
FXUS63 KMKX 012123 AFDMKX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI 323 PM CST MON DEC 1 2008 .SHORT TERM...EXPECT STRATUS TO DISSIPATE MAINLY THIS EVENING AS SUBSIDENCE AND DRYING CONTINUES AND SFC RIDGE APPROACHES FROM THE WEST. WITH CLEARING SKIES AND LIGHTER WINDS TRENDED LOW TEMPS TOWARD THE COLDER ETA MOS GUIDANCE. FOR TUE STRONG WARM ADVECTION IS PROGGED AHEAD OF NEXT APPROACHING UPPER TROUGH FROM CANADA. BREEZY SLY WINDS AND A 40-50 KT LLJ WILL WARM 850 MB TEMPS TO 0 TO 3C WHILE 1000-500 MB THICKNESSES RISE TO 540 TO 546 DM. KEPT HIGH TEMPS A LITTLE COOLER THAN GUIDANCE DUE TO SNOW COVER AND SOME MID TO HIGH CLDS FROM WAA. WINDS WILL REMAIN SLY FOR MOST OF TUE NT AND CLOUDS WILL INCREASE FROM APPROACHING SHORTWAVE AND CDFNT OVER MN. APPROACHING UPPER TROUGH HAS TIGHT TROPOSPHERIC GRADIENT AND THUS THE POTENTIAL FOR DECENT MID LVL FRONTOGENESIS. THIS WILL BEGIN LATE ESPECIALLY OVER THE NW CWA AND THEN SHIFT EWD ACROSS ALL OF SRN WI ON WED. GFS IS MOST ROBUST WITH DIGGING AND AMPLIFYING OF SHORTWAVE RESULTING IN RELATIVELY GOOD FRONTOGENESIS AND Q-VECTOR CONVERGENCE...WHICH INCREASES OVER ERN WI. RIGHT ENTRANCE REGION OF JET STREAK MAY ALSO SET UP OVER ERN WI RESULTING IN DEEP OVERALL LIFT. OTHER MODELS HOWEVER ARE WEAKER WITH LIFT AND QPF AND DURATION OF HEAVIEST SNOW WILL BE SHORT. WENT WITH THE LOWER QPF OF HPC AND SREF WHICH IS 0.20 TO 0.25 INCHES. COBB AND ROEBBER TECHNIQUES ALONG WITH 1000-500 MB THICKNESSES ALL SUPPORT RATIOS AROUND 13 TO 1. THIS PRODUCES AROUND 2 INCHES IN THE FAR NW CWA TO NEARLY 4 IN THE FAR SE CWA. GARCIA METHOD WOULD YIELD 5 TO 6 INCHES GIVEN MIXING RATIOS OF 2.5-3.0 G/KG BUT WITH SPEED OF SYSTEM WILL CUT THAT NEARLY IN HALF. STRONG COLD ADVECTION WED AFT AND NT WILL DRY OUT ATM QUICKLY WITH MAINLY FLURRIES LEFT FOR WED NT. .LONG TERM...12Z GFS AND 00Z ECMWF IN VERY GOOD AGREEMENT INTO NEXT WEEK. THEREFORE...NW FLOW PATTERN AND BELOW NORMAL TEMPS TO CONTINUE. ALSO UNDERCUT GUIDANCE BY SEVERAL DEGREES THROUGHOUT THE EXTENDED DUE TO COLD PATTERN AND SNOW COVER. FOR THU A WEAK SHORTWAVE TROUGH WILL FOLLOW IN THE WAKE OF THE STRONGER TROUGH ON WED. 1000-500 MB THICKNESS AROUND 510 DM AND ENOUGH LOW LEVEL INSTABILITY WILL MAINTAIN SCT FLURRIES. THERE IS A MARGINAL PRESSURE GRADIENT OVER THE AREA THU NT AND BELIEVE DECOUPLING IS PROBABLE SO LOWERED LOW TEMPS INTO THE SINGLE DIGITS FOR MOST LOCATIONS. SWLY WINDS AND WEAK WARM ADVECTION WILL RETURN FOR FRI AND FRI NT AS A WEAK ALBERTA CLIPPER APPROACHES. 1000-500 MB THICKNESSES WILL RETURN TO NEAR 522 DM FOR A SHORT TIME. THE CLIPPER WILL BRING CHANCES OF LGT SNOW FRI NT AND SAT. COLD ADVECTION AND SUBSEQUENT LIGHTER WINDS AND HIGH PRESSURE WILL MAKE FOR SINGLE DIGIT LOWS AGAIN SUN AM. BELOW ZERO TEMPS COULD BE POSSIBLE IF HIGH BUILDS EWD QUICKER. YET ANOTHER SHORTWAVE TROUGH AND ASSOCIATED SFC TROUGH WITHIN NW FLOW APPROACHES FOR SUN NT AND PASSES THROUGH MON AND MON NT. A CHANCE OF LGT SNOW HAS BEEN INTRODUCED FOR THIS PERIOD. && .AVIATION...EXPECTING MVFR CEILINGS TO GRADUALLY DECREASE LATER TONIGHT AS LOW LEVEL RH PROGS SCOUR THINGS OUT. WILL THEN INCREASE MID DECK TOMORROW WITH WARM AIR ADVECTION AHEAD OF NEXT WEATHER SYSTEM. && .MARINE...WILL HAVE SMALL CRAFT ADVISORY REPLACING GALE WARNING. GRADIENT EXPECTED TO RELAX LATER THIS EVENING INFLUENCE OF DEPARTED LOW BEING REPLACED BY A WEAK RIDGE OF HIGH PRESSURE. SMALL CRAFT CONDITIONS WILL RAMP UP AGAIN TOMORROW AS SOUTHWEST WINDS INCREASE AHEAD OF NEXT WEATHER SYSTEM. && .MKX WATCHES/WARNINGS/ADVISORIES... WI...NONE. LM...SMALL CRAFT ADVISORY UNTIL 9 PM CST THIS EVENING FOR LMZ643>646. && $$ SHORT/LONG TERM...20 AVIATION/MARINE...10 |
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