FXUS63 KMQT 300909
AFDMQT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MARQUETTE MI
409 AM EST MON NOV 30 2009
.DISCUSSION...
RADAR CURRENTLY SHOWS SOME FAIRLY HEAVY LAKE EFFECT PCPN OVER
EASTERN LAKE SUPERIOR INTO AREAS EAST OF MUNISING.
FORTUNATELY...THIS PCPN IS MOVING EAST AS THE WINDS SLOWLY SHIFT
TO THE NW AND THEN W-NW LATER THIS MORNING. THIS BAND JUST FORMED
OVER THE PAST FEW HOURS AND WAS LIKELY CAUSED BY SOME ENHANCED LOW
LEVEL CONVERGENCE AS THE WEAK SFC TROUGH OVER ONTARIO MOVED INTO THE
EASTERN LAKE. WILL GO WITH OCNL SNOW SHOWERS ACROSS THE EAST THIS
MORNING WITH LOCAL 1-2 INCHES ACCUMULATIONS TO ACCT FOR THIS
ACTIVITY. HI RES RAPID REFRESH SUGGESTS THAT THIS ACTIVITY WILL
QUICKLY MOVE OFFSHORE THIS MORNING...ALTHOUGH BEFORE THAT OCCURS
SOME PCPN WILL BE RATHER INTENSE WHERE IT DOES OCCUR.
OTHERWISE...ANY LAKE EFFECT PCPN ACROSS THE WEST SHOULD END RATHER
QUICKLY EARLY THIS MORNING AS WINDS CONTINUE TO SHIFT TO THE W-SW
AND DRIER AIR AHEAD OF THE CLIPPER SYSTEM MOVES IN.
AS FOR THE CLIPPER SYSTEM TODAY...THE MODELS ARE IN FAIRLY GOOD
AGREEMENT IN SHOWING SOME MODEST F-GEN FORCING TO MOVE ACROSS THE
AREA LATE THIS AFTERNOON INTO THIS EVENING. IN FACT...THE H7 F-GEN
WILL LIKELY BE STRENGTHENING A LITTLE AS IT MOVES INTO WESTERN UPPER
DUE TO INCREASED DEFORMATION AHEAD OF THE TROUGH AXIS. STABILITY
VALUES SOMEWHAT LOW AS WELL. THIS SHOULD BE A TYPICAL QUICK MOVING
CLIPPER SYSTEM...HOWEVER THE NAM AND GFS BOTH SHOW 0.1 TO 0.2 INCH
OF QPF OVER THE WESTERN HALF OF THE CWFA AS THE SYSTEM MOVES THROUGH
LATE THIS AFTN INTO THIS EVENING. A 1 TO 3 INCH SWATH OF SYNOPTIC
TYPE SNOW ACROSS AREAS WEST OF A MQT TO ESC LINE DOES NOT SEEM OUT
OF THE QUESTION LATE THIS AFTERNOON INTO TONIGHT AS H7 SPECIFIC
HUMIDITY VALUES BTWN 18Z AND 06Z WILL BE IN THE 1-2 G/KM RANGE
ACROSS THE WEST HALF. ALTHOUGH IT WILL BE SHORT LIVED THERE THERE
DENDRITIC SNOW GROWTH WILL BE FAVORABLE WITH THE ACTIVE F-GEN REGION
IN THE DGZ SO SOME 15-20:1 SNOW RATIOS NOT OUT OF THE QUESTION.
WITH 850MB TEMPS AROUND -8C TONIGHT THERE MAY BE SOME LAKE EFFECT
TYPE SNOW IN THE NW FAVORED SNOWBELTS...BUT THE NAM AND GFS SHOW
SOME DRY AIR MOVING IN LATER TONIGHT INTO TUESDAY AHEAD OF THE NEXT
SYSTEM ON TUESDAY/TUE NIGHT. BETTER CHANCE FOR LES WILL BE ACROSS
THE EAST WHERE PBL FLOW WILL BE A LITTLE MORE CONVERGENT AND THERE
IS A HINT OF A LAKE INDUCED TROUGH. WILL KEEP LIKELY POPS FOR THE
ENTIRE NIGHT ACROSS THE EAST WITH 1-3 INCHES ACCUMULATION IN THAT
REGION AS WELL.
MODELS REALLY START TO DIVERGE TUESDAY AS THE NAM AND GFS HANDLE THE
ENERGY CURRENTLY ENTERING THE PAC NW QUITE DIFFERENTLY. THE 00Z NAM
DIFFERS SIGNIFICANTLY FROM PREV RUNS AND THE OTHER MODELS IN BEING
SLOWER WITH THE ENERGY...AND THEREFORE CAUSING THE NEXT SYSTEM TO BE
FURTHER SOUTH. MEANWHILE...THE GFS AND ECMWF ARE IN GENERAL
AGREEMENT TAKING THE LOW FROM NRN MN TO WESTERN UPPER MI BY TUESDAY
NIGHT...THEN INTO QUEBEC BY WEDNESDAY EVENING. THE NAM IS DISCOUNTED
WITH THIS SYSTEM AS IT THE OUTLIER NOT ONLY WITH THE OPERATIONAL
MODELS BUT IT/S ALSO THE WESTERN/SOUTHERN OUTLIER WITH THE SREF
MEMBERS. WITH THIS IN MIND...THE CURRENT FCST IS ON TRACK WITH THE
HEAVIEST PCPN LATER TUE INTO TUESDAY NIGHT ACROSS LAKE SUPERIOR. IN
FACT...THE GFS WOULD IMPLY THAT OTHER THAN SOME POSSIBLE LIGHT SNOW
IN THE WARM ADVECTION NR THE WARM FRONT TUE MORNING...IT WILL BE DRY
ACROSS THE AREA UNTIL THE WINDS TURN NW LATER TUESDAY NIGHT. WILL
THEREFORE GO WITH CHC POPS ACROSS THE ENTIRE REGION TUE AFTN/TUE
NIGHT WITH THE HIGHEST POPS NORTH. WILL ATTEMPT TO BRING IN A DRY
SLOT LATER TUE AFTN INTO TUE EVENING PER THE GFS AND LOWER POPS
ESPECIALLY SOUTH. AGAIN...IT WOULD NOT BE TERRIBLY SURPRISING IF IT
IS COMPLETELY DRY TUE AFTN/TUE EVENING ESPECIALLY IF THE GFS
VERIFIES. IN ADDITION...WITH THE WARM ADVECTION THERE SHOULD BE AT A
MINIMUM A RAIN/SNOW MIX WITH ANY PCPN TUE AFTN/NIGHT.
NO MAJOR CHANGES TO THE REMAINDER OF THE FCST. THE NAM IS DISCOUNTED
WITH THE TRACK OF THE GULF LOW WED/WED NIGHT AS IT IS CONSIDERABLY
FURTHER WEST /INTO LOWER MI BY WED NIGHT/ COMPARED TO THE OTHER
MODELS. THE GFS/ECMWF/GEM SUGGEST A TRACK UP THE SPINE OF THE
APPALACHIANS. THIS IS STILL FURTHER WEST THAN YESTERDAY AND BOTH THE
EC AND ECMWF SHOW PBL WINDS A LITTLE MORE NORTHERLY. LES IS STILL
LIKELY WED NIGHT INTO THU AND SIGNIFICANT ACCUMULATIONS NOT OUT OF
THE QUESTION GIVEN THE COLD AIRMASS AND PERSISTENT FLOW OFF THE
LAKE. HOWEVER...STILL UNCERTAIN EXACTLY WHERE THE HEAVIEST SNOW WILL
OCCUR WITH UNCERTAINTY OF THE LOW LVL WIND FLOW. WILL CONTINUE
MENTION OF POSSIBLE HVY SNOW IN HWO.
&&
.AVIATION /FOR THE 06Z TAF ISSUANCE/...
AT CMX...LAKE EFFECT MOISTURE SHOULD CONTINUE AS WINDS STAY FROM THE
WEST AND THIS WILL HELP KEEP A MVFR CIG AT THIS SITE THROUGH THIS
FORECAST. LITTLE CLIPPER TYPE SYSTEM WILL BRING SOME MVFR VIS SNOW
TO CMX MON EVENING. AT SAW...VFR CONDITIONS WILL CONTINUE UNTIL
CLIPPER TYPE SYSTEM CLOUDS AND SNOW ARRIVE IN THE AFTERNOON OR EARLY
EVENING.
&&
.MARINE /FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE/...
A TROUGH WILL MOVE SOUTHEASTWARD ACROSS LAKE SUPERIOR TODAY CAUSING
WINDS TO START TO VEER NORTHWEST. AS A WEAK RIDGE OF HIGH PRESSURE
MOVE ACROSS LAKE SUPERIOR ON TUESDAY FOLLOWED BY THE LOW PRESSURE
FROM THE CANADIAN PRAIRIES TUESDAY EVENING...WINDS WILL DIMINISH AND
BACK SOUTH. WHEN THE LOW MOVES INTO QUEBEC LATE TUESDAY NIGHT AND
WEDNESDAY...THERE IS THE POTENTIAL FOR WESTERN GALES TO 35 KNOTS
ACROSS EASTERN LAKE SUPERIOR. OTHERWISE...FOR WEDNESDAY AND
THURSDAY...A STRONGER LOW IS EXPECTED TO MOVE FROM THE MISSISSIPPI
DELTA REGION TO THE NEW ENGLAND STATES. THIS WILL KEEP AN ELONGATED
AREA OF HIGH PRESSURE...AND NORTHERLY WINDS...STUCK ACROSS THE
PLAINS STATES THROUGH FRIDAY.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
DISCUSSION...MRD
AVIATION...07
MARINE...DLG
