FXUS61 KCTP 050326
AFDCTP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
1026 PM EST THU DEC 4 2008

.SYNOPSIS...

HIGH PRESSURE WILL BUILD INTO THE REGION WITH MUCH COLDER AIR AND
THE USUAL COLD SEASON POST FRONTAL LAKE EFFECT AND OROGRAPHIC SNOW
SHOWERS. BELOW NORMAL TEMPERATURES WILL PERSIST THROUGH AT LEAST
EARLY NEXT WEEK WITH THE COLDEST TEMPERATURES OCCURRING SUNDAY
INTO MONDAY.

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...

THE COLD FRONT HAS MOVED THROUGH THE CWA WITH WINDS NOW WNW JUST
ABOUT EVERYWHERE. WESTERLY LOW LEVEL FLOW WILL CONFINE MOST OF THE
LAKE EFFECT TO MY FAR NWRN ZONES AND AREAS NEAR THE NY BORDER...SO
WIDESPREAD SNOW SHOWERS NOT LIKELY. HAVE LOWERED POPS A BIT OVER
THE LAURELS WHERE RELATIVELY LOW INVERSION HEIGHTS AND DRY AIR WILL
MAKE ORGANIZED SNOW SHOWERS HARD TO GENERATE.

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH SATURDAY/...
ON FRIDAY LAKE-EFFECT SNOW SHOWERS SHOULD CONTINUE ESPECIALLY ACROSS
WARREN AND MCKEAN COUNTIES... HOWEVER THESE SHOULD CONTINUE TO BE
LIGHT WITH AN ADDITIONAL INCH OR TWO POSSIBLE IN SPOTS. WINDS BEGIN
TO SHIFT TO THE WSW IN THE AFTERNOON WHICH WILL PUSH ANY LAKE-EFFECT
SNOW NORTH OF THE PA BORDER. THE REST OF THE AREA WILL EXPERIENCE
JUST MOSTLY CLOUDY SKIES WITH HIGHS RANGING FROM THE MID 20S IN THE
FAR NORTH TO THE LOW 30S ACROSS THE CENTRAL RIDGE AND VALLEY AREA
AND THE MID TO UPPER 30S ACROSS THE SUSQUEHANNA VALLEY.

FRIDAY NIGHT SHOULD BE PARTLY CLOUDY ACROSS MUCH OF THE STATE AND
WITH A HIGH MOVING OVERHEAD EXPECT A COLD NIGHT. WENT WITH LOWS IN
THE LOW TEENS ACROSS THE NORTH TO THE LOW 20S ACROSS THE FAR
SOUTHEAST. THE WINDS MAY STAY A BIT GUSTY WHICH COULD KEEP THE LOWS
FROM FALLING TOO FAR... BUT IF THEY CAN GO CALM AND IT CLEARS OUT WE
MAY SEE LOWS EVEN A FEW DEGREES BELOW CURRENT FORECAST. A CLIPPER
WILL DROP TOWARDS THE AREA ON SATURDAY BRINGING AN INCREASE IN THE
CLOUDS. LEANED TOWARDS THE GFS AND THE SREF IN REGARD TO TIMING OF
THE ONSET OF LIGHT SNOW. THIS WOULD BRING THE SNOW INTO WESTERN
COUNTIES AND APPROACHING CENTRAL AREAS BY 0Z.

&&

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
SHRTWV ENERGY ASSOC WITH THE PREVIOUSLY NOTED CLIPPER SYSTEM IS
EXPECTED TO DIG FAIRLY SHARPLY OVER THE GREAT LAKES REGION THIS
PD...EVENTUALLY GOING NEG TILT OVER THE NORTHEAST. THE
EMBEDDED ALBERTA CLIPPER LOW WILL SWEEP SOUTHEAST THROUGH THE UPPER
LAKES AND ROTATE INTO SRN ONTARIO ON SUNDAY. MEANWHILE....THE MODELS
CONTINUE TO INDICATE SECONDARY CYCLOGENESIS OFF THE MID ATL COAST.
THERE IS STILL SOME DISAGREEMENT AMONG THE GUIDANCE REGARDING THE
AMPLIFICATION OF THE UPPER TROF AND STRENGTH/POSITION OF THE
SECONDARY SFC LOW. REGARDLESS OF THE MODEL DIFFS...IT STILL
APPEARS THAT THE COASTAL SYS WILL REMAIN FAR ENUF OFFSHORE TO
PROVIDE VERY LITTLE IF ANY DIRECT IMPACT TO THE REGION. SENSIBLE
WEATHER IMPACTS WILL BE PRIMARILY FELT WITH THE CLIPPER
LOW...WHICH SHOULD YIELD A SWATH OF LGT WARM ADV SNOWS /1-3"/
ACROSS THE NORTHERN AND CENTRAL MOUNTAINS FROM SAT NGT INTO EARLY
SUN.

A SURGE OF MODIFIED ARCTIC AIR WILL BE DIRECTED INTO THE REGION IN
THE WAKE OF THE CLIPPER AS THE UPPER TROF AXIS SHIFTS EAST OF THE
GREAT LAKES. THE BLUSTERY CYCLONIC/NWLY FLOW SHOULD LEAD TO WDSPRD
LAKE EFFECT AND OROGRAPHIC SNOW SHOWERS LATER SUNDAY INTO EARLY
MONDAY...WITH SOME MOD ACCUMS PSBL FROM THE SNOWBELT SWD ALONG THE
WESTERN ALLEGHENIES. GEFS DATA CONTINUES TO SHOW HIGH PRESSURE MOVG
INTO THE AREA FOR MONDAY WITH DRY CONDS XPECTED...BUT THEN QUICKLY
RETREATING OFF THE EAST COAST LATER MON NGT AS MID AND HIGH LVL MSTR
INCREASES FROM THE WEST. A MANUAL BLEND OF TEMPERATURE DATA
WEIGHTED HEAVILY TOWARD THE 06/12Z NAEFS RESULTS IN HIGHS 15 TO 20
DEGS BLW CLIMATOLOGY SUN/MON.

PREVIOUS RUNS OF THE ECMWF AND AND GFS SHOWED MAJOR DETERMINISTIC
DIFFS...WITH THE GFS ATTEMPTING TO PHASE NORTHERN AND SOUTHERN
STREAM FLOWS OVER THE CONUS...RESULTING IN A MAJOR CYCLONE IN THE
EAST. MEANWHILE...THE ECMWF MAINTAINED TWO DISTINCT FLOWS WITH
GREATER EMPHASIS ON THE SOUTHERN STREAM. HPC HAS NOTED THAT THE GFS
HAS BACKED OFF SLIGHTLY FROM ITS PREVIOUSLY PHASED SOLUTION. WITH
THAT SAID...THE 12Z GFS ENSEMBLE MEAN /GEFS/ SHOWS A DEEPENING
SURFACE WAVE TRACKING NEWD FM THE LWR MS VLY AND INTO THE MID ATLC
TUE-WED. PLUME DIAGRAMS CONTINUE TO SUGGEST A SIGNIFICANT
PRECIPITATION EVENT CENTERED AROUND 00Z DEC 10. CONSIDERABLE
UNCERTAINTY REMAINS WITH THE DETAILS OF THIS SYSTEM...BUT INCREASING
CONFIDENCE IN THE EVENT ITSELF HAS PROMPTED AN INCREASE IN
POPS...WHICH REFLECT A NEAR 50/50 BLEND OF HPC AND GMOS.

TEMPERATURES SHOULD MODERATE SEVERAL DEGREES INTO MIDWEEK. HOWEVER BY
THUR/FRI THE OPERATIONAL GFS...AND TO A LESSER EXTENT ITS ENSEMBLE
MEAN...SUGGEST A VERY COLD/ARCTIC AIRMASS INVADES THE REGION.
THIS IS SUPPORTED BY THE 12Z NAEFS DATA...WHICH HAS SHOWN
CONSIDERABLE SKILL OVER OTHER GUIDANCE IN THE MEDIUM TO LONG
RANGE.

&&

.AVIATION /04Z FRIDAY THROUGH TUESDAY/...
RESIDUAL MOISTURE LINGERING ACROSS LOWER SUSQ VALLEY...HOWEVER
WITH DRY LLVL/S QUICKLY FILTERING INTO THIS REGION EXPECT CIGS TO
IMPROV TO MVFR THEN VFR BY 12Z FRI. ACROSS CENTRAL PA AIRFIELDS
WEAK DOWNSLOPING WAS HELPING TO THIN STRATUS ACROSS
KUNV/KAOO/KJST...EXPECT PATCHY MVFR CIGS TO LINGER THRU SUNRISE
FRI. CONFIDENCE HAS INCREASED THAT CIGS FOR CENTRAL PA AIRFIELDS
COULD REMAIN AT VFR AFT 12Z THRU MUCH OF FRI AFTN.

AN AREA OF DEEPER MOISTURE WAS EVIDENT FROM LATEST IR IMAGERY OVER
LAKE ERIE...SLIDING EAST. EXPECT AS MOISTURE APPROACHES KBFD AND
OTHER NORTHWEST MTNS AIRFIELDS LAKE INDUCED CLOUDS WILL BE
GENERATED...PROB AFT 04Z. PROFILES HOWEVER DO NOT LOOK TOO
FAVORABLE FOR ORGANIZED LES BANDS FRI MORNING. FLOW IS PRETTY
DIRECTIONAL...THUS A LITTLE CONCERNED TO WHAT EXTENT LES AND
FAVORED UPSLOPE PRECIP WILL OCCUR FOR AIRFIELDS ACROSS ALLEGHENIES
AND NORTHWEST MTNS.

AFT 18Z FRI HI-RES LCL WRF/S PAINT GROWING DIRECTIONAL WIND
GRADIENTS...COUPLED WITH WEAKENING LLVL MOISTURE AND THIS SHOULD
CUT OFF LES FOR MOST WESTERN PA AIRFIELDS. EXPECT WEAK DOWNSLOPING
TO DRY LOW/MID LVL ATMOS OVER KMDT/KLNS ALLOWING FOR VFR CIGS FRI
INTO FRI NGT. THIS IS SUPPORTED AS WEAK SFC RIDGE CENTERED ACROSS
KENTUCKY PROVIDES A WEAK INFLUENCE INTO SUSQ VALLEY THRU MIDDAY
SAT.

A LOW PRES SYSTEM PASSING TO OUR NORTH COULD PRODUCE
DETERIORATING CONDS WITH -SN LATE SAT/SAT NITE. A RETURN TO
TYPICAL LAKE EFFECT REGIME EXPECTED SUNDAY/MONDAY WITH
PREDOMINANTLY MVFR CONDS OVR THE ALLEGHENIES AND VFR CONDS ACROSS
THE SUSQ VALLEY. THEN ANOTHER SYSTEM COULD PROVIDE REDUCED
CIGS/VSBYS MON NGT/TUE.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
NONE.

&&

$$
SYNOPSIS...LACORTE
NEAR TERM...LACORTE/CHENARD
SHORT TERM...LAMBERT/CHENARD
LONG TERM...STEINBUGL
AVIATION...LAMBERT/BEACHLER



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