FXUS61 KCTP 010309
AFDCTP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
1009 PM EST MON NOV 30 2009
.SYNOPSIS...
COLD AIR IS CROSSING THE GREAT LAKES AND SNOW SHOWERS CAN BE
EXPECTED ACROSS THE MOUNTAINS OF NORTHERN AND WESTERN PENNSYLVANIA
THROUGH TUESDAY MORNING. AN AREA OF HIGH PRESSURE WILL BUILD INTO
THE REGION TUESDAY THROUGH WEDNESDAY. LOW PRESSURE WILL MOVE FROM
MISSISSIPPI INTO THE UPPER OHIO VALLEY FOR LATE WEDNESDAY AND
THURSDAY. MAINLY RAIN IS EXPECTED WITH THIS STORM...WITH SNOW
SHOWERS ONLY OCCURRING IN THE WEST AS THE STORM DEPARTS LATE
THURSDAY INTO FRIDAY. COLDER TEMPERATURES ARE THEN IN STORE FOR
THE WEEKEND.
&&
.NEAR TERM /UNTIL 8 AM TUESDAY MORNING/...
COLD...-6C 8H AIR MOVING ACROSS LAKE ERIE WATERS AT +9C (WITHIN A
POCKET OF MID LEVEL LAPSE RATES OF GREATER THAN 6C/KM) WAS
PRODUCING SCATTERED SNOW SHOWERS ACROSS NORTHWESTERN...AND PART OF
CENTRAL PENN THIS EVENING.
LOCAL 12KM WRF RUN FROM 18Z HAS PRETTY MUCH "NAILED" THE BAND OF
LLVL MOISTURE CONVERGENCE...HIGHLIGHTED BY THE CONCENTRATION OF
SNOW SHOWERS/BRIEF SQUALLS FROM NEAR KERI...SE TO KDUJ AND KFIG
(FIZZLING OUT AS THEY REACH THE KUNV AREA).
THIS AREA OF LLVL FORCING WILL DRIFT GRADUALLY TO THE ENE AND
EVEN STRENGTHEN BRIEFLY NEAR KBFD AROUND 05Z...BEFORE LIFTING
INTO THE SOUTHERN TIER OF NEW YORK AS THE MEAN BOUNDARY LAYER (AND
285K ISENTROPIC) FLOW BACKS TO A MORE WSW DIRECTION OVER THE WRN
THIRD OF PENN (CUTTING OFF THE MOISTURE FEED FROM THE GLAKES OVER
MUCH OF OUR NW MTNS).
THE SNOW SHOWERS WILL LIKELY CONSOLIDATE INTO A QUASI-SINGLE LAKE
SHORE PARALLEL BAND (BRIEFLY) NEAR...AND JUST TO THE SE OF
INTERSTATE 90 LATE TONIGHT BEFORE LIFTING FURTHER NORTH OVER
CENTRAL/ERN LAKE ERIE BEFORE DAYBREAK...AS THE MEAN WIND FROM THE
SFC TO 4000 FEET AGL SHIFTS TO AROUND 245 DEG.
WILL ADJUST THE MEASURABLE SNOW PROBABILITIES UP A LITTLE ACROSS
THE FAR NW ZONES OVERNIGHT. OTHERWISE...THE GENERALLY LIGHT AND
SPOTTY SNOW SHOWERS ARE REFLECTED QUITE WELL IN THE 20 PERCENT (OR
LESS) POPS TO THE SE OF THE ALLEGHENIES OVERNIGHT.
IT IS LIKELY THAT THE NWRN MTS (ESP WARREN AND WESTERN MCKEAN
COUNTIES) WOULD SEE THE BEST ACCUMS FROM THIS AS THE FLOW IS DRY
INTO THE LAURELS. WILL MENTION 1-3 INCH ACCUMS IN THE FAR NW...BUT
ONLY AN INCH OR LESS FOR THE LAURELS - MAINLY SOMERSET CO. A LIGHT
COATING OF SNOW WILL ALSO OCCUR ACROSS THE NCENT MTNS.
MINS TEMPS WILL BE A LITTLE ABOVE NORMS ACROSS THE CWA TONIGHT
WITH CLOUDS KEEPING IT MILDER NW AND PARTIAL CLEARING ALLOWING FOR
BETTER RAD COOLING SE. DAYBREAK TEMPS IN THE M20S TO L30S ARE IN
STORE.
&&
.SHORT TERM /8 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/...
LAKE EFFECT TUES AM SHOULD DWINDLE RATHER QUICKLY AS CROSS LAKE
FLOW POINTS TOWARD KBUF AND AWAY FROM THE LOCAL AREA. THE 1020MB
SFC HIGH SLIDES WELL TO OUR S...BUT FLOW VERY ZONAL FOR TUES AND
WILL HELP TO CLEAR THINGS OUT FM W-E ACROSS THE CWA. THE SUNSHINE
IN THE S/CENT WILL HELP MAX TEMPS GET TO THE U30S-U40S. THESE ARE
STILL A FEW DEGS F ABOVE NORMS.
&&
.LONG TERM /TUESDAY NIGHT THROUGH MONDAY/...
STILL LOOKING AT DRY CONDITIONS TUESDAY NIGHT INTO WED. LIKE
YESTERDAY...TEMPS WARM NICELY AT 850 MB TUESDAY NIGHT...SO NOT
LOOKING AT ANYTHING REAL COLD TUE NIGHT.
STILL SOME TIMING ISSUES FOR WED. ADJUSTED GRIDS TO FIT OTHERS ETC.
TOOK OUT SNOW FOR WED NIGHT AND THU...NAM IS FURTHER WEST TODAY.
THE NAM MAY BE TOO FAR WEST...BUT EITHER WAY...LOW LIKELY TO
TRACK NORTHWARD TOWARD SYR...THUS WE SHOULD BE ON THE WARM SIDE
OF THE STORM.
THE COMBINATION OF WARM ADVECTION AND DYNAMICS WILL LIKELY
SUPPORT THUNDER. HAVE TO WATCH THE LEADING EDGE OF THE DRY AIR
ALOFT...FOR THE THREAT OF STRONG WINDS AND/OR SEVERE STORMS.
SOME LAKE EFFECT FOR THU NIGHT INTO SAT...BUT WINDS ALOFT STAY
SW AND THERE IS MORE DIRECTIONAL SHEAR NOW...SO DID CUT AREA
OF LAKE EFFECT DOWN.
VORT MAX COULD TRIGGER SOME RAIN AND SNOW SHOWERS FOR SAT ACROSS
THE AREA EAST AND SOUTH OF THE MTS...THUS ADDED IN LOW CHC POPS.
WENT WITH MAINLY A DRY FCST FOR SUNDAY INTO MONDAY...HARD TO SEE
ANY DECENT SYSTEMS WITH A WARM UP OR WIDESPREAD PCPN...AS THE GFS
HINTED AT YESTERDAY. A LOT OF SPREAD IN DETAILS AS ONE GOES OUT IN
TIME.
THE MAIN THING IS A LARGE OMEGA BLOCK FORMS NEAR ALASKA IN TIME...
WOULD LEAD TO COLDER CONDITIONS FOR THIS AREA...BUT PERHAPS NOT
REAL COLD. HARDER CALL ON STORM POTENTIAL AT THIS POINT...BUT
AFTER ALL IT IS DEC...AND OLD MAN WINTER WILL MAKE HIS ROUNDS
AT SOME POINT.
&&
.AVIATION /03Z TUESDAY THROUGH SATURDAY/...
LK EFF SHSN WILL AFFECT KBFD ALL NIGHT AND SOME UPSLOPE SHSN ARE
POSSIBLE AT KJST. AN EXTENDED ZONE OF LLVL CONV AND HIGH MSTR ORIG
FM LH WILL CROSS LE AND COULD CREATE IFR CONDS IN SHSN ALL THE WAY
FM BFD INTO UNV EARLY TONIGHT. OTHERWISE...MOST OF THE SHSN WILL
BE CONFINED TO AREAS CLOSER TO KBFD. A CROSS-LAKE FLOW FM 320 WILL
BACK TO 260 BY MORNING...AND HELP TO DIMINISH THE LK EFF SHSN
AROUND 12Z. WINDS WILL BE GUSTY THIS EVENING AS THE FLOW IS WELL-
ALIGNED...BUT THAT BACKING DOES NOT OCCUR AT ALL LEVELS AND THE
DECOUPLING SHOULD HELP TO TAKE AWAY THE GUSTS AND SUBTRACT A FEW
KT FM THE SFC WINDS TONIGHT.
AOO/IPT SHUD BE VFR MOST OF THE NIGHT...ALTHOUGH THEY COULD GET A
BRIEF LIGHT SHSN OR REDUCTION TO MVFR CIG. DOWNSLOPING WILL KEEP
DRY/VFR CONDS IN THE SE - KMDT. AS THE PRESSURES RISE TUES...THE
SHSN WILL GET NUDGED INTO NY STATE AND SKIES WILL EVEN BEGIN TO
CLR FM W-E BY 18Z OVER MOST OF THE S AND CENT AIRFIELDS.
OUTLOOK...
WED...VFR.
WED PM-THU...MVFR TO IFR CIGS. RA/BR.
FRI AND SAT...MVFR/IFR W SHSN - VFR E.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...DANGELO/LAMBERT
NEAR TERM...DANGELO/LAMBERT
SHORT TERM...DANGELO
LONG TERM...MARTIN
AVIATION...DANGELO/GARTNER
