000
FXUS61 KCTP 200634
AFDCTP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
134 AM EST THU NOV 20 2008

.SYNOPSIS...
A DEEP UPPER LEVEL TROUGH WILL DOMINATE OUR WEATHER THROUGH THIS
UPCOMING WEEKEND...KEEPING CENTRAL PENNSYLVANIA UNSEASONABLY COLD
WITH SEVERAL BOUTS OF LAKE EFFECT AND OROGRAPHICALLY ENHANCED SNOW
SHOWERS. AN AREA OF LOW PRESSURE MOVING SOUTHEAST ACROSS THE
GREAT LAKES TONIGHT AND OVER NORTHERN PENNSYLVANIA ON THURSDAY
WILL SPREAD LIGHT...FLUFFY SNOW OVER THE CENTRAL AND NORTHERN
PART OF THE STATE.

&&

.NEAR TERM /UNTIL 5 AM THIS MORNING/...
NOTHING MORE THAN A FEW FLURRIES FALLING OVER THE NORTHWEST AS
CIGS REMAIN ABOVE 6K FEET. A FEW LOCALIZED FLAKES WERE REPORTED
OVER THE SOUTHEAST AN HOUR AGO AS A SMALL AREA OF ENHANCEMENT
ALONG THE LEADING EDGE OF THE DRY AIR ALOFT APPROACHED.

LCL WRF ARW DEPICTS ISOLATED S-- UNTIL 06Z...THEN AREAS OF S-
INCREASING OVER MY NORTHWEST COUNTIES BY 10Z. EXPECT BY THAT TIME
FOR CIGS TO FINALLY DROP BELOW 2K FEET WITH STEADY BUT GENERALLY
LIGHT SNOWFALL AS THE 1011 MB SFC LOW CONTINUES TO FILL AND DROPS
TO THE SOUTH AHEAD OF THE SFC FRONTAL BOUNDARY AND TRAILING SFC
TROF.

PREVIOUSLY ISSUED WATCHES IN GOOD SHAPE FOR LATER THURSDAY THROUGH
FRIDAY NIGHT AS LAKE ENHANCEMENT AND OROGRAPHICS KICK IN.
ESSENTIALLY NO CHANGES TO THE GOING FORECAST GRIDS/TEXT THIS EVENING.

&&

.SHORT TERM /5 AM THIS MORNING THROUGH 6 PM FRIDAY/...
ALBERTA CLIPPER WILL TRACK ACROSS NORTHERN PA DURING THURSDAY
MORNING...AS THE SFC LOW SEEMS TO REACH ERIE AROUND 12Z. WILL KEEP
POPS HIGH LATE TONIGHT WITH ONLY MINOR ACCUMS IN THE NW BEFORE
SUNRISE. TEMP PROFILE WILL BE FAVORABLE FOR A VERY FLUFFY
SNOWFALL...WITH S:W RATIOS ON THE ORDER OF 30:1 POSSIBLE. SO...
DESPITE THE QPF ESTIMATES ALL AROUND 0.1 INCHES...THERE COULD BE
2-3 INCHES OF SNOW FROM THIS WAVE BEFORE IT CHANGES TO MORE OF A
LAKE-EFFECT PATTERN LATE IN THE DAY. THE HIGHEST AMOUNTS WILL BE
ALONG THE NY BORDER AND OVER THE HIGHER HILL TOPS OF THE WEST.
HOWEVER...MUCH OF THE AREA NW OF IPT/UNV/AOO COULD GET AN INCH.
THE SERN THIRD/HLF OF THE AREA WILL GET SOME LIGHT SNOW OR
FLURRIES BUT ACCUMS WILL BE LITTLE TO NONE. TEMPS IN THE LOWER
SUSQ MAY EVEN BE MARGINAL FOR RAIN/SNOW IN THE AFTN.

THEN BY THE END OF THE DAY...THE PATTERN CHANGES TO THE NORTHWEST
FLOW AND GOOD UPSLOPE FLOW FOR THE LAURELS AND WRN MTS. S:W RATIOS
FALL AS THE SNOW GETS LESS DENDRITIC AND MORE ICY THOUGH. THE
WINDS SEEM WELL- ALIGNED FOR THE LAURELS TO GET LOTS OF SNOW THURS
NIGHT AND FRIDAY...THEN WE SHOULD SEE A GRADUAL SHIFT TO THE
NORTH...AND INTO THE NW LAKE EFFECT BELT DURING THE DAY FRIDAY AS
THERE IS A GREAT/LONG FETCH FROM LK HURON. SHOWERS MAY BE TOO
CELLULAR DURING THE DAY FRIDAY TO REALLY ACCUM IN LARGE AMTS
THOUGH. INVERSION IS HIGH AND THE TOP OF THE CLOUDS ARE STILL IN
THE GOOD DGZ.

WILL CARRY HIGH POPS THROUGHOUT THE PERIOD FOR THE WRN
HIGHLANDS...WITH LIGHT TO MODERATE ACCUMS ALMOST EVERY PERIOD.

WILL TRY TO GET A LITTLE MORE REFINED AS TO A HIGHER THREAT FOR
DEEP UPSLOPE SNOWS IN THE LAURELS LATE THURS INTO FRIDAY WITH A
WINT STORM WATCH...AND FOR DEEP LK EFF SNOWS OVER THE FAR NW WITH
A LK EFF SNOW WATCH FOR WARREN COUNTY FOR THURS NIGHT INTO FRI
NIGHT.

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
LAKE EFFECT SNOW EVENT WILL BE ONGOING TO START THE PERIOD AS COLD
NW FLOW PERSISTS. TROUGH AXIS SLIDES EAST DURING THE DAY ON SAT
AND SHOWERS WILL BE CONFINED TO MAINLY THE NORTHERN TIER AND
DIMINISHING AS THE DAY WEARS ON. ALTHOUGH NW FLOW WILL CONTINUE
ALOFT...SURFACE HIGH SLIPS THROUGH SAT NIGHT INTO SUN NIGHT WITH
COLD YET DRY WEATHER.  SAT NIGHT HAS THE POTENTIAL TO BE THE COLD
NIGHT SO FAR THIS SEASON. LIGHT WINDS...CLEARING SKIES AND SNOW
COVER COULD RESULT IN SINGLE DIGIT LOWS OVER THE ALLEGHENIES.

NEXT SHORTWAVE WILL BRING ANOTHER FAIRLY SIGNIFICANT TROUGH FOR
EARLY NEXT WEEK. DETAILS REMAIN DIFFICULT TO NAIL DOWN AT THIS
TIME FRAME...BUT DETERIORATING WEATHER MON-WED WITH A PERIOD OF
LIGHT PRECIP /PROBABLY SHSN/ . TEMPS REMAIN BLW NORMAL THRU AT
LEAST THE MIDDLE OF NEXT WEEK.

&&

.AVIATION /06Z THURSDAY THROUGH MONDAY/...
REGIONAL RADAR AT 06Z SHOWS LIGHT SNOW /2.5-5SM/ BREAKING OUT
ACROSS NRN PA AND SWRN NY STATE...ASSOC WITH WEAK CLIPPER LOW
APPROACHING THE LWR GRT LKS FROM INVOF ERN LAKE HURON IN SRN
ONTARIO. HIGH RES MDL GUID SHOWS THE WEAK CLIPPER LOW SLOWLY
SLIDING SEWD THRU NE PA TNT AND EVENTUALLY MOVG OFF THE MID ATLC
COAST BY FRI AM. OVER TIME...THE LOW LEVEL FLOW /VEERING AROUND TO
THE NW/ WILL BECOME MORE FAVORABLE FOR LAKE EFFECT AND
OROGRAPHICLY ENHANCED SNOW ACROSS THE NORTHWEST MOUNTAINS AND
LAUREL HIGHLANDS. BFD AND JST WILL LIKELY EXPERIENCE THE WORST
FLYING CONDS - AS IS USUALLY THE CASE. CENTRAL TERMINALS AOO/UNV
WILL LIKELY SEE TEMPORARY FLUCTUATIONS IN CIGS AND VIS /MAINLY
MVFR/ ALONG WITH OCNL SHSN. IPT/MDT SHOULD STAY VFR MOST OF THE
TIME...ALTHOUGH IPT COULD LOWER TO MVFR AT TIMES THIS MORNING IN
THE CLIPPER SNOW.

LAKE EFFECT/CYCLONIC FLOW REGIME APPEARS TO REMAIN IN TACT THROUGH
FRIDAY WITH SOME IMPROVEMENT ANTICIPATED FOR THE LATER IN THE WEEKEND.
ATTM...THE PD FM LATE SAT INTO SUNDAY LOOKS LIKE THE BEST CHC FOR
WDSPRD VFR AS A HIGH PRESSURE SYS BRIEFLY VISITS THE REGION.
HOWEVER...THE MDLS SHOW ANOTHER SYS APPROACHING FOR EARLY NEXT
WEEK.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
LAKE EFFECT SNOW WATCH FROM THIS EVENING THROUGH LATE FRIDAY
NIGHT FOR PAZ004.
WINTER STORM WATCH FROM THIS EVENING THROUGH FRIDAY AFTERNOON
FOR PAZ024-033.

&&

$$
SYNOPSIS...DANGELO/FITZGERALD
NEAR TERM...DEVOIR
SHORT TERM...DANGELO
LONG TERM...FITZGERALD/RXR
AVIATION...STEINBUGL

NWS CTP Office Area Forecast Discussion