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000 FXUS63 KMQT 251138 AFDMQT AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MARQUETTE MI 638 AM EST WED NOV 25 2009 .SYNOPSIS... 00Z RAOBS/LATEST WV IMAGERY AND RUC ANALYSIS SHOW DEEPENING UPR TROF OVER CENTRAL NAMERICA. SEVERAL WELL DEFINED BUT DISJOINT SHRTWVS ARE EMBEDDED WITHIN THIS FLOW. THE FIRST IS MOVING INTO NW IL. DESPITE MARGINAL MSTR RETURN TO THE N AT H85-7 IN ADVANCE OF SFC LO SHIFTING INTO SRN WI (00Z PWAT ONLY 0.55-0.60 INCH AT GRB/DVN)...88D COMPOSITE SHOWS A WDSPRD AREA OF RA EXTENDING FM SE WI/SW LWR MI NWD INTO THE SCNTRL COUNTIES IN AREA OF SHARP DPVA/DEEP LYR H85-3 QVECTOR CNVGC AND VIGOROUS UPR DVGC IN LEFT EXIT OF SUPPORTING 100KT/80KT H3/H5 JET MAX. ANOTHER WEAKER SHRTWV IS NOTED OVER NW ONTARIO AND DRAGGING A WEAK COLD FNT THRU THE MN ARROWHEAD/FAR WRN LK SUP. SCT -SHRA ARE EVIDENT ALG THIS BNDRY. A NARROW HI PRES RDG AXIS/SWATH OF DRIER AIR SEPARATES THIS FNT FM THE LAST OF THE SHRTWVS DIGGING INTO THE NRN PLAINS. DESPITE VIGOROUS DPVA/DEEP LYR H7-3 QVECTOR CNVGC AHEAD OF THIS SHRTWV/SUPPORTING 120KT H3 JET MAX...LIMITED MSTR AS INDICATED BY 00Z PWAT OF 0.25 INCH AT ABR/0.39 INCH AT BIS IS LIMITING PCPN TO JUST SOME SCT -SHRA. THE SHRTWV APPEARANCE IS VIGOROUS ON WV IMAGERY...BUT COLD AIR INFUSION BEHIND THE ATTENDANT COLD FNT IS RELATIVELY WEAK WITH 00Z H85 TEMP ONLY -7C AT THE PAS NEAR LK WINNIPEG. COLDER AIR WITH 00Z H85 TEMP OF -11C IS NOTED AT CHURCHILL MANITOBA. && .DISCUSSION... MAIN FCST CONCERNS THIS PACKAGE REVOLVE ARND PCPN CHCS/TYPE/PSBL SN AMOUNTS ASSOCIATED WITH THREE SHRTWVS NOTED ABV. LATEST NUMERICAL GUIDANCE IS FAIRLY CONSISTENT SHOWING THESE DISPARATE SHRTWVS WL REMAIN UNPHASED...AVOIDING A POTENTIAL WINTER STORM/SGNFT PCPN EPISODE THIS THANKSGIVING HOLIDAY. TDAY...SHRTWV NOW BRINGING PCPN APRCHG THE SCNTRL IS PROGGED TO MOVE STEADILY NEWD THRU NRN LWR MI INTO LK HURON BY 00Z THU...WITH SFC LO MOVING TO NEAR THE STRAITS OF MACKINAC. SHARPEST DPVA/H85-3 QVECTOR CNVGC/LEFT EXIT UPR DVGC IS PROGGED TO IMPACT THE CNTRL/ERN CWA THIS MRNG. USED THE GFS FCST SHARPEST H8-7 FGEN AT 18Z FM ABOUT THE HURON MOUNTAINS TO CRYSTAL FALLS TO MARK THE WRN EDGE OF HIER CATEGORICAL POPS. MEANWHILE...DVLPG CYC FLOW ARND THE SFC/H85 LO IS FCST TO OVERWHELM WEAKER FNT/LO PRES TROF PUSHING INTO WRN LK SUP...WITH WEAKENING H85-8 FGEN AS THE REMNANTS OF THE FNT/TROF PUSH TOWARD THE WRN CWA. ALTHOUGH THIS FCST WOULD SUG A LOWER POP...RECENT RADAR TRENDS SHOWING AN EXPANSION OF ECHO OVER WRN LK SUP SUG MAINTAINING A LIKELY POP OVER THE W. MAINTAINED GOING TREND OF DIMINISHING POPS THIS AFTN OVER THE E WITH EXIT OF SHARPER DYNAMICS TO THE N. ALTHOUGH LINGERING WEAKLY CYC FLOW/MSTR ARGUES FOR HOLDING ON TO POPS IN THE AFTN FOLLOWING DEPARTURE OF SHARPER DYNAMICS...OPTED TO CUT POPS TO HI CHC WITH FA IN VOID BTWN DEPARTING SHRTWV/SHRTWV TO THE W DIGGIN SEWD TO THE SW OF FA. EXPECT LTL DIURNAL INCRS IN TEMP WITH WDSPRD CLD COVER/PCPN. TNGT...SHRTWV NOW IN THE NRN PLAINS IS FCST TO DIG SHARPLY TO THE SE AND OVER INDIANA BY 12Z THU. WITH TRACK OF SHRTWV/DPVA/SHARPEST H7-3 QVECTOR CNVGC SO FAR TO THE S AND DOWNSLOPING NLY FLOW OVER THE SCNTRL...OPTED TO CUT GOING LIKELY POPS THERE TO HI CHC PER GFS/NAM MOS POPS. RETAINED LIKELY POPS IN THE AREAS OF THE NCNTRL AND W WHERE NLY FLOW UPSLOPES AND NAM/GFS SHOW SHARP H925 CNVGC AND OVER THE E AFT 06Z WHEN SHARPER QVECTOR CNVGC ON NRN FLANK OF BETTER FORCING TO THE S INVIGORATES DEEPER MSTR THERE. WITH ARRIVAL OF COLDER AIR SHOWN BY NAM/GFS FCST H100-85 THKNS/WBLB ZERO HGT FIELDS...MIXED SHRA WITH SHSN OR CHANGED TO ALL SHSN OVER THE W HALF. ANY PCPN WL REMAIN ALL RA OVER THE E HALF. FCST H85 TEMPS OVER WRN LK SUP AT 12Z THU ARE FCST BY NAM/GFS TO BE ONLY ABOUT -7C...CONSISTENT WITH 00Z OB FM THE PAS...MARGINAL FOR PURE LES CONSIDERING WATER TEMPS OVER THE WRN LK IN THE 6-7C RANGE IN ABSENCE OF DYNAMIC SUPPORT. SINCE FCST SDNGS ALSO SHOW MOIST LYR BLO THE HGT FOR OPTIMAL SN GROWTH BY 12Z THU WHEN THE COLDEST AIR DOES ARRIVE AT H85...THINK ANY SN ACCUM WL BE ON THE LGT SIDE. ALTHOUGH MODELS HAVE TRENDED TO BE A BIT MORE PROGRESSIVE WITH LO PRES DEPARTING TO THE E...POTENTIAL FOR ANOTHER SHRTWV TO DIG INTO AND SHARPEN THE UPR TROF/DEEPEN SFC LO JUST TO THE E ARGUES FOR THE SOMEWHAT SLOWER GFS/UKMET OVER THE MORE PROGRESSIVE NAM/CNDN. THE 12Z ECMWF WAS EVEN SLOWER THAN THE 00Z GFS/UKMET TO MOVE THIS DEEPER MSTR TO THE E...LENDING SUPPORT FOR THE SLOWER SCENARIO. THE SLOWER MODELS WOULD SUPPORT LINGERING LIKELY POPS OVER THE E THRU THE DAY ON CYC SIDE OF TRACK OF REINFORCING SHRTWV. BY THE TIME ENUF COLD AIR GETS INTO THE E LATER IN THE DAY WHERE DEEPER MSTR WL LINGER LONGEST...EXPECT PCPN TO BE DIMINISHING. TO THE W...ARRIVAL OF COLDER AIR (H85 TEMPS FALLING TOWARD -10C) WL MAINTAIN HI CHC/LIKELY POPS FOR LES...BUT SUBSIDING INVRN BASE TO ARND 4K FT IN THE AFTN WITH RISING HGTS ON THE ACYC SIDE OF REINFORCING SHRTWV WL LIMIT SN INTENSITY. CONTINUED LES IN THE SN BELTS MAINLY FAVORED BY NW FLOW...BUT TRENDED LOWER ON POPS LATER AT NGT OVER THE W WITH ARPCH OF RDG AXIS/ACYC FLOW. WENT WITH LOWEST TEMPS ON THU NGT OVER THE INTERIOR W AND SCNTRL WHERE HI PRES RDG WL ARRIVE TOWARD 12Z AND FLOW WL BE LESS MODIFIED BY LK SUP. MODELS CONTINUE TO HAVE DIFFICULTY HANDLING W-E PROGRESSION OF FLOW ON FRI INTO THE WEEKEND. THE 00Z CNDN HAS BEEN MOST CONSISTENT WITH PREVIOUS RUNS SHOWING A MORE PROGRESSIVE FLOW...00Z ECWMF HAS NOW TRENDED IN THIS DIRECTION AS WELL. SINCE THIS MORE PROGRESSIVE TREND APPEARS AT ODDS WITH FCST RAPID DEVELOPMENT OF SFC LO OFF THE NEW ENGLAND COAST/MORE AMPLIFIED UPR FLOW...USED A BLEND OF THE MORE PROGESSIVE MODELS WITH THE SOMEWHAT SLOWER GFS FOR GUIDANCE. MADE A FEW MINOR CHGS TO GOING FCST...BUT FEW SGNFT CHGS WITH CONSIDERABLE MODEL UNCERTAINTY. && .AVIATION /FOR THE 12Z TAF ISSUANCE/... BROAD AREA OF MOISTURE/PRECIPITATION WILL IMPACT BOTH SITES THIS MORNING AND AFTERNOON AS A LOW PRESSURE SYSTEM SHIFTS SOUTHEAST OF UPPER MICHIGAN TODAY AND TOMORROW. NORTHERLY MOIST FLOW ASSOCIATED WITH THIS SYSTEM WILL ALLOW FOR LIFR/IFR CONDITIONS THROUGHOUT THIS TAF PERIOD WITH MARGINAL IMPROVEMENT EXPECTED LATE TONIGHT. && .MARINE /FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE/... LIGHT SOUTHEAST TO EAST WINDS THIS MORNING OVER THE LAKE WILL GIVE WAY TO STRONG NORTHERLY WINDS THIS EVENING AS A LOW PRESSURE SYSTEM PASSES TO THE SOUTHEAST OF UPPER MICHIGAN TODAY. EXPECT WINDS TO INCREASE TO 30 KNOTS THIS EVENING BEFORE DIMINISHING LATE THURSDAY NIGHT. NOT ANTICIPATING GALE FORCE WINDS AS THE AIR ABOVE THE LAKE SURFACE IS NOT COLD ENOUGH TO MIX DOWN STRONGER WINDS ALOFT. ON SATURDAY AND SUNDAY A HIGH PRESSURE RIDGE WILL BUILD ACROSS THE LAKE ALLOWING WINDS TO DIMINISH ON SATURDAY AFTERNOON BELOW 20 KNOTS. NORTHEAST WINDS OF 20 TO 25 KNOTS ARE POSSIBLE ON SUNDAY AS A LOW PRESSURE SYSTEM MOVES OUT OF THE MID MISSISSIPPI VALLEY AND TRACKS ACROSS LOWER MICHIGAN. && .MQT WATCHES/WARNINGS/ADVISORIES...NONE. && $$ SYNOPSIS/DISCUSSION...KC AVIATION/MARINE...PEARSON
