AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TUCSON AZ 215 PM MST SAT SEP 15 2007 .SYNOPSIS....SOUTHERLY FLOW AHEAD OF A WEST COAST TROUGH WILL CONTINUE TO DRAW MONSOON MOISTURE INTO THE REGION AND LEAD TO AN INCREASING CHANCE OF SHOWERS AND THUNDERSTORMS. AS THE TROUGH MOVES INLAND MONDAY...ITS ASSOCIATED COLD FRONT WILL SWEEP ACROSS THE REGION AND LEAD TO MUCH DRIER CONDITIONS AND MORE SEASONABLE TEMPERATURES FOR THE MIDDLE PART OF THE WEEK. ANOTHER PACIFIC STORM SYSTEM MAY PULL MOISTURE BACK NORTH INTO THE REGION BY NEXT WEEKEND. && .DISCUSSION...THE ACTIVE 48-60HR PERIOD WE HAVE BEEN FORECASTING FOR A FEW DAYS NOW IS GETTING UNDERWAY. MESOSCALE CONVECTIVE VORTEX LIFTING N THROUGH SONORA...ALONG WITH THE DEEP S FLOW TAPPING INTO THE MONSOON MOISTURE TO OUR S...HAS HELPED TO SPARK MAINLY MOUNTAIN TSTMS EARLY THIS AFTERNOON. THOSE HAVE SINCE BEGUN TO PUSH OFF IN THE 10-15KTS OF SSE FLOW. WATER VAPOR CONTINUES TO SHOW THE INVERTED TROUGH MOVING SLOWLY N ACROSS SINALOA AND TOWARD SE AZ. MEANWHILE... THE SHORT WAVE LIFTING ACROSS NE NV IS INDUCING SOME DIVERGENCE OVER MUCH OF THE STATE...WITH STRONG TSTMS FIRING OVER THE W DESERTS AND EVEN OVER NE AZ. BOTH NAM AND GFS INDUCE SOME SORT OF A CONVECTIVE SYSTEM OVER PIMA/SANTA CRUZ COUNTIES TONIGHT...AND BASED ON HOW THINS HAVE BEEN EVOLVING...I AM BEGINNING TO BELIEVE IT. HAVE ALREADY RAISED POPS FOR THIS AFTERNOON AND TONIGHT IN AN EARLY AFTERNOON UPDATE...BUT WE MAY HAVE TO RAISE THEM EVEN MORE IN THE AFTERNOON PACKAGE...WHILE CARRYING LOW GRADE POPS ALL NIGHT. THE STRONGER STORMS WILL HAVE TO BE WATCHED FOR MICROBURST/DOWNBURST POTENTIAL WITH LATEST SPC RUC MESOANALYSIS SHOWING DCAPE AT 1200-1300 J/KG. HWO WAS ISSUED EARLIER TO MENTION THIS...MAINLY SOUTHWEST OF A WINKLEMAN-DOUGLAS LINE WHERE THE DEEPEST MOISTURE ARRIVES. FORTUNATELY...THE MODELS HAVE CONVERGED SOMEWHAT ON HOW THE NEXT 48HRS WILL EVOLVE. THERE ARE STILL SOME QUESTIONS ABOUT SEVERE POTENTIAL SUN AFTERNOON/NIGHT WITH SOLAR HEATING NOW IN DOUBT AND BEST 0-6KM SHEAR HOLDING OFF UNTIL THE DRY SLOT OVERRUNS US MON MORNING. WHAT IS NOW CLEAR...THOUGH...IS THAT MUCH OF THE CWA IS GOING TO RECEIVE SOME DECENT PRECIP AT SOME POINT BEFORE THE FRONT SWEEPS THROUGH THE CWA MON MORNING. BOTH NAM AND GFS NOW BRING IN ENOUGH COOLING ALOFT TO BRING THICKNESSES DOWN TO SATURATION OF THE 1.5 TO 1.7" PRECIP WATERS WE WILL HAVE IN PLACE SUN AFTERNOON/ EVENING. IF WE END UP WITH THE 1500+ J/KG OF CAPE THE LATEST SREF IS SUGGESTING...WE COULD HAVE A FLASH FLOOD THREAT ON TOP OF THE RISK FOR HAIL AND STRONG WINDS. HOWEVER...HEIGHT FALLS ACTING ON A TROPICAL MOISTURE PLUME LIKE THIS CAN JUST AS EASILY RESULT IN WIDESPREAD SHOWERS OR EVEN STRATIFORM RAIN WITH JUST EMBEDDED TSTMS. WE WILL NOT GO TOO HIGH WITH QPF YET...BUT IN CONCERT WITH OUR NEIGHBORS...WE WILL RAISE POPS ANOTHER 10 PCT SUN-SUN NIGHT AND RAISE OUR QPFS TO THE 0.25-0.5" RANGE. WE COULD STILL BE TOO LOW ON BOTH...BUT THIS IS A GOOD START. BASED ON WHERE THE JET CORE WILL TRAVERSE /N AZ/...IT STILL LOOKS LIKE THE DRY SLOT WILL RACE ACROSS ALL BUT FAR NE PORTIONS OF THE CWA MON AND CAP US OFF BEFORE THE FRONT ITSELF ARRIVES. SO WILL REFINE POP TIMING A BIT TO HIGHLIGHT THE IMPROVING CONDITIONS ALONG WITH SOME SW BREEZES BEHIND THE FRONT. AFTER MON...NOT ONLY WILL WE GET A BREAK FROM THE HEAT...THE HUMIDITY WILL FINALLY DROP AND ALLOW DIURNAL RANGES TO WIDEN TO SOMETHING MORE TYPICAL OF MID SEP. NIGHTTIME LOWS WILL BE PRETTY COMFORTABLE IN THE TUE-FRI PERIOD...WITH SOME SEASONABLY COOL 30S IN THE SOUTHERN WHITES EXPECTED. THE MEDIUM RANGE MODELS CONTINUE TO THROW US SLOW CURVES... KNUCKLEBALLS...AND OTHER VARIETIES OF JUNK PITCHES WITH OUR DAY 5-7 SYSTEM. THE 12Z ECMWF HAS REPEATED ITS 00Z TREND OF CLOSING A DEEP LOW OFF OVER S CA BY LATE NEXT FRI AND DRAWING THE MONSOON BACK NORTH. THAT WAS WHAT THE GFS HAD OVER THE PAST FEW DAYS. MEANWHILE...THE 12Z GFS CARRIES THE BOWLING BALL OFFSHORE TO 130W... WHICH WOULD MEAN RIDGING AND TEMPS ACTUALLY CLIMBING INSTEAD OF DROPPING. THE ENSEMBLES SHOW AN UNUSUALLY LARGE SPREAD...WHILE THE GFS ENSEMBLE HAS A 4-5 STANDARD DEVIATION NEGATIVE ANOMALY OVER THE CA BIGHT. SUCH ANOMALIES RARELY VERIFY...AND INSTEAD SUGGESTS THE MODEL SHOULD NOT BE TRUSTED...ESPECIALLY WITH MUCH WEAKER POSITIVE ANOMALIES ON EITHER SIDE OF THE LOW. WILL FOLLOW HPC/S ADVICE AND LEAN TOWARD THE ECMWF FOR NOW WITH GREAT CAUTION. THIS WILL SUPPORT A SLIGHT INCREASE IN COULD COVER AND HIGHER TERRAIN POPS. && .AVIATION...ISOLATED TSTMS HAVE DEVELOPED AND WILL THREAT ALL TAF SITES THIS EVENING...WITH THE GREATEST THREAT TO KTUS AND KOLS. ANY TSTMS THAT APPROACH AIRPORTS WILL BE CAPABLE OF PRODUCING WIND GUSTS OVER 40KTS...WITH AN OUTSIDE CHANCE OF BRIEF MVFR VISIBILITIES. THE RISK WILL DIMINISH AFTER ABOUT 03Z. AVIATION DISCUSSION NOT UPDATED FOR TAF AND TWEB AMENDMENTS. && .TWC WATCHES/WARNINGS/ADVISORIES...NONE. $$ PYTLAK WEATHER.GOV/TUCSON az AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PUEBLO CO 434 AM MDT FRI SEP 14 2007 .SHORT TERM... (TODAY AND TONIGHT) MAIN FCST CONCERNS WILL BE EXTENT AND PERSISTENCE OF STRATUS ACROSS THE SE PLAINS TODAY...THEN POTENTIAL FOR SHOWERS/TSTORMS THIS AFTERNOON/EVENING WITH INCOMING SHORTWAVE...FOLLOWED BY STRATUS REDEVELOPMENT OVERNIGHT ACROSS THE PLAINS. STRATUS HAS BEEN SLOWLY DEVELOPING ACROSS THE SE PLAINS...WITH VFR TO MVFR CIGS BEING REPORTED AT KPUB AND KLHX AND KAFF. FROM FOG IMAGERY PRODUCT APPEARS STRATUS SHOULD SPREAD QUICKLY INTO SRN EL PASO COUNTY...AIDED BY SE UPSLOPE WINDS. MOISTURE LAYER IN NAM SOUNDINGS IS VERY SHALLOW NEAR THE EASTERN MTS...AND NEITHER RUC NOR NAM12 ARE PRINTING OUT MUCH IN THE WAY OF QPF FOR THE I-25 CORRIDOR. THUS HAVE PARED OUT MORNING POPS FOR THIS REGION. FARTHER EAST...IS STILL DIFFICULT TO SAY. MOISTURE LAYER IS A LITTLE THICKER ACROSS THIS REGION...AND THERE COULD BE SOME SPOTTY DRIZZLE DEVELOP TOWARDS MORNING. IN ADDITION...A WEAK SHORTWAVE MOVING ACROSS CO IS SPREADING SOME MID/HIGH LVL MOISTURE ACROSS THE REGION...AND COULD SEE A FEW SPRINKLES DEVELOP WITH THIS WEAK FEATURE. ALL-IN-ALL AM NOT THAT IMPRESSED WITH PCPN POTENTIAL...BUT WILL MAINTAIN SOME LOW GRADE ISOLATED POPS NEAR THE EASTERN BORDER THROUGH THE MORNING. STRATUS SHOULD BEGIN TO BREAK BY AFTN. SRLY RETURN FLOW DEVELOPS IN THE LOW LVLS...SO STRATUS SHOULD BREAK MORE QUICKLY ALONG THE NRN EDGE OF THE RATON RIDGE...AND PERSIST THE LONGEST ALONG THE SRN EDGE OF THE PALMER WHERE SRLY COMPONENT WILL PROVIDE AN UPSLOPE COMPONENT. FAR EASTERN AREAS WHERE MOIST LAYER IS DEEPEST MAY ALSO SEE STRATUS PERSIST INTO THE EARLY AFTN. FOR WESTERN AREAS...AN EMBEDDED SHORTWAVE CURRENTLY BACK OVER UT WILL BE MOVING INTO WRN CO...BRINGING A FETCH OF SUBTROPICAL MOISTURE AND SOME WEAK FORCING. THIS SHOULD BE SUFFICIENT FOR ISOLATED SHOWERS AND THUNDERSTORMS TO DEVELOP OVER THE MTS BY AFTN. THIS ACTIVITY SPREADS EASTWARD ACROSS THE PLAINS DURING THE EVENING...AIDED BY LOW LVL JET WHICH MAY PROVIDE ENOUGH LIFT TO GENERATE SOME ELEVATED CONVECTION INTO THE OVERNIGHT HRS ACROSS FAR EASTERN CO/WRN KS. WHILE THE NAM IS LIKELY OVERDONE WITH THE AREAL COVERAGE AND AMOUNTS OF QPF ACROSS THE SE PLAINS TONIGHT...THINK IT WARRANTS SOME ISOLATED POPS WHICH BLENDS WELL WITH NEIGHBORS. INTERESTINGLY...SRLY RETURN FLOW TRIES TO ADVECT SOME LOWER 50 DEW POINTS INTO THE SRN I-25 CORRIDOR/NRN SLOPES OF THE RATON RIDGE BY AFTN. THIS MAY YIELD UP TO 1500 J/KG OF CAPE IN AN ENVIRONMENT WITH DEEP LAYER SHEARS OF 40-50 KTS WHERE EASTERLY LOW LVL FLOW RESIDES UNDER STRENGTHENING WESTERLIES ALOFT WITH INCOMING SHORTWAVE/UPPER JET. THUS ENVIRONMENT COULD SUPPORT A SUPERCELL THUNDERSTORM DOWN ALONG THE SRN I-25 CORRIDOR...THOUGH THIS WILL DEPEND ON HOW MUCH SFC HEATING CAN TAKE PLACE TO ERODE LOW LVL STABLE LAYER. WIND GUSTS UP TO NEAR 58 MPH AND HAIL TO NEAR 3/4 INCH IN DIAMETER WILL BE POSSIBLE IN THIS REGION. ELSEWHERE...THE MOUNTAINS AND HIGH VALLEYS COULD SEE SOME LOCALLY GUSTY WINDS UP TO 45 MPH...BRIEF RAINFALL AND LIGHTNING AS THE MAIN THUNDERSTORM THREATS. STRATUS MAKES A RETURN OVERNIGHT ESPECIALLY ACROSS EASTERN AREAS. AFTER 06Z LEE TROF DEVELOPS WHICH HELPS SPREAD SOME WESTERLIES INTO THE I-25 CORRIDOR WHICH SHOULD BEGIN TO ERODE WESTWARD EDGE OF STRATUS TOWARDS DAWN. -KT .LONG TERM... (SATURDAY THROUGH THURSDAY) .SATURDAY...THE SURFACE HIGH CONTINUES TO MOVE TO THE EAST. NAM SUGGESTS THAT SOME LOW CLOUDS AND FOG WILL LINGER ON THE PLAINS EARLY IN THE MORNING...AND MOSTLY CLOUDY REMAINS IN THE GRIDS. BY MIDDAY...WESTERLY FLOW WILL DEVELOP OVER MUCH OF THE PLAINS WITH TEMPERATURES WARMING TO ABOVE CLIMATOLOGY. THERE WILL BE THE POSSIBILITY OF THE LEE TROUGH LINGERING NEAR THE KANSAS BORDER DURING THE AFTERNOON. NAM SHOWS A NARROW AREA OF CAPES APPROACHING 2500 J/KG IN WESTERN KANSAS...EXTENDING INTO SOUTHEAST BACA COUNTY. WITH BULK SHEARS OF 40 KNOTS...THERE IS THE POTENTIAL FOR STORMS TO BECOME STRONG IF THERE IS ENOUGH INSTABILITY. IN THE GRIDS...SLIGHT CHANCE POPS WERE EXTENDED EASTWARD TO NEAR THE KANSAS BORDER. OTHERWISE...SOME MID LEVEL MOISTURE IN THE RIDGE MAY RESULT IN A FEW AFTERNOON AND EVENING STORMS OVER THE MOUNTAINS. .SUNDAY...FAIRLY STRONG TROUGH WILL MOVE INTO THE GREAT BASIN. GFS..NAM AND EC INDICATE SOUTHWEST FLOW AHEAD OF THE TROUGH WILL PULL SOME SUB TROPICAL MOISTURE NORTHWARD INTO THE STATE. POPS IN THE SOUTHWEST AND CENTRAL MOUNTAINS WERE INCREASED WITH SCATTERED POPS OVER THE WESTERN MOUNTAINS. POPS ARE LOWER OVER THE EASTERN MOUNTAINS...AND REMAIN NEAR ZERO ON THE PLAINS. WITH BROAD SOUTHWEST FLOW ALOFT...THERE WILL NOT BE MUCH LOWER LEVEL MOISTURE ON THE PLAINS TO DEVELOP ANY STORMS. MEX AND MAV HAVE TEMPERATURES IN THE UPPER 90S OVER PORTIONS OF THE PLAINS. THIS MAY BE A LITTLE BIT TO WARM WITH THE MID SEPTEMBER SUNSHINE...AND MAXIMUMS WERE KEPT IN THE UPPER 80S TO LOWER 90S ON THE PLAINS...WHICH IS STILL WELL ABOVE NORMAL. .MONDAY AND TUESDAY...ONE TROUGH WILL MOVE THROUGH THE REGION ON MONDAY WITH A SECOND TROUGH PASSING ON TUESDAY. BEST CHANCES FOR PRECIPITATION WILL BE MONDAY AFTERNOON OVER THE MOUNTAINS WITH THE SYNOPTIC FORCING...DAYTIME HEATING AND MID LEVEL MOISTURE. ON THE PLAINS...LOWER LEVELS WILL BE DRY...BUT WITH THE SYNOPTIC LIFT AND COOLING ALOFT...A FEW HIGH BASED THUNDERSTORMS WILL DEVELOP. ON TUESDAY...THE MODELS HAVE THE TROUGH PASSING DURING THE MORNING WITH VERY DRY AIR MOVING INTO THE REGION. THE ISOLATED POPS OVER THE REGION WERE KEPT FOR TUESDAY...GIVEN THE POTENTIAL FOR THE TROUGH TO BE SLOWER. .WEDNESDAY AND THURSDAY...EC ...GFS AND ENSEMBLES HAVE A STRONG TROUGH DIVING SOUTHWARD INTO THE GREAT BASIN. SOUTHERLY FLOW AHEAD OF THE TROUGH WILL TEND TO KEEP TEMPERATURES ABOVE AVERAGE. && .AVIATION...MVFR STRATUS SHOULD SPREAD ACROSS THE SE PLAINS BETWEEN 09Z AND 13Z. STRATUS WILL BE THICKER NEAR THE CO/KS BORDER WHERE SOME VERY LIGHT DRIZZLE OR SPRINKLES WILL BE POSSIBLE THIS MORNING. STRATUS WILL GRADUALLY ERODE DURING THE LATE MORNING/EARLY AFTERNOON HOURS WITH ISOLATED THUNDERSTORMS DEVELOPING OVER THE MOUNTAINS AFTER NOON. THESE THUNDERSTORMS MAY MOVE OFF INTO THE ADJACENT PLAINS DURING THE EVENING...THOUGH THE MAJORITY OF THESE SHOULD REMAIN FAIRLY WEAK...PRODUCING SOME BRIEF RAINFALL AS THEY GRADUALLY DISSIPATE AS THEY MOVE OVER COOLER MORE STABLE AIRMASS ACROSS THE PLAINS. THE EXCEPTION TO THIS WILL BE NEAR KTAD WHERE A STRONG STORM OR TWO WILL BE POSSIBLE. MVFR STRATUS IS EXPECTED TO REDEVELOP OVERNIGHT WITH SOME LIGHT SHOWERS AND THUNDERSTORMS POSSIBLE DURING THE OVERNIGHT HOURS AS LOW LVL JET SETS UP. THESE SHOULD END BY EARLY SAT MORNING. STRATUS WILL ERODE AWAY FROM THE EASTERN MTS AND THE KCOS/KPUB TAF SITES BY 12Z AS WESTERLY LOW LVL FLOW SPREADS INTO THE I-25 CORRIDOR. && .PUB WATCHES/WARNINGS/ADVISORIES... NONE. && $$ 31/06 co AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE UPTON NY 239 PM EDT SAT SEP 15 2007 .SYNOPSIS... A COLD FRONT WILL CONTINUE TO TRACK TO THE EAST...AND WILL BE FOLLOWED BY STRONG HIGH PRESSURE. THE COOLEST WEATHER OF THE SEASON SO FAR IS EXPECTED AS THIS HIGH BUILDS IN. THE HIGH WILL HANG AROUND FOR AWHILE...RESULTING IN A FAIR WEATHER WEEK AHEAD...WITH GRADUALLY MODERATING TEMPERATURES. && .NEAR TERM /THROUGH TONIGHT/... TYPICAL STRONG LATE SUMMER/EARLY FALL FRONT HAS PASSED. COOL SEASON SYNOPTIC FLOW IN FULL FORCE AS STRONG HIGH PRESSURE SLOWLY BUILDS TOWARD THE REGION TONIGHT. IN SPITE OF STRONG CAA...IT DOES LOOK LIKE ATMOSPHERE WILL REMAIN MIXED THROUGH THE OVERNIGHT HOURS. THIS EXPECTED NW FLOW TO PREVENT TEMPS FROM BOTTOMING OUT AS LOW AS THEY COULD HAVE IN IDEAL RADIATIONAL COOLING SITUATION. THIS WOULD LIMIT ANY FROST DEVELOPMENT...AND KEEP READINGS ON THE HIGHER SIDE OF MOS. OTHERWISE...CLEAR SKIES PREVAIL OVERNIGHT AS THIS DRY AIRMASS RUSHES IN. && .SHORT TERM /SUNDAY THROUGH TUESDAY/... FAST FLOW ALOFT...AND SURFACE HIGH WILL BUILD OVERHEAD...AND SLOWLY PUSH TO THE EAST OF THE REGION THROUGH TUESDAY AS HEIGHTS BUILD ALOFT. LITTLE CLOUD COVER TO SPEAK OF THROUGH THE PERIOD. AS FOR TEMPS...WITH H8 HPA TEMPS RUNNING AROUND 4 TO 5C...LOOKS LIKE MID TO UPPER 60S SHOULD SUFFICE FOR SUNDAY. GOOD RADIATIONAL COOLING CONDITIONS SUNDAY NIGHT AS HIGH PRESSURE BUILDS...WINDS LIGHTEN AND SKIES REMAIN CLEAR. THIS SHOULD BE THE COLDEST NIGHT...AND BETTER CHANCE FOR FROST DEVELOPMENT. TEMPS SHOULD DROP QUICKLY...LOWER 50S METRO...THE 40S SUBURBS WITH UPPER 30S INTERIOR/PINE BARRENS OF LI EXPECTED. AIRMASS MODIFIES MONDAY AND TUESDAY WITH TEMPS CLIMBING A COUPLE OF DEGREES EACH DAY. H8 TEMPS UP TO 6C MONDAY AND TUESDAY AS HIGH PRESSURE REMAINS JUST NORTHEAST. MARITIME FETCH FROM WARMER WATERS WILL ALSO HELP BOOST TEMPS SOMEWHAT...TO NEAR 70. && .LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/... PERSISTENT PATTERN THROUGH MUCH OF THE PERIOD AS SURFACE HIGH PRESSURE PREDOMINATES ACROSS THE NORTHEAST. IN THE UPPER LEVELS...LARGE DIFFERENCES IN UPPER PATTERN APPARENT FRI AND SAT WITH STRONGLY SUPPORTED ECMWF INDICATING LARGE SCALE TROUGH OVER THE WESTERN STATES...AND THUS STRENGTHENING RIDGE EAST. GEFS SUPPORTS THIS AS OUTLIER OPERATIONAL GFS DISPLACES UPPER TROUGH WESTWARD OFF THE WEST COAST...AND ALLOWS SHORTWAVE TO DIG ACROSS UPPER MID WEST TOWARD NORTHEAST. THIS WOULD MEAN FRONT KICKS OUT SFC HIGH. SO...GFS PROGS TROUGH OVER THE NORTHEAST...AND BUILDING RIDGE PROGGED FROM ECMWF/GEFS. STILL PLENTY OF TIME TO RESOLVE THESE DIFFERENCES...BUT OBVIOUSLY FOLLOWED HPC/ECMWF/ENSEMBLES. THIS WOULD MEAN SFC HIGH HANGING TOUGH FOR AWHILE. TAKING ALL THIS INTO ACCOUNT...DRY WEATHER ANTICIPATED FOR THE LOCAL CWA WITH THIS ANOMALOUS SFC HIGH IN PLACE OVER THE NORTHEAST. EXPECT A SLOW WARMUP THROUGH THE PERIOD WITH TEMPS NEAR TO SLIGHTLY ABOVE SEASONAL LEVELS. H8 TEMPS NEAR 13-14C THROUGH MUCH OF THE PERIOD AID IN THE MERCURY RISING WELL INTO THE 70S...AND POSSIBLY TO NEAR 80 WITH TYPICAL MIXING. IF AN INCREASE IN CLOUD COVER FROM THE SOUTH DOES OCCUR FRIDAY AND SATURDAY...TEMPS MAY FALL A FEW DEGREES SHORT...INTO THE LOWER 70S. FOR NOW THOUGH WILL LEAN TOWARD WARMER SOLUTIONS. && .AVIATION /19Z SATURDAY THROUGH THURSDAY/... THE 18Z TAF PERIOD WILL START OFF WITH BKN VFR CIGS AS A MID LEVEL DISTURBANCE MOVES THROUGH. NNW WINDS WILL GUST TO 25-30 KT MAINLY BETWEEN 18Z-20Z...AS LATEST ACARS SOUNDINGS AND RUC/NAM MODELS INDICATE BRIEF SURGE OF STRONGER WIND ALOFT BETWEEN 3-4 KFT AGL MOVING THROUGH AND MIXING DOWN TO THE SURFACE. WINDS SHOULD GRADUALLY DECREASE THIS EVENING TO UNDER 10 KT BY MIDNIGHT...TAKING LONGEST AT NYC AREA TERMINALS WHERE URBAN HEAT ISLAND PROLONGS MIXING...THEN TURN MORE N OR EVEN NNE AS HIGH PRESSURE TO THE WEST NOSES IN AT FIRST ACROSS THE INTERIOR. FLOW SLACKENS ENOUGH THAT SEA BREEZES SHOULD DEVELOP BEFORE 18Z AT KBDR/KGON...PERHAPS DELAYED AN HOUR LATER THAN USUAL. ORIENTATION OF THE SURFACE HIGH MAY ALSO PROMOTE DEVELOPMENT OF AN E-NE SOUND BREEZE AT KLGA SHORTLY BEFORE 18Z SUN...BUT CONFIDENCE LEVEL NOT HIGH ENOUGH TO INCLUDE IN TAF. OUTLOOK FOR 18Z SUN THROUGH THU...SEA BREEZES SHOULD ALSO DEVELOP LATER SUN AFTERNOON AT KJFK/KISP...AND POSSIBLY SPREAD INLAND TO KEWR/KTEB. AS MENTIONED ABOVE...KLGA MAY ALSO SEE AN E-NE SOUND BREEZE. OTHERWISE...LATE NIGHT SUB-VFR CONDITIONS IN RADIATION FOG MAY BECOME INCREASINGLY LIKELY...ESPECIALLY OUTSIDE THE NYC URBAN HEAT ISLAND BOTH TUE NIGHT AND WED NIGHT...AS LOW LEVEL MOISTURE INCREASES...WITH DEWPOINTS IN THE 50S. && .MARINE... A COLD FRONT HAS PUSHED EAST OF THE WATERS THIS AFTERNOON. THE TIGHT PRESSURE GRADIENT BETWEEN AN OFFSHORE LOW AND BUILDING HIGH PRESSURE...WILL RESULT IN NORTHWESTERLY WINDS AROUND 20 KT WITH GUSTS UP TO 30 KT. IN ADDITION...SEAS WILL BE BUILDING TO 5 FT ON THE OCEAN WATERS. THESE CONDITIONS SHOULD DIMINISH SOMEWHAT THIS EVENING...ALLOWING WINDS TO SUBSIDE BELOW SCA BY THIS EVENING EXCEPT ON THE OCEAN AND LONG ISLAND SOUTH SHORE BAYS. AS HIGH PRESSURE CONTINUES TO BUILD OVER THE AREA...WINDS AND SEAS WILL CONTINUE TO DIMINISH. EXPECT CONDITIONS TO DROP BELOW SCA LEVELS EVERYWHERE LATE TONIGHT. THIS HIGH WILL BRING TRANQUIL CONDITIONS FROM SUNDAY INTO MID WEEK...THOUGH SEAS MAY BUILD SLIGHTLY BY MID WEEK ON PERSISTENT NE-E FLOW. && .HYDROLOGY... AFTER EARLIER RAIN DUMPED LIGHT AMOUNTS WEST...AND UP TO A HALF AN INCH EAST...DRY CONDITIONS EXPECTED FOR QUITE SOMETIME. RIVER AND STREAM LEVELS SHOULD SLOWLY RECEDE THROUGH THE UPCOMING WEEK. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...NONE. NY...NONE. NJ...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 6 PM EDT THIS AFTERNOON FOR ANZ330- 335-338-340. SMALL CRAFT ADVISORY UNTIL 6 AM EDT SUNDAY FOR ANZ345-350-353- 355. && $$ SYNOPSIS...PW NEAR TERM...PW SHORT TERM...PW LONG TERM...PW AVIATION...BG MARINE...BC HYDROLOGY...PW ct AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE UPTON NY 204 PM EDT SAT SEP 15 2007 .SYNOPSIS... A COLD FRONT WILL PUSH EAST OF THE REGION BY EARLY THIS AFTERNOON...FOLLOWED BY STRONG HIGH PRESSURE BUILDING FROM THE NORTHERN PLAINS STATES AND THE COOLEST WEATHER OF THE SEASON THIS FAR. THIS HIGH WILL REMAIN OVER THE AREA THROUGH THE UPCOMING WORK WEEK...WITH GRADUALLY MODERATING TEMPERATURES BEGINNING ON MONDAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... BAND OF POST-FRONTAL LIGHT SHOWERS WAS MOVING INTO WESTERN CT/LONG ISLAND AS OF 15Z. HAVE MAINTAINED CHANCE POP FOR THOSE AREAS INTO EARLY THIS AFTERNOON...AS IT APPEARS THEY MAY NOT CLEAR FAR EASTERN SECTIONS UNTIL 1730Z-18Z. OVERCAST CONDITIONS SHOULD GIVE WAY TO PARTLY/MOSTLY SUNNY SKIES...WITH STRATOCU DEVELOPING MAINLY IN THE HIGHER ELEVATIONS. MIXING UP TO ABOUT 825 MB SHOULD YIELD MAX TEMPS A LITTLE WARMER THAN 06Z MAV NUMBERS...UPPER 60S WELL NORTH/WEST AND 70-75 ELSEWHERE...AS WELL AS MIX DOWN STRONGER WINDS FROM ALOFT...WITH GUSTS AROUND 30 MPH. && .SHORT TERM /6 PM THIS EVENING THROUGH MONDAY/... HIGH PRESSURE WILL BUILD ACROSS THE AREA THROUGH SUNDAY...THEN LIFT SLIGHTLY NORTHEAST AND ELONGATE ON MONDAY. MEANWHILE...THE COLDEST AIRMASS OF THE SEASON WILL INFILTRATE THE REGION...WITH 850 HPA TEMPERATURES DROPPING TO 2-4 DEGREES C BY TONIGHT FROM THE 13 DEGREES C OBSERVED BY THE KOKX SOUNDING LAST EVENING. LOW TEMPERATURES TONIGHT WILL DEPEND ON HOW QUICKLY THE PRESSURE GRADIENT RELAXES. BELIEVE THAT THE FLOW MAY STILL BE JUST STRONG ENOUGH TO KEEP US FROM PERFECT RADIATIONAL COOLING CONDITIONS... ESPECIALLY IN THE MORE POPULATED AREAS. HAVE THEREFORE STAYED ON THE WARM SIDE OF GUIDANCE ACROSS THE BOARD...WITH MINS RANGING FROM THE LOWER 50S IN NYC...TO MID AND UPPER 40S MOST ELSEWHERE...TO LOWER 40S ACROSS ORANGE/PUTNAM/NORTHERN FAIRFIELD/NORTHERN NEW HAVEN COUNTIES. MOST LOCALES WILL HAVE TROUBLE REACHING 70 DEGREES ON SUNDAY...AND THEN SUNDAY NIGHT...WITH LIGHT WINDS AND CLEAR SKIES WILL BE DOWNRIGHT CHILLY IN MANY SPOTS. THE AIRMASS WILL BEGIN TO MODERATE BY MONDAY...AND THIS WILL COMBINE WITH A MORE MARITIME FETCH AS THE HIGH MOVES EAST TO ALLOW TEMPS TO REBOUND BACK TOWARD CLIMATOLOGICAL AVERAGES. && .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... THE SURFACE HIGH WILL REMAIN OVER THE REGION THROUGH THE PERIOD WHILE HEIGHTS GRADUALLY RISE ALOFT...WHICH SPELLS FAIR WX WITH A GRADUAL MODERATION IN TEMPS. THIS SHOULD KEEP A COLD FRONT WELL NORTH OF THE REGION...BUT WE MAY HAVE WATCH FOR SOME UNSETTLED WX DURING THE MID WEEK PERIOD...FROM WED NIGHT INTO THU...AS PERSISTENT ONSHORE FLOW MAY ALLOW A WARM FRONT TO MOVE WESTWARD TOWARD THE COAST AND EVENTUALLY BRING LOW CLOUDS AND SHOWERS. HPC NOTES THAT MODELS ARE OVERLY BIASED TOWARD THIS WESTWARD MOTION...SO OTHER THAN SOME POSSIBLE LATE NIGHT PATCHY RADIATION FOG BY WED...WX IS MORE LIKELY THAN NOT TO REMAIN FAIR THROUGH THE UPCOMING WORK WEEK. && .AVIATION /18Z SATURDAY THROUGH THURSDAY/... THE 18Z TAF PERIOD WILL START OFF WITH BKN VFR CIGS AS A MID LEVEL DISTURBANCE MOVES THROUGH. NNW WINDS WILL GUST TO 25-30 KT MAINLY BETWEEN 18Z-20Z...AS LATEST ACARS SOUNDINGS AND RUC/NAM MODELS INDICATE BRIEF SURGE OF STRONGER WIND ALOFT BETWEEN 3-4 KFT AGL MOVING THROUGH AND MIXING DOWN TO THE SURFACE. WINDS SHOULD GRADUALLY DECREASE THIS EVENING TO UNDER 10 KT BY MIDNIGHT...TAKING LONGEST AT NYC AREA TERMINALS WHERE URBAN HEAT ISLAND PROLONGS MIXING...THEN TURN MORE N OR EVEN NNE AS HIGH PRESSURE TO THE WEST NOSES IN AT FIRST ACROSS THE INTERIOR. FLOW SLACKENS ENOUGH THAT SEA BREEZES SHOULD DEVELOP BEFORE 18Z AT KBDR/KGON...PERHAPS DELAYED AN HOUR LATER THAN USUAL. ORIENTATION OF THE SURFACE HIGH MAY ALSO PROMOTE DEVELOPMENT OF AN E-NE SOUND BREEZE AT KLGA SHORTLY BEFORE 18Z SUN...BUT CONFIDENCE LEVEL NOT HIGH ENOUGH TO INCLUDE IN TAF. OUTLOOK FOR 18Z SUN THROUGH THU...SEA BREEZES SHOULD ALSO DEVELOP LATER SUN AFTERNOON AT KJFK/KISP...AND POSSIBLY SPREAD INLAND TO KEWR/KTEB. AS MENTIONED ABOVE...KLGA MAY ALSO SEE AN E-NE SOUND BREEZE. OTHERWISE...LATE NIGHT SUB-VFR CONDITIONS IN RADIATION FOG MAY BECOME INCREASINGLY LIKELY...ESPECIALLY OUTSIDE THE NYC URBAN HEAT ISLAND BOTH TUE NIGHT AND WED NIGHT...AS LOW LEVEL MOISTURE INCREASES...WITH DEWPOINTS IN THE 50S. && .MARINE... COLD FRONT PUSHES EAST OF THE WATERS BY 17Z-18Z...WITH THE COMBO OF A TIGHT PRESSURE GRADIENT BETWEEN AN OFFSHORE LOW AND BUILDING HIGH PRESSURE...MODERATE PRESSURE RISES AND GOOD MIXING YIELDING WINDS 15-20 KT WITH GUSTS UP TO 30 KT...AND SEAS BUILDING TO 5 FT ON THE OUTER OCEAN WATERS. THESE CONDITIONS SHOULD LESSEN THIS EVENING... ALLOWING WINDS TO SUBSIDE BELOW SCA BY THIS EVENING EXCEPT ON THE OCEAN AND LONG ISLAND SOUTH SHORE BAYS. WINDS AND SEAS WILL FALL BELOW SCA ACROSS THE BOARD LATE TONIGHT AS THE HIGH BUILDS IN FROM THE WEST. THIS HIGH WILL BRING TRANQUIL CONDITIONS FROM SUNDAY INTO MID WEEK...THOUGH SEAS MAY BUILD SLIGHTLY BY MID WEEK ON PERSISTENT NE-E FLOW. && .HYDROLOGY... DRY FROM EARLY THIS AFTERNOON THROUGH NEXT FRI. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...NONE. NY...NONE. NJ...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 6 PM EDT THIS AFTERNOON FOR ANZ330-335-338-340. SMALL CRAFT ADVISORY UNTIL 6 AM EDT SUNDAY FOR ANZ345-350-353-355. && $$ AVIATION...GOODMAN ct AREA FORECAST DISCUSSION FOR THE FLORIDA KEYS NATIONAL WEATHER SERVICE KEY WEST FL 1048 AM EDT SAT SEP 15 2007 .DISCUSSION... OBSERVATIONS/TRENDS -- ALTHOUGH THE KEY WEST MORNING SOUNDING INDICATED MORE MOIST CONDITIONS IN THE LOWER TROPOSPHERE THAN 24 HOURS AGO...LATEST GOES SOUNDER DATA AND RUC OUTPUT SUGGEST A DRY POCKET BETWEEN THE BAHAMAS AND THE KEYS...WITH KEY WEST ON THE NORTHWESTERN FLANK. SURFACE OBSERVATIONS FROM THE WFO CONFIRM MOSTLY SUNNY SKIES AT PRESENT WITH MOST CUMULI OF LITTLE VERTICAL EXTENT. STILL...KEY WEST DOPPLER RADAR SCANS SHOW ISOLATED SHOWERS ACROSS THE SERVICE AREA MOVING TOWARD THE SOUTHWEST AT ABOUT 7KT. AIR TEMPERATURES HAVE RISEN INTO THE MID OR UPPER 80S AFTER OVERNIGHT LOWS NEAR 80F. CURRENT DEWPOINTS ARE IN THE MID 70S. THE RIDGE OF HIGH PRESSURE NORTH OF THE KEYS HAS WEAKENED DURING THE LAST 24 HOURS OWING TO A MIDLATITUDE TROUGH MIGRATION ACROSS THE SOUTHEASTERN UNITED STATES. AS A RESULT...MSL PRESSURES LOCALLY HAVE DROPPED ABOUT A MILLIBAR AND THE DEEP LAYER WIND HAS BACKED TO ENE THROUGH A DEEP LAYER. AFTERNOON FORECASTS -- THE LOWER KEYS CUMULUS LINE WILL PROBABLY GET A LATE START AGAIN TODAY. THE LIMITING FACTOR WILL BE LOWER TROPOSPHERIC MOISTURE CONTENT. THE KEYS WILL REMAIN ON THE NORTH OR WEST FLANK OF AN AREA OF DRY AIR EXTENDING DOWN BELOW 700MB. RUC SOUNDINGS AND OBSERVATIONAL TRENDS SUGGEST THIS DRY AIR IS AND WILL PERSIST IN TRAVERSING THE KEYS...WHEREAS...NWP OUTPUT FROM WRF/GFS SUGGEST THAT THE DRY AIR REMAINS TO THE SOUTH. WE THINK TODAY WILL BE SIMILAR TO YESTERDAY IN THAT THE ISLAND TERRAIN-INDUCED CONVECTION WILL INITIATE LATE. SUCCESSIVE CUMULUS GROWTH AND DECAY WITHIN A NARROW...SLOW-MOVING...WEAKLY SHEARED CONVECTIVE BOUNDARY LAYER OVER THE ISLANDS WILL GRADUALLY MOISTEN THE LOW LEVELS...REDUCING DRY AIR ENTRAINMENT AROUND THE TIME OF PEAK DIABATIC HEATING LATER THIS AFTERNOON. THUNDER AND SPOUTS WILL BE MOST LIKELY OVER HAWK CHANNEL JUST SOUTH OF THE ISLANDS LATE THIS AFTERNOON TO AROUND SUNSET. WE WILL THUS KEEP THE CURRENT RAIN CHANCES OF 40 PERCENT OVER THE ISLANDS WITH EMPHASIS ON "LATE". ISOLATED COVERAGE IS MORE LIKELY OVER THE STRAITS OF FLORIDA...CLOSER TO THE DRIER AIR. && .MARINE... GENTLE NORTHEAST TO EAST BREEZES WILL PREVAIL THIS AFTERNOON...WITH LOCALLY HIGHER AND GUSTIER BREEZES IN AND NEAR SHOWERS AND THUNDERSTORMS. SHOWERS AND STORMS WILL INCREASE IN COVERAGE AND INTENSITY AROUND THE ISLANDS AND NEAR THE MAINLAND LATE THIS AFTERNOON. LOWEST COVERAGE WILL BE OVER THE STRAITS OF FLORIDA BETWEEN THE KEYS AND CUBA. && .AVIATION... VFR CONDITIONS WILL PREVAIL TODAY ALONG THE AIR ROUTE FROM MIAMI TO KEY WEST...AND AT OUR ISLAND TERMINALS. SHOWERS WHICH DEVELOP ON THE MAINLAND LEG OF THE ROUTE WILL HAVE MEAN CELL MOTION APPROX 07006KT...WITH MOST TOPS AOB FL350. A CLOUD LINE IS LIKELY THIS AFTERNOON IN THE VICINITY OF THE LOWER KEYS. THIS MAY HAVE AN IMPACT ON THE KEY WEST TERMINAL. JUST CHECK THE LATEST METARS AND TAF AMENDMENTS WHEN PLANNING YOUR FLIGHT. && .KEY WATCHES/WARNINGS/ADVISORIES... FL...NONE. GM...NONE. && $$ PUBLIC/MARINE.........KASPER AVIATION/SHORT TERM...DFM DATA COLLECTION.......PARKE-ROSS VISIT US ON THE WEB AT WWW.WEATHER.GOV/KEYWEST fl AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE JACKSONVILLE FL 230 PM EDT FRI SEP 14 2007 .SHORT TERM...VISIBLE LOOP AND RADAR SHOW NMRS STORMS OVER THE FL PANHANDLE ASSOCIATED WITH VORTICITY ENERGY IN A SHORT WAVE TROUGH. THE RUC SHOWS THIS AREA WILL MOVE INTO THE SUWANNEE VALLEY AND SE GA FROM 21Z TO 03Z. REMNANTS OF HUMBERTO OVER MS/AL HAVE MERGED WITH THE COLD FRONT THAT EXTENDS THRU N GA AND SC. AN UPPER TROUGH STRETCHING FROM THE GREAT LAKES TO THE SRN MS VALLEY WILL SWEEP EWD TONIGHT AND SATURDAY PUSHING THE COLD FRONT THRU THE REGION BY EARLY SUNDAY. MOST OF THE ENERGY WITH THE FRONTAL SYSTEM WILL PASS NORTH OF THE AREA AS THE FRONT SAGS INTO THE CWA TONIGHT. SE GA WILL HAVE SCT STORMS THRU THE NIGHT THEN SCT STORMS WILL MOVE INTO NE FL EARLY SAT MORN WITH STORMS TRANSFERRING TO THE SRN PORTION SAT AFTN. ON SUN/MON A STRONG HIGH PRESSURE WILL BUILD OVER THE NE U.S. WITH A RIDGE BUILDING SOUTHWARD ALONG THE APPALACHIANS. NELY FLOW SETS UP BETWEEN THE STRENGTHENING RIDGE AND THE FRONT OFFSHORE. AS THE PRES GRAD STRENGHTENS...A NE FLOW REGIME WILL CREATE BREEZY AND OCCASIONALLY RAINY CONDS KEEPING TEMPS COOLER ESPECIALLY NEAR THE COAST. WILL GO WITH TEMPS IN THE 80S ON MONDAY ALTHOUGH THE BEACHES MAY STRUGGLE TO RISE ABOVE THE UPPER 70S. .LONG TERM...A CUT-OFF MID/UPPER LEVEL LOW IS EXPECTED TO FORM IN THE BASE OF A SHORT WAVE TROUGH NEAR THE GA COAST...THEN TRAVEL TOWARD THE WSW ACROSS THE FL PENINSULA MID WEEK AND WESTWARD ALONG THE GULF COAST THU/FRI. THE COMBINATION OF A SFC COASTAL TROUGH AMPLIFYING OFFSHORE AND HIGH PRESSURE WEDGING ALONG THE APPALACHIAN MTNS WILL RESULT IN A WET BREEZY NELY FLOW TUE/WED. WINDS WILL SHIFT TO SELY WHEN THE CSTL TROF DRIFTS TO THE WEST LATER IN THE WEEK. MODELS SUGGEST INCREASING MOISTURE WITH THE ONSHORE FLOW BUT FOR NOW WILL KEEP CHANCE POPS. TEMPS WILL BE NEAR NORMAL WHICH IS 85 AND 68 FOR JAX THIS TIME OF YEAR. && .AVIATION...LOOKING AT THE SREF QPF PROBABILITIES...WE SHOULD HAVE ANOTHER LATE START TO THE CONVECTION ACROSS THE EASTERN TAF SITES AND CONVECTION NEAR TAF START TIME FOR GNV. IN DEVELOPING SOUTHWEST FLOW...WCSB HAS MADE GOOD PROGRESS INTO THE WESTERN MOST COUNTIES AND IF THIS TREND CONTINUES...WILL NEED TO AMEND TO BRING IN TSRA AN HOUR EARLIER. OTHERWISE...THERE LOOKS TO BE SOME RESIDUAL SHRA HAS TSRA WANES DURING THE LATE EVENING MUCH LIKE LAST NIGHT. FRONT WILL MOVE THROUGH EARLY SAT AND MAY NEED TEMPO FOR CONVECTION WITH SUBSEQUENT TAF ISSUANCES. && .MARINE...A CONTINUED VERY LIGHT WIND REGIME IN STORE FOR THE NEXT 24 TO 48 HOURS AS FRONT SLIDES INTO THE AREA. EXCEPTION WILL BE THE POSSIBILITY OF A SURGE LATER THIS EVENING BUT THIS SHOULD STILL REMAIN IN THE 10 TO 15 KNOT RANGE. LOOKS LIKE THE MAIN ISSUE WILL BE THE WIND SURGE COMING IN LATE SUNDAY INTO MONDAY AS HIGH PRESSURE BUILDS DOWN THE ATLANTIC SEABOARD AND INTERACTS WITH AN INVERTED TROUGH FORMED ALONG OLD FRONTAL BOUNDARY. ONSET WITH MODELS CONTINUES TO HAVE GOOD AGREEMENT WITH GFS NOW SHOWING A STRONGER WIND FIELD SETTING UP LATE MONDAY INTO TUESDAY. WILL NOT GO AS HIGH AS THE GFS BUT DEFINITELY TREND IN THAT DIRECTION WITH 25 KNOTS LIKELY OVER THE OFFSHORE. && .PRELIMINARY POINT TEMPS/POPS... AMG 71 89 69 85 / 40 30 30 20 SSI 75 87 74 83 / 30 40 30 40 JAX 74 90 72 86 / 40 50 40 40 SGJ 74 88 74 85 / 40 50 40 40 GNV 72 90 71 89 / 40 50 40 40 OCF 73 90 71 90 / 40 50 40 40 && .JAX WATCHES/WARNINGS/ADVISORIES... FL...NONE. GA...NONE. AM...NONE. && $$ TRABERT/DEESE fl AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE JACKSONVILLE FL 1000 AM EDT FRI SEP 14 2007 .UPDATE...NO CHANGES TO FCST REQUIRED SINCE A FEW TWEAKS TO THE GRIDS ESSENTIALLY MADE NO DIFFERENCE IN VERBIAGE FOR ZONES. RADAR AND SATELLITE DEPICT A VORT MAX MOVING OVER THE FL PANHNDL THIS MORNING WITHIN SLY LLVL FLOW. RUC CARRIES THIS FEATURE EAST THEN NE THIS AFTN INTO THE SUWANNEE VALLEY AND WRN SE GA PORTION OF OUR CWA. EXCEPT FOR LOW CLOUDS AND FOG LINGERING ACRS THE FAR NRN TIER...SKIES ARE MOSTLY SUNNY THIS MORNING. THIS WILL GIVE SUFFICIENT TIME FOR HEATING TO REACH MAX TEMPS IN THE LWR 90S. THE MORNING SOUNDING SUGGESTS CAPES WILL BE ARND 3500 J/KG DURING MAX HEATING. PWAT IS 2.11 INCHES. THEREFORE EXPECT A FEW STRONG STORMS PRODUCING GUSTY WINDS AND LOCALLY HEAVY RAINS. WILL KEEP A NW TO SE POP DISTRIBUTION FOR 50% NW TO 30% SE. && .AVIATION...FOG HAS LIFTED AT TAF SITES AND VFR CONDS WILL CONTINUE UNTIL TS APPROACHES IN THE AFTN. HAVE TEMPO GROUPS FOR TS PRODUCING MVFR CONDS AFTER 20Z BEGINNING AT FL TAF SITES AND CONTINUING UNTIL 02Z AT SSI. && .MARINE...NO HEADLINES. BUOYS HAVE BEEN REPORTING SOUTH WINDS NEAR 10 KT AND A LITTLE HIGHER IN GA WATERS. SEAS ARE RUNNING 2 FT. && .PRELIMINARY POINT TEMPS/POPS... AMG 90 71 89 69 / 50 40 50 30 SSI 88 75 87 74 / 40 40 50 40 JAX 91 72 89 73 / 40 30 50 40 SGJ 89 74 88 74 / 30 30 40 30 GNV 91 72 89 71 / 40 40 50 40 OCF 92 72 89 72 / 40 30 40 30 && .JAX WATCHES/WARNINGS/ADVISORIES... FL...NONE. GA...NONE. AM...NONE. && $$ MKT fl AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE QUAD CITIES IA IL 814 PM CDT SAT SEP 15 2007 .DISCUSSION... WILL MAKE SOME FINE-TUNING TO THE GOING FCST FOR TONIGHT. MAIN ISSUES WILL BE LOCATION AND AMOUNT OF POPS. SHORWAVE MOVG ACRS SWRN CWA ATTM WITH ATTENDING -SHRA/SHRA. KDVN 88D REFLECTIVITY SUGGESTS VORT CIRCULATION IS APPROX 20 MI SSE KFFL...OR ABOUT 1 HR FASTER THAN...AND 50 MI S OF...THE RUC SOLN. AREA OF PCPN EXTENDS AS FAR N AS I-80 CORRIDOR IN WRN CWA. IN SPITE OF RELATIVELY DRY LOWER LEVELS ACRS OUR CWA...THIS WHOLE AREA OF PCPN IS MAINTAINING ITS INTENSITY LONGER THAN EXPECTED. ONE POSSIBLE CAUSE IS HIGHER MID-LEVEL MOISTURE AS INDICATED BY THE 00Z KDVN SOUNDING. SOME OF THE PCPN IS EVAPORATING...HOWEVER...BUT IS STILL REACHING THE GROUND ESCPLY UNDERNEATH THE HIGHER REFLECTIVITY ECHOES. VERTICAL TEMPERATURE PROFILES SUGGEST THAT MOST OF ANY THUNDER THAT DOES OCCUR SHOULD STAY S OF OUR CWA. THERE MAY BE SOME ISOLATED THUNDER ACRS THE FAR S SO WILL REFLECT THIS THINKING IN THE FCST. && .DVN WATCHES/WARNINGS/ADVISORIES... IA...NONE. IL...NONE. MO...NONE. && $$ 50 ia AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WICHITA KS 1246 PM CDT SAT SEP 15 2007 .AVIATION...18Z. MCS OVER EASTERN KANSAS WILL CONTINUE TO PRODUCE THUNDER NEAR OR AT THE KCNU AIRPORT. WILL INDICATE SUCH THERE. ELSEWHERE MOST CEILINGS AT 5000 FEET BUT THERE IS A SMALL AREA OF 800 FEET THAT EXTENDS FROM KEWK TO KSLN BEHIND THE STRONG CONVECTION ASSOCIATED WITH THE MCS. THE MCS SHOULD GRADUALLY MOVE SOUTHEAST AND DIMINISH LATE THIS EVENING. OVERNIGHT...ANOTHER MCS IS POSSIBLE OVER WESTERN KANSAS WHICH WOULD MOVE EAST INTO CENTRAL KANSAS. HAVE INDICATED THIS POSSIBILITY IN THE TAFS INDICATING CB. COOK && .PREV DISCUSSION... /ISSUED 1203 PM CDT SAT SEP 15 2007/ UPDATE... MCS CONTINUES OVER THE EASTERN HALF OF KANSAS. THIS CONTINUES TO BE SUPPORTED BY THE LOW LEVEL MOISTURE TRANSPORT NOTED ON THE 305K...310K...AND 315K ISENTROPIC SURFACES. CURRENT TRENDS INDICATE A MUCH COOLER DAY FOR TODAY THAN PREVIOUSLY EXPECTED. HAVE THEREFORE UPDATED THE REMAINDER OF THE DAY AND EVENING IN THE GRIDS. COOK PREV DISCUSSION... /ISSUED 914 AM CDT SAT SEP 15 2007/ UPDATE... MCS MOVING SOUTHEAST THROUGH THE FORECAST AREA WILL CONTINUE THIS MORNING. 12Z RUC INDICATES CONTINUED MOISTURE TRANSPORT THHROUGHOUT THE DAY WHICH SHOULD KEEP THE SYSTEM INTACT. HAVE THEREFORE UPDATED THE TEMPERATURE/DEWPOINT/POP/QPF GRIDS TO INDICATE SUCH. COOK PREV DISCUSSION... /ISSUED 720 AM CDT SAT SEP 15 2007/ AVIATION... FOR THE 12Z TAF SUITE...STRONG MID-LEVEL ISENTROPIC LIFT WILL CONTINUE TO SUPPORT ELEVATED CONVECTION THROUGH THE LATE MORNING HOURS FROM CENTRAL KANSAS ACROSS THE FLINT HILLS AND INTO PORTIONS OF SOUTHEAST KANSAS. THE MOIST ASCENT ROOTED AROUND 700MB HAS RESULTED IN CAPE VALUES AROUND 1000 J/KG. DRIER AIR BELOW THIS LEVEL WILL LIMIT THE LOWEST CIGS IN THE RAIN AREAS TO THE MVFR CATEGORY FOR THE MOST PART...WITH MVFR VSBYS ALSO EXPECTED IN THE LOCALLY HEAVY DOWNPOURS. IMPROVING CONDITIONS ARE EXPECTED DURING THE AFTERNOON...WITH SOUTH WINDS INCREASING ACROSS THE AREA. ISOLATED CONVECTION IS AGAIN POSSIBLE IN THE LATTER PORTION OF THE FORECAST VALID PERIOD...THOUGH HAVE OMITTED MENTION NOW TO THE LOW PROBABILITY OF OCCURRENCE. KED PREV DISCUSSION... /ISSUED 312 AM CDT SAT SEP 15 2007/ SYNOPSIS... MAIN MID/UPPER LEVEL FEATURE IS A STALLED CUTOFF/CLOSED LOW OVER NORTHWEST CA/SOUTHWEST OR. AT THE SURFACE...MASSIVE POLAR HIGH PRESSURE CONTINUES TO EASE SOUTHEAST ACROSS THE MIDWEST...IN WAKE OF A STRONG COLD FRONT CURRENTLY PROGRESSING ACROSS THE EASTERN...SOUTHEASTERN AND SOUTHERN CONUS. INCREASING WARM/MOIST ADVECTION IN THE 800-600MB LAYER IS RESULTING IN SHOWERS/EMBEDDED THUNDERSTORMS ACROSS SOUTHERN NE/NORTHWEST KANSAS EARLY THIS MORNING. KLEINSASSER DISCUSSION... FORECAST CHALLENGES/CONCERNS FOCUS AROUND SHOWER/THUNDERSTORM CHANCES TODAY THROUGH SUNDAY MORNING...THEN AGAIN TUESDAY THROUGH WEDNESDAY. STRONG WARM/MOIST ADVECTION IN THE 800-600MB LAYER SWEEPING ACROSS THE FORECAST AREA...ALONG WITH SOMEWHAT MODEST ELEVATED INSTABILITY SHOULD RESULT IN SCATTERED SHOWERS/THUNDERSTORMS THIS MORNING. THINKING BEST CHANCES WILL BE NORTH OF HIGHWAY 54/400 THIS MORNING...WITH CHANCES GENERALLY SHIFTING TO EASTERN KANSAS FOR THIS AFTERNOON. GIVEN 500-1000 J/KG OF ELEVATED CAPE...THINKING SMALL HAIL AND BRIEF HEAVY RAIN WILL BE POSSIBLE...ALONG WITH GUSTY WINDS DUE TO A DRY SUB-CLOUD LAYER. MODELS INDICATE MORE DECENT 850-650 WARM/MOIST ADVECTION AND ELEVATED INSTABILITY LATER TONIGHT...SO INTRODUCED SLIGHT CHANCE POPS AFTER MIDNIGHT GENERALLY EAST OF I-135. THINKING CHANCES WILL LINGER THROUGH SUNDAY MORNING. BY MONDAY...THE AFOREMENTIONED PACIFIC NORTHWEST CUTOFF/CLOSED LOW WILL FINALLY KICK EAST...AS IT PHASES WITH SHORTWAVE ENERGY DROPPING SOUTHEAST OUT OF THE GULF OF ALASKA. CONSEQUENTLY...SOUTHERLY FLOW AND TEMPERATURES WILL INCREASE BY SUNDAY/MONDAY. AREA STILL ANTICIPATED TO RECEIVE A GLANCING BLOW FROM SHORTWAVE ENERGY ON MONDAY NIGHT/TUESDAY...WITH AN ASSOCIATED FRONTAL BOUNDARY IMPINGING ON NORTHWEST PORTIONS OF THE FORECAST AREA. NOT TERRIBLY EXCITED ABOUT PRECIPITATION CHANCES MONDAY NIGHT-WEDNESDAY...BUT IT CERTAINLY REMAINS POSSIBLE GIVEN PROXIMITY OF BOUNDARY AND GLANCING BLOW OF SHORTWAVE ENERGY. KEPT SLIGHT CHANCE/CHANCE POPS FOR NOW. STRONG SOUTHERLY FLOW AND ABOVE NORMAL TEMPERATURES SHOULD CONTINUE THROUGH THE END OF THE WEEK...AND POSSIBLY INTO THE WEEKEND...AS A DEEP TROUGH DIGS ACROSS THE WESTERN CONUS...ALLOWING FOR MID/UPPER RIDGING TO BUILD ACROSS THE CENTRAL/EASTERN CONUS. KLEINSASSER AVIATION... EXPECT 6K TO 8K FOOT CEILINGS TO CONTINUE ACROSS THE REGION OVERNIGHT AS MID LEVEL MOISTURE CONTINUES TO OVERRUN THE SHALLOW COOL AIR IN PLACE ACROSS THE REGION. MODELS SUGGEST ISENTROPIC LIFT WILL INCREASE VERY EARLY IN THE MORNING IN SOUTHWEST KS...WITH THIS LIFT MOVING OVER MOST OF THE AREA BY DAYBREAK. THIS LIFT WILL HELP SATURATE THE LOWER LAYERS AND STEEPEN LAPSE RATES ENOUGH FOR A SHRA AND ISOLATED TSRA CHANCE BEGINNING AFTER 09Z. WILL INCLUDE A VCTS CHANCE IN THE KRSL/KSLN AND KICT TAFS. EPS/BDK && .PRELIMINARY POINT TEMPS/POPS... WICHITA-KICT 69 61 88 67 / 20 20 10 10 HUTCHINSON 69 60 89 67 / 40 10 10 10 NEWTON 68 60 88 66 / 90 20 10 10 ELDORADO 68 60 88 67 / 90 20 20 10 WINFIELD-KWLD 69 61 88 67 / 30 20 10 0 RUSSELL 73 59 90 66 / 30 10 10 10 GREAT BEND 73 59 90 66 / 20 10 10 10 SALINA 68 60 89 67 / 100 10 10 10 MCPHERSON 69 60 89 66 / 90 10 10 10 COFFEYVILLE 64 60 85 67 / 90 20 20 0 CHANUTE 61 59 85 67 / 100 20 20 10 IOLA 60 59 85 67 / 100 20 20 10 PARSONS-KPPF 62 60 85 67 / 100 20 20 10 && .ICT WATCHES/WARNINGS/ADVISORIES... NONE. && $$ ks AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WICHITA KS 1203 PM CDT SAT SEP 15 2007 .UPDATE... MCS CONTINUES OVER THE EASTERN HALF OF KANSAS. THIS CONTINUES TO BE SUPPORTED BY THE LOW LEVEL MOISTURE TRANSPORT NOTED ON THE 305K...310K...AND 315K ISENTROPIC SURFACES. CURRENT TRENDS INDICATE A MUCH COOLER DAY FOR TODAY THAN PREVIOUSLY EXPECTED. HAVE THEREFORE UPDATED THE REMAINDER OF THE DAY AND EVENING IN THE GRIDS. COOK && .PREV DISCUSSION... /ISSUED 914 AM CDT SAT SEP 15 2007/ UPDATE... MCS MOVING SOUTHEAST THROUGH THE FORECAST AREA WILL CONTINUE THIS MORNING. 12Z RUC INDICATES CONTINUED MOISTURE TRANSPORT THHROUGHOUT THE DAY WHICH SHOULD KEEP THE SYSTEM INTACT. HAVE THEREFORE UPDATED THE TEMPERATURE/DEWPOINT/POP/QPF GRIDS TO INDICATE SUCH. COOK PREV DISCUSSION... /ISSUED 720 AM CDT SAT SEP 15 2007/ AVIATION... FOR THE 12Z TAF SUITE...STRONG MID-LEVEL ISENTROPIC LIFT WILL CONTINUE TO SUPPORT ELEVATED CONVECTION THROUGH THE LATE MORNING HOURS FROM CENTRAL KANSAS ACROSS THE FLINT HILLS AND INTO PORTIONS OF SOUTHEAST KANSAS. THE MOIST ASCENT ROOTED AROUND 700MB HAS RESULTED IN CAPE VALUES AROUND 1000 J/KG. DRIER AIR BELOW THIS LEVEL WILL LIMIT THE LOWEST CIGS IN THE RAIN AREAS TO THE MVFR CATEGORY FOR THE MOST PART...WITH MVFR VSBYS ALSO EXPECTED IN THE LOCALLY HEAVY DOWNPOURS. IMPROVING CONDITIONS ARE EXPECTED DURING THE AFTERNOON...WITH SOUTH WINDS INCREASING ACROSS THE AREA. ISOLATED CONVECTION IS AGAIN POSSIBLE IN THE LATTER PORTION OF THE FORECAST VALID PERIOD...THOUGH HAVE OMITTED MENTION NOW TO THE LOW PROBABILITY OF OCCURRENCE. KED PREV DISCUSSION... /ISSUED 312 AM CDT SAT SEP 15 2007/ SYNOPSIS... MAIN MID/UPPER LEVEL FEATURE IS A STALLED CUTOFF/CLOSED LOW OVER NORTHWEST CA/SOUTHWEST OR. AT THE SURFACE...MASSIVE POLAR HIGH PRESSURE CONTINUES TO EASE SOUTHEAST ACROSS THE MIDWEST...IN WAKE OF A STRONG COLD FRONT CURRENTLY PROGRESSING ACROSS THE EASTERN...SOUTHEASTERN AND SOUTHERN CONUS. INCREASING WARM/MOIST ADVECTION IN THE 800-600MB LAYER IS RESULTING IN SHOWERS/EMBEDDED THUNDERSTORMS ACROSS SOUTHERN NE/NORTHWEST KANSAS EARLY THIS MORNING. KLEINSASSER DISCUSSION... FORECAST CHALLENGES/CONCERNS FOCUS AROUND SHOWER/THUNDERSTORM CHANCES TODAY THROUGH SUNDAY MORNING...THEN AGAIN TUESDAY THROUGH WEDNESDAY. STRONG WARM/MOIST ADVECTION IN THE 800-600MB LAYER SWEEPING ACROSS THE FORECAST AREA...ALONG WITH SOMEWHAT MODEST ELEVATED INSTABILITY SHOULD RESULT IN SCATTERED SHOWERS/THUNDERSTORMS THIS MORNING. THINKING BEST CHANCES WILL BE NORTH OF HIGHWAY 54/400 THIS MORNING...WITH CHANCES GENERALLY SHIFTING TO EASTERN KANSAS FOR THIS AFTERNOON. GIVEN 500-1000 J/KG OF ELEVATED CAPE...THINKING SMALL HAIL AND BRIEF HEAVY RAIN WILL BE POSSIBLE...ALONG WITH GUSTY WINDS DUE TO A DRY SUB-CLOUD LAYER. MODELS INDICATE MORE DECENT 850-650 WARM/MOIST ADVECTION AND ELEVATED INSTABILITY LATER TONIGHT...SO INTRODUCED SLIGHT CHANCE POPS AFTER MIDNIGHT GENERALLY EAST OF I-135. THINKING CHANCES WILL LINGER THROUGH SUNDAY MORNING. BY MONDAY...THE AFOREMENTIONED PACIFIC NORTHWEST CUTOFF/CLOSED LOW WILL FINALLY KICK EAST...AS IT PHASES WITH SHORTWAVE ENERGY DROPPING SOUTHEAST OUT OF THE GULF OF ALASKA. CONSEQUENTLY...SOUTHERLY FLOW AND TEMPERATURES WILL INCREASE BY SUNDAY/MONDAY. AREA STILL ANTICIPATED TO RECEIVE A GLANCING BLOW FROM SHORTWAVE ENERGY ON MONDAY NIGHT/TUESDAY...WITH AN ASSOCIATED FRONTAL BOUNDARY IMPINGING ON NORTHWEST PORTIONS OF THE FORECAST AREA. NOT TERRIBLY EXCITED ABOUT PRECIPITATION CHANCES MONDAY NIGHT-WEDNESDAY...BUT IT CERTAINLY REMAINS POSSIBLE GIVEN PROXIMITY OF BOUNDARY AND GLANCING BLOW OF SHORTWAVE ENERGY. KEPT SLIGHT CHANCE/CHANCE POPS FOR NOW. STRONG SOUTHERLY FLOW AND ABOVE NORMAL TEMPERATURES SHOULD CONTINUE THROUGH THE END OF THE WEEK...AND POSSIBLY INTO THE WEEKEND...AS A DEEP TROUGH DIGS ACROSS THE WESTERN CONUS...ALLOWING FOR MID/UPPER RIDGING TO BUILD ACROSS THE CENTRAL/EASTERN CONUS. KLEINSASSER AVIATION... EXPECT 6K TO 8K FOOT CEILINGS TO CONTINUE ACROSS THE REGION OVERNIGHT AS MID LEVEL MOISTURE CONTINUES TO OVERRUN THE SHALLOW COOL AIR IN PLACE ACROSS THE REGION. MODELS SUGGEST ISENTROPIC LIFT WILL INCREASE VERY EARLY IN THE MORNING IN SOUTHWEST KS...WITH THIS LIFT MOVING OVER MOST OF THE AREA BY DAYBREAK. THIS LIFT WILL HELP SATURATE THE LOWER LAYERS AND STEEPEN LAPSE RATES ENOUGH FOR A SHRA AND ISOLATED TSRA CHANCE BEGINNING AFTER 09Z. WILL INCLUDE A VCTS CHANCE IN THE KRSL/KSLN AND KICT TAFS. EPS/BDK && .PRELIMINARY POINT TEMPS/POPS... WICHITA-KICT 69 61 88 67 / 20 20 10 10 HUTCHINSON 69 60 89 67 / 40 10 10 10 NEWTON 68 60 88 66 / 90 20 10 10 ELDORADO 68 60 88 67 / 90 20 20 10 WINFIELD-KWLD 69 61 88 67 / 30 20 10 0 RUSSELL 73 59 90 66 / 30 10 10 10 GREAT BEND 73 59 90 66 / 20 10 10 10 SALINA 68 60 89 67 / 100 10 10 10 MCPHERSON 69 60 89 66 / 90 10 10 10 COFFEYVILLE 64 60 85 67 / 90 20 20 0 CHANUTE 61 59 85 67 / 100 20 20 10 IOLA 60 59 85 67 / 100 20 20 10 PARSONS-KPPF 62 60 85 67 / 100 20 20 10 && .ICT WATCHES/WARNINGS/ADVISORIES... NONE. && $$ ks AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WICHITA KS 914 AM CDT SAT SEP 15 2007 .UPDATE... MCS MOVING SOUTHEAST THROUGH THE FORECAST AREA WILL CONTINUE THIS MORNING. 12Z RUC INDICATES CONTINUED MOISTURE TRANSPORT THHROUGHOUT THE DAY WHICH SHOULD KEEP THE SYSTEM INTACT. HAVE THEREFORE UPDATED THE TEMPERATURE/DEWPOINT/POP/QPF GRIDS TO INDICATE SUCH. KRC && .PREV DISCUSSION... /ISSUED 720 AM CDT SAT SEP 15 2007/ AVIATION... FOR THE 12Z TAF SUITE...STRONG MID-LEVEL ISENTROPIC LIFT WILL CONTINUE TO SUPPORT ELEVATED CONVECTION THROUGH THE LATE MORNING HOURS FROM CENTRAL KANSAS ACROSS THE FLINT HILLS AND INTO PORTIONS OF SOUTHEAST KANSAS. THE MOIST ASCENT ROOTED AROUND 700MB HAS RESULTED IN CAPE VALUES AROUND 1000 J/KG. DRIER AIR BELOW THIS LEVEL WILL LIMIT THE LOWEST CIGS IN THE RAIN AREAS TO THE MVFR CATEGORY FOR THE MOST PART...WITH MVFR VSBYS ALSO EXPECTED IN THE LOCALLY HEAVY DOWNPOURS. IMPROVING CONDITIONS ARE EXPECTED DURING THE AFTERNOON...WITH SOUTH WINDS INCREASING ACROSS THE AREA. ISOLATED CONVECTION IS AGAIN POSSIBLE IN THE LATTER PORTION OF THE FORECAST VALID PERIOD...THOUGH HAVE OMITTED MENTION NOW TO THE LOW PROBABILITY OF OCCURRENCE. KED PREV DISCUSSION... /ISSUED 312 AM CDT SAT SEP 15 2007/ SYNOPSIS... MAIN MID/UPPER LEVEL FEATURE IS A STALLED CUTOFF/CLOSED LOW OVER NORTHWEST CA/SOUTHWEST OR. AT THE SURFACE...MASSIVE POLAR HIGH PRESSURE CONTINUES TO EASE SOUTHEAST ACROSS THE MIDWEST...IN WAKE OF A STRONG COLD FRONT CURRENTLY PROGRESSING ACROSS THE EASTERN...SOUTHEASTERN AND SOUTHERN CONUS. INCREASING WARM/MOIST ADVECTION IN THE 800-600MB LAYER IS RESULTING IN SHOWERS/EMBEDDED THUNDERSTORMS ACROSS SOUTHERN NE/NORTHWEST KANSAS EARLY THIS MORNING. KLEINSASSER DISCUSSION... FORECAST CHALLENGES/CONCERNS FOCUS AROUND SHOWER/THUNDERSTORM CHANCES TODAY THROUGH SUNDAY MORNING...THEN AGAIN TUESDAY THROUGH WEDNESDAY. STRONG WARM/MOIST ADVECTION IN THE 800-600MB LAYER SWEEPING ACROSS THE FORECAST AREA...ALONG WITH SOMEWHAT MODEST ELEVATED INSTABILITY SHOULD RESULT IN SCATTERED SHOWERS/THUNDERSTORMS THIS MORNING. THINKING BEST CHANCES WILL BE NORTH OF HIGHWAY 54/400 THIS MORNING...WITH CHANCES GENERALLY SHIFTING TO EASTERN KANSAS FOR THIS AFTERNOON. GIVEN 500-1000 J/KG OF ELEVATED CAPE...THINKING SMALL HAIL AND BRIEF HEAVY RAIN WILL BE POSSIBLE...ALONG WITH GUSTY WINDS DUE TO A DRY SUB-CLOUD LAYER. MODELS INDICATE MORE DECENT 850-650 WARM/MOIST ADVECTION AND ELEVATED INSTABILITY LATER TONIGHT...SO INTRODUCED SLIGHT CHANCE POPS AFTER MIDNIGHT GENERALLY EAST OF I-135. THINKING CHANCES WILL LINGER THROUGH SUNDAY MORNING. BY MONDAY...THE AFOREMENTIONED PACIFIC NORTHWEST CUTOFF/CLOSED LOW WILL FINALLY KICK EAST...AS IT PHASES WITH SHORTWAVE ENERGY DROPPING SOUTHEAST OUT OF THE GULF OF ALASKA. CONSEQUENTLY...SOUTHERLY FLOW AND TEMPERATURES WILL INCREASE BY SUNDAY/MONDAY. AREA STILL ANTICIPATED TO RECEIVE A GLANCING BLOW FROM SHORTWAVE ENERGY ON MONDAY NIGHT/TUESDAY...WITH AN ASSOCIATED FRONTAL BOUNDARY IMPINGING ON NORTHWEST PORTIONS OF THE FORECAST AREA. NOT TERRIBLY EXCITED ABOUT PRECIPITATION CHANCES MONDAY NIGHT-WEDNESDAY...BUT IT CERTAINLY REMAINS POSSIBLE GIVEN PROXIMITY OF BOUNDARY AND GLANCING BLOW OF SHORTWAVE ENERGY. KEPT SLIGHT CHANCE/CHANCE POPS FOR NOW. STRONG SOUTHERLY FLOW AND ABOVE NORMAL TEMPERATURES SHOULD CONTINUE THROUGH THE END OF THE WEEK...AND POSSIBLY INTO THE WEEKEND...AS A DEEP TROUGH DIGS ACROSS THE WESTERN CONUS...ALLOWING FOR MID/UPPER RIDGING TO BUILD ACROSS THE CENTRAL/EASTERN CONUS. KLEINSASSER AVIATION... EXPECT 6K TO 8K FOOT CEILINGS TO CONTINUE ACROSS THE REGION OVERNIGHT AS MID LEVEL MOISTURE CONTINUES TO OVERRUN THE SHALLOW COOL AIR IN PLACE ACROSS THE REGION. MODELS SUGGEST ISENTROPIC LIFT WILL INCREASE VERY EARLY IN THE MORNING IN SOUTHWEST KS...WITH THIS LIFT MOVING OVER MOST OF THE AREA BY DAYBREAK. THIS LIFT WILL HELP SATURATE THE LOWER LAYERS AND STEEPEN LAPSE RATES ENOUGH FOR A SHRA AND ISOLATED TSRA CHANCE BEGINNING AFTER 09Z. WILL INCLUDE A VCTS CHANCE IN THE KRSL/KSLN AND KICT TAFS. EPS/BDK && .PRELIMINARY POINT TEMPS/POPS... WICHITA-KICT 73 62 88 67 / 50 20 10 10 HUTCHINSON 73 61 89 67 / 70 10 10 10 NEWTON 72 61 88 66 / 90 20 10 10 ELDORADO 72 61 88 67 / 80 20 20 10 WINFIELD-KWLD 74 62 88 67 / 20 20 10 0 RUSSELL 73 60 90 66 / 70 10 10 10 GREAT BEND 74 60 90 66 / 60 10 10 10 SALINA 71 61 89 67 / 100 20 10 10 MCPHERSON 72 61 89 66 / 100 20 10 10 COFFEYVILLE 71 61 85 67 / 20 20 20 0 CHANUTE 70 60 85 67 / 60 20 20 10 IOLA 69 60 85 67 / 90 20 20 10 PARSONS-KPPF 71 61 85 67 / 20 20 20 10 && .ICT WATCHES/WARNINGS/ADVISORIES... NONE. && $$ ks AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE PADUCAH KY 730 AM CDT FRI SEP 14 2007 .UPDATE... MINOR UPDATE TO ADDRESS TRANSITIONAL SENSIBLE WEATHER TRENDS IN ADVANCE OF APPROACHING COLD FRONT. && .DISCUSSION... CURRENT SHOWERS ON TRACK TO EXIT WESTERN KENTUCKY BEFORE 1 PM...SO LITTLE MODIFICATION MADE TO COVERAGE/PROBABILITY OF SHOWER ACTIVITY THIS MORNING. THE STRATUS /MENTIONED IN PREVIOUS DISCUSSION/ AND PATCHY FOG CONTINUES TO BE ON THE MOVE THIS MORNING AND SHOULD THIN OUT ACROSS MOST AREAS NO LATER THAN 15Z /10 AM/. THE SECOND WAVE OF CLOUD COVER WILL SHOW UP AS THE FRONTAL ZONE APPROACHES THE AREA LATER THIS MORNING. THIS MAY RETARD TEMPERATURES SLIGHTLY...BUT STILL BELIEVE LOW TO MID 80S POSSIBLE. THE LATEST GFS MOS/LAMP GUIDANCE SHOW MID 80S STILL LIKELY...WHILE THE COOLER ETA/NGM MOS GUIDANCE HOLD TEMPERATURES NEAR THE 80 DEGREE MARK THIS AFTERNOON. IT WILL BE A RACE TO SEE IF COLD AIR ADVECTION TEMPERS MAX TEMPERATURES TODAY. MINOR TEMPORAL/SPATIAL ADJUSTMENTS WERE MADE TO WIND GUSTS AND MANUALLY EDITED INTO ZONE FORECAST PACKAGE. AS AN ADDITIONAL ITEM NOT INCLUDED IN THE ORIGINAL DISCUSSION EARLIER THIS MORNING...THE MAJORITY OF THE WEATHER SYSTEMS IN THE SHORT TERM WILL BE PUSHED INTO THE WESTERN COAST AND RIDE ACROSS A MEAN RIDGE. MAJOR PIVOT POINT FOR CYCLONIC FLOW RECENTLY IN THE NORTHERN HEMISPHERE WAS LOCATED NEAR 178 DEGREES WEST/65 DEGREES NORTH...WITH ANTICYCLONIC COUNTERPART NEAR 110W/28N. WITH RESPECT TO MODEL GUIDANCE PREFERENCES WITH MORNING PACKAGE...LEANED TOWARD A RUC/NAM/ECMWF BLEND IN THE SHORT TERM AND A ECMWF/GFS BLEND IN THE MEDIUM RANGE FORECAST. && .PREV DISCUSSION... /ISSUED 347 AM CDT FRI SEP 14 2007/ DISCUSSION... CURRENT SHOWER ACTIVITY FROM THE REMNANTS OF HUMBERTO DEVELOPING OVER THE SERN PORTION OF THE WFO PAH FORECAST AREA ALONG THE DEFORMATION ZONE ALONG THE NRN EDGE OF THE TROUGH/LOW. THIS FEATURE SHOULD CONTINUE TO MOVE OFF TO THE EAST THROUGH THE MORNING HOURS...KEEPING THE BEST CHANCE FOR RAIN LIMITED TO THE WRN KY/WRN TN BORDER COUNTIES. ANY MEASURABLE RAIN SHOULD EXIT THE REST OF THE WFO PAH FORECAST AREA BY AFTERNOON. FOR TODAY...THERE WILL BE TRANSITIONAL ZONE ALONG AND IN ADVANCE OF THE LEADING EDGE OF THE COLD FRONT...WHERE FRONTAL COMPRESSION AND INSOLATION WILL LEAD TO A NARROW ZONE OF WARMER THAN NORMAL TEMPERATURES /MID 80S/ IN A SW TO NELY FASHION ACROSS THE WFO PAH FORECAST AREA TODAY. THERE MAY BE A BRIEF PERIOD OF STRATUS DEVELOPMENT IN THE WAKE OF THE BAROCLINIC LEAF CLOUD DECK BETWEEN 12-14Z THIS MORNING...BUT THIS CLOUD COVER SHOULD BURN OFF ACROSS SERN MO/SRN IL/SWRN IN. THE NEXT BATCH OF CLOUD COVER SHOULD ARRIVE ALONG THE 800-600 MB FRONTAL SLOPE...WHERE PARCELS WILL CONTINUE TO BE LIFTED WITH MEAGER MOISTURE AVAILABLE. THERE WAS SOME UNCERTAINTY WHETHER OPAQUE CLOUD COVER PERCENTAGE WOULD REACH THE LEVEL OF MOSTLY CLOUDY ACROSS THE NRN PORTION OF THE WFO PAH FORECAST AREA AROUND THE NOON HOUR...BUT AT THIS TIME I DECIDED TO ERR ON LESSER CLOUD COVER AS MOISTURE DECREASES WITH TIME. I ATTEMPTED TO DISPLAY THE TRANSITION IN CLOUD COVER FROM THE DEPARTING CLOUD DECK ASSOCIATED WITH THE MOISTURE FROM HUMBERTO AND THE MOISTURE TIED WITH THE SHARP TROUGH MOVING IN WITH THE FRONT FROM THE NORTH. THE WFO PAH FORECAST AREA SHOULD SEE NWLY WIND GUSTS BETWEEN 18-22 KNOTS WITH THE PASSAGE OF THE UPPER LEVEL FRONTAL BOUNDARY LATE THIS MORNING AND EARLY THIS AFTERNOON. THESE GUSTS MAY LINGER INTO THE EARLY EVENING ACROSS THE SOUTHERN COUNTIES OF THE WFO PAH FORECAST AREA. PURE EXTRAPOLATION PLACES THE AXIS OF THE 700 MB FRONT INTO THE WFO PAH FORECAST AREA BY 20Z...WHICH SHOULD HERALD THE TRAILING EDGE OF THE CLOUD COVER/WIND GUSTS THROUGH THE FORECAST AREA. THE NEXT CHALLENGE IN THE FORECAST WILL BE THE CLOSED LOW FOUND ALONG THE NRN CA COAST AT 00Z FRIDAY. THIS FEATURE WILL RIDE A LOW AMPLITUDE RIDGE TONIGHT AND EARLY SATURDAY...DEVELOPING INTO A SMALL WAVE IN MODIFIED NWLY FLOW OVER THE MID MS VALLEY SATURDAY EVENING. ALTHOUGH THERE IS SOME LIFT AND MOISTURE ASSOCIATED WITH THIS FEATURE...ANY MEASURABLE PRECIPITATION SHOULD REMAIN NORTH OF THE WFO PAH FORECAST AREA. I CANNOT RULE OUT SPRINKLES OVER SERN MO/SRN IL/SWRN IN...BETWEEN MIDNIGHT AND 7 AM ON SUNDAY...BUT AT THIS TIME...BELIEVE THE GREATEST CHANGE FOR THE AREA WILL JUST BE AN TEMPORARY INCREASE IN CLOUD COVER. I PREFER THE ECMWF/SREF SOLUTION VS. THE 12KM NAM/40 KM GFS WITH THIS SYSTEM. OTHER THAN THE THE PASSAGE OF THE SATURDAY NIGHT WEATHER SYSTEM TO THE NORTH OF THE WFO PAH FORECAST AREA...DRY CONDITION SHOULD PREVAIL THROUGH MIDWEEK. SOME NOTICEABLE ADJUSTMENTS WERE MADE TO THE SATURDAY MAX TEMPERATURES AND SUNDAY MAX/MIN TEMPERATURES TO ACCOUNT FOR THE DRIER AIR INTRUSION AND MAXIMIZED INSOLATION. I DO HAVE SOME CONCERN THAT DEWPOINTS MAY STILL BE A LITTLE TOO HIGH ON SATURDAY /SEE FIRE WEATHER DISCUSSION/...BUT WILL WAIT AND SEE. NO ALTERATIONS MADE TO FORECAST BEYOND TUESDAY WITH THIS PACKAGE. AVIATION... AT 07Z...THE NRN LIMITS OF TROPICALLY BASED HUMBERTO MOISTURE HAD MANAGED TO WORK ITS WAY INTO/ACROSS THE SRN 1/2 OF TWEB ROUTE 232...AND EXTENDED NORTH AND EAST ACROSS THE PENNYRILE OF WKY. VFR CIGS THE RULE BUT ISOLD IFR CIGS WITH MVFR VSBYS IN -SHRA/BR WAS NUDGING INTO THE BOOTHEEL JUST SOUTH OF CGI...WHERE THE NOSE OF 60+F SURFACE TDS HAD PUSHED. COLD FRONT TO THE NW WAS LOCATED FROM SGI IL TO UIN TO MCI MO. THE RAPIDLY MOVING FRONT WILL DRIVE ACROSS THE PAH FLIGHT AREA EARLY IN THE DAY...EFFECTIVELY AIDING THE EWARD TRANSLATION OF THE TROPICAL MOISTURE TO POINTS EAST OF OUR TAF SITES AND FLIGHT ROUTES. THEREFORE WILL ONLY CARRY BRIEF EARLY MORNING MENTION FOR AFOREMENTIONED CONDITIONS IN TAFS AND SRN 1/2 TWEB 232/FAR ERN TWEB 236...AFTER WHICH FROPA SHIFTS SLYS TO NWLYS ALBEIT W/GUSTS TO NR 20 KTS ON THE MIX DOWN. BY LATE IN THE FLIGHT FORECAST...ANY LINGERING FRONTAL/POST FRONTAL VFR CIGS SHOULD BE SCOURED/SCOURING OUT TO SCT/SKC W/DIMINISHING WINDS AND P6SM FOR THE EXTENDED PLANNING PERIOD. FIRE WEATHER... MAIN FORECAST CONCERN IS THE DEGREE OF DRY AIR INTRUSION DURING THE DAY ON SATURDAY. THE DEGREE OF VERTICAL MIXING AND ADVECTION OF LOWER DEWPOINTS SUGGESTED BY THE 00Z FRI 12KM NAM AND 21Z THU SREF LEADS ME TO BELIEVE THAT MY SURFACE DEWPOINTS MAY STILL BE TOO HIGH. THIS COULD LEAD TO MINIMUM DAYTIME RELATIVE HUMIDITY VALUES IN SRN IL TOWARD THE MO BOOTHEEL DROPPING INTO THE UPPER TEENS OR LOWER 20S SATURDAY AFTERNOON. LUCKILY...WIND SPEEDS SHOULD BE LOW ENOUGH TO REDUCE ELEVATED FIRE DANGER CONCERNS. LATER SHIFTS WILL NEED TO MONITOR UPSTREAM DEWPOINT TRENDS. && .PAH WATCHES/WARNINGS/ADVISORIES... KY...NONE. MO...NONE. IL...NONE. IN...NONE. && $$ SHORT/LONG TERM...SMITH AVIATION...DH ky AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MARQUETTE MI 725 PM EDT SAT SEP 15 2007 .SHORT TERM (TONIGHT AND SUN)... TEMPS AND FROST POTENTIAL TONIGHT ARE THE MAIN FCST ISSUES. WATER VAPOR IMAGERY AND RUC ANALYSIS SHOW NW FLOW INTO THE GREAT LAKES BTWN A RIDGE OVER SW CANADA AND A TROF OVER ERN CANADA. A SHORTWAVE IS HEADING SE THRU MANITOBA...BUT IT IS PRODUCING NOTHING MORE THAN SOME CI OVER NRN MN INTO WRN UPPER MI AND ADJACENT ONTARIO. CLOSER TO HOME...STRATOCU QUICKLY DEVELOPED THIS MORNING OVER THE W AND NCNTRL FCST AREA SOON AFTER SUNRISE. THOSE CLOUDS HAVE RAPIDLY DISSIPATED IN THE LAST FEW HRS AS LOW-LEVEL MOISTURE MIXED OUT AND WAA REGIME BEGAN. HIGH PRES CURRENTLY CENTERED OVER THE MID MISSISSIPPI VALLEY WILL MOVE TO THE UPPER OHIO VALLEY BY SUN MORNING. WITH THE HIGH MOVING FARTHER AWAY...TONIGHT WILL NOT BE AN IDEAL RADIATIONAL COOLING NIGHT AS SW WINDS INCREASE BTWN THE DEPARTING HIGH AND A LOW PRES TROUGH DROPPING S THRU ONTARIO. OF COURSE...MOST OF THE INCREASE IN WINDS WILL OCCUR JUST OFF THE SFC AS NOCTURNAL INVERSION DEVELOPS. STILL...ENOUGH MECHANICAL MIXING WILL OCCUR TO KEEP THE WIND STIRRING A BIT AT THE SFC. IN THIS SITUATION...THE SCNTRL FCST AREA SHOULD BE COLDEST WITH THE BEST OPPORTUNITY TO DECOUPLE QUICKLY THIS EVENING BEFORE THE HIGH MOVES FARTHER AWAY. INHERITED FCST LOOKED TO HAVE A GOOD HANDLE ON THIS SCENARIO WITH TEMPS AT THE LOWEST AROUND 35/36F IN THE TYPICAL COLD SPOTS. SOME PATCHY FROST WILL BE POSSIBLE IN THOSE AREAS. NICE WARMUP ON TAP FOR SUN UNDER SW FLOW WITH 850MB TEMPS ABOUT 7C HIGHER SUN AFTN THAN THIS AFTN. OTHER THAN SOME CI AT TIMES AND MAYBE SOME SCT CU IN THE AFTN...THERE SHOULD BE PLENTY OF SUNSHINE. MIXING TO AROUND 800MB ON NAM/GFS FCST SOUNDINGS YIELDS HIGH TEMPS GENERALLY IN THE UPPER 60S WHICH IS CLOSE TO MOS GUIDANCE NUMBERS. .LONG TERM (SUN NIGHT THROUGH NEXT SAT)... SUN NIGHT INTO MON...THE UPPER MIDWEST AND GREAT LAKES REMAINS UNDER A WARM ADVECTION PERIOD DURING THIS PERIOD...DUE TO TROUGHING OVER THE WESTERN U.S. PUSHING EASTWARD. SUN NIGHT AT THIS POINT APPEARS TO BE DRY WITH THE DRY AIRMASS FROM SUN FIRMLY IN PLACE. STRONGEST WARM ADVECTION TO SUPPORT THE DEVELOPMENT OF PCPN APPEARS TO BE OVER WESTERN MINNESOTA SUN NIGHT. HOWEVER...ON MON...THIS STRONGEST WARM ADVECTION ZONE SHIFTS INTO UPPER MICHIGAN WITH 850MB TEMPS CLIMBING FROM 10-12C AT 12Z MON TO AROUND 16C AT 00Z TUE. IN ADDITION...A SHRTWV IS PROGGED TO EJECT OUT OF THE WESTERN TROUGH...MOVING INTO NE MN AT 00Z TUE. THE COMBINATION OF THIS SHRTWV AND THE WARM ADVECTION MAY GENERATE SOME SHOWERS AND THUNDERSTORMS FROM CENTRAL MN INTO WESTERN LAKE SUPERIOR/WESTERN UPPER MI MON AFTERNOON AS INDICATED BY THE GFS/UKMET...AND THUS HAVE INCLUDED POPS FOR THIS. MOSTLY CLEAR SKIES...PRECIPITABLE WATER BETWEEN 0.50-0.60 INCH AND A GENERAL S TO SW WIND SUPPORTS HAVING MID 40S TEMPS INLAND (SHOWN BY MET/MAV AND BIAS CORRECTED GUIDANCE). ALTHOUGH 850MB TEMPS BECOME QUITE WARM ON MON...INCREASING CLOUDS...ESPECIALLY IN THE WESTERN U.P...MAY HAMPER THOSE WARM TEMPS FROM BEING REALIZED. MAV GUIDANCE VALUES SEEM REASONABLE BASED ON THE CLOUD COVER AND WIND FORECAST. MON NIGHT INTO TUE...SHRTWV RESPONSIBLE FOR WESTERN LAKE SUPERIOR CONVECTION MON AFTERNOON WILL CROSS LAKE SUPERIOR MON NIGHT... REACHING NE ONTARIO 12Z TUE. SHOWERS AND THUNDERSTORMS SHOULD ACCOMPANY THE SHRTWV...SUPPORTED BY WARM ADVECTION. THUS...CHANCE POPS FOR MON NIGHT LOOK GOOD...THOUGH HAVE INCLUDED A DIMINISHING TREND AFTER 06Z OVER THE SOUTH CENTRAL PORTION OF THE CWA. ON TUE...MORE SHRTWVS...INCLUDING THE MAIN PIECE OF SHRTWV ENERGY FROM THE WESTERN TROUGH (CURRENTLY IN NW CALIFORNIA ON WATER VAPOR)... WILL BE LIFTING ALONG THE SAME PATH THE PREVIOUS SHRTWV TOOK DUE TO SW FLOW ALOFT. ALONG THIS PATH...GFS/NAM/UKMET INDICATE PRECIPITABLE WATER OF 1.5-1.75 INCHES...SUGGESTING CONTINUED BOUTS OF CONVECTION AND POTENTIAL FOR HEAVY RAIN. MUCH OF THE CONVECTION SHOULD BE CONFINED TO AREAS FROM CENTRAL LAKE SUPERIOR INTO NW WI AND WEST. HOWEVER...HAVE INCLUDED POPS FOR THE WESTERN U.P....AND ESPECIALLY IN THE AFTERNOON AS THE HIGH PRECIPITABLE WATER AXIS SHIFTS SLIGHTLY EAST. TEMPERATURES MON NIGHT SHOULD BE FAIRLY WARM...THANKS TO INCREASING DEWPOINTS AND A BREEZY SOUTH WIND. FOLLOWED THE WARMER MAV GUIDANCE FOR LOWS. TUES HIGHS ARE TRICKY...ESPECIALLY SINCE 850MB TEMPS ARE PROGGED TO REMAIN AROUND 16C. IF FULL SUN COULD BE REALIZED...THE RECORD HIGH FOR THE OFFICE WOULD BE IN JEOPARDY. HOWEVER...IT APPEARS THE SHRTWVS WILL PROVIDE PLENTY OF CLOUD COVER...ESPECIALLY IN THE WEST TO PREVENT RECORD HIGHS FROM OCCURRING. NONETHELESS... READINGS SHOULD BE ABLE TO CLIMB INTO THE 70S...WITH PERHAPS A FEW LOW 80S WHERE MORE SUN OCCURS. TUE NIGHT THROUGH SAT...ECMWF/GFS/CANADIAN/UKMET AND LOCAL WRF-ARW RUNS ARE ALL IN PRETTY GOOD AGREEMENT REGARDING THE UPPER FLOW THROUGH THE PERIOD...WITH TROUGHING OVER THE WESTERN THIRD OF THE U.S. AND RIDGING TO ITS EAST. TOWARDS THU...THE WESTERN TROUGH APPEARS TO SPLIT INTO TWO. THE 00Z/06Z/12Z GFS ALL INDICATE THAT AFTER THE SPLIT...THE FLOW MAY TRY TO TAKE A MORE NW ORIENTATION OVER CANADA AND THE NORTHERN U.S...SUGGESTIVE OF COOLER AIR. HOWEVER...THE CANADIAN/UKMET/LOCAL WRF-ARW AND PAST ECMWF RUNS ALL INDICATE THAT THE FLOW WILL TURN MAINLY ZONAL ACROSS SOUTHERN CANADA...RESULTING IN MUCH WARMER CONDITIONS LIKE AN INDIAN SUMMER. PER HPC...HAVE CONSIDERED THE GFS RUNS OUTLIERS AND FOLLOWED THE 00Z ECMWF IDEA. AS FAR AS THE DETAILS GO...THE MAIN PIECE OF SHRTWV ENERGY LOCATED OVER MN AT 00Z WED WILL MOVE INTO WESTERN UPPER MICHIGAN AT 12Z WED AND THEN UP TO JAMES BAY AT 00Z THU. GIVEN THE TRACK OF THE SHRTWV...THE BEST FORCING FOR PCPN IS OVER THE WEST HALF OF THE U.P. THROUGH WED MORNING. THUS HIGHEST POPS ARE SITUATED THERE. AGAIN...SOME HEAVY RAINFALL COULD OCCUR OVER THE WESTERN U.P. GIVEN HIGH PRECIPITABLE WATER. A SURFACE COLD FRONT ASSOCIATED WITH THE SHRTWV WILL CROSS THE AREA ON WED...THUS MEANING TUE NIGHT SHOULD BE PRETTY WARM IN THE SW FLOW AHEAD OF IT. IN FACT...EVEN BEHIND THE FRONT...850MB TEMPS REMAIN AROUND 12C...SUGGESTING THE COOL DOWN WILL NOT BE TOO SIGNIFICANT ON WED. WILL NEED TO WATCH THE STRENGTH OF THE SURFACE LOW...WITH THE NEW 12Z ECMWF SHOWING A WRAPPED UP LOW DUE TO A NEGATIVELY TILTED SHRTWV COMING THROUGH. IF THIS COMES TO FRUITION...ALL THE WIND FORECASTS WILL NEED TO BE BUMPED UP CONSIDERABLY. HIGH PRESSURE BUILDS IN THE COLD FRONT ACROSS NORTHERN ONTARIO WED NIGHT AND THU...WITH A RIDGE EXTENDING SOUTHWARD INTO THE AREA...WHICH IS EXPECTED TO PROVIDE A DRY PERIOD DURING THIS TIME. 850MB TEMPS STILL NEAR 12C SUGGEST CONTINUED ABOVE NORMAL TEMPS...WITH ONLY COOLING EXPECTED NEAR THE GREAT LAKES SHORES WITH LAKE BREEZES. WARM AND MOIST ADVECTION THU NIGHT INTO FRI SUGGESTS THE NEED FOR SOME CHANCES FOR SHOWERS AND THUNDERSTORMS. BY 00Z SAT...THE ECMWF SHOWS 850MB DEWPOINTS CLIMBING TO 12-14C...AFTER BEING BETWEEN -10 TO -15C AT 00Z THU. THUS CONDITIONS PROBABLY WILL BECOME A BIT HUMID...SURPRISING AFTER THE RECENT COOL DOWN. 00Z ECMWF/CANADIAN/LOCAL WRF-ARW RUN ALL SUGGEST THE WARM FRONT MAY GET STUCK OVER OR JUST NORTH OF THE AREA FRI NIGHT AND SAT. FOR NOW...HAVE DECIDED TO CONFINE POPS TO THE NORTHERN U.P. AND LAKE SUPERIOR FOR FRI NIGHT...THEN HAVE A DRY SAT. SHOULD STILL BE FAIRLY MILD INTO SAT. NEW 12Z ECMWF ACTUALLY SHOWS THE FRONT HEADING BACK SOUTH ON SAT...BUT WILL WAIT UNTIL TOMORROW BEFORE CHANGING TO THIS IDEA. && .AVIATION (FOR THE 00Z TAF ISSUANCE)... VFR CONDITIONS WILL PREVAIL THROUGHOUT THE PERIOD WITH LLWS BECOMING AN ISSUE TONIGHT AND THEN DISSIPATING AFTER SUNRISE WITH WINDS MIXING DOWN AND BECOMING GUSTY IN THE MORNING. && .MARINE (FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)... SW WINDS WILL INCREASE TONIGHT AS PRES GRADIENT TIGHTENS BTWN HIGH PRES MOVING E TO THE OHIO VALLEY AND A LOW PRES TROUGH DROPPING S THRU NRN ONTARIO. WHILE SUSTAINED WINDS WILL PROBABLY BE IN THE 20-25KT RANGE...AREA OF PRES FALLS PASSING N AND THEN E OF THE LAKE MAY SUPPORT 30KT WINDS FOR A TIME...ESPECIALLY AROUND THE KEWEENAW AND POINTS N. WINDS SHOULD RELAX SOME SUN AFTN INTO EARLY MON. TUE/WED...THERE IS QUITE A BIT OF UNCERTAINTY ON TIMING AND STRENGTH OF A SFC LOW WHICH SHOULD TRACK FROM THE DAKOTAS TO JAMES BAY. A PERIOD OF S GALES IS NOT OUT OF THE QUESTION OVER ERN LAKE SUPERIOR MON NIGHT/TUE AHEAD OF SYSTEM. GREATER UNCERTAINTY EXISTS ON THE STRENGTH OF THE NW WINDS BEHIND SYSTEM. THIS FCST ISSUANCE REFLECTS A LIGHT NW WIND REGIME WITH EXPECTATION THAT SFC LOW WILL NOT BE WRAPPED UP (PER BULK OF FCST MODEL GUIDANCE) AS IT HEADS TO JAMES BAY. && .MQT WATCHES/WARNINGS/ADVISORIES...NONE. && $$ SHORT TERM...ROLFSON LONG TERM...AJ MARINE...ROLFSON AVIATION...MICHELS mi AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE MARQUETTE MI 133 PM EDT SAT SEP 15 2007 UPDATED FOR AVIATION DISCUSSION .DISCUSSION (503 AM EDT)... MAIN FCST ISSUES INCLUDE DIMINISHING LAKE EFFECT SHOWERS/CLOUDS TODAY...THEN OTHERWISE CLOUDS/TEMPS INTO MONDAY. WATER VAPOR LOOP AND 00Z RAOBS INDICATE THAT THE SHORTWAVE TROUGH HAS MOVED WELL EAST OF THE FCST AREA. BEHIND IT CONFLUENT FLOW HAS ALLOWED FOR SFC RIDGE TO BUILD IN FROM MN AND NW WI. INCREASINGLY ANTICYCLONIC FLOW AND LOWERING SUBSIDENCE INVERSION IN RESPONSE TO BUILDING HIGH PRESSURE ARE BREAKING APART LAKE CLOUDS OVER THE WRN HALF OF UPR MI AS NOTED ON IR SATELLITE IMAGERY IN THE PAST FEW HRS. ALSO LAKE EFFECT SHOWERS OVER THE ERN CWA APPEAR TO BE WEAKENING AND LESS ORGANIZED ON THE LATEST RADAR LOOP. RUC AND NAM FCST SNDGS ALSO SEEM TO BEAR THIS OUT. -3C 850 MB TEMPS AND ONSHORE FLOW WILL STILL WARRANT KEEPING SOME LOW CHC POPS IN FOR FAR ERN COUNTIES EARLY THIS MORNING BUT EXPECT THE REST OF THE CWA TO BE DRY AFT 12Z. FLOW BACKING WEST TO SOUTHWEST BY MIDDAY WILL SHUT OFF ANY REMAINING LAKE EFFECT SHOWERS. 850 MB TEMPS WARMING TO 0-2C BY MIDDAY WILL ALLOW HIGH TEMPS TO RISE INTO THE 55 TO 60F RANGE UNDER FULL SUNSHINE. THERE IS AN INCREASED RISK OF RIP CURRENTS TODAY FOR BEACHES EAST OF MARQUETTE WITH NW WIND 15 TO 25 KT BACKING W 10 TO 20 KT BY AFTERNOON. EXPECT WAVES 7 TO 10 FT SUBSIDING TO 3 TO 6 FT IN THE AFTERNOON. RIDGE AXIS SLIDES E OF THE FCST AREA BY LATE IN THE DAY AS SW GRADIENT FLOW INCREASES TONIGHT ON BACKSIDE OF HIGH. MIXING FROM INCREASING WIND WILL GENERALLY PREVENT FROST FORMATION TONIGHT... EXCEPT FOR COUNTIES ALONG THE WI BDR WHERE DECOUPLING OF WIND WILL ALLOW TEMPS TO LOWER INTO THE MID 30S WITH PATCHY FROST AT SOME SHELTERED LOCATIONS. WARMING TREND WILL CONTINUE AS 850 MB TEMPS RISE TO 6-7C ON SUNDAY AND 13 TO 15C ON MONDAY. WITH DIURNAL MIXING...LOOK FOR HIGH TEMPS MAINLY IN THE 60S ON SUNDAY WITH DOWNSLOPING LOCATIONS ALONG LAKE SUPERIOR REACHING INTO THE LOWER 70S. ON MONDAY...LOOK FOR TEMPS MAINLY IN THE MID TO UPR 70S WITH SOME LOWER 80S REACHED ALONG THE LAKE SUPERIOR SHORE. && .AVIATION (FOR THE 18Z TAF ISSUANCE)... AFTER QUICK DEVELOPMENT OF BKN STRATOCU (3500-4000FT CLOUD BASES) AFTER SUNRISE...LOW-LEVEL MOISTURE IS NOW MIXING OUT NICELY. DEVELOPING WAA PATTERN IS ALSO AIDING THE DISSIPATION OF THE CLOUDS FROM W TO E. EXPECT ANY LINGERING SCT STRATOCU TO DISSIPATE AT KCMX/KSAW IN THE NEXT HR OR TWO. AS FOR THE FCST...VFR CONDITIONS WILL PREVAIL FOR THE ENTIRE FCST PERIOD WITH LITTLE MORE THAN SOME CIRRUS AT TIMES. INCREASING SW WINDS ABOVE NOCTURNAL INVERSION TONIGHT ARE STILL EXPECTED TO REMAIN LIGHT ENOUGH TO PRECLUDE MENTION OF LLWS. && .MARINE (FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)... WINDS DIMINISHING AS HIGH PRES BUILDS TO THE MID MISSISSIPPI VALLEY AND PRES GRADIENT OVER LAKE SUPERIOR RELAXES. DIMINISHING TREND ONLY TEMPORARY AS SW FLOW INCREASES QUICKLY TO 20-25KT THIS AFTERNOON AND TONIGHT AS THE HIGH MOVES TO THE E AND A LOW PRES TROUGH DROPS SE INTO ONTARIO. PRES FALLS TO THE NORTH OF THE LAKE WITH THE TROUGH AND FAVORED CHANNELLING DIRECTION TO WINDS MAY SUPPORT 30 KT OVR WEST SECTIONS OF LK SUPERIOR. WINDS WILL THEN DIMINISH SUN NIGHT INTO MON. A LOW PRES SYSTEM TRACKING NE INTO ONTARIO TUE WILL BRING ANOTHER SYSTEM TO THE AREA. EXACT TRACK OF LOW NOT CERTAIN...BUT POTENTIAL EXISTS FOR S GALES LATE MON NIGHT INTO TUE AND AGAIN LATER TUE NIGHT INTO WED OVER EASTERN LK SUPERIOR. AT THE LEAST...30 KT SPEEDS SEEM FAIRLY CERTAIN. $$ && .MQT WATCHES/WARNINGS/ADVISORIES...NONE. && $$ DISCUSSION...VOSS AVIATION...ROLFSON MARINE...JLA mi AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE MARQUETTE MI 712 AM EDT SAT SEP 15 2007 UPDATED AVIATION DISCUSSION FOR 12Z TAFS .DISCUSSION (503 AM EDT)... MAIN FCST ISSUES INCLUDE DIMINISHING LAKE EFFECT SHOWERS/CLOUDS TODAY...THEN OTHERWISE CLOUDS/TEMPS INTO MONDAY. WATER VAPOR LOOP AND 00Z RAOBS INDICATE THAT THE SHORTWAVE TROUGH HAS MOVED WELL EAST OF THE FCST AREA. BEHIND IT CONFLUENT FLOW HAS ALLOWED FOR SFC RIDGE TO BUILD IN FROM MN AND NW WI. INCREASINGLY ANTICYCLONIC FLOW AND LOWERING SUBSIDENCE INVERSION IN RESPONSE TO BUILDING HIGH PRESSURE ARE BREAKING APART LAKE CLOUDS OVER THE WRN HALF OF UPR MI AS NOTED ON IR SATELLITE IMAGERY IN THE PAST FEW HRS. ALSO LAKE EFFECT SHOWERS OVER THE ERN CWA APPEAR TO BE WEAKENING AND LESS ORGANIZED ON THE LATEST RADAR LOOP. RUC AND NAM FCST SNDGS ALSO SEEM TO BEAR THIS OUT. -3C 850 MB TEMPS AND ONSHORE FLOW WILL STILL WARRANT KEEPING SOME LOW CHC POPS IN FOR FAR ERN COUNTIES EARLY THIS MORNING BUT EXPECT THE REST OF THE CWA TO BE DRY AFT 12Z. FLOW BACKING WEST TO SOUTHWEST BY MIDDAY WILL SHUT OFF ANY REMAINING LAKE EFFECT SHOWERS. 850 MB TEMPS WARMING TO 0-2C BY MIDDAY WILL ALLOW HIGH TEMPS TO RISE INTO THE 55 TO 60F RANGE UNDER FULL SUNSHINE. THERE IS AN INCREASED RISK OF RIP CURRENTS TODAY FOR BEACHES EAST OF MARQUETTE WITH NW WIND 15 TO 25 KT BACKING W 10 TO 20 KT BY AFTERNOON. EXPECT WAVES 7 TO 10 FT SUBSIDING TO 3 TO 6 FT IN THE AFTERNOON. RIDGE AXIS SLIDES E OF THE FCST AREA BY LATE IN THE DAY AS SW GRADIENT FLOW INCREASES TONIGHT ON BACKSIDE OF HIGH. MIXING FROM INCREASING WIND WILL GENERALLY PREVENT FROST FORMATION TONIGHT... EXCEPT FOR COUNTIES ALONG THE WI BDR WHERE DECOUPLING OF WIND WILL ALLOW TEMPS TO LOWER INTO THE MID 30S WITH PATCHY FROST AT SOME SHELTERED LOCATIONS. WARMING TREND WILL CONTINUE AS 850 MB TEMPS RISE TO 6-7C ON SUNDAY AND 13 TO 15C ON MONDAY. WITH DIURNAL MIXING...LOOK FOR HIGH TEMPS MAINLY IN THE 60S ON SUNDAY WITH DOWNSLOPING LOCATIONS ALONG LAKE SUPERIOR REACHING INTO THE LOWER 70S. ON MONDAY...LOOK FOR TEMPS MAINLY IN THE MID TO UPR 70S WITH SOME LOWER 80S REACHED ALONG THE LAKE SUPERIOR SHORE. && .AVIATION (FOR THE 12Z TAF ISSUANCE)... HIGH PRESSURE BUILDING IN TO THE REGION HAS SCOURED OUT THE LK EFFECT CLOUDS AT KCMX AND KSAW. EXPECT VFR CONDITIONS THROUGH NEXT 24 HR AS THE HIGH REMAINS IN CONTROL. INCREASING WINDS AT 1000-2000FT AGL LATE TODAY INTO TONIGHT COULD RESULT IN LLWS AT BOTH SITES. EXPECTED STRENGTH OF WIND CORE ABOVE THE INVERSION TONIGHT IS LOW ENOUGH TO PRECLUDE THE MENTION RIGHT NOW IN THE TAFS. && .MARINE (FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)... WINDS DIMINISHING AS HIGH PRES BUILDS TO THE MID MISSISSIPPI VALLEY AND PRES GRADIENT OVER LAKE SUPERIOR RELAXES. DIMINISHING TREND ONLY TEMPORARY AS SW FLOW INCREASES QUICKLY TO 20-25KT THIS AFTERNOON AND TONIGHT AS THE HIGH MOVES TO THE E AND A LOW PRES TROUGH DROPS SE INTO ONTARIO. PRES FALLS TO THE NORTH OF THE LAKE WITH THE TROUGH AND FAVORED CHANNELLING DIRECTION TO WINDS MAY SUPPORT 30 KT OVR WEST SECTIONS OF LK SUPERIOR. WINDS WILL THEN DIMINISH SUN NIGHT INTO MON. A LOW PRES SYSTEM TRACKING NE INTO ONTARIO TUE WILL BRING ANOTHER SYSTEM TO THE AREA. EXACT TRACK OF LOW NOT CERTAIN...BUT POTENTIAL EXISTS FOR S GALES LATE MON NIGHT INTO TUE AND AGAIN LATER TUE NIGHT INTO WED OVER EASTERN LK SUPERIOR. AT THE LEAST...30 KT SPEEDS SEEM FAIRLY CERTAIN. $$ && .MQT WATCHES/WARNINGS/ADVISORIES... FREEZE WARNING UNTIL 12Z TODAY MIZ002-004-009>011-084. FROST ADVISORY UNTIL 12Z TODAY MI003-005-012-013. && $$ DISCUSSION...VOSS MARINE/AVIATION...JLA mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MARQUETTE MI 503 AM EDT SAT SEP 15 2007 .DISCUSSION... MAIN FCST ISSUES INCLUDE DIMINISHING LAKE EFFECT SHOWERS/CLOUDS TODAY...THEN OTHERWISE CLOUDS/TEMPS INTO MONDAY. WATER VAPOR LOOP AND 00Z RAOBS INDICATE THAT THE SHORTWAVE TROUGH HAS MOVED WELL EAST OF THE FCST AREA. BEHIND IT CONFLUENT FLOW HAS ALLOWED FOR SFC RIDGE TO BUILD IN FROM MN AND NW WI. INCREASINGLY ANTICYCLONIC FLOW AND LOWERING SUBSIDENCE INVERSION IN RESPONSE TO BUILDING HIGH PRESSURE ARE BREAKING APART LAKE CLOUDS OVER THE WRN HALF OF UPR MI AS NOTED ON IR SATELLITE IMAGERY IN THE PAST FEW HRS. ALSO LAKE EFFECT SHOWERS OVER THE ERN CWA APPEAR TO BE WEAKENING AND LESS ORGANIZED ON THE LATEST RADAR LOOP. RUC AND NAM FCST SNDGS ALSO SEEM TO BEAR THIS OUT. -3C 850 MB TEMPS AND ONSHORE FLOW WILL STILL WARRANT KEEPING SOME LOW CHC POPS IN FOR FAR ERN COUNTIES EARLY THIS MORNING BUT EXPECT THE REST OF THE CWA TO BE DRY AFT 12Z. FLOW BACKING WEST TO SOUTHWEST BY MIDDAY WILL SHUT OFF ANY REMAINING LAKE EFFECT SHOWERS. 850 MB TEMPS WARMING TO 0-2C BY MIDDAY WILL ALLOW HIGH TEMPS TO RISE INTO THE 55 TO 60F RANGE UNDER FULL SUNSHINE. THERE IS AN INCREASED RISK OF RIP CURRENTS TODAY FOR BEACHES EAST OF MARQUETTE WITH NW WIND 15 TO 25 KT BACKING W 10 TO 20 KT BY AFTERNOON. EXPECT WAVES 7 TO 10 FT SUBSIDING TO 3 TO 6 FT IN THE AFTERNOON. RIDGE AXIS SLIDES E OF THE FCST AREA BY LATE IN THE DAY AS SW GRADIENT FLOW INCREASES TONIGHT ON BACKSIDE OF HIGH. MIXING FROM INCREASING WIND WILL GENERALLY PREVENT FROST FORMATION TONIGHT... EXCEPT FOR COUNTIES ALONG THE WI BDR WHERE DECOUPLING OF WIND WILL ALLOW TEMPS TO LOWER INTO THE MID 30S WITH PATCHY FROST AT SOME SHELTERED LOCATIONS. WARMING TREND WILL CONTINUE AS 850 MB TEMPS RISE TO 6-7C ON SUNDAY AND 13 TO 15C ON MONDAY. WITH DIURNAL MIXING...LOOK FOR HIGH TEMPS MAINLY IN THE 60S ON SUNDAY WITH DOWNSLOPING LOCATIONS ALONG LAKE SUPERIOR REACHING INTO THE LOWER 70S. ON MONDAY...LOOK FOR TEMPS MAINLY IN THE MID TO UPR 70S WITH SOME LOWER 80S REACHED ALONG THE LAKE SUPERIOR SHORE. && .AVIATION (FOR THE 06Z TAF ISSUANCE)... CHILLY AIRMASS WILL YIELD SOME LAKE EFFECT -SHRA INTO THE EARLY MORNING HOURS...ESPECIALLY AT KCMX. GIVEN THE OVER WATER INSTABILITY AND NW TO WNW LOW-LEVEL FLOW TONIGHT...EXPECT LAKE EFFECT CLOUDS TO LINGER A BIT THIS MORNING...AGAIN ESPECIALLY AT KCMX MORE SO THAN KSAW. VFR CONDITIONS SHOULD PREVAIL VERY LATE TONIGHT THRU SATURDAY MORNING AT BOTH SITES HAS HIGH PRES RIDGE ARRIVES WITH DRIER AIR/MODERATING AIRMASS AND BACKING WINDS. && .MARINE (FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)... WINDS DIMINISHING AS HIGH PRES BUILDS TO THE MID MISSISSIPPI VALLEY AND PRES GRADIENT OVER LAKE SUPERIOR RELAXES. DIMINISHING TREND ONLY TEMPORARY AS SW FLOW INCREASES QUICKLY TO 20-25KT THIS AFTERNOON AND TONIGHT AS THE HIGH MOVES TO THE E AND A LOW PRES TROUGH DROPS SE INTO ONTARIO. PRES FALLS TO THE NORTH OF THE LAKE WITH THE TROUGH AND FAVORED CHANNELLING DIRECTION TO WINDS MAY SUPPORT 30 KT OVR WEST SECTIONS OF LK SUPERIOR. WINDS WILL THEN DIMINISH SUN NIGHT INTO MON. A LOW PRES SYSTEM TRACKING NE INTO ONTARIO TUE WILL BRING ANOTHER SYSTEM TO THE AREA. EXACT TRACK OF LOW NOT CERTAIN...BUT POTENTIAL EXISTS FOR S GALES LATE MON NIGHT INTO TUE AND AGAIN LATER TUE NIGHT INTO WED OVER EASTERN LK SUPERIOR. AT THE LEAST...30 KT SPEEDS SEEM FAIRLY CERTAIN. $$ && .MQT WATCHES/WARNINGS/ADVISORIES... FREEZE WARNING UNTIL 12Z TODAY MIZ002-004-009>011-084. FROST ADVISORY UNTIL 12Z TODAY MI003-005-012-013. && $$ DISCUSSION...VOSS MARINE...JLA AVIATION...DLG mi AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE MARQUETTE MI 142 AM EDT SAT SEP 15 2007 UPDATED AVIATION DISCUSSION FOR 06Z TAFS .SHORT TERM (TONIGHT AND SAT)... MAIN CONCERN WITH THIS FORECAST UPDATE ARE THE LAKE EFFECT CLOUD AND PRECIPITATION TRENDS AND TEMPERATURES OVERNIGHT. WATER VAPOR IMAGERY AND RUC SHOWING A RATHER PRONOUNCE TROUGH JUST EAST OF THE FORECAST AREA. THE EMBEDDED SHORTWAVE ENERGY IS MOVING INTO EASTERN ONTARIO AS A WEAKER ONE IS MOVING INTO WESTERN ONTARIO. A BROAD RIDGE WILL MOVE INTO WESTERN CANADA. SURFACE ANALYSIS DEPICTS A BROAD HIGH OVER THE NORTHERN PLAINS PUSHING A COLD FRONT THROUGH THE EASTERN OHIO RIVER VALLEY. DRY AIR ACCOMPANYING THIS HIGH IS BLANKETING SOUTH CENTRAL CANADA AND THE UPPER MISSISSIPPI RIVER VALLEY. SURFACE DEW POINTS ARE AROUND 32F OVER SOUTH CENTRAL CANADA. DRIER AIR ADVECTING IN WILL CAUSE THE SKIES TO GRADUALLY CLEAR. COLD AIR IS ADVECTING INTO THE AREA PRODUCING A FEW LAKE EFFECT SHOWERS OVER THE NORTHERN KEWEENAW PENINSULA AND NORTH CENTRAL U.P. SATELLITE SHOWING SOME THINNING OF THE CLOUD COVER OVER THE WESTERN U.P. THE WINDS ARE DIMINISHING AS WELL. TAMDAR SOUNDINGS FROM KSAW SHOWED 850MB TEMPS AROUND -3C...SO THERE IS PLENTY OF OVER WATER INSTABILITY FOR LAKE EFFECT PRECIPITATION. LONG FETCH STILL COINCIDING WITH DEEP MOISTURE IS SUPPORTING HEAVIER AND MORE WIDESPREAD PRECIPITATION OVER SOUTH CENTRAL LAKE SUPERIOR INTO NORTH CENTRAL UPPER MICHIGAN. IT`S LIKELY SNOWFLAKES WERE FLYING FOR A TIME IN SOME OF THE OTHER FAVORED HIGHER TERRAIN LOCATIONS OF THE WEST AS WELL. LINGERING SHRA OVER THE WESTERN PART OF FORECAST AREA SHOULD WIND DOWN QUICKLY IN THE NEXT FEW HOURS AS DRIER AIRMASS/WELL MIXED BOUNDARY NOTED BY KINL SOUNDING ARRIVES. OVER THE EAST...LINGERED -SHRA WILL CONTINUE THRU THE NIGHT. AT THIS POINT...IT APPEARS THERE WILL STILL BE ENOUGH CLEARING THAT GOING FROST/FREEZE HEADLINES WILL WORK OUT. HIGH PRESSURE SHOULD BE CLOSE ENOUGH LATE TONIGHT TO ALLOW DECOUPLED SURFACE WINDS FOR DECENT RADIATIONAL COOLING AND SUBFREEZING TEMPERATURES IN THE INTERIOR WEST HALF. AS THE HIGH SPREAD OVER THE FORECAST AREA ON SATURDAY...SHOWERS OVER THE NORTHEAST CWA SHOULD END BY EARLY AFTERNOON AS WINDS BACK AND WARM AIR ADVECTION BEGINS. THERE SHOULD BE PLENTY OF SUNSHINE FOR MUCH OF THE FORECAST AREA. MOS GUIDANCE LOOKED ACCEPTABLE WITH HIGHS IN THE MID 50S TO AROUND 60. .LONG TERM...00Z SUN ONWARD... NOT TOO MUCH OF CONCERN FOR THIS FORECAST AS THINGS ARE QUIET UNTIL MONDAY NIGHT AS A WARM FRONT APPROACHES. A COLD FRONT TRIES TO COME DOWN TOWARDS THE AREA ON SUN AND NAM IS THE ONLY MODEL TO PUSH THIS THROUGH. WENT AGAINST THE NAM AS THE COLD AIR APPEARS TO STAY TO THE NORTH OF THE AREA AND UPPER LEVEL RIDGING BUILDING INTO THE AREA SHOULD KEEP THE FRONT TO THE NORTH AS GFS HAS BEEN ADVERTISING ALL ALONG. NAM IS THE OUTLIER AND WILL GO WITH GFS FOR THIS FORECAST. TEMPERATURES WILL BE WARMING AND WENT CLOSE TO ADJMVR FOR LOWS AND HIGHS WHICH THEY SEEMED REASONABLE. UPPER LEVEL TROUGHING STARTS TO PUSH OUT AND RIDGING BUILDS IN. IN THE EXTENDED...GFS...ECMWF AND CANADIAN ALL HAVE A 500 MB TROUGH ACROSS THE WESTERN HALF OF THE U.S. AND A RIDGE ACROSS THE EASTERN U.S. 00Z TUE. TROUGHING MOVES INTO THE AREA 00Z WED. THIS TROUGH MOVES QUICKLY THROUGH AND THEN RIDGING TRIES TO COME BACK IN FOR 00Z THU AND FOR 00Z FRI AND 00Z SAT. FOLLOWED AGAIN CLOSE TO 00Z ECMWF SOLUTION AND LOOKS VERY WARM IN THE EXTENDED WITH ABOVE NORMAL TEMPERATURES. WARM FRONT PASSES THROUGH ON MON NIGHT AND INTRODUCED CHANCE POPS WITH THIS AS IT HEADS NORTH. FOR TUE...WARM FRONT IS TO THE NORTH AND COLD FRONT TO THE WEST AND LOOKS VERY WARM. ECMWF HAS 850 MB TEMPERATURES OF 16C TO 18C OVER THE AREA AND MIXING THIS DOWN GIVES ME HIGHS IN THE MID TO UPPER 80S WHICH WOULD GIVE ME RECORD HIGHS. WILL NOT GO THAT WARM FOR NOW...BUT WOULD NOT BE SURPRISED IF MID 80S ARE NOT POSSIBLE AND A FEW RECORD HIGHS WOULD FALL ON THAT DAY. WENT LOWER 80S FOR NOW CLOSE TO ADJMEX GUIDANCE. LOOKS ACTIVE IN THE EXTENDED WITH COLD FRONT COMING ACROSS TUE NIGHT AND PASSING OUT OF THE AREA ON WED AND KEPT CHANCE POPS IN FOR TUE NIGHT OVER ALL THE CWA AND ON WED FOR SOUTHERN AND ERN CWA. WED NIGHT AND THU...FRONT HEADS TO THE SOUTH AND HEADS BACK NORTH ON THU NIGHT AS A WARM FRONT AND AGAIN PUT CHANCE POPS IN FOR THU NIGHT. FRI AGAIN LOOKS TO BE IN THE WARM SECTOR FOR THE CWA WITH WARM FRONT TO THE NORTH AND COLD FRONT OFF TO THE WEST. WENT CLOSE TO ADJMXR FOR LOWS AND HIGHS AND COULD HAVE SOME RECORD HIGHS BROKEN IN THE EXTENDED. LOOKS MORE ACTIVE WITH FRONT MEANDERING ACROSS THE AREA. && .AVIATION (FOR THE 06Z TAF ISSUANCE)... CHILLY AIRMASS WILL YIELD SOME LAKE EFFECT -SHRA INTO THE EARLY MORNING HOURS...ESPECIALLY AT KCMX. GIVEN THE OVER WATER INSTABILITY AND NW TO WNW LOW-LEVEL FLOW TONIGHT...EXPECT LAKE EFFECT CLOUDS TO LINGER A BIT THIS MORNING...AGAIN ESPECIALLY AT KCMX MORE SO THAN KSAW. VFR CONDITIONS SHOULD PREVAIL VERY LATE TONIGHT THRU SATURDAY MORNING AT BOTH SITES HAS HIGH PRES RIDGE ARRIVES WITH DRIER AIR/MODERATING AIRMASS AND BACKING WINDS. && .MARINE (FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)... GALE WARNINGS HAVE BEEN DROPPED WITH THIS FCST ISSUANCE. 3HR PRES RISE MAX THAT WAS LOCATED NW OF LAKE SUPERIOR EARLIER TODAY AND WHICH HELPED BOOST WIND GUSTS TO AROUND 35KT HAS NOW SETTLED OVER SE LAKE SUPERIOR. WITH THE LOSS OF THE ADDITIVE ISALLOBARIC COMPONENT TO THE WIND...FREQUENT GALE FORCE GUSTS HAVE LIKELY ENDED. WINDS WILL SLOWLY DIMINISH THRU THE NIGHT INTO EARLY SAT MORNING AS HIGH PRES BUILDS TO THE MID MISSISSIPPI VALLEY. THE LIGHTER WINDS WILL BE SHORT LIVED AS SW FLOW WILL INCREASE QUICKLY TO 20-25KT SAT/SAT NIGHT AS THE HIGH MOVES TO THE E AND A LOW PRES TROUGH DROPS SE INTO ONTARIO. WINDS WILL THEN DIMINISH SUN NIGHT INTO MON. A LOW PRES SYSTEM TRACKING NE INTO ONTARIO TUE WILL BRING ANOTHER SYSTEM TO THE AREA. && .MQT WATCHES/WARNINGS/ADVISORIES... FREEZE WARNING 06Z-12Z SAT MIZ002-004-009>011-084. FROST ADVISORY 06Z-12Z SAT MI003-005-012-013. && $$ SHORT TERM...DLG LONG TERM...GM MARINE...DR AVIATION...DLG mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MARQUETTE MI 1108 PM EDT FRI SEP 14 2007 .SHORT TERM (TONIGHT AND SAT)... MAIN CONCERN WITH THIS FORECAST UPDATE ARE THE LAKE EFFECT CLOUD AND PRECIPITATION TRENDS AND TEMPERATURES OVERNIGHT. WATER VAPOR IMAGERY AND RUC SHOWING A RATHER PRONOUNCE TROUGH JUST EAST OF THE FORECAST AREA. THE EMBEDDED SHORTWAVE ENERGY IS MOVING INTO EASTERN ONTARIO AS A WEAKER ONE IS MOVING INTO WESTERN ONTARIO. A BROAD RIDGE WILL MOVE INTO WESTERN CANADA. SURFACE ANALYSIS DEPICTS A BROAD HIGH OVER THE NORTHERN PLAINS PUSHING A COLD FRONT THROUGH THE EASTERN OHIO RIVER VALLEY. DRY AIR ACCOMPANYING THIS HIGH IS BLANKETING SOUTH CENTRAL CANADA AND THE UPPER MISSISSIPPI RIVER VALLEY. SURFACE DEW POINTS ARE AROUND 32F OVER SOUTH CENTRAL CANADA. DRIER AIR ADVECTING IN WILL CAUSE THE SKIES TO GRADUALLY CLEAR. COLD AIR IS ADVECTING INTO THE AREA PRODUCING A FEW LAKE EFFECT SHOWERS OVER THE NORTHERN KEWEENAW PENINSULA AND NORTH CENTRAL U.P. SATELLITE SHOWING SOME THINNING OF THE CLOUD COVER OVER THE WESTERN U.P. THE WINDS ARE DIMINISHING AS WELL. TAMDAR SOUNDINGS FROM KSAW SHOWED 850MB TEMPS AROUND -3C...SO THERE IS PLENTY OF OVER WATER INSTABILITY FOR LAKE EFFECT PRECIPITATION. LONG FETCH STILL COINCIDING WITH DEEP MOISTURE IS SUPPORTING HEAVIER AND MORE WIDESPREAD PRECIPITATION OVER SOUTH CENTRAL LAKE SUPERIOR INTO NORTH CENTRAL UPPER MICHIGAN. IT`S LIKELY SNOWFLAKES WERE FLYING FOR A TIME IN SOME OF THE OTHER FAVORED HIGHER TERRAIN LOCATIONS OF THE WEST AS WELL. LINGERING SHRA OVER THE WESTERN PART OF FORECAST AREA SHOULD WIND DOWN QUICKLY IN THE NEXT FEW HOURS AS DRIER AIRMASS/WELL MIXED BOUNDARY NOTED BY KINL SOUNDING ARRIVES. OVER THE EAST...LINGERED -SHRA WILL CONTINUE THRU THE NIGHT. AT THIS POINT...IT APPEARS THERE WILL STILL BE ENOUGH CLEARING THAT GOING FROST/FREEZE HEADLINES WILL WORK OUT. HIGH PRESSURE SHOULD BE CLOSE ENOUGH LATE TONIGHT TO ALLOW DECOUPLED SURFACE WINDS FOR DECENT RADIATIONAL COOLING AND SUBFREEZING TEMPERATURES IN THE INTERIOR WEST HALF. AS THE HIGH SPREAD OVER THE FORECAST AREA ON SATURDAY...SHOWERS OVER THE NORTHEAST CWA SHOULD END BY EARLY AFTERNOON AS WINDS BACK AND WARM AIR ADVECTION BEGINS. THERE SHOULD BE PLENTY OF SUNSHINE FOR MUCH OF THE FORECAST AREA. MOS GUIDANCE LOOKED ACCEPTABLE WITH HIGHS IN THE MID 50S TO AROUND 60. .LONG TERM...00Z SUN ONWARD... NOT TOO MUCH OF CONCERN FOR THIS FORECAST AS THINGS ARE QUIET UNTIL MONDAY NIGHT AS A WARM FRONT APPROACHES. A COLD FRONT TRIES TO COME DOWN TOWARDS THE AREA ON SUN AND NAM IS THE ONLY MODEL TO PUSH THIS THROUGH. WENT AGAINST THE NAM AS THE COLD AIR APPEARS TO STAY TO THE NORTH OF THE AREA AND UPPER LEVEL RIDGING BUILDING INTO THE AREA SHOULD KEEP THE FRONT TO THE NORTH AS GFS HAS BEEN ADVERTISING ALL ALONG. NAM IS THE OUTLIER AND WILL GO WITH GFS FOR THIS FORECAST. TEMPERATURES WILL BE WARMING AND WENT CLOSE TO ADJMVR FOR LOWS AND HIGHS WHICH THEY SEEMED REASONABLE. UPPER LEVEL TROUGHING STARTS TO PUSH OUT AND RIDGING BUILDS IN. IN THE EXTENDED...GFS...ECMWF AND CANADIAN ALL HAVE A 500 MB TROUGH ACROSS THE WESTERN HALF OF THE U.S. AND A RIDGE ACROSS THE EASTERN U.S. 00Z TUE. TROUGHING MOVES INTO THE AREA 00Z WED. THIS TROUGH MOVES QUICKLY THROUGH AND THEN RIDGING TRIES TO COME BACK IN FOR 00Z THU AND FOR 00Z FRI AND 00Z SAT. FOLLOWED AGAIN CLOSE TO 00Z ECMWF SOLUTION AND LOOKS VERY WARM IN THE EXTENDED WITH ABOVE NORMAL TEMPERATURES. WARM FRONT PASSES THROUGH ON MON NIGHT AND INTRODUCED CHANCE POPS WITH THIS AS IT HEADS NORTH. FOR TUE...WARM FRONT IS TO THE NORTH AND COLD FRONT TO THE WEST AND LOOKS VERY WARM. ECMWF HAS 850 MB TEMPERATURES OF 16C TO 18C OVER THE AREA AND MIXING THIS DOWN GIVES ME HIGHS IN THE MID TO UPPER 80S WHICH WOULD GIVE ME RECORD HIGHS. WILL NOT GO THAT WARM FOR NOW...BUT WOULD NOT BE SURPRISED IF MID 80S ARE NOT POSSIBLE AND A FEW RECORD HIGHS WOULD FALL ON THAT DAY. WENT LOWER 80S FOR NOW CLOSE TO ADJMEX GUIDANCE. LOOKS ACTIVE IN THE EXTENDED WITH COLD FRONT COMING ACROSS TUE NIGHT AND PASSING OUT OF THE AREA ON WED AND KEPT CHANCE POPS IN FOR TUE NIGHT OVER ALL THE CWA AND ON WED FOR SOUTHERN AND ERN CWA. WED NIGHT AND THU...FRONT HEADS TO THE SOUTH AND HEADS BACK NORTH ON THU NIGHT AS A WARM FRONT AND AGAIN PUT CHANCE POPS IN FOR THU NIGHT. FRI AGAIN LOOKS TO BE IN THE WARM SECTOR FOR THE CWA WITH WARM FRONT TO THE NORTH AND COLD FRONT OFF TO THE WEST. WENT CLOSE TO ADJMXR FOR LOWS AND HIGHS AND COULD HAVE SOME RECORD HIGHS BROKEN IN THE EXTENDED. LOOKS MORE ACTIVE WITH FRONT MEANDERING ACROSS THE AREA. && .AVIATION (FOR THE 00Z TAF ISSUANCE)... CHILLY AIRMASS WILL YIELD SOME LAKE EFFECT -SHRA INTO THE EARLY EVENING HRS...ESPECIALLY AT KCMX. GIVEN THE OVER WATER INSTABILITY AND NW TO WNW LOW-LEVEL FLOW TONIGHT...EXPECT LAKE EFFECT CLOUDS TO LINGER A BIT LONGER THAN PREVIOUS FCST INDICATED...AGAIN ESPECIALLY AT KCMX MORE SO THAN KSAW. VFR CONDITIONS SHOULD PREVAIL VERY LATE TONIGHT THRU SAT MORNING AT BOTH SITES HAS HIGH PRES RIDGE ARRIVES WITH DRIER AIR/MODERATING AIRMASS AND BACKING WINDS. && .MARINE (FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)... GALE WARNINGS HAVE BEEN DROPPED WITH THIS FCST ISSUANCE. 3HR PRES RISE MAX THAT WAS LOCATED NW OF LAKE SUPERIOR EARLIER TODAY AND WHICH HELPED BOOST WIND GUSTS TO AROUND 35KT HAS NOW SETTLED OVER SE LAKE SUPERIOR. WITH THE LOSS OF THE ADDITIVE ISALLOBARIC COMPONENT TO THE WIND...FREQUENT GALE FORCE GUSTS HAVE LIKELY ENDED. WINDS WILL SLOWLY DIMINISH THRU THE NIGHT INTO EARLY SAT MORNING AS HIGH PRES BUILDS TO THE MID MISSISSIPPI VALLEY. THE LIGHTER WINDS WILL BE SHORT LIVED AS SW FLOW WILL INCREASE QUICKLY TO 20-25KT SAT/SAT NIGHT AS THE HIGH MOVES TO THE E AND A LOW PRES TROUGH DROPS SE INTO ONTARIO. WINDS WILL THEN DIMINISH SUN NIGHT INTO MON. A LOW PRES SYSTEM TRACKING NE INTO ONTARIO TUE WILL BRING ANOTHER SYSTEM TO THE AREA. && .MQT WATCHES/WARNINGS/ADVISORIES... FREEZE WARNING 06Z-12Z SAT MIZ002-004-009>011-084. FROST ADVISORY 06Z-12Z SAT MI003-005-012-013. && $$ SHORT TERM...DLG LONG TERM...GM MARINE...DR AVIATION...DLG mi AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE MARQUETTE MI 130 PM EDT FRI SEP 14 2007 UPDATED FOR AVIATION DISCUSSION .UPDATE (ISSUED AT 1112 AM EDT)... SHORTWAVE TROF IS NOW MOVING ACROSS WRN LAKE SUPERIOR/WRN UPPER MI WITH ABUNDANT LOW LEVEL MOISTURE ROTATING INTO THE FCST AREA. 12Z KINL SOUNDING SHOWED NEAR SATURATION TO AROUND 750MB WHILE CWPL SOUNDING SHOWED SATURATION TO 750MB. 850MB TEMPS AT BOTH SITES WERE -6C. DEEP MOISTURE/CYCLONIC FLOW AND INCREASING OVERWATER INSTABILITY ARE LEADING TO A GRADUAL INCREASE IN LAKE EFFECT PCPN THIS MORNING. WHILE THERE HAVE NOT BEEN ANY REPORTS OF SNOW FROM SPOTTERS...SNOW HAS BEEN OCCURRING THIS MORNING ACROSS THE LAKE AT GRAND MARAIS MN. GOING FCST FOR THE AFTN IS IN GOOD SHAPE WITH HIGHEST POPS FOR THE AREAS FAVORED FOR LAKE EFFECT PCPN UNDER NW FLOW. A FEW SNOWFLAKES COULD STILL MIX IN WITH THE -SHRA OVER THE HIGHEST TERRAIN OF THE W AND NW. OTHERWISE...TEMPS OVER THE W AND NCNTRL SHOULD RISE VERY LITTLE FROM CURRENT READINGS UNDER CLOUD COVER AND FREQUENT -SHRA. TEMPS HAVE ALREADY REBOUNDED SOME OVER THE E AND SCNTRL WHERE THERE HAS BEEN MORE SUN THIS MORNING. HOWEVER...DON`T EXPECT TEMPS TO RISE ANY HIGHER THAN ABOUT THE MID 50S THERE. && .PREV DISCUSSION (ISSUED AT 521 AM EDT)... MAIN FCST ISSUES INCLUDE SHOWER COVERAGE TODAY AND POSSIBILITY OF SNOW MIXING IN WITH RAIN OVER HIGHER TERRAIN AREAS...AND THEN FREEZE/FROST HEADLINES TONIGHT. WATER VAPOR IMAGERY AND RUC ANALYSIS SHOW A VIGOROUS SHORTWAVE/CLOSED MIDLEVEL LOW MOVING THRU NRN ONTARIO. AT THE SFC...ASSOCIATED LOW PRES WAS LOCATED JUST W OF JAMES BAY WITH A COLD FRONT EXTENDING S ACROSS NRN LAKE MI INTO NRN IL. SHRA ASSOC WITH THIS COLD FRONT HAVE EXITED THE ERN FA FOR THE MOST PART EARLY THIS MORNING AS A DRY SLOT HAS MOVED IN FROM THE WEST. FOCUS FOR TODAY SHIFTS TO SHORTWAVE LOBE AND ASSOC TROUGH/SECONDARY COLD FRONT MOVING DOWN FROM NW ONTARIO. DEEP/MOIST NW CYCLONIC FLOW ALONG THIS SHORTWAVE/TROUGH HAS YIELDED SHOWERS OVER NW ONTARIO AND NRN MN. THICKNESSES AND FREEZING LVLS ARE LOW ENOUGH FOR SOME SNOW SHOWERS TO BE REPORTED THIS MORNING NORTH OF MN BDR INTO ONTARIO. WITH 850 MB TEMPS OF -4 TO -5C POISED TO MOVE ACROSS LAKE SUPERIOR WITH THIS TROUGH/FRONTAL PASSAGE...LAKE-850MB DELTA-T WILL INCREASE TO 15-17C. WITH DEEP INSTABILITY (LAKE INDUCED CAPES IN EXCESS OF 300 J/KG) AND MOIST SNDGS PROFILE TO NEAR 600 MB LOOK FOR LAKE EFFECT RAIN SHOWERS TO DEVELOP ALONG THE NRN TIER COUNTIES. BEST CHCS OF RAIN WILL BE FOR AREAS FAVORED BY 300-320 DIR CBL FLOW SO WILL KEEP LIKELY POPS OR NUMEROUS COVERAGE IN FOR THESE COUNTIES WHILE THE REST OF THE NRN TIER SHOULD SEE SCT SHRA. LOOKING AT 950 TEMPS...SOUNDING PROFILES AND 925-850 MB THICKNESSES...THE POSSIBILITY OF SNOW MIXING IN OVER THE W AND NCNTRL HIGH TERRAIN LOOKS DOUBTFUL...BUT SINCE OBS JUST OVER THE BORDER INTO ONTARIO ARE REPORTING SNOW WILL KEEP A MENTION IN FOR WRN COUNTIES THIS MORNING. THICKNESSES AND TEMPS SHOULD WARM ENOUGH BY AFTERNOON TO KEEP ANY PCPN LIQUID. CLOUDS AND EXPECTED PERSISTENT SHRA SHOULD KEEP TEMPS QUITE COOL FOR MID SEPT. FAVORED THE LOW END OF MOS GUIDANCE WITH LOW TO MID 40S FCST FOR A GOOD PORTION OF THE WRN INTERIOR OF THE CWFA. TEMPS SHOULD BE SOMEWHAT WARMER TO THE E WITH LONGER FETCH OVER LAKE SUPERIOR. HIGHEST TEMPS WILL BE OVER THE SCNTRL AREAS (MID 50S) WITH DOWNSLOPING NW FLOW AND LITTLE OR NO PCPN. RIP CURRENTS ARE ALSO POSSIBLE EAST OF MARQUETTE WITH NORTHWEST WINDS UP TO 30 KT AND HIGH WAVES UP TO 8 TO 11 FT. NEXT BIG PROBLEM WILL BE FROST/FREEZE HEADLINES FOR TONIGHT. SHORTWAVE RIDGING AND ASSOC SFC RDG IS FCST TO BUILD OVER THE WRN INTERIOR OF THE CWFA LATE TONIGHT. AS SKIES CLEAR OUT AND WINDS DECOUPLE BY LATE TONIGHT...GOOD RADIATIONAL COOLING WILL ALLOW TEMPS TO DIP DOWN TO THE UPPER 20S OVER IRON-DICKINSON-GOGEBIC-SOUTHERN HOUGHTON AND INLAND PORTIONS OF ONTONAGON AND BARAGA COUNTIES SO HAVE ISSUED A FREEZE WARNING FOR THESE COUNTIES. MORE PERSISTENT WIND AND CLOUDS WILL KEEP TEMPS UP LONGER FOR NORTHERN HOUGHTON...MARQUETTE...DELTA AND MENOMINEE SO WILL GO WITH A FROST ADVISORY FOR THESE COUNTIES AS TEMPS WILL LIKELY DIP NEAR 30F FOR INLAND PORTIONS. SCATTERED LAKE EFFECT SHRA SHOULD CONTINUE ACROSS THE EASTERN CWA TONIGHT AS WEAKLY CYCLONIC NW FLOW PERSISTS WITH LAKE DELTA-T AROUND 14-15C. SO GIVEN PERSISTENT CLOUDS AND MODERATING NW WINDS OFF LAKE SUPERIOR DO NOT EXPECT A FROST/FREEZE POTENTIAL FOR THE EAST. KEPT IN LOW CHC POPS FOR SHRA EARLY SAT FOR FAR ERN COUNTIES GIVEN ONSHORE NW FLOW BUT FLOW IS ALREADY BECOMING ANTICYCLONIC AS RIDGE AXIS BUILDS IN QUICKLY FROM THE WEST. BACKING FLOW TO WEST BY MIDDAY SHOULD END ANY LAKE EFFECT SHRA. RETURN WSW FLOW ON BACKSIDE OF RIDGE WILL ALLOW FOR A GRADUAL WARMING TREND OVER THE WEEKEND AS 850 MB TEMPS REBOUND TO AROUND 8C BY SUN. LOOK FOR HIGH IN THE UPR 50S TO AROUND 60F ON SAT AND 65 TO 70 RANGE ON SUN UNDER MOSTLY SUNNY SKIES. && .AVIATION (FOR THE 18Z TAF ISSUANCE)... MVFR CIGS WILL CONTINUE TO DOMINATE KCMX THRU THE AFTN AS ABUNDANT LOW-LEVEL MOISTURE LINGERS. HOWEVER...SOME DRYING/LOWERING OF SFC DWPTS IS EVIDENT ACROSS LAKE SUPERIOR...SUGGESTING MVFR CIGS BLO 2KFT WILL END AT KCMX...PROBABLY BY 21Z. AT KSAW...FLOW HAS HAD ENOUGH OF A DOWNSLOPE COMPONENT SO FAR THAT MVFR CIGS AND EVEN -SHRA HAVE BEEN SLOW TO ARRIVE. WITH WINDS VEERING SLIGHTLY...EXPECT MVFR CIGS AND -SHRA (NO VIS RESTRICTION) TO BECOME A BIT MORE PREVALENT AT KSAW. CHILLY AIRMASS WILL CONTINUE TO YIELD SOME LAKE EFFECT -SHRA INTO THE EARLY EVENING HRS...ESPECIALLY AT KCMX. GIVEN THE OVERWATER INSTABILITY AND NW TO WNW LOW-LEVEL FLOW TONIGHT...EXPECT LAKE EFFECT CLOUDS TO LINGER A BIT LONGER THAN PREVIOUS FCST INDICATED...AGAIN ESPECIALLY AT KCMX MORE SO THAN KSAW. VFR CONDITIONS SHOULD PREVAIL VERY LATE TONIGHT THRU SAT MORNING AT BOTH SITES HAS HIGH PRES RIDGE ARRIVES WITH DRIER AIR/MODERATING AIRMASS AND BACKING WINDS. && .MARINE (FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)... COLD FRONT HAS CLEARED EASTERN LAKE SUPERIOR SO EXPECT W/NW WINDS 25-30KT TO DEVELOP OVER MOST OF THE LAKE THIS MORNING. PRES RISE CROSSING THE LAKE ATTM WILL BOOST WINDS TEMPORARILY THIS MORNING. AS TROFFING OVER THE LAKE SUBSIDES LATE TODAY AND RIDGING BUILDS IN...COULD SEE ANOTHER BOOST TO THE WINDS. DURING EITHER OF THESE TIME FRAMES WINDS MAY GUST TO 35 KNOT GALES THOUGH GALES DO NOT LOOK WIDESPREAD OR LONG LASTING ENOUGH TO ISSUE A GALE WARNING. HIGH PRES CONTINUES TO BUILD IN LATE TONIGHT INTO SAT. ON THE BACKSIDE OF THE HIGH...SW WINDS WILL AGAIN INCREASE TO 20 TO 25 KT LATER SAT INTO SUN. && .MQT WATCHES/WARNINGS/ADVISORIES... GALE WARNING LAKE SUPERIOR. FREEZE WARNING 06Z-12Z SAT MIZ002-004-009>011-084. FROST ADVISORY 06Z-12Z SAT MI003-005-012-013. && $$ UPDATE...ROLFSON PREV DISCUSSION...VOSS AVIATION...ROLFSON MARINE...JLA mi AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE MARQUETTE MI 1112 AM EDT FRI SEP 14 2007 .UPDATE... SHORTWAVE TROF IS NOW MOVING ACROSS WRN LAKE SUPERIOR/WRN UPPER MI WITH ABUNDANT LOW LEVEL MOISTURE ROTATING INTO THE FCST AREA. 12Z KINL SOUNDING SHOWED NEAR SATURATION TO AROUND 750MB WHILE CWPL SOUNDING SHOWED SATURATION TO 750MB. 850MB TEMPS AT BOTH SITES WERE -6C. DEEP MOISTURE/CYCLONIC FLOW AND INCREASING OVERWATER INSTABILITY ARE LEADING TO A GRADUAL INCREASE IN LAKE EFFECT PCPN THIS MORNING. WHILE THERE HAVE NOT BEEN ANY REPORTS OF SNOW FROM SPOTTERS...SNOW HAS BEEN OCCURRING THIS MORNING ACROSS THE LAKE AT GRAND MARAIS MN. GOING FCST FOR THE AFTN IS IN GOOD SHAPE WITH HIGHEST POPS FOR THE AREAS FAVORED FOR LAKE EFFECT PCPN UNDER NW FLOW. A FEW SNOWFLAKES COULD STILL MIX IN WITH THE -SHRA OVER THE HIGHEST TERRAIN OF THE W AND NW. OTHERWISE...TEMPS OVER THE W AND NCNTRL SHOULD RISE VERY LITTLE FROM CURRENT READINGS UNDER CLOUD COVER AND FREQUENT -SHRA. TEMPS HAVE ALREADY REBOUNDED SOME OVER THE E AND SCNTRL WHERE THERE HAS BEEN MORE SUN THIS MORNING. HOWEVER...DON`T EXPECT TEMPS TO RISE ANY HIGHER THAN ABOUT THE MID 50S THERE. && .PREV DISCUSSION (ISSUED AT 521 AM EDT)... MAIN FCST ISSUES INCLUDE SHOWER COVERAGE TODAY AND POSSIBILITY OF SNOW MIXING IN WITH RAIN OVER HIGHER TERRAIN AREAS...AND THEN FREEZE/FROST HEADLINES TONIGHT. WATER VAPOR IMAGERY AND RUC ANALYSIS SHOW A VIGOROUS SHORTWAVE/CLOSED MIDLEVEL LOW MOVING THRU NRN ONTARIO. AT THE SFC...ASSOCIATED LOW PRES WAS LOCATED JUST W OF JAMES BAY WITH A COLD FRONT EXTENDING S ACROSS NRN LAKE MI INTO NRN IL. SHRA ASSOC WITH THIS COLD FRONT HAVE EXITED THE ERN FA FOR THE MOST PART EARLY THIS MORNING AS A DRY SLOT HAS MOVED IN FROM THE WEST. FOCUS FOR TODAY SHIFTS TO SHORTWAVE LOBE AND ASSOC TROUGH/SECONDARY COLD FRONT MOVING DOWN FROM NW ONTARIO. DEEP/MOIST NW CYCLONIC FLOW ALONG THIS SHORTWAVE/TROUGH HAS YIELDED SHOWERS OVER NW ONTARIO AND NRN MN. THICKNESSES AND FREEZING LVLS ARE LOW ENOUGH FOR SOME SNOW SHOWERS TO BE REPORTED THIS MORNING NORTH OF MN BDR INTO ONTARIO. WITH 850 MB TEMPS OF -4 TO -5C POISED TO MOVE ACROSS LAKE SUPERIOR WITH THIS TROUGH/FRONTAL PASSAGE...LAKE-850MB DELTA-T WILL INCREASE TO 15-17C. WITH DEEP INSTABILITY (LAKE INDUCED CAPES IN EXCESS OF 300 J/KG) AND MOIST SNDGS PROFILE TO NEAR 600 MB LOOK FOR LAKE EFFECT RAIN SHOWERS TO DEVELOP ALONG THE NRN TIER COUNTIES. BEST CHCS OF RAIN WILL BE FOR AREAS FAVORED BY 300-320 DIR CBL FLOW SO WILL KEEP LIKELY POPS OR NUMEROUS COVERAGE IN FOR THESE COUNTIES WHILE THE REST OF THE NRN TIER SHOULD SEE SCT SHRA. LOOKING AT 950 TEMPS...SOUNDING PROFILES AND 925-850 MB THICKNESSES...THE POSSIBILITY OF SNOW MIXING IN OVER THE W AND NCNTRL HIGH TERRAIN LOOKS DOUBTFUL...BUT SINCE OBS JUST OVER THE BORDER INTO ONTARIO ARE REPORTING SNOW WILL KEEP A MENTION IN FOR WRN COUNTIES THIS MORNING. THICKNESSES AND TEMPS SHOULD WARM ENOUGH BY AFTERNOON TO KEEP ANY PCPN LIQUID. CLOUDS AND EXPECTED PERSISTENT SHRA SHOULD KEEP TEMPS QUITE COOL FOR MID SEPT. FAVORED THE LOW END OF MOS GUIDANCE WITH LOW TO MID 40S FCST FOR A GOOD PORTION OF THE WRN INTERIOR OF THE CWFA. TEMPS SHOULD BE SOMEWHAT WARMER TO THE E WITH LONGER FETCH OVER LAKE SUPERIOR. HIGHEST TEMPS WILL BE OVER THE SCNTRL AREAS (MID 50S) WITH DOWNSLOPING NW FLOW AND LITTLE OR NO PCPN. RIP CURRENTS ARE ALSO POSSIBLE EAST OF MARQUETTE WITH NORTHWEST WINDS UP TO 30 KT AND HIGH WAVES UP TO 8 TO 11 FT. NEXT BIG PROBLEM WILL BE FROST/FREEZE HEADLINES FOR TONIGHT. SHORTWAVE RIDGING AND ASSOC SFC RDG IS FCST TO BUILD OVER THE WRN INTERIOR OF THE CWFA LATE TONIGHT. AS SKIES CLEAR OUT AND WINDS DECOUPLE BY LATE TONIGHT...GOOD RADIATIONAL COOLING WILL ALLOW TEMPS TO DIP DOWN TO THE UPPER 20S OVER IRON-DICKINSON-GOGEBIC-SOUTHERN HOUGHTON AND INLAND PORTIONS OF ONTONAGON AND BARAGA COUNTIES SO HAVE ISSUED A FREEZE WARNING FOR THESE COUNTIES. MORE PERSISTENT WIND AND CLOUDS WILL KEEP TEMPS UP LONGER FOR NORTHERN HOUGHTON...MARQUETTE...DELTA AND MENOMINEE SO WILL GO WITH A FROST ADVISORY FOR THESE COUNTIES AS TEMPS WILL LIKELY DIP NEAR 30F FOR INLAND PORTIONS. SCATTERED LAKE EFFECT SHRA SHOULD CONTINUE ACROSS THE EASTERN CWA TONIGHT AS WEAKLY CYCLONIC NW FLOW PERSISTS WITH LAKE DELTA-T AROUND 14-15C. SO GIVEN PERSISTENT CLOUDS AND MODERATING NW WINDS OFF LAKE SUPERIOR DO NOT EXPECT A FROST/FREEZE POTENTIAL FOR THE EAST. KEPT IN LOW CHC POPS FOR SHRA EARLY SAT FOR FAR ERN COUNTIES GIVEN ONSHORE NW FLOW BUT FLOW IS ALREADY BECOMING ANTICYCLONIC AS RIDGE AXIS BUILDS IN QUICKLY FROM THE WEST. BACKING FLOW TO WEST BY MIDDAY SHOULD END ANY LAKE EFFECT SHRA. RETURN WSW FLOW ON BACKSIDE OF RIDGE WILL ALLOW FOR A GRADUAL WARMING TREND OVER THE WEEKEND AS 850 MB TEMPS REBOUND TO AROUND 8C BY SUN. LOOK FOR HIGH IN THE UPR 50S TO AROUND 60F ON SAT AND 65 TO 70 RANGE ON SUN UNDER MOSTLY SUNNY SKIES. && .AVIATION (FOR THE 12Z TAF ISSUANCE)... HERE COME THE LOW CLOUDS INTO UPR MI. BASES FLOATING AROUND 3000FT BUT WITH NW WINDS ADVECTING IN COOL/MOIST AIRMASS AND LOW CONVECTIVE TEMPS...SUSPECT CIGS WILL DIP INTO MVFR QUICKLY THIS MORNING. SCT RAIN SHOWERS NOTED ON THE RADAR...A LIGHT MIST NOW OUTSIDE AT OUR OFFICE JUST WEST OF NEGAUNEE...AND WITH COLD AIR ADVECTION...EXPECT COVERAGE IN THE PCPN TO ONLY INCREASE AS LK INSTABILITY BECOMES MORE OF A FACTOR. COULD SEE IFR CONDITIONS FOR A TIME AT KCMX LATER THIS MORNING INTO EARLY AFTN AND AT THE SAME TIME MAY ALSO SEE SOME SNOWFLAKES MIX WITH THE RAIN SHOWERS AS THERMAL TROUGH/DEEP MOISTURE AXIS SHIFTS ACROSS LK SUPERIOR. BOTH THE EVENTS ARE TOO LOW A PROBABILITY TO INCLUDE IN THE TAF. ALL IN ALL...BETTER CHANCES FOR PCPN TODAY WILL BE AT KCMX WITH MORE FAVORABLE TRAJECTORIES. LINGERED LOW CLOUD AT KCMX INTO THE OVERNIGHT HOURS...BUT WITH NW WINDS CLEARED OUT THE CLOUDS AT KSAW THIS EVENING. && .MARINE (FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)... COLD FRONT HAS CLEARED EASTERN LAKE SUPERIOR SO EXPECT W/NW WINDS 25-30KT TO DEVELOP OVER MOST OF THE LAKE THIS MORNING. PRES RISE CROSSING THE LAKE ATTM WILL BOOST WINDS TEMPORARILY THIS MORNING. AS TROFFING OVER THE LAKE SUBSIDES LATE TODAY AND RIDGING BUILDS IN...COULD SEE ANOTHER BOOST TO THE WINDS. DURING EITHER OF THESE TIME FRAMES WINDS MAY GUST TO 35 KNOT GALES THOUGH GALES DO NOT LOOK WIDESPREAD OR LONG LASTING ENOUGH TO ISSUE A GALE WARNING. HIGH PRES CONTINUES TO BUILD IN LATE TONIGHT INTO SAT. ON THE BACKSIDE OF THE HIGH...SW WINDS WILL AGAIN INCREASE TO 20 TO 25 KT LATER SAT INTO SUN. && .MQT WATCHES/WARNINGS/ADVISORIES... GALE WARNING LAKE SUPERIOR. FREEZE WARNING 06Z-12Z SAT MIZ002-004-009>011-084. FROST ADVISORY 06Z-12Z SAT MI003-005-012-013. && $$ UPDATE...ROLFSON PREV DISCUSSION...VOSS AVIATION...JLA MARINE...JLA mi AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE MARQUETTE MI 755 AM EDT FRI SEP 14 2007 UPDATED AVIATION DISCUSSION FOR 12Z TAFS .DISCUSSION... MAIN FCST ISSUES INCLUDE SHOWER COVERAGE TODAY AND POSSIBILITY OF SNOW MIXING IN WITH RAIN OVER HIGHER TERRAIN AREAS...AND THEN FREEZE/FROST HEADLINES TONIGHT. WATER VAPOR IMAGERY AND RUC ANALYSIS SHOW A VIGOROUS SHORTWAVE/CLOSED MIDLEVEL LOW MOVING THRU NRN ONTARIO. AT THE SFC...ASSOCIATED LOW PRES WAS LOCATED JUST W OF JAMES BAY WITH A COLD FRONT EXTENDING S ACROSS NRN LAKE MI INTO NRN IL. SHRA ASSOC WITH THIS COLD FRONT HAVE EXITED THE ERN FA FOR THE MOST PART EARLY THIS MORNING AS A DRY SLOT HAS MOVED IN FROM THE WEST. FOCUS FOR TODAY SHIFTS TO SHORTWAVE LOBE AND ASSOC TROUGH/SECONDARY COLD FRONT MOVING DOWN FROM NW ONTARIO. DEEP/MOIST NW CYCLONIC FLOW ALONG THIS SHORTWAVE/TROUGH HAS YIELDED SHOWERS OVER NW ONTARIO AND NRN MN. THICKNESSES AND FREEZING LVLS ARE LOW ENOUGH FOR SOME SNOW SHOWERS TO BE REPORTED THIS MORNING NORTH OF MN BDR INTO ONTARIO. WITH 850 MB TEMPS OF -4 TO -5C POISED TO MOVE ACROSS LAKE SUPERIOR WITH THIS TROUGH/FRONTAL PASSAGE...LAKE-850MB DELTA-T WILL INCREASE TO 15-17C. WITH DEEP INSTABILITY (LAKE INDUCED CAPES IN EXCESS OF 300 J/KG) AND MOIST SNDGS PROFILE TO NEAR 600 MB LOOK FOR LAKE EFFECT RAIN SHOWERS TO DEVELOP ALONG THE NRN TIER COUNTIES. BEST CHCS OF RAIN WILL BE FOR AREAS FAVORED BY 300-320 DIR CBL FLOW SO WILL KEEP LIKELY POPS OR NUMEROUS COVERAGE IN FOR THESE COUNTIES WHILE THE REST OF THE NRN TIER SHOULD SEE SCT SHRA. LOOKING AT 950 TEMPS...SOUNDING PROFILES AND 925-850 MB THICKNESSES...THE POSSIBILITY OF SNOW MIXING IN OVER THE W AND NCNTRL HIGH TERRAIN LOOKS DOUBTFUL...BUT SINCE OBS JUST OVER THE BORDER INTO ONTARIO ARE REPORTING SNOW WILL KEEP A MENTION IN FOR WRN COUNTIES THIS MORNING. THICKNESSES AND TEMPS SHOULD WARM ENOUGH BY AFTERNOON TO KEEP ANY PCPN LIQUID. CLOUDS AND EXPECTED PERSISTENT SHRA SHOULD KEEP TEMPS QUITE COOL FOR MID SEPT. FAVORED THE LOW END OF MOS GUIDANCE WITH LOW TO MID 40S FCST FOR A GOOD PORTION OF THE WRN INTERIOR OF THE CWFA. TEMPS SHOULD BE SOMEWHAT WARMER TO THE E WITH LONGER FETCH OVER LAKE SUPERIOR. HIGHEST TEMPS WILL BE OVER THE SCNTRL AREAS (MID 50S) WITH DOWNSLOPING NW FLOW AND LITTLE OR NO PCPN. RIP CURRENTS ARE ALSO POSSIBLE EAST OF MARQUETTE WITH NORTHWEST WINDS UP TO 30 KT AND HIGH WAVES UP TO 8 TO 11 FT. NEXT BIG PROBLEM WILL BE FROST/FREEZE HEADLINES FOR TONIGHT. SHORTWAVE RIDGING AND ASSOC SFC RDG IS FCST TO BUILD OVER THE WRN INTERIOR OF THE CWFA LATE TONIGHT. AS SKIES CLEAR OUT AND WINDS DECOUPLE BY LATE TONIGHT...GOOD RADIATIONAL COOLING WILL ALLOW TEMPS TO DIP DOWN TO THE UPPER 20S OVER IRON-DICKINSON-GOGEBIC-SOUTHERN HOUGHTON AND INLAND PORTIONS OF ONTONAGON AND BARAGA COUNTIES SO HAVE ISSUED A FREEZE WARNING FOR THESE COUNTIES. MORE PERSISTENT WIND AND CLOUDS WILL KEEP TEMPS UP LONGER FOR NORTHERN HOUGHTON...MARQUETTE...DELTA AND MENOMINEE SO WILL GO WITH A FROST ADVISORY FOR THESE COUNTIES AS TEMPS WILL LIKELY DIP NEAR 30F FOR INLAND PORTIONS. SCATTERED LAKE EFFECT SHRA SHOULD CONTINUE ACROSS THE EASTERN CWA TONIGHT AS WEAKLY CYCLONIC NW FLOW PERSISTS WITH LAKE DELTA-T AROUND 14-15C. SO GIVEN PERSISTENT CLOUDS AND MODERATING NW WINDS OFF LAKE SUPERIOR DO NOT EXPECT A FROST/FREEZE POTENTIAL FOR THE EAST. KEPT IN LOW CHC POPS FOR SHRA EARLY SAT FOR FAR ERN COUNTIES GIVEN ONSHORE NW FLOW BUT FLOW IS ALREADY BECOMING ANTICYCLONIC AS RIDGE AXIS BUILDS IN QUICKLY FROM THE WEST. BACKING FLOW TO WEST BY MIDDAY SHOULD END ANY LAKE EFFECT SHRA. RETURN WSW FLOW ON BACKSIDE OF RIDGE WILL ALLOW FOR A GRADUAL WARMING TREND OVER THE WEEKEND AS 850 MB TEMPS REBOUND TO AROUND 8C BY SUN. LOOK FOR HIGH IN THE UPR 50S TO AROUND 60F ON SAT AND 65 TO 70 RANGE ON SUN UNDER MOSTLY SUNNY SKIES. && .AVIATION (FOR THE 12Z TAF ISSUANCE)... HERE COME THE LOW CLOUDS INTO UPR MI. BASES FLOATING AROUND 3000FT BUT WITH NW WINDS ADVECTING IN COOL/MOIST AIRMASS AND LOW CONVECTIVE TEMPS...SUSPECT CIGS WILL DIP INTO MVFR QUICKLY THIS MORNING. SCT RAIN SHOWERS NOTED ON THE RADAR...A LIGHT MIST NOW OUTSIDE AT OUR OFFICE JUST WEST OF NEGAUNEE...AND WITH COLD AIR ADVECTION...EXPECT COVERAGE IN THE PCPN TO ONLY INCREASE AS LK INSTABILITY BECOMES MORE OF A FACTOR. COULD SEE IFR CONDITIONS FOR A TIME AT KCMX LATER THIS MORNING INTO EARLY AFTN AND AT THE SAME TIME MAY ALSO SEE SOME SNOWFLAKES MIX WITH THE RAIN SHOWERS AS THERMAL TROUGH/DEEP MOISTURE AXIS SHIFTS ACROSS LK SUPERIOR. BOTH THE EVENTS ARE TOO LOW A PROBABILITY TO INCLUDE IN THE TAF. ALL IN ALL...BETTER CHANCES FOR PCPN TODAY WILL BE AT KCMX WITH MORE FAVORABLE TRAJECTORIES. LINGERED LOW CLOUD AT KCMX INTO THE OVERNIGHT HOURS...BUT WITH NW WINDS CLEARED OUT THE CLOUDS AT KSAW THIS EVENING. && .MARINE (FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)... COLD FRONT HAS CLEARED EASTERN LAKE SUPERIOR SO EXPECT W/NW WINDS 25-30KT TO DEVELOP OVER MOST OF THE LAKE THIS MORNING. PRES RISE CROSSING THE LAKE ATTM WILL BOOST WINDS TEMPORARILY THIS MORNING. AS TROFFING OVER THE LAKE SUBSIDES LATE TODAY AND RIDGING BUILDS IN...COULD SEE ANOTHER BOOST TO THE WINDS. DURING EITHER OF THESE TIME FRAMES WINDS MAY GUST TO 35 KNOT GALES THOUGH GALES DO NOT LOOK WIDESPREAD OR LONG LASTING ENOUGH TO ISSUE A GALE WARNING. HIGH PRES CONTINUES TO BUILD IN LATE TONIGHT INTO SAT. ON THE BACKSIDE OF THE HIGH...SW WINDS WILL AGAIN INCREASE TO 20 TO 25 KT LATER SAT INTO SUN. && .MQT WATCHES/WARNINGS/ADVISORIES... FREEZE WARNING 06Z-12Z SAT MIZ002-004-009>011-084. FROST ADVISORY 06Z-12Z SAT MI003-005-012-013. && $$ DISCUSSION...VOSS AVIATION...JLA MARINE...JLA mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MARQUETTE MI 521 AM EDT FRI SEP 14 2007 .DISCUSSION... MAIN FCST ISSUES INCLUDE SHOWER COVERAGE TODAY AND POSSIBILITY OF SNOW MIXING IN WITH RAIN OVER HIGHER TERRAIN AREAS...AND THEN FREEZE/FROST HEADLINES TONIGHT. WATER VAPOR IMAGERY AND RUC ANALYSIS SHOW A VIGOROUS SHORTWAVE/CLOSED MIDLEVEL LOW MOVING THRU NRN ONTARIO. AT THE SFC...ASSOCIATED LOW PRES WAS LOCATED JUST W OF JAMES BAY WITH A COLD FRONT EXTENDING S ACROSS NRN LAKE MI INTO NRN IL. SHRA ASSOC WITH THIS COLD FRONT HAVE EXITED THE ERN FA FOR THE MOST PART EARLY THIS MORNING AS A DRY SLOT HAS MOVED IN FROM THE WEST. FOCUS FOR TODAY SHIFTS TO SHORTWAVE LOBE AND ASSOC TROUGH/SECONDARY COLD FRONT MOVING DOWN FROM NW ONTARIO. DEEP/MOIST NW CYCLONIC FLOW ALONG THIS SHORTWAVE/TROUGH HAS YIELDED SHOWERS OVER NW ONTARIO AND NRN MN. THICKNESSES AND FREEZING LVLS ARE LOW ENOUGH FOR SOME SNOW SHOWERS TO BE REPORTED THIS MORNING NORTH OF MN BDR INTO ONTARIO. WITH 850 MB TEMPS OF -4 TO -5C POISED TO MOVE ACROSS LAKE SUPERIOR WITH THIS TROUGH/FRONTAL PASSAGE...LAKE-850MB DELTA-T WILL INCREASE TO 15-17C. WITH DEEP INSTABILITY (LAKE INDUCED CAPES IN EXCESS OF 300 J/KG) AND MOIST SNDGS PROFILE TO NEAR 600 MB LOOK FOR LAKE EFFECT RAIN SHOWERS TO DEVELOP ALONG THE NRN TIER COUNTIES. BEST CHCS OF RAIN WILL BE FOR AREAS FAVORED BY 300-320 DIR CBL FLOW SO WILL KEEP LIKELY POPS OR NUMEROUS COVERAGE IN FOR THESE COUNTIES WHILE THE REST OF THE NRN TIER SHOULD SEE SCT SHRA. LOOKING AT 950 TEMPS...SOUNDING PROFILES AND 925-850 MB THICKNESSES...THE POSSIBILITY OF SNOW MIXING IN OVER THE W AND NCNTRL HIGH TERRAIN LOOKS DOUBTFUL...BUT SINCE OBS JUST OVER THE BORDER INTO ONTARIO ARE REPORTING SNOW WILL KEEP A MENTION IN FOR WRN COUNTIES THIS MORNING. THICKNESSES AND TEMPS SHOULD WARM ENOUGH BY AFTERNOON TO KEEP ANY PCPN LIQUID. CLOUDS AND EXPECTED PERSISTENT SHRA SHOULD KEEP TEMPS QUITE COOL FOR MID SEPT. FAVORED THE LOW END OF MOS GUIDANCE WITH LOW TO MID 40S FCST FOR A GOOD PORTION OF THE WRN INTERIOR OF THE CWFA. TEMPS SHOULD BE SOMEWHAT WARMER TO THE E WITH LONGER FETCH OVER LAKE SUPERIOR. HIGHEST TEMPS WILL BE OVER THE SCNTRL AREAS (MID 50S) WITH DOWNSLOPING NW FLOW AND LITTLE OR NO PCPN. RIP CURRENTS ARE ALSO POSSIBLE EAST OF MARQUETTE WITH NORTHWEST WINDS UP TO 30 KT AND HIGH WAVES UP TO 8 TO 11 FT. NEXT BIG PROBLEM WILL BE FROST/FREEZE HEADLINES FOR TONIGHT. SHORTWAVE RIDGING AND ASSOC SFC RDG IS FCST TO BUILD OVER THE WRN INTERIOR OF THE CWFA LATE TONIGHT. AS SKIES CLEAR OUT AND WINDS DECOUPLE BY LATE TONIGHT...GOOD RADIATIONAL COOLING WILL ALLOW TEMPS TO DIP DOWN TO THE UPPER 20S OVER IRON-DICKINSON-GOGEBIC-SOUTHERN HOUGHTON AND INLAND PORTIONS OF ONTONAGON AND BARAGA COUNTIES SO HAVE ISSUED A FREEZE WARNING FOR THESE COUNTIES. MORE PERSISTENT WIND AND CLOUDS WILL KEEP TEMPS UP LONGER FOR NORTHERN HOUGHTON...MARQUETTE...DELTA AND MENOMINEE SO WILL GO WITH A FROST ADVISORY FOR THESE COUNTIES AS TEMPS WILL LIKELY DIP NEAR 30F FOR INLAND PORTIONS. SCATTERED LAKE EFFECT SHRA SHOULD CONTINUE ACROSS THE EASTERN CWA TONIGHT AS WEAKLY CYCLONIC NW FLOW PERSISTS WITH LAKE DELTA-T AROUND 14-15C. SO GIVEN PERSISTENT CLOUDS AND MODERATING NW WINDS OFF LAKE SUPERIOR DO NOT EXPECT A FROST/FREEZE POTENTIAL FOR THE EAST. KEPT IN LOW CHC POPS FOR SHRA EARLY SAT FOR FAR ERN COUNTIES GIVEN ONSHORE NW FLOW BUT FLOW IS ALREADY BECOMING ANTICYCLONIC AS RIDGE AXIS BUILDS IN QUICKLY FROM THE WEST. BACKING FLOW TO WEST BY MIDDAY SHOULD END ANY LAKE EFFECT SHRA. RETURN WSW FLOW ON BACKSIDE OF RIDGE WILL ALLOW FOR A GRADUAL WARMING TREND OVER THE WEEKEND AS 850 MB TEMPS REBOUND TO AROUND 8C BY SUN. LOOK FOR HIGH IN THE UPR 50S TO AROUND 60F ON SAT AND 65 TO 70 RANGE ON SUN UNDER MOSTLY SUNNY SKIES. && .AVIATION (FOR THE 06Z TAF ISSUANCE)... BEHIND THE FRONT...VFR CONDITIONS AND DRY WEATHER SHOULD PREVAIL UNTIL LATER IN THE NIGHT. LATER TONIGHT...MOISTURE WRAPPING AROUND THE BACKSIDE OF LOW PRES IN ONTARIO WILL BRING A LOWERING OF CIGS INTO THE MVFR RANGE...FIRST AT KCMX. NOTE THE LARGE AREA OF MVFR CIGS UPSTREAM IN NRN MN AND WRN ONTARIO. IN ADDITION...INCREASINGLY CHILLY AIRMASS WILL LEAD TO LAKE EFFECT -SHRA DEVELOPMENT WHICH WILL BE FURTHER AIDED BY DEEP CYCLONIC FLOW. NOT TOTALLY OUT OF THE QUESTION THAT IFR CIGS COULD DEVELOP FOR A TIME AT KCMX FRI MORNING UNDER FAVORABLE UPSLOPING NW LOW-LEVEL FLOW...BUT THAT POTENTIAL APPEARS MINIMAL AT THIS POINT AND WILL NOT BE INCLUDED IN THIS FCST ISSUANCE. KCMX WILL ALSO SEE STRONGER WINDS THAN KSAW DUE TO TERRAIN AFFECTS AND UNSTABLE NW FLOW ACROSS THE LAKE. SOME IMPROVEMENT IS EXPECTED FRI AFTERNOON WITH VFR CIGS LATE AS DRIER AIR FILTERS IN FROM THE WEST AHEAD OF THE PLAINS SFC HIGH. && .MARINE (FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)... COLD FRONT HAS CLEARED EASTERN LAKE SUPERIOR SO EXPECT W/NW WINDS 25-30KT TO DEVELOP OVER MOST OF THE LAKE THIS MORNING. PRES RISE CROSSING THE LAKE ATTM WILL BOOST WINDS TEMPORARILY THIS MORNING. AS TROFFING OVER THE LAKE SUBSIDES LATE TODAY AND RIDGING BUILDS IN...COULD SEE ANOTHER BOOST TO THE WINDS. DURING EITHER OF THESE TIME FRAMES WINDS MAY GUST TO 35 KNOT GALES THOUGH GALES DO NOT LOOK WIDESPREAD OR LONG LASTING ENOUGH TO ISSUE A GALE WARNING. HIGH PRES CONTINUES TO BUILD IN LATE TONIGHT INTO SAT. ON THE BACKSIDE OF THE HIGH...SW WINDS WILL AGAIN INCREASE TO 20 TO 25 KT LATER SAT INTO SUN. && .MQT WATCHES/WARNINGS/ADVISORIES... FREEZE WARNING 06Z-12Z SAT MIZ002-004-009>011-084. FROST ADVISORY 06Z-12Z SAT MI003-005-012-013. && $$ DISCUSSION...VOSS AVIATION...JLB MARINE...JLA mi AREA FORECAST DISCUSSION...UPDATED FOR AVIATION NATIONAL WEATHER SERVICE MARQUETTE MI 220 AM EDT FRI SEP 14 2007 .DISCUSSION... .SHORT TERM (TONIGHT AND FRIDAY)... MAIN FCST ISSUE ARE SHRA/TSRA COVERAGE. WATER VAPOR IMAGERY AND RUC ANALYSIS SHOW A VIGOROUS SHORTWAVE/CLOSED MIDLEVEL LOW MOVING THRU NRN ONTARIO. AT THE SFC...ASSOCIATED LOW PRES WAS LOCATED JUST SW OF CYPL WITH A COLD FRONT EXTENDING ACROSS WRN LAKE SUPERIOR/FAR WRN UPPER MI INTO CNTRL IA. APPEARS A BAND OF ACCUMULATING SNOW HAS BEEN OCCURRING JUST N OF THE SFC LOW TRACK IN NRN ONTARIO TODAY. FARTHER S...BAND OF SHRA AND ISOLATED TSRA AHEAD OF THE COLD FRONT HAS BEEN PROGRESSING ACROSS THE W HALF OF UPPER MI THIS AFTN. PCPN HAS HAD SOME DIFFICULTY HOLDING TOGETHER...SO HIGH CHC/SCT POPS WILL BE UTILIZED LATE THIS AFTN/EARLY THIS EVENING AS PCPN MOVES INTO THE ERN FCST AREA. THERE IS A FAIRLY SUBSTANTIAL BREAK IN THE PCPN BEHIND THE COLD FRONT AS MIDLEVEL DRYING SURGES AROUND THE S SIDE OF THE SHORTWAVE TO THE N. SO...ONCE PCPN ENDS SHORTLY AFTER FROPA...DO NOT EXPECT ANY PCPN AGAIN UNTIL LATE IN THE NIGHT WHEN DEEP MOISTURE ROTATES BACK INTO THE AREA BEHIND THE SHORTWAVE. LAKE EFFECT PCPN WILL ALSO BECOME INVOLVED AS 850MB TEMPS DROP TO AROUND -4C OVER THE WRN LAKE BY 12Z FRI. HAVE REMOVED ANY MENTION OF POSSIBLE SNOW AS AT LEAST THE LOWEST 1500FT ABOVE GROUND REMAIN ABOVE FREEZING. LAKE EFFECT SHRA SHOULD BECOME WIDESPREAD FRI MORNING UNDER DEEP/MOIST NW CYCLONIC FLOW WITH LAKE-850MB DELTA-T INCREASING TO 15-18C. WHILE THE POSSIBILITY OF SOME SNOWFLAKES MIXING IN OVER THE W AND NCNTRL HIGH TERRAIN LOOKS DOUBTFUL...SOUNDINGS SUGGEST THAT FREEZING LEVEL WILL BE LOW ENOUGH THAT IT CAN`T BE RULED OUT COMPLETELY. AS OFTEN OCCURS IN EARLY SEASON LAKE EFFECT...IT WOULD PROBABLY BE MORE LIKELY THAT GRAUPEL WOULD OCCUR RATHER THAN SNOWFLAKES. WITH EXPECTATION OF PLENTY OF CLOUDS AND PERSISTENT LIGHT -SHRA...IT WILL BE A VERY CHILLY DAY FOR MID SEPT OVER THE W AND NCNTRL. FAVORED THE LOW END OF MOS GUIDANCE WITH WIDESPREAD MID 40S AT BEST THOUGH A FEW AREAS MAY ONLY REACH THE LWR 40S WHERE LAKE EFFECT PCPN IS MOST PERSISTENT. TEMPS WILL BE SOMEWHAT WARMER TO THE E WITH LONG FETCH OVER THE LAKE. HIGHEST TEMPS WILL BE OVER THE SCNTRL AREAS (MID 50S) WITH DOWNSLOPING NW FLOW AND LITTLE OR NO PCPN. RIP CURRENTS ARE POSSIBLE EAST OF MARQUETTE ON FRIDAY WITH NORTHWEST WINDS UP TO 25 KT AND HIGH WAVES UP TO 6 TO 10 FT. LONGER TERM...00Z SAT ONWARDS... BIGGEST PROBLEM IS GOING TO BE THE FROST/FREEZE LATE FRI NIGHT AND EARLY SAT MORNING. AREA STAYS UNDER A BROAD 500 MB TROUGH THROUGH THE PERIOD WITH A STRONG SHORTWAVE 500 MB TROUGH TO THE EAST OF THE CWA BY FRI NIGHT ALREADY. LAKE EFFECT PCPN SHOULD CONTINUE ACROSS THE EASTERN CWA FRI NIGHT WITH LAKE EFFECT CLOUDS REMAINING...SO NO FREEZE OR FROST POTENTIAL ACROSS THE ERN CWA AS NAM AND GFS BOTH SHOW 850 MB TEMPERATURES OF -2C TO -4C AND WITH LAKE TEMPS OF 10C TO 15C...THAT IS ENOUGH FOR LAKE EFFECT CLOUDS WHICH SHOULD REMAIN OVER THE EAST. THINGS GET TRICKIER IN THE WEST. WINDS LOOK TO STAY UP THROUGH MIDNIGHT AT LEAST WHICH SHOULD PREVENT TEMPERATURES FROM GETTING TO FREEZING FOR A WHILE. AS SKIES CLEAR OUT AND WINDS DIE DOWN...GOOD RADIATIONAL COOLING CONDITIONS SET UP LATE WHICH SHOULD GET TEMPS DOWN TO THE UPPER 20S IN PLACES AND CONTINUED THE FREEZE WATCH WHICH CONTINUED TO LOOK GOOD. WENT CLOSE TO ADJMAV FOR LOWS AND HIGHS WHICH SEEMED GOOD. REMOVED POPS FROM SUN EVENING AS COLD FRONT NOW LOOKS TO GET HUNG UP TO THE NORTH AND DOES NOT HAVE MUCH MOISTURE AVAILABLE WITH IT AND FRONT SHOULD ONLY BE A WINDSHIFT NOW AS COLD AIR STAYS WELL NORTH INTO CANADA. OTHER THAN THAT...QUIET WEATHER WITH A WARM UP WITH TEMPERATURES GETTING BACK ABOVE NORMAL BY SUN. ONE POSSIBILITY WHICH WAS THOUGHT ABOUT BRIEFLY WAS LAKE EFFECT SHOWERS ON SUN WITH S TO SW FLOW OFF LAKE MICHIGAN AS NAM IS SHOWING 850 MB TEMPERATURES OF 4C IN THE AFTERNOON WHICH WITH LAKE TEMPERATURES OF 18C...MIGHT BE ENOUGH TO CONSIDER. NAM IS PUTTING OUT SOME PCPN ALONG THE LAKE MICHIGAN SHORELINE EAST OF KISQ ANYWAY AND MAY BE PICKING UP ON THIS. COULD BE POSSIBLE...BUT THINK CHANCE IS LOW ENOUGH TO NOT MENTION AT THIS TIME. WILL HAVE TO CONTINUE TO WATCH THOUGH FOR SUN WITH WINDS COMING BACK AROUND AND LAKE-850 MB DELTA-T IN CRITICAL AREA. IN THE EXTENDED...GFS...ECMWF AND CANADIAN ALL SHOW THE 500 MB PATTERN CONSISTS OF A TROUGH IN THE WEST AND ACROSS SOUTH CENTRAL CANADA WITH RIDGING ACROSS THE SOUTHERN U.S. 00Z MON. THE TROUGH ACROSS SOUTH CENTRAL CANADA STAYS TO THE NORTH OF THE AREA AND IS FOLLOWED BY RIDGING FOR 00Z TUE POKING INTO THE AREA AND THE RIDGING CONTINUES TO BUILD TO THE EAST 00Z WED WITH TROUGHING ASSOCIATED WITH THE WESTERN U.S. MOVING IN FOR 00Z THU. RIDGING THEN COMES BACK IN FOR 00Z FRI. WARM FRONT MOVES THROUGH THE AREA ON TUE...AND THEN COLD FRONT ON WED. FOLLOWED THE 00Z ECMWF SOLUTION PRETTY CLOSELY AND WENT WARMER CLOSE TO ADJMXR TEMPERATURES WHICH WERE PRETTY CLOSE. SPED THINGS UP A BIT AND PUT CHANCE POPS IN FOR TUE AND TUE NIGHT WITH THE WARM FRONT AND THEN MOVED PCPN OUT OF WESTERN CWA ON WED AS COLD FRONT IS ALREADY PAST. TEMPERATURES LOOK TO BE ABOVE NORMAL. A FEW CHANGES HERE AND THERE...BUT OVERALL NOT MUCH CHANGE FROM THE PREVIOUS FORECAST. WENT DRY FOR WED NIGHT AND THU WITH RIDGING BACK IN THE AREA. && .AVIATION (FOR THE 06Z TAF ISSUANCE)... BEHIND THE FRONT...VFR CONDITIONS AND DRY WEATHER SHOULD PREVAIL UNTIL LATER IN THE NIGHT. LATER TONIGHT...MOISTURE WRAPPING AROUND THE BACKSIDE OF LOW PRES IN ONTARIO WILL BRING A LOWERING OF CIGS INTO THE MVFR RANGE...FIRST AT KCMX. NOTE THE LARGE AREA OF MVFR CIGS UPSTREAM IN NRN MN AND WRN ONTARIO. IN ADDITION...INCREASINGLY CHILLY AIRMASS WILL LEAD TO LAKE EFFECT -SHRA DEVELOPMENT WHICH WILL BE FURTHER AIDED BY DEEP CYCLONIC FLOW. NOT TOTALLY OUT OF THE QUESTION THAT IFR CIGS COULD DEVELOP FOR A TIME AT KCMX FRI MORNING UNDER FAVORABLE UPSLOPING NW LOW-LEVEL FLOW...BUT THAT POTENTIAL APPEARS MINIMAL AT THIS POINT AND WILL NOT BE INCLUDED IN THIS FCST ISSUANCE. KCMX WILL ALSO SEE STRONGER WINDS THAN KSAW DUE TO TERRAIN AFFECTS AND UNSTABLE NW FLOW ACROSS THE LAKE. SOME IMPROVEMENT IS EXPECTED FRI AFTERNOON WITH VFR CIGS LATE AS DRIER AIR FILTERS IN FROM THE WEST AHEAD OF THE PLAINS SFC HIGH. && .MARINE (FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)... COLD FRONT PROGRESSING ACROSS LAKE SUPERIOR THIS EVENING WILL BRING AN END TO SRLY GALES OVER THE E PART OF THE LAKE IN THE NEXT FEW HRS. AFTER FROPA...EXPECT A SUSTAINED PERIOD OF W AND THEN NW 25-30KT WINDS TONIGHT THRU FRIDAY. COULD BE CLOSE TO NW GALES OVER THE E HALF OF THE LAKE FRI AFTN/EVENING WITH DEEP INSTABILITY RESULTING IN EFFICIENT MIXING OF STRONGER WINDS TO THE LAKE SFC. SINCE WINDS IN THE MIXED LAYER ARE NO HIGHER THAN ABOUT 31KT AND THERE IS NO ADDITIVE ISALLOBARIC COMPONENT...WILL KEEP WINDS TO JUST 30KT. WINDS WILL DIMINISH FRI NIGHT/SAT MORNING AS HIGH PRES BUILDS INTO THE WRN LAKES. ON THE BACKSIDE OF THE HIGH...SW WINDS WILL AGAIN INCREASE TO 20 TO 25 KT LATER SAT INTO SUN. && .MQT WATCHES/WARNINGS/ADVISORIES... GALE WARNING E HALF LAKE SUPERIOR THROUGH 00Z TONIGHT GALE WARNING LMZ221-248 THROUGH 03Z TONIGHT FREEZE WATCH 06Z-12Z SAT MIZ002-004-005-009>012-084. && $$ LONG TERM...GM AVIATION/MARINE/SHORT TERM...ROLFSON mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BINGHAMTON NY 926 PM EDT SAT SEP 15 2007 .SYNOPSIS... CANADIAN HIGH PRESSURE WILL BRING UNSEASONABLY COOL WEATHER TO CENTRAL NEW YORK AND NORTHEAST PENNSYLVANIA TONIGHT INTO MONDAY. AREAS OF FROST WILL DEVELOP IN NORMALLY COLDER AREAS LATE TONIGHT AS TEMPERATURES FALL TO THE 30S. PATCHY FROST WILL BE POSSIBLE AGAIN SUNDAY NIGHT. A WARMING TREND WILL BEGIN EARLY NEXT WEEK... WITH TEMPERATURES CLIMBING BACK ABOVE NORMAL BY THE SECOND HALF OF THE WEEK. && .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/... LAKE EFFECT -SHRA ARE BEGINNING TO DSPT ACRS NRN ZONES, AS CLDS ALSO BEGIN TO DECREASE. RUC APPEARS TOO MOIST AT LOW LVLS...SUGGESTING BKN-OVC CONDITIONS MANY AREAS TNGT, AND PREFER TEH DRIER DEPICTION OF THE LCL WRF/NAM12 RUNS. TD`S ARE GNRLY IN THE 35 TO 40 RNG MOST SPOTS...WITH MDLS INDICATING POTNL FOR COLDEST MIN TEMPS OVER THE WRN CATSKILLS AS 925-850 FLOW TURNS MORE NRLY REDUCING LAKE ONTARIO INFLUENCES. WE ADDED SULLIVAN COUNTY TO THE FROST ADVISORY FOR THIS REASON. JUST SOME MINOR TWEEKS TO THE ZONES/GRIDS IN THE EVNG UPDATE. && .SHORT TERM /6 AM SUNDAY MORNING THROUGH MONDAY/... CLEAR WEATHER WILL CONTINUE SUNDAY THROUGH MONDAY AS HIGH PRESSURE MOVES SLOWLY EAST OFF THE NEW ENGLAND COAST. FROST WILL AGAIN BE A POSSIBILITY SUNDAY NIGHT WITH NEARLY IDEAL RADITIONAL COOLING CONDITIONS EXPECTED. && .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/... QUIET...EARLY FALL LIKEWX FOR THE FCST AREA THRU THE XTNDD PD. LRG SFC HI BLDS INTO THE AREA THIS WEEKEND AND HOLDS RDGG OVER THE NE US. HPR HGTS BLDS THRU THE PD SO DAY TIME TEMPS CLIMB INTO THE MID AND UPR 70S IN THE DRY AIR. SOME HINT THAT ENUF MOISTURE COULD RETURN LATE FRI TO BRING A LOW CHANCE OF SHWRS BUT HAVE ELECTED TO KEEP THE FCST DRY FOR NOW AND SIMPLY AWAIT LTR MODEL RUNS. && .AVIATION /02Z SUNDAY THROUGH THURSDAY/... PRIMARILY VFR CONDITIONS ALL SITES ATTM WITH A FEW MVFR SHRA IMPACTING RME. EXPECT A VERY GRADUAL CLEARING TREND OVER THE NEXT 6 HOURS WITH SKIES GOING FROM BKN/OVC TO FEW/SCT. TOWARDS MORNING...EXPECT VLIFR FOG AT ELM. FOG WILL BE MUCH LESS DENSE IF THE CLOUDINESS IS ABLE TO HANG ON THROUGH THE NIGHT. CURRENT SATELLITE IMAGERY SUGGESTS CLEARING BY AFTER MIDNIGHT...BUT IF THE CLOUDS HOLD LONGER...THEN FOG WILL NOT BE AS BIG OF A PROBLEM. EXPECT NO OVERNIGHT PROBLEMS OUTSIDE OF ELM. DIURNAL CU WILL POP UP THROUGHOUT THE AREA AGAIN ON SUNDAY WITH BASES IN THE 4-5KFT RANGE. NORTHWESTERLY WINDS NEAR 10KTS WILL QUICKLY DIMINISH OVER THE NEXT 2-3 HOURS WITH WINDS 5 KTS OR LESS OVERNIGHT. NORTHWEST WINDS 10 KTS OR LESS WILL REDEVELOP BY MID MORNING SUNDAY...REMAINING MUCH LIGHTER THAN THEY WERE TODAY. FOR SUNDAY NIGHT THROUGH THURSDAY...VFR CONDITIONS OUTSIDE OF MORNING FOG /ESP AT ELM/ THROUGH THE PERIOD UNDER HIGH PRESSURE. && .BGM WATCHES/WARNINGS/ADVISORIES... PA...FROST ADVISORY FROM 4 AM TO 9 AM EDT SUNDAY FOR PAZ038>040. NY...FROST ADVISORY FROM 4 AM TO 9 AM EDT SUNDAY FOR NYZ009-022>025- 036-037-044>046-055>057-062. && $$ SYNOPSIS...MSE NEAR TERM...MSE SHORT TERM...MSE LONG TERM...DGM AVIATION...JMA ny AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC 139 AM EDT FRI SEP 14 2007 .SYNOPSIS... THE REMNANTS OF HUMBERTO WILL MOVE NORTHEASTWARD AND AFFECT THE FORECAST AREA TODAY. A COLD FRONT WILL CROSS THE AREA FROM THE NORTHWEST ON SATURDAY...WITH COOL AND DRY HIGH PRESSURE SETTLING IN BEHIND IT THROUGH THE EARLY PART OF NEXT WEEK. && .NEAR TERM /THROUGH TODAY/... BETWEEN 6 AND 12 UTC THE GFS BRINGS AN AREA OF DEEP LAYER ASCENT AND ASSOCIATED CONVECTION ACROSS THE CWFA. THAT/S NOT TOO FAR OFF FROM WHAT/S HAPPENING NOW...AND BY LATE TONIGHT I WOULDN/T BE SURPRISED TO SEE AN AREA OF ORGANIZED PCPN MOVE INTO THE SW PART OF THE FA. THE LATEST RUC ALSO HAS AN H5 WAVE OVER THE WRN FA BY DAWN...SIMILAR TO THE GFS. I UPPED POPS INTO THE LIKELY CATEGORY SOUTH AND WEST OF ASHEVILLE LATER TONIGHT...THOUGH IF THE PCPN FOLLOWS THE GFS TIMING...CATEGORICAL COVERAGE MAY BE REALIZED CLOSER TO 8 OR 9 UTC. SERIES OF H5 SHORTWAVES ARE EXPECTED TO MOVE IN FROM W FRI WHILE DEEP MOISTURE FROM REMNANTS OF HUMBERTO MOVE OVER AREA. AT THE SAME TIME THE SFC BOUNDARY SURGES BACK N OVER S CWA PROVIDING LOW LEVEL CONVERGENCE. WENT WITH CATEGORICAL POPS ACROSS CWA FRI WITH HIGHEST QPF MTNS AND ALONG ESCARPMENT FRI. NOT ESP UNSTABLE FRI BUT EXPECT A CHANCE OF TSTMS THROUGH THE DAY. HIGH TEMPS LOW 80S S TO 70S N WITH SOME 60S IN THE MTNS. && .SHORT TERM /TONIGHT THROUGH SUNDAY NIGHT/... AN UPPER LEVEL LONG WAVE TROUGH WILL PERSIST ALONG THE EAST COAST ON SATURDAY AND SUNDAY. A DRY POST FRONTAL AIR MASS WILL MOVE INTO THE AREA SATURDAY...WITH NORTHERLY DOWNSLOPE FLOW QUICKLY BREAKING UP CLOUDS IN THE LEE OF THE MOUNTAINS...AND WARMING TEMPERATURES A FEW DEGREES ABOVE FRIDAY. SATURDAY NIGHT WILL COOL INTO THE 50S...WITH A NORTHEAST WIND PREVENTING TEMPERATURES FROM REACHING DEW POINTS. THE MODEL DIFFER WITH REGARD TO LOW LEVEL MOISTURE ON SUNDAY...WITH THE NAM SUPPORTING A CLOUDIER FORECAST IN AN EASTERLY FLOW OFF THE ATLANTIC. BOTH MODELS APPEAR TO HINT AT A SURFACE WAVE DEVELOPING ON THE FRONT OVER THE GULF STREAM IN RESPONSE TO A SHORTWAVE TROUGH DIVING SOUTHEAST ACROSS THE SOUTHERN APPALACHIANS. SINCE THE GFS DOES SHOW SOME INCREASE IN MOISTURE...CLOUD COVER WILL BE RAISED ON SUNDAY AND SUNDAY NIGHT...AND TEMPERATURES LOWERED A COUPLE OF DEGREES...BUT POPS WILL NOT BE INTRODUCED AT THIS TIME. && .LONG TERM /MONDAY THROUGH THURSDAY/... SURFACE HIGH PRESSURE IS EXPECTED TO LINGER ALONG THE EASTERN SEABOARD...WITH A COOL NORTHEASTERLY FLOW EAST OF THE MOUNTAINS. CLOUD COVER WILL BE RAISED INITIALLY IN THE UPPER SAVANNAH RIVER VALLE AND THE MOUNTAINS...WHERE EVEN THE DRY GFS SUGGEST SOME MOISTURE WILL LINGER FORM THE WEAK FRONTAL WAVE ON MONDAY. THE GFS AGGRESSIVELY BRINGS MOISTURE WEST FROM THE ATLANTIC TO THE SOUTHERN APPALACHIANS ON TUESDAY AND WEDNESDAY...LEAVING IN THERE ON THURSDAY...AS THE OLD SURFACE FRONT RETURNS WEST AND BACK TO THE COAST...AND ISENTROPIC UPGLIDE AND UPSLOPE FLOW INCREASE. SINCE THIS WOULD REPRESENT A RADICAL DEPARTURE FROM FORECAST CONTINUITY...FOR NOT SKY COVER WILL BE INCREASED MODESTLY FOR MOST OF THE EXTENDED FORECAST. && .AVIATION /06Z FRIDAY THROUGH TUESDAY/... THE SITUATION LOOKS GRIM OVER THE NEXT 24 HOURS AS UPSLOPE FLOW AND ISENTROPIC UPGLIDE AHEAD OF THE REMNANTS OF HUMBERTO SPREAD CLOUDS AND PRECIPITATION UP FROM THE SOUTH AND SOUTHWEST. CONDITIONS ARE IN THE PROCESS OF SLOW DETERIORATION AS OF 05Z AND ALL SITES SHOULD BE MVFR AT LEAST WITH VISIBILITY BY 08Z AT THE LATEST. UPSTREAM OBS SHOW IFR CEILINGS ACROSS N GA SO EXPECT SOME OF THAT TO SPREAD ACROSS KAND/KAVL BY 10Z OR SO. THE VERY LOW CLOUDS COULD VERY WELL OVERSPREAD THE REST OF THE FORECAST AREA...BUT KGSP/KCLT WILL BE KEPT HIGHER THAN THAT UNTIL A TREND IS ESTABLISHED. NEVERTHELESS... VISIBILITY IS EXPECTED TO DROP DOWN TO IFR AROUND SUNRISE. THE POOR CONDITIONS SHOULD PERSIST THROUGH THE MIDDLE PART OF THE DAY WITH SLOW IMPROVEMENT BACK TO MVFR AS THE BOUNDARY LAYER WARMS. THERE COULD BE SOME BRIEF VFR BREAKS IN THE AFTERNOON...BUT CONFIDENCE IS TOO LOW TO INCLUDE IT RIGHT NOW. SOUTHWESTERLY LOW LEVEL FLOW SHOULD KEEP THE MVFR CLOUDS IN UNTIL SOME TIME IN THE LATE EVENING...WHEN THE FLOW STARTS TO VEER AROUND. THIS WILL NOT BE INCLUDED IN THIS ISSUANCE SINCE IT WILL HAPPEN VERY LATE IN THE PERIOD. OUTLOOK FRI THROUGH SUN...CONVECTION LIKELY FRI AS A SFC WAVE MOVES THRU AREA. MVFR CIG AND VIS PSBL FRI MORNING AS UPSLOPE FLOW DEVELOPS ACROSS THE FOOTHILLS AND PIEDMONT. A COLD FRONT IS EXPECTED TO MOVE THROUGH EARLY SAT WITH VFR CONDITIONS FOR WEEKEND AS HIGH PRESSURE BUILDS IN FROM THE NW. && .GSP WATCHES/WARNINGS/ADVISORIES... GA...NONE. NC...NONE. SC...NONE. && $$ SYNOPSIS...JAT NEAR TERM...RB SHORT TERM...JAT LONG TERM...JAT AVIATION...PM sc AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MORRISTOWN TN 1125 AM EDT FRI SEP 14 2007 .DISCUSSION...REMNANTS FROM HUMBERTO MOVING SLOWLY ENEWD NEAR CENTRAL MS/AL BORDER. COUPLE OF LARGE SHIELDS OF RAIN TO NORTHEAST OF HUMBERTO THAT STRETCH THROUGH AND PAST OUR CWA. NORTHERN EDGE OF HUMBERTO SHIELD IN SOUTHERN TN SLIDING TO THE ENE. LOOKING AT PRESENT MOVEMENT AND MODEL TRENDS THINK IT IS SAFE TO BACK OFF POPS SOMEWHAT IN THE NW CORNER OF CWA FOR THE REST OF AFTERNOON. HAVE BACKED POPS TO 40 PERCENT IN THAT CORNER. ELSEWHERE HIGH POPS RULE WITH 100 PERCENT POPS FOR ABOUT THE SOUTHERN 20 PERCENT OF THE AREA AND 80+ PERCENT POPS FOR ABOUT THE SOUTHEASTERN 1/2 OF AREA. MODELS SHOW HUMBERTO CENTER CONTINUING TO WEAKEN AND TURN ALMOST DUE EAST...AND NCEP FORECASTER STATED AN EXPECTED LESSENING FROM THE OVERNIGHT RAIN RATES NORTHEAST OF HUMBERTO. SO HAVE KEPT QPF VALUES FAIRLY CONSERVATIVE...WITH BASIN-AVERAGE AMOUNTS AROUND 0.50 INCH ALONG THE GA BORDER. WOULD NOT BE SURPRISED BY SOME 1-3 INCH ISOLATED AMOUNTS...BUT THINK THAT PRIME FOCUS OF HEAVY RAIN WILL BE SOUTH OF ARE TODAY AND SOUTHEAST OF AREA TONIGHT. 06Z GFS MOVEMENT OF BACK EDGE OF RAIN IS WAY TOO FAST...NAM AND RUC LOOK MUCH MORE REASONABLE. PURE RADAR EXTRAPOLATION PUTS BACK EDGE OF PRECIP AT KCHA ABOUT 530 PM...AT KTYS AT 800 PM...CORNER OF SE TN 700 PM...AND NE CORNER OF TN AT 100 AM. THINK ENTIRE SHIELD WILL SHIFT EASTWARD AND ACCELERATE THE BACK EDGE A LITTLE FASTER THAN THESE ESTIMATES...ESPECIALLY FOR THE 100 AM ESTIMATE FOR NE CORNER OF TN. COLD FRONT STILL PRETTY FAR NORTHWEST AND WILL NOT AFFECT WEATHER FOR THIS AFTERNOON. CURRENT TEMPS IN FORECAST FOR THIS AFTERNOON LOOK VERY GOOD. && .PRELIMINARY POINT TEMPS/POPS... CHATTANOOGA AIRPORT, TN 78 63 79 55 81 / 100 40 10 0 0 KNOXVILLE MCGHEE TYSON AIRPORT, TN 79 62 77 54 79 / 80 30 10 0 0 OAK RIDGE, TN 79 60 76 52 78 / 60 20 10 0 0 TRI CITIES AIRPORT, TN 75 57 75 47 76 / 80 30 10 0 0 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...NONE. TN...NONE. VA...NONE. && $$ GM tn AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN 404 AM CDT SUN SEP 16 2007 .DISCUSSION... OVERCAST LOW/MID LEVEL CLOUDS COVERING THE EASTERN TWO-THIRDS OF THE CWA EARLY THIS MORNING. BACK EDGE RUNS FROM KSTC TO KULM WITH AN EASTWARD MOVEMENT AROUND 17 KNOTS. EXPECT THE CLOUDS TO BREAK UP SOME DURING THE MORNING AS THEY MOVE EAST WITH SKIES BECOMING PARTLY TO MOSTLY SUNNY. STRATUS HAS POPPED UP OVER EASTERN NEBRASKA WITH A MOVEMENT TO THE NORTH. RUC 925MB PROGS SHOW THIS EXPANDING RAPIDLY NORTHEAST THIS MORNING BEFORE DIMINISHING OVER EAST CENTRAL MN EARLY THIS AFTERNOON. WILL ALLOW FOR SOME OF THE STRATUS MAKING IT INTO SOUTH CENTRAL MN THIS MORNING. GFS 300K THETA SURFACE SHOWS THAT THE STRATUS WILL BE ONE OF OUR PROBLEMS DEVELOPING TONIGHT WITH SATURATION SETTING IN. OVERALL...STILL PREFER THE 16/00Z GFS OVER THE NAM. USED THE GFS 24 HOURS AGO AND CONTINUED WITH THAT TREND THIS MORNING. THE MAIN PROBLEM WITH THE 16/00Z NAM IS THE DEEPENING SURFACE LOW OVER MN ON TUESDAY. THE 16/00Z ECMWF...WHICH 24 HOURS AGO WAS A COMPROMISE BETWEEN THE NAM AND GFS...IS NOW MORE IN LINE WITH THE GFS. DO THINK THERE WILL BE A WAVE MOVING NORTHEAST ALONG THE FRONT ON TUESDAY BUT JUST NOT THE DEPTH SHOWN BY THE NAM. AFTER SOME SUNSHINE TODAY...MOISTURE AND INSTABILITY WILL BE ON THE INCREASE ACROSS THE WESTERN AND SOUTHERN CWA TONIGHT. ADDED POPS TO THESE AREAS. THINGS BECOME PRETTY UNSTABLE SUNDAY NIGHT AND I WOULDN`T BE SURPRISED IF A SEVERE STORM OR TWO DEVELOPED BY MONDAY MORNING DUE TO THE INTENSE LOW LEVEL THETA-E ADVECTION AND 30 KNOT WINDS 1500 FEET ABOVE THE GROUND. MONDAY STILL LOOKS BAD FOR SOUTHERN MN IN THE AFTERNOON AND EVENING FOR SURFACE BASED CONVECTION AND POSSIBLE TORNADOES. WILL CONTINUE TO MENTION THE CHANCE FOR TORNADOES IN THE HWO THIS MORNING. A WARM FRONT IS SHOWN TO MAKE IT TO NEAR THE MN RIVER BY MONDAY EVENING. SURFACE DEW POINTS IN THE 60 TO 65 DEGREE RANGE EXPECTED. 6 HOUR PRESSURE FALLS OF 4 MILLIBARS ARE CENTERED NEAR MANKATO. 0-1KM SHEAR IS 30-35 KNOTS WITH 0-6KM SHEAR NEAR 50 KNOTS. 40 KNOT WINDS AT 850MB POKE ALL THE WAY INTO KMSP. THE NAM SHOWS A SIMILAR SCENARIO BUT EVEN WORSE. ELEVATED SEVERE STORMS WILL BE POSSIBLE ON MONDAY TO THE NORTH OF THE WARM FRONT. THE ACTION DOESN`T STOP. ALTHOUGH THE WARM FRONT LIFTS NORTH OF THE AREA MONDAY NIGHT...A COLD FRONT WILL SLOWLY MOVE INTO THE MN CWA ON TUESDAY. MORE CONVECTION IS LIKELY...ESPECIALLY TUESDAY AFTERNOON AND EVENING OVER THE EASTERN CWA AS THE AIRMASS DESTABILIZES. STILL BELIEVE WE WILL HAVE A BREAK ON WEDNESDAY. ANOTHER WAVE OF LOW PRESSURE SHOWN TO APPROACH FROM THE WSW THURSDAY AND FRIDAY. THIS WILL PUSH A WARM FRONT NORTH THROUGH THE AREA WITH MORE SHOWERS AND THUNDERSTORMS. HIGHS/LOWS FOR THE NEXT 72 HOURS NEAR MAV VALUES. && .PREV DISCUSSION... /ISSUED 1234 AM CDT SUN SEP 16 2007/ AVIATION.../06Z TAF ISSUANCE/ MID LEVEL CLOUDS TRANSLATING EAST ACROSS ERN MN AND WRN WI OVERNIGHT. MOISTURE FIELDS ON THE MODELS INDICATE THE ATMOSPHERE WILL ATTEMPT TO SATURATE LOWER AS DAWN APPROACHES. HAVE HINTED AT THIS AT EAU...THOUGH VFR CIGS ARE EXPECTED TO PREVAIL GIVEN DRY LOWEST FEW THOUSAND FT. WINDS SHOULD NOT BE AS BREEZY TODAY AS GRADIENT YESTERDAY WAS SET UP BY DEPTH OF THE DEPARTING HIGH PRESSURE. AS THAT HAS WEAKENED AND SHIFTED WELL SOUTHEAST... SOUTHERLY WINDS ON THE ORDER OF 7 TO 11 KTS SHOULD BE ABOUT IT. WARM AIR ADVECTION ALOFT TONIGHT MAY PROMOTE SOME SHOWERS/T-STORMS TOWARDS AXN AND STC...HOWEVER DEVELOPMENT TIME LOOKS BEYOND CURRENT TAF PERIOD. MAY ALSO BE SOME STRATUS IN THAT TIME AT OTHER TAF SITES. && .MPX WATCHES/WARNINGS/ADVISORIES... MN...NONE. WI...NONE. && $$ RAH/MTF mn AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE OMAHA/VALLEY NE 316 AM CDT SUN SEP 16 2007 .DISCUSSION... MAIN FORECAST CHALLENGE OVER THE NEXT 24 HOURS WILL BE WHETHER ANY CONVECTION CAN FIRE TO OUR WEST/SOUTHWEST THIS AFTERNOON AS MID LEVEL WARM AIR ADVECTION SETS UP...IN THE VICINITY OF A DEVELOPING WARM FRONT. THE NAM/ECMWF ARE THE MOST AGGRESSIVE IN THIS SCENARIO ALLOWING CONVECTION TO DEVELOP ACROSS SCNTRL NEBRASKA AND NORTHEAST KANSAS BY MID TO LATE AFTERNOON. OTHER MODELS SUCH AS THE SREF/GFS/RUC ARE NOT AS ROBUST. AM THINKING THAT IF SOMETHING DOES DEVELOP...IT SHOULD REMAIN ACROSS NERN KS/NWRN MO THIS AFTERNOON AND EARLY EVENING...BUT WILL HAVE TO WATCH TRENDS CLOSELY TO SEE IF IT COULD SNEAK INTO SOUTHEAST NEBRASKA 21Z-03Z TIME FRAME. THE WARM FRONT DOES PUSH NORTH THROUGH THE FORECAST AREA OVERNIGHT. DESPITE SIGNIFICANT WARM AIR ADVECTION ALOFT WHICH COULD GENERATE SOME ISOLATED THUNDERSHOWER ACTIVITY ALONG IT...BUT MOSTLY EAST OF THE REGION WHERE THE NOSE OF THE LOW LEVEL JET FOCUSES. WILL KEEP THINGS MOSTLY DRY OVERNIGHT IN OUR AREA WITH GFS/SREF INDICATING TOO SMALL OF CHANCE TO MENTION. HOWEVER...AFTER MIDNIGHT TONIGHT WE COULD SEE SOME SCATTERED CONVECTION DEVELOP ACROSS NERN NEBRASKA WHERE DEEPER MOISTURE WILL RESIDE AND WHERE THETAE CONVERGENCE MIGHT BE A LITTLE STRONGER. IF THIS PRECIP GETS GOING...IT SHOULD LINGER INTO MONDAY MORNING ACROSS NERN NEBRASKA...WITH FOCUSING SHIFTING FURTHER NORTH OUT OF OUR AREA ALONG THE WARM FRONT IN THE AFTERNOON AS THE ATMOSPHERE REMAINS CAPPED FURTHER SOUTH ACROSS NEBRASKA. AS THE CAP WEAKENS MONDAY EVENING...WE SHOULD SEE CONVECTION DEVELOP SOUTHWARD AHEAD OF THE FRONT INTO OUR CWFA...SOME OF WHICH COULD BE SEVERE. NAM HAS ABOUT 45KTS OF BULK SHEAR ALONG WITH 3000 J/KG OF MUCPAE MONDAY EVENING WHICH COULD RESULT IN SUPERCELLULAR STRUCTURE WITH WIND AND HAIL POTENTIAL BEFORE MIDNIGHT. WILL BOOST POPS INTO THE 50 TO 60 PERCENT RANGE ACROSS NORTHERN CWFA WITH ISOLATED ACTIVITY POSSIBLE ACROSS SRN CWFA BY DAYBREAK TUESDAY. THE FRONT THEN SLOWLY SLIDES SOUTH DURING THE DAY TUESDAY WITH A DECENT UPPER WAVE MOVING THROUGH AND PLENTY OF MOISTURE TO WORK WITH. FEEL CONFIDENT BOOSTING POPS INTO THE 50 TO 70 PERCENT RANGE WITH THE FRONTAL PASSAGE. DEGREE OF INSTABILITY WILL BE A CONCERN ON TUESDAY...BUT STRONGER STORMS COULD DEVELOP AS THE UPPER LEVEL SUPPORT ARRIVES. GFS INDICATING SHEAR INCREASES TO 50 TO 60 KTS BY THAT TIME WITH UP TO 1000 J/KG OF MUCAPE AVAILABLE WHICH SHOULD BE SUFFICIENT FOR AT LEAST A SLIGHT RISK OF MORE SEVERE STORMS. PRECIP WILL LINGERING TUESDAY NIGHT AS THE FRONT DRIFTS SOUTH...ENDING ACROSS THE NWRN CWFA BEHIND THE FRONT. THE FRONT SHOULD STALL BUT THEN BEGIN TO LIFT BACK NORTH WEDNESDAY THROUGH EARLY THURSDAY WITH A CONTINUED CHANCE OF PRECIP AS IT LIFTS NORTH THROUGH THIS TIME. ONE MORE FRONT WILL MOVE THROUGH THE REGION ON FRIDAY BASED ON THE 00Z OPERATIONAL GFS...ALTHOUGH THE ECMWF AND THE GFS ENSEMBLE DON`T REALLY BRING THE FRONT FAR ENOUGH SOUTH TO AFFECT US. WE CURRENTLY HAVE A DRY FORECAST DURING THAT TIME AND MADE NO CHANGES THAT FAR OUT. REGARDING TEMPS...HIGHS TODAY SHOULD REBOUND NICELY OVER YESTERDAY`S CHILLY READINGS. UPPER 70S TO LOWER 80S ARE FORECAST FOR TODAY...BUT THEN INTO THE LOWER 90S ON MONDAY AS THE WARM FRONT LIFTS NORTH. MILD NIGHTS IN STORE THE NEXT COUPLE OF NIGHTS TOO AS WINDS ARE NOT EXPECTED TO DECOUPLE RESULTING IN READINGS IN THE MID TO UPPER 60S. && .AVIATION... VFR CONDITIONS EXPECTED AT KOMA/KLNK THRU PD. HOWEVER...NORTHWARD EXPANDING STRATUS DECK OVR SCENTRAL NEB EARLY THIS MORNING WILL AFFECT KOFK DURING THE EARLY MORNING HOURS WHICH SHOULD RESULT IN SOME IFR CIGS AT THAT SITE. OTHERWISE...MID AND HIGH CLOUDS WL CONT TO MOVE EAST ACROSS THE SITES THRU MUCH OF THE DAY AS MID LEVEL RIDGE AXIS MOVES INTO THE CNTRL PLAINS. SERLY WINDS EXPECTED THRU TAF PD AS SFC LO PRES TROF SLIDES EAST ACROSS THE HI PLAINS. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...NONE. IA...NONE. && $$ DEWALD/GRIFFIS ne AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BINGHAMTON NY 136 AM EDT SUN SEP 16 2007 .SYNOPSIS... CANADIAN HIGH PRESSURE WILL BRING COOL WEATHER TO CENTRAL NEW YORK AND NORTHEAST PENNSYLVANIA INTO MONDAY. AREAS OF FROST WILL DEVELOP IN NORMALLY COLDER AREAS THIS MORNING, AND AGAIN LATE TONIGHT, AS TEMPERATURES FALL TO THE 30S. A WARMING TREND WILL BEGIN MONDAY, WITH TEMPERATURES CLIMBING BACK ABOVE NORMAL BY THE SECOND HALF OF THE WEEK. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... LAKE EFFECT -SHRA ARE BEGINNING TO DSPT ACRS NRN ZONES, AS CLDS ALSO BEGIN TO DECREASE. RUC APPEARS TOO MOIST AT LOW LVLS...SUGGESTING BKN-OVC CONDITIONS MANY AREAS TNGT, AND PREFER TEH DRIER DEPICTION OF THE LCL WRF/NAM12 RUNS. TD`S ARE GNRLY IN THE 35 TO 40 RNG MOST SPOTS...WITH MDLS INDICATING POTNL FOR COLDEST MIN TEMPS OVER THE WRN CATSKILLS AS 925-850 FLOW TURNS MORE NRLY REDUCING LAKE ONTARIO INFLUENCES. WE ADDED SULLIVAN COUNTY TO THE FROST ADVISORY FOR THIS REASON. JUST SOME MINOR TWEEKS TO THE ZONES/GRIDS IN THE EVNG UPDATE. && .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM MONDAY/... CLEAR WEATHER WILL CONTINUE SUNDAY THROUGH MONDAY AS HIGH PRESSURE MOVES SLOWLY EAST OFF THE NEW ENGLAND COAST. FROST WILL AGAIN BE A POSSIBILITY SUNDAY NIGHT WITH NEARLY IDEAL RADITIONAL COOLING CONDITIONS EXPECTED. && .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/... QUIET...EARLY FALL LIKEWX FOR THE FCST AREA THRU THE XTNDD PD. LRG SFC HI BLDS INTO THE AREA THIS WEEKEND AND HOLDS RDGG OVER THE NE US. HPR HGTS BLDS THRU THE PD SO DAY TIME TEMPS CLIMB INTO THE MID AND UPR 70S IN THE DRY AIR. SOME HINT THAT ENUF MOISTURE COULD RETURN LATE FRI TO BRING A LOW CHANCE OF SHWRS BUT HAVE ELECTED TO KEEP THE FCST DRY FOR NOW AND SIMPLY AWAIT LTR MODEL RUNS. && .AVIATION /06Z SUNDAY THROUGH THURSDAY/... PRIMARILY VFR CONDITIONS ALL SITES ATTM. LAKE EFFECT SHOWERS STILL ONGOING AT SYR AND AT TIMES RME AND ITH. GRADUAL CLEARING TREND THROUGH THE MORNING WITH SKIES GOING FROM BKN/OVC TO FEW/SCT. AROUND 11Z ELM MAY HAVE IFR RADIATIONAL VALLEY FOG. SKIES THERE HAVE BEEN CLEAR THE LAST FEW HOURS WITH A LIGHT TO CALM WIND. DIURNAL CU WILL POP UP THROUGHOUT THE AREA AGAIN ON SUNDAY WITH BASES IN THE 4-5KFT RANGE. ALL BUT SYR AND RME EXPECTED TO BE SCT. AT SYR AND RME BKN TO OVC STILL BUT WINDS FIELDS WEAKENING SO LESS LAKE MOISTURE. SATELLITE PICTURES SHOWING LAKE HURON MOISTURE HAS NOT BEEN EXTENDING THAT FAR INLAND AND CERTAINLY NOT CLOSE TO LAKE ONTARIO. NORTHWESTERLY WINDS AROUND 5 KTS OR LESS THIS MORNING WILL INCREASE TO 5 TO 10 KTS TODAY. THIS EVENING WINDS GO LIGHT AND VARIABLE TO CALM. FOR SUNDAY NIGHT THROUGH THURSDAY...VFR CONDITIONS OUTSIDE OF MORNING FOG /ESP AT ELM/ THROUGH THE PERIOD UNDER HIGH PRESSURE. LIFR FOG AT ELM EXPECTED FOR AT LEAST MONDAY MORNING. && .BGM WATCHES/WARNINGS/ADVISORIES... PA...FROST ADVISORY UNTIL 9 AM EDT THIS MORNING FOR PAZ038>040. NY...FROST ADVISORY UNTIL 9 AM EDT THIS MORNING FOR NYZ009-022>025- 036-037-044>046-055>057-062. && $$ SYNOPSIS...MSE NEAR TERM...MSE SHORT TERM...MSE LONG TERM...DGM AVIATION...TAC ny AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 421 AM EDT SUN SEP 16 2007 .SYNOPSIS... COLD HIGH PRESSURE WILL SLIDE OVER PA TODAY AND CONTINUE TO SLIP EAST TO SIT OVER THE EAST COAST FOR THE FIRST PART OF THE WORK WEEK...BRINGING A TASTE OF FALL TO THE REGION. LIGHT SOUTH WINDS WILL ALLOW TEMPERATURES TO MODERATE AND MOISTURE TO GRADUALLY INCREASE DURING THE WEEK...WITH NO PRECIPITATION EXPECTED. TEMPERATURES WILL CLIMB ABOVE SEASONABLE LEVELS BY MID WEEK AND LAST INTO NEXT WEEKEND. && .NEAR TERM /UNTIL 4 PM THIS AFTERNOON/... LOW CLOUD ENHANCEMENT IR PICS AND SFC OBS SHOW A WIDE AREA OF HIGH- BASED STRATO CU OVER THE NC MTNS AND PARTS OF NW PA RIGHT NOW...PRETTY MUCH RIGHT OVER THE CURRENT FROST/FREEZE AREAS. SOME CLEARING OVER WARREN COUNTY AND FAR WRN NY MAY SLIP EAST THROUGH SUNRISE...THOUGH. BUT MESONET TEMPS ARE RUNNING IN THE U30S AND L40S FOR THE MOST PART. WILL TAKE A STEP DOWN AND REDUCE/CANCEL THE CURRENT FREEZE WARNING AREA TO A FROST ADVSRY...BUT LEAVE THE REST OF THE FROST ADV AREA ALONE. IT IS JUST AN ADVISORY AFTER ALL...AND PATCHES OF CLEARING DID ALLOW KBFD TO DROP TO 34F EARLIER BEFORE THE CLOUDS MOVED IN. IT COULD STILL GET COOL ENOUGH /AGAIN/ BEFORE SUNRISE TO FROST UP. WINDS WILL TURN TO A MORE SOUTHWESTERLY DIRECTION IN THE CLOUD LAYER...AND TAKE IT AWAY. SUNSHINE WILL AGAIN ALLOW FOR MORE CELLULAR LOOKING CU IN THE AFTERNOON - RATHER THAN A SHEET OF STRATUS. WILL KEEP THE SE SUNNY. TEMPS SHOULD RISE INTO THE 60S FOR MOST OF THE AREA...BUT NEAR 70 IN THE HARRISBURG AREA...AND THE WRN HIGHLANDS COULD STAY IN THE 50S. && .SHORT TERM /4 PM THIS AFTERNOON THROUGH 6 PM MONDAY/... PROBLEMS TONIGHT ARE EXACTLY THE SAME AS RIGHT NOW. WILL THERE BE ANY CLOUDS - AND HOW COLD WILL IT GET? WILL USE BOTH CLIMATOLOGY AND GOOD OL PATTERN RECOGNITION TO HELP...AND THINK THAT THE SKIES WILL BE MUCH MORE CLEAR TONIGHT THAN EARLY THIS MORNING...AND LLVL WINDS WILL BE CALM FOR THE MOST PART AS THE HIGH AND THE MUCH DRIER AIR ALOFT WILL BE RIGHT OVER THE EASTERN HALF OF PA. GRANTED...A LIGHT SW FLOW STARTS TO DEVELOP IN THE 8H LEVEL NEAR THE TOP OF THE INVERSION LATER TONIGHT...BUT LITTLE/NO MOISTURE WILL BE UPSTREAM - AT LEAST COMPARED TO WHAT THE LAKE IS CONTRIBUTING RIGHT NOW. ALSO...THE SECOND NIGHT OF HIGH PRESSURE IS USUALLY COLDER THAN THE FIRST. WILL THEREFORE GO COLDER ON THE WHOLE TONIGHT THAN WHAT IS HAPPENING RIGHT NOW. WILL POST A WIDER FROST ADVSRY AREA AND MENTION PATCHY FROST IN ZFP TEXT AS FAR SOUTH AS GETTYSBURG/THOMASVILLE AND MEYERSDALE /BUT NOT POST ADVISORY THERE AS AREAL COVERAGE WILL NOT BE AS WIDESPREAD AS UP NORTH/. WILL ALSO POST ANOTHER FREEZE WATCH FOR POTTER AND MCKEAN COS FOR TONIGHT. && .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/... MODELS/ENSEMBLES CONTINUE TO SUPPORT DRY FCAST THRU NEXT WEEK UNDER THE INFLUENCE OF HIGH PRESSURE...WHICH WILL DOMINATE THRU THE PD. ANOMALOUS UPPER LEVEL RIDGING BUILDS OVER THE EASTERN U.S. FOR MID/LATE WEEK IN RESPONSE TO A DEEPENING WRN TROF...LEADING TO A SIGNIFICANT WARM-UP FOR THE AREA. SRLY RETURN FLOW WILL ALLOW FOR GRADUALLY INCREASING HEAT/HUMIDITY AS TEMPS CLIMB ABOVE NORMAL TUE-SAT. && .AVIATION /08Z SUNDAY THROUGH THURSDAY/... VFR AND LIGHT WINDS REPORTED ACROSS THE ENTIRE REGION AS OF 05Z. LAKE EFFECT STRATOCU ACROSS THE NW MTNS SHOULD DISSIPATE AND SHIFT NORTH OF THE NY BORDER BY DAWN. CALM WIND AND COLD AM TEMPS WILL ALMOST CERTAINLY LEAD TO TYPICAL DENDRITIC PATTERN OF DENSE FOG IN THE DEEP RIVER VALLEYS OF THE ALLEGHENIES FOR SEVERAL HOURS ARND DAWN. AMONG CENTRAL PA/S TERMINAL SITES...IPT APPEARS THE MOST SUSCEPTIBLE TO A PERIOD OF FOG NR DAWN...DUE TO PROXIMITY TO SUSQ RIVER. CONDITIONAL CLIMATOLOGY AND LATEST RUC RH DATA ALSO SUGGEST A GOOD CHC FOR A PERIOD OF FOG AT BFD AND JST...MAINLY BTWN 10-13Z. DOMINANT HIGH PRESSURE OVER THE NORTHEASTERN US WILL CONTINUE THROUGH MIDWEEK WITH GENLY VFR CONDS AND LIGHT WINDS. IFR CONDS IN ERY MRNG VLY AND GNFG APPEAR LIKELY THROUGH EARLY WEEK...THEN LESS LIKELY BY LATE WEEK DUE TO MILDER AM TEMPS. && .CTP WATCHES/WARNINGS/ADVISORIES... FROST ADVISORY UNTIL 9 AM EDT THIS MORNING FOR PAZ004>006- 010>012-037-041-042. FREEZE WATCH FROM LATE TONIGHT THROUGH MONDAY MORNING FOR PAZ005-006. FROST ADVISORY FROM 2 AM TO 9 AM EDT MONDAY FOR PAZ004-010>012- 017-018-037-041-042-045-046-049>053-058. && $$ SYNOPSIS...DANGELO NEAR TERM...DANGELO SHORT TERM...DANGELO/DEVOIR LONG TERM...STEINBUGL AVIATION...FITZGERALD pa AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 141 AM EDT SUN SEP 16 2007 .SYNOPSIS... COLD HIGH PRESSURE...CENTERED OVER NORTHERN INDIANA...WILL DOMINATE OUR WEATHER FOR THE REST OF THE WEEKEND...BRINGING A TASTE OF FALL TO THE REGION. THE HIGH PRESSURE AREA WILL SLOWLY SLIP EASTWARD AND OFF THE NORTHEAST U.S. COAST DURING THE WORK WEEK ALLOWING TEMPERATURES MODERATE AND MOISTURE TO GRADUALLY INCREASE. TEMPERATURES WILL CLIMB ABOVE SEASONABLE LEVELS FROM MID WEEK INTO NEXT WEEKEND. && .NEAR TERM /UNTIL 8 AM THIS MORNING/... SLOWLY DECREASING SCT-BKN STRATO CU DECK WAS NOTED ON REGIONAL 3.9 UM SATELLITE IMAGERY. LOCATION OF THE SFC-850 HPA HIGH PRESSURE RIDGE TO OUR WEST WILL ALLOW FOR A LIGHT NW BREEZE THROUGH ABOUT 06-09Z BEFORE A POSSIBLE DROP TO NEAR CALM FOR A FEW HRS AROUND DAYBREAK. HOURLY TEMPS ARE RUNNING VERY CLOSE TO SHORT TERM ENSEMBLE MOS AND FORECAST MIN TEMPS ARE PATTERNED CLOSE TO THIS GUIDANCE. LARGE 20-25F AIR WATER TEMP SPREAD LATE TONIGHT WILL BE CONDUCIVE FOR VALLEY FOG FORMATION...ESPECIALLY IF THE LIGHT NNW BREEZE TAILS OFF SOONER THAN ANTICIPATED. PATCHY 1/2SM VALLEY FOG HAS BEEN PAINTED IN OUR WEB GRIDS AND INCLUDED IN THE ZONE TEXT FOR THE EVENING UPDATE. CURRENT FREEZE WARNING/FROST ADVISORY CONFIGURATION FOR LATE TONIGHT/EARLY SUNDAY LOOKS IN GOOD SHAPE. SLIGHTLY MORE IN THE WAY OF FROST /AND FREEZING CONDITIONS ACROSS THE NRN MTNS/ IS LIKELY LATE SUNDAY NIGHT AS THE CENTER OF HIGH PRESSURE DRIFTS OVERHEAD. && .SHORT TERM /8 AM THIS MORNING THROUGH 6 PM MONDAY/... OVERNIGHT EXPECT SCATTERED LAKE EFFECT CLOUDS AT WORST TO CONTINUE TO THIN AS THE LAKE HURON CONNECTION IS LOSS AND FAVORABLE FETCH DECREASES ALONG WITH THE BOUNDARY LAYER WINDS. MAINLY CLEAR SKIES WILL PERSIST INTO SUNDAY MORNING PATCHY RADIATIONAL RIVER VALLEY FOG. EXPECT SCATTERED CU TO ONCE AGAIN DEVELOP BY MID SUNDAY MORNING BUT WILL BE MORE SOLIDLY CAPPED AS INVERSION HEIGHTS REMAIN AROUND 800 MB...WHICH WILL HAVE DRIED SUBSTANTIALLY BY 12Z SUN. A SUNNY AFTERNOON EXPECTED FOR ALL...WITH EARLY AUTUMN LIKE TEMPERATURES AND LIGHTER WINDS MAKING FOR A VERY PLEASANT AFTERNOON. && .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/... ANOTHER CHILLY NIGHT IN STORE SUNDAY NIGHT INTO EARLY MONDAY WITH TEMPS IN THE MID TO UPPER 30S OVER A GOOD PORTION OF CENTRAL PA. HAVE CONTINUED MENTION OF AREAS/PATCHY FROST...AND MAY NEED TO ISSUE ADDITIONAL FROST/FREEZE PRODUCTS DEPENDING ON HOW COLD WE GET TNT. MOS NUMBERS LOOK SLIGHTLY COLDER FOR THE CENTRAL/EASTERN ZONES TOMORROW NIGHT...WHICH LINES UP BEST WITH THE ANOMALOUS PW/S. MODELS/ENSEMBLES CONTINUE TO SUPPORT DRY FCAST THRU NEXT WEEK UNDER THE INFLUENCE OF HIGH PRESSURE...WHICH WILL DOMINATE THRU THE PD. ANOMALOUS UPPER LEVEL RIDGING BUILDS OVER THE EASTERN U.S. FOR MID/LATE WEEK IN RESPONSE TO A DEEPENING WRN TROF...LEADING TO A SIGNIFICANT WARM-UP FOR THE AREA. SRLY RETURN FLOW WILL ALLOW FOR GRADUALLY INCREASING HEAT/HUMIDITY AS TEMPS CLIMB ABOVE NORMAL TUE-SAT. && .AVIATION /05Z SUNDAY THROUGH THURSDAY/... VFR AND LIGHT WINDS REPORTED ACROSS THE ENTIRE REGION AS OF 05Z. LAKE EFFECT STRATOCU ACROSS THE NW MTNS SHOULD DISSIPATE AND SHIFT NORTH OF THE NY BORDER BY DAWN. CALM WIND AND COLD AM TEMPS WILL ALMOST CERTAINLY LEAD TO TYPICAL DENDRITIC PATTERN OF DENSE FOG IN THE DEEP RIVER VALLEYS OF THE ALLEGHENIES FOR SEVERAL HOURS ARND DAWN. AMONG CENTRAL PA/S TERMINAL SITES...IPT APPEARS THE MOST SUSCEPTIBLE TO A PERIOD OF FOG NR DAWN...DUE TO PROXIMITY TO SUSQ RIVER. CONDITIONAL CLIMATOLOGY AND LATEST RUC RH DATA ALSO SUGGEST A GOOD CHC FOR A PERIOD OF FOG AT BFD AND JST...MAINLY BTWN 10-13Z. DOMINANT HIGH PRESSURE OVER THE NORTHEASTERN US WILL CONTINUE THROUGH MIDWEEK WITH GENLY VFR CONDS AND LIGHT WINDS. IFR CONDS IN ERY MRNG VLY AND GNFG APPEAR LIKELY THROUGH EARLY WEEK...THEN LESS LIKELY BY LATE WEEK DUE TO MILDER AM TEMPS. && .CTP WATCHES/WARNINGS/ADVISORIES... FREEZE WARNING UNTIL 9 AM EDT THIS MORNING FOR PAZ005-006. FROST ADVISORY UNTIL 9 AM EDT THIS MORNING FOR PAZ004-010>012- 037-041-042. && $$ SYNOPSIS...LAMBERT NEAR TERM...LAMBERT SHORT TERM...DEVOIR LONG TERM...STEINBUGL AVIATION...FITZGERALD pa AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LINCOLN IL 1045 AM CDT SUN SEP 16 2007 .DISCUSSION... ISSUED 1044 AM CDT SUN SEP 16 2007 VORTMAX EASILY VISIBLE EMBEDDED IN MID-LEVEL CLOUD FIELD OVER SOUTHERN ILLINOIS... MOVING SOUTHEASTWARD TOWARDS THE OHIO RIVER VALLEY. CLOUDS RAPIDLY DISSIPATING NORTH AND WEST OF I-72... AND MORE SLOWLY FURTHER SOUTHEAST. SUBSIDENCE AREA SHOULD MIGRATE SE AS THE UPPER VORTMAX SLIDES OUT... SO STILL EXPECT AN OVERALL CLOUD COVER DECREASE ACROSS THE ENTIRE CWA. EITHER WAY... MOST SUNSHINE SHOULD BE SEEN ACROSS THE WESTERN HALF OF THE AREA. WILL FRESHEN UP CLOUD COVER TRENDS AND MAKE SLIGHT DOWNWARD ADJUSTMENTS IN MAX TEMP ACROSS THE EASTERN HALF OF THE AREA. UPDATED PRODUCTS SHOULD BE OUT BY 11 AM. HARDIMAN && .AVIATION... ISSUED 640 AM CDT SUN SEP 16 2007 VFR CONDITIONS SHOULD PREVAIL THROUGH 12Z/MON ACROSS THE FIVE CENTRAL IL TAF SITES. SHORT WAVE OVER CENTRAL IL WILL MOVE SE INTO KY BY EARLY AFTERNOON/18Z. WIDELY SCATTERED LIGHT SHOWERS SE OF I-55 WILL DIMINISH THROUGH 14Z WITH JUST VCSH ALONG I-72 TAF SITES NEXT HOUR OR TWO. 4 TO 8 KFT BROKEN TO OVERCAST CLOUD DECK TODAY THOUGH I-74 TAF SITES AT BMI AND CMI ARE ON EDGE OF THIS DECK AND MAY BE SCATTERED AT TIMES TODAY. RUC/NAM 800 MB RH USED FOR DECREASING CLOUDS TO SCATTERED BETWEEN 20Z AND 24Z THIS AFTERNOON. COULD BE A LIGHT FOG AT PIA LATE TONIGHT AFTER 09Z AND JUST HAVE 5SM BR. HUETTL && .PREV DISCUSSION... ISSUED 330 AM CDT SUN SEP 16 2007 00Z SHORT RANGE MODELS IN GOOD AGREEMENT THROUGH TUE AND FOLLOWED ALONG WITH SIMILAR GUIDANCE TEMPS. SHORT WAVE AND ASSOCIATED WARM AIR ADVECTION PATTERN EXITING CENTRAL IL/MID MS VALLEY BY MID MORNING ALONG WITH WIDELY SCATTERED LIGHT SHOWERS. FORECAST CONCERN IS WHEN CLOUDS WILL CLEAR TODAY OR TONIGHT. OTHERWISE BIG WARM UP STILL IN STORE FOR CENTRAL/SE IL THROUGH TUE AS SURFACE HIGH PRESSURE OVER WV DRIFTS INTO NEW ENGLAND BY TONIGHT AND MON WHILE STRONG UPPER LEVEL RIDGE BUILDS INTO IL AND THE EASTERN STATES BY EARLY WORK WEEK. STILL SOME QUESTION AS TO WHETHER CONVECTION CHANCES RETURN TO CENTRAL IL WED WITH EXTENDED MODELS DIFFERING ON HOW FAR SOUTH FRONT GETS WITH STRONG UPPER LEVEL RIDGE OVER THE EASTERN U.S. SHORT TERM...TODAY THROUGH TUESDAY... 0830Z/330 AM RADAR MOSAIC SHOWS WIDELY SCATTERED LIGHT SHOWERS OVER CENTRAL AND SOUTHERN IL ALONG AND SOUTH OF A MACOMB TO LAFETTE IN LINE AND MOVING ESE. ISOLATED THUNDERSTORMS NOTED OVER SOUTHERN IL SOUTH OF I-64/MOUNT VERNON AND THESE TO STAY SOUTH OF ILX CWFA. SHORT WAVE OVER WEST CENTRAL IL AND WARM AIR ADVECTION PATTERN AHEAD OF THIS FEATURE CAUSING WIDELY SCATTERED CONVECTION DURING PAST 6 HOURS OR SO. CLOUD DECK OF 5 TO 10 KFT FROM CENTRAL IL UPSTREAM ACORSS CENTRAL AND EASTERN IA/MO. SHORT WAVE IS WEAKENING AS ITS ZIPPING ESE INTO CENTRAL IL AT PREDAWN. SURFACE MAP SHOWS LARGE 1026 MB HIGH PRESSURE OVER WV AND RIDGING ACROSS THE SOUTHERN GREAT LAKES AND OHIO VALLEY WHILE FRONTAL BOUNDARY WAS NEAR THE GULF COAST AND ARCHING UP THE HIGH PLAINS. MILDER TEMPS OF 50 TO 55 OVER CENTRAL IL WHILE DEWPOINTS IN THE LOW TO MID 40S. MODELS TAKE SHORT WAVE FROM WEST CENTRAL IL INTO KY BY NOON ENDING WIDELY SCATTERED LIGHT SHOWERS OVER CENTRAL IL SOUTH OF PEORIA BY MID MORNING. SHOULD SEE CLOUDS DECREASE THIS AFTERNOON WITH SKIES BECOMING PARTLY SUNNY WITH SOME DRYING IN WAKE OF SHORT WAVE PER MODEL LAYERED RH FIELD. HIGHS 70 TO 75F BUT WILL BE COOLER IF CLOUDS STICK AROUND LONGER IN THE AFTERNOON. INCREASING SOUTHERLY FLOW MON AS HIGH PRESSURE DRIFTS OVER NEW ENGLAND AND STRONG LOW PRESSURE MOVING INTO THE NORTHERN PLAINS. UPPER LEVEL RIDGE BUILDING INTO IL. WARMER HIGHS IN THE LOW TO MID 80S WITH PARTLY TO MOSTLY SUNNY SKIES. EVEN WARMER TUE WITH HIGHS IN THE UPPER 80S TO NEAR 90F WITH MOSTLY SUNNY SKIES AND BREEZY SSW WINDS. LONG TERM...TUESDAY NIGHT THROUGH FRIDAY... KEPT TUE EVENING DRY OVER IL RIVER VALLEY WITH SLIGHT CHANCE OF CONVECTION AFTER MIDNIGHT TUE NIGHT NW OF THE IL RIVER AS FRONTAL BOUNDARY APPROACHES NW IL WED MORNING. GFS MAY BE A BIG TOO QUICK WITH FRONT CONSIDERING STRONG UPPER LEVEL RIDGE ANCHORED ACROSS MUCH OF THE EASTERN U.S. CONTINUE 20 TO 30% CHANCE OF CONVECTION FROM I-55 NW AS FRONT MOVES INTO NW IL WHILE STAYING DRY SE OF I-55 WITH MORE SUNSHINE POSSIBLE IN EASTERN IL. LOW PRESSURE EJECTING NE FROM EASTERN CO AND DEEPENING INTO THE NORTHERN PLAINS THU TO LIFT FRONT BACK NORTH OF IL. THIS TO KEEP CENTRAL IL DRY THU/FRI WITH CONTINUED SUMMERTIME WARMTH WITH HIGHS WELL INTO THE 80S. SO LAST WEEK OF SUMMER LOOKS TO BE VERY WARM AND ON THE DRY SIDE ACROSS CENTRAL/SE IL. HUETTL && .ILX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ il AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LINCOLN IL 653 AM CDT SUN SEP 16 2007 .DISCUSSION... ISSUED 330 AM CDT SUN SEP 16 2007 00Z SHORT RANGE MODELS IN GOOD AGREEMENT THROUGH TUE AND FOLLOWED ALONG WITH SIMILAR GUIDANCE TEMPS. SHORT WAVE AND ASSOCIATED WARM AIR ADVECTION PATTERN EXITING CENTRAL IL/MID MS VALLEY BY MID MORNING ALONG WITH WIDELY SCATTERED LIGHT SHOWERS. FORECAST CONCERN IS WHEN CLOUDS WILL CLEAR TODAY OR TONIGHT. OTHERWISE BIG WARM UP STILL IN STORE FOR CENTRAL/SE IL THROUGH TUE AS SURFACE HIGH PRESSURE OVER WV DRIFTS INTO NEW ENGLAND BY TONIGHT AND MON WHILE STRONG UPPER LEVEL RIDGE BUILDS INTO IL AND THE EASTERN STATES BY EARLY WORK WEEK. STILL SOME QUESTION AS TO WHETHER CONVECTION CHANCES RETURN TO CENTRAL IL WED WITH EXTENDED MODELS DIFFERING ON HOW FAR SOUTH FRONT GETS WITH STRONG UPPER LEVEL RIDGE OVER THE EASTERN U.S. SHORT TERM...TODAY THROUGH TUESDAY... 0830Z/330 AM RADAR MOSAIC SHOWS WIDELY SCATTERED LIGHT SHOWERS OVER CENTRAL AND SOUTHERN IL ALONG AND SOUTH OF A MACOMB TO LAFETTE IN LINE AND MOVING ESE. ISOLATED THUNDERSTORMS NOTED OVER SOUTHERN IL SOUTH OF I-64/MOUNT VERNON AND THESE TO STAY SOUTH OF ILX CWFA. SHORT WAVE OVER WEST CENTRAL IL AND WARM AIR ADVECTION PATTERN AHEAD OF THIS FEATURE CAUSING WIDELY SCATTERED CONVECTION DURING PAST 6 HOURS OR SO. CLOUD DECK OF 5 TO 10 KFT FROM CENTRAL IL UPSTREAM ACORSS CENTRAL AND EASTERN IA/MO. SHORT WAVE IS WEAKENING AS ITS ZIPPING ESE INTO CENTRAL IL AT PREDAWN. SURFACE MAP SHOWS LARGE 1026 MB HIGH PRESSURE OVER WV AND RIDGING ACROSS THE SOUTHERN GREAT LAKES AND OHIO VALLEY WHILE FRONTAL BOUNDARY WAS NEAR THE GULF COAST AND ARCHING UP THE HIGH PLAINS. MILDER TEMPS OF 50 TO 55 OVER CENTRAL IL WHILE DEWPOINTS IN THE LOW TO MID 40S. MODELS TAKE SHORT WAVE FROM WEST CENTRAL IL INTO KY BY NOON ENDING WIDELY SCATTERED LIGHT SHOWERS OVER CENTRAL IL SOUTH OF PEORIA BY MID MORNING. SHOULD SEE CLOUDS DECREASE THIS AFTERNOON WITH SKIES BECOMING PARTLY SUNNY WITH SOME DRYING IN WAKE OF SHORT WAVE PER MODEL LAYERED RH FIELD. HIGHS 70 TO 75F BUT WILL BE COOLER IF CLOUDS STICK AROUND LONGER IN THE AFTERNOON. INCREASING SOUTHERLY FLOW MON AS HIGH PRESSURE DRIFTS OVER NEW ENGLAND AND STRONG LOW PRESSURE MOVING INTO THE NORTHERN PLAINS. UPPER LEVEL RIDGE BUILDING INTO IL. WARMER HIGHS IN THE LOW TO MID 80S WITH PARTLY TO MOSTLY SUNNY SKIES. EVEN WARMER TUE WITH HIGHS IN THE UPPER 80S TO NEAR 90F WITH MOSTLY SUNNY SKIES AND BREEZY SSW WINDS. LONG TERM...TUESDAY NIGHT THROUGH FRIDAY... KEPT TUE EVENING DRY OVER IL RIVER VALLEY WITH SLIGHT CHANCE OF CONVECTION AFTER MIDNIGHT TUE NIGHT NW OF THE IL RIVER AS FRONTAL BOUNDARY APPROACHES NW IL WED MORNING. GFS MAY BE A BIG TOO QUICK WITH FRONT CONSIDERING STRONG UPPER LEVEL RIDGE ANCHORED ACROSS MUCH OF THE EASTERN U.S. CONTINUE 20 TO 30% CHANCE OF CONVECTION FROM I-55 NW AS FRONT MOVES INTO NW IL WHILE STAYING DRY SE OF I-55 WITH MORE SUNSHINE POSSIBLE IN EASTERN IL. LOW PRESSURE EJECTING NE FROM EASTERN CO AND DEEPENING INTO THE NORTHERN PLAINS THU TO LIFT FRONT BACK NORTH OF IL. THIS TO KEEP CENTRAL IL DRY THU/FRI WITH CONTINUED SUMMERTIME WARMTH WITH HIGHS WELL INTO THE 80S. SO LAST WEEK OF SUMMER LOOKS TO BE VERY WARM AND ON THE DRY SIDE ACROSS CENTRAL/SE IL. && .AVIATION... ISSUED 640 AM CDT SUN SEP 16 2007 VFR CONDITIONS SHOULD PREVAIL THROUGH 12Z/MON ACROSS THE FIVE CENTRAL IL TAF SITES. SHORT WAVE OVER CENTRAL IL WILL MOVE SE INTO KY BY EARLY AFTERNOON/18Z. WIDELY SCATTERED LIGHT SHOWERS SE OF I-55 WILL DIMINISH THROUGH 14Z WITH JUST VCSH ALONG I-72 TAF SITES NEXT HOUR OR TWO. 4 TO 8 KFT BROKEN TO OVERCAST CLOUD DECK TODAY THOUGH I-74 TAF SITES AT BMI AND CMI ARE ON EDGE OF THIS DECK AND MAY BE SCATTERED AT TIMES TODAY. RUC/NAM 800 MB RH USED FOR DECREASING CLOUDS TO SCATTERED BETWEEN 20Z AND 24Z THIS AFTERNOON. COULD BE A LIGHT FOG AT PIA LATE TONIGHT AFTER 09Z AND JUST HAVE 5SM BR. HUETTL && .ILX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ il AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN 632 AM CDT SUN SEP 16 2007 .UPDATE...FOR 12Z AVIATION DISCUSSION BELOW && .DISCUSSION.../ISSUED 404 AM CDT SUN SEP 16 2007/ OVERCAST LOW/MID LEVEL CLOUDS COVERING THE EASTERN TWO-THIRDS OF THE CWA EARLY THIS MORNING. BACK EDGE RUNS FROM KSTC TO KULM WITH AN EASTWARD MOVEMENT AROUND 17 KNOTS. EXPECT THE CLOUDS TO BREAK UP SOME DURING THE MORNING AS THEY MOVE EAST WITH SKIES BECOMING PARTLY TO MOSTLY SUNNY. STRATUS HAS POPPED UP OVER EASTERN NEBRASKA WITH A MOVEMENT TO THE NORTH. RUC 925MB PROGS SHOW THIS EXPANDING RAPIDLY NORTHEAST THIS MORNING BEFORE DIMINISHING OVER EAST CENTRAL MN EARLY THIS AFTERNOON. WILL ALLOW FOR SOME OF THE STRATUS MAKING IT INTO SOUTH CENTRAL MN THIS MORNING. GFS 300K THETA SURFACE SHOWS THAT THE STRATUS WILL BE ONE OF OUR PROBLEMS DEVELOPING TONIGHT WITH SATURATION SETTING IN. OVERALL...STILL PREFER THE 16/00Z GFS OVER THE NAM. USED THE GFS 24 HOURS AGO AND CONTINUED WITH THAT TREND THIS MORNING. THE MAIN PROBLEM WITH THE 16/00Z NAM IS THE DEEPENING SURFACE LOW OVER MN ON TUESDAY. THE 16/00Z ECMWF...WHICH 24 HOURS AGO WAS A COMPROMISE BETWEEN THE NAM AND GFS...IS NOW MORE IN LINE WITH THE GFS. DO THINK THERE WILL BE A WAVE MOVING NORTHEAST ALONG THE FRONT ON TUESDAY BUT JUST NOT THE DEPTH SHOWN BY THE NAM. AFTER SOME SUNSHINE TODAY...MOISTURE AND INSTABILITY WILL BE ON THE INCREASE ACROSS THE WESTERN AND SOUTHERN CWA TONIGHT. ADDED POPS TO THESE AREAS. THINGS BECOME PRETTY UNSTABLE SUNDAY NIGHT AND I WOULDN`T BE SURPRISED IF A SEVERE STORM OR TWO DEVELOPED BY MONDAY MORNING DUE TO THE INTENSE LOW LEVEL THETA-E ADVECTION AND 30 KNOT WINDS 1500 FEET ABOVE THE GROUND. MONDAY STILL LOOKS BAD FOR SOUTHERN MN IN THE AFTERNOON AND EVENING FOR SURFACE BASED CONVECTION AND POSSIBLE TORNADOES. WILL CONTINUE TO MENTION THE CHANCE FOR TORNADOES IN THE HWO THIS MORNING. A WARM FRONT IS SHOWN TO MAKE IT TO NEAR THE MN RIVER BY MONDAY EVENING. SURFACE DEW POINTS IN THE 60 TO 65 DEGREE RANGE EXPECTED. 6 HOUR PRESSURE FALLS OF 4 MILLIBARS ARE CENTERED NEAR MANKATO. 0-1KM SHEAR IS 30-35 KNOTS WITH 0-6KM SHEAR NEAR 50 KNOTS. 40 KNOT WINDS AT 850MB POKE ALL THE WAY INTO KMSP. THE NAM SHOWS A SIMILAR SCENARIO BUT EVEN WORSE. ELEVATED SEVERE STORMS WILL BE POSSIBLE ON MONDAY TO THE NORTH OF THE WARM FRONT. THE ACTION DOESN`T STOP. ALTHOUGH THE WARM FRONT LIFTS NORTH OF THE AREA MONDAY NIGHT...A COLD FRONT WILL SLOWLY MOVE INTO THE MN CWA ON TUESDAY. MORE CONVECTION IS LIKELY...ESPECIALLY TUESDAY AFTERNOON AND EVENING OVER THE EASTERN CWA AS THE AIRMASS DESTABILIZES. STILL BELIEVE WE WILL HAVE A BREAK ON WEDNESDAY. ANOTHER WAVE OF LOW PRESSURE SHOWN TO APPROACH FROM THE WSW THURSDAY AND FRIDAY. THIS WILL PUSH A WARM FRONT NORTH THROUGH THE AREA WITH MORE SHOWERS AND THUNDERSTORMS. HIGHS/LOWS FOR THE NEXT 72 HOURS NEAR MAV VALUES. && .AVIATION.../12Z TAF ISSUANCE/ OVERCAST DECK CIRCA 5K-6K FEET WILL CONTINUE EXITING TO THE EAST...CLEARING KMSP SHORTLY AFTER DAYBREAK...KRNH BETWEEN 14Z AND 15Z...AND KEAU AROUND THE NOON HOUR. NEXT CONCERN IS STRATUS DECK THAT DEVELOPED OVERNIGHT OVER EASTERN NE...AND IS BEGINNING TO BLOSSOM ACROSS EXTREME SOUTHWESTERN MINNESOTA. WHILE THERE SHOULD BE SOME REDUCTION IN THE EXPANSION OF THE DECK ONCE THE SUN RISES...THINK THAT KRWF MAY SEE A PERIOD OF IFR CEILINGS THIS MORNING...WHICH IS SUPPORTED BY THE 925MB RUC RELATIVE HUMIDITY PROGS. OTHERWISE...SOUTHERLY FLOW WILL PREVAIL AGAIN TODAY...ALTHOUGH LOOSER GRADIENT TODAY SHOULD KEEP MAX SPEEDS AT OR BELOW 15 KNOTS. STRATUS DEVELOPMENT APPEARS POSSIBLE AFTER 06Z TONIGHT...AS A WARM FRONT LIFTS INTO SOUTHWESTERN MINNESOTA. ADDITIONALLY...ELEVATED INSTABILITY APPEARS TO INCREASE NORTH OF THE WARM FRONT OVERNIGHT...SO SHRA/TS MAY NEED TO BE ADDED IN FUTURE ISSUANCES. && .MPX WATCHES/WARNINGS/ADVISORIES... MN...NONE. WI...NONE. && $$ RAH/LS mn AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE GRAND FORKS ND 956 AM CDT SUN SEP 16 2007 .UPDATE...SOUTHERLY FLOW WILL CONTINUE TODAY AS LOW PRESSURE ORGANIZES ACROSS THE N ROCKIES. CONVECTIVE TEMPS NEAR 100F...SO MOSTLY CLEAR SKIES A GOOD BET. THERE IS A POCKET OF LOW CLOUDS JUST SOUTH OF THE FA. LATEST SATELLITE IMAGERY WOULD INDICATE THESE CLOUDS HALTING THEIR NORTHWARD MOVEMENT...AND DISSIPATING FROM THE EDGES. TAMDAR SOUNDING FROM KFSD SHOWS A SHALLOW CLOUD LAYER...TO 900MB. 12Z NAM/RUC INDICATES THESE CLOUDS TO REMAIN SOUTH TODAY. THIS MAKES SENSE CONSIDERING SHALLOW CLOUD LAYER AND WARM AIR ADVECTION ONGOING TODAY...WILL STICK WITH CURRENT FORECAST OF NO CLOUDS. THUS...FORECAST IN EXCELLENT SHAPE AND NO UPDATE PLANNED. && .AVIATION...VFR TO CONTINUE WITH WINDS UP TO 15 KTS FOR TODAY. && .PREV DISCUSSION... /ISSUED 415 AM CDT SUN SEP 16 2007/ DISCUSSION...MAIN FORECAST CHALLENGE IS PRECIPITATION. WHEN LOOKING AT THE CURRENT SURFACE ANALYSIS...THE AREA IS BETWEEN WEATHER SYSTEMS..WITH LOW PRESSURE TO THE W AND HIGH PRESSURE TO THE E. WHEN COMPARING MODELS...THE GFS WAS PREFERRED DUE TO ITS BETTER TRACK RECORD OF LATE...BUT A COMPROMISE WITH THE NAM WAS UTILIZED FOR LATER IN THE FORECAST IN ORDER TO PROVIDE BETTER CONTINUITY. A LOW PRESSURE SYSTEM MOVES OUT OF THE ROCKIES INTO THE N PLAINS TONIGHT. AHEAD OF THE LOW...GOOD 850MB WAA AND A S WIND FLOW WILL PROVIDE WARMER TEMPERATURE AND A RETURN OF MOISTURE TO THE AREA TODAY. THE ATMOSPHERE DESTABILIZES TONIGHT AS AN UPPER LEVEL SHORTWAVE MOVES THROUGH. WITH SHOWALTERS FALLING TO -6 IN CONJUNCTION WITH GOOD 700MB LIFT AND 850MB Q-VECTOR CONVERGENCE...COULD SEE ELEVATED CONVECTION DEVELOP ON NOSE OF THETA-E GRADIENT IN E ND IN CONJUNCTION WITH 30KT LOW LEVEL JET. THEREFORE...ADDED ISOLATED THUNDERSTORMS TO THE FORECAST FOR PART OF E ND AFTER MIDNIGHT. AS THE LOW MOVES THROUGH ND AND SD ON MON...WILL SEE ADDITIONAL THUNDERSTORM DEVELOPMENT OVER THE AREA...WITH THE FOCUS APPEARING TO BE MAINLY SE ND AND WC MN AT THIS TIME. AS A RESULT...INCREASED POPS TO LIKELY FOR MAINLY WC MN INTO MON NIGHT AND TUE. SOME WRAP-AROUND PRECIP REMAINS POSSIBLE INTO TUE NIGHT...WITH A BRIEF BREAK BETWEEN SYSTEMS ON WED. WHEN LOOKING INTO THE EXTENDED FORECAST...ANOTHER LOW PRESSURE SYSTEM MOVES OUT INTO THE N PLAINS FOR THU AND FRI. WITH GOOD CONTINUITY REMAINING IN EXTENDED FORECAST...MINIMAL CHANGES NEEDED. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...NONE. MN...NONE. && $$ TG nd AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA NATIONAL WEATHER SERVICE SIOUX FALLS SD 1003 AM CDT SUN SEP 15 2007 .DISCUSSION... STRATUS HAS EXPANDED TO COVER A LARGE PORTION OF THE CWA...BUT IS BEGINNING TO SHOW HINTS OF DETERIORATION AROUND THE EDGES...ESPECIALLY ON THE SOUTHEAST SIDE. EXPECT THIS TREND TO CONTINUE AS GOOD WARMING OCCURS WHERE THE CLOUDS ARE NOT...WHICH WILL CONTINUE TO ERODE STRATUS. LOOKS LIKE THE I29 CORRIDOR/BIG SIOUX RIVER VALLEY WILL BE ABOUT THE LAST TO GO...SO WILL MAINTAIN CLOUDS LONGEST IN THESE LOCATIONS. NAM/GFS HAVE NO CLUE TO THE EXISTENCE OF THIS STRATUS...SO HAVE HAD TO RELY ON INFORMATION FROM THE RUC. OTHERWISE...SLOWED DOWN WARMING UNDER THE STRATUS...BUT WITH THE EXPECTED DETERIORATION OF STRATUS...FORECAST HIGHS SHOULD BE PRETTY CLOSE WITH MIXING TO ONLY ABOUT 900MB UNDER INFLUENCE OF STRONG INVERSION. FOR TONIGHT...JET STREAK PER WATER VAPOR WORKING INTO NV/UT WILL SPREAD NORTHEAST TOWARDS WESTERN SD. THIS SHOULD AID IN PRECIPITATION DEVELOPMENT OVER THE WESTERN HIGH PLAINS LATE THIS AFTERNOON AND THIS EVENING...WHICH SHOULD THEN WORK INTO CENTRAL AND WESTERN SD LATE TONIGHT AND MONDAY MORNING. A VERY NICE RIGHT REAR QUAD PER GFS AND NAM WILL LIKELY INTERACT WITH THE 700-600MB FRONT AS ANYTHING BELOW THIS PER BUFKIT SOUNDINGS AND 12Z LBF SOUNDING ARE MUCH TOO DRY. SO...MAY DECREASE POPS IN THE EAST FOR LATE TONIGHT AND INCREASE A BIT SOUTHWEST OF A 9V9 TO TYNDALL LINE. JET STREAK/MID LEVEL FRONT INTERACTION REALLY GETS GOING ON MONDAY MORNING AND WOULD EXPECT RAIN AND ISOLATED THUNDERSTORMS WEST OF INTERSTATE 29 WITH A STRONG POSITIVE/NEGATIVE FRONTOGENESIS COUPLET. 08 && .AVIATION... IFR AND LIFR CIGS AT FSD SHOULD LIFT BY ABOUT 17Z. VFR CONDITIONS AFTER THIS FOR ALL SITES. && .PREV DISCUSSION... TRICKY FORECAST FORTHCOMING WITH MORE ACTIVE PATTERN SETTING UP. CURRENT OBSERVATIONS SUGGEST A BATCH OF STRATUS OVER NORTH CENTRAL NEBRASKA SLIDING OFF TO THE NORTH NORTHEAST AT 15 KNOTS. CURRENT PROJECTIONS SHOW IT REACHING THE I-90 CORRIDOR RIGHT AROUND 12Z. FEEL IT WILL GRADUALLY LIFT AND DISSIPATE THROUGH THE MORNING HOURS....BUT WITH ELEVATED INVERSION IT MAY TAKE ITS TIME DOING SO. TEMPERATURES TODAY ARE SOMEWHAT TRICKY TODAY...BUT HAVE KEPT TEMPERATURES IN THE EAST SLIGHTLY COOLER BASED ON AFOREMENTIONED CLOUD COVER AND SLIGHTLY COOLER 925 HPA TEMPS. GRADIENT INCREASES TONIGHT AHEAD OF A DEVELOPING TROUGH MOVING OUT OF THE INTERMOUNTAIN WEST. LEADING SHORTWAVE MOVES OUT OF WYOMING INTO CENTRAL SOUTH DAKOTA BY MONDAY MORNING. AHEAD OF SHORTWAVE...FAIRLY STRONG WARM AIR ADVECTION ASSOCIATED WITH 30 KNOT LOW LEVEL JET. HAVE EXPANDED PRECIP CHANCES TO INCLUDE ENTIRE CWA AFTER MIDNIGHT BASED ON FORCING...WITH THE GREATEST CHANCES CLOSER TO THE MID LEVEL WAVE. WITH THE INCREASING CLOUD COVER AND WINDS...HAVE KEPT LOWS ON THE WARMER END OF GUIDANCE. WARM FRONT EXPECTED TO LIFT NORTH ACROSS THE CWA ON MONDAY. NORTH OF THE FRONT...EXPECT STRATUS TO KEEP TEMPERATURES DOWN...WHILE SOUTH OF THE FRONT...PARTLY CLOUDY SKIES MAY DEVELOP RESULTING IN RAPID DESTABILIZATION. WITH STEEP LAPSE RATES ALOFT AND GOOD DIRECTIONAL AND SPEED SHEAR...ANY STORMS THAT DEVELOP IN THE WARM SECTOR WOULD LIKELY BE SEVERE WITH LARGE HAIL AND DAMAGING WINDS BEING THE MAIN THREAT. RIGHT NOW...CAPPING INVERSION LOOKS TO BE FAIRLY STRONG AND HAVE HELD OFF ON ANY WARM SECTOR PRECIP POTENTIAL TILL AFTER 00Z TUESDAY. FURTHER OFF TO THE NORTH... A SERIES OF SHORTWAVES LOOKS TO MOVE WITHIN THE VICINITY OF THE WARM FRONT RESULTING IN WAVES OF SHOWERS AND THUNDERSTORMS THROUGHOUT PORTIONS OF THE DAY. LOOKS LIKE THE POTENTIAL FOR A DECENT RAIN EVENT ON MONDAY NIGHT INTO TUESDAY AS SHORT WAVE TRAIN MOVES FROM SOUTHWEST TO NORTHEAST ACROSS THE AREA. HAVE ALIGNED THE HIGHEST POPS AND QPF WITHIN THE VICINITY OF THE FRONT...WHICH IS A NORTH AND WEST SHIFT FROM HPC GUIDANCE. MODELS STILL SUGGESTING FAIRLY STRONG WAVE WORKING THROUGH THE AREA TUESDAY AFTERNOON INTO EARLY EVENING AND WILL CONTINUE TO HIGHLIGHT IN THE HWO. WEDNESDAY APPEARS TO BE A FAIRLY UNEVENTFUL DAY AT THIS POINT...AS LARGE UPPER LEVEL TROUGH DIGS THANKS TO THE HELP OF A 150+ KNOT JET DIGGING ALONG THE BACKSIDE. MODELS SUGGEST THIS MAY DEVELOP INTO A CUT OFF LOW LATE IN THE WEEK. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...NONE. MN...NONE. IA...NONE. NE...NONE. && $$ BT/RSR sd AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE CORPUS CHRISTI TX 1049 AM CDT SUN SEP 16 2007 .UPDATE...12Z RUC/NAM/GFS SHOW A MID LEVEL VORTICITY MAXIMUM OVER THE COASTAL BEND DRIFTING TO THE WEST-NORTHWEST ON THE SOUTHERN PERIPHERY OF THE MID LEVEL ANTICYCLONE OVER NORTH TEXAS. A LOOP OF GOES SOUNDER PRECIPITABLE WATER SHOWS HIGHER MOISTURE ADVECTING NORTHWEST INTO THE COASTAL BEND AS THIS SHORT WAVE TROUGH SLOWLY MOVES WEST. WILL CONTINUE PREVIOUS FORECAST OF BETTER CHANCE POPS ALONG THE SOUTHERN PORTION OF THE FORECAST AREA AND RAISE POPS SLIGHTLY TO 20 PERCENT OVER THE VICTORIA CROSSROADS REGION. MADE SOME MINOR MODIFICATIONS TO THE WIND FORECAST...OTHERWISE NO MAJOR CHANGES WERE MADE. && .PREV DISCUSSION... /ISSUED 307 AM CDT SUN SEP 16 2007/ SHORT-TERM (TODAY THROUGH MONDAY)...MID LEVEL ANTICYCLONE CENTERED NEAR N CEN TX WILL DRIFT EAST TOWARD THE LOWER MS RIVER VALLEY THROUGH MONDAY. AS IT DOES A WEAK S/WV WILL MOVE ACROSS S TX...PERHAPS PROVIDING MODEST LIFT ACROSS THE AREA. SFC HIGH PRESSURE RIDGE TO THE NE WILL PROVIDE ERLY LOW LEVEL FLOW. SOME DRIER AIR WILL SNEAK INTO IN NERN COS NEAR VCT...BUT MOISTURE POOL ASSOC W/ OLD WASHED OUT FRONT OVER THE GULF WILL REMAIN ACROSS SRN AREAS WHERE PWS WILL RANGE FROM 1.8 TO NEAR 2 INCHES. THIS WILL ALL LEAD TO ISOLD TO SCT SHRAS AND POSSIBLY A FEW TSTMS W/ HIGHEST POPS SW OF FREER TO CRP LINE TODAY. APPEARS DRIER AIR WILL FILTER INTO THE REGION A BIT MORE FOR MON...BUT MOISTURE POOL REMAINS ACROSS SWRN 3RD OF THE REGION. WILL CONTINUE SIMILAR POP CONFIGURATION FOR MON (LOWEST NE-HIGHEST SW)...BUT POPS WILL BE ABOUT 10 PERCENT LOWER THAN TODAY WITH LOW END CHC POPS CONFINED TO FAR SRN/SWRN SECTIONS (NQI-LRD). MAV TEMPS GENERALLY SEEM BEST THROUGH THE PERIOD. AVIATION...SOME MVFR CONDITIONS WILL BE POSSIBLE WITH SOME LIGHT FOG ACROSS THE REGION EACH MORNING AND NEAR ISOLD TO SCT SHRA/TSRAS MAINLY FROM MID MORNING THROUGH AFTN TODAY. OTHERWISE CIGS THAT DEVELOP W/ CU/HEATING SHOULD REMAIN VFR FOR MOST PART TODAY. LONG TERM (MONDAY NIGHT THROUGH SATURDAY)...GFS/ECMWF/NAM ARE CONSISTENT LIFTING A TROUGH INTO THE NORTHERN PLAINS TUE WHICH WILL WEAKEN AND ELONGATE THE RIDGE FROM SW-NE OVER TEXAS. SUBSIDENCE ASSOCIATED WITH THIS RIDGE WILL KEEP OUR FORECAST DRY AND TEMPERATURES SLIGHTLY ABOVE NORMAL FOR THIS TIME OF YEAR. ANOTHER DEEP TROUGH DEVELOPS ON THE WEST COAST WED-FRI WHICH ANCHORS THE RIDGE OVER TEXAS THROUGH THE END OF THE WEEK. THE FORECAST GETS INTERESTING TOWARD THE WEEKEND AS THE ECMWF AND GFS BOTH SHOW A TROPICAL SYSTEM EMERGING FROM THE CARIBBEAN SEA AND INTO THE GULF OF MEXICO. BOTH MODELS BRING THE SYSTEM TOWARD THE TEXAS COAST ON SUNDAY. THE ECMWF PROGS VERY WEAK SHEAR ALOFT OVER THIS SYSTEM AND THE GFS INDICATES STRONG SHEAR. STILL TOO UNCERTAIN TO HAVE ANY CONFIDENCE THIS FAR OUT BUT WILL BE SOMETHING TO WATCH IN THE COMING DAYS FOR NEXT WEEKEND. WILL INTRODUCE 20% POPS FOR SAT TO AT LEAST ACCOUNT FOR AN INCREASE IN MOISTURE ASSOCIATED WITH TROPICAL WAVE. && .PRELIMINARY POINT TEMPS/POPS... CORPUS CHRISTI 91 73 91 74 91 / 30 20 20 10 10 VICTORIA 91 69 91 71 91 / 20 10 10 10 10 LAREDO 95 75 96 76 96 / 30 30 30 10 10 ALICE 92 72 93 72 92 / 40 20 20 10 10 ROCKPORT 90 77 90 77 91 / 20 20 10 10 10 COTULLA 93 72 94 72 94 / 20 20 20 10 10 KINGSVILLE 91 73 91 73 92 / 40 30 30 10 10 NAVY CORPUS 91 77 89 77 88 / 30 20 20 10 10 && .CRP WATCHES/WARNINGS/ADVISORIES... TX...NONE. GM...NONE. && $$ TMT/89...SHORT TERM tx AREA FORECAST DISCUSSION FOR THE FLORIDA KEYS NATIONAL WEATHER SERVICE KEY WEST FL 357 PM EDT SUN SEP 16 2007 .DISCUSSION... OBSERVATIONS/TRENDS -- THE MEAN LOWER-TROPOSPHERIC WIND HAS SLIGHTLY VEERED AND FRESHENED DURING THE LAST 24 HOURS...NOW AVERAGING ABOUT 075/10KT...ACCORDING TO RECENT OBSERVATIONS FROM THE NOAA ENVIRONMENTAL TECHNOLOGY LABORATORY PROFILER ON CUDJOE KEY. A BRIEF LOWER KEYS CUMULUS LINE EPISODE A FEW HOURS AGO WAS AIDED BY A NORTHWARD-MOVING OUTFLOW BOUNDARY THAT MERGED WITH AN INCIPIENT ISLAND HEATING ZONE. THE CU LINE PRODUCED A BRIEF WATERSPOUT OVER THE FLATS BETWEEN KEY HAVEN AND CHANNEL KEY...A FEW MILES NE OF KEY WEST. LATEST DOPPLER RADAR SCANS SHOW VERY FEW SHOWERS ACROSS THE SERVICE AREA. SATELLITE AND RUC SOUNDINGS INDICATE A LARGE POCKET OF DRY AIR IN THE 850-700MB LAYER MOVING WEST ACROSS THE REGION...AND THIS MAY BE CUTTING DOWN CONVECTIVE COVERAGE. AN UPPER-LEVEL COMPOSITE ANALYSIS THIS AFTERNOON REVEALS A LARGE DEEP LAYER ANTICYCLONE CENTERED OVER TEXAS WITH A RIDGE EXTENDING NORTH OVER THE GREAT PLAINS WHILE A MEAN TROUGH WAS ANALYZED OVER MUCH OF THE EASTERN SEABOARD. MEANWHILE...A TUTT CONFIGURATION IS APPARENT IN THE UPPER TROPOSPHERE OVER THE GREATER ANTILLES AND CARIBBEAN SEA... WITH A BROAD AND WEAK CYCLONIC FLOW REGIME IN THE LOWER TROPOSPHERE ACROSS THIS REGION. SEVERAL SMALLER SCALE TROUGH LINES ARE EVIDENT WITHIN THE BROAD AREA OF CYCLONIC LOW-LEVEL FLOW. FORECASTS -- TONIGHT THROUGH MONDAY NIGHT -- THE MIDLATITUDE UPPER FLOW PATTERN IS EXPECTED TO AMPLIFY NORTH OF THE KEYS WITH A STRONG MID-LEVEL VORTICITY CENTER DROPPING SOUTH OUT OF THE WESTERLIES TO NEAR CENTRAL FLORIDA. GLOBAL NUMERICAL MODELS HAVE BEEN VERY PERSISTENT INDICATING THIS SCENARIO OVER THE LAST SEVERAL DAYS. AS THIS PATTERN UNFOLDS...THE BROAD CYCLONIC LOWER-TROPOSPHERIC FLOW REGIME IN PLACE OVER THE WESTERN CARIBBEAN BASIN WILL EXPAND NORTHWARD AND SHARPEN DUE TO THE INFLUENCE OF THE MIDLATITUDE VORTICITY CENTER. AS A RESULT...INCREASING LEVELS OF AMBIENT VORTICITY AND SOME WEAK LARGE-SCALE ASCENT SHOULD BEGIN TO DEEPEN THE MOIST LAYER LOCALLY...WITH NE OR ENE FLOW PREVAILING IN THE 1000-700MB LAYER AND LOCAL CIRCULATIONS MODULATING CONVECTIVE PATTERNS. WE ARE KEEPING 12-HOUR POPS AROUND 40 PERCENT FOR TONIGHT- MONDAY NIGHT...WHICH IS ABOVE CLIMATOLOGY AND MOS. TUESDAY THROUGH SUNDAY -- THE MID-LEVEL VORTICITY CENTER INITIALLY OVER FLORIDA IS EXPECTED TO EXPAND INTO A SLOW...WESTWARD-MOVING CYCLONIC GYRE OVER THE GULF OF MEXICO. WIND FIELDS LOCALLY DO NOT APPEAR TO BE TOO STRONG...BUT MY THINKING IS THAT OUR PROXIMITY TO THIS CYCLONIC GYRE AND POSITION WITHIN LOW-LEVEL MOIST CONFLUENT FLOW SHOULD IF NOTHING ELSE DEEPEN THE MOIST LAYER FURTHER...THEREBY ENHANCING DAILY CONVECTIVE CYCLES. INTERESTINGLY...BY MIDWEEK THE GLOBAL MODELS BUILD A STRONG AND DEEP SHORT WAVE RIDGE FROM NE TO SW ON THE EASTERN FLANK OF THE CYCLONIC GYRE...PRODUCING AN UNUSUAL CONFIGURATION OF STRONG SUBSIDENCE AND DEEP SOUTHERLY FLOW ACROSS THE KEYS. THIS SETUP APPEARS VERY SUSPECT RIGHT NOW...AND WE WILL AT THIS POINT MAINTAIN THE MODESTLY-ABOVE CLIMATOLOGY 12-HOUR RAIN CHANCES OF 50 AND 40 PERCENT FOR TUESDAY-THURSDAY AND THURSDAY NIGHT-SUNDAY... RESPECTIVELY. && .MARINE... GENTLE TO MODERATE ENE BREEZES WILL PERSIST TONIGHT THROUGH TUESDAY...WITH LOCALLY HIGHER WINDS IN AND NEAR SHOWERS AND THUNDERSTORMS. NO ADVISORIES OR HEADLINES ARE ANTICIPATED. HOWEVER...BE ALERT FOR POSSIBLE SPECIAL MARINE WARNINGS AND MARINE WEATHER STATEMENTS FOR THE STRONGER THUNDERSTORM ACTIVITY. && .AVIATION... VFR CONDITIONS WILL PREVAIL THIS EVENING ALONG THE FLIGHT ROUTE FROM MIAMI TO KEY WEST...AND AT OUR ISLAND TERMINALS. SHOWERS AND THUNDERSTORMS ON THE MAINLAND LEG OF THE ROUTE WILL HAVE A SLOW DRIFT TOWARD THE WEST OR SOUTHWEST...WHICH MEANS COVERAGE SHOULD REMAIN ISOLATED TO WIDELY SCATTERED WITHIN THE ROUTE CORRIDOR OVER THE EVERGLADES. A CLOUD LINE IN THE LOWER KEYS IS INTERMITTENTLY ACTIVE. SHOWERS WITHIN THIS FEATURE WOULD AFFECT THE KEY WEST TERMINAL. WE WILL AMEND PROMPTLY IF THUNDER OCCURS OR IS IMMINENT. WE WILL ISSUE A GROUND-HOLD AT KEY WEST IF LIGHTNING IS WITHIN 5 MILES OF THE RUNWAY. && .PRELIMINARY POINT TEMPS/POPS... KEY WEST 80 91 80 90 / 40 40 40 50 MARATHON 80 91 80 91 / 40 40 40 50 && .KEY WATCHES/WARNINGS/ADVISORIES... FL...NONE. GM...NONE. && $$ PUBLIC/MARINE.........KASPER AVIATION/SHORT TERM...DFM DATA COLLECTION.......COTTRILL VISIT US ON THE WEB AT WWW.WEATHER.GOV/KEYWEST fl AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TOPEKA KS 430 PM CDT SUN SEP 16 2007 .DISCUSSION... 20Z SFC OBS SHOWED THE WARM FRONT STILL LOCATED MAINLY SOUTH OF THE FORECAST AREA. CONTINUOUS LIFT OVER THE FRONT HAS CAUSED ISOLATED SHOWERS AND THUNDERSTORMS TO PERSIST THROUGH THE DAY TODAY. ALOFT WATER VAPOR SHOWED A LOW AMPLITUDE RIDGE FROM SOUTH TO NORTH ACROSS THE PLAINS AS A UPPER LEVEL TROUGH MOVES INLAND ACROSS THE PACIFIC NORTHWEST. FOR TONIGHT...MAIN QUESTION IS WHEN WILL THE WARM FRONT FINALLY LIFT NORTH. LATEST RUC DATA STILL SHOWS IT LIFTING INTO NEB BY 06Z MEANWHILE THERE IS CONCERN FOR PRECIP CONTINUING INTO THE EVENING AS LONG AS MOISTURE CONTINUES TO ADVECT NORTH OF THE FRONT. WITH THIS IN MIND CONTINUED WITH SLIGHT CHANCE POPS ACROSS THE NORTHEAST WHERE NAM AND RUC ISENTROPIC SFC SHOW CONTINUED LIFT WITH SOME DECENT MOISTURE. THIS SEEMS TO FIT IN WITH RADAR TRENDS AS WELL. BELIEVE ONCE THE FRONT FINALLY LIFTS NORTH...PRECIP CHANCES WILL BE NIL THROUGH MONDAY WITH LITTLE OR NO FORCING SEEN FROM MODELS. LOWS TONIGHT COULD BE TRICKY WITH TEMPERATURES RISING DURING THE EVENING ACROSS THE NORTH AS WAA FINALLY MOVES IN. ADDITIONALLY THE PRESSURE GRADIENT IS EXPECTED TO TIGHTEN OVERNIGHT KEEPING THE BOUNDARY LAYER WELL MIXED. IN GENERAL STAYED RELATIVELY CLOSE TO PREVIOUS FORECAST AND GUIDANCE. MAIN PROBLEM FOR MONDAY WILL BE WHETHER WIND ADVISORY CRITERIA WILL BE MET. AS UPPER TROUGH ALONG THE WEST COAST MOVES EAST...LEE TROUGH IS EXPECTED TO DEEPEN. THIS WILL CAUSE WINDY CONDITIONS ACROSS THE REGION. THE NEXT SHIFTS WILL WANT TO SEE IF THE GRADIENT WILL BE STRONG ENOUGH FOR SUSTAINED 30 MPH WINDS OR NOT. FOR NOW KEPT THE WINDS IN THE 20 TO 30 MPH RANGE. -WOLTERS FOR MONDAY NIGHT...FLOW TURNS SOUTHWEST ALOFT WITH SEVERAL PIECES OF ENERGY HINTED BY MODELS COMING THROUGH FLOW. AHEAD OF THESE FEATURES STRONG LOW LEVEL JET AND SOME ISENTROPIC LIFT AND WAA DEVELOP OVER AREA BY LATE NIGHT. HAVE KEPT SOME LOW CHANCES POPS IN THE NORTHCENTRAL BEFORE MIDNIGHT FOR THIS REASON AND UPPED INTO THE CHANCE RANGE ALONG AND WEST OF AN ABILENE TO HIAWATHA LINE AFTER AFTER 06Z. GFS HINTING OF WEAK SHORTWAVE COMING THROUGH AFTER MIDNIGHT WHILE NAM KEEPING ENERGY FURTHER WEST OTHERWISE WOULD HAVE SPREAD PRECIPITATION FURTHER EAST. H850 MB WINDS 50 TO 55 KTS ON NAM AND GFS 40 TO 45 KTS OVERNIGHT SO SHOULD STILL BE SOMEWHAT BREEZY THROUGH MUCH OF THE NIGHT. KEPT LOWS IN THE UPPER 60S MOST AREAS. ON TUESDAY INTO TUESDAY NIGHT...BOTH GFS AND NAM BRING MAIN SHORTWAVE THROUGH DURING THE AFTERNOON AND EVENING HOURS. HAVE UPPED POPS INTO THE 40 TO 50 PERCENT RANGE AT THIS POINT FOR AREAS GENERALLY ALONG AND NORTH OF I70 TUESDAY AFTERNOON AND GENERALLY OVER THE EASTERN THIRD OF CWA TUESDAY NIGHT. NAM SHOWING SURFACE BASED INSTABILITY IN THE 2000-3000 J/KG RANGE DURING THE AFTERNOON HOURS WHEN MAIN LIFT SHOULD BE PUSHING INTO AREA. HAVE ADDED SOME STRONG TO SEVERE THUNDERSTORM WORDING TO HWO PRODUCT FOR TUESDAY AFTERNOON AND EVENING. HAVE HIGHS TUESDAY IN THE MID 80S NORTH TO UPPER 80S SOUTH GIVEN EXPECTED CLOUD COVER AND PRECIPITATION. LATE TUESDAY NIGHT INTO WEDNESDAY SHOULD SEE PRECIPITATION CHANCES GREATLY DIMINISH AS WAVE AND MAIN LIFT PUSH EAST. HAVE KEPT SOME SMALL CHANCE POPS FOR WEDNESDAY AS FRONT MEANDERS AROUND CWA ALONG WITH SOME WEAK OVERRUNNING/ISENTROPIC LIFT. HAVE HIGHS WEDNESDAY MAINLY IN THE MIDDLE 80S. WITH FRONT RETREATING NORTHWARD WEDNESDAY NIGHT...KEPT SOME SLIGHT CHANCE POPS ALONG AND NORTH OF I70. STILL QUITE A VARIANCE IN MODEL SOLUTIONS FROM THURSDAY THROUGH THE WEEKEND. THE GFS SEEMINGLY THE OUTLIER WITH DEVELOPMENT OF CLOSED LOW OFF THE CALIFORNIA COAST AND ITS SLOW PROGRESSION EASTWARD. IT ALSO DEEPENS THE NORTHERN STREAM THURSDAY NIGHT INTO FRIDAY DAY BRINGING A NORTHERN STREAM BOUNDARY INTO THE AREA BY SATURDAY MORNING. AT THIS POINT GOING ALONG WITH HPC AND FAVORING THE 00Z ECMWF AND ENSEMBLE GFS SOLUTIONS. THUS TEMPERATURE TRENDS AND WINDS THE MAIN CONCERN FOR THURSDAY INTO SATURDAY. ALL MODELS STILL SHOWING SOME INCREASING LOW LEVEL RH RETURNS DURING THE DAY THURSDAY AND H850 MB TEMPS NOT AS WARM AS YESTERDAY`S RUNS FOR THURSDAY. THUS HAVE KEPT HIGHS IN THE MID TO UPPER 80S. GFS H850 MB WINDS DIMINISHED TO 25 TO 30KT WHILE THE ECMWF KEEPING H850 MB WINDS JUST A BIT HIGHER. WITH OVERNIGHT WINDS EXPECTED TO PROVIDE SOME MIXING...HAVE LOW TEMPERATURES THURSDAY NIGHT IN THE MIDDLE 60S MOST AREAS. FOR FRIDAY INTO SATURDAY...ECMWF KEEPING SOME RIDGING ALOFT OVER AREA WITH MINOR WAVE TO THE NORTH. IT OPENS CALIFORNIA LOW AND GRADUALLY LIFTS NORTHEAST WHILE GFS KEEPS LOW OFF THE CALIFORNIA COAST AND AS MENTIONED ABOVE DEEPENS NORTHERN STREAM WAVE. THE GFS WOULD PUSH A SURFACE REFLECTION INTO THE NORTHERN COUNTIES FRIDAY NIGHT INTO SATURDAY WITH SOME THUNDERSTORM/RAIN POTENTIAL. OPTING AT THIS POINT THE DRIER ECMWF SOLUTION. HAVE HIGHS FRIDAY IN THE UPPER 80S MOST AREAS IN CASE SOME CLOUDS SPREAD SOUTH FROM NORTHERN STREAM. LOWS FRIDAY NIGHT AGAIN MIDDLE 60S. HIGHS SATURDAY IN THE MID TO UPPER 80S AS CLOUDS INCREASE WITH APPROACHING WESTERN SYSTEM. FOR SUNDAY...ENHANCED RESOLUTION ECMWF HAS UPPER LOW LIFTING INTO NORTHERN PLAINS BY 00Z MONDAY WITH TROUGH EXTENDING SOUTH AND HINTING OF SOME PRECIPITATION DEVELOPMENT. GFS HAS SYSTEM OVER CALIFORNIA...DRY OVER THE PLAINS. WITH DIFFERING SOLUTIONS...HAVE KEPT NEXT SUNDAY DRY AT THIS POINT. HIGHS MAINLY IN THE MIDDLE 80S. PF && .AVIATION... EXPECT MID LEVEL CLOUDS TO PERSIST UNTIL THE WARM FRONT LIFTS NORTH BETWEEN 00Z AND 03Z. THERE COULD ALSO BE SOME ISOLATED SHOWERS AROUND WHILE THE FRONT REMAINS SOUTH OF THE TAFS. OTHERWISE EXPECT CLEARING SKIES ONCE THE FRONT LIFTS NORTH. WINDS WILL REMAIN UP OVERNIGHT AROUND 10-12KTS. WINDS SHOULD INCREASE WITH GUSTS APPROACHING 30KTS FROM THE SSW DURING THE DAYTIME HOURS MONDAY. && .TOP WATCHES/WARNINGS/ADVISORIES...NONE. && $$ ks AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GOODLAND KS 200 PM MDT SUN SEP 16 2007 .SHORT TERM... (TONIGHT - WEDNESDAY) FORECAST CONCERNS WILL BE SLIM PRECIPITATION CHANCES TONIGHT NORTH OF A RETREATING WARM FRONT...THEN BETTER CHANCES OF THUNDERSTORMS MONDAY AFTERNOON THROUGH TUESDAY MORNING. WARM FRONT CURRENTLY HUNG UP ACROSS THE FORECAST AREA. HIGH RESOLUTION NAM AND RUC MODELS FORECAST IT TO LIFT NORTH AND BE JUST ABOUT OUT OF THE CWA BY 12Z MONDAY. BASED ON THAT POSITION NOT EXPECTING FOG TO REDEVELOP TONIGHT...THOUGH WILL BE A CLOSE CALL FOR NEBRASKA COUNTIES. 315K ISENTROPIC CHARTS SHOW LOW LEVEL TROUGH AXIS APPROACHING FROM THE NORTHWEST TONIGHT WITH 50KT SOUTHWESTERLY LOW LEVEL JET AHEAD OF IT POINTING INTO NEBRASKA. INTENSE ISENTROPIC LIFT FORECAST ALONG AND JUST NORTH OF THE WARM FRONT. AGAIN TOO CLOSE TO CALL SO WILL HAVE SOME POPS IN THE NORTHERN ZONES. MONDAY AND MONDAY NIGHT...SHORTWAVE TROUGH CURRENTLY OVER THE SOUTHWEST WILL MOVE ACROSS THE FORECAST AREA. Q-VECTORS/QG FORCING VERY FAVORABLE FOR UPWARD VERTICAL MOTION WITH THIS SYSTEM. BEST SHEAR AND INSTABILITY WILL BE ACROSS NORTHERN ZONES...BUT THINK ALL LOCATIONS STAND A GOOD CHANCE OF RECEIVING MEASURABLE PRECIPITATION AND RAISED POPS ACCORDINGLY. 310K ISENTROPIC CHARTS SHOW THE 700MB TROUGH AXIS STILL ACROSS THE CWA TUESDAY MORNING...WITH UPGLIDE AHEAD OF IT. WILL CARRY SOME CHANCE POPS INTO TUESDAY MORNING...TAPERING OFF IN THE AFTERNOON AS THE SYSTEM MOVES EAST. BROAD SOUTHWESTERLY FLOW ALOFT WILL DEVELOP ON WEDNESDAY...WHILE SOUTHEASTERLY WINDS AT THE SURFACE WILL ADVECT MOISTURE INTO THE AREA. SOME DECENT SURFACE BASED INSTABILITY FORECAST BUT CANNOT FIND LIFTING MECHANISM EITHER ALOFT OR AT THE SURFACE. IF ANYTHING 500MB HEIGHTS ARE RISING WITH SUBTLE ANTICYCLONIC CURVATURE TO THE FLOW. WILL KEEP IT DRY. .LONG TERM... (THURSDAY - SUNDAY) UPPER TROUGH WILL DROP INTO THE DESERT SOUTHWEST AND BECOME CUT OFF FROM THE MAIN FLOW. IT WILL EJECT NORTH/NORTHEASTWARD LATE IN THE PERIOD. LOCAL AREA WILL BE ON THE EASTERN FRINGE OF FASTEST SOUTHWEST FLOW ALOFT THIS PERIOD. MREF CONSENSUS FORECAST AND NORMALIZED ANOMALIES CONTINUE TO SUPPORT ABOVE NORMAL TEMPERATURES. AS FOR THE LATE PERIOD TROUGH EJECTING...THINK IT WILL BE SLOWER THAN CURRENTLY PROGGED. IN ADDITION...IT MAY TRACK NORTH/WEST OF THE AREA AND RESULT IN DRY SLOTTING. WILL TAKE A PERSISTENCE PHILOSOPHY AND KEEP IT WARM AND DRY. && .AVIATION...INITIALLY VFR CONDITIONS WILL PREVAIL ACROSS THE CENTRAL HIGH PLAINS THROUGH LATE AFTERNOON/EARLY EVENING. ISOLATED THUNDERSTORMS WILL BE POSSIBLE ALONG THE WARM FRONT WHICH WAS LOCATED ALONG A LINE FROM JUST NORTH OF KHYS TO NORTH OF KTQK. THIS WARM FRONT INTERSECTED THE TROUGH AXIS ACROSS WICHITA COUNTY SSE OF LEOTI IN WEST CENTRAL KANSAS. ANY THUNDERSTORMS THAT MANAGE TO DEVELOP SHOULD BE DIURNALLY DRIVEN AND DECREASE AROUND 03-04Z AS THE WARM FRONT TRANSLATES SLOWLY NNE. SIMILAR TO THE PAST COUPLE OF NIGHTS...CONVERGENCE ASSOCIATED WITH A DEVELOPING NOCTURNAL LLJ AND MODEST MID LVL WAA MAY ALLOW WIDELY SCATTERED THUNDERSTORMS TO DEVELOP AFTER 04-05Z...ESPECIALLY NORTH OF A LINE FROM BENKELMAN TO HOXIE WHERE MVFR CONDITIONS WILL BE POSSIBLE IN LOW CIGS. && .GLD WATCHES/WARNINGS/ADVISORIES... KS...NONE. NE...NONE. CO...NONE. && $$ JDK/JDK/MWM ks AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MARQUETTE MI 428 PM EDT SUN SEP 16 2007 .SHORT TERM (TONIGHT AND MON)... WATER VAPOR IMAGERY AND RUC ANALYSIS SHOW A RIDGE EXTENDING FROM THE WRN PLAINS TO ALBERTA/SASKATCHEWAN. DOWNSTREAM TROF OVER ERN CANADA INTO THE NE CONUS IS BEGINNING TO LIFT OUT. MEDIUM RANGE MODELS INDICATE THIS PROCESS WILL CONTINUE AS THE TROF IS REPLACED WITH A RIDGE OVER THE ERN CONUS THIS WEEK. SO...THIS WILL OVERALL BE A MUCH WARMER WEEK THAN LAST WEEK. WITH THESE CHANGES IN THE LARGE SCALE PATTERN...WAA REGIME IN DEVELOPING DEEP LAYER SW FLOW AND SHORTWAVE ENERGY LIFTING NE TOWARD THE GREAT LAKES WILL OFFER PCPN CHANCES. IT APPEARS THAT THE FIRST OF THESE SHORTWAVES TO APPROACH THE AREA WILL BE THE ONE CURRENTLY OVER SRN NV. CLOSER TO HOME...VIS SATELLITE IMAGERY SHOWS MIXED STRATOCU/AC CLOUDS SPREADING ACROSS WRN AND CNTRL UPPER MI. FATE OF THESE CLOUDS WILL BE A FCST ISSUE TONIGHT. ATTENTION THEN TURNS TO PCPN CHANCES MON AFTN. AS VIEWED ON 300 AND 305K SFCS...ONGOING MOIST ISENTROPIC ASCENT WHICH SUPPORTING CLOUDS OVER FCST AREA RIGHT NOW WILL SHIFT E OF THE AREA TONIGHT. ISENTROPIC ASCENT WILL CONTINUE...BUT CONDENSATION PRES DEFICITS INCREASE. SO PLAN IS TO TREND TOWARD LESS CLOUD COVER FROM W TO E DURING THE LATE AFTN AND EVENING HRS. EXPECT BULK OF THE OVERNIGHT HRS TO BE MOSTLY CLEAR/PARTLY CLOUDY...BUT WILL NEED TO WATCH FOR ADDITIONAL STRATOCU DEVELOPMENT LATE IN THE NIGHT AS LOW-LEVEL MOISTURE ADVECTS NWD THRU THE PLAINS TOWARD THE WRN LAKES. AS FOR TEMPS...SRLY WINDS WILL KEEP W AND NCNTRL DOWNSLOPING AREAS WARMEST...PROBABLY WITH MINS NO LWR THAN THE LOW/MID 50S. EXPECT SIMILAR READINGS NEAR LAKE MICHIGAN WITH BRISK S TO SW WINDS OVER THE WATER. EXPECT 40S IN THE INTERIOR. SHORTWAVE STREAKS NE TOWARD UPPER MI MON AFTN BRINGING WITH IT AN IMPRESSIVE SURGE OF 850MB THETA-E ADVECTION. PRECIPITABLE WATER ALSO INCREASES DRAMATICALLY FROM AROUND 0.5 INCHES TONIGHT TO 1.5 TO 1.75 INCHES MON AFTN. WEAK SHORTWAVE AND MOISTURE SURGE SHOULD BE SUFFICIENT FOR SOME SHRA/TSRA ACTIVITY MON AFTN OVER THE W HALF OF THE FCST AREA. OTHERWISE...WARMING WILL CONTINUE WITH 850MB TEMPS REACHING 14-16C IN THE AFTN. HOWEVER...INCREASING CLOUD COVER WILL KEEP HIGH TEMPS FROM REACHING THEIR POTENTIAL. EXPECT LOW-MID 70S TO BE THE RULE...BUT IF CLOUDS ARE SLOWER TO ARRIVE...TEMPS WILL BE SEVERAL DEGREES HIGHER. COOLEST READINGS WILL BE NEAR LAKE MICHIGAN WHERE A STIFF S WIND WILL KEEP TEMPS IN THE 60S. .LONG TERM (MON NIGHT THROUGH NEXT SUN)... MAIN FORECAST CONCERNS ARE PCPN CHANCES FOR MON NIGHT THROUGH WED MORNING...THEN TEMPERATURES FRI THROUGH SUN. MON NIGHT AND TUE...AT 00Z TUE...UPPER LEVEL TROUGHING SHOULD BE LOCATED OVER THE INTERMOUNTAIN WEST WITH RIDGING FROM LOUISIANA INTO LOWER MICHIGAN...WHILE AT THE SURFACE A 1001 MB LOW IS EXPECTED NEAR ABERDEEN SOUTH DAKOTA. SW FLOW BETWEEN THE RIDGE AND TROUGH AND WHICH EXTENDS INTO UPPER MICHIGAN FAVORS SHRTWVS TO RIDE ACROSS THE AREA...AND IN FACT...THE GFS/NAM DO SHOW ONE MOVING THROUGH MON NIGHT. THE 12Z ECMWF/UKMET SHOWS THE SAME SHRTWV BUT JUST LOCATED A BIT FARTHER WEST SINCE IT HAS A MUCH MORE AMPLIFIED RIDGE INTO LOWER MICHIGAN. ALTHOUGH THE UKMET IS FURTHER WEST WITH THE SHRTWV...ALL MODELS INDICATE A WARM ADVECTION SCENARIO MON NIGHT AS THE BASE OF THE INTERMOUNTAIN TROUGH PUSHES EASTWARD INTO THE CENTRAL PLAINS. GIVEN THE WARM ADVECTION...ALL MODELS GENERATE QPF ACROSS THE WEST HALF OF THE AREA...THUS HAVE DECIDED TO RAISE POPS TOWARDS LIKELY (SIMILAR TO GUIDANCE). OVER THE EAST HALF...WITH THE UKMET BUILDING MORE RIDGING HERE...THERE IS LESS PROBABILITY FOR PCPN AND HAVE DECIDED ONLY TO RAISE POPS TO 50 IN RESPECT FOR THE GFS/NAM. PRECIP SHOULD TAPER OFF AFTER 06Z OVER THE SOUTH CENTRAL AS CAPPING UNDER THE LOW LEVEL JET MOVES IN. A WARM NIGHT IS EXPECTED WITH BREEZY S TO SE WINDS. ON TUE...THE TROUGH OVER THE CENTRAL PLAINS WILL LIFT INTO WESTERN MN. A FEW SHRTWVS ARE INDICATED AHEAD OF IT TO CROSS WESTERN LAKE SUPERIOR AND WESTERN UPPER MICHIGAN DURING THE DAY...ENOUGH TO KEEP CHANCE OR LIKELY POPS GOING THERE. GIVEN STRONG SHEAR PRESENT AND ELEVATED CAPE VALUES BETWEEN 500-1000 J/KG...MAY HAVE TO WATCH FOR SOME SEVERE STORMS WITH LARGE HAIL THE MAIN HAZARD. DAY 3 OUTLOOK HAS AREA IN 5 PCT. THE REST OF THE U.P. WILL BE SOLIDLY IN THE CAPPED WARM SECTOR WITH 850MB TEMPS OF 16-18C. GIVEN BREEZY SOUTHERLY WINDS AHEAD OF THE APPROACH LOW AND COLD FRONT...AND THOSE WARM 850MB READINGS...AN UNSEASONABLY WARM AND HUMID DAY IS EXPECTED. PARTLY SUNNY SKIES SHOULD AT LEAST ALLOW READINGS IN THE EAST HALF OF THE U.P. AWAY FROM LAKE MI CLIMB INTO THE LOW 80S. IF MORE SUN OCCURS...MID 80S ARE CERTAINLY POSSIBLE. RECORD HIGH FOR THE OFFICE IS 86. COOLER TEMPS EXPECTED IN THE WESTERN U.P. WHERE THERE APPEARS TO BE MORE CLOUDS. REGARDING HUMIDITY...MODEL GUIDANCE AGREES THAT AT LEAST LOW 60S DEWPOINTS SHOULD COME UP HERE. TUE NIGHT AND WED...SHRTWV TROUGH AND THE SURFACE LOW OVER WESTERN MN WILL CONTINUE TO BE LIFTED NORTHEAST ATOP THE STRONG RIDGE OVER LOWER MICHIGAN...IN RESPONSE TO A NEW BUT MUCH DEEPER TROUGH DIVING SOUTH INTO THE PACIFIC NW. GIVEN THAT THE MODELS HAVE BEEN FAIRLY CONSISTENT ON THE TRACK OF THIS SHRTWV...AND ALL THE MOISTURE PRESENT...THERE IS ENOUGH CERTAINTY TO RAISE POPS TO LIKELY OVER THE WESTERN U.P.. ON THE MOISTURE NOTE...PRECIPITABLE WATER VALUES ARE PROGGED BETWEEN 1.5 AND 2 INCHES...WHICH IS 300 PERCENT ABOVE NORMAL! THUS ANY STORMS THAT MOVE THROUGH COULD PRODUCE HEAVY RAINFALL...AS INDICATE BY THE NAM SHOWING SOME VERY HIGH QPF AMOUNTS WHERE IT THINKS STORMS HAVE TRACKED (3.2 INCHES FOR CMX BETWEEN 21-03Z). FOR THE EASTERN U.P....DELAYED POPS UNTIL AFTER 06Z...AND THIS MIGHT EVEN HAVE TO BE PUSHED BACK FURTHER SINCE THE SHRTWV TRACK IS SW TO NE...MAINTAINING RIDGING THERE. ON WED...HAVE KEPT IN SOME CHANCE POPS IN THE MORNING OVER MUCH OF THE CWA...EXCLUDING IMMEDIATELY ALONG THE WISCONSIN BORDER. THIS IS DUE TO THE FACT THAT THE NAM/CANADIAN/ECMWF WHICH WERE PREFERRED BY HPC TEND TO HOLD BACK THE SURFACE LOW AND SHRTWV NEAR THE AREA AT 12Z. PCPN STILL LOOKS GOOD ENDING BY 18Z AS THE LOW AND SHRTWV LIFT INTO NE ONTARIO. TUE NIGHT SHOULD ALSO BE ANOTHER MILD AND HUMID NIGHT WITH THE RAIN COMING ACROSS. CLOUD COVER MAY BE SLOW TO LEAVE WED...PREVENTING HIGHS FROM REACHING THEIR MAXIMUM POTENTIAL GIVEN 850MB TEMPS AT LEAST BETWEEN 10-12C. GOING HIGHS LOOKS GOOD FOR NOW. WED NIGHT THROUGH SUN...AT 00Z THU...MODELS ARE ALL IN GOOD AGREEMENT SHOWING A SPLIT TROUGH FROM NORTHERN ALBERTA INTO NORTHERN CALIFORNIA (AN UPPER LOW IN NORTHERN CALIFORNIA)...WITH RIDGING UP INTO THE NE PACIFIC AND FROM TEXAS TO MAINE. THE 00Z/06Z GFS IS LESS PRONOUNCED WITH THE RIDGE IN THE NE PACIFIC COMPARED TO THE CANADIAN/ECMWF/UKMET...AND THUS ALLOWS FOR A VIGOROUS TROUGH TO CROSS THE NORTHERN PLAINS INTO THE GREAT LAKES FRI INTO SAT. UKMET ALSO DEVELOPS A STRONG TROUGH OVER NORTHERN ONTARIO FRI EVENING...BUT NOT AS STRONG AS THE GFS. PER HPC PMDEPD DISCUSSION...HAVE DISCOUNTED BOTH OF THESE SCENARIOS AND FOLLOWED THE MORE CONSISTENT ECMWF/CANADIAN/LOCAL HEMISPHERIC ARW RUN WHICH FOLLOW THE 00Z GFS ENSEMBLE MEAN. NEW 12Z ECMWF/GFS ARE VERY SIMILAR TO THEIR PREVIOUS RUNS. WED NIGHT AND THU STILL LOOK DRY AT THIS POINT AS A BRIEF RIDGE OF HIGH PRESSURE CROSSES THE CWA BEHIND THE TUE NIGHT AND WED SYSTEM. BY LATE THU...SOME STORMS SHOULD FIRE ACROSS CENTRAL/NRN MN IN AN AREA OF STRONG WARM ADVECTION AND IN THE RIGHT ENTRANCE REGION OF A 110 KT JET OVER NORTHERN ONTARIO. AS THE UPPER JET AND WARM ADVECTION ZONE SHIFT EAST...SOME OF THESE STORMS MAY MAKE THEIR WAY INTO UPPER MI OR JUST STAY TO THE NORTH...ENOUGH TO MAINTAIN CHANCE POPS. BY FRI MORNING...THE SURFACE WARM FRONTAL WILL SHIFT NORTH OF UPPER MICHIGAN...PLACING THE AREA IN THE WARM SECTOR. 00Z ECMWF SHOWS 850MB TEMPS CLIMBING TO 16-18C AT 00Z SAT WITH 850MB DEWPOINTS BETWEEN 12-14C...SUGGESTING A DRY...WARM AND HUMID DAY. A SHRTWV TROUGH TOPPING THE NE PACIFIC RIDGE IS EXPECTED TO MOVE ACROSS NORTHERN ONTARIO FRI NIGHT...PUSHING THE FRONTAL BOUNDARY BACK S ON SAT. LAKE BREEZE CONVERGENCE ON THIS BOUNDARY MAY ALLOW FOR STORMS TO FIRE ALONG IT IN SAT AFTERNOON AS SUGGESTED BY THE LOCAL HEMISPHERIC ARW RUN. THIS FRONT WILL NOT STAY LONG OVER THE AREA...DUE TO WARM ADVECTION IN ADVANCE OF THE UPPER TROUGH OVER THE WESTERN U.S. LIFTING NE. WILL KEEP SOME LOW CHANCE POPS FOR THE WARM ADVECTION OVER THE BOUNDARY...BUT THIS IS VERY MARGINAL WITH THE BETTER FORCING BACK TOWARDS THE WEST. ON SUN...THE ECMWF SHOWS AN UPPER RIDGE AXIS WITH 500MB HEIGHTS WAY ABOVE NORMAL...AROUND 588 DAM...OVER UPPER MI BY 12Z SUN...IN ADDITION WITH 850MB TEMPS NEAR 18C. SUBSIDENCE UNDER THIS RIDGE SHOULD RESULT IN A DRY DAY SUN...WITH TEMPERATURES AND HUMIDITY SIMILAR TO FRI. IF THE SOLUTION PRESENTED BY THE ECMWF/CANADIAN/LOCAL HEMISPHERIC ARW RUN DOES PAN OUT...WE COULD BE LOOKING AT MANY DAYS OF NEAR OR ABOVE RECORD HIGHS. FRI...SAT...SUN AND PERHAPS EVEN MON TOO COULD BE IN JEOPARDY. && .AVIATION (FOR THE 18Z TAF ISSUANCE)... VFR CONDITIONS WILL PREVAIL FOR THIS FCST PERIOD. LAYERED VFR CLOUD DECKS WITH BASES BTWN 4KFT AND 7KFT WILL DRIFT ACROSS KCMX/KSAW DURING THE AFTN PER VIS SATELLITE IMAGERY. BACK EDGE SHOULD REACH KCMX AROUND 21Z AND KSAW AROUND 00Z...PROVIDED LINEAR EXTRAPOLATION OF CURRENT MOVEMENT HOLDS. MARGINAL LLWS SHOULD REDEVELOP TONIGHT AS SW WINDS INCREASE ABOVE SFC BASED INVERSION. LLWS WILL THEN QUICKLY END AFTER SUNRISE MON. SHOULD BE A BREEZY DAY MON AT KSAW UNDER FAVORED SRLY FLOW WITH 20-25KT AVBL TO MIX DOWN TO THE SFC. SHRA AND POSSIBLE TSRA MAY AFFECT KCMX JUST BEYOND THIS TAF FCST PERIOD. && .MARINE (FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)... EXPECT 15 TO 25 KT SRLY WINDS TO BE THE RULE FOR THE MOST PART TONIGHT THRU MON UNDER RATHER TIGHT PRES GRADIENT BTWN HIGH PRES WELL TO THE E AND LOW PRES OVER THE DAKOTAS. AS IS TYPICAL FOR SRLY FLOW...THE STRONGER WINDS WILL BE FOUND OVER THE E HALF OF LAKE SUPERIOR. LOCALLY...THE STRONGEST WINDS MAY OCCUR IN THE VCNTY OF GRAND MARAIS AT THE E END OF PICTURED ROCKS NATIONAL LAKESHORE DUE TO TERRAIN AFFECTS. OVER THE W HALF OF THE LAKE...WINDS MAY BACK E OR EVEN NE TOWARD THE FAR WRN PORTION MON AS MARINE INVERSION STRENGTHENS AND SFC PRES FALLS OCCUR JUST TO THE W. AS THE LOW OVER THE DAKOTAS LIFTS NE MON NIGHT/TUE...SRLY WINDS WILL INCREASE. WILL CONTINUE TO FCST 30KT WINDS OVER THE E HALF...BUT THERE IS THE POTENTIAL FOR SOME GALE FORCE GUSTS. AT THIS TIME...IT APPEARS LOW PRES WILL NOT BE WRAPPED UP AS IT PASSES TO THE N...SO NW WINDS AFTER COLD FRONT PASSAGE SHOULD BE FAIRLY LIGHT (10-20KT). WINDS WILL SETTLE DOWN WED NIGHT/EARLY THU AS HIGH PRES BUILDS TO THE UPPER LAKES. NEW LOW PRES DEVELOPING TO THE W WILL BRING ANOTHER ROUND OF INCREASED SRLY WINDS THU NIGHT/FRI. && .MQT WATCHES/WARNINGS/ADVISORIES...NONE. && $$ SHORT TERM...ROLFSON LONG TERM...AJ AVIATION/MARINE...ROLFSON mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN 1230 PM CDT SUN SEP 16 2007 .UPDATE...FOR 18Z AVIATION DISCUSSION BELOW && .DISCUSSION.../ISSUED 404 AM CDT SUN SEP 16 2007/ OVERCAST LOW/MID LEVEL CLOUDS COVERING THE EASTERN TWO-THIRDS OF THE CWA EARLY THIS MORNING. BACK EDGE RUNS FROM KSTC TO KULM WITH AN EASTWARD MOVEMENT AROUND 17 KNOTS. EXPECT THE CLOUDS TO BREAK UP SOME DURING THE MORNING AS THEY MOVE EAST WITH SKIES BECOMING PARTLY TO MOSTLY SUNNY. STRATUS HAS POPPED UP OVER EASTERN NEBRASKA WITH A MOVEMENT TO THE NORTH. RUC 925MB PROGS SHOW THIS EXPANDING RAPIDLY NORTHEAST THIS MORNING BEFORE DIMINISHING OVER EAST CENTRAL MN EARLY THIS AFTERNOON. WILL ALLOW FOR SOME OF THE STRATUS MAKING IT INTO SOUTH CENTRAL MN THIS MORNING. GFS 300K THETA SURFACE SHOWS THAT THE STRATUS WILL BE ONE OF OUR PROBLEMS DEVELOPING TONIGHT WITH SATURATION SETTING IN. OVERALL...STILL PREFER THE 16/00Z GFS OVER THE NAM. USED THE GFS 24 HOURS AGO AND CONTINUED WITH THAT TREND THIS MORNING. THE MAIN PROBLEM WITH THE 16/00Z NAM IS THE DEEPENING SURFACE LOW OVER MN ON TUESDAY. THE 16/00Z ECMWF...WHICH 24 HOURS AGO WAS A COMPROMISE BETWEEN THE NAM AND GFS...IS NOW MORE IN LINE WITH THE GFS. DO THINK THERE WILL BE A WAVE MOVING NORTHEAST ALONG THE FRONT ON TUESDAY BUT JUST NOT THE DEPTH SHOWN BY THE NAM. AFTER SOME SUNSHINE TODAY...MOISTURE AND INSTABILITY WILL BE ON THE INCREASE ACROSS THE WESTERN AND SOUTHERN CWA TONIGHT. ADDED POPS TO THESE AREAS. THINGS BECOME PRETTY UNSTABLE SUNDAY NIGHT AND I WOULDN`T BE SURPRISED IF A SEVERE STORM OR TWO DEVELOPED BY MONDAY MORNING DUE TO THE INTENSE LOW LEVEL THETA-E ADVECTION AND 30 KNOT WINDS 1500 FEET ABOVE THE GROUND. MONDAY STILL LOOKS BAD FOR SOUTHERN MN IN THE AFTERNOON AND EVENING FOR SURFACE BASED CONVECTION AND POSSIBLE TORNADOES. WILL CONTINUE TO MENTION THE CHANCE FOR TORNADOES IN THE HWO THIS MORNING. A WARM FRONT IS SHOWN TO MAKE IT TO NEAR THE MN RIVER BY MONDAY EVENING. SURFACE DEW POINTS IN THE 60 TO 65 DEGREE RANGE EXPECTED. 6 HOUR PRESSURE FALLS OF 4 MILLIBARS ARE CENTERED NEAR MANKATO. 0-1KM SHEAR IS 30-35 KNOTS WITH 0-6KM SHEAR NEAR 50 KNOTS. 40 KNOT WINDS AT 850MB POKE ALL THE WAY INTO KMSP. THE NAM SHOWS A SIMILAR SCENARIO BUT EVEN WORSE. ELEVATED SEVERE STORMS WILL BE POSSIBLE ON MONDAY TO THE NORTH OF THE WARM FRONT. THE ACTION DOESN`T STOP. ALTHOUGH THE WARM FRONT LIFTS NORTH OF THE AREA MONDAY NIGHT...A COLD FRONT WILL SLOWLY MOVE INTO THE MN CWA ON TUESDAY. MORE CONVECTION IS LIKELY...ESPECIALLY TUESDAY AFTERNOON AND EVENING OVER THE EASTERN CWA AS THE AIRMASS DESTABILIZES. STILL BELIEVE WE WILL HAVE A BREAK ON WEDNESDAY. ANOTHER WAVE OF LOW PRESSURE SHOWN TO APPROACH FROM THE WSW THURSDAY AND FRIDAY. THIS WILL PUSH A WARM FRONT NORTH THROUGH THE AREA WITH MORE SHOWERS AND THUNDERSTORMS. HIGHS/LOWS FOR THE NEXT 72 HOURS NEAR MAV VALUES. && .AVIATION.../12Z TAF ISSUANCE/ LAST OF SC DECK OVER WC WI WILL MOVE EAST THROUGH 20Z...AFFECTING ONLY KEAU EARLY. IFR CIGS OVER SW MN DISSIPATING AS MIXING TAKES PLACE. WILL HAVE TO WAIT FOR DEVELOPMENT OF STRATUS INTO SOUTHERN MN LATER TONIGHT...MAINLY AFTER 06Z AS STRONG WAA LIFTS OVER THE AREA. BROUGHT MVFR CIGS INTO AREA MAINLY AFTER 08Z AND LIFTED NORTHEAST OVERNIGHT. MAY SEE IFR CIGS DEVELOP BY 12Z ACROSS MUCH OF THE WEST AND SOUTH. ELEVATED INSTABILITY MOVING ACROSS SRN MN OVERNIGHT AS WELL...AND HAVE ADDED PROB30 TSRA AT KAXN AFTER 08Z ...AND PROB30 SHRA DEVELOPING REMAINDER OF TAF SITES 08Z-14Z PERIOD. SHOULD REMAIN WITH MVFR CIGS THROUGH MUCH OF THE MORNING. && .MPX WATCHES/WARNINGS/ADVISORIES... MN...NONE. WI...NONE. && $$ RAH/DWE/JPR mn