FXUS61 KCTP 261529
AFDCTP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
1029 AM EST SAT DEC 26 2009
.SYNOPSIS...
LOW PRESSURE WILL TRACK NORTHWARD ACROSS EASTERN PENNSYLVANIA
TODAY. AN UPPER LEVEL LOW PRESSURE SYSTEM OVER THE MIDWEST WILL
TRACK EAST ACROSS PENNSYLVANIA BY MONDAY. HIGH PRESSURE WILL BUILD
OVER THE REGION AT MIDWEEK. HOWEVER...AN EAST COAST STORM COULD
POTENTIALLY THREATEN PENNSYLVANIA BY LATE NEXT WEEK.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
PLUME OF ANOMALOUS PWATS EXENDING FROM COASTAL NC TO CENTRAL PA
WITH SLOW MOVING N/S ORIENTED BANDS STREAMING NORTHWARD FROM DEL
MARVA REGION. SFC DEWPOINTS NEARING 50F ACROSS THE LOWER SUSQ.
NEAR THE MARYLAND BORDER AIDING IN EFFICICENT SNOWMELT.
COMBINATION OF PERSISTENT LIGHT RAIN AND SNOWMELT IS CAUSING SOME
MINOR PONDING AND FLOODING IN THAT AREA...WHERE A FLOOD ADVISORY
WILL REMAIN IN EFFECT FOR THE NEXT SEVERAL HOURS. SHERMANS CREEK
NOW EXPECTED TO CREST AROUND CAUTION STAGE AROUND MIDNIGHT...FOR
WHICH AN RVS WILL BE ISSUED SHORTLY.
ARRIVAL OF OCCLUDED FRONT WILL BRING AN END TO THE RAIN LATER
TDY FROM WEST TO EAST...BUT THIS WILL BE A SLOW PROCESS. STRONG LL
JET WORKING ACROSS EASTERN PA WILL CONTINUE TO CREATE GUSTY WINDS
NR THE SFC...ESP DOWNWIND /WEST/ OF THE RIDGETOPS. BUFKIT DATA
SUPPORTS GUSTS ARND 25KTS CONTINUING FOR MUCH OF THE DAY ACROSS
EASTERN PA.
MODEL SOUNDINGS SUGGEST JUST ENOUGH COLD AIR ON THE BACK EDGE OF
PRECIP SHIELD TO SUPPORT A BRIEF CHANGEOVER TO SNOW OVR THE N MTNS
LATER TDY. ANY ACCUMS SHOULD BE NEGLIGIBLE.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SUNDAY/...
DRY SLOT SHOULD WORK INTO THE AREA TONIGHT...BRINGING PARTIAL
CLEARING. STEEPENING LPS RTS AHEAD OF APPROACHING UPPER LO WILL
BRING AN INCREASING CHC OF SHSN ON SUNDAY. ENS MEAN QPF INDICATES LGT
ACCUMS OF LESS THAN AN INCH POSSIBLE BY SUN AFTN OVR THE NW MTNS
AND LAUREL HIGHLANDS. MODEL 900MB TEMPS SUGGEST HIGH TEMPS SUNDAY RANGING
FROM THE L30S NW MTNS TO M40S LOWER SUSQ VALLEY.
&&
.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
UPPER LOW WILL LIFT NORTHEAST ACROSS THE E GRT LKS SUNDAY NIGHT.
LG SCALE FORCING AHEAD OF THIS FEATURE WILL LIKELY SUPPORT A
PERIOD OF SNOW OVR THE ALLEGHENY MTNS SUNDAY NIGHT...WITH SHSN
POTENTIALLY EVEN SURVIVING DOWNWIND OF THE MTNS INTO THE SUSQ
VALLEY.
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. THIS 36-48 HOUR PERIOD WILL LIKELY
CONTAIN SEVERAL INCHES OF SNOW ACROSS THE SNOW BELT OF NW PA.
THE MOST TRANQUIL /THOUGH STILL COLD/ PERIOD NEXT WEEK WILL BE
TUESDAY NIGHT THROUGH WEDNESDAY NIGHT AS A LARGE AREA OF HIGH
PRESSURE BUILDS ENE FROM THE OHIO VALLEY.
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.
12Z GEFS...AND THE OPERATIONAL 06Z EC/ 12Z GFS STILL SHOW A
DEVELOPING AREA OF LOW PRESSURE MOVING NNE - SEVERAL HUNDRED KM
OFF THE SE AND MID ATLANTIC COAST TOWARD THE START OF THE NEXT
DECADE...STAY TUNED. FOR NOW...WILL BROAD-BRUSH A 30-40 PERCENT
CHC FOR SNOW NEW YEARS EVE INTO THE FIRST DAY OF 2010. 12Z
ECMWF...HAS SHOWN A TYPICAL WWD JOG TO THE PATH OF THE LOW - NOW
CLOSER TO THE MID ATLANTIC COAST...WITH A BETTER CHC FOR SNOW
ACROSS OUR CENTRAL AND ERN ZONES LATE NEW YEARS DAY INTO JAN 2ND.
&&
.AVIATION /16Z SATURDAY THROUGH WEDNESDAY/...
SFC LOW OVR SE VIRGINIA AT 12Z...IS PROGGED TO TRACK ACROSS EASTERN
PA LATER TDY KEEPING THE RAIN/DZ GOING /ALONG WITH PRIMARILY MVFR
CONDITIONS/ FOR THE MAJORITY OF THE DAY IN SUSQ VALLEY. ACROSS
WESTERN PA...ARRIVAL OF OCCLUDED FRONT WILL BRING AN END TO THE
RAIN EARLY THIS AFTERNOON /WITH A BRIEF CHANGOVER TO SNOW POSSIBLE
IN THE NW MTNS BEFORE ENDING/ AS CONDITIONS IMPROVE BACK TO VFR
AROUND 21Z. STRONG LL JET WORKING ACROSS EASTERN PA WILL CONTINUE
TO CREATE GUSTY WINDS NR THE SFC...ESP DOWNWIND /WEST/ OF THE
RIDGETOPS.
OUTLOOK...
SUN-TUE...NW FLOW. MVFR/IFR WEST WITH FREQ SNOW SHOWERS. CNTRL/EAST
VFR/MVFR WITH SCATTERED SNOW SHOWERS.
WED...VFR.
&&
.HYDROLOGY...
RIVER LVLS STARTING TO RESOPND TO THE RAIN AND SNOWMELT...WITH
LATEST MARFC GUIDANCE INDICATING MODEST RISES TO OCCUR OVER SOUTHEAST
PA...PARTICULARLY IN RESPONSE TO THE HIGHER DEWPOINTS WORKING UP
INTO THE REGION FROM MARYLAND AND DELAWARE. GEFS MEAN QPF RANGING
CLOSE TO 0.5 INCHES TDY OVR MUCH OF CENTRAL PA...WITH LOCALIZED
AMTS IN EXCESS OF 1 INCH OVR THE HIGH TERRAIN OF EASTERN PA STILL
LOOKING REASONABLE...GIVEN THE ANOMALOUS MOISTURE PLUME AND
POTENTIAL FOR TOPOGRAPHIC ENHANCEMENT. THAT SAID...6HR FFG BTWN 2
AND 3 INCHES SUGGEST SIG FLOOD THREAT REMAINS LOW. WILL CONTINUE
TO SEE MINOR FLOODING ISSUES IN POOR DRAINAGE AREAS OVER
ADAMS...YORK AND LANCASTER COUNTIES DUE TO COMBINED EFFECTS OF
RAIN AND SNOWMELT...BUT AT THE PRESENT TIME THIS WOULD APPEAR TO
REMAIN IN THE MINOR CATEGORY.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...FITZGERALD
NEAR TERM...DEVOIR/FITZGERALD
SHORT TERM...FITZGERALD
LONG TERM...FITZGERALD/LAMBERT
AVIATION...RXR
HYDROLOGY...DEVOIR
