Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 180849 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 449 AM EDT FRI APR 18 2014 .SYNOPSIS... A MASSIVE SURFACE AND 500 HPA ANTICYCLONE OVER THE WESTERN ATLANTIC WILL SLOWLY WEAKEN OVER THE NEXT SEVERAL DAYS AS A RIDGE TO OUR WEST MOVES OVER OUR REGION. THE RESULT IS ABOVE NORMAL HEIGHTS INTO EARLY NEXT WEEK. A TROUGH IN THE NORTHERN STREAM SHOULD WEAKEN THE RIDGE AND COULD TRIGGER SHOWERS TUESDAY- WEDNESDAY BUT YET ANOTHER RIDGE MOVES IN QUICKLY BEHIND THIS SYSTEM BY NEXT THURSDAY. NOT A GOOD PATTERN FOR SIGNFICANT RAINFALL AND NEAR NORMAL TEMPERATURES MOST OF THE PERIOD. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... THE SLOWLY RETREATING 1040HPA HIGH IS PRODUCING LOW-LEVEL EASTERLY FLOW. THUS...THE LOW CLOUDS AND MARINE LAYER HAVE MOVED ACROSS LANCASTER AND LEBANON COUNTIES. THE LEADING EDGE IS NO INTO YORK AND DAUPHIN COUNTIES. THE WINDS DIED AND IT REMAINED CLEAR ENOUGH SUCH THAT TEMPERATURES WERE A FEW DEGREES OTHER SIDE OF FREEZING. WE KEPT THE FROST ADVISORY UP DESPITE THE APPROACHING CLOUDS. AFTER A COLD START SHOULD TURN OUT TO BE A PRETTY GOOD DAY. SATELLITE IMAGERY SHOWS CLOUDS IN THE SOUTHERN STREAM AND NORTHERN STREAM WILL PRODUCED MOSTLY CLOUDY DAY. LEANED TOWARD A NAM/SREF BLEND IN THE POPS WHICH INDICATED LATER AFTERNOON LIGHT RAIN SHOWERS ALONG THE NY BORDER. LOWERED THE POPS BELOW THE ENSEMBLE FREQUENCY DISTRIBUTION. SREF IS TOO WET WITH LOW QPF SO LOWERED VALUES. MOST AREAS WILL REMAIN RAIN FREE. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/...
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THE ONLY RAIN POTENTIAL IS IN THE NORTHWEST 3 HOURS EITHER SIDE OF ABOUT 7 PM. IT SHOULD BE QUITE LIGHT. AS IN PREVIOUS PERIOD USED BLEND OF SREF AND NAM FOR FREQUENCY TO MAKE A POP. THE WEAK FRONT AHEAD OF THE APPROACHING ANTICYCLONE WILL USHER IN SOME DRY AIR WITH -1 SIGMA PW ANOMALIES. THIS SHOULD HELP REDUCE CLOUDS. SHOULD BE MOSTLYRAIN EVENT. HEIGHTS SHOULD DROP SLIGHTLY BELOW NORMAL WEDNESDAY AND 850 HPA TEMPS DROP TO JUST BELOW NORMAL. HEIGHTS AND TEMPERATURES REBOUND BACK TOWARD NORMAL THURSDAY AND FRIDAY COULD BE A RELATIVELY WARM DAY. UNCERTAINTY GROWS IN FORECAST AND SOME ENSEMBLE MEMBERS SHOW SURGE OF MOISTURE IN WARM AIR AHEAD OF YET ANOTHER POTENTIAL TROUGH. THE CHANCE OF RAIN SHOULD GRADUALLY INCREASE IN THE FRIDAY OR SATURDAY TIME FRAME.
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&& .AVIATION /09Z FRIDAY THROUGH TUESDAY/...
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A LAYER OF SHALLOW/BKN MVFR-LOW END VFR STRATOCU WILL BE SLIDING INTO SUSQ VALLEY AIRFIELDS FROM THE SE OVERNIGHT...AND ULTIMATELY EDGING INTO PORTIONS OF THE CENTRAL MTNS JUST BEFORE SUNRISE. MAINLY SUNNY SKIES WILL CONTINUE WITH SOUTHEAST TO SOUTH-SOUTHEAST WINDS AVERAGING TO 8-12 KTS WITH OCCASIONAL GUSTS AROUND 20 KTS. THE WIND WILL SUBSIDE BY 00Z. DURING THE DAY ON FRI...CHANCE FOR LIGHT RAIN TO IMPACT MAINLY NW LATE IN THE AFTERNOON INTO THE EVE WITH LOW PROB OF RESTRICTIONS. VFR ELSEWHERE. LI SUNNY AND WITH 850 HPA TEMPS IN THE +3 TO 0C RANGE EXPECT NEAR NORMAL HIGH TEMPERATURES. 2M TEMPS SUPPORT WIDESPREAD HIGHS IN THE 50S TO AROUND 60.
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&& .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
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AT THIS TIME THE ENSEMBLES SUGGEST THE BEST CHANCE OF RAIN IN THE NEXT WEEK WILL BE IN THE TUESDAY-WEDNESDAY TIMEFRAME. GEFS FAVORS RAIN AHEAD OF THE DEEPENING TROUGH AND FRONTAL SYSTEM MAINLY TUESDAY. BUT TIMING COULD CHANGE AND SOME CHANCE LINGERING INTO EARLY WEDNESDAY. THE COMING 7 DAYS IN GENERAL... SATURDAY NIGHT INTO SUNDAY THE REGION WILL BE DOMINATED BY A STRONG ANTICYCLONE. SHOULD BE GENERALLY FAIR DRY WEATHER. THE ANTICYCLONE WEAKENS MONDAY BUT STILL IN A RIDGE. VERY WEAK FLOW AHEAD OF THE APPROACHING FRONTAL BOUNDARY. THERE IS NO PRESSURE GRADIENT OVER MOST OF THE EASTERN UNITED STATES MONDAY IN THE GEFS OR NAEFS. A SHORTWAVE AND FRONT SHOULD TRIGGER SHOWERS AND RAIN TUESDAY INTO EARLY WEDNESDAY. TROUGH OVER A RIDGE AND NO BIG PW SURGE...NOT A BIG GHT SOUTHEAST WINDS WILL SHIFT TO THE SOUTH AND THEN SW THROUGH THE DAY...WITH INCREASES TO 5-10 KTS WITH GUSTS TO AROUND 15 KTS. OUTLOOK... TONIGHT-SAT...REDUCED CIGS/VSBYS POSS WITH CHANCE OF LIGHT RAIN SHOWERS MAINLY NW HALF. VFR ELSEWHERE. SUN-MON...NO SIG WX. TUE...SEVERAL-HOUR PERIOD OF MVFR CIGS POSS WITH BRIEF MVFR VSBYS IN SHOWERS ACCOMPANYING A COLD FRONTAL PASSAGE.
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&& .CTP WATCHES/WARNINGS/ADVISORIES... FROST ADVISORY UNTIL 8 AM EDT THIS MORNING FOR PAZ057-059- 063>066. && $$ SYNOPSIS...GRUMM NEAR TERM...LA CORTE SHORT TERM...DANGELO/LAMBERT LONG TERM...GRUMM AVIATION...RXR

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