FXUS61 KCTP 301603
AFDCTP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
1103 AM EST MON NOV 30 2009
.SYNOPSIS...
A COLD FRONT WILL PUSH EAST OUT OF PA TODAY. LAKE EFFECT SNOW
SHOWERS HAVE ALREADY BEGUN AND WILL CONTINUE INTO TUESDAY MORNING.
AN AREA OF HIGH PRESSURE BUILDS INTO THE REGION TUESDAY THROUGH
WEDNESDAY. AN ACTIVE WEATHER PATTERN RETURNS FOR THE SECOND HALF
OF THE WEEK WITH AN AREA OF LOW PRESSURE MOVING UP INTO THE OHIO
VALLEY LATE WEDNESDAY INTO THURSDAY. ADDITIONAL RAIN IS EXPECTED
FOR THURSDAY AND MAY POSSIBLY BECOME MIXED WITH SNOW SHOWERS WITH
COOLER TEMPERATURES FOR THE UPCOMING WEEKEND.
&&
.NEAR TERM /UNTIL 8 PM THIS EVENING/...
PRECIP ALREADY TAPERING OFF WITH JUST VERY LIGHT RAIN IN THE SE
AND DOWNSLOPE DRYING OCCURRING IN THE CENTRAL MTS. RAIN HAS TURNED
TO SNOW OVER THE RIDGES OF THE LAURELS AND LAKE EFFECT ON NW FLOW
PUSHING SHORT STREAMERS INTO WARREN AND MCKEAN COS. FLURRIES
EXTEND A LITTLE FARTHER INTO THE ALLEGHENIES. ANY RAIN IN THE SE
WILL DIMINISH VERY QUICKLY EARLY THIS AFTN...AS FRONT IS THRU ALL
BUT LNS. THUS...DOWNSLOPE IS STARTING THERE...TOO. WILL KEEP ANY
MENTIONS OF ACCUMS TO ONLY THE LAURELS AND THE FAR NW. BUT THESE
SHOULD BE AN INCH OR LESS WITH THE LESS-THAN-FAVORABLE WIND DIR
AND GRADUAL BACKING IN LLVLS.
&&
.SHORT TERM /8 PM THIS EVENING THROUGH 6 AM TUESDAY/...
THE QUESTION FOR TONIGHT IS IF TOO MUCH DRY AIR WILL ENTRAIN INTO
THE BNDRY LYR AND CHOKE OFF LES FROM DEVELOPING UNTIL AFT 06Z.
500MB TROUGH AXIS QUICKLY PIVOTS THRU THE REGION UNDER A
PROGRESSIVE FLOW...WITH A WEAK LOBE OF VORTICITY ACROSS SOUTHERN
ONTARIO OVERNIGHT. BASED ON MESOSCALE SOUNDINGS THE DENDRITIC
GROWTH ZONE REMAINS ELEVATED WITH TOO MUCH DRY IN THE 5-8KFT RANGE
ACROSS OUR FAVORED LES CWFA TO SUPPORT ANY ORGANIZED BANDS OR
PROLONGED INTENSITY OF SN. WEAK UPSLOPE MECHANISM COULD SPAWN SOME
SCT SHSN BTWN 06-12Z FOR MUCH OF THE ALLEGHENY MTNS WITH ARND AN
INCH OF TWO PSBL. HAVE ADJUSTED POPS TO REFLECT THE TYPICAL
UPSLOPE AND LES REGION OF OUR CWFA...TO HIGH CHC. DOWNSTREAM
EXPECT DRY CONDS OVERNIGHT FOR THE SUSQ-VALLEY. CLOUD SHIELD WILL
CONTINUE TO THIN ACROSS THE SUSQ- VALLEY WITH PROLONGED
SUBSIDENCE...WITH OVERNIGHT TEMPS IN THE LOW TO MID 30S. UPSTREAM
TEMPS WILL BE COOLER IN THE MID 20S NW TO LOW 30S CENTRAL.
&&
.LONG TERM /TUESDAY THROUGH SUNDAY/...
VERY CHANGEABLE CONDITIONS FOR THE EXTENDED WILL TRANSITION TO
NEAR TO BELOW NORMAL TEMPERATURES BY LATE IN THE PERIOD...AS COLD
AIR ENVELOPS MUCH OF THE LOWER 48 BY NEXT WEEKEND.
ENSEMBLES AND DETERMINISTIC RUNS INDICATE A RAPID REGIME CHANGE
FROM BRIEF LAKE EFFECT ON TUESDAY TO STRONG OVERRUNNING WARM
ADVECTION LATER WEDNESDAY INTO THURSDAY AS SOUTHWEST UNITED STATES
CUTOFF PHASES WITH STRONG NORTHERN STREAM UPPER TROF WHICH DROPS
THROUGH THE NORTHERN ROCKIES INTO THE NORTHERN AND CENTRAL PLAINS
LATE TUESDAY AND WEDNESDAY. GEFS CONSENSUS SFC LOW TRACK TRENDING
FURTHER WESTWARD OVER THE LAST 24 HOURS WITH WARMER AIR FLOODING
NORTHWARD ALONG THE MID ATLANTIC SEABOARD AND NORTHWARD INTO
CENTRAL PA...WITH NO CAD TO SPEAK OF GIVEN SFC HIGH TRACKING WELL
OFF THE COASTLINE ON WEDNESDAY. THUS...CONFIDENCE APPEARS TO BE
INCREASING FOR A RAIN STORM THROUGHOUT CENTRAL PA WEDNESDAY
AFTERNOON INTO EARLY THURSDAY AS A FAIRLY DEEP SFC CYCLONE RIDES
NEWD ALONG THE SPINE OF THE APPALACHIANS...REACHING NORTHERN NEW
ENGLAND THURSDAY EVENING.
IT APPEARS SEASONABLY COOL CONDITIONS MAY PREVAIL FOR A WHILE IN
THE WAKE OF THIS SYSTEM...WITH BROAD TROFFING TRANSITIONING TO
ZONAL FLOW LATE NEXT WEEKEND INTO EARLY NEXT WEEK. THIS MAY
PROVIDE OPPORTUNITIES FOR PACIFIC SYSTEMS TO TRACK ACROSS THE
CONUS AND PERHAPS FAVOR PTYPES IN THE FORM OF SNOW VS. RAIN ACROSS
THE REGION DURING THE 2ND WEEK OF DECEMBER.
&&
.AVIATION /16Z MONDAY THROUGH FRIDAY/...
POOR FLYING CONDS FOR MUCH OF TDY AS WINDS HAVE TURNED NWSTRLY
BEHIND THE COLD FRONT. MIXED LYR SUGGESTS PSBL GUSTS TDY BTWN
15-20KTS...WHICH WILL PROVIDE SOME UPSLOPE SHSN FOR THE HIGHER
TERRAIN AIRFIELDS OF THE ALLEGHENIES AIDING IN PROLONGED IFR
PATCHY LIFR CONDS FOR JST/BFD. AOO/UNV/IPT SHUD BE MVFR AND MAY
GET INTO VFR SHORTLY. VFR WILL CONTINUE IN THE SE AS RA-- WILL
STOP BY 18-19Z. OVERALL EXPECT MVFR CIGS AND VSBYS FOR WESTERN
THIRD OF PA THRU TUES AM. DOWNSLOPING WILL KEEP DRY CONDS IN THE
SE.
OUTLOOK...
TUE...IFR/MVFR CIGS WEST WITH -SN. VFR EAST.
WED...VFR.
WED PM-THU...MVFR TO IFR CIGS. RA/BR.
FRI...MVFR/IFR W SHSN - VFR E.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...DANGELO/BEACHLER
NEAR TERM...DANGELO
SHORT TERM...BEACHLER
LONG TERM...DEVOIR/MARTIN
AVIATION...DANGELO
