FXUS63 KMQT 260906
AFDMQT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MARQUETTE MI
405 AM EST SAT DEC 26 2009
.SYNOPSIS...
00Z RAOBS/LATEST WV IMAGERY AND RUC ANALYSIS SHOW DEEP CLOSED H5 LO
OVER NW IL BTWN HI AMPLITUDE RDGS ALG THE E AND W COASTS. SFC
OCCLUDED LO CENTER WAS OVER IA AT 03Z. THIS SYS IS SO WRAPPED UP THE
COLDEST POCKET OF AIR IS ON THE SRN FLANK OF THE SFC/H85 LO...WITH
THE WARMEST AIR TO THE N. 00Z H85 TEMP AT DVN WAS -17C...AND THE DVN
RAOB SHOWS NEAR SATURATION SFC-H4. SFC OCCLUDED/COLD FNT ON THE
LEADING EDGE OF THIS AIRMASS IS MOVING NWD THRU WI...PASSING MNM AT
04Z AS NOTED BY SHARP WSHFT FM ESE TO S. GENERALLY LGT SN CONTINUES
OVER THE MUCH OF THE FA IN ADVANCE OF THIS FNT...SUPPORTED BY LARGER
SCALE CYC FLOW ARND OCCLUDED LO/UPR DVGC ASSOCIATED WITH APRCH OF
85KT H3 JET MAX/H85-7 FGEN ACCOMPANYING THE APRCH OF THE COLD/
OCCLUDED FNT/DEEP MSTR SFC-H45 ALSO SHOWN ON THE 00Z GRB RAOB. HIER
SFC TEMPS ARND 36 NEAR THE LKSHORE SUG THE PCPN MAY BE MIXED WITH RA
THERE. DUE TO THE MOIST NATURE OF THE AIRMASS OBSVD AT DVN/GRB AND
ESE-WNW TRACK OF SHRTWV THRU SRN WI ROTATING ARND CUTOFF LO
CENTER...SHSN ARE NOTED OVER MUCH OF WI BEHIND THE COLD/OCCLUDED
FNT...LESS OVER THE SE.
&&
.DISCUSSION...
FCST CONCERNS THIS PACKAGE INCLUDE PCPN TRENDS/SN AMNTS WITH TREND
TOWARD MORE LK EFFECT SN WITH ARRIVAL OF COLDER AIR NOW TO THE S.
TDAY...APRCHG COLD/OCCLUDED FNT WL CLEAR THE NRN CWA BY NOON AS
DECAYING OCCLUDED LO TO THE SW DRIFTS SLOWLY ENE TO NRN IL BY 00Z.
ALTHOUGH SHSN ARE FALLING OVER MUCH OF THE NW 2/3 OF WI NOW...GFS/
NAM SHOW DNVA/SUBSIDENCE IN THE WAKE OF SHRTWV NOW MOVING WNWD THRU
SRN WI WL RESULT IN DRYING OF THE ATMOSPHERE...AS OBSVD NOW IN SE
WI. SO TENDED TO CUT POPS IN THE WAKE OF FROPA WITH LLVL FLOW
INITIALLY DIFFLUENT AS WELL. BUT ARRIVAL OF COLDER AIR FM THE S WITH
H85 TEMPS PROGGED TO FALL TO -12C AFT 18Z WL RESULT IN SOME LES OFF
THE RELATIVELY WARM WATERS OF GREEN BAY/ LK MI IN THE AFTN...
ESPECIALLY WITH ARRIVAL OF DEEPER MSTR FM THE AREA OF THE 00Z DVN
RAOB AS SHOWN LATER IN THE DAY BY GFS/NAM. HOWEVER...THE SETUP DOES
NOT LOOK AS IMPRESSIVE AS ON PREVIOUS RUNS WITH WEAKER H925 SE FLOW.
BUT STILL MAINTAINED LIKELY POPS OVER THE SCNTRL LATER IN THE DAY
WHERE 00Z GFS/NAM/CNDN/LOCAL WRF-ARW SHOW HINT OF LO PRES TROF. NAM
FCST SDNG FOR ESC EVEN SHOWS LLVL CYC FLOW/CNVGC FORCING SOME DECENT
UVV WITHIN DGZ THERE ARND 00Z...SO EXPECT HI SN/WATER RATIOS THERE
AND AT LEAST A COUPLE INCHES ACCUMULATION. ELSEWHERE...THE WEAKNESS
OF THE LLVL FLOW JUSTIFIES NO MORE THAN CHC POPS WITH LARGER SCALE
QVECTOR DVGC DOMINATING. CONSIDERING THE CHILL OF THE AIRMASS TO THE
S...TENDED TOWARD THE LO END OF GUIDANCE FOR TEMPS.
TNGT...STEADILY DECAYING OCCLUDED LO IS PROGGED TO DRIFT NE INTO
NCNTRL LK BY 12Z SUN...WITH LLVL FLOW PROGGED TO GRDLY TURN MORE NE
THRU THE NGT. EXPECT THE HIEST POPS OVER THE SE ZNS CLOSER TO LARGE
SCALE QVECTOR CNVGC/DEEPER MSTR/H7 UVV/SHARPER LLVL CYC FLOW SHOWN
BY THE 00Z GFS. WITH HI SN/WATER RATIOS GIVEN GFS FCST FOR ESC
SHOWING UVV WITHIN THE DGZ AND POTENTIAL FOR SOME LK ENHANCEMENT
WHILE THE H925 FLOW IS MORE ELY...A MARGINAL ADVY MAY BE NECESSARY
OVER THE SCNTRL FOR LATE TDAY/TNGT ON CYC SIDE OF H7 LO TRACK...
ALBEIT WEAKENING OCCLUSION. WSHFT TO THE NNE FARTHER TO THE NW WL
MAINTAIN LES CHCS NEAR LK SUP...BUT MORE ACYC LOOK AND RATHER LGT
NATURE OF SFC-H925 FLOW W OF THE HURON MTNS SUGS ANY SN THERE WL BE
ON THE LGT SIDE WITH H85 TEMPS ONLY -10C.
AS THE WEAKENING OCCLUSION SHIFTS TO THE NE ON SUN...LLVL FLOW WL
BACK TO THE NW. BUT SINCE SO MUCH WARM AIR HAS INVADED SRN CAN ON
THE NRN FLANK OF THE OCCLUSION...H85 TEMPS ARE ACTUALLY PROGGED TO
RISE THRU THE DAY FM -10C OVER WRN LK SUP AT 12Z SUN TO -8C AT 00Z
MON...MARGINAL TEMPS FOR PURE LES. GFS/NAM DIFFER IN THAT GFS SHOWS
WAD/MSTR ADVECTION OVERWHELMING DNVA/HGT RISES TO RESULT IN QVECTOR
CNVGC WHILE NAM HINTS AT MORE QVECTOR DVGC WITH DNVA/HGT RISES
DOMINATING. SINCE BOTH MODELS AS WELL AS UKMET SHOW SFC TROF PASSING
IN THE AFTN AND WARM AIRMASS TO THE NW IS ALSO MOIST...OPTED TO
MAINTAIN GOING LIKELY POPS OVER THE W IN THE AFTN DESPITE LACK OF
MORE THAN MARGINAL INSTABILITY. WITH THE GRADUAL RETURN OF WARMER
AIR FM THE NW...TEMPS ON SUN SHOULD RUN ABV NORMAL DESPITE PLENTY OF
CLDS.
A REINFORCING SHRTWV IN THE NW FLOW ALF IS PROGGED TO DIG INTO THE
UPR GRT LKS ON SUN NGT...WITH ACCOMPANYING COLD FNT SWEEPING THRU
THE KEWEENAW LATE SUN NGT AND THEN CLRG THE SCNTRL COUNTIES ON MON
MRNG. MAINTAINED GOING LIKELY POPS NEAR LK SUP ON SUN NGT...WITH
POPS DIMINISHING TO SCHC OVER THE SCNTRL WITH DOWNSLOPE FLOW.
ARRIVAL OF H85 TEMPS IN THE -15C TO -20C RANGE ON MON WARRANTS
LIKELY POPS IN THE NNW WIND SN BELTS ESPECIALLY OVER THE E CLOSER TO
TRACK OF SHRTWV/CORE OF INCOMING COLDEST AIR. DRYNESS OF ARRIVING
AIRMASS WL LIKELY LIMIT SN AMNTS DESPITE IMPROVING OVERWATER
INSTABILITY. WITH INVRN BASE FCST TO FALL AOB 3K FT MON AFTN OVER
THE W...TENDED TO CUT POPS THERE IN THE AFTN. TEMPS ON SUN NGT WL
RUN ABV NORMAL...BUT TEMPS ON MON WL SHOW ONLY A MINOR DIURNAL
REBOUND WITH VIGOROUS CAD. A GUSTY NNW WIND WITH H925 WINDS UP TO
30-35KTS WITHIN THE THERMAL TROF WL MAKE THE DAY FEEL EVEN COLDER.
&&
.AVIATION.../FOR THE 06Z TAF ISSUANCE/...
KCMX...EXPECT LIFR CIGS TO IMPROVE TO IFR BY 10Z TONIGHT AND THEN
IMPROVE TO MVFR BY 13Z SATURDAY AS THE PASSAGE OF AN OCCLUDED FRONT
SHIFTS WINDS FROM UPSLOPE EAST TO DOWNSLOPE S-SE DIRECTION. MVFR
VSBYS IN SNOW SHOULD ALSO IMPROVE TO VFR WITH THE PASSAGE OF THE
OCCLUDED FRONT AS S-SE WINDS WILL NO LONGER SUPPORT ANY LAKE
ENHANCED SNOW.
AT KSAW...A MOIST ESE FLOW WILL CONTINUE TO SUPPORT IFR CIGS AND
MVFR VSBYS IN LIGHT SNOW INTO THE EARLY OVERNIGHT. PASSAGE OF THE
OCCLUDED FRONT WILL ALLOW CONDITIONS TO IMPROVE TO MVFR BY 10Z
TONIGHT AS DRIER AIR WORKS IN FROM THE SOUTH. CYCLONIC S-SE FLOW
WILL CONTINUE TO SUPPORT SOME LIGHT SNOW/FLURRIES ON SATURDAY AS
CIGS REMAIN IN THE MVFR RANGE.
&&
.MARINE.../FOR THE 4 AM LAKE SUPERIOR ISSUANCE/...
SURFACE LOW OVER IA WILL CONTINUE TO WEAKEN AS IT LIFTS SLOWLY
NORTHEASTWARD TOWARDS NORTHERN LOWER MI BY SUNDAY AFTERNOON. AS
OCCLUDED FRONT LIFTS NORTHWARD INTO LAKE SUPERIOR EARLY THIS MORNING
AND PRESSURE GRADIENT RELAXES SIGNIFICANTLY WINDS WILL DIMINISH.
WITH GALES DIMINISHING A BIT EARLIER ACROSS THE EASTERN LAKE WILL
CANCEL GALE WARNING. HOWEVER...A FEW WIND GUST TO 30KTS WILL STILL
BE POSSIBLE EARLY THIS MORNING. GLANCING BLOW FROM S/WV AND SURGE OF
COLDER AIR OVER LAKE SUPERIOR ON MONDAY WILL RESULT IN ANOTHER ROUND
OF GALES...THIS TIME FROM THE NORTH WITH WINDS TO 40 KTS POSSIBLE.
WINDS WILL DIMINISH BELOW 20 KTS FOR TUESDAY AND WEDNESDAY.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...NONE.
LAKE SUPERIOR...NONE.
LAKE MICHIGAN...NONE.
&&
$$
SYNOPSIS/DISCUSSION...KC
AVIATION...VOSS
MARINE...MZ
