Forecast Discussions mentioning "ACARS", "MDCRS", "AIRCRAFT", "TAMDAR", or "AMDAR" received at FSL on 10/27/07

AREA FORECAST DISCUSSION
NWS SAN DIEGO CA
925 PM PDT FRI OCT 26 2007 .SYNOPSIS... MARINE LAYER CLOUDS WILL SPREAD A LITTLE FARTHER INLAND TONIGHT...WHILE HIGH CLOUDS INCREASE FROM THE SOUTH. THE ADDITIONAL HIGH CLOUD COVER WILL BRING A FEW MORE DEGREES OF COOLING SATURDAY. ON SUNDAY WEAK OFFSHORE FLOW AND REBUILDING HIGH PRESSURE WILL BRING BRIEF WARMING. THEN RETURNING ONSHORE FLOW WILL BRING COOLING NEXT TUESDAY. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... HIGH TEMPERATURES TODAY WERE LOWER THAN YESTERDAY. AT THE COAST IT WAS MUCH LOWER. LINDBERGH FIELDS HIGH THURSDAY WAS 81...TODAY IT WAS 66. INLAND...MOUNTAIN AND DESERT AREAS WERE ABOUT 5 DEGREES LOWER THAN YESTERDAY. SATURDAYS HIGHS WILL BE SIMILAR TO TODAY. SUNDAY WILL BE WARMER WITH THE WEAK OFFSHORE AND BUILDING HEIGHTS ACCOMPANYING THE BUILDING HIGH. THE 1000 FOOT DEEP MARINE LAYER HAS ALREADY MADE INTO SANTA ANA THIS EVENING. CLOUDS OFF THE SAN DIEGO COAST WILL PUSH INLAND AND AREAS OF DENSE FOG ARE POSSIBLE...MAINLY ON THE COASTAL MESAS. IN THE UPPER LEVELS...MID AND HIGH CLOUDS FROM A COMBINATION OF THE REMNANTS OF "KIKO" AND A SHORTLIVED SUBTROPICAL MOISTURE TAP FROM 10N LATITUDE WAS SURGING NORTHWARD TOWARD SOUTHERN CAL THIS EVENING. SOUTHWEST WINDS AHEAD OF A CLOSED LOW LOCATED WEST OF THE BAY AREA WERE AIDING THE NORTHWARD TRANSPORT OF THIS MOISTURE. THE NAM AND GFS ACTUALLY GENERATE LIGHT PRECIP OVER CENTRAL CALIFORNIA FROM THIS FEATURE...BUT THE DESICCATED ATMOSPHERE FROM THE DEPARTED SANTA ANA WILL LIMIT PRECIP AMTS. A FEW SPRINKLES COULD FALL OVER THE LA COUNTY MTNS. ANOTHER IMPACT OF THIS TROUGH WILL BE TO WEAKEN THE STRENGTH OF THE SURFACE HIGH FORMING OVER UTAH SATURDAY NIGHT AND SUNDAY. WEAKER HIGH PRESSURE MEANS WEAKER OFFSHORE GRADIENTS...SO THE OFFSHORE EVENT SLATED FOR SATURDAY NIGHT AND SUNDAY WONT BE AS STRONG AS PREVIOUSLY THOUGHT. THIS UPPER LOW THEN DRIFTS WEST...AND ACCORDING TO THE GFS...TURNS INTO A DEEP CLOSED LOW 600 MILES WEST OF PT CONCEPTION BY 18Z SUNDAY...WHICH HELPS PROP UP THE RIDGE OVER THE INTERMOUNTAIN WEST SUNDAY AFTERNOON. ON MONDAY AND TUESDAY...THIS UPPER LOW WEST OF PT CONCEPTION OPENS UP AND MOVES ACROSS CENTRAL CA. THE AGONY OF FORECASTING CLOSED LOWS HAS NOT CHANGED...AND THE TIMING OF THIS SYSTEM IS QUESTIONABLE. HOWEVER...ANTICIPATE COOLING TUESDAY AND WEDNESDAY FROM A DEEPER MARINE LAYER...AND POTENTIALLY STRONGER WESTERLY WINDS IN THE MTNS FROM INCREASING ONSHORE FLOW AND CLOSER PROXIMITY TO THE JET STREAM. && .AVIATION...270400Z MARINE LAYER WAS ROUGHLY 1000-1200 FEET DEEP BASED ON ACARS AND OBS EARLY THIS EVENING. STRATUS FORECASTS FOR TONIGHT WILL BE A BIT TRICKY DUE TO THE HIGH CLOUDS WHICH WILL INHIBIT DEVELOPMENT AND TREND FROM SOUTH TOWARDS SOUTHEAST FLOW ALOFT WHICH SHOULD LOWER THE MARINE INVERSION. GENERALLY...HEIGHTS WILL BE AROUND 1000 FEET MSL AT THE COASTAL AIRPORTS...BUT SOME LOWERING IS EXPECTED BY MORNING. LOCALLY DENSE FOG WILL OCCUR ON THE MESAS LATE...BUT MOST VSBYS NEAR THE COAST WILL BE 3-5 MILES. CLEARING SHOULD BE EARLY SAT WITH HIGH CLOUDS...ABOVE 15000 FT...PLUS SOME 2-5 MILE VSBYS DUE TO THE SMOKE...WITH LOWEST VSBYS N AND A LITTLE NW OF EACH MAJOR FIRE DUE TO S/SE WIND FLOW ALOFT. STRATUS/FOG COULD RETURN BY LATE EVENING SAT...MOSTLY ALONG THE IMMEDIATE COAST. && .SGX WATCHES/WARNINGS/ADVISORIES... CA...NONE. PZ...NONE. && $$ PUBLIC...MOEDE AVIATION/MARINE...MAXWELL NWS ON THE WEB AT WEATHER.GOV/SANDIEGO
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
1225 PM CDT THU OCT 25 2007 .UPDATE... SENDING OUT A QUICK UPDATE TO FIRST PERIOD TO TWEAK SKY/WIND GRIDS. SCT STRATOCUMULUS DECK CONTINUES TO ADVECT IN OFF THE LAKE IN NE IL...WITH TIME EXPECT THIS STRATOCUMULUS TO FADE THIS AFTERNOON AS MODERATING LOW LEVEL TEMPS LESSEN THE DELTA T`S. AWAY FROM THE LAKE LOOK FOR SUNNY SKIES GIVING WAY TO SLOWING ADVANCING STRATUS DECK FROM THE SOUTH LATER THIS AFTERNOON. OTHER CHANGE WAS TO INCREASE WINDS A BIT AS GRADIENT STILL FAIRLY TIGHT BETWEEN STRONG HIGH OVER QUEBEC AND WEAK LOW APPROACHING FROM THE LOWER MISSISSIPPI VALLEY. PROFILERS AND ACARS SOUNDINGS FROM THIS MORNING SHOW 30-35KT WINDS JUST OFF THE DECK...WHILE THESE WILL DECREASING SOME WITH MIXING...GUSTS OF 20-25KT ARE A GOOD BET FROM THE LAKE INLAND A BIT AS WELL AS OVER OUR SOUTHERN CWA. GOING LOW CHC POPS FOR LIGHT RAIN STILL APPEAR ON TRACK FOR FAR SOUTHERN CWA LATE THIS AFTERNOON. UPDATED GRIDS/DERIVED PRODUCTS HAVE BEEN SHIPPED. IZZI && .DISCUSSION... 330 AM CDT MAIN CONCERN FOR THE MORNING FORECAST PACKAGE WILL FOCUS ON THE EVOLUTION OF THE CUT-OFF LOW OVER THE DEEP SOUTH. AFTER SEVERAL DAYS OF NOT KNOWING WHAT TO DO WITH THIS SYSTEM...THE MODELS HAVE BEEN SHOWING GOOD AGREEMENT ON THE TRACK OF THIS SYSTEM FOR THE PAST FEW RUNS. WHILE THERE ARE SOME VERY SLIGHT TIMING DIFFERENCES BETWEEN THE MODELS ON THE EXACT TRACK OF THE UPPER CENTER AND THE ASSOCIATED SURFACE REFLECTION...THESE SHOULD HAVE VERY LITTLE IMPACT ON THE GENERAL FORECAST. THE TREND CONTINUES TO BE TO INCREASE CLOUD COVER OVER THE CWA FROM SOUTH TO NORTH DURING THE DAY TODAY AND TO INTRODUCE CHANCE POPS FOR LIGHT PCPN OVER THE FAR SOUTHERN COUNTIES BY EARLY AFTERNOON. EXAMINATION OF MODEL RH PROFILES SHOWS A VERY MOIST LAYER BELOW 700MB WITH SIGNIFICANT DRYING ABOVE...MORE OF A DRIZZLE PROFILE THAN CONVECTIVELY DRIVEN SHOWERS. BUT FEEL THAT GIVEN THE DEPTH OF THE SYSTEM ALOFT...THERE IS STILL A GOOD CHANCE FOR MEASURABLE PCPN...SO HAVE GONE WITH 0.01-0.02 INCHES QPF WITH -SHRA RATHER THAN TRACE PCPN AND DRIZZLE. HOWEVER...HAVE BACKED OFF SOMEWHAT ON QPF AMOUNTS THROUGH FRIDAY AFTERNOON GIVEN THE MOISTURE PROFILES...AND THINK A MORE EXTENDED PERIOD OF VERY LIGHT PCPN IS PROBABLE. BY FRIDAY AFTERNOON/EVENING...THE MAIN DYNAMIC CENTER OF THE SYSTEM WILL BE IN CLOSER PROXIMITY TO THE CWA...WITH THE MAIN SFC LOW MOVING THROUGH CNTRL IL TO NWRN IN AND THE UPPER CENTER TRACKING JUST NORTH OF THE OHIO RIVER. GIVEN THIS TRACK AND THE HIGHER FORECAST CONFIDENCE INSTILLED BY GOOD MODEL CONSISTENCY...BOTH RUN-TO-RUN AND MODEL-TO-MODEL...HAVE INCREASED POPS TO LIKELY ACROSS THE CWA FROM FRIDAY AFTERNOON THROUGH SATURDAY AFTERNOON. AS THIS SYSTEM WILL INITIALLY BE RATHER SLOW MOVING...HAVE A 60 HOUR PERIOD WITH POPS/QPF IN THE FORECAST. THE FIRST 24 HRS...18Z TODAY THROUGH 18Z FRIDAY...SHOULD SEE RATHER LIGHT...BUT MEASURABLE PCPN...AROUND .03-.05 INCHES...MORE SIGNIFICANT RAINFALL IS EXPECTED FOR THE LATTER PORTIONS OF THE PERIOD...18Z FRIDAY THROUGH 06Z SUNDAY...WITH AT LEAST A QUARTER INCH OF RAIN FALLING OVER THE CWA...WITH A SWATH OF NEARLY 1 INCH EXTENDING ALONG A LINE ROUGHLY FROM PONTIAC THROUGH VALPARAISO. THE MODELS DO SHOW A STRONG BULLS-EYE OF UVV AND DEEP MOISTURE OVER THE AREA AROUND 06Z SATURDAY...FEEL THAT ANY THUNDER POTENTIAL IS NIL. SATURDAY NIGHT...THE CLOSED LOW WILL BEGIN TO GET CAUGHT UP IN THE STRONGER WESTERLIES OF THE NORTHERN STREAM AND THE CLOSED LOW WILL QUICKLY EVOLVE INTO AN OPEN WAVE AND RAPIDLY EXIT THE REGION. AFTER A FAIRLY MILD PERIOD THROUGH SATURDAY...THE NEXT FORECAST CONCERN WILL BE TEMPERATURES SUNDAY MORNING. WHILE THE CWA HAS FLIRTED WITH PATCHY FROST THE PAST FEW MORNINGS...THERE IS A GOOD CHANCE FOR A HARD FREEZE SUNDAY MORNING FOR THE NWRN PORTIONS OF THE CWA. HAVE LOWERED TEMPS FOR SUNDAY MORNING TO 29 DEGREES FOR LOCATIONS WEST OF INTERSTATE 39...WHERE DECREASING CLOUD COVER AND NEAR-CALM WINDS SHOULD ALLOW FOR STRONG RADIATIONAL COOLING. OTHERWISE...NO OTHER CHANGES MADE TO THE LONGER TERM FORECAST PERIOD. KREIN && .AVIATION... FOR THE 1800 UTC TAFS...LAKE EFFECT STRATOCUMULUS HAS LED TO SOME BKN MVFR CIGS THIS MORNING...HOWEVER MODERATING LOW LEVEL TEMPS SHOULD PUT THE KIBOSH ON THIS CLOUDINESS SOON AND THIS TREND IS ALREADY EVIDENT IN VISIBLE SATELLITE IMAGERY. WILL CONTINUE TO SEE BRISK ENE WINDS THROUGH THE AFTERNOON WITH GUSTS IN THE MID-UPPER 20 KNOT RANGE. OTHERWISE LOOK FOR VFR CIGS TO OVERSPREAD THE TERMINALS LATE THIS AFTERNOON/EARLY THIS EVENING IN ADVANCE OF THE UPPER LOW LIFTING NORTHWARD OUT OF THE LOWER MISSISSIPPI VALLEY. FORECAST SOUNDINGS AND UPSTREAM OBSERVATIONS SUGGEST THAT CIGS WILL PROBABLY BUILD DOWN TO MVFR BY LATE TONIGHT. SOME POTENTIAL CERTAINLY EXISTS FOR A PERIOD OF LIGHT RAIN TONIGHT AS THE FIRST OUTER BAND OF THE UPPER LOW PIVOTS NORTHWARD...BUT CONFIDENCE IN TIMING AND LIKELIHOOD OF OCCURRENCE IS LOW ENOUGH TO HOLD OFF ON INTRODUCING PRECIP AT THIS TIME. BY NEXT TAF ISSUANCE PRECIP CHANCES SHOULD BE A BIT CLEARER AND MAY NEED TO INTRODUCE SOME LIGHT PRECIP AT THAT TIME. IZZI && .MARINE... FOR 3 PM GLF...UPPER LOW AND ASSOCIATED WEAK SURFACE LOW OVER THE LOWER MISSISSIPPI VALLEY WILL LIFT NORTHWARD INTO THE CENTRAL GREAT LAKES BY FRIDAY NIGHT. INITIALLY MODERATE EASTERLY FLOW TO THE NORTH OF THE SURFACE LOW WILL BEGIN TO SLACKEN SOME AS THE LOW APPROACHED FRIDAY INTO FRIDAY EVENING. BY LATE FRIDAY NIGHT INTO SATURDAY THE SURFACE LOW IS EXPECTED TO DEEPEN AS IT ACCELERATES NORTHEASTWARD AND A STRONG 1035MB HIGH MOVES INTO THE PLAINS. STRONG COLD AIR ADVECTION OVER THE RELATIVELY WARM LAKE AND STRONG PRESSURE RISES ALL SEEM TO POINT TOWARD A PERIOD OF GALE FORCE WINDS LATE FRIDAY NIGHT INTO SATURDAY OVER MUCH OF THE LAKE. GALES SHOULD QUICKLY DIMINISH LATE SATURDAY INTO SATURDAY NIGHT AS SURFACE HIGH MOVES EASTWARD INTO THE REGION AND GRADIENT RELAXES. ANOTHER FAST MOVING FRONT IS PROGGED TO APPROACH THE LAKE MONDAY NIGHT WITH A PERIOD OF AT LEAST FORCE 4 SOUTHWESTERLIES POSSIBLE AHEAD OF THE FRONT DURING THE DAY MONDAY. IZZI && .LOT WATCHES/WARNINGS/ADVISORIES... IL...NONE. IN...NONE. LM...SMALL CRAFT ADVISORY THROUGH 03Z FRIDAY FOR THE INDIANA NEARSHORE WATERS AND 08Z FRIDAY FOR THE ILLINOIS NEARSHORE WATERS. GALE WATCH OPEN LAKE LATE FRIDAY NIGHT AND SATURDAY. && $$
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
932 AM CDT THU OCT 25 2007 .UPDATE... SENDING OUT A QUICK UPDATE TO FIRST PERIOD TO TWEAK SKY/WIND GRIDS. SCT STRATOCUMULUS DECK CONTINUES TO ADVECT IN OFF THE LAKE IN NE IL...WITH TIME EXPECT THIS STRATOCUMULUS TO FADE THIS AFTERNOON AS MODERATING LOW LEVEL TEMPS LESSEN THE DELTA T`S. AWAY FROM THE LAKE LOOK FOR SUNNY SKIES GIVING WAY TO SLOWING ADVANCING STRATUS DECK FROM THE SOUTH LATER THIS AFTERNOON. OTHER CHANGE WAS TO INCREASE WINDS A BIT AS GRADIENT STILL FAIRLY TIGHT BETWEEN STRONG HIGH OVER QUEBEC AND WEAK LOW APPROACHING FROM THE LOWER MISSISSIPPI VALLEY. PROFILERS AND ACARS SOUNDINGS FROM THIS MORNING SHOW 30-35KT WINDS JUST OFF THE DECK...WHILE THESE WILL DECREASING SOME WITH MIXING...GUSTS OF 20-25KT ARE A GOOD BET FROM THE LAKE INLAND A BIT AS WELL AS OVER OUR SOUTHERN CWA. GOING LOW CHC POPS FOR LIGHT RAIN STILL APPEAR ON TRACK FOR FAR SOUTHERN CWA LATE THIS AFTERNOON. UPDATED GRIDS/DERIVED PRODUCTS HAVE BEEN SHIPPED. IZZI && .DISCUSSION... 330 AM CDT MAIN CONCERN FOR THE MORNING FORECAST PACKAGE WILL FOCUS ON THE EVOLUTION OF THE CUT-OFF LOW OVER THE DEEP SOUTH. AFTER SEVERAL DAYS OF NOT KNOWING WHAT TO DO WITH THIS SYSTEM...THE MODELS HAVE BEEN SHOWING GOOD AGREEMENT ON THE TRACK OF THIS SYSTEM FOR THE PAST FEW RUNS. WHILE THERE ARE SOME VERY SLIGHT TIMING DIFFERENCES BETWEEN THE MODELS ON THE EXACT TRACK OF THE UPPER CENTER AND THE ASSOCIATED SURFACE REFLECTION...THESE SHOULD HAVE VERY LITTLE IMPACT ON THE GENERAL FORECAST. THE TREND CONTINUES TO BE TO INCREASE CLOUD COVER OVER THE CWA FROM SOUTH TO NORTH DURING THE DAY TODAY AND TO INTRODUCE CHANCE POPS FOR LIGHT PCPN OVER THE FAR SOUTHERN COUNTIES BY EARLY AFTERNOON. EXAMINATION OF MODEL RH PROFILES SHOWS A VERY MOIST LAYER BELOW 700MB WITH SIGNIFICANT DRYING ABOVE...MORE OF A DRIZZLE PROFILE THAN CONVECTIVELY DRIVEN SHOWERS. BUT FEEL THAT GIVEN THE DEPTH OF THE SYSTEM ALOFT...THERE IS STILL A GOOD CHANCE FOR MEASURABLE PCPN...SO HAVE GONE WITH 0.01-0.02 INCHES QPF WITH -SHRA RATHER THAN TRACE PCPN AND DRIZZLE. HOWEVER...HAVE BACKED OFF SOMEWHAT ON QPF AMOUNTS THROUGH FRIDAY AFTERNOON GIVEN THE MOISTURE PROFILES...AND THINK A MORE EXTENDED PERIOD OF VERY LIGHT PCPN IS PROBABLE. BY FRIDAY AFTERNOON/EVENING...THE MAIN DYNAMIC CENTER OF THE SYSTEM WILL BE IN CLOSER PROXIMITY TO THE CWA...WITH THE MAIN SFC LOW MOVING THROUGH CNTRL IL TO NWRN IN AND THE UPPER CENTER TRACKING JUST NORTH OF THE OHIO RIVER. GIVEN THIS TRACK AND THE HIGHER FORECAST CONFIDENCE INSTILLED BY GOOD MODEL CONSISTENCY...BOTH RUN-TO-RUN AND MODEL-TO-MODEL...HAVE INCREASED POPS TO LIKELY ACROSS THE CWA FROM FRIDAY AFTERNOON THROUGH SATURDAY AFTERNOON. AS THIS SYSTEM WILL INITIALLY BE RATHER SLOW MOVING...HAVE A 60 HOUR PERIOD WITH POPS/QPF IN THE FORECAST. THE FIRST 24 HRS...18Z TODAY THROUGH 18Z FRIDAY...SHOULD SEE RATHER LIGHT...BUT MEASURABLE PCPN...AROUND .03-.05 INCHES...MORE SIGNIFICANT RAINFALL IS EXPECTED FOR THE LATTER PORTIONS OF THE PERIOD...18Z FRIDAY THROUGH 06Z SUNDAY...WITH AT LEAST A QUARTER INCH OF RAIN FALLING OVER THE CWA...WITH A SWATH OF NEARLY 1 INCH EXTENDING ALONG A LINE ROUGHLY FROM PONTIAC THROUGH VALPARAISO. THE MODELS DO SHOW A STRONG BULLS-EYE OF UVV AND DEEP MOISTURE OVER THE AREA AROUND 06Z SATURDAY...FEEL THAT ANY THUNDER POTENTIAL IS NIL. SATURDAY NIGHT...THE CLOSED LOW WILL BEGIN TO GET CAUGHT UP IN THE STRONGER WESTERLIES OF THE NORTHERN STREAM AND THE CLOSED LOW WILL QUICKLY EVOLVE INTO AN OPEN WAVE AND RAPIDLY EXIT THE REGION. AFTER A FAIRLY MILD PERIOD THROUGH SATURDAY...THE NEXT FORECAST CONCERN WILL BE TEMPERATURES SUNDAY MORNING. WHILE THE CWA HAS FLIRTED WITH PATCHY FROST THE PAST FEW MORNINGS...THERE IS A GOOD CHANCE FOR A HARD FREEZE SUNDAY MORNING FOR THE NWRN PORTIONS OF THE CWA. HAVE LOWERED TEMPS FOR SUNDAY MORNING TO 29 DEGREES FOR LOCATIONS WEST OF INTERSTATE 39...WHERE DECREASING CLOUD COVER AND NEAR-CALM WINDS SHOULD ALLOW FOR STRONG RADIATIONAL COOLING. OTHERWISE...NO OTHER CHANGES MADE TO THE LONGER TERM FORECAST PERIOD. KREIN && .AVIATION...DISCUSSION REGARDING 12Z TAFS... MAIN CONCERN THIS TAF PERIOD REMAINS GUSTY NELY WINDS AND LAKE EFFECT CLOUDS. A RIDGE OF HIGH PRESSURE MOVING EASTWARD TO THE NORTH OF THE RGN WILL REMAIN IN PLACE THROUGH TODAY. WINDS WILL REMAIN NELY...WITH SPEEDS INCRSG AGAIN TO GUSTS AOA 20 KTS BY LATE THIS MRNG AS LLVLS UNDERGO DIURNAL MIXING. CURRENT SATLT TRENDS SHOW BAND OF LK EFFECT CU/STRATOCU MOVG WWD ACROSS NERN IL. BKN-OVC CIGS ARND 3 THSD FT WILL CONTINUE...WITH GRDL SCATTERING OUT OF CLOUD DECK FROM E-W BY 15Z. CONDS TO RMN VFR RMNDR OF PERIOD...HOWEVER...MORE WIDESPREAD MID-HI LVL CIGS FCST TO DVLP NWWD FROM OH VLY LATE TDY AND TNGT AS UPR LVL LOW OVR NERN MS DRIFTS NWWD TO SERN MO BY 12Z FRIDAY. MERZLOCK && .MARINE...PRELIMINARY DISCUSSION FOR 3AM ISSUANCE... HIGH PRESSURE RIDGE FROM ONTARIO SOUTHWESTWARD ACROSS UPPER MICHIGAN TO THE CENTRAL PLAINS WILL SLOWLY LIFT NORTH ACROSS SOUTHERN ONTARIO THROUGH TODAY...KEEPING A NORTHEAST GRADIENT ACROSS LAKE MICHIGAN INTO FRIDAY MORNING. MEANWHILE...A LOW PRESSURE OVER THE TENNESSEE VALLEY WILL LIFT NORTHWESTWARD TO SOUTHEAST MISSOURI BY FRIDAY MORNING...THEN DRIFT NORTHEASTWARD TO THE SOUTHERN GREAT LAKES BY SATURDAY MORNING. AS THIS WEAK LOW ACCELERATES NORTHEASTWARD INTO QUEBEC ON SATURDAY...A STRONG SURGE OF POLAR AIR IS FORECAST TO DROP SOUTHWARD ACROSS THE WESTERN GREAT LAKES SATURDAY AFTERNOON INTO SATURDAY NIGHT. THIS INCREASING NORTHERLY FETCH MAY REACH GALE FORCE BY LATE SATURDAY...ESPECIALLY WITH A LARGE HIGH PRESSURE BUILDING ACROSS THE PLAINS SATURDAY. IF LATER MODEL GUIDANCE CONTINUES TO SUPPORT THIS SCENARIO...A GALE WATCH MAY BE NEEDED. MERZLOCK && .LOT WATCHES/WARNINGS/ADVISORIES... IL...NONE. IN...NONE. LM...SMALL CRAFT ADVISORY THROUGH 03Z FRIDAY FOR THE INDIANA NEARSHORE WATERS AND 08Z FRIDAY FOR THE ILLINOIS NEARSHORE WATERS. && $$
AREA FORECAST DISCUSSION...UPDATED
NWS MARQUETTE MI
900 PM EDT FRI OCT 26 2007 .UPDATE... UPDATED FCST TO EXPAND PCPN COVG A BIT EARLIER PER RADAR TRENDS. THE INCRS IN COVG HAS BEEN ESPECIALLY IMPRESSIVE OVER THE E NEAR INVERTED TROF STRETCHING N FM SFC LO IN THE LOWER GRT LKS TO ERN LK SUP AND WHERE 00Z APX SDNG SHOWS SOMEWHAT DEEPER MSTR TO H6 OR SO. ANOTHER NARROW BAND OF -SHRA/--SHRA FM BARAGA TO IWD THAT CORRELATES BEST WITH SOMEWHAT HIER H7 SPECIFIC HUMIDITY SHOWN ON 18Z NAM F6 ALSO APPEARS TO BE INCRSG IN COVG. SINCE MODELS SHOW INCRSG DEEP LYR H85-3 QVECTOR CNVGC THRU 06Z...EXPECT THESE TRENDS TO CONTINUE. PCPN SHOULD EXPAND INTO THE CNTRL FM CRYSTAL FALLS TO MQT LAST WITH NARROW WEDGE OF DRY AIR APRNT FM STLT IMAGERY. OVERALL...DRY LLVL AIR SHOWN ON EARLIER TAMDAR SDNG FM SAW/LOWER SFC DWPTS IN THE MID 30S WL RESTRICT PCPN INTENSITY OVER THE W AWAY FM THE BETTER DYNAMICS/DEEPER MSTR TO THE E. STILL EXPECTING SFC COLD FNT ASSOCIATED WITH NRN BRANCH SHRTWV OVER SCNTRL CAN TO MOVE INTO THE W AFT MIDNGT. BUT ARRIVAL OF EVEN DRIER LLVL AIR SHOWN ON THE 00Z INL RAOB BEHIND THE FNT AS WELL AS DEPARTURE OF SHARPER QVECTOR CNVGC TO THE E SHOULD RESULT IN DECRSG PCPN COVG LATE OVER THE W. OTRW...GOING FCST LO TEMPS/INCRSG WINDS BEHIND THE FNT APPEAR ON TRACK. && .SHORT TERM (TONIGHT AND SAT)... WATER VAPOR IMAGERY AND RUC ANALYSIS SHOW A CLOSED MID/UPPER LEVEL LOW CENTERED NEAR ST LOUIS. IT IS BEGINNING TO BE PULLED N BY PROGRESSIVE TROF CURRENTLY EXTENDING FROM HUDSON BAY TO MT. WITHIN THE TROF...A WELL-DEFINED SHORTWAVE WAS DROPPING SE THRU ALBERTA TO SRN SASKATCHEWAN. WITH MIDLEVEL LOW...THERE IS NO PCPN NEAR THE FCST AREA (A FEW SPOTTY -SHRA/SPRINKLES ARE IN WRN WI AND OVER NRN LAKE HURON). MODELS REMAIN IN GOOD AGREEMENT SHOWING MIDLEVEL LOW OVER THE MID MISSISSIPPI VALLEY OPENING UP AND LIFTING NE TONIGHT AND SAT AS THE ALBERTA SHORTWAVE HEADS TO THE UPPER GREAT LAKES. AS WAS THE CASE YESTERDAY...12Z MODEL RUNS CONTINUE TO SHOW DEEP LAYER FORCING TO BE WEAK WITH BOTH THE OPENING UP MIDLEVEL LOW AND WITH THE SHORTWAVE (WHICH IS NOW WELL-DEFINED) APPROACHING FROM THE W. BEST DEEP LAYER FORCING OCCURS OVER THE E WHERE THERE WILL BE A SOMEWHAT BETTER MOISTURE PROFILE ASSOCIATED WITH THE NE MOVING MID MISSISSIPPI VALLEY SYSTEM. SO SOME -SHRA SHOULD DEVELOP. HOWEVER...INHERITED FCST OF LIKELY POPS IS PROBABLY TOO HIGH GIVEN THE OVERALL WEAK FORCING ENVIRONMENT. TO THE W...BAND OF LOW-MIDLEVEL FRONTOGENESIS PRODUCING BANDED CLOUD STRUCTURE FROM DAKOTAS TO HUDSON BAY WILL WEAKEN SOME AS IT SHIFTS E TO THE UPPER LAKES TONIGHT. AT THIS TIME...IT APPEARS AIRMASS IS TOO DRY BASED ON UPSTREAM 12Z SOUNDINGS ACROSS THE NRN PLAINS TO SUPPORT MUCH MORE THAN 20-30 POPS DESPITE RESPECTABLE 12HR 500MB HEIGHT FALLS UPWARDS OF 120M TONIGHT. WITH PASSAGE OF SHORTWAVE AND ANY ASSOCIATED PCPN SAT MORNING... GFS/NAM SHOW A DRY AIRMASS ARRIVING. EVEN THOUGH 850MB TEMPS OVER WRN LAKE SUPERIOR DROP TO -4 TO -6C DURING THE AFTN (BRINGING LAKE-850MB DELTA-T TO AROUND 15C)...FCST SOUNDINGS SUGGEST TOO MUCH DRY AIR TO SUPPORT ANYTHING MORE THAN A BKN STRATOCU DECK OFF THE LAKE. LONGER NW FETCH INTO THE ERN FCST AREA MAY BE SUFFICIENT FOR SOME LIGHT PCPN. SO...WILL NOT COMPLETELY PULL MENTION OF PCPN THERE...BUT DROP POPS TO SLIGHT CHC BY AFTN. AS AIRMASS COOLS FURTHER LATE IN THE AFTN AND LOW-LEVEL MOISTURE INCREASES...THERE SHOULD BE AN INCREASED POTENTIAL FOR -SHRA OVER THE E BY EVENING. .LONG TERM(SATURDAY NIGHT THROUGH FRIDAY)... MAIN FCST CONCERN IS LAKE EFFECT PCPN POTENTIAL SAT NIGHT INTO SUN. SAT NIGHT AND SUN...THE 12Z NAM WAS ALONE WITH A DEEPER SHORTWAVE AND MORE SUBSTANTIAL 850-700 MB MOISTURE MOVING THROUGH THE UPPER GREAT LAKES. SO...THE FCST LEANED MORE TOWARD THE 12Z GFS AND CANADIAN REGIONAL GEM. 850 MB TEMPS TO AROUND -8C GIVING LK-H8 DELTA/T VALUES OF NEAR 17C AND INVERSION HEIGHTS TO 5K FT WILL STILL BE FAVORABLE ENOUGH TO PRODUCE SCT LAKE SNOW SHOWERS WITH A MIX OF RAIN/SNOW OVER OR NEAR THE WARMER WATER. WITH ONLY MARGINAL INSTABILITY AND 850-700 MB MOISTURE EXPECT LITTLE (LESS THAN A HALF INCH) OR NO SNOW ACCUMULATION. ANY LAKE EFFECT PCPN WILL END SUN AFTERNOON AS A SFC RDG MOVE IN AND WINDS BACK OFFSHORE. MON...MDLS HAVE CONTINUED TO TREND TOWARD A WEAKER SHORTWAVE MOVING WELL NORTH OF THE AREA WITH ONLY MINIMAL HEIGHT FALLS INTO THE UPPER GREAT LAKES. PARTLY SUNNY SKIES AND WAA WITH 850 MB TEMPS CLIMBING INTO THE 5C-7C RANGE WILL ALLOW TEMPS TO CLIMB INTO THE MID 50S. TUE-FRI...SIDING CLOSER TO THE HPC PREFERRED 00Z ECMWF (WHICH IS ALSO SUPPORTED BY THE 12Z UKMET) WITH THE SHORTWAVE MOVING THROUGH WED INTO THU...EXPECT SHOWER CHANCES WILL MOVE IN WED WITH MORE SUBSTANTIAL HEIGHT FALLS AND QVECTOR CONV FCST INTO THE CWA FOLLOWED BY ENOUGH CAA (850 MB TEMPS DOWN TO -8C) FOR LAKE EFFECT RAIN OR SNOW SHOWERS...WHICH COULD LINGER INTO EARLY THU. ALTHOUGH MODELS AND GFS ENSEMBLE SPREAD INCREASES SIGNIFICANTLY LATE IN THE WEEK...PROGRESSIVE PATTERN COULD BRING ANOTHER MID LEVEL TROUGH AND PCPN INTO THE CWA FRI...PER ECMWF. && .AVIATION (FOR THE 00Z TAF ISSUANCE)... VFR CONDITIONS WILL PREVAIL THIS FCST PERIOD AT KCMX/KSAW. COLD FRONT WILL PASS ACROSS THE AREA LATE TONIGHT/SAT MORNING...AND WDSPRD HI BASED SC/LO AC WL ACCOMPANY AND TRAIL THIS FEATURE. BUT LLVLS ARE TOO DRY FOR ANY PCPN/CIGS WORSE THAN VFR PER UPSTREAM OBS/DRY LLVLS SHOWN ON PERTINENT RAOBS. AFTER FROPA...EXPECT GUSTY N TO NW WINDS AND SCT-BKN STRATOCU WITH BASES AOA 4K FT WITH LLVL DRY AIR STILL ARND. MORE MID CLD WL OVERSPREAD THE UPR LKS LATER SAT AS ANOTHER SHRTWV NOW MOVING THRU SCNTRL CAN APRCHS. && .MARINE (FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)... MAIN FOCUS FOR THIS FCST ISSUANCE IS THE POTENTIAL FOR GALES LATE TONIGHT/SAT. AS A COLD FRONT CROSSES LAKE SUPERIOR TONIGHT... LOW PRES WILL DEEPEN AS IT LIFTS NE THRU THE CNTRL GREAT LAKES TOWARD QUEBEC. STRENGTHENING COLD AIR ADVECTION W OF THE DEEPENING SFC LOW COMBINED WITH TIGHTENING PRES GRADIENT BTWN THE LOW PRES TO THE E AND HIGH PRES OVER THE DAKOTAS WILL RESULT IN INCREASING N TO NW WINDS OVER THE LAKE. WITH THE LOW-LEVEL TEMP PROFILE BECOMING MORE UNSTABLE OVER THE WATER DUE TO THE INCREASINGLY COLD AIRMASS...STRONGER WINDS ALOFT WILL ALSO BE ABLE TO MIX DOWN TOWARD THE LAKE SFC. END RESULT SHOULD BE A PERIOD OF N TO NW GALES LATE TONIGHT INTO SAT EVENING...MAINLY OVER THE CNTRL AND ERN PORTION OF LAKE SUPERIOR. THIS EVENT WILL LIKELY FEATURE FREQUENT GALE FORCE GUSTS RATHER THAN SUSTAINED GALES AS OVERALL WIND FIELDS ARE NOT ESPECIALLY STRONG. PERIOD OF STRONGEST WINDS SHOULD OCCUR OVER THE CNTRL PORTION OF THE LAKE ROUGHLY 09Z-15Z AND OVER THE E PART OF THE LAKE 15Z-24Z. && .MQT WATCHES/WARNINGS/ADVISORIES... GALE WARNING CNTRL AND ERN LAKE SUPERIOR. && $$ UPDATE...KC SHORT TERM...ROLFSON LONG TERM...JLB AVIATION...KC MARINE...ROLFSON
AREA FORECAST DISCUSSION
NWS GAYLORD MI
124 AM EDT THU OCT 25 2007 .AVIATION...ASIDE FROM SOME LINGERING LAKE CLOUDINESS ALONG THE SHORELINE AREAS...HIGH PRESSURE BUILDING INTO MICHIGAN WILL PROVIDE MOSTLY CLEAR SKIES AND DIMINISHING WIND SPEEDS OVERNIGHT. AS THE HIGH PUSHES EAST OF THE REGION TODAY...EXPECT A LIGHT SOUTHEAST FLOW TO DEVELOP. DESPITE DEPARTING HIGH PRESSURE...EXPECT CLEAR SKIES TO CONTINUE THRU THIS EVENING. && .UPDATE...ISSUED 1039 PM LARGE AREA OF STRONG SURFACE HIGH PRESSURE CONTINUES TO BUILD INTO THE WRN GREAT LAKES REGION LATE THIS EVENING. UPPER LEVEL TROUGH HAS PUSHED EAST OF MICHIGAN...WITH PRONOUNCED RIDGING BUILDING INTO THE UPPER MID WEST. RESIDUAL LAKE EFFECT RAIN SHOWERS IMPACTING LOCATIONS WEST OF US-131 EARLY THIS EVENING HAVE DISSIPATED AS LOW LEVEL FLOW BECOMES ANTICYCLONIC AND DRY LOW LEVEL AIR FILTERS INTO THE REGION. SOME SHALLOW LAKE CLOUDS STILL REMAIN IN THIS AREA...AND ALONG THE FAR NRN LAKE HURON SHORELINE. THE REST OF THE CWA HAS CLEARED AND WINDS ARE STEADILY DIMINISHING. TEMPS ARE DROPPING RATHER QUICKLY...WITH GOV ALREADY REPORTING 32 DEGREES. GOING GRIDS ARE HANDLING DIMINISHING CLOUD...WIND AND TEMP TRENDS NICELY. NO NEED TO MODIFY GRIDS AT THIS TIME. && .UPDATE...ISSUED 448 PM DESPITE A STEADY FALL...WAVE HEIGHTS STILL RUNNING AT 4.5 FT...PER THE LAKE MICHIGAN BUOY. ALTHOUGH HEIGHTS SHOULD CONTINUE TO FALL...FELT IT PRUDENT TO KEEP SCA/S ON ALL NEARSHORE LAKE MICHIGAN WATERS ALONG THE NORTHWEST COAST OF NORTHERN LOWER MICHIGAN THROUGH THIS EVENING. MSB && .DISCUSSION...ISSUED 430 PM MID AFTERNOON SATELLITE/RUC/SURFACE/UPPER AIR AND REGIONAL RADAR ANALYSIS SHOWS MID LEVEL SHORTWAVE TROUGH AXIS ABOUT SET TO EXIT THE NORTHERN LAKES REGION STAGE RIGHT...WHILE FATHER SOUTH...MUCH ADVERTISED CUT OFF MID AND UPPER LEVEL LOW MEANDERS OVER THE LOWER MISSISSIPPI VALLEY. AT THE SURFACE...NORTHERN PLAINS HIGH PRESSURE CONTINUES TO BUILD INTO THE LAKES REGION...WITH NORTH FLOW ON DOWNSTREAM SIDE OF THIS FEATURE CONTINUING THE LIGHT LAKE EFFECT RAIN SHOWERS AND ABUNDANT STRATO-CU OFF BOTH LAKE SUPERIOR AND MICHIGAN. HOWEVER...DESPITE MAINTENANCE OF GOOD OVER-WATER INSTABILITY (DELTA T/S ON THE ORDER OF 16C TO 18C) DRY AIR ENTRAINMENT AND LOWERING INVERSION HEIGHTS BEGINNING TO WIN OUT (UPSTREAM ACARS SOUNDINGS AND SATELLITE IMAGERY SHOWING PRONOUNCED DRYING ABOVE STRENGTHENING 850MB SUBSIDENCE INVERSION AND CLEAR SKIES JUST WEST OF THE BIG LAKES) AS EVIDENCED BY WEAKENING AND LOSS OF AREAL COVERAGE OF SHOWERS OBSERVED ON LOCAL RADARS. RATHER UNUSUAL FOR THIS FALL SEASON...BUT TEMPERATURES REMAINED BELOW NORMAL TODAY...WITH READINGS GENERALLY STUCK IN THE 40S. FORECAST CONCERNS CENTER ON DEMISE OF LAKE EFFECT SHOWERS/CLOUDS AND HOW COLD TO GO WITH TEMPERATURES TONIGHT. TONIGHT...OBSERVATION DATA SUPPORTING 12Z MODEL GUIDANCE SUGGESTING A QUICK END TO ANY LINGERING LAKE EFFECT SHOWERS LATER THIS AFTERNOON AS DRY AIR AND LOWERING INVERSION HEIGHTS CONTINUE THEIR ASSAULT. STILL EXPECTING SOME LINGERING STRATO-CU EARLY THIS EVENING IN NORTH FLOW WIND REGIME AS DELTA T/S REMAIN IN THE MID TO UPPER TEENS. BY LATER THIS EVENING...SKIES SHOULD CLEAR ACROSS THE AREA AS DEEP LAYER SUBSIDENCE AND SURFACE HIGH PRESSURE BUILD THROUGH THE NORTHERN LAKES. SOME CONCERN FOR SOME STRATO-CU TO HANG TOUGH ALONG THE LAKE HURON SHORELINE AREAS OF NORTHERN LOWER MICHIGAN AND FAVORED NORTHEAST FLOW UPSLOPE AREAS ACROSS THE INTERIOR WITH MODELS SUGGESTING A VERY LIGHT NORTHEAST WIND OVER THE LAKE JUST SOUTH OF PRIMARY HIGH CENTER. HOWEVER...AT THIS TIME...CLOSER INSPECTION OF MODEL SOUNDINGS SHOW JUST TOO MUCH DRY AIR TO OVERCOME TO SUPPORT CLOUD GENERATION SO WILL RUN WITH A CLEAR FORECAST. TEMPERATURES EXPECTED TO BEGIN A QUICK DOWNWARD SPIRAL BEGINNING LATE THIS EVENING AS NEARLY IDEAL RADIATIONAL COOLING PARAMETERS SET UP (LIGHT WIND REGIME...AMBIENT DRY AIR...AND CLEAR SKIES). EXPECTING TEMPERATURES BY MORNING TO FALL INTO THE MID TO UPPER 20S OVER INTERIOR REGIONS OF NORTHERN LOWER AND EASTERN UPPER MICHIGAN AND THE LOW TO MID 30S ALONG THE RELATIVE BATH LIKE GREAT LAKES SHORELINES. MARINE...WEAKENING PRESSURE GRADIENT AND LOWERING INVERSION HEIGHTS BEGINNING TO MAKE THEIR PRESENCE FELT OVER LAKE MICHIGAN AND WHITEFISH BAY...WITH GUSTS NOW DROPPING BELOW SCA CRITERIA. ACROSS LAKE HURON...CONDITIONS SHOULD REMAIN FAVORABLE FOR SMALL CRAFT CONDITIONS THROUGH THIS EVENING BEFORE AFOREMENTIONED PARAMETERS TRACK ACROSS THE LAKE. THUS...WILL END ALL ADVISORIES FOR LAKE MICHIGAN AND SUPERIOR WATERS AND EXTEND ADVISORIES ON NEARSHORE LAKE HURON WATERS BORDERING NORTHEAST MICHIGAN THROUGH THIS EVENING. THURSDAY...DRY WEATHER CONTINUES AS MID LEVEL RIDGING BUILDS ACROSS THE NORTHERN LAKES REGION NORTH OF LOWER MISSISSIPPI VALLEY MID AND UPPER LEVEL LOW PRESSURE. BESIDES BEING DRY...MODEL CROSS SECTIONS AND SOUNDINGS SUPPORT MOSTLY SUNNY CONDITIONS...WITH JUST SOME POSSIBLE WIDELY SCATTERED CIRRUS AND CONTRAILS TRAVERSING ABOVE THE LANDSCAPE. AT THE SURFACE...HIGH PRESSURE CENTERED OVER THE HEART OF THE AREA DURING THE MORNING WILL SLOWLY PULL TO THE EAST...ALLOWING A LIGHT SOUTHEAST TO EAST RETURN FLOW TO DEVELOP DURING THE DAY. THIS...COUPLED WITH WARMING LOW AND MID LEVELS (900MB MIXING HEIGHT HAS TEMPERATURES APPROACHING 4C MID AFTERNOON)...EXCEEDINGLY DRY LOW LEVELS (900MB-700MB RH PERCENTAGES <15 PERCENT OVER NORTHERN LOWER MICHIGAN)...AND PLENTY OF SUNSHINE SHOULD LEAD TO A RATHER QUICK DIURNAL RESPONSE IN THE TEMPERATURE DEPARTMENT. EXPECT READINGS BY MID AFTERNOON TO REACH THE MID TO UPPER 50S. MSB THURSDAY NIGHT INTO FRIDAY...HIGH PRESSURE CENTERED OVER MAINE WILL HAVE ONE OF ITS AXES DRAPED ACROSS THE CENTRAL GREAT LAKES TO START THE NIGHT. HOWEVER...AN UPPER LEVEL LOW WILL SLOWLY CREEP NE FROM ARKANSAS INTO ILLINOIS BY FRIDAY AFTERNOON...AND WILL SEND AN 850-700MB THETAE TONGUE NW TOWARDS THE AREA BY LATE THURSDAY NIGHT...BUT MORESO INTO FRIDAY. AS THIS MOISTURE SURGES NW...IT WILL ENCOUNTER VERY DRY AIR (850-700MB RH < 10 PCT) ACROSS NORTHERN MICHIGAN...AND THEREFORE BELIEVE ANY PRECIP WITH THIS MOISTURE ADVECTION WILL HOLD OFF INTO FRIDAY. THE 00Z ECMWF...WHICH USUALLY HAS SUPERIOR PERFORMANCE WITH CUTOFF LOWS...SHOWS THE PREVIOUSLY MENTIONED THETAE TONGUE CONTINUING TO MOVE NNE OVER THE COURSE OF THE DAY WITH ONLY THE SE CORNER OF THE CWA FEELING THE EFFECTS OF THIS DEEPER MOISTURE. WILL THEREFORE CONFINE THE HIGHEST CHANCE OF PRECIP TO THESE ZONES...AND MOSTLY FOR THE AFTERNOON...BUT BELIEVE INCREASING LOW LEVEL MOISTURE WILL HAVE CLOUDS INCREASE FROM SOUTH TO NORTH DURING THE MORNING. WITH LITTLE IN THE WAY OF FORCING...THESE SHOWERS WILL BE MOSTLY LIGHT IN NATURE AND PRODUCE LITTLE IN THE WAY OF QPF. FRIDAY NIGHT INTO SATURDAY...UPPER LOW MOVES FROM ILLINOIS TO LAKE ERIE AS AN APPROACHING NORTHERN STREAM WAVE PICKS UP THIS ENERGY. EVEN THOUGH THE ASSOCIATED SURFACE LOW PASSES ACROSS THE SOUTHERN GREAT LAKES...DEEP LAYER -DIVQ OVERSPREADS THE AREA LATE FRIDAY NIGHT INTO SATURDAY DUE TO CONVERGENCE ALONG THE 850MB TROUGH AXIS. THIS CYCLONIC FLOW ALONG WITH DEEP MOISTURE WILL HELP KEEP SHOWER COVERAGE HIGHER ACROSS THE SE HALF OF THE CWA. MEANWHILE...UPSTREAM NORTHERN STREAM SHORTWAVE WILL APPROACH THE CWA BY LATE IN THE DAY...WHICH WILL HELP MAINTAIN THE CYCLONIC FLOW AND MOISTURE. COLD ADVECTION SETS IN DURING THE AFTERNOON AND 850MB TEMPS WILL DROP FROM AROUND +5C TO THE 0 TO -2C RANGE. AS NORTHWEST WINDS SET IN...SOME OF THIS PRECIP DURING THE AFTERNOON MAY BE ENHANCED BY LAKE EFFECT PROCESSES. THIS APPEARS TO BE A RAINY DAY FOR MOST LOCATIONS ACROSS NORTHERN LOWER (LESS SO ACROSS EASTERN UPPER) WITH HIGHS IN THE MIDDLE 40S NORTH TO LOWER 50S SOUTH. SUNDAY THROUGH WEDNESDAY...PROGRESSIVE AND RELATIVELY ZONAL FLOW WILL BE PRESENT INTO THE MIDDLE OF NEXT WEEK WITH THE PRIMARY STORM TRACK LYING ACROSS THE US-CANADIAN BORDER. SINCE THIS STORM TRACK WILL PASS OVER THE GREAT LAKES...LOOKS LIKE NORTHERN MICHIGAN WILL SEE TEMPERATURES SWINGS EVERY COUPLE DAYS WITH SOME UNSETTLED CONDITIONS IN-BETWEEN. GONE WITH A BLEND OF 00Z ECMWF AND 00Z GFS ENSEMBLE FOR THIS FORECAST. SUNDAY...NORTHERN STREAM SHORTWAVE WILL PASS ACROSS THE AREA DURING THE MORNING HOURS BEHIND A STRENGTHENING SURFACE LOW MOVING INTO THE NORTHEAST US. MID-LEVEL -DIVQ...DEEP LAYER MOISTURE AND CYCLONIC FLOW AHEAD OF THIS WAVE WILL PROVIDE A CHANCE FOR SHOWERS WITH THE BEST CHANCES OVER THE EASTERN HALF OF THE CWA. ADDITIONALLY...850MB TEMPERATURES WILL FALL INTO THE MIDDLE NEGATIVE SINGLE DIGITS BY MID-MORNING...BUT RAPID DRYING BEHIND THE WAVE WILL LIMIT THE TIME IN WHICH THE LAKE EFFECT MACHINE CAN CRANK INTO GEAR. NONETHELESS...TEMPERATURES LOOK COLD ENOUGH THAT ANY RAIN SHOWERS HAVE A CHANCE TO BE MIXED WITH SNOW...ESPECIALLY ACROSS EASTERN UPPER AND THE HIGHER ELEVATIONS OF NORTHERN LOWER. SO...WILL KEEP A CHANCE OF PRECIP THROUGH THE EARLY MORNING HOURS OF SUNDAY BEFORE THE MOISTURE LOOKS MOVE OUT BY MID TO LATE MORNING. HEIGHTS THEN REBOUND ALOFT WHILE THE SURFACE RIDGE AXIS THEN MOVES IN FOR THE REST OF THE DAY. THAT DOES NOT MEAN THAT SKIES WILL CLEAR THOUGH...SINCE THERMAL TROUGHING WITH COLD 850MB TEMPS AROUND MINUS 6 TO 8C SUGGESTS THAT A COLD/STRATO-CUISH DAY IS IN ORDER WITH HIGHS IN THE LOWER TO MIDDLE 40S. MONDAY...THERMAL TROUGHING MOVES EAST WHILE A WARM FRONTAL FEATURE MOVES ACROSS THE AREA MONDAY MORNING AHEAD OF THE NEXT SHORTWAVE CUTTING ACROSS CANADA. BEST LIFT OVER THE WARM FRONT LOOKS TO REMAIN TO THE NORTH CLOSER TO THE SURFACE LOW...AND IN THE LEFT EXIT REGION OF A 100KT JET STREAK. BUT BELIEVE NORTHERN SECTIONS HAVE A CHANCE OF RAIN AND WILL INTRODUCE A CHANCE OF PRECIP ACROSS EASTERN UPPER AND TIP OF THE MITT. 850MB TEMPS DO MODERATE SOMEWHERE NEAR 0C SOUTH OF THE WARM FRONT...BUT CONCERNS WITH AMOUNT OF CLOUD COVER PLACES DOUBT ABOUT HOW MUCH TEMPERATURES WILL WARM. THE SHORTWAVE THEN PUSHES THE COLD FRONT THROUGH THE AREA MONDAY NIGHT...BUT WITH ALL UPPER LEVEL SUPPORT REMAINING TO THE NORTHEAST...AND LIMITED CONVERGENCE ALONG THE FRONT...DO NOT SEE MUCH PRECIP WITH IT AT THIS TIME. TUESDAY INTO WEDNESDAY...NOT TOO CONFIDENT IN THE FORECAST AT THIS POINT. PREVIOUS COLD FRONT LOOKS TO STALL AND WASH OUT ACROSS THE SOUTHERN GREAT LAKES ON TUESDAY. NOT AS MUCH COLD AIR BEHIND THIS FRONT THAN THE PREVIOUS FRONT WITHOUT A STRONG PUSH OF NORTHERLY FLOW...BUT AT LEAST WILL KEEP TUESDAY DRY. RETURN FLOW BECOMES ESTABLISHED ON WEDNESDAY WITH THE NEXT SHORTWAVE PLOWING ACROSS NORTH AMERICA. ARRIVAL TIMING OF THIS WAVE VERY UNCERTAIN...SO WILL KEEP GOING DRY FORECAST FOR WEDNESDAY INTACT. MPC && .APX WATCHES/WARNINGS/ADVISORIES... MI...NONE. LM...NONE. LH...NONE. LS...NONE. && $$
AREA FORECAST DISCUSSION
NWS SAN DIEGO CA
1050 PM PDT FRI OCT 26 2007 .SYNOPSIS... MARINE LAYER CLOUDS WILL SPREAD A LITTLE FARTHER INLAND TONIGHT...WHILE HIGH CLOUDS INCREASE FROM THE SOUTH. THE ADDITIONAL HIGH CLOUD COVER WILL BRING A FEW MORE DEGREES OF COOLING SATURDAY. ON SUNDAY WEAK OFFSHORE FLOW AND REBUILDING HIGH PRESSURE WILL BRING BRIEF WARMING. THEN RETURNING ONSHORE FLOW WILL BRING COOLING NEXT TUESDAY. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... UPDATE TO CURRENT FORECAST FOR TONIGHT THROUGH SATURDAY EVENING TO ACCOUNT FOR MOISTURE FROM THE REMNANTS OF "KIKO"...MAINLY FINE TUNING OF THE PREVIOUS FORECAST. HAVE MOSTLY FOLLOWED THE IDEA OF THE GFS QPF...LIGHT QPF OVER THE SOUTHERN CALIFORNIA BIGHT SATURDAY FROM MID AND HIGH LEVEL MOISTURE WITH LIGHT QPF POSSIBLE OVER NORTHWEST PORTIONS OF THE FORECAST AREA IN THE AFTERNOON...MAINLY HIGHER ELEVATIONS. HAVE INCREASED VALUES IN SKY COVER GRIDS AND ADDED LOW POPS...HIGHEST FOR NORTHWEST SECTIONS AND DURING SATURDAY AFTERNOON. ...FROM PREVIOUS DISCUSSION... HIGH TEMPERATURES TODAY WERE LOWER THAN YESTERDAY. AT THE COAST IT WAS MUCH LOWER. LINDBERGH FIELDS HIGH THURSDAY WAS 81...TODAY IT WAS 66. INLAND...MOUNTAIN AND DESERT AREAS WERE ABOUT 5 DEGREES LOWER THAN YESTERDAY. SATURDAYS HIGHS WILL BE SIMILAR TO TODAY. SUNDAY WILL BE WARMER WITH THE WEAK OFFSHORE AND BUILDING HEIGHTS ACCOMPANYING THE BUILDING HIGH. THE 1000 FOOT DEEP MARINE LAYER HAS ALREADY MADE INTO SANTA ANA THIS EVENING. CLOUDS OFF THE SAN DIEGO COAST WILL PUSH INLAND AND AREAS OF DENSE FOG ARE POSSIBLE...MAINLY ON THE COASTAL MESAS. IN THE UPPER LEVELS...MID AND HIGH CLOUDS FROM A COMBINATION OF THE REMNANTS OF "KIKO" AND A SHORTLIVED SUBTROPICAL MOISTURE TAP FROM 10N LATITUDE WAS SURGING NORTHWARD TOWARD SOUTHERN CAL THIS EVENING. SOUTHWEST WINDS AHEAD OF A CLOSED LOW LOCATED WEST OF THE BAY AREA WERE AIDING THE NORTHWARD TRANSPORT OF THIS MOISTURE. THE NAM AND GFS ACTUALLY GENERATE LIGHT PRECIP OVER CENTRAL CALIFORNIA FROM THIS FEATURE...BUT THE DESICCATED ATMOSPHERE FROM THE DEPARTED SANTA ANA WILL LIMIT PRECIP AMTS. A FEW SPRINKLES COULD FALL OVER THE LA COUNTY MTNS. ANOTHER IMPACT OF THIS TROUGH WILL BE TO WEAKEN THE STRENGTH OF THE SURFACE HIGH FORMING OVER UTAH SATURDAY NIGHT AND SUNDAY. WEAKER HIGH PRESSURE MEANS WEAKER OFFSHORE GRADIENTS...SO THE OFFSHORE EVENT SLATED FOR SATURDAY NIGHT AND SUNDAY WONT BE AS STRONG AS PREVIOUSLY THOUGHT. THIS UPPER LOW THEN DRIFTS WEST...AND ACCORDING TO THE GFS...TURNS INTO A DEEP CLOSED LOW 600 MILES WEST OF PT CONCEPTION BY 18Z SUNDAY...WHICH HELPS PROP UP THE RIDGE OVER THE INTERMOUNTAIN WEST SUNDAY AFTERNOON. ON MONDAY AND TUESDAY...THIS UPPER LOW WEST OF PT CONCEPTION OPENS UP AND MOVES ACROSS CENTRAL CA. THE AGONY OF FORECASTING CLOSED LOWS HAS NOT CHANGED...AND THE TIMING OF THIS SYSTEM IS QUESTIONABLE. HOWEVER...ANTICIPATE COOLING TUESDAY AND WEDNESDAY FROM A DEEPER MARINE LAYER...AND POTENTIALLY STRONGER WESTERLY WINDS IN THE MTNS FROM INCREASING ONSHORE FLOW AND CLOSER PROXIMITY TO THE JET STREAM. && .AVIATION...270400Z MARINE LAYER WAS ROUGHLY 1000-1200 FEET DEEP BASED ON ACARS AND OBS EARLY THIS EVENING. STRATUS FORECASTS FOR TONIGHT WILL BE A BIT TRICKY DUE TO THE HIGH CLOUDS WHICH WILL INHIBIT DEVELOPMENT AND TREND FROM SOUTH TOWARDS SOUTHEAST FLOW ALOFT WHICH SHOULD LOWER THE MARINE INVERSION. GENERALLY...HEIGHTS WILL BE AROUND 1000 FEET MSL AT THE COASTAL AIRPORTS...BUT SOME LOWERING IS EXPECTED BY MORNING. LOCALLY DENSE FOG WILL OCCUR ON THE MESAS LATE...BUT MOST VSBYS NEAR THE COAST WILL BE 3-5 MILES. CLEARING SHOULD BE EARLY SAT WITH HIGH CLOUDS...ABOVE 15000 FT...PLUS SOME 2-5 MILE VSBYS DUE TO THE SMOKE...WITH LOWEST VSBYS N AND A LITTLE NW OF EACH MAJOR FIRE DUE TO S/SE WIND FLOW ALOFT. STRATUS/FOG COULD RETURN BY LATE EVENING SAT...MOSTLY ALONG THE IMMEDIATE COAST. && .SGX WATCHES/WARNINGS/ADVISORIES... CA...NONE. PZ...NONE. && $$ PUBLIC...MOEDE/MARTIN AVIATION/MARINE...MAXWELL NWS ON THE WEB AT WEATHER.GOV/SANDIEGO
AREA FORECAST DISCUSSION...UPDATED
NWS MARQUETTE MI
311 AM EDT SAT OCT 27 2007 .UPDATE... UPDATED FCST TO EXPAND PCPN COVG A BIT EARLIER PER RADAR TRENDS. THE INCRS IN COVG HAS BEEN ESPECIALLY IMPRESSIVE OVER THE E NEAR INVERTED TROF STRETCHING N FM SFC LO IN THE LOWER GRT LKS TO ERN LK SUP AND WHERE 00Z APX SDNG SHOWS SOMEWHAT DEEPER MSTR TO H6 OR SO. ANOTHER NARROW BAND OF -SHRA/--SHRA FM BARAGA TO IWD THAT CORRELATES BEST WITH SOMEWHAT HIER H7 SPECIFIC HUMIDITY SHOWN ON 18Z NAM F6 ALSO APPEARS TO BE INCRSG IN COVG. SINCE MODELS SHOW INCRSG DEEP LYR H85-3 QVECTOR CNVGC THRU 06Z...EXPECT THESE TRENDS TO CONTINUE. PCPN SHOULD EXPAND INTO THE CNTRL FM CRYSTAL FALLS TO MQT LAST WITH NARROW WEDGE OF DRY AIR APRNT FM STLT IMAGERY. OVERALL...DRY LLVL AIR SHOWN ON EARLIER TAMDAR SDNG FM SAW/LOWER SFC DWPTS IN THE MID 30S WL RESTRICT PCPN INTENSITY OVER THE W AWAY FM THE BETTER DYNAMICS/DEEPER MSTR TO THE E. STILL EXPECTING SFC COLD FNT ASSOCIATED WITH NRN BRANCH SHRTWV OVER SCNTRL CAN TO MOVE INTO THE W AFT MIDNGT. BUT ARRIVAL OF EVEN DRIER LLVL AIR SHOWN ON THE 00Z INL RAOB BEHIND THE FNT AS WELL AS DEPARTURE OF SHARPER QVECTOR CNVGC TO THE E SHOULD RESULT IN DECRSG PCPN COVG LATE OVER THE W. OTRW...GOING FCST LO TEMPS/INCRSG WINDS BEHIND THE FNT APPEAR ON TRACK. && .SHORT TERM (TONIGHT AND SAT)... WATER VAPOR IMAGERY AND RUC ANALYSIS SHOW A CLOSED MID/UPPER LEVEL LOW CENTERED NEAR ST LOUIS. IT IS BEGINNING TO BE PULLED N BY PROGRESSIVE TROF CURRENTLY EXTENDING FROM HUDSON BAY TO MT. WITHIN THE TROF...A WELL-DEFINED SHORTWAVE WAS DROPPING SE THRU ALBERTA TO SRN SASKATCHEWAN. WITH MIDLEVEL LOW...THERE IS NO PCPN NEAR THE FCST AREA (A FEW SPOTTY -SHRA/SPRINKLES ARE IN WRN WI AND OVER NRN LAKE HURON). MODELS REMAIN IN GOOD AGREEMENT SHOWING MIDLEVEL LOW OVER THE MID MISSISSIPPI VALLEY OPENING UP AND LIFTING NE TONIGHT AND SAT AS THE ALBERTA SHORTWAVE HEADS TO THE UPPER GREAT LAKES. AS WAS THE CASE YESTERDAY...12Z MODEL RUNS CONTINUE TO SHOW DEEP LAYER FORCING TO BE WEAK WITH BOTH THE OPENING UP MIDLEVEL LOW AND WITH THE SHORTWAVE (WHICH IS NOW WELL-DEFINED) APPROACHING FROM THE W. BEST DEEP LAYER FORCING OCCURS OVER THE E WHERE THERE WILL BE A SOMEWHAT BETTER MOISTURE PROFILE ASSOCIATED WITH THE NE MOVING MID MISSISSIPPI VALLEY SYSTEM. SO SOME -SHRA SHOULD DEVELOP. HOWEVER...INHERITED FCST OF LIKELY POPS IS PROBABLY TOO HIGH GIVEN THE OVERALL WEAK FORCING ENVIRONMENT. TO THE W...BAND OF LOW-MIDLEVEL FRONTOGENESIS PRODUCING BANDED CLOUD STRUCTURE FROM DAKOTAS TO HUDSON BAY WILL WEAKEN SOME AS IT SHIFTS E TO THE UPPER LAKES TONIGHT. AT THIS TIME...IT APPEARS AIRMASS IS TOO DRY BASED ON UPSTREAM 12Z SOUNDINGS ACROSS THE NRN PLAINS TO SUPPORT MUCH MORE THAN 20-30 POPS DESPITE RESPECTABLE 12HR 500MB HEIGHT FALLS UPWARDS OF 120M TONIGHT. WITH PASSAGE OF SHORTWAVE AND ANY ASSOCIATED PCPN SAT MORNING... GFS/NAM SHOW A DRY AIRMASS ARRIVING. EVEN THOUGH 850MB TEMPS OVER WRN LAKE SUPERIOR DROP TO -4 TO -6C DURING THE AFTN (BRINGING LAKE-850MB DELTA-T TO AROUND 15C)...FCST SOUNDINGS SUGGEST TOO MUCH DRY AIR TO SUPPORT ANYTHING MORE THAN A BKN STRATOCU DECK OFF THE LAKE. LONGER NW FETCH INTO THE ERN FCST AREA MAY BE SUFFICIENT FOR SOME LIGHT PCPN. SO...WILL NOT COMPLETELY PULL MENTION OF PCPN THERE...BUT DROP POPS TO SLIGHT CHC BY AFTN. AS AIRMASS COOLS FURTHER LATE IN THE AFTN AND LOW-LEVEL MOISTURE INCREASES...THERE SHOULD BE AN INCREASED POTENTIAL FOR -SHRA OVER THE E BY EVENING. .LONG TERM(SATURDAY NIGHT THROUGH FRIDAY)... MAIN FCST CONCERN IS LAKE EFFECT PCPN POTENTIAL SAT NIGHT INTO SUN. SAT NIGHT AND SUN...THE 12Z NAM WAS ALONE WITH A DEEPER SHORTWAVE AND MORE SUBSTANTIAL 850-700 MB MOISTURE MOVING THROUGH THE UPPER GREAT LAKES. SO...THE FCST LEANED MORE TOWARD THE 12Z GFS AND CANADIAN REGIONAL GEM. 850 MB TEMPS TO AROUND -8C GIVING LK-H8 DELTA/T VALUES OF NEAR 17C AND INVERSION HEIGHTS TO 5K FT WILL STILL BE FAVORABLE ENOUGH TO PRODUCE SCT LAKE SNOW SHOWERS WITH A MIX OF RAIN/SNOW OVER OR NEAR THE WARMER WATER. WITH ONLY MARGINAL INSTABILITY AND 850-700 MB MOISTURE EXPECT LITTLE (LESS THAN A HALF INCH) OR NO SNOW ACCUMULATION. ANY LAKE EFFECT PCPN WILL END SUN AFTERNOON AS A SFC RDG MOVE IN AND WINDS BACK OFFSHORE. MON...MDLS HAVE CONTINUED TO TREND TOWARD A WEAKER SHORTWAVE MOVING WELL NORTH OF THE AREA WITH ONLY MINIMAL HEIGHT FALLS INTO THE UPPER GREAT LAKES. PARTLY SUNNY SKIES AND WAA WITH 850 MB TEMPS CLIMBING INTO THE 5C-7C RANGE WILL ALLOW TEMPS TO CLIMB INTO THE MID 50S. TUE-FRI...SIDING CLOSER TO THE HPC PREFERRED 00Z ECMWF (WHICH IS ALSO SUPPORTED BY THE 12Z UKMET) WITH THE SHORTWAVE MOVING THROUGH WED INTO THU...EXPECT SHOWER CHANCES WILL MOVE IN WED WITH MORE SUBSTANTIAL HEIGHT FALLS AND QVECTOR CONV FCST INTO THE CWA FOLLOWED BY ENOUGH CAA (850 MB TEMPS DOWN TO -8C) FOR LAKE EFFECT RAIN OR SNOW SHOWERS...WHICH COULD LINGER INTO EARLY THU. ALTHOUGH MODELS AND GFS ENSEMBLE SPREAD INCREASES SIGNIFICANTLY LATE IN THE WEEK...PROGRESSIVE PATTERN COULD BRING ANOTHER MID LEVEL TROUGH AND PCPN INTO THE CWA FRI...PER ECMWF. && .AVIATION (FOR THE 06Z TAF ISSUANCE)... EXPECT VFR CONDITIONS AT CMX TNGT EVEN WITH COLD FROPA AS UPSTREAM 00Z INL RAOB SHOWS VERY DRY LLVL AIR BEHIND FNT UNDER MID CLD DECK. BEFORE THIS FNT PASSES SAW ARND 09Z...UPSLOPE NLY FLOW AND SOME LGT RA MAY RESULT IN MVFR CONDITIONS AT TIMES EVEN THOUGH VFR WL PREDOMINATE. THERE WL BE A PD OF GUSTY NNW WINDS BEHIND THIS BNDRY... BUT WINDS WL DIMINISH TOWARD THIS AFTN WITH APRCH OF WEAK HI PRES RDG. ARRIVAL OF THIS DRIER LLVL AIR SHOULD DSPT ANY UPSLOPE SC THAT FORMS IN THE CAD IN THE WAKE OF THE FNT. A REINFORCING SHRTWV/ACCOMPANYING SFC TROF NOW OVER SCNTRL CAN AND THE ARRIVAL OF COLDER AIR THIS EVNG MAY BRING SOME LES. EXPECT A PD OF AT LEAST MVFR CIGS WITH ARRIVAL OF THERMAL TROF. && .MARINE (FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)... MAIN FOCUS FOR THIS FCST ISSUANCE IS THE POTENTIAL FOR GALES LATE TONIGHT/SAT. AS A COLD FRONT CROSSES LAKE SUPERIOR TONIGHT... LOW PRES WILL DEEPEN AS IT LIFTS NE THRU THE CNTRL GREAT LAKES TOWARD QUEBEC. STRENGTHENING COLD AIR ADVECTION W OF THE DEEPENING SFC LOW COMBINED WITH TIGHTENING PRES GRADIENT BTWN THE LOW PRES TO THE E AND HIGH PRES OVER THE DAKOTAS WILL RESULT IN INCREASING N TO NW WINDS OVER THE LAKE. WITH THE LOW-LEVEL TEMP PROFILE BECOMING MORE UNSTABLE OVER THE WATER DUE TO THE INCREASINGLY COLD AIRMASS...STRONGER WINDS ALOFT WILL ALSO BE ABLE TO MIX DOWN TOWARD THE LAKE SFC. END RESULT SHOULD BE A PERIOD OF N TO NW GALES LATE TONIGHT INTO SAT EVENING...MAINLY OVER THE CNTRL AND ERN PORTION OF LAKE SUPERIOR. THIS EVENT WILL LIKELY FEATURE FREQUENT GALE FORCE GUSTS RATHER THAN SUSTAINED GALES AS OVERALL WIND FIELDS ARE NOT ESPECIALLY STRONG. PERIOD OF STRONGEST WINDS SHOULD OCCUR OVER THE CNTRL PORTION OF THE LAKE ROUGHLY 09Z-15Z AND OVER THE E PART OF THE LAKE 15Z-24Z. && .MQT WATCHES/WARNINGS/ADVISORIES... GALE WARNING CNTRL AND ERN LAKE SUPERIOR. && $$ UPDATE...KC SHORT TERM...ROLFSON LONG TERM...JLB AVIATION...KC/AJ MARINE...ROLFSON
AREA FORECAST DISCUSSION
NWS SAN DIEGO CA
230 PM PDT SAT OCT 27 2007 .SYNOPSIS... TROPICAL MOISTURE IN SOUTHWEST FLOW ALOFT WILL BRING CLOUDS AND A CHANCE OF SHOWERS OR THUNDERSTORMS THROUGH THIS EVENING. WARMER SUNDAY IN VERY WEAK OFFSHORE FLOW. UPPER LEVEL LOW PRESSURE WILL BRING ONSHORE FLOW AND A DEEPENING MARINE LAYER MONDAY AND TUESDAY ALONG WITH COOLING. WEAKER ONSHORE FLOW WILL CONTINUE THROUGH FRIDAY WITH AREAS OF COASTAL LOW CLOUDS AND FOG IN THE NIGHTS AND MORNINGS. && .DISCUSSION...FOR SOUTHWEST CALIFORNIA INCLUDING SAN DIEGO... ORANGE...SOUTHWEST SAN BERNARDINO AND WEST RIVERSIDE COUNTIES. .SHORT TERM (TODAY-TUE)...THERE WERE PATCHES OF STRATUS NEAR THE COAST THIS MORNING. THERE WAS ALSO VARIABLE MID TO HIGH CLOUDINESS WITH LIGHTNING STRIKES SW OF SAN DIEGO IN THE MORNING. ISOLATED LIGHT SHOWERS IN THE COASTAL AREAS AND INLAND VALLEYS. EARLY AFTERNOON ACARS SOUNDINGS INDICATE AN INVERSION BASED BELOW 1000 FT WITH S TO SW WINDS ALOFT. WEAK OFFSHORE GRADIENTS FROM THE N AND ONSHORE TO THE E. TROPICAL MOISTURE IN SW FLOW ALOFT WILL CAUSE A SLIGHT CHANCE OF SHOWERS OR THUNDERSTORMS TODAY...MAINLY OVER AND W OF THE MOUNTAINS. RAINFALL TOTALS...IF ANY...ARE EXPECTED TO BE LIGHT AND LESS THAN A TENTH OF AN INCH. THIS MOISTURE WILL DECREASE LATE TONIGHT. WEAK OFFSHORE GRADIENTS WILL DEVELOP FROM THE NE TONIGHT AND SUN MORNING RESULTING IN WEAK OFFSHORE BREEZES. THIS WILL KEEP ANY STRATUS LIMITED TO THE COASTAL AREAS. AN UPPER LOW OFF THE CENTRAL CA COAST WILL SLOWLY APPROACH MON AND THEN MOVE THROUGH TUE MORNING. THE FLOW WILL TURN ONSHORE BY MON AFTERNOON WITH A LITTLE STRONGER ONSHORE GRADIENTS TUE. THE MARINE LAYER WILL DEEPEN TUE MORNING WITH POSSIBLE DRIZZLE OVER AND W OF THE MOUNTAINS. WARMER SUN THEN COOLER MON WITH MORE COOLING TUE. A FEW HIGH CLOUDS WILL CONTINUE IN SW FLOW ALOFT. SMOKE FROM FIRES SHOULD GRADUALLY BE ON THE DECREASE. && .LONG TERM (WED-SAT)... FLAT WLY FLOW ALOFT AND WEAKER ONSHORE FLOW THROUGH FRI WILL RESULT IN A LITTLE WARMER WEATHER WITH A SHALLOWER MARINE LAYER. WEAK TO MODERATE OFFSHORE FLOW MAY DEVELOP SAT. && .AVIATION... 272000Z...MID AND HIGH LEVEL CLOUDS CONTINUE TO STREAM IN FROM THE SOUTH WITH BASES AROUND 10K FT. TRACE AMOUNTS OF RAIN HAVE BEEN OBSERVED AT MANY AIRPORTS. THERE WERE EVEN A FEW LIGHTNING STRIKES DETECTED OVER THE COASTAL WATERS SOUTHWEST OF KSAN SHORTLY BEFORE 16Z...BUT NOTHING SINCE. VISIBILITY STILL 4-6SM WITH SMOKE AND HAZE IN MOST AREAS. A FAIRLY LARGE SMOKE PLUME FROM THE POOMACHA FIRE CONTINUES TO OBSCURE PORTIONS OF MT PALOMAR AND POINTS NORTHWARD. SOME SMOKE FROM POOMACHA AND OTHER FIRES MAY DRIFT INTO KPSP AND KTRM...REDUCING THE VISIBILITY TO 5-6SM AT TIMES. THE POSSIBILITY OF LIGHT SHOWERS WILL CONTINUE THROUGH THE AFTERNOON THEN DECREASE OVERNIGHT. EXPECT LITTLE IF ANY STRATUS OR FOG SUN MORNING AS WEAK OFFSHORE FLOW DEVELOPS...ALTHOUGH SOME DENSE FOG MAY MOVE INTO THE FAR SOUTH COAST NEAR KSAN AS WEAK ONSHORE TO THE LOWER DESERTS WILL STILL EXIST. && .SGX WATCHES/WARNINGS/ADVISORIES...NONE. && $$ PUBLIC...DVA AVIATION...SCV
AREA FORECAST DISCUSSION
NWS GREEN BAY WI
259 PM CDT SAT OCT 27 2007 .SHORT TERM...TONIGHT AND SUNDAY... SUNNY SKIES ACROSS NE WI THIS AFTN BEHIND THE EXITING COLD FRONT. VERY DRY AIR PRESENT ON SEVERAL TAMDAR SOUNDINGS OVER CNTL AND WRN WI THIS AFTN AND WITH THE STRONG WINDS...ALLOWED DEWPTS TO DROP ACROSS THAT AREA. UPSTREAM...AN INCREASE IN MOISTURE SEEN OVER NRN MN AND SRN ONTARIO ON WV/VIS SAT AND TAMDAR SOUNDINGS...AND IS EXPECTED TO MOVE SE ACROSS WI TONIGHT. PERIOD BEGINS WITH UPPER TROUGH OVER THE WRN GREAT LKS...AND A 115KT JET STREAK ENTERING THE PACIFIC NW BRINGING ZONAL FLOW ACROSS SRN CANADA. H500 TROUGH NEAR CWA AT THIS TIME...AS SEEN ON WV IMAGERY. 12Z NAM/GFS PROG THE TROUGH TO QUICKLY EXIT THE REGION THIS EVENING AND EARLY OVERNIGHT. PRESS GRAD WEAKENS OVER THE REGION LATE THIS AFTN AND EVENING AT THE SFC...CAUSING THE WINDS TO DIMINISH. THE MOISTURE SEEN ON WV AND VIS SAT NEAR THE WEAK SFC TROUGH OVER SWRN ONTARIO IS PICKED UP WELL IN THE MODELS. NAM/GFS INDICATING GOOD MOISTURE BETWEEN H850-700...AND STRONG MID LEVEL LAPSE RATES...WHICH WILL MOVE ACROSS NRN WI THIS EVENING AND OVERNIGHT. WITH THE BEST ENERGY AND MOISTURE ACROSS NRN WI...EXPECTED PARTLY-MOSTLY CLOUDY SKIES OVER NRN WI TONIGHT. IN THE LK EFFECT REGIONS OF NC WI...WINDS AND DELTA T VALUES WILL BECOME FAVORABLE FOR MAYBE A FEW FLURRIES DURING THE LATE EVENING AND OVERNIGHT HOURS...ESPECIALLY ALONG THE WI/MI BORDER. BEHIND THE TROUGH...H500 RIDGE BEGINS TO BUILD OVER THE WRN GREAT LKS FOR SUNDAY. DRIER H850 AIR MOVES IN DURING THE DAY ON SUN...WITH SOME LINGERING H925-850 MOISTURE OVER FAR NE WI. WITH THE COLDER AIR LINGERING OVER FAR NE WI...EXPECT CU TO DEVELOP AND REMAIN OVER THAT AREA THROUGH MOST OF THE DAY. OTHERWISE...THE REST OF CWA SHOULD BE MOSTLY SUNNY. WENT NEAR GUIDANCE VALUES TONIGHT SINCE THERE WAS CONSISTENCY IN THE MOS VALUES AND CLOUD COVER. KEPT EXISTING HIGH FORECAST INTACT FOR SUN...AS STRONG COLD AIR DROPPING S BEHIND THE TROUGH SHOULD KEEP VALUES BELOW MAV GUIDANCE VALUES. .LONG TERM...SUNDAY NIGHT THROUGH NEXT SATURDAY...THE MAIN FCST CONCERNS ARE TEMPS THROUGHOUT THE EXTENDED FCST PERIOD...AND THE EFFECTS OF A COLD FRONT DURING THE MID PART OF NEXT WEEK. NO SIGNIFICANT CHANGES WERE MADE TO THE PREVIOUS FCST. ZONAL FLOW ALOFT WILL CONTINUE THROUGH MOST OF THE PERIOD...WITH A MORE AMPLIFIED PATTERN EXPECTED TOWARD NEXT WEEKEND AS A TROF DEEPENS OVER THE PLAINS. TWO MAIN FRONTAL SYSTEMS ARE FCST TO MOVE THROUGH WI DURING THIS PERIOD...ONE LATE TUES NGT INTO WEDS...AND ANOTHER ON SATURDAY. EXPECT DRY CONDITIONS TO PREVAIL SUNDAY NIGHT THROUGH TUESDAY...WITH ABOVE TO MUCH ABOVE NORMAL TEMPS DUE TO PERSISTENT SW WINDS. MODELS GENERALLY AGREE ON THE TIMING OF THE COLD FRONT PASSAGE LATE TUES NGT INTO WEDS...BUT THERE IS CONSIDERABLE DIFFERENCE ON THE STRENGTH OF THE SFC LOW MOVG THROUGH THE RGN. HPC FAVORS THE LESS AMPLIFIED ECMWF SOLN...BUT THE GFS/CANADIAN/UKMET ARE STRONGER AND MORE AMPLIFIED...SO THERE IS A SIGNIFICANT AMOUNT OF UNCERTAINTY. IF THE MORE AMPLIFIED SOLNS ARE CORRECT...WINDS WILL BE QUITE STG...LEADING TO A MORE PRONOUNCED PUSH OF COLD AIR...AND PERHAPS A QUICKER CHANGEOVER TO A RAIN/SNOW MIX WEDS AFTERNOON. FOR NOW... WILL GO WITH A MIDDLE OF THE ROAD APPROACH...WITH A BLUSTERY DAY ON WEDNESDAY...AND NO MENTION OF SNOW UNTIL WEDS NGT...WHEN LAKE- EFFECT SNOW SHOWERS ARE PSBL IN NC WI. HIGH PRESSURE WILL BUILD BACK INTO THE RGN LATE WEDS NGT INTO THURSDAY...AND LINGER INTO FRIDAY. TEMPS ARE EXPECTED TO COOL BACK TO NEAR NORMAL LEVELS. MODELS HAVE SLOWED DOWN THE PROGRESSION OF THE NEXT UPPER TROF AND SFC COLD FRONT NEXT WEEKEND. WILL HOLD OFF ON PCPN CHCS UNTIL SATURDAY. && .AVIATION...VFR CONDITIONS ARE EXPECTED ACROSS NE WI FOR MOST OF THE PERIOD. APPROACHING SCT-BKN 4-6KFT OVER NE MN AND SWRN ONTARIO WILL SWING SE ACROSS NRN WI TONIGHT. THERE MAY BE A FEW CEILINGS APPROACHING MVFR CONDITIONS NEAR THE WI/MI BORDER DURING THE OVERNIGHT PERIOD...AS WINDS BECOME FAVORABLE FOR LK ENHANCED CLOUDS AND MAYBE A FEW FLURRIES. && .MARINE...SCA WINDS ARE EXPECTED TO DIMINISH DURING THE EVENING HOURS AS SFC PRESSURE GRADIENT AND STRONGER H925-850 WINDS PUSH EAST OF THE REGION. CURRENT TIMING LOOKS GOOD FOR THE END OF THE SCA. && .GRB WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SRF/KIECKBUSCH
AREA FORECAST DISCUSSION
NWS LA CROSSE WI
230 PM CDT SAT OCT 27 2007 .SHORT TERM...THROUGH TUESDAY NIGHT FORECAST CONCERNS WERE PRIMARILY FOCUSED ON TEMPERATURES. AFTERNOON SURFACE ANALYSIS HAD HIGH PRESSURE OVER THE PLAINS. DRY AIR MASS SITUATED ACROSS THE UPPER MISSISSIPPI VALLEY...WITH DEW POINTS MAINLY IN THE 20S. WATER VAPOR IMAGERY IN CONJUNCTION WITH ACARS AND RAOB UPPER AIR DATA INDICATED FLOW SHIFTING TO ZONAL PATTERN ACROSS THE NORTHERN PART OF THE NATION. FORECAST CONFIDENCE WAS HIGH THROUGH TUESDAY...AS DETERMINISTIC AND PROBABILISTIC DATA SUITE WERE IN GOOD AGREEMENT ON OVERALL UPPER LEVEL AND SURFACE FEATURES. AS A RESULT...DRY WEATHER EXPECTED TO CONTINUE THROUGH THE EARLY PART OF THE WEEK...ALONG WITH AN UPWARD TREND IN TEMPERATURES. TONIGHT...EXCELLENT RADIATIONAL COOLING ANTICIPATED...WITH DRY AIR... LIGHT WINDS AND FEW CLOUDS. THUS...ONE OF THE COLDEST NIGHTS OF THE SEASON EXPECTED. OVERNIGHT LOWS SHOULD GENERALLY BE IN THE UPPER 20S TO THE LOWER 30S...ALTHOUGH LOCALLY COLDER READINGS WILL OCCUR IN SUCH LOCATIONS AS KCMY AND KVOK. SUNDAY THROUGH TUESDAY...RISING 850MB TEMPERATURES IN LOW LEVEL WARM AIR ADVECTION SUPPORT TEMPERATURES ON AN UPWARD TREND. THIS SHOULD ESPECIALLY BE TRUE ON TUESDAY...AS 850MB READINGS FORECAST TO REACH 10C-12C BY 00Z 31OCT07. MAIN IMPACT ON THE CURRENT DATA BASE WAS TO TREND MAXIMUM AND MINIMUM TEMPERATURES UPWARD. TUESDAY NIGHT...BULK OF FORCING SHOULD BE ACROSS SOUTHERN CANADA... WHERE MAIN UPPER LEVEL AND SURFACE WAVE WILL BE LOCATED. WITH SURFACE FRONT SITUATED WELL TO THE WEST OF THE FORECAST AREA...LOW-END RAIN CHANCES WERE PUSHED BACK UNTIL AFTER MIDNIGHT. .LONG TERM...WEDNESDAY THROUGH SATURDAY WEDNESDAY...OPERATIONAL ECMWF AND GFS HAVE COME INTO BETTER AGREEMENT ON UPPER LEVEL AND SURFACE WAVE ADVANCING ACROSS THE UPPER MISSISSIPPI VALLEY. CONSISTENT SIGNAL IN THE MODELS SUPPORTED BEST DYNAMICS ASSOCIATED WITH PARENT SURFACE AND UPPER LEVEL WAVE MOVING ACROSS SOUTHERN CANADA. THEREFORE...FORECAST CONFIDENCE WAS FAIRLY HIGH IN MAINTAINING JUST A LOW-END RAIN CHANCE PER CURRENT DATA BASE...SINCE FORCING APPEARS WEAK AND MOISTURE LIMITED. FRIDAY INTO SATURDAY...ANOTHER SURFACE AND UPPER LEVEL WAVE SHOULD IMPACT THE FORECAST AREA IN THIS TIME FRAME. OPERATIONAL ECMWF AND GFS HAVE BEEN AT ODDS WITH REGARDS TO EVOLUTION AND PROGRESSION OF THIS FEATURE...ALTHOUGH DPROG/DT IN BOTH MODELS SUPPORTS SLOWER PROGRESSION ON FRIDAY. THUS...FORECAST CONFIDENCE WAS HIGH ENOUGH TO SLOW ONSET OF PRECIPITATION CHANCES UNTIL FRIDAY NIGHT. ECMWF WAS MORE PROGRESSIVE WITH SYSTEM INTO SATURDAY...EVEN THOUGH ECMWF JOINED GFS IN SUPPORTING MID LEVEL LOW CLOSING OFF OVER THE CENTER PART OF THE NATION. FORECAST CONFIDENCE IN DETAILS OBVIOUSLY NOT HIGH AT THIS TIME...BUT OPERATIONAL AND PROBABILISTIC DATA SUITE SUGGEST A CHANCE OF PRECIPITATION WARRANTED ON SATURDAY. && .AVIATION... HIGH PRESSURE WILL BUILD INTO THE AREA THIS EVENING AND WILL SETTLE ACROSS THE AREA THROUGH SUNDAY. THIS WILL PROVIDE MOSTLY CLEAR SKIES AND DIMINISHING WINDS AT KRST/KLSE TAF SITES. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...NONE. MN...NONE. IA...NONE. && $$ SHORT/LONG TERM...THOMPSON AVIATION..........DAS