALS TONIGHT. MOST OF THE RAIN WILL NOT IMPACT CIGS OR VIS...BUT BRIEF PERIODS OF MVFR CONDITIONS WILL BE POSSIBLE IN ISOLATED +SHRA. WINDS WILL SHIFT TO NORTHWEST BEHIND THE COLD FRONT DURING THE EARLY MORNING HOURS...FOLLOWED BY DECREASING CLOUDS. NORTHWEST WINDS OF 10 KT (GUSTS TO 20 KT) ARE EXPECTED BY MID TO LATE TUESDAY MORNING...ALONG WITH UNLIMITED CIGS AND VIS. KTLH RADAR IMAGERY INDICATED A FIRE (AND SMOKE PLUME) 16 NM SOUTHWEST OF KTLH. SO FAR THE BOUNDARY LAYER WINDS HAVE NOT BEEN ADVECTING THE SMOKE OVER THE TERMINAL...BUT WE WILL WATCH THIS CLOSELY FOR VIS IMPACTS. && .FIRE WEATHER... A COLD FRONT WILL USHER DRIER AIR INTO THE REGION TUESDAY. THE COMBINATION OF DAYTIME HEATING AND THE DRY AIRMASS WILL DRIVE RELATIVE HUMIDITY LEVELS BELOW CRITICAL LEVELS TUESDAY AFTERNOON ACROSS OUR FL ZONES. HIGH DISPERSION VALUES ARE ALSO EXPECTED. THE HUMIDITY MAY BRIEFLY DROP BELOW 25 PERCENT IN OUR GA AND AL ZONES...BUT NOT LONG ENOUGH TO WARRANT A WARNING. RED FLAG CONDITIONS WILL BE POSSIBLE AGAIN WEDNESDAY AFTERNOON. && .PRELIMINARY POINT TEMPS/POPS... TALLAHASSEE 47 66 32 65 33 / 60 0 0 0 0 PANAMA CITY 49 66 39 66 45 / 70 0 0 0 0 DOTHAN 43 63 34 65 39 / 80 0 0 0 0 ALBANY 43 62 31 65 34 / 70 0 0 0 0 VALDOSTA 46 64 32 65 33 / 50 05 0 0 0 CROSS CITY 51 69 32 68 32 / 30 15 0 0 0 && .TAE WATCHES/WARNINGS/ADVISORIES... AL...NONE. GA...NONE. FL...RED FLAG WARNING FROM 12 PM EST /11 AM CST/ TO 6 PM EST /5 PM CST/ TUESDAY FOR THE FOLLOWING ZONES: BAY...CALHOUN... COASTAL WALTON...DIXIE...FRANKLIN...GADSDEN...GULF... HOLMES...INLAND WALTON...JACKSON...JEFFERSON...LAFAYETTE... LEON...LIBERTY...MADISON...TAYLOR...WAKULLA...WASHINGTON. GM...NONE. && $$ AVIATION/FIRE WEATHER...FOURNIER SYNOPSIS/SHORT TERM/MARINE...MROCZKA LONG TERM...GODSEY fl AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE MARQUETTE MI 120 PM EST MON NOV 24 2008 UPDATED FOR 18Z TAF ISSUANCE .UPDATE... UPPER LOW CONTINUES TO DROP SOUTHEASTWARD OUT OF WESTERN ONTARIO TOWARDS WESTERN LAKE SUPERIOR THIS MORNING. EVENTUALLY UPPER LOW WILL MERGE WITH S/WV OVER SOUTHERN LAKE MI FORMING BROADER UPPER LOW OVER SOUTHERN GREAT LAKES. WEAK SFC LOW CURRENTLY OVER SOUTHERN LOWER MI WILL MOVE SLOWLY EWD TO SOUTHERN LAKE HURON BY THE END OF THE DAY. BACK EDGE OF LIGHT SNOW FIELD ASSOCIATED WITH THESE FEATURES HAS MOVED INTO LAKE MI. BEST CHANCE FOR LIGHT SNOW THIS AFTERNOON WILL BE EAST OF A MANISTIQUE TO NEWBERRY LINE AND EVEN THERE AMOUNTS SHOULD BE LIGHT. AS MAIN UPPER LOW DROPS SOUTHEASTWARD ACROSS FAR WESTERN LAKE SUPERIOR EXPECT FLURRIES/-SHSN TO ACCOMPANY IT. WITH A SLIGHTLY WESTWARD UPPER LOW TRACK EXPECT BEST CHANCE OF THIS ACTIVITY ACROSS WESTERN UPPER MICHIGAN WITH CENTRAL AREAS REMAINING PRECIP FREE THROUGH MUCH OF THE DAY. 85H TEMPS WILL FALL INTO THE -8 TO -10 RANGE OVER WESTERN LAKE SUPERIOR AND AS WINDS BECOME MORE NORTHWESTERLY DO EXPECT SOME LAKE ENHANCEMENT TO OCCUR IN FAVORABLE UPSLOPE AREAS IN THE WEST. STILL NOT EXPECTING ANYTHING MORE THAN AN INCH OR AT MOST 2 OF ACCUMULATION DURING THE DAY TODAY. OVERALL TEMP FORECAST IS ON TRACK AND WILL NOT MAKE ANY ADJUSTMENTS TO IT. .SYNOPSIS... ISSUED AT 425 AM EST 08Z WATER VAPOR LOOP AND RUC 500MB HEIGHT ANALYSIS SHOWED RIDGING OVER THE WESTERN U.S. INTO SW CANADA...RIDGING IN THE OHIO VALLEY INTO THE EASTERN GREAT LAKES...AND A TROUGH FROM MANITOBA SOUTHWARD INTO THE CENTRAL PLAINS. WITHIN THE TROUGH...AN UPPER LOW IS LOCATED AT THE FAR NORTH END OF LAKE WINNIPEG. THE WARM CONVEYOR BELT AHEAD OF THE UPPER LOW EXTENDS FROM MO ACROSS UPPER MI AND INTO NE ONTARIO. SOME -SN IS FALLING OUT OF THE CONVEYOR BELT OVER THE CENTRAL PORTION OF THE CWA...ALSO IN THE SAME PLACE WHERE BETTER MOISTURE IS BASED ON 00Z RAOBS FROM MPX...COMPARED TO GRB AND APX WHICH REFLECT THE DRIER AIRMASS OVER EASTERN UPPER MI. A DRY SLOT IS EVIDENT ON 11-3.9 U IMAGERY OVER NE MN...BUT FARTHER NW OVER NW MN INTO MANITOBA IS THE COLD CONVEYOR BELT (CCB) CLOUDS ON THE BACK SIDE OF THE UPPER LOW. 850MB TEMPS UNDER THE CCB WERE AROUND -14C BASED ON THE 00Z SOUNDING FROM CYQD...QUITE A BIT COLDER THAN THE -1C AT MPX...-4C AT INL AND -6C AT CWPL. TO THE SW OF UPPER MI ON WATER VAPOR...A SHRTWV IS MOVING THROUGH SRN IA. ASSOCIATED WITH THE SHRTWV IS A 1015MB SFC LOW IN SE IA. A TROUGH EXTENDS NE FROM THE LOW ACROSS CENTRAL UPPER MI...THEN HEADS BACK TO THE NW AS A COLD FRONT WHERE IT CONNECTS UP TO A 1008MB LOW IN FAR NW ONTARIO. && .DISCUSSION... ISSUED AT 425 AM EST MAIN FORECAST CONCERNS ARE THE AMOUNT OF SNOW THE NEXT TWO DAYS... ALONG WITH POTENTIAL FOR FREEZING DRIZZLE. TODAY...UPPER LOW AT THE NORTH END OF LAKE WINNIPEG IS PROGGED TO SLIDE A LITTLE BIT FARTHER WEST COMPARED TO YESTERDAYS 00Z RUNS...MOVING INTO WRN WI AT 00Z TUE. THE BULK OF THE COLD AIR SEEN UPSTREAM AT CYQD WILL STAY UNDER OR TO THE WEST OF THE UPPER LOW. HOWEVER...SOME COOLING IS STILL EXPECTED TO COME INTO UPPER MICHIGAN WITH THE APPROACH OF THE UPPER LOW. NAM/GFS SHOW 850MB TEMPS FALLING TO -8 TO -10C OVER WRN LAKE SUPERIOR...WHICH WOULD BE GOOD ENOUGH FOR LAKE ENHANCED OR PERHAPS EVEN PURE LAKE EFFECT. WITH NW WINDS... IT WOULD SEEM LIKELY FOR SNOW IN WRN UPPER MI...ESPECIALLY IN UPSLOPE AREAS. HAVE RAISED POPS TO DEFINITE IN THE UPSLOPE AREA FROM IWD TO ROCKLAND. SOUNDINGS SUGGEST SNOW TO WATER RATIOS SOMEWHERE AROUND 10 TO 1...DUE TO MAJORITY OF VERTICAL MOTION BELOW THE DENDRITIC SNOW GROWTH ZONE...WHICH WITH A BLEND OF NAM/LOCAL WRF-ARW RUN/GFS FOR QPF RESULTS IN 1 TO 2 INCHES. THE AMOUNT OF COLD AIR CROSSING CENTRAL AND LAKE SUPERIOR IS A LITTLE MORE UNCERTAIN... WITH THE GFS SHOWING -8 TO PERHAPS -10C AT 00Z TUE...COMPARED TO THE NAM AND LOCAL WRF-ARW WHICH HAVE -4 TO -6C. EITHER SCENARIO SEEMS AT LEAST POSSIBLE FOR LAKE ENHANCED PCPN...ESPECIALLY GIVEN THAT THERE WILL BE PLENTY OF MOISTURE AROUND IN THE WARM CONVEYOR BELT AHEAD OF THE UPPER LOW. THE PROBLEM IS THAT THE WARMER SCENARIO WOULD RESULT IN POTENTIAL FOR RAIN TO MIX IN...PARTICULARLY OVER LAKE SUPERIOR AND OVER LAND NEAR THE SUPERIOR SHORELINE. GIVEN 00Z SOUNDING FROM CWPL UPSTREAM WAS -6C...WILL LEAN TOWARDS THE NAM/LOCAL WRF-ARW. THE WARMER SCENARIO ALSO MEANS THAT ANY SNOW THAT FALLS INLAND WILL ALSO BE WETTER WITH SNOW TO WATER RATIOS LESS THAN 10 TO 1. COULD BE AN INCH...PERHAPS TWO OF THIS WET SNOW IN THE EASTERN CWA. THE CENTRAL U.P. LOOKS TO BE MAINLY DRY TODAY...WITH SOME SUN AS THE DRY-SLOT WORKS IN. A FEW -SHSN COULD WORK IN OVER MQT COUNTY OFF OF WRN SUPERIOR IN THE AFTN...BUT THAT IS ABOUT IT FOR CENTRAL UPPER MI. ALTHOUGH COLD AIR IS FLOWING IN...EXPECT HIGHS AGAIN TODAY IN THE 30S...WARMEST SOUTH CENTRAL WITH DOWNSLOPING NW WINDS AND NEAR LAKE SUPERIOR WITH HEAT FLUX OFF THE WARMER WATER. TONIGHT...UPPER LOW MOVES SE INTO OHIO BY 12Z TUE...COMING CLOSE TO PHASING WITH THE SHRTWV CURRENTLY HEADING EAST OUT OF SRN IA. AS A RESULT...THE SFC LOWS THAT ARE CURRENTLY IN NW ONTARIO AND SE IA END UP MERGING TOGETHER INTO A DEEPER 1003 MB LOW NEAR LONDON ONTARIO AT 12Z TUE. THE DEEPENING LOW HELPS TO STRENGTHEN NORTH TO NE WINDS OVER EASTERN LAKE SUPERIOR. NORMALLY THIS WOULD SPELL COLDER AIR MOVING IN. HOWEVER...THE AIR COMING IN IS EITHER JUST AS COOL OR PERHAPS EVEN SLIGHTLY WARMER THAN THE AIR THAT IS IN OVER THE CWA AT 00Z PER 850MB TEMP PROGS. THE REASON IS THAT THE DEEPENING LOW HELPS TO PULL WARMER AIR IN OFF THE ATLANTIC INTO ITS CIRCULATION. SO WITH LITTLE TO NO CHANGE IN 850MB TEMPS...LAKE ENHANCEMENT SHOULD BE THE RULE...POSSIBLY PURE LAKE EFFECT IN THE WRN U.P.. PROBLEM IN THE WRN U.P. COMPARED TO TODAY IS THAT WITH THE DEPARTURE OF THE UPPER LOW...INVERSIONS FALL WITH THE MID-LEVEL HEIGHT RISES. THE QUESTION IS IF THE -10C ISOTHERM DRIES OUT...WHICH WOULD CHANGE THE PCPN FROM SNOW TO FZDZ GIVEN THAT AN UPSLOPING WIND CONTINUES. RIGHT NOW ONLY OUR LOCAL WRF-ARW RUN SHOWS THIS OCCURRING...WHILE THE NAM/GFS SHOW THE -10C ISOTHERM REMAINING MOIST. THEREFORE HAVE DECIDED TO KEEP THE P-TYPE AS SNOW. IN THE CENTRAL AND EAST...INVERSIONS WILL GRADUALLY LOWER AS WELL...BUT NOT AS QUICK. SO CONFIDENCE IS HIGHER THAT THE P-TYPE WILL STAY AS SNOW INLAND FROM LAKE SUPERIOR. AMOUNTS OF SNOW SHOULD NOT BE THAT IMPRESSIVE...MAYBE AN INCH OR TWO GIVEN LOW SNOW TO WATER RATIOS. REGARDING AREAS NEAR THE LAKE...THE WARMER NAM/LOCAL WRF-ARW RUNS SUGGEST HOLDING ON TO A RAIN/SNOW MIX THROUGH AT LEAST 09Z. IF THE PCPN IS GENERALLY LIGHT...THEN MORE OF THE PCPN SHOULD FALL AS RAIN. GIVEN THE WARMER 850MB TEMPS AND PLENTY OF CLOUDS...ALONG WITH A FLOW OF AIR OFF THE WARM LAKE SUPERIOR WATER...TEMPS SHOULD NOT DROP TOO MUCH. COLDEST READINGS EXPECTED IN THE INTERIOR WEST...CLOSEST TO THE COLDEST 850MB AIR...BUT EVEN THESE SHOULD ONLY BE IN THE MID 20S. TUESDAY...UPPER LOW IS PROGGED TO SHIFT INTO NORTH CENTRAL PA BY 00Z WED...WITH THE SFC LOW MOVING TO THE LAKE ONTARIO AREA. THIS ALLOWS A HIGH PRESSURE RIDGE TO BUILD INTO WESTERN UPPER MI BY 00Z...IN ADDITION TO CONTINUED MID-LEVEL HEIGHT RISES THROUGH THE DAY. THE RIDGE SHOULD BRING DRIER AIR IN...LIKELY TO THE WESTERN CWA...ENOUGH TO END PCPN BY EARLY AFTN. HOWEVER...THE CENTRAL AND EASTERN CWA WILL STAY IN LOW CLOUDS TRAPPED UNDER THE LOWERING INVERSION... ENHANCED BY LAKE SUPERIOR GIVEN COOL AIR BELOW THE INVERSION. PCPN TYPE IS VERY TRICKY...AS ALL MODELS SHOW THE -10C LAYER DRYING OUT THROUGH THE DAY. GIVEN A NORTH WIND OVER EASTERN LAKE SUPERIOR...SET UP IS FAVORABLE FOR UPSLOPE. SO WITH LAKE ENHANCEMENT OFF LAKE SUPERIOR AND UPSLOPE FLOW PRODUCING VERTICAL MOTION...SOME PCPN SHOULD OCCUR OUT OF THE CLOUDS. RIGHT NOW HAVE GONE WITH EITHER SNOW SHOWERS OR DZ/FZDZ (FZDZ OVER INLAND AREAS THROUGH THE EARLY AFTN). POPS ARE HIGHEST IN THE UPSLOPE AREAS OF THE NORTH CENTRAL IN THE MORNING...THEN DECREASE IN THE AFTN AS THE DRIER AIR TRIES TO WORK IN. GIVEN CLOUD COVER AND 850MB TEMPS THAT ARE SLIGHTLY COOLER THAN TODAY...HIGHS WILL ALSO END UP SLIGHTLY COOLER. STILL...MOST LOCATIONS SHOULD BE IN THE 30S...WARMEST IN THE DOWNSLOPE AREAS OF THE SOUTH CENTRAL. TUE NIGHT THROUGH THU...PER THE UKMET/NAM/GFS/ECMWF...UPPER MI LOOKS TO BE CAUGHT IN SQUEEZE-PLAY AS THE UPPER LEVEL PATTERN OVER CANADA AND THE NORTHERN U.S. BECOMES BLOCKED. THIS BLOCKING LOOKS TO BE A RESULT OF STRONG RIDGING BUILT UP AHEAD OF THE UPPER LOW TO OUR EAST. IN FACT...MODELS ARE IN GOOD AGREEMENT TAKING THE UPPER LOW BACK TO THE NW DURING THIS PERIOD...BASICALLY PULLED BY THE CURRENT SHRTWV CROSSING SRN IA. WHAT THIS MEANS FOR UPPER MI IS A PERSISTENT CHANCE FOR -SN ACROSS THE EAST HALF OF UPPER MI CLOSER TO THE DEEPER MOISTURE AROUND THE UPPER LOW...WHILE THE WEST HALF OF UPPER MI IS DRY WITH PARTLY CLOUDY SKIES UNDER THE INFLUENCE OF LOW INVERSIONS AND THE SURFACE RIDGE. STILL MAINTAINED THE POSSIBILITY OF SOME DZ/FZDZ OVER THE EASTERN CWA TUE NIGHT SINCE IT DOES NOT APPEAR THAT THE DEEPER MOISTURE WILL MOVE IN UNTIL WED. ANY PCPN LOOKS TO BE LIGHT AT THE CURRENT TIME DUE TO LACK OF SIGNIFICANT MOISTURE WITH THE UPPER LOW. GIVEN THE BLOCKED PATTERN...NO SIGNIFICANT COOLING OR WARMING IS PLANNED. THEREFORE... LOWS AND HIGHS ARE FORECAST TO BE ABOUT THE SAME THROUGH THE PERIOD...IN THE 20S AND 30S RESPECTIVELY. BEYOND THU...NO SIGNIFICANT CHANGES MADE. 00Z ECMWF/GFS/GFS ENSEMBLES ARE ALL IN VERY GOOD AGREEMENT SHOWING THE DEVELOPMENT OF A BROAD TROUGH ACROSS THE GREAT LAKES INTO THE OHIO VALLEY FOR FRI INTO THE WEEKEND. THIS TROUGH IS FORMED BY A COMBINATION OF THE UPPER LOW TO OUR EAST ON THU AND ANOTHER TROUGH DROPPING DOWN OUT OF CENTRAL CANADA. THIS MEANS THAT GRADUAL COOLING WILL OCCUR...COLD ENOUGH TO SET UP PURE LAKE EFFECT BY THE WEEKEND. && .AVIATION (FOR THE 18Z TAF ISSUANCE)... OVERALL...EXPECT MVFR CONDITIONS TO PREVAIL AT KCMX/KSAW THRU THIS FCST PERIOD. UPPER LOW DROPPING ACROSS WESTERN LAKE SUPERIOR WILL BRING SOME -SHSN TO KCMX THIS AFTN AND KSAW THIS EVENING. SOME LAKE ENHANCEMENT IS EXPECTED...ESPECIALLY AT KSAW AS CONVERGENT NRLY UPSLOPING FLOW DEVELOPS. MAY SEE IFR CONDITIONS FOR A TIME LATE EVENING INTO THE OVERNIGHT. LOW LEVEL MOISTURE TRAPPED UNDER INVERSION WILL KEEP MVFR CIGS AT BOTH KCMX AND KSAW THROUGH 18Z TUESDAY. && .MARINE (FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)... A LOW PRES TROF EXTENDING FROM NORTHERN ONTARIO ACROSS THE UPPER GREAT LAKES TO THE MID MISSISSIPPI RIVER VALLEY WILL CONSOLIDATE INTO A LOW PRES CENTER OVER SRN LAKE HURON THIS EVENING. AS THIS OCCURS...NRLY WINDS WILL BEGIN TO INCREASE ACROSS LAKE SUPERIOR THIS AFTN AND MORE SO THIS EVENING AND OVERNIGHT. EXPECT NRLY WINDS IN THE 20-30KT RANGE TONIGHT WITH THE STRONGEST WINDS OVER THE E HALF OF THE LAKE. IT`S NOT OUT OF THE QUESTION THAT SOME GALE FORCE GUSTS COULD OCCUR...BUT SINCE THERE IS A LACK OF COLD AIR ADVECTION TO INCREASE MIXING...WILL HOLD OFF ON ANY MENTION OF GALES. PROGRESSION OF THE MAIN WEATHER SYSTEMS WILL SLOW TO A CRAWL TUE THRU FRI. WITH LOW PRES TO THE E AND HIGH PRES TO THE W...N TO NW WINDS WILL BE THE RULE TUE THRU FRI WITH THE STRONGEST WINDS REMAINING OVER THE E HALF OF LAKE SUPERIOR. OVERALL...AFTER TUE...WINDS SHOULD GENERALLY BE IN THE 15-25KT RANGE OVER THE E AND 10-20KT OVER THE W. && .MQT WATCHES/WARNINGS/ADVISORIES... UPPER MICHIGAN...NONE. LAKE SUPERIOR...NONE. LAKE MICHIGAN...NONE. && $$ UPDATE...MZ SYNOPSIS/DISCUSSION...AJ AVIATION...MZ MARINE...ROLFSON mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 343 PM EST MON NOV 24 2008 .SYNOPSIS... A LOW PRESSURE SYSTEM OVER THE OHIO VALLEY WILL STRENGTHEN AS IT REACHES UPDATE NEW YORK ON TUESDAY...WHILE A SECONDARY LOW DEVELOPS AND MOVES OFF OF THE MID ATLANTIC COAST. MAINLY SNOW WILL FALL OVER NORTHERN SECTIONS WITH MOSTLY RAIN IN THE SOUTH THROUGH TONIGHT...WITH MIXED PRECIPITATION IN BETWEEN CHANGING BACK TO SNOW SHOWERS ON TUESDAY MORNING AS THE COLDER AIR WRAPS BACK AROUND TO THE SOUTH. AFTERWARDS...COLD...NORTHWESTERLY OVER-LAKE FLOW WILL KEEP SNOW SHOWERS IN THE FORECAST FOR MUCH OF THE REGION THIS WEEK WITH AREAS OF HEAVIER LAKE EFFECT AND OROGRAPHICALLY ENHANCED SNOWS POSSIBLE ACROSS THE WESTERN ALLEGHENIES. && .NEAR TERM /UNTIL 11 PM THIS EVENING/... PRECIP SHIELD HAS REACHED THE CENTRAL MOUNTAINS WITH LIGHT SNOW AND SOME SLEET FALLING HERE AT NWS CTP THIS HOUR. TRANSITION ZONE NOT FAR AWAY WITH MIXED PRECIP AT KFIG AND KDUJ...AND COLD RAIN AT KJST AND KAOO WITH 33F AIRTEMP AND 28F DEWPOINTS. CURRENT ADVISORIES SEEM WELL PLACED FOR THIS EVENING WITH LITTLE IN THE WAY OF CHANGES. 09Z SREF PTYPE PROBS CONT TO FAVOR SNOW MIXED WITH SLEET FROM CENTRAL MOUNTAINS NORTHWARD...WITH PRIMARILY SNOW FROM I80 NORTHWARD. SREF INDICATES CATEGORICAL PROBS OF .5" OR GREATER IN 12 HOURS FROM 18Z MON TO 06Z TUE. A FEW PLUMES SUGGEST THE POTENTIAL FOR MORE THAN 4 INCHES FROM WILLIAMSPORT NORTHWARD TONIGHT. MODEL FORECASTING SOUNDINGS ARE PREDOMINATELY "SNOW" SOUNDINGS AFTER PRECIP ARRIVES...WITH DYNAMIC COOLING TO THE WET BULB TEMPERATURES CREATING ISOTHERMAL SOUNDINGS BELOW FREEZING TO NEAR THE SURFACE FROM CENTRAL MOUNTAINS NORTHWARD. UNLIKE LAST YEAR WHICH WAS THE "WINTER OF THE WARM LAYER ALOFT" FOR MUCH OF CENTRAL PA... DIFFICULT TO FIND A WARM LAYER ALOFT WITH THIS SYSTEM. A MESSY EVENING COMMUTE IS AHEAD FOR MUCH OF CENTRAL AND ALL OF NORTHERN PA AS THE ONSET OF PRECIPITATION IS ILL-TIMED. FURTHER NORTH... PRIMARILY SNOW WILL CONTINUE WITH MANY AREAS LIKELY RECEIVING 3 OR 4 INCHES OF SNOW THROUGH LATE TONIGHT. TRANSITION BACK TO SNOW SHOWERS WILL OCCUR AFTER MIDNIGHT AS COLDER AIR WRAPS BACK AROUND INTO CENTRAL PA AS COASTAL LOW DEVELOPS. EXPECT WESTERN AND CENTRAL SECTIONS TO BE CHANGED OVER BEFORE 10Z WITH EASTERN SECTIONS LAGGING A BIT BEYOND THAT TIMEFRAME. && .SHORT TERM /11 PM THIS EVENING THROUGH 6 AM TUESDAY/... TRANSITION WILL CONTINUE ACROSS THE CENTRAL MOUNTAIN REGION TONIGHT...WITH I-80 FAIRLY CLOSE TO THE RAIN/SNOW LINE AS SUGGESTED BY LATEST GUIDANCE AND RUC13 FORECASTS OF WET BULB ZERO. THE LOWER SUSQ VALLEY SHOULD BE PRIMARILY RAIN. THE HIGHER ELEVS OF SULLIVAN/SCHUYLKILL CO POSE THE GREATEST FCST CHALLENGE FOR INTO TONIGHT...GIVEN THE ELEVATION PTYPE DEPENDENCE. HAVE HELD OFF AN ANY HEADLINES AT THIS POINT WITH ACCUMS OF 1-3 INCHES MENTIONED. WILL LET THE DAY SHIFT CONSULT THE LATEST GUID AND MAKE THE FINAL DECISION ON ANY FLAGS FOR TNT. THE CLD/OCCLD FNT WILL SWEEP ACROSS THE REGION LATE TONIGHT...ACCOMPANIED BY A GUSTY WIND SHIFT TO THE W/SW. THE HIGH RESOLUTION NAM/WRF DEPICTS A MORE ROBUST DRY SLOT IMMEDIATELY BEHIND THE FRONT...AND SOUNDINGS SHOW SOME DRYING ALOFT. THIS SHOULD RESULT IN MORE SHOWERY/LIGHTER PCPN AFT 06Z ESP ACROSS THE WEST. AS THE UPPER LVL TROF TRANSITIONS FROM A NEUTRAL TO A SLIGHTLY NEG TILT...ERN PA MAY PICK UP SOME ADDNL MOD TO HEAVY QPF AS MDLS HINT AT A SECONDARY WAVE DEVELOPING ALONG THE TRAILING CLD FNT. THIS IS OFTEN THE CASE AS THE AMPLIFIED NATURE OF THE LW TROF LEADS TO A SLOWER EWD FNTL PROGRESSION. THE ANOMALOUS H5 LOW IS FCST TO ESSENTIALLY MOVE OVERHEAD ON TUE...ACCOMPANIED BY VERY COLD TEMPS ALOFT AND STEEP MID LVL LAPSE RATES. THIS SHOULD RESULT IN NUMEROUS SNOW SHOWERS WITH LOCALLY HEAVY SQUALLS ACROSS MUCH OF THE AREA. THE ENTIRE STORM SYS BECOMES VERTICALLY STACKED AS IT RETROGRADES NWWD FROM THE LWR LAKES INTO SRN ONTARIO BY WED. THIS SET UP SHOULD FAVOR MORE LAKE EFFECT/ENHANCED AND OROGRAPHIC SNOWS ACROSS THE WESTERN ALLEGHENIES...WITH SEVERAL INCHES OF ACCUMULATION POSSIBLE BY WED NGT. && .LONG TERM /TUESDAY THROUGH MONDAY/... CHALLENGES WITH THE EXTENDED FORECAST RESIDE WITH LES SNOW MACHINE AND FAVORED ORAGRAPHIC LIFT SNOW REGIONS SEEING SNOW LATE TUE EVE THRU EARLY THUR. LCL WRF-ARW/NMM PAINT MID-LVL VORT ACROSS ALLEGHENIES TUE AFTN...LIFTING NORTHEAST TUE EVE. LCL MODELS SUGGEST AN AREA OF DEFORMATION SNOW MAY PERSIST ACROSS SUSQ-VALLEY TUE AFTN. ATTM THINKING ACCUMS SHUD REMAIN SUB-ADVISORY CRITERIA...HOWEVER THIS REMAINS A CONCERN. NEGATIVELY TILTED 500MB VORT...SENDS A WEAK VORT MAX ARND TROUGH AXIS TUE...ALLOWING COASTAL LOW TO DEV OFFSHORE OF LONG ISLAND/CAPE COD VICINITY. THIS SOLUTION WOULD FAVOR QUICKLY PULLING LLVL MOISTURE EAST OF THE SUSQ-VALLEY BY 21Z TUE. DRY WEDGE QUICKLY PUSHES INTO CENTRAL PA AFT 18Z AS FLOW SLOWLY BECOMES WESTERLY/NORTHWESTERLY. DENDRITIC GROWTH GRADUALLY LOWERS ACROSS ALLEGHENIES AS COLD AIR STEADILY POURS INTO THE WESTERN MOUNTAINS OF PA TUE EVE. 1000-850MB LAYERED RH SATURATES ARND 00Z WED...WITH A NARROW WEDGE OF OMEGA IN THE CROSS-HAIRS OF SEVERAL PROFILES. THIS SHUD KICK THE SNOW MACHINE INTO HIGH GEAR THRU EARLY THANKSGIVING DAY. MID-LVL VORT SLOWLY LIFTS NORTHEAST THUR INTO QUEBEC...ALLOWING FLOW TO BACK TO WESTERLY IN THE LLVL/S. THIS FEATURE WOULD PUSH ANY LINGERING LES NORTH OF PA INTO NEW YORK TOWARDS END OF THE WEEK. OPERATIONAL MODELS KEEP 850MB TEMPS WELL BELOW ZERO...COUPLED WITH A 534DM THICKNESS SUPPORT PRECIP AS SN. OPERATIONAL GFS PRODUCES A BROAD SFC RIDGE FOR THE MID-ATLANTIC FRI...HOWEVER FEEL IT WILL STRUGGLE TO MIX OUT LLVL MOISTURE. CLOUDS MAY LINGER THRU WEEKEND. ENSEMBLES SUGGEST A HIGH AMPLITUDE RIDGE BUILDING ACROSS THE WESTERN CONUS...FAVORING A PERSISTENT TROUGHING PATTERN FOR THE EASTERN US. SEVERAL MEMBERS TRY TO DEVELOP A VERY WEAK SOUTHERN STREAM SHORTWAVE SAT. THEN BRING IT NORTH ARND TROUGH AXIS FOR THE UPCOMING WEEKEND. TIMING AND PLACEMENT HAVE A LOW CONFIDENCE. && .AVIATION /21Z MONDAY THROUGH SATURDAY/... FLYING CONDITIONS CONTINUE TO DETERIORATE FROM WEST TO EAST THIS AFTERNOON WITH MVFR CIGS AND VSBYS IN S/R ACROSS THE SOUTHERN/WRN PA TAF SITES. MVFR WILL QUICKLY DROP TO IFR IN MIXED PRECIPITATION THROUGH EARLY EVENING...WITH SNOW ACROSS THE NORTH TONIGHT. MVFR TO IFR WILL PERSIST THROUGH LATE TONIGHT...WITH AREAS OF LIFR/VLIFR CIGS ACROSS THE MTNS OF WRN AND NRN PENN. PRECIP WILL BE LIGHTER AFTER 04Z TONIGHT...AND MAINLY IN THE FORM OF -DZ OR SNOW GRAINS AS THE TEMP IN THE CLOUD DECK WILL BE ABOUT -2C TO -6C AND TOO WARM FOR LARGER SNOWFLAKE FORMATION. A COLD FRONT WILL PUSH EAST ACROSS PA VERY EARLY TUESDAY. MVFR CIGS AND OCNL MVFR VSBYS IN SHSN WILL BE CONCENTRATED ACROSS THE HIGHER TERRAIN OF WRN AND NRN PENN (TAF SITES KJST AND KBFD). A SECONDARY COLD FRONT PUSHING ACROSS THE REGION TUESDAY NIGHT WILL USHER IN COLDER AIR...WITH MORE WIDESPREAD SNOW SHOWERS AND PERSISTENT MVFR TO IFR CIGS AND VSBYS ACROSS ALL OF CENTRAL AND NWRN PENN. AREAS OF LIFR/VLIFR CIGS/VSBYS WED AND WED NIGHT...WITH SOME IMPROVEMENT IN CONDITIONS SEEN FOR THANKSGIVING DAY AS THE FLOW BECOMES MORE WESTERLY. ANOTHER STORM WITH MIXED PRECIPITATION MAY AFFECT THE AREA FRIDAY INTO SATURDAY. && .CTP WATCHES/WARNINGS/ADVISORIES... WINTER WEATHER ADVISORY UNTIL 5 AM EST TUESDAY FOR PAZ004>006- 010>012-017>019-037-041-042-045-046. WINTER STORM WATCH FROM TUESDAY EVENING THROUGH LATE WEDNESDAY NIGHT FOR PAZ017-024-033. LAKE EFFECT SNOW WATCH FROM TUESDAY EVENING THROUGH LATE WEDNESDAY NIGHT FOR PAZ004-005-010. WINTER WEATHER ADVISORY UNTIL 7 PM EST THIS EVENING FOR PAZ024>028-049>053-056. && $$ SYNOPSIS...DEVOIR NEAR TERM...DEVOIR SHORT TERM...DEVOIR LONG TERM...BEACHLER AVIATION...DEVOIR/LAMBERT pa AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BROWNSVILLE TX 142 PM CST MON NOV 24 2008 .DISCUSSION...CURRENT 18Z VISIBLE SATELLITE IMAGERY AND RUC ANALYSIS SHOWS THE COLD FRONT OVER THE CORPUS CHRISTI CWA WITH 5 TO 10 KTS SURFACE WINDS AHEAD OF THE COLD FRONT. SCATTERED CUMULUS AND STRATOCUMULUS ARA MAINLY LOCATED OVER THE EASTERN HALF OF THE BRO CWA WITH MAINLY CLEAR TO PARTLY CLOUDY SKIES IN THE CENTRAL PORTIONS OF THE CWA. A DECK OF STRATOCUMULUS ENTERING THE WESTERN PORTIONS OF ZAPATA COUNTY. AS THE DAY PROGRESSES THE FRONT WILL APPROACH FROM THE NORTHWEST BRING A SLIGHT CHANCE OF SHOWERS THIS EVENING. A BLEND OF THE ECMWF AND GFS CONTINUES TO BE THE PREFERRED SOLUTION FOR THE GRIDS FOR TEMPERATURE AND PRECIPITATION FOR THE REMAINING OF THE WEEK. IN THE SHORT TERM AFTER THE PASSAGE OF THE FRONT AN UPPER LEVEL RIDGE WILL BUILD OVER NORTHERN MEXICO AHEAD OF A DEEPER TROF OF LOW PRESSURE THAT WILL ENTER THE SW US TOWARD THE LATTER PART OF THIS WEEK. UPPER LEVEL WINDS OVER DEEP SOUTH TEXAS WILL BE NORTHWESTERLY AND THEN WESTERLY AND SOUTHWESTERLY AS THE JET ON THE EASTERN SIDE OF THIS SYSTEM CONTINUES TO TRACK EAST TOWARD THE GULF OF MEXICO BY NEXT WEEKEND. BY WED 06Z SURFACE FLOW WILL BECOME SOUTHEASTERLY AND START INCREASING OUR TOTAL PRECIPITABLE WATER TO A MAX OF AROUND 1.60 BY THE END OF THE WEEK JUST PRIOR TO THE PASSAGE OF THE NEXT FRONT/TROF FROM THE SW US. THE SURFACE NE WINDS EXPECTED TO START SATURDAY MORNING COULD BRING OVERRUNNING PRECIPITATION TO DEEP SOUTH TEXAS WITH SOUTHWESTERLY FLOW ABOVE THE BOUNDARY LAYER. AS THE UNCERTAINTY DECREASES WITH THE AMPLITUDE AND TRACK OF THIS PACIFIC STORM THE GRIDS WILL BE CONTINUOUSLY UPDATED THROUGHOUT THE WEEK. THE 12Z ECMWF HAVE COME IN LINE MORE WITH THE 12Z GFS AND STILL SHOW THE ECMWF HAVING A MORE ABRUPT DROP IN THE DEWPOINTS FOR DEEP SOUTH TEXAS IN COMPARISON WITH THE GFS...HOWEVER...THE GFS DROPS TO LOWER DEWPOINTS THAN THE ECMWF BY MONDAY. BOTH THE NEW GFS AND ECMWF DEWPOINTS ARE HIGHER THAN FROM THE PREVIOUS RUNS. && .MARINE...THE 1 PM OBSERVATION FROM BUOY 42020 INDICATED WINDS WERE WEST SOUTHWEST AROUND 4 KTS AND SEAS WERE AROUND 4 FT WITH A PERIOD OF 8 SECONDS. MTRPIL REPORTED AN EAST NORTHEAST WIND AROUND 7 KTS. RELATIVELY QUIET MARINE CONDITIONS OBSERVED TODAY COMPARED THE LAST COUPLE DAYS. CHC FOR SCT SHRAS ARE POSSIBLE THE REST OF THE DAY AS A COLD FRONT CONTINUES TO APPROACH FROM THE NORTH. EXPECT WINDS TO REMAIN LIGHT TO MODERATE AND VARIABLE IN DIRECTION THRU THIS AFTN BEFORE BECOMING NORTHEAST BY THIS EVENING. WINDS SHOULD THEN INCREASE SOMETIME AFTER SUNSET TONIGHT IN THE WAKE OF THE FROPA. A MODERATE NORTHEAST WIND WILL REMAIN THRU THE DAYTIME HRS ON TUESDAY BUT BEGIN TO RELAX BY LATE IN THE DAY AS HIGH PRESSURE TAKES OVER. CONDITIONS LATE TONIGHT THRU TUESDAY COULD APPROACH SMALL CRAFT CONDITIONS...ESPECIALLY IN THE FAR OFFSHORE WATERS AT 20 TO 60 NAUTICAL MILES OFFSHORE. BASED ON LATEST OBS AND GUIDANCE...THINK CAUTION STATEMENT WILL SUFFICE FOR NOW...BUT LATER SHIFT COULD DECIDE IF STRONGER WORDING IS NEEDED. HIGH PRESSURE WILL SHIFT NORTHEAST INTO THE NORTHWEST AND NORTH CENTRAL GULF OF MEXICO ON WEDNESDAY WHICH WILL HELP TO ESTABLISH AN ONSHORE FLOW WITH MODERATE SOUTHEAST WINDS. THIS PATTERN WILL LIKELY THEN HOLD THROUGH THANKSGIVING INTO FRIDAY. CONDITIONS WITH THIS TYPE OF PATTERN MAY RESEMBLE THE SAME CONDITIONS THAT WERE EXPERIENCED THIS LAST WEEKEND WITH CLOUDY SKIES AND SCT SHRAS. ANOTHER POTENTIALLY STRONGER COLD FRONT IS ANTICIPATED TO PASS THROUGH THE LOWER TX COASTAL WATERS LATE FRIDAY OR EARLY SATURDAY. MARINE CONDITIONS IN THE WAKE OF THIS FRONT WILL HAVE THE POTENTIAL TO APPROACH OR EXCEED SMALL CRAFT ADVISORY CRITERIA. SEAS THE REST OF TODAY SHOULD REMAIN FAIRLY STEADY WITH AN INCREASE EXPECTED ONCE THE COLD FRONT PASSES. SEAS WILL REMAIN SLIGHTLY ELEVATED THROUGH TUESDAY BEFORE A SLIGHT DECREASE IS EXPECTED ON WEDNESDAY INTO THURSDAY. BUILDING SEAS ARE ANTICIPATED ONCE AGAIN TO TAKE PLACE POST FRONTAL LATE FRIDAY INTO SATURDAY. && .AVIATION...VSBL SATL IMAGERY SHOWS CU DEVELOPMENT ACROSS THE CWA THIS AFTN. CLD BANDS ASSOC A COLD FRONT APPROACHING FROM THE NORTH FROM AROUND CRP TO LRD. EXPECT CLDS TO HANG ON THROUGH TONIGHT. SOME SCT SHRAS COULD BE POSSIBLE WITH THE FROPA. A LIGHT AND VARIABLE WINDS IS EXPECTED THIS AFTN BEFORE BECOMING NORTHEAST BY THIS EVENING. LIGHT TO MODERATE NORTHEAST WINDS WILL CONTINUE THROUGH TUESDAY. EXPECTING VFR CONDITIONS TO PREVAIL THE NEXT 24 HRS. .PREV DISCUSSION... /ISSUED 940 AM CST MON NOV 24 2008/ DISCUSSION... THERE IS A CHANCE FOR SCT SHRAS LATER TODAY AS A COLD FRONT APPROACHES FROM THE NORTH. THE FRONT SHOULD CLEAR THE AREA BY EARLY TUESDAY MORNING. A LIGHT SOUTHERLY WIND TODAY WILL BACK NORTHEASTERLY ON TUESDAY AND REMAIN MODERATE THROUGH TUESDAY AFTN. ECMWF...NAM...AND GFS ARE IN GOOD AGREEMENT IN THE SHORT TERM DEPICTING WELL A WEAK FRONTAL PASSAGE FOR TONIGHT. IN THE EXTENDED RANGE THE ECMWF SHOWS A SHARP DECREASE IN DEWPOINTS AFTER FRIDAY AT 18Z DOWN TO 45F AT BROWNSVILLE...WHILE THE GFS SHOWS A GRADUAL DECREASE DOWN TO 55F BY MONDAY MORNING. UPDATED THE GRIDS TO KEEP A 50...50 BLEND OF THE GFS AND ECMWF POPS TO ACCOUNT FOR THIS MODEL UNCERTAINTY. NO TEMPERATURE CHANGES WERE DONE AT THIS TIME. && .PRELIMINARY POINT TEMPS/POPS... BAYVIEW/PORT ISABEL 64 72 63 79 / 20 10 20 10 BROWNSVILLE 61 73 59 81 / 20 10 10 10 HARLINGEN 59 72 57 82 / 10 10 10 10 MCALLEN 61 73 57 82 / 10 10 10 10 RIO GRANDE CITY 59 71 57 80 / 20 10 10 20 SOUTH PADRE ISLAND 64 73 63 78 / 30 10 10 20 && .BRO WATCHES/WARNINGS/ADVISORIES... TX...NONE. GM...NONE. && $$ THIS PRODUCT IS ALSO AVAILABLE ON THE WEB AT: HTTP://WWW.WEATHER.GOV/BROWNSVILLE 53/57 tx