FXUS63 KMQT 261233
AFDMQT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MARQUETTE MI
733 AM EST THU NOV 26 2009
UPDATED FOR 12Z TAFS
.SYNOPSIS...
00Z RAOBS/LATEST WV IMAGERY AND RUC ANALYSIS SHOW TROF CENTERED OVER
THE WRN GRT LKS BTWN RDG OFF THE E COAST AND ANOTHER IN THE ROCKIES.
POTENT SHRTWV/ACCOMPANYING 80KT H5 JET MAX DIGGING INTO THE CENTRAL
MS RIVER VALLEY HAS DEEPENED THE TROF...WITH AN AREA OF RAIN
EXTENDING FM NRN IL INTO ERN WI/WRN LWR MI UNDER VIGOROUS H7-3
QVECTOR CNVGC. IN ABSENCE OF SGNFT FORCING FARTHER N AND DESPITE
DEEP MSTR SHOWN ON THE 00Z GRB RAOB... JUST SOME -RA/-DZ FALLING
OVER MAINLY THE NRN TIER OF THE CWA AT MIDNGT IN UPSLOPE NLY FLOW ON
WRN FLANK OF SFC LO NEAR THE STRAITS OF MACKINAC. 00Z INL SDNG SHOWS
DRYING ABV H85...WHERE THE 00Z TEMP WAS ONLY -7C. ALTHOUGH THERE IS
A LACK OF WDSPRD PCPN IN MN/ADJOINING SCNTRL CAN...WDSPRD SC IS
NOTED THRU MN/ADJOINING ONTARIO. BUT THIS SC IS BREAKING UP CLOSER
TO MUCH DRIER LLVL SHOWN ON THE 00Z YQD RAOB CLOSER TO SFC RDG AXIS
UNDER IMPRESSIVE 12HR H3 HGT RISES UP TO 150M. ANOTHER SHRTWV IS
APRNT DIGGING INTO FAR NW ONTARIO. 00Z H85 TEMP WAS -10C AT YQD.
&&
.DISCUSSION...
MAIN FCST CONCERNS THIS PACKAGE ARE PCPN CHCS/TYPE TDAY...THEN
POTENTIAL FOR LES TNGT INTO FRI.
TDAY...SHRTWV NOW IN THE CNTRL MS RIVER VALLEY IS PROGGED TO LIFT NE
TO LK HURON BY 00Z FRI WHILE SHRTWV NOW IN NW ONTARIO WL DIG SEWD
INTO ERN LK SUP/ERN UPR MI. DEEP LYR QVECTOR CNVGC ASSOCIATED WITH
THE SHRTWV/RA AREA TO THE S IS FCST TO IMPACT THE ERN CWA MAINLY
THIS MRNG. SO MAINTAINED GOING HIER POPS OVER THE E AND IN THE
UPSLOPE AREAS JUST DOWNWIND OF LK SUP FOR OBSVD NLY FLOW. ALTHOUGH
THE SHARPER FORCING WL TEND TO SHIFT TO THE E AFT 18Z...MAINTENANCE
OF DEEPER MSTR/CONTINUED HGT FALLS ON THE CYC SIDE OF REINFORCING
SHRTWV TRACK THIS AFTN ARGUES FOR HOLDING ON TO GOING HIER POPS OVER
THE E AS SUGGESTED BY NAM MOS POPS. MOST OF THIS PCPN WL BE IN THE
FORM OF RA...BUT GFS/NAM FCST WBLB ZERO HGT/H100-85 THKNS FIELDS SUG
THE PCPN WL MIX WITH/CHG TO SN IN THE AFTN BEFORE DIMINISHING. BUT
LIMITED DURATION OF THE SN BEFORE DEEPER MSTR EXITS/RELATIVELY HI
NEAR SFC TEMPS SUG ANY SN ACCUM WL BE MINIMAL. ALTHOUGH THE DIGGING
SHRTWV WL DRAG THE POCKET OF COLDER -10C H85 TEMPS OBSVD NEAR LK
WINNIPEG THIS PAST EVNG INTO THE W HALF OF LK SUP THIS AFTN...AIR
SUFFICIENTLY COLD FOR LES...LARGER SCALE QVECTOR DVGC/HGT RISES ON
THE ACYC SIDE OF SHRTWV TRACK ARE FCST TO STRENGTHEN THE SUBSIDENCE
INVRN BASE NEAR 3K-4K FT AS SHOWN ON FCST SDNGS FOR CMX/IWD. WITH
TEMPS WITHIN THE RELATIVELY SHALLOW MOIST LYR UNDER THE INVRN TOO
WARM FOR DENDRITIC SN GROWTH AS WELL AS ARRIVAL OF DRIER LLVL AIR
DEPICTED ON THE YQD RAOB WL GREATLY LIMIT LES AMOUNTS. ARRIVAL OF
THIS MUCH DRIER LLVL AIR SHOULD RESULT IN DIMINISHING SC LATER IN
THE DAY...ESPECIALLY AWAY FM LK SUP.
ARRIVAL OF THERMAL TROF/H85 TEMPS AS LO AS -10C TNGT WL CONTINUE TO
PROVIDE SUFFICIENT INSTABILITY FOR LES ESPECIALLY IN AREAS E OF MQT
FAVORED BY NNW FLOW DOWNWIND OF PRECONDITIONING FM LK NIPIGON...BUT
STRENGTHING SUBSIDENCE INVRN ARND 4K FT ACCOMPANYING HGT RISES/LARGE
SCALE QVECTOR DVGC AND POOR SN GROWTH WL LIMIT SN ACCUMS PER LES
CHART. THE APRCH OF HI PRES RDG AXIS FM THE W LATE/WEAKENING H925
CNVGC WL FURTHER SUPPRESS LES OVER THE W. THE NAM MOS IS PARTICULARY
CHILLY TNGT...ESPECIALLY OVER THE W WHERE HI PRES RDG WL APRCH LATE.
CONSIDERING SFC DWPTS FALLING TOWARD 15 CLOSE TO THE RDG AXIS
UPSTREAM...THINK THE NAM MOS MIGHT BE ON THE RIGHT TRACK OVER THE
INTERIOR W. FARTHER E...PERSISTENT NNW LLVL FLOW THAT WL MAINTAIN
MORE SC/LK MODERATION FAVORS THE HIER GFS MOS.
SOME LES MAY PERSIST MAINLY IN THE MRNG OVER THE E ON FRI...BUT
ARRIVAL W-E OF HI PRES RDG AXIS WL COMPLETELY END ANY LINGERING PCPN
AND SCOUR OUT SC W OF P53 IN THE AFTN. WITH INVRN BASE SINKING TO 3K
FT AT ERY IN THE AFTN...ANY LINGERING -SHSN/FLURRIES WL BE INSGNFT.
FCST ISENTROPIC ASCENT/MOISTENING ON THE 290-295K SFCS (H8-7) TO THE
E OF LO PRES MOVING THRU THE NRN PLAINS WL RESULT IN SOME AC
SPREADING W-E DURING THE DAY. GOING FCST TEMPS ARE IN GOOD AGREEMENT
WITH MOS FCST AND NEED LTL MODIFICATION.
FRI NGT/SAT...ALTHOUGH THERE WL BE QUITE A BIT OF AC ESPECIALLY OVER
THE NRN CWA ASSOCIATED WITH CONTINUED ISENTROPIC ASCENT E OF WEAK LO
PRES MOVING INTO MN ON FRI NGT AND INTO THE UPR GRT LKS ON SAT...
THE GFS/NAM FCST SDNGS SUG THE LLVLS WL BE TOO DRY FOR ANY PCPN.
WITH LGT WINDS ON FRI NGT...TENDED BLO MOS GUIDANCE FOR LO TEMPS
INLAND FM LK SUP WHERE LESS CLD COVER IS LIKELY. SINCE NCEP PREFERS
THE SOMEWHAT STRONGER LO PRES SHOWN BY THE 00Z ECMWF/CNDN MODELS...
TENDED TO RAISE TEMPS A BIT ON SAT WITH THE ASSUMPTION OF MORE
WARMING AHEAD OF THIS FEATURE.
PER NCEP GUIDANCE...TENDED TOWARD THE 00Z ECMWF/CNDN FOR THE SAT
NGT/SUN FCST DETAILS. THESE MODELS FAVOR A QUICKER/STRONGER COLD
FROPA SAT NGT WITH COLDER AIR ARRIVING FASTER ON SUN. ADJUSTED GOING
POPS TO REFLECT FASTER COLD FROPA AND THEN TO INCRS LES CHCS ON SUN
IN THE NW WIND SN BELTS WITH ECMWF SHOWING H85 TEMPS ARND -10C
ARRIVING OVER LK SUP IN LLVL NW FLOW.
COORDINATED WITH APX.
&&
.AVIATION /FOR THE 12Z TAF ISSUANCE/...
EXPECT IMPROVING CONDITIONS TODAY AS DRIER AIR BEGINS TO WORK INTO
UPPER MICHIGAN BEHIND LOW PRESSURE EXITING TO THE EAST. INITIALLY
THIS IFR VISIBILITIES/CEILINGS COULD OCCUR AT BOTH SITES
WITH ONGOING LES. BY 00Z EXPECT CEILINGS TO LIFT TO VFR AND BY 08Z
AT CMX.
&&
.MARINE /FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE/...
STRONG NORTHERLY WINDS TO 30 KNOTS ARE EXPECTED TODAY ACROSS CENTRAL
AND EASTERN LAKE SUPERIOR TODAY. A FEW GALE FORCE GUSTS TO 35 KNOTS
AREN/T OUT OF THE QUESTION OVER THE CENTRAL AND EAST...THOUGH GUSTS
THIS HIGH SHOULD NOT BE WIDESPREAD. LOOK FOR THE WINDS TO DIMINISH
BELOW 20 KNOTS EARLY FRIDAY MORNING AS LOW PRESSURE LOCATED EAST OF
THE LAKE SHIFTS EAST. WINDS BELOW 20 KNOTS ARE EXPECTED THROUGH
SATURDAY NIGHT AS HIGH PRESSURE INFLUENCES LAKE SUPERIOR. WINDS MAY
INCREASE ABOVE 20 KNOTS OUT OF THE NORTHWEST...BUT REMAIN BELOW GALE
FORCE...SUNDAY INTO MONDAY AS HIGH PRESSURE EDGES CLOSER TO THE
UPPER GREAT LAKES FROM THE WEST. THIS WILL ACT TO INCREASE THE
PRESSURE GRADIENT OVER THE LAKE...THUS INCREASING THE WINDS.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
SYNOPSIS/DISCUSSION...KC
AVIATION...PEARSON
MARINE...PEARSON
