Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 251531 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 1131 AM EDT FRI JUL 25 2014 .SYNOPSIS... HIGH PRESSURE WILL BUILD ACROSS THE OHIO VALLEY AND MID-ATLANTIC TODAY AND MOVE OFFSHORE TONIGHT. ON THE BACKSIDE OF THE HIGH PRESSURE SYSTEM A WARM FRONT AND ASSOCIATED LOW PRESSURE SYSTEM WILL MOVE ACROSS THE MIDWEST ON SATURDAY AND INTO OUR REGION BY SATURDAY NIGHT AND PUSH NORTH OF THE REGION ON SUNDAY. A 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/... NOT MANY CHANGES NEEDED (ONE WOULD HOPE SO ON A DAY LIKE TODAY) WITH THE NEXT ESTF UPDATE EITHER. THE MORNING 12Z SOUNDINGS SHOW AN EXCELLENT CAP AND CONVECTIVE TEMPS AS HIGH AS AROUND 100 DEGREES. LATEST LAPS SOUNDINGS SUGGESTING MAYBE A COUPLE OF REALLY HIGH BASED CU PRIMARILY FROM THE MASON DIXON LINE/AC EXPRESSWAY NORTH. TEMPS ON/CLOSE TO SCHEDULE, SO NO CHANGE THERE. DEW POINTS ARE RUNNING HIGHER THAN EXPECTED AND SOME UPWARD ADJUSTMENTS HAVE BEEN MADE. A SEA AND BAY BREEZE FRONT IS EXPECTED TO MOVE INTO NJ AND DE THIS AFTERNOON. HIGH PRES WILL BUILD INTO THE REGION TODAY AND A DRY AND PLEASANT DAY IS IN STORE, WITH DEW POINTS IN THE 40S AND 50S, WHICH IS SPECTACULAR FOR LATE JULY! && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SATURDAY/... THE HIGH WILL MOVE TO THE EAST TONIGHT AND THE WIND WILL BECOME MORE S TO SWLY BUT STILL BE LIGHT AND DEW POINTS WILL CREEP UP A BIT, BUT AGAIN DRY WX IS EXPECTED. && .LONG TERM /SATURDAY THROUGH THURSDAY/... SATURDAY AND SATURDAY NIGHT: A WARM FRONT APPROACHES THE REGION FROM THE MIDWEST AND OHIO VALLEY THEN PUSHES NORTHEAST THROUGH THE REGION SATURDAY NIGHT. THE RESULT WILL BE INCREASE IN SOUTHERLY MOISTURE AND MOISTURE TRANSPORT INTO THE REGION. MID-LEVEL AND SURFACE TEMPERATURES LOOK TO RESPOND IN KIND WITH THE SOUTHERLY AND SOUTHWEST ADVECTION, 925 MB TEMPS NEAR 20C SHOULD YIELD SURFACE TEMPERATURES JUST UNDER 90 FOR PHL AND IN THE 80`S ELSEWHERE ACROSS THE REGION. AS MENTIONED IN THE PREVIOUS FORECAST THE RAPID RISE OF DEWPOINTS APPEARS SUSPECT AND IS MUCH SLOWER WITH THE LATEST 00Z MAV AND MET GUIDANCE SETS. THE SLOWER DEWPOINT RISE MAY LIMIT THE AMOUNT OF DESTABILIZATION THAT OCCURS DURING THE DAY AS WELL. A FEW HUNDRED J/KG OF CIN COUPLED WITH 700 MB TEMPS NEAR 10C COULD ALLOW FOR THE FORMATION OF A WEAK CAP ACROSS THE SOUTHERN PART OF THE REGION. THE MAJORITY OF THE OPERATIONAL MODELS SUGGEST THE BEST CHANCE OF ANY SHORTWAVE/TRIGGER FOR CONVECTION TO BE ACROSS THE NORTHERN HALF OF THE REGION SATURDAY NIGHT, CLOSER TO THE WARM FRONT. WILL MAINTAIN CHANCE POPS ACROSS THE NORTH AND SLIGHT ACROSS THE SOUTH. ALSO OF INTEREST IS THE POTENTIAL FOR 30-50 KTS OF 0-6 KM BULK SHEAR AS WELL. IF STORMS CAN FORM SATURDAY NIGHT THERE IS A POTENTIAL FOR ORGANIZATION AND A DAMAGING WIND THREAT IF INSTABILITY OF THE MODELED 1000 J/KG OR SO DOES MATERIALIZE. PW VALUES JUST UNDER 2 INCHES SUGGEST A HEAVY RAIN THREAT WITH ANY STORMS AS WELL. THE CURRENT SPC OUTLOOK DOES NOT FEATURE A SEVERE THREAT IN THIS PERIOD LIKELY DUE TO THE LIMITED COVERAGE OF THE STORMS. AS THE MAIN STORM CHANCE IS LATE SATURDAY MODELED MOMENTUM TRANSFER SUGGESTS SOME GUSTS FROM 15-20 MPH ARE POSSIBLE IN THE AFTERNOON ON SATURDAY. SUNDAY AND SUNDAY NIGHT: CONTINUED WEST-SOUTHWEST FLOW IN THE WARM SECTOR. GOOD AGREEMENT AMONG THE GFS ENSEMBLES, 12Z ECMWF ENSEMBLE MEAN AND THE OPERATIONAL GFS AND CMC RUNS THAT THE HIGHEST CHANCE OF STORMS WILL BE SUNDAY NIGHT IN ASSOCIATION WITH THE STRONGEST VORT MAX AND ASSOCIATED SHORTWAVE. ON THE OTHER HAND THE NEW 00Z ECMWF RUN IS SLOWER AND HAS THE MAIN SHOW ON MONDAY. WENT HIGH CHANCE POPS SUNDAY AFTERNOON AND LOW END LIKELY POPS FOR SUNDAY NIGHT MORE ALONG THE LINE OF THE CMC AND GFS. FOR QPF STAYED CLOSE TO THE 21Z SREF. SIMILAR TO SATURDAY ENOUGH BULK SHEAR MAY BE PRESENT TO ORGANIZE STORMS THAT DO FORM. HOWEVER THE AMOUNT OF DESTABILIZATION IS IN QUESTION WITH MODELED CAPE VALUES ONLY AROUND 1000 J/KG AND WILL BE DEPENDENT ON CONVECTION FROM THE NIGHT BEFORE, PW VALUES NEAR 2 INCHES SUGGEST A CONTINUED HEAVY RAIN THREAT FROM STORMS. 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. THE SPC FEATURES THE REGION IN A SLIGHT RISK FOR SEVERE THUNDERSTORMS DUE TO THE POTENTIAL FOR THE STORMS TO ORGANIZE AND FOR WIND/HAIL THREATS. THE HWO HAS BEEN UPDATED FOR THIS. 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 ON THE GFS AND CMC. THE NEW 00Z ECMWF IS SLOWER WITH THE FRONT LEADING TO ANOTHER ROUND OF SHOWERS AND THUNDER. FOR NOW CONTINUED WITH A MORE PROGRESSIVE IDEA CENTERING THE CHANCES IN EARLIER PERIODS BUT DID RAISE POPS IN THIS PERIOD. ANOTHER GUSTY DAY AS ONCE MODELED MOMENTUM TRANSFER SHOWS POTENTIAL FOR SOME GUSTS OF 15-20 MPH. RAIN MAY KEEP TEMPERATURES DOWN BUT MID-LEVEL TEMPERATURES SUGGEST ANOTHER HOT DAY. TEMPERATURES MAY TRY AND SPIKE AHEAD OF THE COLD FRONT AS WELL. MORE UNCERTAINTY WITH TEMPERATURES IN THIS PERIOD AS RAIN MAY KEEP TEMPERATURES DOWN BUT A TEMPERATURE SPIKE COULD OCCUR AHEAD OF THE FRONT. TUESDAY THROUGH THURSDAY: 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 HIGHS ON TUESDAY AND WEDNESDAY. EVEN WITH THIS ABNORMALLY COOL AIRMASS THERE IS GOOD AGREEMENT AMONG THE MEX, WPC AND MODELED TWO METER TEMPERATURES IN THIS PERIOD. WENT ON THE COOLER END OF GUIDANCE CLOSE TO WPC IN MOST PERIODS. LAPSE RATES MAY STEEPEN UP TUESDAY AFTERNOON FOR THE FORMATION OF SOME CUMULUS ON THE BACKSIDE OF THE TROUGH ACROSS THE NORTH WITH THE AID OF ELEVATION. OTHERWISE EACH DAY LOOKS MOSTLY SUNNY. DEWPOINT DEPRESSIONS LOOK TO LARGE FOR WEDNESDAY AND THURSDAY FOR MUCH IN THE WAY OF AFTERNOON CUMULUS. && .AVIATION /16Z FRIDAY THROUGH TUESDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. VFR CONDS EXPECTED THRU THE TAF PD, WITH HIGH PRES IN CONTROL. THE HIGH WILL GRADUALLY MOVE EWD THRU TONIGHT AND THE WIND WILL SHIFT FROM N OR NW ERLY TO W TO SW BY TONIGHT. WIND SPEED SHUD GENLY BE LESS THAN 10 KT. WITH THE LIGHT WIND, THE GUID IS HINTING AT A BIT OF A SEABREEZE, MAINLY FOR KACY AND PSBLY FOR KMIV DURG THE LATE AFTN. OUTLOOK... SATURDAY AND SATURDAY NIGHT...BRIEF MVFR AND IFR RESTRICTIONS IN SCATTERED THUNDERSTORMS. HIGHEST CHANCE FOR RESTRICTIONS IS ON SATURDAY AFTERNOON AND EVENING FOR RDG, ABE, TTN, AND POINTS NORTH. SUNDAY THROUGH MONDAY NIGHT...BRIEF MVFR AND IFR RESTRICTIONS IN THUNDERSTORMS. SOME SOUTHWEST WIND GUSTS AROUND 15 KNOTS POSSIBLE MONDAY AFTERNOON OUTSIDE OF THUNDERSTORMS. TUESDAY: VFR. && .MARINE... WITH HIGH PRES OVER THE REGION TODAY AND MOVG OVER THE CSTL WATERS TONIGHT, NO MARINE HEADLINES ARE ANTICIPATED THRU THE NR AND SHORT TERM PDS. OUTLOOK... SATURDAY...SEAS AND WINDS EXPECTED TO STAY UNDER SCA CRITERIA. A FEW WIND GUSTS AROUND 20 KNOTS POSSIBLE SATURDAY AFTERNOON. SATURDAY NIGHT...SEAS APPROACHING FIVE FEET AT TIMES. WINDS BELOW SCA CRITERIA. SUNDAY THROUGH TUESDAY...FOUR FEET SEAS DECREASING LATE IN THE DAY. HOWEVER SEAS MAY APPROACH FOUR FEET AT OTHER TIMES IN THIS PERIOD. WINDS BELOW SCA CRITERIA. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...NONE. && $$ SYNOPSIS...GAINES NEAR TERM...GIGI/NIERENBERG SHORT TERM...NIERENBERG LONG TERM...GAINES AVIATION...GAINES/NIERENBERG MARINE...GAINES/NIERENBERG

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