FXUS61 KCTP 251201
AFDCTP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
701 AM EST FRI DEC 25 2009

.SYNOPSIS...
AN UPPER LEVEL LOW PRESSURE SYSTEM OVER THE PLAINS WILL MOVE EAST
OVER THE THE NEXT FEW DAYS...PASSING THROUGH PENNSYLVANIA BY EARLY
MONDAY. HIGH PRESSURE WILL BUILD INTO THE REGION FOR THE MIDDLE OF
NEXT WEEK.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
WATER VAPOR IMAGERY SHOWING UPPER LOW LIFTING NORTH OVR THE
MISSISSIPPI VALLEY THIS MORNING. AHEAD OF THIS FEATURE...BLENDED TPW
PRODUCT SHOWING DEEP...MOIST SOUTHERLY FLOW ORIGINATING OVR GULF
OF MEX AND EXTENDING NORTHWARD INTO THE OHIO VALLEY. AS ANOMALOUS
SERLY LL JET SWEEPS NORTHEAST AND ENCOUNTERS LL COLD AIR OVR
PA...MIXED PRECIP SHOULD BRK OUT LATER THIS MORNING AND AFTN. 

ALTHOUGH SREF PTYPE PROBS SUGGEST FZRA CHANGING TO RAIN OVR MUCH
OF THE AREA...CAN/T RULE OUT SOME SNOW/SLEET BASED ON MODEL
SOUNDINGS...WHICH SHOW WET BULB PROFILES AOB 0C FROM THE GROUND
UP. AM NOT MENTIONING SNOWFALL ACCUMS ATTM. HOWEVER...EVAP COOLING
OR ENHANCED PRECIP RTS COULD POTENTIALLY COOL THERMAL PROFILES
ENOUGH TO PRODUCE A QUICK COUPLE INCHES OF ACCUM IN SPOTS. 

WILL KEEP WINTER WEATHER ADVISORY IN EFFECT FOR ALL AREAS INTO THE
AFTN HOURS. REGIONAL RADAR LOOP AND LATEST RUC13 SUGGEST PRECIP
ARRIVAL TIME WILL RANGE FROM ARND 12Z OVR SOMERSET CO...TO MID
AFTN OVR THE MTNS N OF IPT. ALL MODEL DATA SUPPORTS ERODING LL
COLD AIR AND A CHANGEOVER TO RAIN BY LATE TDY...AS LL JET AND
ASSOCIATED STG WAA OVERSPREADS THE AREA. HAVE USED WWD ICE ACCUMS
OF A TENTH OF AN INCH OR LESS. 

OF OTHER CONCERN IS POTENTIAL OF STRONG WIND GUSTS OVR THE
ALLEGHENY MTNS WITH PASSAGE OF LL JET. WIND GUSTS OVR 40KT CURRENTLY
NOTED OVR PARTS OF WEST VIRGINIA...AND SIMILAR GUST SEEM POSSIBLE
OVR THE LAUREL HIGHLANDS LATER TDY AS 60-70KT LL JET SHIFTS NORTH.
WILL HOLD OFF ON A WIND ADVISORY FOR NOW BASED ON LATEST BUFKIT
DATA. HOWEVER...ONE MAY BE NEEDED LATER TDY OVR SOMERSET/CAMBRIA
COUNTIES.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH SATURDAY NIGHT/...
SECONDARY LOW DEVLPMNT SOUTH OF PA...AND ASSOCIATED EASTERLY
LLJ...WILL KEEP THE RAIN GOING INTO SAT. HOWEVER...RAIN SHOULD
TAPER OFF LATE IN THE DAY ACROSS THE WEST...AS OCCLD FNTL BNDRY
PIVOTS NEWD. TEMPERATURES OVR SERN PENN MAY APPROACH 50F IN THE
WARM SECTOR SAT...BEFORE TEMPS DROP BEHIND THE OCCLD FNTL PASSAGE.
MANUAL 36HR GRIDDED QPF SHOWS MUCH OF THE AREA PICKING UP
1.00-1.50 INCH RNFL AMNTS THRU 00Z SUNDAY. THIS...ALONG WITH SNOW
MELT WILL CAUSE MINOR TO MODERATE RISES IN THE WEST BRANCH AND
LOWER SUSQ BASINS...AND MAY PUSH SOME SMALLER TRIBS TO CAUTIONS
STAGE. HYDRO FCSTS FROM THE MARFC DO NOT INDICATE ANY FLOODING
ATTM AND GIVEN THAT ANY PROBLEMS WOULD LKLY NOT OCCUR FOR ANOTHER
36HRS...DECIDED AGAINST A FLOOD WATCH...BUT WL MENTION SOME
SPECIFICS IN HWO AND HYDRO SECTION BELOW.

COLDER AIR WILL BEGIN TO MIX WITH/CHANGE ANY LINGERING RAIN
SHOWERS TO SNOW SHOWERS LATE SAT AND SAT NGT WITH LITTLE OR NO
ACCUMS XPCD.

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
COLD MID LVL VORT WILL WOBBLE E ACROSS THE OH VLY AND INTO THE
MID ATLC REGION SUN/MON. BRISK/WINDY CONDS AND LES SHWRS WILL
ACCOMPANY A REINFORCING SURGE OF COLDER AIR MON NGT/TUE. HIGH PRES
SHOULD BRING SOME IMPROVEMENT BY THE MIDDLE OF NEXT WEEK.

STRONG NEG AO/NAO...+ PNA AND A SRN STREAM EL NINO CONNECTION
WL CONT TO OFFER A SET UP FAVORABLE FOR EAST COAST WINTER STORMS.
GFS/ECMWF MEAN SHOW A STORM SYSTEM ORGANIZED ALONG THE ECOAST
AROUND THE NEW YEAR...STAY TUNED.

&&

.AVIATION /12Z FRIDAY THROUGH TUESDAY/...
POTENT UPPER LOW CENTERED TO OUR WEST WITH SURFACE WAVE SLIDING UP
APPALACHIANS WILL BRING DETERIORATING CONDITIONS TO CENTRAL PA
THROUGH SAT. SE LLVL FLOW WILL BRING MOISTURE WHICH WILL LOWER
CIGS TO MVFR THIS MORNING AS PRECIP BEGINS TO ARRIVE BY 15Z. AT
THAT TIME...CIGS WILL LOWER TO IFR/LIFR WITH VSBY BETWEEN 2-5SM.
PRECIP TYPE WILL BE FZRA FROM ONSET TO MID AFTERNOON...SO ICING
THREAT IS VERY HIGH. AROUND 21Z TEMPS WILL WARM ABOVE FREEZING AND
PRECIP TYPE WILL TRANSITION TO PLAIN RAIN...BUT IFR/LIFR CONDITIONS
WILL PERSIST THROUGH FRI NIGHT INTO SAT. IN ADDITION TO THE POOR
FLYING CONDS...A VIGOROUS LLVL JET WILL BRING WINDS OFF THE DECK
AT 1500FT AGL AOA 40-50KTS SO HAVE MENTIONED WIND SHEAR THRU EARLY
SAT.

OUTLOOK...
FRI NGT...IFR TEMPO LIFR CIGS WITH STEADY RA. WS OF 40-50KTS AOA
1500FT AGL. 
SAT...IFR CONDS...SLT IMPROV TO MVFR CENTRAL/EAST. WS WILL RELAX.
SUN-TUE...MVFR CIGS W/IFR WEST IN SHSN. CNTRL/EAST VFR/MVFR.

&&

.HYDROLOGY...
GENERALLY MINOR CHANGES IN RIVER LEVELS ARE EXPECTED OVER THE
NEXT 24 HOURS...WITH A RISE OF UP TO SEVERAL FEET EXPECTED LATER
IN THE PERIOD. WILLIAMSPORT IS FCST TO APPROACH CAUTION STATE
SUN/MON.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY FROM 10 AM THIS MORNING TO 7 PM EST 
THIS EVENING FOR PAZ037-041-042.
WINTER WEATHER ADVISORY UNTIL 5 PM EST THIS AFTERNOON FOR 
PAZ004>006-010>012-017>019-024>028-033>036-045-049-050-056>059-
063>066.
WINTER WEATHER ADVISORY FROM 10 AM THIS MORNING TO 5 PM EST 
THIS AFTERNOON FOR PAZ046-051>053.

&&

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