Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 262004 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 404 PM EDT THU MAR 26 2015 .SYNOPSIS... SHOWERS AND ISOLATED THUNDERSTORMS WILL OCCUR AHEAD OF A STRONG COLD FRONTAL SYSTEM THIS EVENING. A LARGE HIGH PRESSURE SYSTEM WITH COLD AIR WILL DOMINATE OUR REGION INTO THE WEEKEND. THE UPPER LEVEL FLOW BECOMES MORE ZONAL NEXT WEEK SO TEMPERATURES SHOULD REBOUND TOWARD NORMAL. && .NEAR TERM /UNTIL 10 PM THIS EVENING/... THE TONGUE OF WARM AIR HAS PUSHED 60F READINGS WELL INTO CENTRAL PENNSYLVANIA WHILE COLD AIR REMAINS ENTRENCHED ALONG THE NY BORDER WHERE IT IS STILL IN THE 30S. SNOW IS OCCURRING NOT TOO FAR TO THE NORTH AND WEST. THE MODELS AND RADAR INDICATED SHOWERS AND ISOLATE THUNDERSTORMS WILL MOVE ACROSS THE STATE TODAY. BEST CHANCE OF THUNDER IN THE WARM AIR FROM CENTRAL PA TO THE SOUTHEAST. THE HRRR CONTINUES TO SHOW A CONVECTIVE LINE DEVELOPING IN CENTRAL PA IN THE 3-4 PM TIME FRAME THEN THIS LINE MOVING EASTWARD CLEARING LANCASTER COUNTY BY 7-8 PM. THERE IS A CHANCE OF THUNDER OVER SOUTHEASTERN PA THIS EVENING. TOTAL QPF IS RELATIVELY LIGHT IN THE 0.05 TO 0.25 RANGE WITH HINTS OF PERHAPS 0.25 TO 0.40 INCHES IN MORE INTENSE SHOWERS. ENSEMBLE GUIDANCE IMPLIES RELATIVE TO HRRR/RAP IS ABOUT 0.10 TO 0.20 INCHES. NOT A BIG EVENT. MOST AREAS WILL LIKELY BE LUCKY TO SEE ABOUT 0.10. POPS DROP BEHIND THIS LINE AND THIS EVENING COLD AIR TURNS ANY SHOWERS TO SNOW IN THE NORTHWEST. ALL NORTHERN AND WESTERN MOUNTAIN AREAS SHOULD BE SNOW BY 10 PM. SNOW CHANGE OVER IS SLOWER TO EAST AND IN NEXT PERIOD AND AFTER THE BULK OF THE FORECAST QPF. && .SHORT TERM /10 PM THIS EVENING THROUGH 6 PM FRIDAY/... . THE COLD AIR AND GUSTY WINDS PUSH ACROSS OUR ENTIRE REGION THIS OVERNIGHT. SOME PATCHY FOG IN SOUTHEAST. ANY RESIDUAL SHOWERS WILL TURN TO SNOW SHOWERS OR FLURRIES. BEST CHANCE OF A DUSTING OR LIGHT SNOW ACCUMULATIONS WOULD BE OVERNIGHT IN NORTHWESTERN AREAS. BY MIDNIGHT TEMPERATURES WILL RANGE 40S IN SOUTHEAST TO AROUND 30 IN NORTHWEST. SOME SNOW SHOWER ACTIVITY POSSIBLE IN THE WEST FRIDAY. MORNING LOWS MAINLY UPPER 20S IN NORTH TO LOW TO MID 30S IN SOUTHEAST. STRONG COLD ADVECTION AND 850 HPA TEMPERATURES FORECAST TO FALL WELL BELOW LATE FRIDAY INTO FRIDAY NIGHT...WILL BE UNSEASONABLY COLD DAY FOR LATE MARCH. TEMPERATURES JUST ABOVE FREEZING IN MOUNTAINS TO MID 40S IN LOWER SUSQUEHANNA VALLEY. THE COLDEST AIR AT 850 HPA WITH -2 TO -2.5 STANDARD DEVIATION ANOMALIES COMES BY FRIDAY EVENING INTO SATURDAY. && .LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/... UPPER TROF DEEPENING OVER THE EASTERN U.S. AT THE START OF THE PERIOD WILL AFFECT THE WEATHER THROUGH AT LEAST THE EARLY PART OF THE WEEKEND. SIGNIFICANT PRECIPITATION ASSOCIATED WITH THIS TROF SHOULD HAVE CONCLUDED BY DAYTIME FRIDAY...BUT SEVERAL SHORTWAVES ROTATING AROUND THE UPPER TROF WILL SLOW THE ADVANCE OF THE OTHERWISE PROGRESSIVE TROF/ASSOCIATED SFC LOW...CAUSING LINGERING SHOWERS INTO SATURDAY. AREA OF HIGH PRESSURE SHOULD EVENTUALLY MOVE INTO THE REGION FOR SUNDAY INTO EARLY NEXT WEEK. BEHIND THE DEEP UPPER TROF WILL BRING ANOTHER SHOT UNSEASONABLY COLD AIR INTO THE REGION...ESPECIALLY NOTICEABLE AFTER A COUPLE DAYS OF MORE SPRING LIKE CONDS TODAY. TEMPERATURES WILL BE 10 TO 20 DEGREES BELOW NORMAL OVER THE WEEKEND. A COMPARATIVELY WEAKER NRN STREAM WAVE WILL MOVE ACROSS THE UPPER GREAT LAKES REGION AND TOWARDS THE NORTHEAST ON MONDAY. THIS WILL CONTINUE THE CHILLY TEMPS AS WELL AS BRING THE CHANCE FOR MORE SNOW SHOWERS. WEATHER WILL DRY OUT BUT REMAIN COOL FOR THE MIDDLE OF NEXT WEEK AS ANOTHER AREA OF HIGH PRESSURE ARRIVES BEHIND FRONT. && .AVIATION /20Z THURSDAY THROUGH TUESDAY/... KEY ISSUE OVER THE NEXT 24 HOURS IS THE TIMING OF THE FRONT AND THE FRONTAL RAIN AND ISOLATED THUNDERSTORMS. THERE WILL ALSO BE SOME ISSUES WITH RAIN TO SNOW IN NORTHWESTERN PA THIS EVENING. THE BEST CHANCE FOR MODEST THUNDERSTORMS IS INT THE 20Z TO 00Z TIMEFRAME MAINLY IN CENTRAL AND SOUTHEASTERN AREAS. THERE COULD BE A WEAK LINE OF SHOWERS AND THUNDERSTORMS IN SOUTHEASTERN AREAS THIS EVENING. THE RAIN....SNOW....AND LINE OF SHOWERS WILL PRODUCE AREAS OF MVFR AND IFR. BEHIND THE FRONTAL SYSTEM MOISTURE COULD PRODUCE SOME AREAS OF PATCHY FOG AND AREAS OF SNOW SHOWERS IN THE NORTHWEST...AREAS OF IFR AND MVFR. THE COLD AIR COMES IN AND COULD CHANGE THE RAIN TO SNOW OVER THE ENTIRE REGION BY FRIDAY. MAINLY VFR AND SOME AREAS MVFR IN SNOW SHOWERS IN MOUNTAINS. FRIDAY WILL BE A MOSTLY VFR AREAS MVFR IN SNSH. WINDY DAY WITH SOME GUST SPREAD ISSUES. OUTLOOK... FRI-SAT...MVFR/IFR WITH SNOW SHOWERS NORTH/WEST. VFR TO MVFR CENTRAL AND EAST WITH SCHC OF -SHRA. SUN...NO SIG WX/VFR. MON...CHANCE OF LIGHT RAIN /LIGHT SNOW EARLY/ ACROSS NW HALF WITH MVFR REDUCTIONS. VFR SE. && .CTP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...GRUMM/LAMBERT NEAR TERM...GRUMM SHORT TERM...GRUMM LONG TERM...DEVOIR/GARTNER AVIATION...GRUMM

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