Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 270139 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 939 PM EDT SUN APR 26 2015 .SYNOPSIS... A SLOW MOVING UPPER LEVEL LOW OVER THE NORTHEASTERN UNITED STATES AND COOL AIR ALOFT WILL FAVOR UNSEASONABLY CHILLY TEMPERATURES WITH PERIODS OF SHOWERY WEATHER THROUGH THE END OF THIS MONTH. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/... A SPRAWLING UPPER LOW OVER THE CANADIAN MARITIMES WILL CONTROL THE PATTERN FOR THE NEXT COUPLE OF DAYS AT LEAST. THE MAIN EFFECT WILL TO FUNNEL A SERIES OF UPPER SHORTWAVES DOWN OUT OF NEW YORK/EASTERN CANADA AND KEEP A FAIR AMOUNT OF CLOUDINESS AND THE CHANCE FOR SHOWERS IN THE FORECAST. EVENING IR IMAGERY SHOWING EXPANSIVE STRATOCU DECK ASSOC WITH UPPER LOW EXTENDING FROM ONTARIO/QUEBEC INTO NORTHERN PA. FURTHER SOUTH...SCT DIURNAL CU ACROSS CENTRAL/SOUTHERN PA HAVE LARGELY COLLAPSED WITH LOSS OF HEATING LATE THIS EVENING. LOW LVL INSTABILITY BENEATH UPPER LOW WILL LIKELY SUSTAIN MCLDY SKIES ACROSS THE N MTNS OVERNIGHT. HOWEVER...SUBTLE UPPER LVL RIDGING BTWN SHORTWAVES AND COOLING BLYR SHOULD KEEP THE NORTHERN MTNS DRY FOR NEARLY THE ENTIRE NIGHT. HAVE INTRODUCED CHC OF SHSNRA TOWARD DAWN ACROSS THE NW MTNS UPON APPROACH OF NEXT SHORTWAVE DIVING SOUTH ACROSS LK ERIE. LOWS WILL RANGE FROM AROUND FREEZING OVER THE NW TO AROUND 40 IN THE SE. && .SHORT TERM /6 AM MONDAY MORNING THROUGH 6 PM MONDAY/... MODELS AGREE IN TRACKING A RELATIVELY SHARP SHORTWAVE SOUTHWARD ACROSS WESTERN PA MONDAY. GEFS/SREF QPF FIELDS SUPPORT THE HIGHEST /LIKELY/ POPS ACROSS THE ALLEGHENY PLATEAU...IN LINE WITH TRACK OF SHORTWAVE AND BEST LG SCALE FORCING. HOWEVER...INCREASING LAPSE RTS ASSOC WITH POOL OF COLD AIR ALOFT SHOULD PROMOTE ABUNDANT CLOUD COVER BY EVERYWHERE AFTN W/SCT -SHRA EVEN ACROSS EASTERN PA. MDL SOUNDINGS REMAIN MARGINALLY COLD ENOUGH FOR SNOW MON AM ACROSS THE NW MTNS...SO HAVE MIXED RAIN/SNOW SHOWERS MENTIONED UP THERE THRU ARND 14Z. LOW PWATS SHOULD TRANSLATE TO ONLY VERY LIGHT RAINFALL AMTS MONDAY...ON THE ORDER OF A FEW HUNDRETHS AT BEST. ENS MEAN 8H TEMPS ARND -1C SHOULD TRANSLATE TO HIGHS FROM THE M40S OVR THE HIGH TERRAIN OF THE ALLEGHENIES...TO THE U50S ACROSS THE SUSQ VALLEY. && .LONG TERM /MONDAY NIGHT THROUGH SUNDAY/... ACTIVE NORTHERN AND SOUTHERN STREAM SPLIT FLOW PATTERN ACROSS NORTH AMERICA WILL KEEP THE REGION IN UPPER LEVEL TROFFINESS THROUGH MUCH OF THE COMING WEEK. THIS WILL SUPPORT COOLER THAN NORMAL...SHOWERY WEATHER. UPPER LEVEL RIDGING WILL MOVE EAST AND TRY TO PERSIST OVER THE EASTERN U.S. STARTING AROUND NEXT WEEKEND. EARLY THIS WEEK A SHOT OF COOL UNSETTLED WEATHER ARRIVES AS A BACK DOOR COLD FRONT IS NUDGED SOUTHWARD ACROSS PA FROM AN UPPER LOW OVR NEW ENG. COOL TEMPS ALOFT ASSOC WITH UPPER LOW WILL LIKELY LEAD TO A GOOD DEAL OF DAYTIME CLOUDINESS AND SCT SHRA /ESP OVR THE MTNS/ MONDAY AND TUESDAY. BY MIDWEEK...SLOW MOVING SRN STREAM UPPER LOW WILL EMERGE INTO THE SERN TO MID ATLC STATES...POSSIBLY PHASING WITH A NRN STREAM WAVE. AT THIS POINT SIGNIFICANT PCPN LOOKS TO STAY SOUTH OF PA...THOUGH THE HIEST POPS OF THE PERIOD WILL BE FROM THIS SYSTEM ON THURSDAY. REGARDLESS...THURSDAY LOOKS TO BE A CLOUDY AND COOL DAY ACROSS THE COMMONWEALTH. AFFECTS OF THIS UPPER LOW SHOULD DIMINISH THROUGH FRIDAY INTO SATURDAY AND WITH RISING HEIGHTS THE START OF NEXT WEEK LOOKS WARMER AND DRIER...AT THIS POINT. && .AVIATION /02Z MONDAY THROUGH FRIDAY/... NO CHANGES TO 00Z TAF PACKAGE FROM 21Z TAF PACKAGE. MADE SOME CHANGES TO THE PACKAGE AT 21Z. EARLIER DISCUSSION BELOW. LOOKING AT MAINLY VFR CONDITIONS TONIGHT AND MUCH OF THE WEEK. THIS BASED ON A FLOW OF DRY AIR FROM THE NORTH. HIGH BASE CU PREVAILED THIS AFT. THE EXCEPTION MAY BE BFD AND JST...WHICH WILL LIKELY SEE SOME MVFR AND EVEN IFR CIGS AT TIMES LATER TONIGHT INTO MONDAY...AS AN UPPER LEVEL TROUGH ROTATES ACROSS THE AREA. THESE LOWER CONDITIONS COULD PERSIST INTO AT LEAST EARLY TUE. A FEW SHOWERS WILL BE POSSIBLE ACROSS THE REGION MONDAY AND MONDAY NIGHT...GIVEN THE COLD AIR ALOFT. OUTLOOK... TUE...MAINLY VFR WITH SCT LIGHT RAIN SHOWERS. WED...NO SIG WX. THU-FRI...MVFR POSSIBLE IN SCATTERED RAIN SHOWERS. && .CTP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...LA CORTE NEAR TERM...FITZGERALD SHORT TERM...FITZGERALD/LA CORTE LONG TERM...LAMBERT/GARTNER AVIATION...MARTIN

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