FXUS61 KCTP 160220
AFDCTP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
920 PM EST TUE DEC 15 2009

.SYNOPSIS...
COLDER AIR WILL CONTINUE TO FILTER INTO THE REGION BEHIND A COLD
FRONT MOVING OFF THE EASTERN SEABOARD. THIS IS THE START OF
AN EXTENDED PERIOD OF BELOW NORMAL TEMPERATURES...AND MOUNTAIN
SNOW SHOWERS THAT WILL LAST RIGHT INTO THE UPCOMING WEEKEND. AN
AREA OF LOW PRESSURE MAY DEVELOP ALONG THE SOUTHEAST COAST OF THE
U.S. SATURDAY NIGHT AND MOVE NORTHEAST...BRINGING A CHANCE FOR
SOME SNOW SUNDAY INTO MONDAY.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
SHARP 500 MB VORT LOBE AND THE APPROACH OF THE LEFT EXIT REGION 
OF A 115 KT UPPER JET FROM THE NW WILL BRING A SEVERAL HOUR PERIOD
OF ENHANCED UVVEL ACROSS THE REGION UNTIL SHORTLY AFTER MIDNIGHT. 
FAIRLY STRONG/NARROW BAND(S) OF 800-700MB FRONTOGENESIS WILL HELP
TO FOCUS SOME BRIEFLY...MDT TO HVY SNOW SHOWERS/SQUALLS ACROSS
THE CENTRAL AND NW PORTIONS OF OUR CWA THROUGH ABOUT 06Z. 

LATE TONIGHT...THESE FEATURES WILL SLIDE EAST OF THE REGION (AND
THE SUBSIDENCE INVERSION WILL LOWER BY ABOUT 2 KFT) WITH THE
COLDER NW FLOW AT THE SFC AND ALOFT CONFINING THE SNOW SHOWERS
MAINLY TO THE FAR NW MTNS...AND LAUREL HIGHLANDS OF SWRN PENN.

HI RES MDLS SHOW A MULTI-BAND LES CONFIGURATION SETTING UP WITH
MAINLY LOCATIONS ACROSS THE NW MTNS AND LAURELS PICKING UP AN
INCH OR TWO BY WED AM. AS THE S/WV TROUGH TAKES ON A NEGATIVE TILT
INTO NRN NEW ENG...LOW PRES OVR DOWN-EAST MAINE AND CANADIAN
MARITIMES WILL DEEPEN AND TIGHTEN THE GRADIENT OVR CENTRAL
PENN...RESULTING IN GUSTY WNWLY WNDS 20-30KTS.

MODEL SOUNDINGS INDICATE THE INVERSION LOWERS SIGNIFICANTLY DURG
THE DAY WED SO THE BEST WINDOW OF OPPORTUNITY FOR ACCUM SNOW WILL
LIKELY BE CLOSING DURING THE MORNING. IT WILL PROBABLY REMAIN
CLOUDY HOWEVER...WITH A GUSTY WNW WIND AND SCATTERED SNOW SHOWERS
CONTINUING.

TEMPS ON TRACK TO REACH LOWS IN THE UTEENS ACROSS THE MTNS...LOWER
TO MID 20S THROUGHOUT THE CENTRAL VALLEYS...AND U20S IN THE LOWER
SUSQ VALLEY. 

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/...
HIGH PRESSURE WILL CONTINUE TO BRING COLD YET MAINLY FAIR WEATHER
TO THE REGION AS NORTHWEST FLOW CONTINUES. ANY LINGERING LAKE
EFFECT SNOW SHOWERS IN THE NW WILL TAPER OFF BY THU BUT STUBBORN
CLOUDS WILL LINGER OVER THE HIGHER TERRAIN. THU NIGHT LOOKS TO BE
A CHILLY ONE AS SKIES COULD CLEAR...BRINGING A SHOT FOR SINGLE
DIGIT LOWS ACROSS NORTHERN TIER WITH MOST OTHER LOCATIONS FALLING
INTO THE TEENS.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
AS PREV DISC NOTED...BLOCKING HIGH OVER GREENLAND APPEARS TO HOLD
THRU THE WEEKEND. THAT WILL IN TURN KEEP AN UPPER LOW STATIONED
OVER THE CANADIAN MARITIMES THROUGH THE WEEKEND WITH MID-LEVEL
TROUGH ACROSS ONTARIO/QUEBEC. BOTH GFS AND ECMWF SWING ENERGY BACK
AROUND TO THE WEST SIDE OF THIS TROUGH AND HINT AT A RETROGRADING
PATTERN...WITH GFS PUSHING ENERGY THROUGH AS A BACK DOOR FRONT
OVER THE WEEKEND. IN ADDITION...BOTH MODELS LATCH ONTO A WAVE
SLIDING DOWN THE ROCKIES LATE WEEK THAT SWINGS THROUGH THE SE AND
UP THE EAST COAST. BUT EVOLUTION OF THIS FEATURE DIFFERS GREATLY.
GFS DOESN/T DEVELOP MUCH OF A SFC LOW AT ALL WHILE ECMFW GENERATES
A DECENT SFC LOW BUT KEEPS IT OFFSHORE. SO WHAT DOES THIS ALL MEAN
FOR THIS FORECAST...PLENTY OF UNCERTAINTLY IN THE DETAILS ALTHOUGH
NOT POINTING TO A BIG STORM. BUT WITH TROUGH IN PLACE AND AN
INCREASE IN GENERAL FORCING...WOULD EXPECT AT LEAST A CHANCE FOR
SNOW SAT NIGHT INTO SUN...AND INTRODUCED THAT INTO THE FORECAST.
AM SURE THIS FOREAST WILL CONTINUE TO CHANGE AND EVOLVE AS WEEKEND
APPROACHED.

TROUGH OVER THE CENTRAL AND EASTERN U.S. BROADENS EARLY NEXT WEEK
AS BLOCKING PATTERN CONTINUES. FIRST PART OF THE WEEK MAY SEE
SCATTERED SNOW SHOWERS IN THE WESTERN HIGHER TERRAIN /BASICALLY
CLIMOTOLOGY/ WHILE THE EAST REMAINS DRY WITH NW/W FLOW.
ODDLY...WITH SUCH MODEL DIFFERENCES OVER THE WEEKEND...BOTH THE
GFS AND ECMWF INDICATING POTENTIAL FOR SOME WINTRY WEATHER NEXT
WED/THU. BUT CONFIDENCE QUIET LOW IN MODEL FORECAST THAT FAR OUT
BASED ON WEEKEND DIFFERENCES.

&&

.AVIATION /02Z WEDNESDAY THROUGH SUNDAY/...
HIGHER TERRAIN WILL CONTINUE TO DEAL WITH SCT SNOW SHOWERS BEHIND
FRONT WHICH WILL BRING PERIODS OF MVFR/IFR CONDITIONS THROUGH
06-09Z. WINDS WILL ALSO REMAIN GUSTY FROM THE NW THERE...AND WILL
PICK UP IN THE EAST FOR SEVERAL HOURS WITH FRONTAL PASSAGE.

ON WED...SCT SNOW SHOWERS WILL BE CONFINED MAINLY TO KBFD BUT
GUSTY NW WINDS WILL COVER THE ENTIRE AREA. 

OUTLOOK...
WED...MVFR AND OCNL -SHSN BFD/JST. MAINLY VFR ELSEWHERE.
THU-FRI...VFR. 
SAT-SUN...VFR WITH CHANCE OF MVFR IN LIGHT SNOW.

&&

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

&&

$$
SYNOPSIS...LA CORTE
NEAR TERM...LA CORTE/LAMBERT
SHORT TERM...RXR
LONG TERM...RXR
AVIATION...RXR