Forecast Discussions mentioning "ACARS", "MDCRS", "AIRCRAFT", "TAMDAR", or "AMDAR" received at FSL on 04/03/07

AREA FORECAST DISCUSSION
NWS SAN DIEGO CA
930 PM PDT MON APR 2 2007 .SYNOPSIS... THE MARINE LAYER AND ONSHORE FLOW WILL CAUSE COASTAL LOW CLOUDS AND FOG IN THE NIGHTS AND MORNINGS...EXTENDING LOCALLY INLAND. OTHERWISE...FAIR EXCEPT FOR VARIABLE HIGH CLOUDINESS. WARMER LATE THIS WEEK INTO EARLY NEXT WEEK AS HIGH PRESSURE BUILDS. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES. .SHORT TERM (TONIGHT-THU)... STRATUS WAS MOVING INLAND THIS EVENING AND THERE WAS VARIABLE HIGH CLOUDINESS. THE 00Z NKX SOUNDING HAD AN INVERSION BASED NEAR 1700 FT...ABOUT 400 FT HIGHER THAN 24 HOURS PREVIOUS. THE SOUNDING ALSO SHOWED THE HIGH LEVEL MOISTURE IN WLY WINDS ALOFT. STRONG ONSHORE FLOW WITH 6-7 MB SAN-IPL. RELATIVELY MINOR CHANGES THROUGH THE SHORT TERM WITH WEAK RIDGING THROUGH WED GIVING WAY TO A WEAK SHORT WAVE TROUGH THU. THE ONSHORE FLOW AND A WEAK INTERMITTENT EDDY WILL CONTINUE COASTAL LOW CLOUDS AND FOG IN THE NIGHTS AND MORNINGS...EXTENDING LOCALLY INLAND LATE AT NIGHT. HIGH CLOUDS WILL INCREASE WED INTO THU IN SW FLOW ALOFT RESULTING IN PARTLY CLOUDY SKIES ABOVE THE MARINE LAYER. ONSHORE GRADIENTS WILL CAUSE LOCALLY BREEZY CONDITIONS...MAINLY IN THE MOUNTAINS AND DESERTS DURING THE AFTERNOONS AND EVENINGS. ONLY MINOR LOCAL COOLING EXPECTED WED AND THU. .LONG TERM (FRI-MON)... UPPER RIDGING SHOULD PREVAIL LATE THIS WEEK INTO EARLY NEXT WEEK. THIS WILL CAUSE A SHALLOWER MARINE LAYER. OTHERWISE...FAIR AND WARMER WITH A FEW HIGH CLOUDS AT TIMES. && .AVIATION... 030300Z...ACARS SOUNDINGS SHOWED THE MARINE INVERSION AROUND 1400 FEET. THE WEAK EDDY SHOULD CONTINUE OVERNIGHT AND DEEPEN THE MARINE LAYER A FEW HUNDRED FEET. THIS...PLUS A RAPID INCREASE IN DEW POINTS IN THE VALLEYS...SHOULD RESULT IN STRATUS AND FOG SPREADING INTO W AND S PARTS OF THE INLAND EMPIRE BY SUNRISE TUE. FOR THIS EVENING...COASTAL AREAS WILL SEE STRATUS INCREASING...WITH BASES AROUND 1300-1500 FT MSL. ONLY LOCAL IFR/LIFR VSBYS ARE EXPECTED LATE TONIGHT...MAINLY IN THE 1300-1800 FT MSL RANGE. CLEARING SHOULD OCCUR TUE IN MOST AREAS BETWEEN 17 AND 18Z...BUT LINGERING STRATUS WILL BE POSSIBLE NEAR THE BEACHES IN THE AFTERNOON. ABOVE THE MARINE LAYER...HIGH CLOUDS WILL DRIFT BY THROUGH TUE MORNING...BUT VFR CONDITIONS FOR VSBYS/CIGS WILL DOMINATE THROUGH TUE. && .SGX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ PUBLIC...DVA AVIATION...MAXWELL
SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION...UPDATED AVN
NWS LOS ANGELES/OXNARD CA
1100 AM PDT SUN APR 1 2007 .SHORT TERM... CURRENT SATELLITE IMAGERY SHOWING LOW CLOUDS AND FOG RETURNING TO MOST COASTAL LOCATIONS THIS MORNING...LOCALLY EXTENDING INTO THE SAN GABRIEL VALLEY. INITIALLY MARINE INVERSION WAS BELOW 1000 FEET LAST NIGHT...AND FOG WAS DENSE IN SOME LOCATIONS...PROMPTING THE ISSUANCE OF A DENSE FOG ADVISORY. LATEST ACARS DATA AND PILOT REPORTS OVER THE LA BASIN INDICATE THE MARINE LAYER HAS DEEPENED TO AROUND 1300 FEET AS OF 8 AM. WITH VISIBILITIES SLOWLY IMPROVING...WILL GO AHEAD AND CANCEL DENSE FOG ADVISORY IN MORNING UPDATE. WITH UPPER LEVEL FLOW BECOMING MORE ZONAL TODAY...THIS WILL RESULT IN PRESSURE GRADIENTS TRENDING ONSHORE TODAY. THIS IN COMBINATION WITH A FAIRLY STRONG MARINE INVERSION WILL LIKELY CAUSE SOME LOW CLOUDS AND FOG TO LINGER NEAR THE BEACHES TODAY. AS A RESULT...HAVE INDICATED MORE PESSIMISTIC CLEARING IN MORNING UPDATE...ALONG WITH COOLER TEMPERATURES ALONG THE COASTAL PLAIN. LOOK FOR ANOTHER WARM DAY ABOVE THE MARINE INVERSION IN THE VALLEYS...MOUNTAINS...AND DESERTS. *** FROM PREVIOUS DISCUSSION *** AN INCREASING NORTH GRADIENT TONIGHT SHOULD KEEP THE SOUTHERN SBA COAST CLEAR BUT THATS ABOUT IT ALL OTHER COASTAL SITES SHOULD HAVE CLOUDS NOT MUCH LIFT AND THE VALLEYS SHOULD NOT SEE MUCH IF ANY MARINE CLOUDS. ANY CLOUDS MONDAY WILL DISSIPATE BY LATE MORNING AND SKIES SHOULD BE SUNNY FOR THE AFTERNOON. A LITTLE BREEZY IN THE ANTELOPE VALLEY. NORTH WINDS INCREASE SOME MONDAY NIGHT AND A MODERATE SUNDOWNER IS POSSIBLE FOR SOUTHER SBA COUNTY AND THE I-5 CORRIDOR WILL ALSO LIKELY SEE SOME MODERATE WINDS. THESE NORTH PUSH WILL KEEP THE SBA SOUTH COAST CLEAR...SMALL EDDY IS FORECAST FOR LA AND VTA COUNTIES AND HAVE SOME MARINE CLOUDS THERE BUT CONFIDENCE IS NOT TOO HIGH. LITTLE RIDGE POPS UP TUESDAY. ONSHORE FLOW WEAKENS SOME AND BURN OFF SHOULD BE QUICKER AND THIS SHOULD LEAD TO A LITTLE WARM UP. .LONG TERM... EXTENDED PROGS BRING A TROF THROUGH THE AREA WED AND THU AND THIS SHOULD CREATE A NICE MARINE LAYER WEDNESDAY BUT THE COLD AIR AND MIXING SHOULD DISSIPATE THE MARINE CLOUDS THURSDAY. A RIDGE PUNCHES INTO THE AREA FRIDAY AND LASTS TIL SATURDAY. OFFSHORE FLOW INCREASES AND THIS SHOULD KEEP THE MARINE CLOUDS AT BAY AND ALLOW FOR A NICE JUMP IN TEMPS. DID NOT RADICALLY JUMP THE TEMPS AND WILL SEE IF THIS IS AN ANOMALY OR AN ACTUAL TREND. && .AVIATION...AT 18Z...OR 11 AM PDT...MARINE LAYER WAS AROUND 1.3KFT DEEP WITH A LITTLE STRONGER EDDY THEN SUGGESTED BY GUIDANCE. LOW CLOUD FIELD WAS ORGANIZED NORTH OF POINT DUME AND DISORGANIZED SOUTH. EXPECT THE LOW CLOUDS TO LINGER NEAR SHORE THROUGH EARLY AFTERNOON. MARINE DEPTH WILL REMAIN AT PRESENT DEPTH OR ASCEND A COUPLE HUNDRED FEET OVERNIGHT AS THE EDDY STRENGTHENS. UNCERTAIN ON CIGS/VSBY AS WELL AS THE RETURN AT KLAX. HAVE ADJUSTED MOS AS WELL AS PREVIOUS TAFS TIMING UP AND CIGS/VSBY LOWER. WILL CONTINUE WITH LOW CIGS/VSBY PUSHING OVER THE SAN FERNANDO VALLEY THOUGH PUSHED TIMING BACK AS WELL AS LOWER CIGS/VSBY FROM PREVIOUS TAFS. && .LOX WATCHES/WARNINGS/ADVISORIES... SMALL CRAFT ADVISORY (SEE LAXCWFLOX). && $$ PUBLIC...GOMBERG/RORKE AVIATION...FORWOOD WWW.WEATHER.GOV/LOSANGELES
SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NWS LOS ANGELES/OXNARD CA
930 AM PDT SUN APR 1 2007 .SHORT TERM... CURRENT SATELLITE IMAGERY SHOWING LOW CLOUDS AND FOG RETURNING TO MOST COASTAL LOCATIONS THIS MORNING...LOCALLY EXTENDING INTO THE SAN GABRIEL VALLEY. INITIALLY MARINE INVERSION WAS BELOW 1000 FEET LAST NIGHT... AND FOG WAS DENSE IN SOME LOCATIONS...PROMPTING THE ISSUANCE OF A DENSE FOG ADVISORY. LATEST ACARS DATA AND PILOT REPORTS OVER THE LA BASIN INDICATE THE MARINE LAYER HAS DEEPENED TO AROUND 1300 FEET AS OF 8 AM. WITH VISIBILITIES SLOWLY IMPROVING...WILL GO AHEAD AND CANCEL DENSE FOG ADVISORY IN MORNING UPDATE. WITH UPPER LEVEL FLOW BECOMING MORE ZONAL TODAY...THIS WILL RESULT IN PRESSURE GRADIENTS TRENDING ONSHORE TODAY. THIS IN COMBINATION WITH A FAIRLY STRONG MARINE INVERSION WILL LIKELY CAUSE SOME LOW CLOUDS AND FOG TO LINGER NEAR THE BEACHES TODAY. AS A RESULT...HAVE INDICATED MORE PESSIMISTIC CLEARING IN MORNING UPDATE...ALONG WITH COOLER TEMPERATURES ALONG THE COASTAL PLAIN. LOOK FOR ANOTHER WARM DAY ABOVE THE MARINE INVERSION IN THE VALLEYS...MOUNTAINS...AND DESERTS. *** FROM PREVIOUS DISCUSSION *** AN INCREASING NORTH GRADIENT TONIGHT SHOULD KEEP THE SOUTHERN SBA COAST CLEAR BUT THATS ABOUT IT ALL OTHER COASTAL SITES SHOULD HAVE CLOUDS NOT MUCH LIFT AND THE VALLEYS SHOULD NOT SEE MUCH IF ANY MARINE CLOUDS. ANY CLOUDS MONDAY WILL DISSIPATE BY LATE MORNING AND SKIES SHOULD BE SUNNY FOR THE AFTERNOON. A LITTLE BREEZY IN THE ANTELOPE VALLEY. NORTH WINDS INCREASE SOME MONDAY NIGHT AND A MODERATE SUNDOWNER IS POSSIBLE FOR SOUTHER SBA COUNTY AND THE I-5 CORRIDOR WILL ALSO LIKELY SEE SOME MODERATE WINDS. THESE NORTH PUSH WILL KEEP THE SBA SOUTH COAST CLEAR...SMALL EDDY IS FORECAST FOR LA AND VTA COUNTIES AND HAVE SOME MARINE CLOUDS THERE BUT CONFIDENCE IS NOT TOO HIGH. LITTLE RIDGE POPS UP TUESDAY. ONSHORE FLOW WEAKENS SOME AND BURN OFF SHOULD BE QUICKER AND THIS SHOULD LEAD TO A LITTLE WARM UP. .LONG TERM... EXTENDED PROGS BRING A TROF THROUGH THE AREA WED AND THU AND THIS SHOULD CREATE A NICE MARINE LAYER WEDNESDAY BUT THE COLD AIR AND MIXING SHOULD DISSIPATE THE MARINE CLOUDS THURSDAY. A RIDGE PUNCHES INTO THE AREA FRIDAY AND LASTS TIL SATURDAY. OFFSHORE FLOW INCREASES AND THIS SHOULD KEEP THE MARINE CLOUDS AT BAY AND ALLOW FOR A NICE JUMP IN TEMPS. DID NOT RADICALLY JUMP THE TEMPS AND WILL SEE IF THIS IS AN ANOMALY OR AN ACTUAL TREND. && .AVIATION...01/1230Z... N OF POINT CONCEPTION...MARINE LAYER HAS FORMED WITH ALL COASTAL SITES KOXR AND NORTH EXPERIENCING LIFR CIGS AND VSBYS...MOST WITH VSBYS AOB 1SM AND CIGS BLO 003. SOUTH OF KOXR...AIRFIELDS HAVE IFR CIGS NEAR 007 AND VSBYS 4-6SM. THIS SHOULD SLOWLY LIFT AFTER SUNRISE AND BURN OFF BY 18Z...AFTER WHICH CLEAR SKIES AND UNRESTRICTED VSBYS SHOULD TAKE OVER. A NORMAL SEABREEZE SHOULD PICK UP BY 20Z. EXPECT A RETURN OF IFR CIGS AND VSBYS BETWEEN 8-10Z TONIGHT. KLAX HAS IFR CIGS AT 007 WHICH SHOULD LIFT BY 15Z. OTHERWISE...CLEAR SKIES AND A USUAL SEABREEZE AROUND 12 KTS WILL TAKE OVER BY 20Z. LIFR TO IFR CIGS SHOULD RETURN AROUND 08-10 TONIGHT. && .LOX WATCHES/WARNINGS/ADVISORIES... SMALL CRAFT ADVISORY (SEE LAXCWFLOX). && $$ PUBLIC...GOMBERG/RORKE AVIATION...MEIER WWW.WEATHER.GOV/LOSANGELES
SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION...UPDATED
NWS LOS ANGELES/OXNARD CA
530 AM PDT SUN APR 1 2007 ...UPDATED AVIATION SECTION... .SHORT TERM... EC AND GFS IN GOOD AGREEMENT FOR NEXT 7 DAYS. FAIRLY HIGH CONFIDENCE IN SYNOPTIC PATTERN. CURRENT MARINE LAYER STRUGGLING SOMEWHAT TO FORM. 09Z ACARS PEGS MARINE LAYER AT 850 FEET WHICH AGREES WELL WITH KLAX CIG AT 007 LOWER CIGS AND LOCAL DENSE FOG ACROSS VENTURA COUNTY SUGGEST MARINE LAYER IS LOWER THERE. THERE WILL BE SOME SORT OF MARINE CLOUDINESS ACROSS ALL THE COASTAL SXNS BY DAWN. NOT MUCH OF AN EDDY AND ONSHORE PUSH ONLY PLUS 3.5MB SO CLEARING SHOULD BE OK. AN INCREASING NORTH GRADIENT TONIGHT SHOULD KEEP THE SOUTHERN SBA COAST CLEAR BUT THATS ABOUT IT ALL OTHER COASTAL SITES SHOULD HAVE CLOUDS NOT MUCH LIFT AND THE VALLEYS SHOULD NOT SEE MUCH IF ANY MARINE CLOUDS. ANY CLOUDS MONDAY WILL DISSIPATE BY LATE MORNING AND SKIES SHOULD BE SUNNY FOR THE AFTERNOON. A LITTLE BREEZY IN THE ANTELOPE VALLEY. NORTH WINDS INCREASE SOME MONDAY NIGHT AND A MODERATE SUNDOWNER IS POSSIBLE FOR SOUTHER SBA COUNTY AND THE I-5 CORRIDOR WILL ALSO LIKELY SEE SOME MODERATE WINDS. THESE NORTH PUSH WILL KEEP THE SBA SOUTH COAST CLEAR...SMALL EDDY IS FORECAST FOR LA AND VTA COUNTIES AND HAVE SOME MARINE CLOUDS THERE BUT CONFIDENCE IS NOT TOO HIGH. LITTLE RIDGE POPS UP TUESDAY. ONSHORE FLOW WEAKENS SOME AND BURN OFF SHOULD BE QUICKER AND THIS SHOULD LEAD TO A LITTLE WARM UP. .LONG TERM... EXTENDED PROGS BRING A TROF THROUGH THE AREA WED AND THU AND THIS SHOULD CREATE A NICE MARINE LAYER WEDNESDAY BUT THE COLD AIR AND MIXING SHOULD DISSIPATE THE MARINE CLOUDS THURSDAY. A RIDGE PUNCHES INTO THE AREA FRIDAY AND LASTS TIL SATURDAY. OFFSHORE FLOW INCREASES AND THIS SHOULD KEEP THE MARINE CLOUDS AT BAY AND ALLOW FOR A NICE JUMP IN TEMPS. DID NOT RADICALLY JUMP THE TEMPS AND WILL SEE IF THIS IS AN ANOMALY OR AN ACTUAL TREND. && .AVIATION...01/1230Z... N OF POINT CONCEPTION...MARINE LAYER HAS FORMED WITH ALL COASTAL SITES KOXR AND NORTH EXPERIENCING LIFR CIGS AND VSBYS...MOST WITH VSBYS AOB 1SM AND CIGS BLO 003. SOUTH OF KOXR...AIRFIELDS HAVE IFR CIGS NEAR 007 AND VSBYS 4-6SM. THIS SHOULD SLOWLY LIFT AFTER SUNRISE AND BURN OFF BY 18Z...AFTER WHICH CLEAR SKIES AND UNRESTRICTED VSBYS SHOULD TAKE OVER. A NORMAL SEABREEZE SHOULD PICK UP BY 20Z. EXPECT A RETURN OF IFR CIGS AND VSBYS BETWEEN 8-10Z TONIGHT. KLAX HAS IFR CIGS AT 007 WHICH SHOULD LIFT BY 15Z. OTHERWISE...CLEAR SKIES AND A USUAL SEABREEZE AROUND 12 KTS WILL TAKE OVER BY 20Z. LIFR TO IFR CIGS SHOULD RETURN AROUND 08-10 TONIGHT. && .LOX WATCHES/WARNINGS/ADVISORIES... SMALL CRAFT ADVISORY (SEE LAXCWFLOX). && $$ PUBLIC...RORKE AVIATION...MEIER WWW.WEATHER.GOV/LOSANGELES
SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NWS LOS ANGELES/OXNARD CA
320 AM PDT SUN APR 1 2007 .SHORT TERM... EC AND GFS IN GOOD AGREEMENT FOR NEXT 7 DAYS. FAIRLY HIGH CONFIDENCE IN SYNOPTIC PATTERN. CURRENT MARINE LAYER STRUGGLING SOMEWHAT TO FORM. 09Z ACARS PEGS MARINE LAYER AT 850 FEET WHICH AGREES WELL WITH KLAX CIG AT 007 LOWER CIGS AND LOCAL DENSE FOG ACROSS VENTURA COUNTY SUGGEST MARINE LAYER IS LOWER THERE. THERE WILL BE SOME SORT OF MARINE CLOUDINESS ACROSS ALL THE COASTAL SXNS BY DAWN. NOT MUCH OF AN EDDY AND ONSHORE PUSH ONLY PLUS 3.5MB SO CLEARING SHOULD BE OK. AN INCREASING NORTH GRADIENT TONIGHT SHOULD KEEP THE SOUTHERN SBA COAST CLEAR BUT THATS ABOUT IT ALL OTHER COASTAL SITES SHOULD HAVE CLOUDS NOT MUCH LIFT AND THE VALLEYS SHOULD NOT SEE MUCH IF ANY MARINE CLOUDS. ANY CLOUDS MONDAY WILL DISSIPATE BY LATE MORNING AND SKIES SHOULD BE SUNNY FOR THE AFTERNOON. A LITTLE BREEZY IN THE ANTELOPE VALLEY. NORTH WINDS INCREASE SOME MONDAY NIGHT AND A MODERATE SUNDOWNER IS POSSIBLE FOR SOUTHER SBA COUNTY AND THE I-5 CORRIDOR WILL ALSO LIKELY SEE SOME MODERATE WINDS. THESE NORTH PUSH WILL KEEP THE SBA SOUTH COAST CLEAR...SMALL EDDY IS FORECAST FOR LA AND VTA COUNTIES AND HAVE SOME MARINE CLOUDS THERE BUT CONFIDENCE IS NOT TOO HIGH. LITTLE RIDGE POPS UP TUESDAY. ONSHORE FLOW WEAKENS SOME AND BURN OFF SHOULD BE QUICKER AND THIS SHOULD LEAD TO A LITTLE WARM UP. .LONG TERM... EXTENDED PROGS BRING A TROF THROUGH THE AREA WED AND THU AND THIS SHOULD CREATE A NICE MARINE LAYER WEDNESDAY BUT THE COLD AIR AND MIXING SHOULD DISSIPATE THE MARINE CLOUDS THURSDAY. A RIDGE PUNCHES INTO THE AREA FRIDAY AND LASTS TIL SATURDAY. OFFSHORE FLOW INCREASES AND THIS SHOULD KEEP THE MARINE CLOUDS AT BAY AND ALLOW FOR A NICE JUMP IN TEMPS. DID NOT RADICALLY JUMP THE TEMPS AND WILL SEE IF THIS IS AN ANOMALY OR AN ACTUAL TREND. && .AVIATION... WILL BE ISSUED SHORTLY AFTER 12Z TAFS. && .LOX WATCHES/WARNINGS/ADVISORIES... SMALL CRAFT ADVISORY (SEE LAXCWFLOX). && $$ PUBLIC...RORKE AVIATION...MEIER WWW.WEATHER.GOV/LOSANGELES
AREA FORECAST DISCUSSION
NWS NORTHERN INDIANA
839 AM EDT SUN APR 1 2007 .UPDATE... OCCLUDED LOW PRESSURE SYSTEM NEAR SW MN THIS MORNING WILL ROTATE NE TO A POSITION NEAR WRN LAKE SUPERIOR BY THIS EVENING. A TIGHTENING SFC PRESSURE GRADIENT BEHIND THIS SYSTEM WILL BRING WINDY CONDITIONS TO OUR REGION THIS AFTERNOON. FURTHERMORE...ATMOSPHERE WILL BECOME ADIABATICALLY MIXED THROUGH 6 TO 7 KFT. AS THIS HAPPENS...STRONGER WINDS ALOFT WILL BE TRANSFERRED DOWN TO THE SFC. LATEST NAM-WRF AND RUC INDICATE THAT 40 KNOT WINDS WILL DEVELOP NEAR 925 MB THIS AFTERNOON WITH 50 KNOTS POSSIBLE AT 850 MB. IN FACT...THE WINCHESTER..IL PROFILER THIS MORNING WAS SHOWING NEAR 50 KNOT WINDS AT 925 MB AND 850 MB AS WELL AS THE LINCOLN 12Z SOUNDING. WILL HOIST A WIND ADVISORY FOR THE ENTIRE REGION FOR THE AFTERNOON/EARLY EVENING HOURS WITH GUSTS FROM 45 MPH TO 55 MPH POSSIBLE. && .PREV DISCUSSION... /ISSUED 637 AM EDT SUN APR 1 2007/ AVIATION/UPDATE... DRY SLOT WAS MOVG ACROSS NRN INDIANA EARLY THIS MORNING WITH MID CLOUD DECK MOVG FAIRLY QUICKLY EAST ACROSS NRN IL ATTM. THESE CLOUDS AND SOME CU EXPECTED AT THE TERMINALS BY LATE MORNING. PROFILER/VWP/TAMDAR AROUND THE REGION SHOWING 30-40KT WINDS IN THE 2-4KFT LAYER. WITH DIURNAL HEATING THESE STRONGER WINDS WILL MIX DOWN TO THE SFC IN GUSTS THIS AFTN. SECONDARY CDFNT OVER ERN IA WILL MOVE EAST INTO NRN INDIANA LATE THIS AFTN AND COMBINED WITH DAYTIME HEATING AND RESULTANT WK INSTABILITY SHOULD TRIGGER SCT SHOWERS AND TSTMS. GIVEN THE MARGINAL INSTABILITY AND OVERALL LIMITED MOISTURE, OPTED TO JUST EMPLOY VCTS FOR A FEW HRS THIS AFTN ATTM. WITH PASSAGE OF SECONDARY FRONT THIS EVE, WINDS SHOULD STAY UP MOST OF THE NIGHT WITH CYCLONIC FLOW RESULTING IN SOME LINGERING SHOWERS IN THE EVE AND PRBLY VFR CIGS MUCH OF THE NIGHT. UPDATE... WILL UPDATE ZFP/GRIDS SHORTLY TO REMOVE EARLY MORNING WORDING AS SHOWERS HAVE ALREADY MOVED OUT OF THE CWA. PREV DISCUSSION... /ISSUED 444 AM EDT SUN APR 1 2007/ SHORT TERM... CDFNT/DRY SLOT PRECEEDED BY LARGE AREA OF SHOWERS WAS MOVG E/35KT ACROSS INDIANA THIS MORNING AND APPEARS IT WILL MOVE EAST OF OUR CWA BY 12Z. CARRIED SHOWERS ENDING PREDAWN ACROSS ERN ZONES TO ACCOUNT FOR THIS. CLEAR AREA OVER IL WILL OVERSPREAD THE CWA THIS MORNING. SFC DEWPOINTS IN IL BEHIND THE CDFNT ARE GENERALLY IN THE 40S. STRONG DAYTIME HEATING TODAY WILL RESULT IN WK INSTABILITY DVLPG BUT CAPE WILL EXTEND FROM THE FREEZING LEVEL UP THROUGH -20C. WITH HIGH CLOUD BASES AND RELATIVELY DRY SUB-CLOUD LAYER... GOOD POTENTIAL FOR DOWNWARD MIXING OF AIR IN ANY SHOWERS/TSTMS THAT DVLP THIS AFTN AND ALSO WILL BE CONDUCIVE FOR AT LEAST SOME SMALL HAIL. OTHER CONCERN TODAY IS GENERAL STRONG WIND GUSTS THIS AFTN AS NAM12/GFS FCST SOUNDINGS ON BUFKIT CONTINUING TO SUGGEST WINDS AROUND 35KTS WILL MIX DOWN TO THE SFC. SOME WRAP AROUND LOW CLOUDS AND LIGHT SHOWERS POSSIBLE THIS EVENING ACROSS N-NE PORTION OF CWA. WINDS SHOULD STAY UP OVERNIGHT LIMITING DIURNAL COOLING AND RAISED OUR GOING MINS SLIGHTLY WITH THE EXCEPTION OF SW MI WHICH WILL HAVE WINDS TURNING IN OFF THE LAKE. /ISSUED 444 AM EDT SUN APR 1 2007/ LONG TERM... MONDAY THROUGH SATURDAY...MAIN CONCERNS THIS PERIOD ARE THE CHANCES FOR SEVERE WEATHER TUESDAY AFTERNOON/EARLY TUESDAY NIGHT AND THE AMOUNT OF COLD AIR SPREADING INTO THE REGION DURING THE SECOND HALF OF THE WEEK. SEVERAL FACTORS COMING TOGETHER FOR A ROUND OF SEVERE WEATHER LATE IN THE DAY TUESDAY AND TUESDAY NIGHT. MOISTURE WILL SURGE BACK INTO THE AREA TUESDAY AHEAD A STRONG AND FAST MOVING COLD FRONT. THE 00Z GFS ENSEMBLES HAVE COME INTO EVEN BETTER AGREEMENT WITH THE TRACK OF THE LOW AND THE TIMING OF THE ASSOCIATED FRONT. THE FRONT SHOULD MOVE INTO THE AREA LATE IN THE AFTERNOON OR EARLY EVENING...DURING THE MOST FAVORABLE DIURNAL TIME FOR CONVECTION. FORECAST CAPE VALUES STILL SHOWING QUITE A SPREAD...BUT GENERALLY IN THE 1500 TO 2500 J/KG RANGE. AN UPPER LEVEL JET OF OVER 120 KNOTS SHOULD ALSO HELP SUPPORT SEVERE STORMS. THEREFORE...HAVE RAISED STORM CHANCES EARLY TUESDAY NIGHT OVER MOST AREAS. LARGE HAIL...DAMAGING WINDS AND EVEN TORNADOES POSSIBLE. FOR THE REST OF THE WEEK...A STRONG COLD FRONT WILL MOVE ACROSS THE AREA TUESDAY NIGHT. THE GFS AND THE ECMWF PATTERN INDICATE AN EXTENDED COLD PERIOD WITH TEMPERATURES REMAINING WELL BELOW NORMAL AS A TROF DEEPENS OVER THE MIDWEST. RECORD LOW TEMPERATURES AT SBN ARE BASICALLY IN THE 15F TO 20F RANGE. THE 01/00Z MEX HAS A LOW OF 16F AT SBN SATURDAY MORNING. PROBABLY WILL NEED SNOW COVER TO GET THAT COLD. LOWS OF 22F TO 26F SEEM FAVORABLE. FURTHERMORE...THE GFS MAY NOT BE MODERATING THE COLD AIR ENOUGH. THE 00Z ECMWF IS ABOUT 3C TO 4C WARMER THAN THE 12Z RUN...SO TAKING ALL OF THIS INTO ACCOUNT .HAVE TRENDED MOST TEMPERATURES DURING THE 2ND HALF OF THE WEEK DOWN. CONCERN FOR VEGETATION GROWTH AND DEVELOPMENT AHEAD OF THE NORMAL GROWTH FOR THIS TIME OF YEAR AS TEMPERATURES WILL DROP WELL BELOW FREEZING FOR SEVERAL NIGHTS THIS COMING WEEK. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...NONE. MI...NONE. OH...NONE. LM...SMALL CRAFT ADVISORY UNTIL 8 AM EDT MONDAY FOR LMZ043-046. && $$ UPDATE...HICKMAN/TAYLOR SHORT TERM/AVIATION...TAYLOR LONG TERM...SKIPPER
AREA FORECAST DISCUSSION
NWS NORTHERN INDIANA
637 AM EDT SUN APR 1 2007 .AVIATION/UPDATE... DRY SLOT WAS MOVG ACROSS NRN INDIANA EARLY THIS MORNING WITH MID CLOUD DECK MOVG FAIRLY QUICKLY EAST ACROSS NRN IL ATTM. THESE CLOUDS AND SOME CU EXPECTED AT THE TERMINALS BY LATE MORNING. PROFILER/VWP/TAMDAR AROUND THE REGION SHOWING 30-40KT WINDS IN THE 2-4KFT LAYER. WITH DIURNAL HEATING THESE STRONGER WINDS WILL MIX DOWN TO THE SFC IN GUSTS THIS AFTN. SECONDARY CDFNT OVER ERN IA WILL MOVE EAST INTO NRN INDIANA LATE THIS AFTN AND COMBINED WITH DAYTIME HEATING AND RESULTANT WK INSTABILITY SHOULD TRIGGER SCT SHOWERS AND TSTMS. GIVEN THE MARGINAL INSTABILITY AND OVERALL LIMITED MOISTURE, OPTED TO JUST EMPLOY VCTS FOR A FEW HRS THIS AFTN ATTM. WITH PASSAGE OF SECONDARY FRONT THIS EVE, WINDS SHOULD STAY UP MOST OF THE NIGHT WITH CYCLONIC FLOW RESULTING IN SOME LINGERING SHOWERS IN THE EVE AND PRBLY VFR CIGS MUCH OF THE NIGHT. .UPDATE... WILL UPDATE ZFP/GRIDS SHORTLY TO REMOVE EARLY MORNING WORDING AS SHOWERS HAVE ALREADY MOVED OUT OF THE CWA. && .PREV DISCUSSION... /ISSUED 444 AM EDT SUN APR 1 2007/ SHORT TERM... CDFNT/DRY SLOT PRECEEDED BY LARGE AREA OF SHOWERS WAS MOVG E/35KT ACROSS INDIANA THIS MORNING AND APPEARS IT WILL MOVE EAST OF OUR CWA BY 12Z. CARRIED SHOWERS ENDING PREDAWN ACROSS ERN ZONES TO ACCOUNT FOR THIS. CLEAR AREA OVER IL WILL OVERSPREAD THE CWA THIS MORNING. SFC DEWPOINTS IN IL BEHIND THE CDFNT ARE GENERALLY IN THE 40S. STRONG DAYTIME HEATING TODAY WILL RESULT IN WK INSTABILITY DVLPG BUT CAPE WILL EXTEND FROM THE FREEZING LEVEL UP THROUGH -20C. WITH HIGH CLOUD BASES AND RELATIVELY DRY SUB-CLOUD LAYER... GOOD POTENTIAL FOR DOWNWARD MIXING OF AIR IN ANY SHOWERS/TSTMS THAT DVLP THIS AFTN AND ALSO WILL BE CONDUCIVE FOR AT LEAST SOME SMALL HAIL. OTHER CONCERN TODAY IS GENERAL STRONG WIND GUSTS THIS AFTN AS NAM12/GFS FCST SOUNDINGS ON BUFKIT CONTINUING TO SUGGEST WINDS AROUND 35KTS WILL MIX DOWN TO THE SFC. SOME WRAP AROUND LOW CLOUDS AND LIGHT SHOWERS POSSIBLE THIS EVENING ACROSS N-NE PORTION OF CWA. WINDS SHOULD STAY UP OVERNIGHT LIMITING DIURNAL COOLING AND RAISED OUR GOING MINS SLIGHTLY WITH THE EXCEPTION OF SW MI WHICH WILL HAVE WINDS TURNING IN OFF THE LAKE. LONG TERM... MONDAY THROUGH SATURDAY...MAIN CONCERNS THIS PERIOD ARE THE CHANCES FOR SEVERE WEATHER TUESDAY AFTERNOON/EARLY TUESDAY NIGHT AND THE AMOUNT OF COLD AIR SPREADING INTO THE REGION DURING THE SECOND HALF OF THE WEEK. SEVERAL FACTORS COMING TOGETHER FOR A ROUND OF SEVERE WEATHER LATE IN THE DAY TUESDAY AND TUESDAY NIGHT. MOISTURE WILL SURGE BACK INTO THE AREA TUESDAY AHEAD A STRONG AND FAST MOVING COLD FRONT. THE 00Z GFS ENSEMBLES HAVE COME INTO EVEN BETTER AGREEMENT WITH THE TRACK OF THE LOW AND THE TIMING OF THE ASSOCIATED FRONT. THE FRONT SHOULD MOVE INTO THE AREA LATE IN THE AFTERNOON OR EARLY EVENING...DURING THE MOST FAVORABLE DIURNAL TIME FOR CONVECTION. FORECAST CAPE VALUES STILL SHOWING QUITE A SPREAD...BUT GENERALLY IN THE 1500 TO 2500 J/KG RANGE. AN UPPER LEVEL JET OF OVER 120 KNOTS SHOULD ALSO HELP SUPPORT SEVERE STORMS. THEREFORE...HAVE RAISED STORM CHANCES EARLY TUESDAY NIGHT OVER MOST AREAS. LARGE HAIL...DAMAGING WINDS AND EVEN TORNADOES POSSIBLE. FOR THE REST OF THE WEEK...A STRONG COLD FRONT WILL MOVE ACROSS THE AREA TUESDAY NIGHT. THE GFS AND THE ECMWF PATTERN INDICATE AN EXTENDED COLD PERIOD WITH TEMPERATURES REMAINING WELL BELOW NORMAL AS A TROF DEEPENS OVER THE MIDWEST. RECORD LOW TEMPERATURES AT SBN ARE BASICALLY IN THE 15F TO 20F RANGE. THE 01/00Z MEX HAS A LOW OF 16F AT SBN SATURDAY MORNING. PROBABLY WILL NEED SNOW COVER TO GET THAT COLD. LOWS OF 22F TO 26F SEEM FAVORABLE. FURTHERMORE...THE GFS MAY NOT BE MODERATING THE COLD AIR ENOUGH. THE 00Z ECMWF IS ABOUT 3C TO 4C WARMER THAN THE 12Z RUN...SO TAKING ALL OF THIS INTO ACCOUNT ..HAVE TRENDED MOST TEMPERATURES DURING THE 2ND HALF OF THE WEEK DOWN. CONCERN FOR VEGETATION GROWTH AND DEVELOPMENT AHEAD OF THE NORMAL GROWTH FOR THIS TIME OF YEAR AS TEMPERATURES WILL DROP WELL BELOW FREEZING FOR SEVERAL NIGHTS THIS COMING WEEK. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...NONE. MI...NONE. OH...NONE. LM...SMALL CRAFT ADVISORY UNTIL 8 AM EDT MONDAY FOR LMZ043-046. && $$ SHORT TERM...TAYLOR LONG TERM....SKIPPER AVIATION...TAYLOR
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
1015 PM EDT MON APR 2 2007 ...MAJOR LATE SEASON WINTER STORM TOMORROW INTO WEDNESDAY... ...TRAVEL NOT RECOMMENDED TUESDAY NIGHT INTO WEDNESDAY... .UPDATE... WATER VAPOR IMAGERY AND RUC ANALYSIS SHOW WEAK SHORTWAVE RIDGING APPROACHING UPPER MI AHEAD OF SHORTWAVE MOVING THRU MT/WY. STRONG TEMP GRADIENT IS IN PLACE OVER THE PLAINS FOR THIS SHORTWAVE TO TAKE ADVANTAGE OF. LATE AFTN TEMPS REACHED THE LOWER 80S IN SE NEBRASKA WHILE IN ND TEMPS WERE IN THE 20S. PER 00Z RAOBS...850MB TEMPS RANGE FROM 22C AT KDDC TO -8C AT KINL. SRLY WINDS ARE ALREADY RAMPING UP ACROSS THE PLAINS IN RESPONSE TO APPROACHING SHORTWAVE WITH 35-40KT AT 850MB AT KDDC/KTOP. STRENGTHENING WAA IS ALREADY YIELDING RADAR ECHOES ACROSS CNTRL MN INTO SRN WI. SFC OBS INDICATE THE SRN AND ERN PORTIONS OF THE RADAR RETURNS ARE NOT PRODUCING PCPN THAT IS REACHING THE SFC. CLOSEST RAIN IS OCCURRING FROM KMSP TO KEAU. IT IS THIS PCPN THAT WILL BE OF INTEREST FOR THE OVERNIGHT AS IT COULD REACH THE FCST AREA LATE. 00Z KGRB SOUNDING SHOWED A FAIRLY SUBSTANTIAL DRY LAYER FROM 850-650MB WITH DWPT DEPRESSIONS OF 10-20C. SIMILAR LOOK IS FOUND ON EVENING TAMDAR SOUNDINGS FROM KSAW...BUT PRESENCE OF LINGERING STRATOCU DECK ELIMINATES THE DRY AIR AROUND 850MB. ALTHOUGH LOWER TROP WINDS WILL VEER AROUND TO THE NE OVERNIGHT TO HELP HOLD IN DRIER AIR...THE FLOW IS MUCH LIGHTER THAN THE STRONG SRLY FLOW DEVELOPING TO THE W AND SW. THUS...DON`T ANTICIPATE THE DRY LAYER TO HOLD BACK ADVANCING PCPN FOR LONG. SO THE QUESTION IS HOW FAST WILL FORCING SPREAD NE OVERNIGHT. BASED ON 00Z RUC...ISENTROPIC ASCENT BEGINS TO AFFECT THE AREAS NEAR THE WI BORDER AFTER 09Z. THIS LINES UP WELL WITH GOING FCST OF CHC POPS ALONG THE BORDER BEGINNING BTWN 09Z-12Z. AS FOR PTYPE...RUC40 FCST SOUNDING FOR KIMT SHOWS ABOVE 0C TEMPS (PEAKING AT 2C) FROM 800MB TO SFC. HOWEVER...WETBULB PROFILE IS AT OR JUST BLO 0C THRU THAT LAYER. BASED ON THIS AND WARM LOOK OF 00Z KGRB SOUNDING...WILL EXPAND MENTION OF RAIN/SNOW PTYPE FARTHER NW TOWARD KIMT/CRYSTAL FALLS. 00Z NAM IS JUST BEGINNING TO ARRIVE...SO THERE WILL NOT BE ANY HEADLINE ADJUSTMENTS THIS EVENING. 18Z NAM/GFS SUPPORTED GOING FCST FOR THIS MAJOR LATE SEASON WINTER STORM. GFS STILL INDICATED THAT THERE WOULD BE RAIN/SNOW PTYPE ISSUES FOR THE SE FCST AREA FOR EARLY PART OF EVENT...SO WINTER STORM WATCH IS STILL IN GOOD SHAPE THERE. HOPEFULLY...00Z RUNS WILL PIN DOWN PTYPE ISSUES AND CHANGEOVER TIMES FOR THAT AREA. THIS DEFINITELY HAS THE POTENTIAL TO BE ONE OF THE BIGGER APRIL SNOW STORMS FOR UPPER MICHIGAN. IN FACT...CURRENTLY EXPECTED SNOW TOTALS COULD MAKE THIS STORM A TOP 5 EVENT FOR APRIL FOR THIS OFFICE LOCATION. SEE TOP NEWS OF THE DAY SECTION OF WEB PAGE (WWW.WEATHER.GOV/MQT) FOR APRIL`S TOP 10 TWO DAY SNOW ACCUMULATIONS. GALE WARNINGS HAVE BEEN HOISTED FOR THE OPEN WATERS OF LAKE SUPERIOR WITH HIGH CONFIDENCE OF REACHING CRITERIA. GALES SHOULD BEGIN TUE EVENING. NOT OUT OF THE QUESTION THAT STORM FORCE GUSTS WILL OCCUR OVER CNTRL/ERN LAKE SUPERIOR LATE TUE NIGHT/WED MORNING AS LOW PRES WINDS UP. && .PREV DISCUSSION (ISSUED AT 403 PM EDT)... SYNOPSIS...WV AND RUC ANALYSIS INDICATE A CLOSED LOW OVER THE ONTARIO-QUEBEC LINE...WITH WEAK TROUGHINESS OVER THE APPALACIANS AND A DIGGING TROUGH OVER THE INTERMOUNTAIN WEST. ACROSS THE SOUTHERN CONUS...MOSTLY ZONAL FLOW IS EVIDENT WITH A FEW EMBEDDED SHORTWAVES ALONG THE GULF COAST. AT THE SURFACE...DRIER AIR WRAPPING IN BEHIND THE ONTARIO-QUEBEC SURFACE LOW HAS BROUGHT SOME CLEARING SKIES TO THE SOUTHERN REACHES OF THE CWFA...AND A WEAK AREA OF HIGH PRES OVER SOUTH CENTRAL CANADA IS PUSHING INTO NORTHEASTERN MN. THE NEXT LOW OF INTEREST IS CURRENTLY DEVELOPING ON THE LEE OF THE ROCKIES UNDER AN UPPER LEVEL SHORTWAVE...AND WILL BE WRAPPING NE OVER THE NEXT SEVERAL DAYS. SHORT TERM (TONIGHT)... ALTHOUGH CLOUDS HAVE LINGERED ACROSS MUCH OF THE CWFA TODAY AND THIS AFTERNOON...SOME CLEARING IS NOTED IN NORTHERN WI AND IN THE SOUTHERN PORTIONS OF UPPER MI ASSOCIATED WITH A WEAK AREA OF HIGH PRESSURE AHEAD OF THE PLAINS LOW. AS THIS PLAINS LOW MOVES NE...EXPECT SOME HIGH CLOUDS...AS NOTED IN H5-H3 RH IN THE NAM AND GFS...TO SPREAD ACROSS UPPER MI TONIGHT. THE 12Z NAM AND GFS BOTH KEEP THE BEST DYNAMICS AND PCPN SOUTH OF THE WI BORDER AT 12Z WEDNESDAY...BUT KEPT CHANCE POPS UP ALONG OUR BORDER. WENT WITH ALL SN AS NAM KIMT SOUNDING IS JUST LEFT OR ALONG THE ZERO ISOTHERM. FARTHER SOUTH...BROUGHT IN THE RA/SN MIX WITH A WARMER PROFILE NEAR THE LAKE. SHOULD THE PROFILE WARM JUST SLIGHTLY...WOULD NEED TO INCLUDE A LARGER AREA OF MIXED PCPN. LONG TERM (TUESDAY THROUGH NEXT MONDAY)... MAIN FORECAST CONCERN CONTINUES TO BE HOW MUCH SNOW FALLS FROM THE EXPECTED STORM SYSTEM TUE THROUGH WED. TUE...STRONG SHRTWV TROUGH CURRENTLY OVER SOUTHERN IDAHO SHOULD BE LOCATED OVER SE SOUTH DAKOTA AT 12Z...WITH AN ASSOCIATED 1005MB SURFACE LOW IN SE IOWA. MODELS SHOW AN 80-110 KT UPPER LEVEL JET ORIENTED NW TO SE MOVING INTO NEBRASKA BEHIND THIS SHRTWV TROUGH... THUS THE MODELS DIG THE TROUGH INTO IOWA AND ALSO DEVELOP A 500MB CLOSED LOW IN CENTRAL/SOUTHERN MN. THE LOW ITSELF ALSO ENDS UP DEEPENING AND LIFTING NE...REACHING THE BENTON HARBOR AREA BY 00Z WED WITH A PRESSURE OF A 1000MB. IT SHOULD BE NOTED THAT THE 13 KM RUC AND REGIONAL CANADIAN ARE OUTLIERS FROM THIS IDEA AND BRING THE SURFACE LOW UP TO THE GREEN BAY AREA. IF THESE SOLUTIONS PAN OUT...MUCH MORE PCPN WILL OCCUR. HEIGHT FALLS ASSOCIATED WITH THE SHRTWV TROUGH APPROACHING UPPER MICHIGAN...COMBINED WITH MID-LEVEL FRONTOGENESIS WHICH SPREADS NORTH OUT OF WISCONSIN...SHOULD ALLOW FOR PCPN TO DEVELOP AND INTENSIFY THROUGH THE DAY FROM SW TO NE. THE ONLY THING THAT WILL SLOW THE PCPN FROM MOVING NORTH IS DRY AIR THAT IS PRESENT OVER UPPER MICHIGAN TONIGHT AND CONTINUES TO GET FED INTO THE AREA ON NE WINDS ALOFT ON TUE. HOWEVER...ONCE THE PROFILE SATURATES...THE PCPN WILL START AND CONTINUE THROUGH THE REST OF THE DAY. AS FAR AS PCPN TYPE GOES...THE LATEST MODELS AND THE PREVIOUS 00Z CYCLE TOOK THE LOW TRACK A BIT FARTHER SOUTH...WHICH ALLOWS COOLER AIR TO ENTER THE CWA QUICKER THAN SHOWN YESTERDAY. THEREFORE... NOW MODEL SOUNDINGS ONLY INDICATE THAT AREAS ALONG LAKE MICHIGAN MAY SEE SOME RAIN MIX IN. REGARDING ACTUAL QPF AND SNOW AMOUNTS...THE INCREASING VERTICAL MOTION FROM DPVA AND FRONTOGENESIS SHOULD RESULT IN DECENT PRODUCTION OF PCPN. 12 HOUR QPF AMOUNTS FROM THE NAM...WHICH SEEMS REASONABLE...SUGGESTS UP TO A 0.50 INCH ALONG THE WISCONSIN BORDER BETWEEN IWD AND IMT TO VERY LITTLE IN THE EASTERN U.P.. SNOW TO WATER RATIOS SHOULD START OFF FAIRLY HIGH (12 TO 15 TO 1) GIVEN DEEP MOISTURE AND PLENTY OF LIFT IN THE SNOW GROWTH LAYER. HOWEVER...THERE ARE INDICATIONS OF A DRY SLOT MOVING NORTHWARD INTO THE SOUTH CENTRAL U.P. IN THE AFTERNOON...DRYING OUT THE SNOW GROWTH LAYER...THUS KNOCKING RATIOS DOWN TO 8 TO 1. IN ANY EVENT...4 TO 7 INCHES IS NOT OUT OF THE QUESTION...ESPECIALLY NEAR IWD CLOSER TO THE BETTER MOISTURE. TUE NIGHT...UPPER LOW/STRONG SHRTWV TROUGH IS PROGGED TO DIG AND TURN NEGATIVELY TILTED TUE NIGHT THROUGH LOWER MICHIGAN...CAUSING THE SURFACE LOW TO DEEPEN RAPIDLY AND LIFT NNE...REACHING NORTHERN LAKE HURON BY 12Z WED WITH A 991MB PRESSURE. THIS IS A VERY FAVORABLE TRACK FOR HEAVY SNOW ACROSS THE AREA...AND IS THIS NOTED IN THE QPF FIELDS FROM ALL THE MODELS. SOME OF THE FACTORS HELPING TO PRODUCE THE HEAVY SNOW INCLUDE: 1. VERY STRONG Q-VECTOR CONVERGENCE ASSOCIATED WITH HEIGHT FALLS FROM THE DEEPENING 500MB LOW. 2. STRONG MID LEVEL FRONTOGENESIS. 3. INCREASING NORTHERLY WINDS...RESULTING IN UPSLOPE OVER THE NORTHERN U.P.. 4. 850MB TEMPS COOLING TO -6C EAST TO -14C WEST...RESULTING IN LAKE ENHANCEMENT. DURING THE TIME OF THE SYNOPTIC SUPPORT...SINCE IT WILL BE MOVING VERY SLOWLY EASTWARD...THE BEST OMEGA INTERSECTS THE SNOW GROWTH. IN ADDITION...THE 850MB TEMPS WILL FALL DOWN TO THE DENDRITIC CRYSTAL SNOW GROWTH LATE. REGARDING AMOUNTS...HAVE FOLLOWED THE NAM SINCE ITS FIELD LOOKS SIMILAR TO THE PREFERRED GFS...BUT SHOWS EXTRA ENHANCEMENT FOR UPSLOPE AREAS. SNOW TO WATER RATIOS SHOULD BE IN THE 10 TO 15 TO 1 RANGE...WHICH RESULTS IN AMOUNTS OF 4 TO 10 INCHES...MOST IN THE UPSLOPE AREAS OF THE NORTH CENTRAL U.P.. IF THE REGIONAL CANADIAN IS RIGHT...BETWEEN 06-12Z...THE OFFICE COULD SEE AN INCH OF QPF WHICH WOULD TRANSLATE TO 10 TO 15 INCHES OF SNOW. LASTLY...THE WINDS ARE PROGGED TO REALLY INCREASE TOWARDS 12Z...WITH THE NAM SHOWING 50 KT AT 3000 FT. THEREFORE A LOT OF BLOWING MAY OCCUR TOWARDS DAYBREAK AND HAVE CHANGED THE AREAS OF BLOWING SNOW TO WIDESPREAD. ALSO HAVE RAISED WINDS ON LAKE SUPERIOR TO 45 KT TO ACCOUNT FOR THESE STRONGER WINDS. WED THROUGH THU...UPPER AND SURFACE LOWS ARE PROGGED TO BECOME NEARLY VERTICAL STACKED WHEN THEY REACH GEORGIAN BAY AROUND 00Z THU...THEN MOVE TO QUEBEC AND NEW ENGLAND BY 00Z THU. SYNOPTIC SNOW SHOULD DIMINISH ON WEDNESDAY WEST TO EAST...THOUGH COLD 850MB TEMPS (-14 TO -16C) FLOWING ACROSS LAKE SUPERIOR AND PLENTY OF MOISTURE WILL SUPPORT NUMEROUS LAKE EFFECT SNOW SHOWERS THROUGH THU. IN ADDITION...GIVEN THE STRONG WINDS ON WEDNESDAY...BLOWING SNOW WILL CONTINUE TO BE A PROBLEM (ESPECIALLY SINCE IT IS LAKE EFFECT WHICH HAS A DRIER WATER TO SNOW RATIO). TEMPERATURES WILL BE BELOW NORMAL THROUGH THE PERIOD AND GENERALLY FOLLOWED A BLEND OF MOS GUIDANCE FOR HIGHS AND LOWS. HAZARD ADJUSTMENTS: SINCE SOME FRONTOGENESIS SNOW WILL BE MOVING NORTH ON TUESDAY...HIGH CONFIDENCE OF UPPER MICHIGAN GETTING INTO THE COMMA HEAD AND PLENTY OF WIND/BLOWING SNOW AFTER MIDNIGHT TUESDAY NIGHT INTO WEDNESDAY...HAVE UPGRADED THE PREVIOUS WATCHES TO WARNINGS. ALSO ADDED LUCE AND NORTHERN SCHOOLCRAFT TO THE WARNINGS. FOR THE COUNTIES ALONG LAKE MICHIGAN...HAVE INSERTED THEM INTO A WATCH SINCE SOME UNCERTAINTY STILL REMAINS ON THE LOW TRACK. HOWEVER...IT IS LIKELY THEY WILL NEED AT LEAST A SNOW AND BLOWING SNOW ADVISORY. THU NIGHT THROUGH MON...MODELS REMAIN IN VERY GOOD AGREEMENT DURING THIS TIME PERIOD...BASICALLY KEEPING THE EAST HALF OF NORTH AMERICA UNDER A TROUGH WITH UNSEASONABLY COOL AIR. OVER TIME...THOUGH...THIS TROUGH WILL WARM UP...AS INDICATED BY 850MB TEMPS FROM THE ECMWF RISING FROM -14 TO -16C THU NIGHT THROUGH SAT UP TO -10 TO -12C BY MONDAY. WITHIN THE LARGER TROUGH...THE MAIN FEATURE OF INTEREST IS A WEST TO EAST SHRTWV TROUGH WHICH DROPS SOUTH ACROSS LAKE SUPERIOR THU NIGHT INTO FRI MORNING. THIS FEATURE SHOULD PROVIDE SOME ENHANCEMENT TO THE LAKE EFFECT SNOW DURING THE NIGHT...ALONG WITH INCREASING THE WINDS. FROM FRIDAY NIGHT INTO MONDAY...WINDS ARE SHOWN TO GRADUALLY RELAX...THOUGH SNOW CHANCES CONTINUE GIVEN THE COLD AIR ALOFT (COULD BE A COMBINATION OF LAKE EFFECT AND/OR DIURNAL ACTIVITY). HOWEVER...IT APPEARS THAT ON MONDAY ENOUGH DRY AIR SHOULD ENTER THE CWA...AND COMBINE WITH ANTICYCLONIC FLOW FROM THE PERSISTENT HIGH OVER CENTRAL CANADA MOVING OVER UPPER MICHIGAN TO RESULT IN A DRY FORECAST. BEYOND MONDAY...MODELS SHOW A FASTER PACIFIC JET DEVELOPING WHICH HELPS TO EITHER PUSH THE WESTERN RIDGE EASTWARD (ECMWF) OR FLATTEN IT OUT AND RESULT IN A ZONAL PATTERN (GFS). IN EITHER EVENT...THIS SHOULD ALLOW CONDITIONS TO GET BACK TO NORMAL. && .MQT WATCHES/WARNINGS/ADVISORIES... WINTER STORM WARNING 8 AM EDT /7 PM CDT/ TUE TO 8 PM EDT /7 PM CDT/ WED MIZ002-009. WINTER STORM WARNING 7 AM TUE TO 1 PM CDT WED FOR MIZ010-011. WINTER STORM WARNING 2 PM TUE TO 8 PM EDT WED MIZ001-003>006-084. WINTER STORM WARNING 6 PM TUE TO 8 PM EDT WED MIZ007-085. WINTER STORM WATCH TUE AFTN THRU WED AFTN MIZ012-013. WINTER STORM WATCH TUE EVENING THRU WED EVENING MIZ014. GALE WARNING LAKE SUPERIOR. && $$ ROLFSON (UPDATE) JLL (SHORT TERM) AJ (LONG TERM)
AREA FORECAST DISCUSSION
NWS GAYLORD MI
146 PM EDT SUN APR 1 2007 .AVIATION...AXIS OF OCCLUDED FRONT AT 1700Z RUNS FROM NEAR PLN TO NORTH OF OSC. LAST OF IFR CONDITIONS AT APN SHOULD FINALLY ERODE AWAY IN THE NEXT HOUR OR SO BASED ON SATELLITE TRENDS. MID CLOUDS STARTING TO INCREASE INTO TVC...SCATTERED RAIN SHOWERS DEVELOPING ACROSS CENTRAL LAKE MICHIGAN WITH A MORE PERSISTENT RAIN BAND OVER SOUTHEAST WI. EXPECT THIS RAIN BAND TO SWEEP EAST ACROSS NORTHERN MI DURING THE LATE AFTERNOON AND EVENING HOURS...THEN PRECIPITATION SHOULD BECOME MORE SPOTTY/DRIZZLY OVERNIGHT WITH GENERALLY MVFR CEILINGS. WINDS SHOULD BE GUSTY FOR A TIME INTO EARLY EVENING ESPECIALLY AROUND TVC WITH COLD ADVECTION DEVELOPING AND MIXING 30-40KT WINDS DOWNWARD. JPB && .UPDATE... /ISSUED 1056 AM EDT SUN APR 1 2007/ 12Z SURFACE ANALYSIS SHOWS 992MB OCCLUDED LOW OVER SOUTHERN MN..OCCLUDED FRONT STRETCHES EAST ACROSS WI/SOUTHERN LOWER TO TRIPLE POINT NEAR TOL. SECONDARY COLD FRONT ACROSS SOUTHEAST MN/EASTERN IA/MO. BULK OF THE INITIAL PRECIPITATION HAS LIFTED NORTHEAST OF THE AREA THOUGH A FEW SHOWERS CONTINUE TO DEVELOP ALONG THE BACK EDGE AT THE LEADING EDGE OF THE DRY SLOT. SOME FOG/ST/DRIZZLE HAS DEVELOPED ACROSS INTERIOR NORTHERN LOWER... WITH CLEARING SKIES ACROSS SOUTHWEST QUADRANT OF THE FORECAST AREA. OCCLUDED FRONT WILL LIFT SLOWLY NORTHEAST ACROSS NORTHERN LOWER TODAY...PRETTY WELL DEFINED BY DIFFERENTIAL HEATING OCCURRING ACROSS IT BETWEEN WHERE SKIES ARE CLEAR (MID 50S AT FKS/MBL) AND OVERCAST (MID 30S EASTERN UPPER/FAR NORTHEAST LOWER). EXPECT BOUNDARY TO GET HUNG UP NEAR THE STRAITS...WHICH GIVEN WARM OCCLUSION NATURE OF THE BOUNDARY WILL PROBABLY KEEP LOW CLOUDS LOCKED IN FOR A WHILE INTO THE AFTERNOON ACROSS PARTS OF EASTERN UPPER AND FAR NORTHERN LOWER. LOW LEVEL MOISTURE IS GETTING SCOURED OUT HOWEVER (AIRCRAFT SOUNDING OUT OF TVC HAS DRIED OUT SUBSTANTIALLY SINCE EARLIER THIS MORNING)...SO EVEN AREAS THAT REMAIN NORTH OF THE OCCLUSION SHOULD BREAK OUT INTO SOME SUN LATER THIS AFTERNOON. DESPITE THE ANTICIPATED CLEARING...THE LOW LEVEL DRYING WILL LIKELY INHIBIT INSTABILITY POTENTIAL. SO LOOKING MORE LIKELY THAT MUCH OF EASTERN UPPER/NORTHEAST LOWER WILL STAY DRY INTO LATE AFTERNOON...WITH DEEPER WRAP AROUND MOISTURE/COLD AIR ALOFT SLIDING BACK INTO NORTHWEST LOWER BY MID AFTERNOON...THUS INCREASING THE THREAT FOR SHOWERS AND PERHAPS A RUMBLE OF THUNDER WEST OF I-75. RAIN CHANCES WILL INCREASE ACROSS FAR EASTERN UPPER/NORTHEAST LOWER AFTER 21Z. JPB && .PREV DISCUSSION... /ISSUED 733 AM EDT SUN APR 1 2007/ SFC/RUC/SATELLITE/RADAR AND UPPER AIR ANALYSIS SHOWING NEGATIVELY TILTED UPPER LOW IN SRN BRANCH OF UPPER LEVEL SPLIT FLOW WORKING INTO SRN MN...ALONG WITH DEEP/OCCLUDING SFC LOW PRESSURE. DEEP MOISTURE PLUME EVIDENT IN STRONG AND DEEP SOUTHERLY FLOW ACROSS INDIANA AND MICHIGAN...USHERED IN BY 40-50KT LLJ. MUCH OF THIS MOISTURE IS BEING DIRECTED AROUND THE NE PERIPHERY OF THE UPPER/ SFC LOWS...CONSIDERING HOW CLOSED OFF THEY ARE. AS A RESULT OF THIS DEEP SYSTEM...WIDESPREAD RAIN AND SOME THUNDERSTORMS ARE AFFECTING AREAS FROM WESTERN TN...THROUGH IL/INDY...MICHIGAN BACK ACROSS WISCONSIN/MN/IOWA AND THE DAKOTAS/EAST NEBRASKA. QUITE THE SYSTEM. THE THUNDERSTORMS WERE MAINLY OCCURRING ALONG THE LEADING EDGE OF THE MID LEVEL DRY SLOT...BUT HAVE WANED IN THE LAST FEW HOURS AS OCCLUDING PROCESS HAS SEEMINGLY SHIFTED BETTER LLJ INTO AREAS EAST OF DTX WHERE NEW THUNDERSTORMS HAVE DEVELOPED. FORECAST CONCERNS...MANY...TOO MANY. SHOWERS AND THUNDER CHANCES THIS MORNING...TIMING THE CLEARING BEHIND IT...THEN BRINGING SHOWERS AND POSSIBLE THUNDERSTORMS BACK INTO THE FORECAST FOR THE AFTERNOON. ALSO...WINDS ARE A CONCERN FOR NEARSHORE ZONES. PRECIP THEN REMAINS THE MAIN CONCERN INTO TONIGHT AND TOMORROW MORNING BEFORE...ADDITIONAL PRECIP ISSUES DEVELOP LATE MONDAY NIGHT INTO TUESDAY WHILE NEXT STORM SYSTEM BECOMES RATHER VIGOROUS TOO. PRECIP TYPE ISSUES ARISE BY TUESDAY NIGHT..WHICH THEN TRANSFORM INTO LAKE EFFECT ISSUES. TODAY...SFC LOW CONTINUES TO OCCLUDE AND NEW SFC LOW DEVELOPMENT TAKING SHAPE OVER NRN INDIANA...HELPING TO REFOCUS THE LLJ INTO WESTERN OHIO. THIS IS ALLOWING FOR ELEVATED THUNDERSTORMS TO DECREASE IN COVERAGE ACROSS NRN MICHIGAN (NEWER DEVELOPMENT NOW OVER LAKE ONTARIO). WITH ISOLATED ACTIVITY STILL PRESENT ALONG THE LEADING EDGE OF THE MID LEVEL DRY SLOT...AND ARRIVAL OF STEEPER 6-6.5C/KM LAPSE RATES INTO MUCH OF NRN LOWER MICHIGAN...WILL HAVE TO CARRY A MENTION OF ISOLATED THUNDER EARLY THIS MORNING. THIS DRY SLOT PUNCHES NORTHWARD AND THROUGH ALL OF NRN MICHIGAN BY 18Z. DISTINCT CLEARING LINE SEEN BEHIND THIS FEATURE...SO AFTER SOMEWHAT OF A WET DAYBREAK...LOOK FOR THE SUN TO APPEAR FOR AT LEAST A PERIOD OF TIME FOR NORTHERN LOWER MICHIGAN BETWEEN MID- LATE MORNING AND EARLY AFTERNOON. THIS WILL LESS LIKELY BE THE CASE FOR EASTERN UPPER....WHERE COOL SE WINDS COMING IN OFF LAKE HURON MAY PUT A DIRECT HALT OF THE NORTHWARD MOVEMENT OF THE OCCLUDED/WARM FRONT. A TYPICAL OCCURRENCE THIS TIME OF YEAR. THIS WILL LEAD TO THE POSSIBILITY OF SCATTERED SHOWERS CONTINUING ACROSS EASTERN UPPER THROUGH THE ENTIRE DAY AND COLDER HIGH TEMPERATURES WHICH WILL STRUGGLE TO GET OUT OF THE MIDDLE 40S. FOR NRN LOWER...SECONDARY SHORTWAVE ENERGY AND ROUND OF STRONGER LOW TO MID LEVEL WINDS (850MB 40KTS..700MB 70KTS) PUNCHING UP ACROSS THE SAGINAW BAY AREA. PASSAGE OF THE FRONT AND RESULTING CLEARING LOOKS TO LEAD TO TEMPERATURES TAPPING INTO THE LOWER 60S. MODIFYING AFTERNOON SOUNDINGS REVEAL A FEW HUNDRED J/KG OF SBCAPE. COUPLE THAT WITH MODEST H8-H5 -DIVQ AND STEEPER MID LEVEL LAPSE RATES ARRIVING IN ALL OF NRN MICHIGAN (6.5 TO 7.0C/KM...STEEPEST ACROSS THE SE CWA) AND ISOLATED THUNDERSTORMS ARE ALSO POSSIBLE THIS AFTERNOON. SLIGHT RISK OF SEVERE STORMS REMAINS TO OUR SE...ACROSS SE LOWER MICHIGAN. TONIGHT...THIS SECONDARY SHORTWAVE ENERGY AND ASSOCIATED FORCING AND STRONGER WIND FIELDS STICK AROUND FOR THE EVENING...BEFORE SHIFTING EAST OF US BY MIDNIGHT. THERE WILL BE RESIDUAL/MORE SHEARED OUT ENERGY THAT WILL PASS BY OVERNIGHT...BUT FORCING IS MINIMAL. LARGE STRATO CU DECK ACROSS IOWA ATTM...WILL BE HEADING OUR WAY AND OVERSPREADING THE ENTIRE FORECAST AREA. WILL GO WITH SHOWERS LIKELY THIS EVENING AND NOT MENTION THUNDER ATTM. WILL LET DAY CREW ASSESS EXTENT OF ANY AFTERNOON DEVELOPMENT FOR CONTINUATION IN THE EVENING FORECAST. SCATTERED LIGHT RAIN SHOWERS WILL BE THE CALL FOR THE OVERNIGHT PERIOD...BUT LOOKING UPSTREAM...WILL NOT BE OUT OF THE QUESTION ENTIRELY TO SEE A SPIT OR TWO OF DRIZZLE AS THE PRECIP TYPE. COOLER AIR WILL MOVE IN...BUT PRESENCE OF LOWER LEVEL CLOUDS WILL KEEP LOWS IN THE UPPER 30S IN EASTERN UPPER...AND IN THE LOWER 40S FOR NRN LOWER. MONDAY...THE RESIDUAL SHEARED OUT SHORTWAVE ENERGY AND MOISTURE WILL BE THE EVIDENCE FOR JUST A SMALL CHANCE (30%) OF SHOWERS IN THE MORNING. UPPER TROUGH WILL BE NE OF THE AREA AND FORCING BECOMES INCREASINGLY DOWNWARD INTO THE AFTERNOON. SKIES SHOULD BE MOSTLY CLOUDY THROUGH THE DAY THOUGH. POSSIBLE CLEARING LATE SOUTH OF M-72. TEMPERATURES WILL RANGE FROM THE MIDDLE 40S EASTERN UPPER TO THE LOWER HALF OF THE 50S SOUTH OF M-72. MONDAY NIGHT...NEXT UPPER TROUGH WILL BE EJECTING OUT OF THE NRN ROCKIES WHILE WE GET SOME MID LEVEL RIDGING AND PRECIPITATION FREE WEATHER. POSSIBLY A PEEK AT THE SUN/STARS HEADING THROUGH THE EVENING. THIS IS ALL BEFORE SKIES INCREASE IN CLOUDS AGAIN...AS SIGNALS START TO APPEAR OF INCREASED THETA-E AIR ARRIVE OVERNIGHT AHEAD OF INITIAL ENERGY EJECTING FROM THIS TROUGH AND NEARING WARM FRONT THAT EDGES INTO NRN IL/SRN LK MI. WILL GO MOSTLY CLOUDY ALL AREAS BY LATE OVERNIGHT. AT THE SAME TIME...MODELS ARE STILL POINTING TOWARD A SMALL CHANCE OF PRECIPITATION FOR FAR NW LOWER MICHIGAN AROUND DAYBREAK. MANY QUESTIONS REVOLVE AROUND THE EVOLUTION OF THIS SYSTEM. GFS IS QUITE COOLER THAN NAM AND OTHER MODELS...BUT HAS BEEN THE MODEL OF CHOICE BY SOME. AM NOT SO SURE ABOUT THIS...AS GFS SHOWS A SFC LOW IN NRN IL WITH UPPER TROUGH TOO FAR NW FOR THIS TO MAKE TOTAL SENSE. AS A RESULT...GFS KEEPS MUCH COLDER AIR OVER NRN MICHIGAN COMPARED TO NAM AND OTHER MODELS. REASON FOR ALL OF THIS TALK...WELL IS PRECIP BREAKS OUT THEN IT COULD BE IN THE FORM OF A MIX FOR FAR NRN LOWER. AM GOING TO LEAN MORE SO ON THE SIDE OF WARMER WITH THIS ONE...SO WILL KEEP JUST A CHANCE OF RAIN IN THE FORECAST. TUESDAY...FOLLOWING THIS SAME TRAIN OF THOUGHT...AND FOLLOWING THE POSITION OF THE UPPER TROUGH...STRONGER DYNAMICAL FORCING ARRIVES MORE SO IN THE AFTERNOON. WOULD EXPECT RAIN SHOWERS TO BECOME LIKELY ACROSS THE ENTIRE FORECAST AREA. GFS SEEMS TO BE SUFFERING FROM FEEDBACK ISSUES AFTER LOOKING AT AN ANOMALOUS 70KT LLJ POINTING INTO THE SAG BAY AREA WITH SEEMINGLY TOO STEEP OF MID LEVEL LAPSE RATES BY TUESDAY AFTERNOON. DAY CREW CAN TAKE A CLOSER LOOK AT THIS...AS CURRENT WEATHER KEPT THE FOCUS ON THE SHORTER TERM ISSUES. HOWEVER...WOULD EXPECT A WARMER SOLUTION FOR JUST RAIN AS THE PRECIP TYPE THROUGH TUESDAY...AND LIKELY THUNDERSTORMS SEEMS A BIT OVERDONE AT THIS POINT. TUESDAY NIGHT...UPPER TROUGH STRENGTHENS AND SFC LOW DEEPENS THROUGH THE NIGHT...WHILE MOVING UP INTO OUR NECK OF THE WOODS. PRECIPITATION REMAINS LIKELY...AND COLDER AIR WILL INVADE THE AREA. ODDS HERE FOR A CHANGE IN PRECIP TYPE IS STILL VERY GOOD. WITH STRONG FORCING WHILE THIS IS OCCURRING...PORTIONS OF THE CWA IN ACCUMULATING SNOW IS A DEFINITE POSSIBILITY. WILL HAVE TO BE WATCHING THIS SYSTEM CLOSELY...AS IT SEEMS THAT MOTHER NATURE JUST WANTS TO REMIND US THAT WE ARE IN NRN MICHIGAN IN EARLY APRIL. DOESN`T NECESSARILY MEAN SPRING IS HERE IN EARNEST. LATER PERIODS (WED AND THU)...SURFACE LOW PRESSURE MOVES EAST OF THE AREA...BUT STRONG COLD ADVECTION BEHIND THIS SYSTEM DROPPING 850MB TEMPERATURES BELOW 0C BY 12Z AND -10C BY 00Z THU SPELLS SNOW SHOWERS WITH A GREATER CHANCE WITHIN THE DEFORMATION ZONE ACROSS EASTERN UPPER AND NE LOWER. LATE SEASON LAKE EFFECT THEN CRANKS UP ACROSS THE TYPICAL SNOW BELTS WEDS NIGHT INTO THU AS 850MB TEMPERATURES FALL BETWEEN -13C AND -15C AND DEEP MOISTURE WITHIN THE UPPER LEVEL LOW HANGS ON. THE DEEP MOISTURE THEN PULLS OUT ON THURSDAY AND WOULD SIGNAL A DECREASING TREND IN SNOW SHOWER ACTIVITY...BUT PLENTY OF INSTABILITY WITH DELTA T/S ON THE ORDER OF 15C WILL REMAIN PRESENT. IN GENERAL...A COLD AND SNOWY PERIOD WITH HIGH TEMPERATURES AROUND 15 DEGREES BELOW NORMAL. MPC && .APX WATCHES/WARNINGS/ADVISORIES...NONE. && $$
AREA FORECAST DISCUSSION
NWS GAYLORD MI
1056 AM EDT SUN APR 1 2007 .UPDATE...12Z SURFACE ANALYSIS SHOWS 992MB OCCLUDED LOW OVER SOUTHERN MN..OCCLUDED FRONT STRETCHES EAST ACROSS WI/SOUTHERN LOWER TO TRIPLE POINT NEAR TOL. SECONDARY COLD FRONT ACROSS SOUTHEAST MN/EASTERN IA/MO. BULK OF THE INITIAL PRECIPITATION HAS LIFTED NORTHEAST OF THE AREA THOUGH A FEW SHOWERS CONTINUE TO DEVELOP ALONG THE BACK EDGE AT THE LEADING EDGE OF THE DRY SLOT. SOME FOG/ST/DRIZZLE HAS DEVELOPED ACROSS INTERIOR NORTHERN LOWER... WITH CLEARING SKIES ACROSS SOUTHWEST QUADRANT OF THE FORECAST AREA. OCCLUDED FRONT WILL LIFT SLOWLY NORTHEAST ACROSS NORTHERN LOWER TODAY...PRETTY WELL DEFINED BY DIFFERENTIAL HEATING OCCURRING ACROSS IT BETWEEN WHERE SKIES ARE CLEAR (MID 50S AT FKS/MBL) AND OVERCAST (MID 30S EASTERN UPPER/FAR NORTHEAST LOWER). EXPECT BOUNDARY TO GET HUNG UP NEAR THE STRAITS...WHICH GIVEN WARM OCCLUSION NATURE OF THE BOUNDARY WILL PROBABLY KEEP LOW CLOUDS LOCKED IN FOR A WHILE INTO THE AFTERNOON ACROSS PARTS OF EASTERN UPPER AND FAR NORTHERN LOWER. LOW LEVEL MOISTURE IS GETTING SCOURED OUT HOWEVER (AIRCRAFT SOUNDING OUT OF TVC HAS DRIED OUT SUBSTANTIALLY SINCE EARLIER THIS MORNING)...SO EVEN AREAS THAT REMAIN NORTH OF THE OCCLUSION SHOULD BREAK OUT INTO SOME SUN LATER THIS AFTERNOON. DESPITE THE ANTICIPATED CLEARING...THE LOW LEVEL DRYING WILL LIKELY INHIBIT INSTABILITY POTENTIAL. SO LOOKING MORE LIKELY THAT MUCH OF EASTERN UPPER/NORTHEAST LOWER WILL STAY DRY INTO LATE AFTERNOON...WITH DEEPER WRAP AROUND MOISTURE/COLD AIR ALOFT SLIDING BACK INTO NORTHWEST LOWER BY MID AFTERNOON...THUS INCREASING THE THREAT FOR SHOWERS AND PERHAPS A RUMBLE OF THUNDER WEST OF I-75. RAIN CHANCES WILL INCREASE ACROSS FAR EASTERN UPPER/NORTHEAST LOWER AFTER 21Z. JPB && .PREV DISCUSSION... /ISSUED 733 AM EDT SUN APR 1 2007/ SFC/RUC/SATELLITE/RADAR AND UPPER AIR ANALYSIS SHOWING NEGATIVELY TILTED UPPER LOW IN SRN BRANCH OF UPPER LEVEL SPLIT FLOW WORKING INTO SRN MN...ALONG WITH DEEP/OCCLUDING SFC LOW PRESSURE. DEEP MOISTURE PLUME EVIDENT IN STRONG AND DEEP SOUTHERLY FLOW ACROSS INDIANA AND MICHIGAN...USHERED IN BY 40-50KT LLJ. MUCH OF THIS MOISTURE IS BEING DIRECTED AROUND THE NE PERIPHERY OF THE UPPER/ SFC LOWS...CONSIDERING HOW CLOSED OFF THEY ARE. AS A RESULT OF THIS DEEP SYSTEM...WIDESPREAD RAIN AND SOME THUNDERSTORMS ARE AFFECTING AREAS FROM WESTERN TN...THROUGH IL/INDY...MICHIGAN BACK ACROSS WISCONSIN/MN/IOWA AND THE DAKOTAS/EAST NEBRASKA. QUITE THE SYSTEM. THE THUNDERSTORMS WERE MAINLY OCCURRING ALONG THE LEADING EDGE OF THE MID LEVEL DRY SLOT...BUT HAVE WANED IN THE LAST FEW HOURS AS OCCLUDING PROCESS HAS SEEMINGLY SHIFTED BETTER LLJ INTO AREAS EAST OF DTX WHERE NEW THUNDERSTORMS HAVE DEVELOPED. FORECAST CONCERNS...MANY...TOO MANY. SHOWERS AND THUNDER CHANCES THIS MORNING...TIMING THE CLEARING BEHIND IT...THEN BRINGING SHOWERS AND POSSIBLE THUNDERSTORMS BACK INTO THE FORECAST FOR THE AFTERNOON. ALSO...WINDS ARE A CONCERN FOR NEARSHORE ZONES. PRECIP THEN REMAINS THE MAIN CONCERN INTO TONIGHT AND TOMORROW MORNING BEFORE...ADDITIONAL PRECIP ISSUES DEVELOP LATE MONDAY NIGHT INTO TUESDAY WHILE NEXT STORM SYSTEM BECOMES RATHER VIGOROUS TOO. PRECIP TYPE ISSUES ARISE BY TUESDAY NIGHT..WHICH THEN TRANSFORM INTO LAKE EFFECT ISSUES. TODAY...SFC LOW CONTINUES TO OCCLUDE AND NEW SFC LOW DEVELOPMENT TAKING SHAPE OVER NRN INDIANA...HELPING TO REFOCUS THE LLJ INTO WESTERN OHIO. THIS IS ALLOWING FOR ELEVATED THUNDERSTORMS TO DECREASE IN COVERAGE ACROSS NRN MICHIGAN (NEWER DEVELOPMENT NOW OVER LAKE ONTARIO). WITH ISOLATED ACTIVITY STILL PRESENT ALONG THE LEADING EDGE OF THE MID LEVEL DRY SLOT...AND ARRIVAL OF STEEPER 6-6.5C/KM LAPSE RATES INTO MUCH OF NRN LOWER MICHIGAN...WILL HAVE TO CARRY A MENTION OF ISOLATED THUNDER EARLY THIS MORNING. THIS DRY SLOT PUNCHES NORTHWARD AND THROUGH ALL OF NRN MICHIGAN BY 18Z. DISTINCT CLEARING LINE SEEN BEHIND THIS FEATURE...SO AFTER SOMEWHAT OF A WET DAYBREAK...LOOK FOR THE SUN TO APPEAR FOR AT LEAST A PERIOD OF TIME FOR NORTHERN LOWER MICHIGAN BETWEEN MID- LATE MORNING AND EARLY AFTERNOON. THIS WILL LESS LIKELY BE THE CASE FOR EASTERN UPPER....WHERE COOL SE WINDS COMING IN OFF LAKE HURON MAY PUT A DIRECT HALT OF THE NORTHWARD MOVEMENT OF THE OCCLUDED/WARM FRONT. A TYPICAL OCCURRENCE THIS TIME OF YEAR. THIS WILL LEAD TO THE POSSIBILITY OF SCATTERED SHOWERS CONTINUING ACROSS EASTERN UPPER THROUGH THE ENTIRE DAY AND COLDER HIGH TEMPERATURES WHICH WILL STRUGGLE TO GET OUT OF THE MIDDLE 40S. FOR NRN LOWER...SECONDARY SHORTWAVE ENERGY AND ROUND OF STRONGER LOW TO MID LEVEL WINDS (850MB 40KTS..700MB 70KTS) PUNCHING UP ACROSS THE SAGINAW BAY AREA. PASSAGE OF THE FRONT AND RESULTING CLEARING LOOKS TO LEAD TO TEMPERATURES TAPPING INTO THE LOWER 60S. MODIFYING AFTERNOON SOUNDINGS REVEAL A FEW HUNDRED J/KG OF SBCAPE. COUPLE THAT WITH MODEST H8-H5 -DIVQ AND STEEPER MID LEVEL LAPSE RATES ARRIVING IN ALL OF NRN MICHIGAN (6.5 TO 7.0C/KM...STEEPEST ACROSS THE SE CWA) AND ISOLATED THUNDERSTORMS ARE ALSO POSSIBLE THIS AFTERNOON. SLIGHT RISK OF SEVERE STORMS REMAINS TO OUR SE...ACROSS SE LOWER MICHIGAN. TONIGHT...THIS SECONDARY SHORTWAVE ENERGY AND ASSOCIATED FORCING AND STRONGER WIND FIELDS STICK AROUND FOR THE EVENING...BEFORE SHIFTING EAST OF US BY MIDNIGHT. THERE WILL BE RESIDUAL/MORE SHEARED OUT ENERGY THAT WILL PASS BY OVERNIGHT...BUT FORCING IS MINIMAL. LARGE STRATO CU DECK ACROSS IOWA ATTM...WILL BE HEADING OUR WAY AND OVERSPREADING THE ENTIRE FORECAST AREA. WILL GO WITH SHOWERS LIKELY THIS EVENING AND NOT MENTION THUNDER ATTM. WILL LET DAY CREW ASSESS EXTENT OF ANY AFTERNOON DEVELOPMENT FOR CONTINUATION IN THE EVENING FORECAST. SCATTERED LIGHT RAIN SHOWERS WILL BE THE CALL FOR THE OVERNIGHT PERIOD...BUT LOOKING UPSTREAM...WILL NOT BE OUT OF THE QUESTION ENTIRELY TO SEE A SPIT OR TWO OF DRIZZLE AS THE PRECIP TYPE. COOLER AIR WILL MOVE IN...BUT PRESENCE OF LOWER LEVEL CLOUDS WILL KEEP LOWS IN THE UPPER 30S IN EASTERN UPPER...AND IN THE LOWER 40S FOR NRN LOWER. MONDAY...THE RESIDUAL SHEARED OUT SHORTWAVE ENERGY AND MOISTURE WILL BE THE EVIDENCE FOR JUST A SMALL CHANCE (30%) OF SHOWERS IN THE MORNING. UPPER TROUGH WILL BE NE OF THE AREA AND FORCING BECOMES INCREASINGLY DOWNWARD INTO THE AFTERNOON. SKIES SHOULD BE MOSTLY CLOUDY THROUGH THE DAY THOUGH. POSSIBLE CLEARING LATE SOUTH OF M-72. TEMPERATURES WILL RANGE FROM THE MIDDLE 40S EASTERN UPPER TO THE LOWER HALF OF THE 50S SOUTH OF M-72. MONDAY NIGHT...NEXT UPPER TROUGH WILL BE EJECTING OUT OF THE NRN ROCKIES WHILE WE GET SOME MID LEVEL RIDGING AND PRECIPITATION FREE WEATHER. POSSIBLY A PEEK AT THE SUN/STARS HEADING THROUGH THE EVENING. THIS IS ALL BEFORE SKIES INCREASE IN CLOUDS AGAIN...AS SIGNALS START TO APPEAR OF INCREASED THETA-E AIR ARRIVE OVERNIGHT AHEAD OF INITIAL ENERGY EJECTING FROM THIS TROUGH AND NEARING WARM FRONT THAT EDGES INTO NRN IL/SRN LK MI. WILL GO MOSTLY CLOUDY ALL AREAS BY LATE OVERNIGHT. AT THE SAME TIME...MODELS ARE STILL POINTING TOWARD A SMALL CHANCE OF PRECIPITATION FOR FAR NW LOWER MICHIGAN AROUND DAYBREAK. MANY QUESTIONS REVOLVE AROUND THE EVOLUTION OF THIS SYSTEM. GFS IS QUITE COOLER THAN NAM AND OTHER MODELS...BUT HAS BEEN THE MODEL OF CHOICE BY SOME. AM NOT SO SURE ABOUT THIS...AS GFS SHOWS A SFC LOW IN NRN IL WITH UPPER TROUGH TOO FAR NW FOR THIS TO MAKE TOTAL SENSE. AS A RESULT...GFS KEEPS MUCH COLDER AIR OVER NRN MICHIGAN COMPARED TO NAM AND OTHER MODELS. REASON FOR ALL OF THIS TALK...WELL IS PRECIP BREAKS OUT THEN IT COULD BE IN THE FORM OF A MIX FOR FAR NRN LOWER. AM GOING TO LEAN MORE SO ON THE SIDE OF WARMER WITH THIS ONE...SO WILL KEEP JUST A CHANCE OF RAIN IN THE FORECAST. TUESDAY...FOLLOWING THIS SAME TRAIN OF THOUGHT...AND FOLLOWING THE POSITION OF THE UPPER TROUGH...STRONGER DYNAMICAL FORCING ARRIVES MORE SO IN THE AFTERNOON. WOULD EXPECT RAIN SHOWERS TO BECOME LIKELY ACROSS THE ENTIRE FORECAST AREA. GFS SEEMS TO BE SUFFERING FROM FEEDBACK ISSUES AFTER LOOKING AT AN ANOMALOUS 70KT LLJ POINTING INTO THE SAG BAY AREA WITH SEEMINGLY TOO STEEP OF MID LEVEL LAPSE RATES BY TUESDAY AFTERNOON. DAY CREW CAN TAKE A CLOSER LOOK AT THIS...AS CURRENT WEATHER KEPT THE FOCUS ON THE SHORTER TERM ISSUES. HOWEVER...WOULD EXPECT A WARMER SOLUTION FOR JUST RAIN AS THE PRECIP TYPE THROUGH TUESDAY...AND LIKELY THUNDERSTORMS SEEMS A BIT OVERDONE AT THIS POINT. TUESDAY NIGHT...UPPER TROUGH STRENGTHENS AND SFC LOW DEEPENS THROUGH THE NIGHT...WHILE MOVING UP INTO OUR NECK OF THE WOODS. PRECIPITATION REMAINS LIKELY...AND COLDER AIR WILL INVADE THE AREA. ODDS HERE FOR A CHANGE IN PRECIP TYPE IS STILL VERY GOOD. WITH STRONG FORCING WHILE THIS IS OCCURRING...PORTIONS OF THE CWA IN ACCUMULATING SNOW IS A DEFINITE POSSIBILITY. WILL HAVE TO BE WATCHING THIS SYSTEM CLOSELY...AS IT SEEMS THAT MOTHER NATURE JUST WANTS TO REMIND US THAT WE ARE IN NRN MICHIGAN IN EARLY APRIL. DOESN`T NECESSARILY MEAN SPRING IS HERE IN EARNEST. LATER PERIODS (WED AND THU)...SURFACE LOW PRESSURE MOVES EAST OF THE AREA...BUT STRONG COLD ADVECTION BEHIND THIS SYSTEM DROPPING 850MB TEMPERATURES BELOW 0C BY 12Z AND -10C BY 00Z THU SPELLS SNOW SHOWERS WITH A GREATER CHANCE WITHIN THE DEFORMATION ZONE ACROSS EASTERN UPPER AND NE LOWER. LATE SEASON LAKE EFFECT THEN CRANKS UP ACROSS THE TYPICAL SNOW BELTS WEDS NIGHT INTO THU AS 850MB TEMPERATURES FALL BETWEEN -13C AND -15C AND DEEP MOISTURE WITHIN THE UPPER LEVEL LOW HANGS ON. THE DEEP MOISTURE THEN PULLS OUT ON THURSDAY AND WOULD SIGNAL A DECREASING TREND IN SNOW SHOWER ACTIVITY...BUT PLENTY OF INSTABILITY WITH DELTA T/S ON THE ORDER OF 15C WILL REMAIN PRESENT. IN GENERAL...A COLD AND SNOWY PERIOD WITH HIGH TEMPERATURES AROUND 15 DEGREES BELOW NORMAL. MPC && .APX WATCHES/WARNINGS/ADVISORIES...NONE. && $$
AREA FORECAST DISCUSSION
NWS GAYLORD MI
135 AM EDT SUN APR 01 2007 .AVIATION...WINDS HAVE BEEN SLOW TO INCREASE OVERNIGHT AND WITH THE WARM AIR ADVECTION, WILL PUT IN LOW LEVEL WIND SHEAR. BASED ON THE KAPX 88D WILL ALLOW FOR WIND SHEAR AROUND 2000 FEET OF 40 KNOTS WHILE THE SFC IS AROUND 10 KNOTS. OTHERWISE THE MAIN CONCERN IS THE TIMING OF THE RAIN AND THUNDER CHANCES THROUGH THE OVERNIGHT HOURS. ADDITIONALLY...EXPECT THE DRY SLOT TO MOVE INTO THE REGION BY 12Z AROUND TVC (BY 16Z AT APN) AND CREATE A TEMPORARY PERIOD OF VFR CONDITIONS THROUGH EARLY AFTERNOON. THEREAFTER...DEEPER MOISTURE...LIGHT SHOWERS...AND MVFR CONDITIONS MOVE BACK IN AND WILL BE PRESENT THROUGH THE EVENING HOURS. LUTZ/MPC && .UPDATE...ISSUED AT 1044 PM EDT SAT MAR 31 JUST TWEAKED THE FORECAST OVERNIGHT AS THE RAIN LOOKS TO BE ON TRACK WITH THE LATEST WAVE MOVING INTO NW LOWER. THE 850 MB WARM SECTOR WILL BE MOVING OUT TO THE REGION OVERNIGHT AND WITH IT THE 850 MB MOISTURE WILL BE MOVING IN. 00Z NAM IS SHOWING THE 850 TEMPERATURES FALLING QUICKLY, AND BOTH ARE WARMER BY 1C THAN THE ACTUAL TEMPERATURE FROM 00Z (7C). SO WITH THE TEMPERATURES STARTING LOWER AND FALLING AT 850 MB WILL EXPECT THAT THE LAPSE RATES WILL BE LESS THAN EXPECTED. SO THE FORECAST LOOKS GOOD. LUTZ && PREV DISCUSSION... /ISSUED 350 PM EDT SAT MAR 31 2007/ DISCUSSION...SHORT TERM ISSUES (TONIGHT)...SOUTHERN BRANCH SHORT WAVE TROUGH...PART OF UPSTREAM SPLIT FLOW PATTERN...LIFTING NORTH ACROSS EASTERN NE THIS AFTERNOON. 18Z SURFACE ANALYSIS SHOWS 997MB LOW CONSOLIDATING NEAR OMA...WHICH WILL UNDERGO OCCLUSION STARTING THIS EVENING AS IT MOVES NORTHEAST AND EVENTUALLY INTO SOUTHERN MN BY SUNDAY MORNING. ASSOCIATED WARM/OCCLUDED FRONT WILL ALSO LIFT NORTH ACROSS THE LOWER PENINSULA TONIGHT...REACHING FAR NORTHERN LOWER MI BY SUNDAY MORNING (AND MAY END UP STAYING THERE THROUGH SUNDAY AS USUALLY HAPPENS WITH SOUTHEAST FLOW OFF LAKE HURON). REALLY NO PRECIPITATION ACROSS NORTHERN MI THIS AFTERNOON...AS AIRCRAFT SOUNDINGS CONFIRM MUCH DRIER MID LEVELS THAN THIS MORNING. RECENT SOUNDING OUT OF APN SATURATED IN THE 850-650MB LAYER...BUT AT TEMPERATURES ABOVE -3C. MORE SUBSTANTIAL SHOWER/ THUNDERSTORM ACTIVITY DEVELOPING ACROSS WI/IA/IL...ALL OF WHICH SHOULD PIVOT NORTHEAST AND SWEEP ACROSS NORTHERN MI TONIGHT. EXPECT PRECIPITATION TO BE FAIRLY WIDESPREAD GIVEN JUXTAPOSITION OF DEEP LAYER FORCING AND LOW LEVEL MOIST INFLOW AXIS...SO HIGH POPS JUSTIFIED ALONG WITH SOME EMBEDDED THUNDER ACROSS PARTS OF NORTHERN LOWER THOUGH BETTER ELEVATED INSTABILITY WILL BE SOUTH OF THE FORECAST AREA. JPB LONG TERM ISSUES...SUNDAY INTO SUNDAY NIGHT...INITIAL WAVE OF WARM ADVECTION PRECIP SHOULD BE PRETTY MUCH NORTH OF THE CWA BY 12Z SUNDAY AS PRONOUNCED DRY SLOT PUNCHES NORTHEAST IN ASSOCIATION WITH DEEPLY OCCLUDING CYCLONE. MOMENTUM OF APPROACHING DRY SLOT SHOULD EASILY FORCE SURFACE WARM FRONT THROUGH MUCH OF THE CWA...THOUGH EXPECT WARM SURGE LIKELY TO GET HUNG UP ACROSS EASTERN UPPER AS IS TYPICAL FOR THESE SYSTEMS. TO THE SOUTH OF WHERE THE BOUNDARY ENDS UP...IT IS SHAPING UP TO BE A RATHER NICE EARLY SPRING DAY WITH AT LEAST PERIODS OF SUN EXPECTED MAINLY MORNING THROUGH EARLY AFTERNOON AS DRY AIR WINS OUT WITH ENHANCED MIXING. IN THESE AREAS...COULD EASILY SEE TEMPS IN THE 60S PENDING DEGREE OF SUNSHINE...THOUGH EXPECT STRATOCU WILL FILL IN QUICKLY BY AFTERNOON WITH REMNANT BOUNDARY LAYER MOISTURE PRESENT AND STEEP LOW LEVEL LAPSE RATES. TO THE NORTH...CLOUDS AND LINGERING SHOWERS A POSSIBILITY...HENCE WILL HOLD NUMBERS DOWN QUITE A BIT IN THESE AREAS...AND COULD FORESEE A DAY STUCK AROUND 40 WITH PERSISTENT SOUTHEASTERLY LOW LEVEL FLOW THOUGH DRY SLOT IMPRESSIVE AND MAY SIMPLY DISPLACE LOW LEVEL MOISTURE. MAIN ACTION FOR TOMORROW APPEARS TO BE DURING THE AFTERNOON AS DEEP CLOSED LOW/NEGATIVE TILT UPPER TROUGH LIFTS ACROSS THE REGION...WITH PRONOUNCED MID LEVEL COOLING AS UPPER COLD POOL DRIFTS OVERHEAD. SUBSEQUENT STEEPENING OF LOW AND MID LEVEL LAPSE RATES COUPLED WITH APPROACH OF SURFACE OCCLUDED FRONT AND MID LEVEL IMPULSE/SPEED MAX ROTATING AROUND THE MAIN UPPER LOW SHOULD BE ENOUGH TO SPARK ADDITIONAL SHOWERS AND THUNDERSTORMS. GIVEN SUCH COLD MID LEVELS...A HAIL THREAT NATURALLY EXISTS WITH ANY ORGANIZED STORMS THAT FIRE...AND WINDS FIELDS ALSO QUITE IMPRESSIVE WITH 0-6KM DEEP SHEAR PROGGED AT 40 TO 45 KNOTS PER AIDED BOOST FROM H5 SPEED MAX. ONLY INGREDIENT PERHAPS LACKING PENDING DEGREE OF CLOUD COVER WILL BE SURFACE HEATING...THOUGH SUSPECT EVEN WITH MINIMAL HEATING A FEW STORMS SHOULD BE ABLE TO FIRE IN COLD POOL. LATEST SPC DAY 2 OUTLOOK APPEARS REASONABLE AND WILL CONTINUE MENTION OF HAIL/WIND POSSIBILITIES IN HWO. ALSO APPEARS TO BE A RATHER BREEZY DAY IN THE PRESENCE OF GOOD LOW LEVEL MIXING AND STOUT JET ALOFT...WITH MOMENTUM TRANSFER PROFILES OFF FORECAST RAOBS INDICATING PLENTY OF GUSTS TO AROUND 30 KNOTS OVER LAND...THOUGH STABLE MARINE LAYER SHOULD PREVENT MUCH IN THE WAY OF STRONG WINDS OVER WATER. LINGERING AREA OF CHANNELED VORTICITY/WEAK QG FORCING ON THE SOUTHERN END OF DEPARTING WAVE LIKELY TO KEEP A FEW SHOWERS GOING INTO SUNDAY NIGHT AND PERHAPS EARLY INTO MONDAY IN THE PRESENCE OF WEAK COLD ADVECTION. COULD SEE A LITTLE ENHANCED PRECIP ALONG THE LAKE MICHIGAN SHORELINE THIS TIME FRAME GIVEN AREA OF MAXIMIZED LOW LEVEL CONVERGENCE IN WESTERLY FLOW. ANYTHING REMAINING WILL SHUT DOWN LATE MONDAY INTO MONDAY NIGHT WITH WEAK SURFACE RIDGE DRIFTING THROUGH THE REGION WHILE SHORTWAVE RIDGING BUILDS ALOFT IN ADVANCE OF NEXT APPROACHING WAVE. TUESDAY...ANOTHER ACTIVE PERIOD OF WEATHER EXPECTED THIS TIME FRAME AS PATTERN BEGINS TO AMPLIFY ACROSS THE COUNTRY. SHORTWAVE COMING ONSHORE OVER THE PACIFIC NORTHWEST ON MONDAY WILL WORK EAST QUICKLY IN FAST NORTHERN STREAM AND BEGIN TO AMPLIFY AS DEEP TROUGHING DEVELOPS OVER THE EASTERN PACIFIC INTO THE GULF OF ALASKA...ALLOWING UPPER RIDGING TO DEVELOP OVER THE PACIFIC COAST STATES. STILL HAVE SOME DOUBTS ABOUT THE DEGREE OF AMPLIFICATION SHOWN SO EARLY BY THE GFS...AS FLOW REMAINS RATHER PROGRESSIVE AND BOTH GFS ENSEMBLES AND 00Z RUN OF THE ECMWF AS WELL AS THE 00Z GFS PARALLEL RUN SHOW A SLOWER AMPLIFICATION TO SYSTEM. IN EITHER CASE...SHOULD SEE LEE CYCLOGENESIS TAKE SHAPE OVER THE CENTRAL PLAINS IN ADVANCE OF APPROACHING WAVE LATE MONDAY...WITH DEVELOPING WARM FRONT LIFTING NORTH INTO SOUTHERN MICHIGAN ON TUESDAY. FAIRLY POTENT WARM ADVECTION OUT AHEAD OF THE WAVE AND TIGHTENING BAROCLINIC GRADIENT ALOFT SHOULD PRODUCE A FRONTOGENETICALLY FORCED BAND OF PRECIP NORTH OF THE LIFTING WARM FRONT...ESPECIALLY AS BEST DYNAMICS APPROACH WITH INCREASINGLY DIFLUENT MID/UPPER LEVEL FLOW. STILL QUITE A FEW QUESTIONS TO BE ANSWERED REGARDING THE EXACT TRACK OF THIS SYSTEM AND ITS ASSOCIATED SURFACE REFLECTION. GFS OPERATIONAL AND ENSEMBLE MEAN PLOT OF MSLP WOULD SUGGEST A TRACK ALONG THE WARM FRONT OVER SOUTHERN MICHIGAN...WHILE THE LESS AMPLIFIED AND SLIGHTLY MORE PREFERRED ECMWF PLACES THE TRACK THROUGH THE NORTHERN OHIO VALLEY. EITHER OUTCOME PRETTY MUCH PLACES THE MAJORITY OF THE CWA NORTH OF THE WARM FRONT...WITH COOL EASTERLY FLOW PREVAILING AND TEMPS STRUGGLING TO CLIMB UNDER LIKELY PRECIP. HOWEVER...THIS SUBJECT TO CHANGE SHOULD SYSTEM TAKE ANY NORTHWARD JUMPS...WHICH COULD PUT THE SOUTHERN CWA IN THE WARM SECTOR. PERHAPS THE BIGGEST ISSUE WITH THIS SYSTEM (OTHER THAN PLACEMENT OF FEATURES) WILL BE CONVECTIVE POTENTIAL TUESDAY AFTERNOON/EVENING AS WELL AS SOME POTENTIAL FOR PRECIP TYPE ISSUES OVER THE FAR NORTH. INCREASING LAPSE RATES WITH ONGOING WARM ADVECTION DOWN LOW AND APPROACHING COOL POOL IN ASSOCIATION WITH THE WAVE SHOULD BRING AT LEAST SOME THREAT FOR STORMS MAINLY SOUTHERN CWA CLOSEST TO AXIS OF DEEPER MOISTURE...AND WILL MAINTAIN A MENTION OF THIS POSSIBILITY. FARTHER NORTH...PTYPE ISSUES MAY ARISE AS PRECIP OVERRUNS RESIDUAL COLD AIR LEFT FROM PASSAGE OF INITIAL SUNDAY SYSTEM. FORECAST RAOBS INDICATE PRECIP COULD START AS SNOW OVER EASTERN UPPER THOUGH WOULD ANTICIPATE A CHANGEOVER AS WARMING COMMENCES ALOFT. THIS THREAT HIGHLY DEPENDENT ON TRACK OF SYSTEM...AND GIVEN SO MUCH UNCERTAINTY PREFER TO KEEP THINGS ALL LIQUID FOR NOW. TUESDAY NIGHT INTO WEDNESDAY...PTYPE BECOMES MUCH EASIER TUESDAY NIGHT AND ESPECIALLY WEDNESDAY AS UPPER VORTEX PINCHES OFF OVER SOUTHEAST CANADA OWING TO A HIGH AMPLIFICATION OF WESTERN CONUS RIDGE. THIS WILL ALLOW FOR A VERY COLD AIRMASS TO DROP INTO THE REGION WITH ANY RESIDUAL PRECIP TAKING THE FORM OF SNOW. THIS IS WHERE THE FORECAST GETS EVEN MORE TRICKY AS THE GFS DEPICTION OF ALREADY CLOSED LOW TUESDAY NIGHT WOULD SUGGEST ACCUMULATING SNOW POSSIBLE MAINLY NORTH UNDER DEFORMATION AXIS AS UPPER LOW SLOWLY PINWHEELS EAST. AS MENTIONED EARLIER...APPEARS GFS TOO QUICK TO CUT OFF SYSTEM SO FAR WEST AND BELIEVE A MORE OPEN/PROGRESSIVE LOOK TO SYSTEM IN ORDER...THUS DIMINISHING OVERALL THREAT. HOWEVER...12Z ECMWF COMING IN WITH SIMILAR SCENARIO...SO SOMETHING TO BE WATCHED FOR SURE. ATTENTION THEREAFTER TURNS TO LAKE EFFECT POTENTIAL BY WEDNESDAY AFTERNOON AS STRONG COLD ADVECTION COMMENCES...THOUGH APPEARS ANY ACCUMULATIONS WEDNESDAY MINIMAL AS COLDEST H85 AIR YET TO ARRIVE. WEDNESDAY NIGHT THROUGH SATURDAY...AN EXTENDED PERIOD OF WINTRY WEATHER STILL APPEARS ON TRACK FOR THIS TIME FRAME. WITH DEEP VORTEX FIRMLY ENTRENCHED OVER SOUTHEAST CANADA AND UPPER RIDGING IN PLACE OVER THE WEST...THE FLOODGATES WILL BE OPENED FOR AN IMPRESSIVE INTRUSION OF COLD AIR INTO THE EASTERN HALF OF THE COUNTRY. ENSEMBLE MEAN H85 TEMPS CONTINUE TO SUGGEST SEVERAL SURGES OF -12C TO -18C AIR DROPPING INTO THE GREAT LAKES...SUGGESTING INCREASINGLY FAVORABLE DELTA T/S FOR LAKE EFFECT SNOW PRODUCTION DESPITE LAKES AT CLIMATOLOGICAL MINIMUM TEMPS. COUPLED WITH OVERALL CYCLONIC FLOW AND COLD POOL ALOFT AS WELL AS QUITE DEEP MOISTURE PROGGED BY ALL MODEL GUIDANCE...ACCUMULATING LAKE EFFECT STILL APPEARS IN ORDER AS WELL AS TEMPERATURES WELL BELOW NORMAL. THE MAIN PROBLEM CONTINUES TO BE DIRECTION OF LOW LEVEL FLOW...BUT TREND OF MODEL GUIDANCE SUGGESTS PRIMARILY A NORTHWEST TO NORTHERLY FLOW EVENT IN THE WORKS. WILL MAINTAIN GOING MENTION IN THE HWO FOR THIS POTENTIAL. LAWRENCE && .APX WATCHES/WARNINGS/ADVISORIES... NONE. && $$
AREA FORECAST DISCUSSION...UPDATED
NWS FORT WORTH TX
1232 PM CDT MON APR 2 2007 .AVIATION... VISIBLE SATELLITE LOOPS SHOW BREAKS IN THE LOW CLOUDS...BUT WE WILL SEE AT LEAST TEMPO BKN015-020 AT THE TAF SITES THROUGH 21Z. AFTERWARDS...WE SHOULD SEE VFR CONDITIONS LATE AFTERNOON THROUGH THE EVENING HOURS. WITH BETTER MIXING...WE WILL SEE SOUTHERLY WINDS AROUND 15 KNOTS...WITH SOME GUSTS OVER 20 KNOTS POSSIBLE THROUGH SUNSET. LOW CLOUDS WILL OVERSPREAD THE REGION AFTER 05Z AT WACO... AND 07Z AT THE METROPLEX SITES...WITH IFR CONDITIONS LIKELY 11-17Z AT WACO. SHOWER/THUNDERSTORM CHANCES ARE WAY TOO LOW TO MENTION IN THE TAFS AT THIS TIME. #58 && .PREV DISCUSSION... /ISSUED 1106 AM CDT MON APR 2 2007/ DISCUSSION...QUICK UPDATE TO THE FORECAST TO MAKE SOME MINOR ADJUSTMENTS TO SKIES/TEMPS/WINDS THROUGH THE AFTERNOON. 15Z ACARS SOUNDINGS FROM DFW SHOW 20-30KTS OF WIND JUST ABOVE THE SURFACE. LOW CLOUDS WILL CONTINUE TO ERODE THROUGH EARLY AFTERNOON...AND EXPECT WARM BREEZY CONDITIONS BY AFTERNOON. THERE IS A SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS THIS AFTERNOON...MAINLY ACROSS THE SOUTHERN TWO-THIRDS OF THE CWA. THERE IS SUFFICIENT INSTABILITY ACROSS THE REGION...BUT A LACK OF LARGE SCALE FORCING OR NOTICEABLE SFC BOUNDARIES SHOULD PRECLUDE WIDESPREAD CONVECTION. 91/DUNN PREV DISCUSSION... /ISSUED 400 AM CDT MON APR 2 2007/ LOW LEVEL MOISTURE WILL RAPIDLY INCREASE ACROSS NORTH TEXAS TODAY AS A SURFACE LOW PRESSURE SYSTEM DEEPENS LEE OF THE ROCKIES. THE SURFACE PRESSURE GRADIENT WILL ALSO TIGHTEN AND RESULT IN INCREASING SOUTHERLY WINDS. A WEAK WAVE EMBEDDED IN WESTERLY FLOW ALOFT WILL BRING A SLIGHT CHANCE OF SHOWERS/STORMS TO THE SOUTHERN ZONES THIS MORNING AND ACROSS THE SOUTH AND EAST THIS AFTERNOON. A BETTER CHANCE OF SHOWERS AND THUNDERSTORMS IS EXPECTED TUESDAY AFTERNOON AND TUESDAY NIGHT WHEN A COLD FRONT AND ANOTHER SHORT WAVE MOVE ACROSS NORTH TEXAS. PRECIPITATION CHANCES WILL LINGER INTO WEDNESDAY IN THE SOUTH. FORECASTED INSTABILITY STILL LOOKS FAVORABLE FOR SOME SEVERE STORMS WITH HAIL AND DOWNBURST WINDS POSSIBLE TUESDAY AFTERNOON THROUGH WEDNESDAY. TEMPORARY RIDGING ALOFT AND DRIER AIR WILL LIMIT STORM DEVELOPMENT THURSDAY. HOWEVER...ANOTHER SHORT WAVE AND COLD FRONT WILL MOVE ACROSS THE REGION FRIDAY AND BRING A CHANCE OF RAIN AND THUNDERSTORMS. LOOKING AHEAD...THE UPPER PATTERN IS PROGGED TO STAY PROGRESSIVE WITH ADDITION RAIN CHANCES NEXT WEEK. AFTER A WARM START TO THE WEEK...TEMPERATURES WILL COOL TO NEAR OR BELOW SEASONAL NORMALS FROM MID WEEK THROUGH THE WEEKEND. 79 FWD WATCHES/WARNINGS/ADVISORIES... NONE. && .PRELIMINARY POINT TEMPS/POPS... DALLAS-FT. WORTH, TX 80 67 80 54 67 / 10 10 20 40 20 WACO, TX 80 68 82 59 65 / 20 10 20 50 30 PARIS, TX 81 65 79 53 64 / 20 10 30 40 20 DENTON, TX 83 65 80 53 66 / 10 10 20 30 20 MCKINNEY, TX 80 66 81 52 65 / 10 10 20 40 20 DALLAS, TX 83 69 83 56 68 / 10 10 20 50 20 TERRELL, TX 82 67 81 56 68 / 10 20 20 50 20 CORSICANA, TX 80 67 82 58 65 / 20 20 20 50 40 TEMPLE, TX 83 66 83 61 70 / 20 10 20 40 30 && .FWD WATCHES/WARNINGS/ADVISORIES... NONE. && $$ 58/91/58
AREA FORECAST DISCUSSION
NWS CHICAGO IL
420 AM CDT TUE APR 3 2007 .DISCUSSION... 420 AM CDT WARM FRONT HAS BEEN SLOWLY LIFTING THROUGH NORTHERN IL EARLY THIS MORNING AND CURRENTLY EXTENDS FROM DAVENPORT TO JOLIET TO SOUTH OF VALPARAISO. OUTFLOW FROM CONVECTIVE CLUSTER ACROSS SOUTHERN WI SEEMS TO BE HINDERING ANY FURTHER ADVANCE OF BOUNDARY FOR THE TIME BEING. RADAR COMPOSITE AND SATELLITE LOOPS INDICATE A CONVECTIVE VORT MAX MOVING ACROSS SOUTHEAST WI WITH A RELATIVE DECREAE IN TSRA ACTIVITY BUT STRONG WAA AT NOSE OF 50 TO 75KT LOW LEVEL JET OUT OF THE SOUTHERN PLAINS AND ACROSS THE LOWER MO VALLEY PER PROFILER NET CONTINUES TO INITIATE NOEW ACTIVITY IN NORTHEAST IA...NORTH OF THE BOUNDARY. UPPER LOW CURRENTLY OVER THE DAKOTAS TO DEEPEN AS IT MOVES EAST TO MN BY THIS EVENING...WHILE SURFACE LOW MOVES QUICKLY EAST NORTHEAST ACROSS IA...FAR NORTHWEST IL AND SOUTHEAST WI...TO SOUTHERN LAKE BY LATE AFTERNOON. ASSOCIATED COLD FRONT TO RACE EAST TO THE MS RIVER BY LATE MORNING AND CONTINUE QUICKLY ACROSS IL DURING THE AFTERNOON. STRONG LOW LEVEL FLOW OF WARM MOIST AIR AHEAD OF THE COLD FRONT...COMBINED WITH STRONG HEATING WITH MOSTLY CLEAR SKY IN WARM SECTOR UNDER STEEP MID LEVEL LAPSE RATES RESULTS IN SBCAPE REACHING 1500+ J/KG FROM NORTHERN IND SOUTHWESTWARD TO SOUTHEASTERN MO BY EARLY AFTERNOON...WHERE SPC HAS MOD SEVERE RISK OUTLOOKED. LINE OF TSRA ALREADY REACHING FROM SOUTHWEST IA ACROSS NORTHWEST MO INTO NORTHEAST KS. EXPECTED TO CONTINUE TO DEVELOP AHEAD OF THE COLDFRONT AND SWEEP ACROSS THE FA DURING THE LATE MORNING AND AFTERNOON. BY LATE AFTERNOON THE SQUAL LINE WILL BE MOVING INTO NORTH CENTRAL AND WEST CENTRAL IND. VERY COOL AIR IN PLACE ACROSS CANADA HAS ALREADY STARTED TO SPREAD SOUTH BEHIND THE CENTRAL U.S. SYSTEM WITH CURRENT TEMPS ACROSS THE NORTHERN PLAINS ONLY IN THE TEENS AND 20S. STRONG COLD AIR ADVECTION SPREADS ACROSS THE UPPER MIDWEST AND MID MS VALLEY AS THE UPPER SYSTEM MOVES TO THE WESTERN GREAT LAKES TONIGHT. THE UPPER LOW THEN ONLY VERY SLOWLY MOVES EAST ACROSS THE LAKES WED AND THU...WITH THE UPPER TROUGH DEEPENING OVER THE CENTRAL AND EASTERN U.S. LATE WEEK AND INTO THE WEEKEND MAINTAINING THE FEED OF COLD AIR OUT OF CANADA AND ACROSS THE REGION WITH DAYTIME TEMPS MAINLY IN THE 30S AND LOWS IN THE 20S. TRS && .AVIATION... 133 AM CDT THE WARM FRONT LIES FROM DAVENPORT IOWA TO KANKAKEE ILLINOIS. AN 850 MB JET STREAK LIES OVER CENTRAL IOWA AT 05 UTC. THIS IS SEEN USING THE PROFILER AND VAD WIND PROFILE DATA. 50 KNOT 850 MB WIND WAS OVER WESTERN ILLINOIS. SHOWERS AND THUNDERSTORMS ARE ALONG THE WISCONSIN BORDER AT 0550 UTC AND EXTEND AS FAR SOUTH AS ROCKFORD ILLINOIS AND NORTHERN COOK COUNTY ILLINOIS. THE FORECAST SOUNDING FROM THE LOCALLY RUN WRF ARW SHOW THE MAXIMUM INSTABILITY FOR ROCKFORD TO BE BY 00 UTC THIS TUESDAY. THE ACARS SOUNDING FROM ROCKFORD SHOWS AN INVERSION AROUND 879 MB. WILL LEAVE THUNDER IN THE TAFS FOR ORD AND RFD SINCE THE THUNDERSTORMS ARE NEAR BOTH AIRPORTS. THE BIGGEST CHANCE OF THUNDERSTORMS WILL BE THIS AFTERNOON. AT THE TIME OF MAXIMUM INSTABILITY. WE WILL WATCH AN MCS OVER WESTERN IOWA AS WELL FOR POSSIBLE THUNDERSTORMS IN THE MORNING. WITH A 50 KNOT JET STREAK THERE IS ENOUGH WARM AIR ADVECTION AT AT 850 MB TO MAINTAIN A MCS. WILL KEEP THE 2500 FT CEILING AFTER 22 UTC. THEN LATER...WHEN THE COLD AIR ARRIVES WE WILL ADD LIGHT SNOW TO THE FORECAST. THE WIND SHIFT IS EXPECTED AROUND 00 UTC WEDNESDAY TO THE WEST AND NORTHWEST. && .LOT WATCHES/WARNINGS/ADVISORIES... .IL...NONE. .IN...NONE. .LM...GALE TONIGHT THRU WED. && $$
AREA FORECAST DISCUSSION
NWS CHICAGO IL
135 AM CDT TUE APR 3 2007 .UPDATE... 915 PM CDT WARM FRONT EXTENDING FROM NEAR RENSSELAER TO PEORIA AND WESTWARD ALONG THE IOWA AND MISSOURI STATELINE AS OF 02Z SFC ANALYSIS. MCS DEVELOPING ALONG THIS BOUNDARY OVER CENTRAL NE SHOULD CONTINUE PROPOGATING EASTWARD ALONG THE FRONT THROUGH THE NIGHT...AND IF IT SURVIVES ...WOULD REACH NRN IL TOWARD SUNRISE. LLJ EXPECTED TO INCREASE TO 50 KTS AS AXIS SHIFTS FROM PRESENT LOCATION OVR WRN IA TOWARD NRN IL AFT MIDNIGHT NUDGING WARM FRONT SLOWLY NWD THROUGH THE OVERNIGHT HRS. A FEW SEVERE STORMS EXPECTED LATE AS DEEP LAYER SHEAR FAVORABLE FOR ORGANIZED CONVECTION WHILE BAND OF 1000-2000 J/KG SURGES NEWD TOWARD THE LOCAL AREA. HAIL SHOULD BE MOST PREDOMINANT SVR THREAT NORTH OF THE FRONT...BUT MAY SEE A FEW STRONG WIND GUSTS WHERE STORMS ARE CLOSER TO BEING SFC BASED SOUTH OF INTERSTATE 80...ESPECIALLY TOWARD MORNING WHEN WIND PROFILES BECOME MORE UNIDIRECTIONALLY SHEARED AND STRONGEST ISENTROPIC ASCENT/MID LEVEL SHORTWAVE SHIFTS ACROSS THE LOCAL AREA. FORECAST APPEARS TO BE ON TRACK... SO NO UPDATES PLANNED. RRH && .DISCUSSION FOR AFTERNOON GRIDS... 405 PM CDT WELL...MARCH CAME IN LIKE AND LION AND WENT OUT LIKE A LION. APRIL LOOKS TO BE THE SAME SITUATION. FOR THE SHORT TERM...THE MAIN CONCERN...PARTICULARLY FOR THE OVERNIGHT HOURS WILL BE THUNDER POTENTIAL. THE NAM AND GFS ARE IN DECENT AGREEMENT ON HANDLING THE DEVELOPMENT OF A SFC LOW OVER THE CENTRAL PLAINS. THE GFS IS TRENDING A LITTLE FASTER AND SLIGHTLY STRONGER...BUT THE MINOR DIFFERENCES BETWEEN MODELS SHOULD NOT HAVE SIGNIFICANT DIFFERENCE ON THE SENSIBLE WEATHER FEATURES. THE LATEST SATELLITE IMAGERY SHOWS WARM ADVECTION CLOUDS DEVELOPING ON THE WARM FRONT SETTING UP ACROSS THE CENTRAL PLAINS. THE INITIAL ROUND OF CONVECTIVE ACTIVITY SHOULD BE ELEVATED CONVECTION NORTH OF THE WARM FRONT. HAVE ADJUSTED THE GOING FORECAST GRIDS TO MENTION T+ OVER THE NORTHWESTERN COUNTIES FOR THE PERIOD AFTER MIDNIGHT. BY TOMORROW MORNING...THE WARM SECTOR AND COLD FRONT WILL BECOME THE FOCUS OF TS ACTIVITY. A LIMITING FACTOR FOR TS AND POTENTIAL SEVERE TS TOMORROW WILL BE THE RACE FOR THE RETURN OF HIGHER DEWPOINT AIR IN THE WARM SECTOR. FOR THE INITIAL ROUND OF TS OVERNIGHT...THE WARM FRONT SHOULD PROVIDE ADEQUATE ISENTROPIC LIFT...BY BY MORNING...THE WARM FRONTAL BOUNDARY WILL BE WELL TO THE NORTH. CURRENT OBS SHOW DEWPOINTS ACROSS THE CWA TO BE IN THE LOW TO MIDDLE 40S...WITH LOW LEVEL TRAJECTORIES TAKING A LONG PATH AROUND THE SFC HIGH CENTERED OVER THE SRN APPALACHIANS. DURG THE MORNING HOURS TOMORROW...THE HIGH WILL SHIFT OFF THE SERN ATLANTIC COAST AND SLY LOW LEVEL FLOW WILL INCREASE MOISTURE ADVECTION...BRINGING DEWPOINTS WELL INTO THE 50S. BUT THE COLD FRONT WILL ALSO BE ACCELERATING OUT OF THE NRN PLAINS AND WILL SWEEP ACROSS THE REGION TOMORROW AFTERNOON. CURRENTLY FEEL THAT THE FRONT WILL SWEEP ACROSS THE CWA BY AROUND 18Z...SO THE BEST OPPORTUNITY FOR ANY SGFNT TS WILL BE OVER BY THE EARLY AFTERNOON HRS...BEFORE TIME OF MAX HEATING. FOLLOWING THE FROPA...SIGNIFICANT LATE SEASON COLD AIR WILL OVERSPREAD THE CWA. HAVE ADJUSTED TEMPS AND ASSD PCPN COLDER THAN THE PREVIOUS FORECAST PACKAGE. THE MAIN CONCERN WILL SHIFT FROM TS TO STRONG WINDS...LOWER TEMPS AND LIGHT SNOW. THE GUIDANCE IS IN GOOD AGREEMENT ON THE PATH OF THE MAIN SFC LOW...TRACKING THROUGH NRN IL/IN AND INTO LOWER MICHIGAN AND LAKE HURON. THE LOW IS EXPECTED TO BECOME NEARLY STATIONARY OVER LAKE HURON WHILE STRONG HIGH PRESSURE BUILDS OVER THE NRN PLAINS. THIS WILL SET UP STRONG COLD ADVECTION AND A STRONG PRESSURE GRADIENT ACROSS THE CWA...DRIVING STRONG...GUSTY WINDS TO NEAR WIND ADVISORY CRITERIA LEVELS. FOR WEDNESDAY...THROUGH THE END OF THE FORECAST PERIOD...EXPECTING UNSEASONABLY COOL...WINDY CONDITIONS. WHILE NOT EXPECTING A SIGNIFICANT AMOUNT OF QPF FOR THE PERIODS FOLLOWING THE COLD FRONTAL PASSAGE...THE AIRMASS WILL BE COOL ENOUGH THAT MUCH OF THE PCPN FALLING SHOULD BE ALL OR MOSTLY SNOW...AND NOT EXPECTING MUCH...IF ANY ACCUMULATION. KREIN && .AVIATION... 133 AM CDT THE WARM FRONT LIES FROM DAVENPORT IOWA TO KANKAKEE ILLINOIS. AN 850 MB JET STREAK LIES OVER CENTRAL IOWA AT 05 UTC. THIS IS SEEN USING THE PROFILER AND VAD WIND PROFILE DATA. 50 KNOT 850 MB WIND WAS OVER WESTERN ILLINOIS. SHOWERS AND THUNDERSTORMS ARE ALONG THE WISCONSIN BORDER AT 0550 UTC AND EXTEND AS FAR SOUTH AS ROCKFORD ILLINOIS AND NORTHERN COOK COUNTY ILLINOIS. THE FORECAST SOUNDING FROM THE LOCALLY RUN WRF ARW SHOW THE MAXIMUM INSTABILITY FOR ROCKFORD TO BE BY 00 UTC THIS TUESDAY. THE ACARS SOUNDING FROM ROCKFORD SHOWS AN INVERSION AROUND 879 MB. WILL LEAVE THUNDER IN THE TAFS FOR ORD AND RFD SINCE THE THUNDERSTORMS ARE NEAR BOTH AIRPORTS. THE BIGGEST CHANCE OF THUNDERSTORMS WILL BE THIS AFTERNOON. AT THE TIME OF MAXIMUM INSTABILITY. WE WILL WATCH AN MCS OVER WESTERN IOWA AS WELL FOR POSSIBLE THUNDERSTORMS IN THE MORNING. WITH A 50 KNOT JET STREAK THERE IS ENOUGH WARM AIR ADVECTION AT AT 850 MB TO MAINTAIN A MCS. WILL KEEP THE 2500 FT CEILING AFTER 22 UTC. THEN LATER...WHEN THE COLD AIR ARRIVES WE WILL ADD LIGHT SNOW TO THE FORECAST. THE WIND SHIFT IS EXPECTED AROUND 00 UTC WEDNESDAY TO THE WEST AND NORTHWEST. && .LOT WATCHES/WARNINGS/ADVISORIES... .IL...NONE. .IN...NONE. .LM...NONE. && $$