Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 230649 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 249 AM EDT WED JUL 23 2014 .SYNOPSIS... A COLD FRONT WILL PUSH SOUTHEAST ACROSS THE COMMONWEALTH LATE TODAY AND TONIGHT. A REFRESHING...COOLER AND LESS HUMID AIRMASS WILL OVERSPREAD THE COMMONWEALTH FOR THE END OF THE WEEK INTO THE WEEKEND. && .NEAR TERM /UNTIL 8 AM THIS MORNING/... WEAK RIDGING OVER THE REGION AT THE SURFACE AND ALOFT...COMBINED WITH VERY WARM MID LEVEL TEMPS OF 9-11C WILL KEEP CONDITIONS MAINLY CLEAR BUT MUGGY FOR THE REST OF THE OVERNIGHT HOURS. CURRENT DEWPOINTS IN THE MID TO UPPER 60S ARE A FEW DEG SHY OF THE EXPECTED MIN TEMPS AROUND SUNRISE. PATCHY LOW CLOUDS AND FOG WILL LIKELY FORM OVER THE NEXT FEW HOURS...BUT SHOULDN/T BE AS EXTENSIVE AS EARLY TUESDAY. A BKN LINE OF SHRA/TSRA SLIDING SE ACROSS THE PENNSINSULA OF SRN ONTARIO IS SHOWN TO WEAKEN AS IT CROSSES LAKE ERIE SHORTLY BEFORE DAYBREAK AND ENCOUNTERS THE VERY STRONG MID-LEVEL CAP ACROSS NWRN PENN. && .SHORT TERM /8 AM THIS MORNING THROUGH 6 PM TODAY/... A DRY START TO THE DAY WILL GIVE WAY TO INCREASING CHANCES FOR SHOWERS AND THUNDERSTORMS AS FORCING INCREASES ASSOCIATED WITH THE APPROACHING COLD FRONT. WE ARE NOT OUTLOOKED FOR SEVERE AT THIS TIME BUT THE AIRMASS CHANGE WILL BE FAIRLY STARK FOR MID JULY AND FORECAST CAPES IN EXCESS OF 1200J SUGGEST SPC MIGHT EXPAND THEIR SLIGHT RISK WITH LATER UPDATES. EITHER WAY IT LOOKS LIKE AN UNSETTLED AND WET DAY AS THE FRONT TRAVERSES THE REGION. THANKS TO A WARMING LOW LEVEL WSW DOWNSLOPE FLOW AHEAD OF THE CFRONT...HIGH TEMPS WED WILL BE THE WARMEST OF THE WEEK...RANGING FROM THE LOWER 80S ACROSS THE HIGHEST TERRAIN OF THE NORTH AND WEST...TO THE MID AND UPPER 80S IN THE CENTRAL VALLEY...AND LOWER 90S IN THE GREATER YORK/HARRISBURG AREA. && .LONG TERM /TONIGHT THROUGH TUESDAY/... OVERALL SCENARIO REMAINS UNCHANGED IN THE LONG TERM PERIOD AS A LARGE UPPER RIDGE BUILDING OVER THE FOUR CORNERS REGION IS FORECAST TO EXPAND NORTH AND EAST INTO THE ROCKIES AND PLAINS DURING THE PERIOD. DOWNSTREAM...THIS WILL LEAD TO LONG WAVE TROFFING OVER THE EASTERN THIRD OF THE COUNTRY. UPPER LOW TO THE EAST OF HUDSON BAY WILL BE STRENGTHENED AT TIMES BY SHORTWAVE ENERGY IN THE STRONGER JET STREAM FLOW ACROSS CANADA. SOUTHWARD EXTENSION OF THIS LOW/TROF WILL AT TIMES DURING THE PERIOD STRENGTHENING THE TROFFING ACROSS THE NORTHEASTERN U.S./OUR REGION. THE TREND OF MEDIUM RANGE MODEL GUIDANCE IS FOR STRONGER/DEEPER TROFFING DOWNSTREAM ACROSS THE EASTERN U.S...DEVELOPING AN ALMOST FULL LATITUDE TROF EXTENDING FROM THE EASTERN CANADA LOW SWD TO FLORIDA. THIS WILL LIKELY SERVE TO EXPAND AND PROLONG THE CHANCES FOR PCPN THIS WEEKEND. GUIDANCE FORECASTS CONTINUE TO BRING A FRONT AND INCREASED CHANGES FOR PRECIPITATION TOWARD PA IN THE WEDNESDAY/THURSDAY TIME FRAME AND SHOW A SECOND...POTENTIALLY STRONGER SYSTEM LATE NEXT WEEKEND. THE TREND OF STRONGER TROUGHING MENTIONED ABOVE HAS LEAD TO SLOWER ARRIVAL AND DEPARTURE OF THE FRONTAL SYSTEM IN THE DAILY PROGS. THE ECMWF IN LATEST RUN HAS SLOWED UP THE PROGRESSION OF THIS UPPER LEVEL LOW...WHERE THE GFS OPERATIONAL AND ENSEMBLES HAVE SPED UP ITS PROGRESSION THROUGH THE GREAT LAKES REGION. A WARM FRONT WILL BE ON THE DOORSTEP OF PA SUNDAY...AS THE EC CONTINUES TO SLOW ITS PROGRESSION SO EXPECT THE WARM FRONT TO MOVE IN CLOSER TO MIDDAY SUNDAY. HAVE THUS ADJUSTED POPS/TIME. ASSOCIATED COLD FRONT DOES NOT CROSS THE STATE TIL MONDAY...WHERE SURPRISINGLY AT THIS POINT...THE EC AND GFS COME CLOSELY IN PHASE. THIS LARGE UPPER LEVEL LOW COULD BECOME QUASI STATIONARY OVER SOUTHERN CANADA...GREAT LAKES REGION WHICH COULD LEAD TO A POTENTIAL PROLONGED PERIOD OF SHOWERS AND THUNDERSTORM THROUGH THE MIDDLE OF NEXT WEEK. && .AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
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23/06Z...CUT BACK ON FOG THIS MORNING GIVEN OBS TRENDS AND LGT S-SW GRADIENT SFC WIND IN ADVANCE OF COLD FRONT SEWD ACRS LWR MI TWD THE ERN LKS. LINE OF STORMS IN ADVANCE OF COLD FRONT MOVG ACRS LK ERIE ARE FCST BY COSPA/HRRR/SPC 4KM WRF TO WEAKEN OR DISSIPATE AS THEY REACH NW PA AROUND DAYBREAK. AFTER SOMEWHAT OF A LULL IN CONVECTION DURING THE MID TO LATE MORNING...EXPECT SCT TO NMRS SHWRS AND TSTMS TO DEVELOP FROM THIS AFTN INTO THE EVE ALONG AND AHEAD OF THE COLD FRONT..AS IT SHIFTS SEWD ACRS THE AIRSPACE. CVRG SHOULD BE GREATEST OVER THE CNTRL AND ERN PRTNS OF THE AIRSPACE WITH SOME STG TO LCLY SVR STORMS POSSIBLE. PREVAILING CONDS WILL VFR WITH BRIEF MVFR-IFR VIS REDUCTIONS IN TSRA IMPACTS. WND SHIFT FROM SW TO NW BY TONIGHT WITH MAIN PCPN ACTIVITY BCMG CONFINED TO SERN AREAS INTO THU. POST-FRONTAL MVFR SEEMS PROBABLE OVER WRN SXNS TNGT. OUTLOOK... THU...SCT TSTM IMPACTS PSBL SERN AIRFIELDS AS COLD FRONT SLOWS ALONG THE MID-ATLC COAST. FRI...PATCHY MORNING FOG...OTHERWISE VFR/NO SIG WX. SAT...PATCHY MORNING FOG...OTHERWISE VFR. ISOLD PM TSTM PSBL. SUN...TSTM IMPACTS LKLY AS WARM FRONT LIFTS NWD ACRS AIRSPACE.
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&& .CTP WATCHES/WARNINGS/ADVISORIES... NONE. && .CTP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...LA CORTE/LAMBERT NEAR TERM...DEVOIR/LAMBERT SHORT TERM...LA CORTE LONG TERM...LAMBERT/CERU AVIATION...STEINBUGL

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