Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 240132 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 832 PM EST TUE DEC 23 2014 .SYNOPSIS... LOW PRESSURE OFF OF THE NEW JERSEY COAST THIS EVENING WILL WEAKEN AND MOVE TO CAPE COD TONIGHT. AN INTENSIFYING STORM SYSTEM WILL MOVE NORTHWARD FROM THE WESTERN GULF COAST TO THE CENTRAL GREAT LAKES BY WEDNESDAY EVENING...PUSHING A WARM FRONT NORTHWARD OVER THE COMMONWEALTH. THE LOW WILL THEN LIFT INTO ONTARIO AND QUEBEC LATE CHRISTMAS EVE...PUSHING A COLD FRONT THROUGH THE STATE BY EARLY CHRISTMAS MORNING. ANOTHER LESS POTENT COLD FRONT WILL MOVE ACROSS THE AREA THIS WEEKEND. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... DEEP SOUTHERLY FLOW IN ADVANCE OF TROUGH OVR THE PLAINS HAS DRAWN A PLUME OF GULF OF MEX MOISTURE OVER THE EASTERN CONUS. SATL-DERIVED PWAT IMAGERY AS OF THIS EVENING IS SHOWING ANOMALOUS DEEP LYR MOISTURE VALUES ACROSS THE ENTIRE E COAST. FOR THIS EVENING...WEAK FORCING IN THE FORM OF OROGRAPHIC LIFT WILL PRODUCE NO MORE THAN DRIZZLE OVR MOST OF CENTRAL PA. HOWEVER...REGIONAL RADAR LOOP AT 23Z SHOWS A LARGE AREA OF RAIN LIFTING NORTH TOWARD PA IN ASSOC WITH LL JET AHEAD OF DEVELOPING SFC LOW ON THE GULF COAST. AS LL JET FEATURE LIFTS NORTH...EXPECT A STEADY RAIN TO OVERSPREAD THE REGION FROM THE SOUTH LATE TONIGHT. BLEND OF HRRR...RAP AND 18Z GEFS/NAM SUGGEST THE STEADY RAIN WILL REACH THE LAUREL HIGHLANDS/SC MTNS ARND MIDNIGHT AND THE REST OF THE AREA BY ARND 09Z. A CALM WIND HAS PROMOTED WIDESPREAD FOG THIS EVENING. HOWEVER...AS A SERLY BREEZE DEVELOPS LATE TONIGHT...EXPECT THE FOCUS OF THE FOG TO BE ON THE RIDGES...WITH IMPROVING VSBYS ACROSS THE SUSQ VALLEY. TEMPS EXPECTED TO REMAIN NEARLY STEADY OVERNIGHT...AVERAGING IN THE L40S MOST PLACES. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/... A RIBBON OF HIGHER DEEP LAYER MOISTURE WILL LIKELY BRING SOAKING RAINFALL TO SOUTHEAST PA...GENERALLY ONE TO TWO INCHES...BEFORE WARM SECTOR AND DRY SLOT ARRIVE WEDNESDAY AFTERNOON. HI RES MODELS INDICATING A SQUALL LINE TO ACCOMPANY SFC COLD FRONT LAGGING THE UPPER FRONTAL PASSAGE LATE WEDNESDAY AFTERNOON AND EVENING. EXTENT OF SURFACE DESTABILIZATION WILL ULTIMATELY DETERMINE HOW STRONG THIS SQUALL LINE CAN GET...AND HOW STRONG WIND GUSTS CAN BE AT THE SURFACE...BUT SUFFICE TO SAY ONE OF THE BETTER SEVERE WEATHER SETUPS FOR CHRISTMAS EVE IS IN STORE FROM EARLY WED EVENING THROUGH JUST PAST MIDNIGHT ACROSS CENTRAL PA. AS PREVIOUSLY MENTIONED...EVEN MINIMAL CAPE COMBINED WITH STRONG /DEEP- LAYER WIND FIELDS A FEW TO SVRL KFT AGL OFTEN RESULTS IN A NCFRB WITH LOCALIZED DOWNBURST DAMAGE OCCURRING BENEATH MINI BOWS IN THE LINE. SPC HAS PLACED MUCH OF CENTRAL PA IN MARGINAL CATEGORY FOR DAY 2 AS A RESULT. MORE DETAILS BELOW. TEMPERATURES WILL CLIMB INTO THE 50S WED AFTERNOON INTO WED NIGHT...AS STRONGER SOUTHERLY WINDS DEVELOP. WARMEST TEMPS MAY BE ACROSS THE FAR WEST. && .LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/... ANOMALOUSLY STRONG SSWRLY UPPER JET OF 140-150 KTS WILL ACCOMPANY THE CFROPA IN THE 04-10Z TIME PERIOD CHRISTMAS DAY. IN ADDITION...THE UNSEASONABLY WARM AND MOIST AIR WILL HELP TO PRODUCE A RIBBON OF CAPE UP TO A FEW HUNDRED J/KG. FOR NOW...HAVE CHC OF THUNDER IN FOR WED EVENING. NORMALLY I WOULD BE MORE CONCERN ABOUT STRONG TO SEVERE STORMS...BUT BEST FORCING ACROSS THE OH VLY. ALSO TIME OF DAY NOT THE BEST. HOWEVER...HINTS OF COLD AIR DAMMING STILL ACROSS CENTRAL ZONES. EITHER WAY...NORMALLY LIKE TO SEE DEWPTS IN THE UPPER 50S. STILL EXPECT SOME GUSTY WINDS LATE WED NIGHT INTO THU AM...MOST LIKELY WILL NEED A WIND ADVISORY...BUT STILL THIRD PERIOD. TOOK SNOW OUT OF FCST FOR CHRISTMAS...TEMPS NOT COLD ENOUGH. FRIDAY LOOKS NICE...WITH SW FLOW. DID UP TEMPS FRIDAY INTO SAT...GIVEN RISING HEIGHTS. CUT BACK PCPN FOR LATE FRIDAY. 12Z EC RUN HAS SYSTEM FURTHER NW NOW...BUT FOR NOW WENT WITH SLIGHT CHC OF SNOW FROM SUNDAY INTO EARLY MONDAY MORNING. AGAIN WITH SPLIT FLOW...THERE COULD BE SOME CHANCE FOR A SOUTHERN WAVE TO BRING SOME RAIN OR SNOW SHOWERS TO THE AREA AT TIMES...BUT IT LOOKS LIKE ANYTHING WOULD BE FAST MOVING. PERHAPS A CHANGE LATER NEXT WEEK...AS CROSS POLAR FLOW SETS UP. && .AVIATION /01Z WEDNESDAY THROUGH SUNDAY/... WIDESPREAD REDUCTIONS WILL CONTINUE OVERNIGHT WITH ENTIRE CWA REMAINING AT IFR/LIFR AS LOW LEVEL MOISTURE FEEDS IN FROM THE SE FROM A WEAK SFC LOW EAST IF NEW JERSEY COAST...THEN MAINTAINED AHEAD OF SRLY FLOW OF APPROACHING FRONTAL SYSTEM. INCLUDED LLWS FOR ALL TAF SITES STARTING NEAR SUNRISE WED MORNING AS WINDS ALOFT BEING TO INCREASE AHEAD OFF APPROACHING FRONTAL SYSTEM OVER THE MIDWEST WHILE SFC WINDS REMAIN SERLY. OUTLOOK... WED...PERIODS OF RAIN ALONG WITH WIDESPREAD REDUCTIONS. SLGT CHC TSTM NW. BREEZY. LLWS LIKELY. THU...WINDY AND COLDER WITH SCT MVFR CIGS AND -SHSN. LLWS. FRI...FAIR AND MOSTLY VFR. SAT...FAIR AND MOSTLY VFR. SCT SHSN WITH LOCAL REDUCTIONS NW. SUN...MVFR TO IFR WITH CHC RA/SN...ESP SOUTH. && .CTP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...DEVOIR/MARTIN NEAR TERM...FITZGERALD SHORT TERM...DEVOIR/MARTIN LONG TERM...MARTIN AVIATION...GARTNER

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