FXUS61 KCTP 270940
AFDCTP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
440 AM EST FRI NOV 27 2009
.SYNOPSIS...
COOL AND BLUSTERY CONDITIONS WILL LAST LINGER INTO SATURDAY FOR
PENNSYLVANIA. SCATTERED RAIN BECOMING MIXED WITH SNOW SHOWERS FOR
THE HIGHER ELEVATIONS OF THE ALLEGHENIES TODAY. ADDITIONAL SNOW
SHOWERS TONIGHT ACROSS THE ALLEGHENIES WITH A RIDGE OF HIGH
PRESSURE SLOWLY BUILDING IN FROM THE WEST. CONTINUED UNSETTLED
WEATHER FOR EARLY NEXT WEEK AS A COLD FRONT BRINGS ANOTHER CHANCE
FOR RAIN AND SNOW SHOWERS.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
CHALLENGES FOR TODAY RESIDE AROUND ARRIVAL OF PRECIP INTO THE
ALLEGHENIES...AND COVERAGE OF PRECIP AND DEPARTING FRONTAL BNDRY
ACROSS SUSQ-VALLEY THIS MORNING. 500MB TROUGH AXIS CONTINUES TO TAKE
ON A NEGATIVE TILT...WITH A SERIES OF WEAK LLVL LOBES OF VORTICITY
PIVOTING ARND TROUGH AXIS. NEGATIVE TILT WILL ALSO ALLOW COASTAL LOW
TO STEADILY INTENSIFY AND PUSH INTO THE NORTHEAST REGION.
IR IMAGERY THIS MORNING INDICATES A WEAK VORT ACROSS LAKE
ERIE/NORTHERN OHIO...WITH A SECOND LLVL VORT MAX UPSTREAM ACROSS
LAKE MICHIGAN/WISCONSIN. POST FRONTAL PASSAGE HAS ALLOWED FLOW TO
TURN W/NWSTRLY. MIXED LYR INCREASES THIS AFTN TO 1800-2200FT AGL
FILTERING TO THE SFC A CORE OF 25-35KT WINDS. ATTM ANTICIPATE SUB
WIND ADV CONDS...HOWEVER GUSTS WILL STEADILY INCR AFT 18Z TO
20-25KTS. DEEP MOISTURE ARRIVES THIS MORNING...THUS HAVE ADJUSTED
POPS ACCORDINGLY FOR THE WESTERN MTNS. WEAK DOWNSLOPING AND MARGINAL
SUBSIDENCE COULD ERODE BNDRY LYR MOISTURE DOWNSTREAM IN THE
SUSQ-VALLEY. THIS SCENARIO SUGGESTS FEWER CLOUDS FOR MUCH OF
TODAY...HOWEVER DEPARTURE OF COASTAL LOW WILL ALSO PROVIDE ADDTL
MOISTURE AND LIMIT ANY POTENTIAL OF SUNSHINE.
DESPITE LOWEST 0-3KM FLOW IS UNI-DIRECTIONAL...DENDRITIC GROWTH
APPEARS TO BE LOFTY ARND 8-10KFT AGL THIS AFTN. THAT SAID TEMPS
SUPPORT PRECIP AS SN...POSSIBLY MIXED AT TIMES WITH RA TODAY. CONSID
SOLAR FILTERING AND 925MB TEMPS ARND 0 TO -3 DEG C...HAVE HELD TEMPS
IN THE M30S FOR THE PLATEAU REGION/LAUREL HIGHLANDS. DOWNSTREAM
TEMPS SHUD TOP OUT THIS AFTN ARND 40...AND M40S IN THE SUSQ-VALLEY.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SATURDAY/...
EARLY THIS EVE NEGATIVE TILT TROUGH AXIS PIVOTS THRU WITH A WEAK
LOBE OF VORTICITY PUSHING THRU ARND 00Z. DEEP MOISTURE QUICKLY PEELS
TO THE NE...WHICH MAKES TONIGHTS FORECAST DIFFICULT. NW FLOW
STRENGTHENS WITH GUSTS APPROACHING 30-35KTS...STILL EXPECT SUB-ADV
CRITERIA. GIVEN BLUSTERY CONDS...PARCELS THAT TRAVERSE LAKE ERIE
WILL SEE REDUCED RESONANCE TIME LIMITING INFLUENCE OF ORGANIZED LES
BANDS. QPF WILL BE LOW AS WELL FOR TONIGHT. BASED ON AFOREMENTIONED
ELEMENTS...IT APPEARS OROGRAPHICAL LIFT MECHANISM FOR SN WILL BE
MAXIMIZED FOR THE ALLEGHENIES. THUS POSSIBLE SN ACCUMS FOR HIGHER
TERRAIN ARND 1-3 INCH. ATTM IT DOESN/T APPEAR ANY HEADLINES WILL BE
NEEDED. OVERNIGHT TEMPS SHUD COOL INTO THE U20S/M30S ACROSS THE
CWFA.
&&
.LONG TERM /SATURDAY THROUGH THURSDAY/...
OVERALL PATTERN CONTINUES TO TRANSITION TO MORE SEASONABLE
CONDITIONS. BRIEF LAKE EFFECT REGIME ENDS EARLY SATURDAY FOLLOWED
BY A PERIOD OF ZONAL FLOW SUNDAY INTO MONDAY. MEANWHILE...AN
AMPLIFIED EASTERN PACIFIC RIDGE WILL REACH THE WEST COAST BY MONDAY...
WITH DOWNSTREAM TROFFING EXTENDING INTO THE GREAT LAKES AND
NORTHEAST LATE MONDAY AND TUESDAY. BY MID TO LATE WEEK...AN UPPER
LEVEL CUTOFF MAY EJECT INTO THE SOUTHERN PLAINS...REACHING THE
MID ATLANTIC REGION ON WEDNESDAY AND POTENTIALLY SPREADING SOME
RAINFALL OVER PORTIONS OF CENTRAL PA WEDNESDAY NIGHT INTO
THURSDAY. THIS SYSTEM WILL BE FOLLOWED BY SEASONABLE CONDITIOSN
FOR THE REMAINDER OF NEXT WEEK.
&&
.AVIATION /10Z FRIDAY THROUGH TUESDAY/...
FRONTAL BNDRY CONTINUES TO PUSH EAST...HOWEVER SLOWING AS IT
SLIDES ACROSS THE SUSQ-VALLEY AIRFIELDS. POOR FLYING CONDS WILL
PERSIST THRU 10Z FOR IPT/MDT WITH BRIEF IMPROV CONDS. ACROSS THE
ALLEGHENIES FLOW HAS TURNED W/NWSTRLY AND WILL STEADILY INC.
JST/AOO/UNV WILL SEE BRIEFLY VFR CONDS...THEN TURN TO MVFR/IFR AS
PRECIP COVERAGE INCREASES. TEMPS HAVE COOLED BEHIND THE FRONT
ACROSS THE ALLEGHENIES AND LGT PRECIP HAS BECOME MIXED AT TIMES
WITH RASN AND PL. IN AND ANRD PRECIP VSBYS/CIGS WILL FLUCTUATE
BTWN MVFR/IFR CONDS TODAY.
OUTLOOK...
SAT...IFR/MVFR W/NW IN HIGH TERRAIN SHSN. VFR E OF THE
ALLEGHENIES IN SCT RASN.
SUN...VFR.
MON...IFR/MVFR SHRA.
TUE...IFR/MVFR W...MVFR/VFR E IN POST FRONTAL SHOWERS.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...LA CORTE/BEACHLER
NEAR TERM...BEACHLER
SHORT TERM...BEACHLER
LONG TERM...DEVOIR/MARTIN
AVIATION...BEACHLER
