Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 241529 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 1129 AM EDT THU JUL 24 2014 .SYNOPSIS... A COLD FRONTAL BOUNDARY WILL CONTINUE MOVING OFFSHORE TODAY. HIGH PRESSURE WILL BUILD ACROSS THE OHIO VALLEY TONIGHT AND ON FRIDAY. THE HIGH PRESSURE SYSTEM WILL MOVE EAST OF THE REGION ON SATURDAY AND BE FOLLOWED BY THE PASSAGE OF A WARM FRONT FROM THE SOUTH BY SATURDAY NIGHT AND BE LOCATED TO OUR NORTH ON SUNDAY. ANOTHER COLD FRONTAL BOUNDARY THEN WILL SWEEP FROM WEST TO EAST ACROSS THE REGION ON MONDAY. A HIGH PRESSURE SYSTEM WILL BUILD IN BEHIND THE COLD FRONT FOR THE MIDDLE HALF OF NEXT WEEK. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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THE CDFNT HAS MOVED SOUTH OF OUR CWA. NEXT ESTF UPDATE WE WILL SHAVE BACK MENTION OF POPS FURTHER. THE HRRR AND COSPA TREND HAS BEEN FOR LESS AND LESS. THIS IS LIKELY DUE TO THE CIRRUS SHIELD SLOWING OUR TEMP ASCENT TO THE CONVECTIVE TEMP AS MOST OF OUR TEMP ERRORS HAVE BEEN ON THE HIGH SIDE. SOME OF THE SHWRS IN NOVA HAVE BEEN UNDERDONE BY THE MESOSCALE MODELS, SO WILL KEEP A BUFFER LOW CHC INTO CENTRAL DELMARVA AND PARTS OF SERN NJ. BASED ON THE SLOWER TEMP ASCENT AND WHERE THEY ARE CURRENTLY OCCURRING, WE NOW HAVE THE MENTION OF THUNDER ONLY IN OUR FAR SRN CWA AND ADJACENT COASTAL WATERS. FAIRLY UNIFORM MAX TEMPS AWAY FROM THE HIGHER TERRAIN EXPECTED THIS AFTERNOON.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM FRIDAY/... HIGH PRES WILL BUILD EWD AND INTO THE AREA TONIGHT. ANY PRECIP WILL END EARLY AND THE SKY WILL CLEAR. OVERALL, A QUIET NIGHT IS IN STORE. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... FRIDAY AND FRIDAY NIGHT: HIGH PRESSURE GLIDES EAST FROM THE OHIO VALLEY INTO OUR REGION. VARIABLE WINDS, PLENTY OF SUNSHINE AND NOT THAT HOT SINCE THIS AIRMASS WILL BE COMING FROM CANADA! LITTLE SPREAD IN THE MODELS ON MOST IF NOT ALL WEATHER ELEMENTS. TRICKIEST PART OF THIS PERIOD IS HOW MUCH RADIATIONAL COOLING CAN OCCUR IN RURAL AREAS BEFORE THE FLOW TURNS MORE SOUTHERLY BY SATURDAY. OPTED TO GO A TOUCH COOLER THAN MEX/MAV/MET IN A FEW SPOTS WITH LOWS FRIDAY NIGHT. SATURDAY AND SATURDAY NIGHT: A WARM FRONT APPROACHES THE REGION FROM THE SOUTH AND WITH A DEPARTING HIGH PRESSURE THE FLOW TURNS SOUTHERLY. MODELED MOMENTUM TRANSFER SUGGESTS SOME GUSTS CLOSE TO 20 MPH ARE POSSIBLE IN THE AFTERNOON, WENT HIGHER THAN A STANDARD 125% FOR WIND GUSTS. MID-LEVEL AND SURFACE TEMPERATURES LOOK TO RESPOND IN KIND AFTER THE WARM FRONTAL PASSAGE, 925 MB TEMPS NEAR 20-22C SHOULD YIELD SURFACE TEMPERATURES JUST UNDER 90 FOR PHL AND IN THE 80`S ELSEWHERE ACROSS THE REGION. HUMIDITY IS ON THE RISE BUT THIS WILL BE LIKE MORE TYPICAL JULY HEAT WITH HEAT INDEX VALUES WELL UNDER ADVISORY LEVELS. THE WARM FRONT MAY PROVIDE ENOUGH LIFT FOR SOME SCATTERED SHOWERS AND THUNDERSTORMS FOCUSED ACROSS THE NORTHERN PART OF THE REGION. THE 21Z SREF AND THE LAST TWO ECMWF RUNS HAVE THESE PINED DOWN WELL. INCREASING CIN COUPLED WITH 700 MB TEMPS NEAR 10C COULD ALLOW FOR THE FORMATION OF A WEAK CAP ACROSS THE SOUTHERN PART OF THE REGION, BEING FURTHER AWAY LOWER CHANCE POPS WERE WARRANTED WHEN COMPARED TO LOCATIONS FURTHER NORTH. SUNDAY AND SUNDAY NIGHT: CONTINUED WEST-SOUTHWEST FLOW IN THE WARM SECTOR. THE LAST FEW GFS RUNS HAVE BEEN MORE AGGRESSIVE WITH CONVECTION BY THE AFTERNOON AND EVENING HOURS. A COMMON THEME THIS SUMMER. THINK THE GFS IS TO AGGRESSIVE WITH THIS. HOWEVER, STORM CHANCES SHOULD INCREASE AS THE MAIN LOW PRESSURE SYSTEM AND COLD FRONT APPROACH THE REGION. GOOD AGREEMENT AMONG THE GFS ENSEMBLES, ECMWF ENSEMBLE MEAN AND THE OPERATIONAL MODELS THAT THE HIGHEST CHANCE WILL BE SUNDAY NIGHT. MAINTAINED LOW END LIKELY POPS ACROSS THE NORTH AND HIGH END CHANCE ACROSS THE SOUTH. FOR QPF STAYED CLOSE TO THE SREF AND ECMWF SIMILAR TO SATURDAY. THOUGH DID RAISE IT SLIGHTLY TO ACCOUNT FOR THE MORE AGGRESSIVE GFS. TEMPERATURES MAY BE RAIN COOLED SUNDAY BUT DID NOT GO IN THAT DIRECTION ATTM. FAIR SHOT AT 90 FOR PHL WITH SLIGHTLY WARMER MODELED MID-LEVEL TEMPERATURES THAN SATURDAY. MONDAY AND MONDAY NIGHT: THE COLD FRONT MOVES THROUGH LIKELY MONDAY AFTERNOON. HOWEVER THIS SHOULD BE TO LITTLE TO LATE IN TERMS OF ANOTHER ROUND OF SHOWERS AND STORMS. THE MAIN CAPE AXIS IS LIKELY TO OFFSHORE AT THIS TIME AND LITTLE IS LEFT FOR A TRIGGER BESIDES THE ACTUAL FRONTAL BOUNDARY. HOWEVER MAINTAINED LOW CHANCE POPS SINCE THE FRONT WILL STILL BE IN THE REGION. CLEARED CONDITIONS OUT MONDAY NIGHT WITH A RETURN TO WESTERLY FLOW. ANOTHER GUSTY DAY AS ONCE MODELED MOMENTUM TRANSFER SHOWS POTENTIAL FOR SOME GUSTS NEAR 20 MPH. TUESDAY AND WEDNESDAY: ANOTHER CANADIAN AIRMASS COMES DOWN INTO THE REGION AS THE SAME GENERAL PATTERN FROM THE WINTERTIME CONTINUES WITH FEW BREAKS. COOL NORTHWESTERLY FLOW WILL BE IN PLACE AS MOST LOCATIONS STRUGGLE TO 80 FOR A HIGH. EVEN WITH THIS ABNORMALLY COOL AIRMASS THERE IS GOOD AGREEMENT AMONG THE MEX, WPC AND MODELED TWO METER TEMPERATURES. TRENDED SLIGHTLY COOLER THAN WPC GIVEN THE LATEST 00Z ECMWF WHICH IS ON THE COOLEST END OF THE MODEL GUIDANCE. LAPSE RATES MAY STEEPEN UP TUESDAY AFTERNOON FOR THE FORMATION OF SOME CUMULUS AND SPOTTY SHOWERS/THUNDER ON THE BACKSIDE OF THE TROUGH ACROSS THE NORTH WITH THE AID OF ELEVATION. OTHERWISE BOTH DAYS LOOK MOSTLY SUNNY. && .AVIATION /16Z THURSDAY THROUGH MONDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. GENLY VFR CONDS ARE EXPECTED TODAY. THERE COULD BE SOME SHRA OR ISOLD TSRA, MAINLY S LATER THIS MRNG THRU ERLY EVE WHICH CUD BRIEFLY DECREASE CIGS/VSBYS. HOWEVER, ODDS ARE LOW ENOUGH TO NOT MENTION IN THE INDIVIDUAL TAF SITES. WIND IS EXPECTED TO BE NW OR N AROUND 10 KTS TODAY DECREASING TO LESS THAN 10 KTS TONIGHT. OUTLOOK... FRIDAY AND FRIDAY NIGHT: VFR SATURDAY THROUGH MONDAY: BRIEF MVFR AND IFR RESTRICTIONS IN SCATTERED THUNDERSTORMS. HIGHEST CHANCE FOR RESTRICTIONS IS ON SUNDAY AFTERNOON AND EVENING FOR RDG, ABE, TTN, AND POINTS NORTH. && .MARINE... WITH HIGH PRES BUILDING INTO THE REGION, NO MARINE HEADLINES ARE ANTICIPATED THRU THE NR AND SHORT TERM PDS. OUTLOOK... FRIDAY THROUGH SATURDAY NIGHT: SEAS AND WINDS EXPECTED TO STAY UNDER SCA CRITERIA. A FEW WIND GUSTS AROUND 20 KNOTS POSSIBLE SATURDAY AFTERNOON. SUNDAY AND MONDAY: SEAS INCREASE TO FOUR FEET ON SUNDAY AND PERHAPS FIVE FEET BY MONDAY MORNING BEFORE FALLING BELOW FIVE FEET MONDAY NIGHT. A FEW WIND GUSTS AROUND 20 KNOTS POSSIBLE SUNDAY AND MONDAY AFTERNOONS. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...NONE. && $$ SYNOPSIS...GAINES NEAR TERM...GIGI SHORT TERM...NIERENBERG LONG TERM...GAINES AVIATION...GAINES/NIERENBERG MARINE...GAINES/NIERENBERG

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