Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 180825 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 425 AM EDT FRI APR 18 2014 .SYNOPSIS...
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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.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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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.
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&& .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 MOSTLY 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/... THE 17/12Z MEDIUM RANGE MODEL AND ENSEMBLE GUIDANCE HAS COME INTO MUCH BETTER AGREEMENT ON THE LARGE SCALE PATTERN EVOLUTION ACROSS THE LOWER 48 THIS PERIOD...SUPPORTING INCREASING CONFIDENCE IN THE FORECAST. THE MAIN THEME FOR CENTRAL PA OVER THE NEXT 7+ DAYS WILL BE A DRY AND RELATIVELY BENIGN WEATHER PATTERN...WITH NO SIGNIFICANT RAIN-PRODUCING SYSTEMS ON THE HORIZON. THIS SHOULD CONTRIBUTE TO INCREASING FIRE WEATHER CONCERNS. TEMPERATURES WILL MODERATE THROUGH NEXT WEEK...TRENDING WARMER WITH THE ODDS FAVORING A TILT TOWARD THE WARMER-SIDE OF LATE APRIL CLIMATOLOGY. NRN STREAM SHORTWAVE TROUGH AND SFC COLD FRONT PUSHING EASTWARD FROM THE GREAT LAKES REGION INTO THE NORTHEAST STATES WILL BRING SCT...VERY LIGHT RAIN SHOWERS TO NW/N-CENTRAL PA LATE FRIDAY NIGHT INTO EARLY SATURDAY MORNING. LIMITED RETURN FLOW AND RELATIVELY COOL/DRY AIRMASS IN PLACE AHEAD OF THIS SYSTEM SHOULD LIMIT QPF AMTS TO AOB 0.10 INCH. MODEL CONSENSUS KEEPS PCPN ASSOCIATED WITH CLOSED SRN STREAM LOW TO THE SOUTH OF THE AREA...WITH CANADIAN HIGH PRESSURE REGAINING CONTROL OF THE SYNOPTIC PATTERN THROUGH THE REMAINDER OF EASTER WEEKEND. GUIDANCE TEMPERATURES APPEAR MARGINAL FOR FROST SUN-MON MORNING ACROSS THE LOWER SUSQ VLY WHERE THE GROWING SEASON IS OFFICIALLY UNDERWAY. THE BEST OPPORTUNITY/HIGHEST PROBABILITY FOR APPRECIABLE RAINFALL /0.25 TO 0.50 INCH AMOUNTS/ OVER THE NEXT 7 DAYS WILL LIKELY COME ON TUESDAY...WITH SLIGHTLY BETTER MOISTURE IN PLACE AHEAD OF AN APPROACHING SHORTWAVE TROUGH AND SFC COLD FRONT. THE ECMWF IS MORE AGGRESSIVE IN BRINGING HEIGHT FALLS INTO THE NORTHEAST ON DAY 7/WED EVENTUALLY CLOSING OFF A 500MB LOW NEAR SOUTHERN NEW ENGLAND. MEANWHILE THE GFS/GEFS ARE NOT AS STRONG AND GENERALLY MORE PROGRESSIVE ALOFT...WHICH LEADS TO FASTER HEIGHT RISES HEADING INTO THE SECOND HALF OF NEXT WEEK. THE SENSIBLE WEATHER HIGHLIGHT IS PROBABLY A RELATIVE MINIMUM IN DAYTIME HIGH TEMPERATURES FOR NEXT WEDNESDAY WITH BOTH MODELS/EFS DEPICTING A WEAK NEGATIVE H5-H7 ANOMALY INVOF THE NEW ENGLAND COAST. UPPER TROUGH/CLOSED LOW IS PROGGED TO MIGRATE EWD ACROSS THE NRN ROCKIES INTO THE UPPER MIDWEST WED-FRI. DOWNSTREAM RIDGE AXIS OVER THE CENTRAL PLAINS/MS VLY/MID-SOUTH SHOULD REACH THE EAST COAST BY THE END OF NEXT WEEK. THIS SUGGESTS A WARMING TREND FOLLOWING THE BRIEF COOL-DOWN MIDWEEK WITH MAX TEMPS POSSIBLY HEADING BACK TO/OR ABOVE 70F. && .AVIATION /08Z FRIDAY THROUGH TUESDAY/... 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. LIGHT 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. && .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...STEINBUGL AVIATION...RXR

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