Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 220942 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 542 AM EDT TUE APR 22 2014 .SYNOPSIS...
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A STRONG COLD FRONT STRETCHING FROM DETROIT TO INDIANAPOLIS AT DAYBREAK TODAY...WILL PUSH EAST ACROSS THE STATE THIS AFTERNOON AND EARLY THIS EVENING...PRODUCING OCCASIONAL SHOWERS AND POSSIBLY A FEW ISOLATED THUNDERSTORMS. MUCH COLDER AIR WILL WORK INTO THE COMMONWEALTH TONIGHT AND WEDNESDAY...WITH LAKE EFFECT SNOW SHOWERS OVER THE NORTHWEST AND WEST CENTRAL MOUNTAINS AND FLURRIES POSSIBLE OVER THE REST OF THE CENTRAL AND NORTHERN MOUNTAINS. COOL AND DRY WEATHER IS EXPECTED TO CONTINUE THURSDAY...AS A RIDGE OF HIGH PRESSURE SLIDES OVER THE AREA. THE NEXT COLD FRONT AND CHANCE FOR SHOWERS WILL ARRIVE ON FRIDAY.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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A RIBBON OF ANOMALOUSLY HIGH PWAT AIR /AROUND 1.00 INCH/ WILL SLIDE INTO WESTERN PENN THIS MORNING...THEN SHIFT INTO THE EASTERN HALF OF THE STATE BY 18Z...BEFORE EXITING FAR EASTERN PENN AROUND 00Z WED. THIS PLUME OF MOISTURE WILL INTERACT WITH AN APPROACHING COLD FRONT TO BRING A HIGH PROBABILITY OF SHOWERS TODAY. ALTHOUGH THE PROBABILITY FOR MEASURABLE RAIN IN THE 12Z TUE-00Z WED PERIOD WILL BE 90-100 PERCENT...THE AMOUNT OF RAINFALL WILL BE GENERALLY LIGHT AND AOB 0.25. SFC AND MIXED LAYER CAPE WILL ALSO BE QUITE MEAGER AND ONLY A FEW TO SVRL HUNDRED J/KG...THANKS TO WIDESPREAD AND FAIRLY THICK MID LEVEL CLOUD COVER PRECEDING THE COLD FRONT. THEREFORE...ANY THUNDERSTORMS SHOULD BE SHORT IN STATURE... ISOLATED...AND SHORT-LIVED. THE TIMING OF THE CFROPA SHOULD BE ABOUT 14-16Z ACROSS THE NW MTNS 18-21Z THROUGHOUT THE CENTRAL RIDGE AND VALLEY REGION OF PA...AND ABOUT 22-23Z IN THE FAR SE ZONES. HIGHS TODAY WILL OCCUR DURING THE MID TO LATE MORNING ACROSS THE NW HALF OF THE CWA...AND DURING THE EARLY AFTERNOON IN THE SUSQ VALLEY. THE MAX TEMPS WILL RANGE FROM THE MID 50S IN THE NORTHWEST TO AROUND 70F ACROSS THE SOUTHEAST.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM WEDNESDAY/...
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MUCH COLDER AIR DIVES INTO WEST CENTRAL PA BY 00Z WED...WITH 850 MB READINGS PLUNGING BELOW ZERO. FRONTAL RAIN SHOWERS SHOULD EXIT THE ERN 1/3 OF THE CWA LATE THIS EVENING. GUSTY POST-FRONTAL WNW FLOW WILL INCREASE THROUGH WEDNESDAY AND HELP DIRECT AN ABNORMALLY COOL CANADIAN AIRMASS INTO THE AREA FOR THE MIDDLE OF THE WEEK. THE WELL ALIGNED NW FLOW WILL COMBINE WITH 850 MB TEMPS FALLING TO AROUND -3 TO -4C TONIGHT TO BRING SCATTERED SNOW SHOWERS TO THE NW MTNS AND LAURELS OVERNIGHT TONIGHT...WITH A LIGHT COATING POSSIBLE AT ELEVATIONS GENERALLY AOA 1500 FT MSL. A FEW FLURRIES WILL LIKELY SPILL OFF THE ALLEGHENY FRONT AND INTO THE CENTRAL RIDGE AND VALLEY REGION AFTER MIDNIGHT TONIGHT. LOW TEMPS TONIGHT WILL VARY FROM THE LOWER TO MID 30S ACROSS THE MOUNTAINS...TO BETWEEN 40-45F THROUGHOUT THE SUSQ VALLEY. PLENTY OF CLOUDS WILL LINGER ACROSS THE NRN AND WESTERN MTNS FOR WEDNESDAY WITH SCATTERED MAINLY MORNING SNOW SHOWERS /MIXED WITH RAIN IN THE VALLEYS/...WHILE MOSTLY SUNNY SKIES DEVELOP ACROSS THE LOWER SUSQ VALLEY. VRBL AMOUNTS OF STRATO CU WILL OCCUR ACROSS THE CENTRAL RIDGE AND VALLEY REGION. HIGH TEMPS ON WEDNESDAY /IN THE MID AND UPPER 40S ACROSS THE NW MTNS AND LAURELS...AND UPPER 50S IN THE SE/ WILL AVG 5-10 DEGREES BELOW NORMAL.
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&& .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
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SFC LOW WILL DEEPEN INTO THE CANADIAN MARITIMES THROUGH DAY 3/WED...AS THE PARENT UPPER LEVEL TROUGH AMPLIFIES SEWD ACROSS THE NORTHEASTERN CONUS AND EVENTUALLY CLOSES-OFF NEAR THE GULF OF MAINE/SOUTH OF NOVA SCOTIA BY 12Z THURS. THIS SHOULD MARK THE BEGINNING OF A LARGER SCALE PATTERN TRANSITION FROM MODERATELY PROGRESSIVE TO A BLOCKY/SLOWER-EVOLVING REGIME BY THE WEEKEND AND INTO EARLY NEXT WEEK. SFC HIGH PRES RIDGE AXIS WILL CROSS THE AREA ON THURSDAY. AT THIS TIME IT APPEARS THAT THERE WILL BE ENOUGH OF A PRES GRADIENT AND NW WIND TO PREVENT FROST/FREEZE HEADLINES FOR THE LOWER SUSQ. VALLEY THURSDAY MORNING. TEMPS WILL GRADUALLY REBOUND DURING THE DAY THURSDAY. THERE IS DECENT MODEL/ENSEMBLE AGREEMENT IN A SHORTWAVE TROUGH AND SFC LOW PRESSURE TRACKING THROUGH THE GREAT LAKES REGION BY THE END OF THE WEEK...WITH THE NEXT COLD FRONT FCST TO ARRIVE ON FRIDAY ACCOMPANIED BY THE CHC FOR SHOWERS. THERE IS INCREASING SPREAD IN THE GUIDANCE FOR THE WEEKEND AND INTO EARLY NEXT WEEK WITH HINTS OF A REX BLOCK DEVELOPING OVER THE CENTRAL NOAM AND MEAN TROUGH LINGERING OVER SERN CANADA AND PERHAPS THE NERN US. THE 21/12Z GFS ARE STRONGLY IN FAVOR OF THIS EVOLUTION WHILE THE 21/00Z ECMWF AND 21/12Z GEFS ARE NOT QUITE AS AMPLIFIED WITH TROUGHING OVER SERN CANADA/NERN US. DUE TO THE VARIABILITY IN THE GUIDANCE...OPTED FOR A CONSENSUS BLEND FOR MAX/MIN/POP WHICH RESULTED IN NEAR NORMAL TEMPS AND RELATIVELY LOW PROBS FOR RAIN.
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&& .AVIATION /09Z TUESDAY THROUGH SATURDAY/... A WEAKENING RIDGE ALOFT WILL CONTINUE TO BRING VFR CONDITIONS THROUGH THE PREDAWN HOURS...WITH THICKENING/LOWERING MID LEVEL CLOUDS. FOR THE DAYLIGHT HOURS TODAY...A SHORT WAVE AND ASSOCIATED COLD FRONT WILL BRING RAIN SHOWERS TO PENNSYLVANIA...STARTING IN THE NW BY 12Z. EXPECT MVFR CIGS AND VSBYS TO PERSIST THROUGH AROUND 21ZZ. ENOUGH CAPE THAT THERE MAY BE AN ISOLATED TSTORM IN THE SUSQ VALLEY LATER IN THE DAY...BUT CHANCE TOO LOW AT SPECIFIC POINTS TO MENTION IN TAFS ATTM. BREEZY NW WINDS WILL DEVELOP THIS AFTERNOON...AND CONTINUE INTO WED WITH WIND GUSTS UPWARDS OF 25 MPH LIKELY. MVFR CIGS WILL RETURN TO MAINLY THE WESTERN/NORTHERN HIGHER ELEVATIONS STARTING MID EVE BEHIND FRONT...WHILE DOWNSLOPE FLOW KEEPS REMAINDER OF AREA VFR. OUTLOOK... TONIGHT-WED...MVFR NORTH/WEST WITH SCT -SHRA...VFR ELSEWHERE. BREEZY NW WINDS. THU...VFR. NO SIG WX. FRI...MVFR WITH CHC SHRA. SAT...MVFR WITH CHC SHRA && .CTP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...LAMBERT NEAR TERM...LAMBERT SHORT TERM...LAMBERT LONG TERM...LAMBERT/STEINBUGL AVIATION...RXR

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