Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 240715 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 215 AM EST WED DEC 24 2014 .SYNOPSIS... AN INTENSIFYING STORM SYSTEM WILL MOVE NORTHWARD FROM THE WESTERN GULF COAST TO THE CENTRAL GREAT LAKES BY THIS EVENING. THE ASSOCIATED COLD FRONT WILL PUSH THROUGH CENTRAL PENNSYLVANIA WEDNESDAY NIGHT. ANOTHER LESS POTENT COLD FRONT WILL MOVE ACROSS THE AREA THIS WEEKEND. && .NEAR TERM /UNTIL 8 AM THIS MORNING/... LARGE SHIELD OF RAIN CONTINUES TO ADVANCE QUICKLY TO THE NORTH ACROSS THE CWA EARLY TODAY. INCREASINGLY STRONG SOUTHERLY FLOW /PLUS 2-3 SIGMA AT 850 MB VIA THE LATEST SREF/ WILL ADVECT ABUNDANT MOISTURE INTO THE REGION TODAY IN THE FORM OF LIGHT TO MODERATE RAIN. PWATS INCREASING TO NEARLY PLUS 4 SIGMA /OR 1.25 TO 1.5 INCHES/ THIS MORNING WILL BRING WIDESPREAD 0.5 TO 0.75 INCH AMOUNTS OF RAIN ACROSS MOST OF CENTRAL AND ERN PENN BY LATE THIS MORNING. TEMPS FOR THE REST OF THE NIGHTTIME HOURS WILL NEARLY STEADY IN THE UPPER 30S TO LOW 40S. WINDS WILL BE GENERALLY LIGHT FROM THE EAST TO SOUTHEAST...BUT GUSTS AROUND 20 MPH WILL BE LIKELY ON THE HIGHER TERRAIN...AND INVOF KIPT WHERE CHANNELING EFFECTS OF THE EAST/WEST VALLEY WILL ACCENTUATE SPEEDS. LOW STRATUS WILL INTERSECT THE RIDGES SHROUDING THEM IN FOG THIS MORNING. && .SHORT TERM /8 AM THIS MORNING THROUGH 6 PM THURSDAY/... A RIBBON OF HIGHER DEEP LAYER MOISTURE WILL LIKELY BRING SOAKING RAINFALL TO CENTRAL PA EARLY IN THE DAY. BY AFTN...MDL DATA INDICATES THE RAIN SHOULD TAPER OFF AS DRY SLOT WORKS IN FROM THE SW. LATEST GUIDANCE CONTINUES TO TARGET THE LOWER SUSQ VALLEY FOR THE HEAVIEST RAIN...WITH 1+ INCH AMTS LIKELY BASED ON 21Z SREF AND BLEND OF EARLIER OPER RUNS. MUCH LIGHTER AMTS EXPECTED ACROSS THE NW MTNS. HI RES MODELS INDICATING A SQUALL LINE TO ACCOMPANY SFC COLD FRONT LAGGING THE UPPER FRONTAL PASSAGE WEDNESDAY 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. HAVE LOWERED DAYTIME TEMPS OVR MUCH OF THE AREA...BASED ON LATEST GUIDANCE WHICH INDICATES PERSISTENT COLD AIR DAMMING. THE WARMEST READINGS OVR MUCH OF THE AREA MAY NOT BE REACHED UNTIL AFTER DARK WED EVENING. && .LONG TERM /THURSDAY 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 /07Z WEDNESDAY THROUGH SUNDAY/... WIDESPREAD REDUCTIONS IN FOG AND LOW CIGS 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 AN 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...LAMBERT NEAR TERM...LAMBERT SHORT TERM...FITZGERALD/LAMBERT LONG TERM...MARTIN AVIATION...GARTNER

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