Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 042005 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 405 PM EDT MON MAY 4 2015 .SYNOPSIS... HIGH PRESSURE IN THE WEST CENTRAL ATLANTIC THROUGH TONIGHT. A COLD FRONT SAGS SLOWLY SOUTH ACROSS THE AREA TUESDAY AFTERNOON AND NIGHT. HIGH PRESSURE FOLLOWS OVER THE MID ATLANTIC STATES WEDNESDAY AND THURSDAY, EDGING OFFSHORE FRIDAY THROUGH THE WEEKEND. THIS OCCURS WHILE LOW PRESSURE MEANDERS ALONG THE SOUTHEAST UNITED STATES COAST LATER THIS WEEK INTO THE WEEKEND. && .NEAR TERM /THROUGH TUESDAY/... SURFACE HIGH PRESSURE WILL CONTINUE TO GET SQUEEZED FARTHER SOUTH TONIGHT AS A COLD FRONT APPROACHES FROM THE NORTH. DRY CONDITIONS ARE EXPECTED OVERNIGHT, ALTHOUGH CLOUD COVER WILL INCREASE THROUGH THE NIGHT. SOME SHOWERS MAY BEGIN TO APPROACH OUR FAR NORTHWESTERN AREAS TOWARD DAYBREAK AS THE FRONT GET CLOSER TO THE AREA. GUSTY WINDS THIS AFTERNOON SHOULD DIMINISH/DROP OFF AROUND OR SHORTLY AFTER SUNSET, ALTHOUGH A STEADY SOUTHWEST BREEZE AROUND 5 TO 10 MPH MAY REMAIN FOR MOST AREAS OVERNIGHT. && .SHORT TERM /TUESDAY NIGHT THROUGH 6 PM TUESDAY/... A COLD FRONT IS FORECAST TO MOVE IN FROM THE WEST TUESDAY MORNING, AND SLOWLY PROGRESS EASTWARD THROUGH THE DAY. PW VALUES WILL INCREASE TO AROUND 1.0-1.5 INCHES AS THE FRONT SAGS ACROSS THE AREA, AND WITH AN INCREASE IN MOISTURE AND WARM TEMPERATURES, THERE IS SOME INSTABILITY FORECAST WITH CAPE VALUES APPROACHING 500-1000 J/KG, LI VALUES GO SLIGHTLY NEGATIVE, AND TOTAL TOTAL VALUES APPROACH 50. SO AS THE FRONT MOVES THROUGH THE AREA, AND A SHORT WAVE/VORTICITY PULSE APPROACHES THE AREA DURING THE AFTERNOON SCATTERED SHOWERS ARE EXPECTED TO INCREASE IN COVERAGE, ALONG WITH ISOLATED THUNDERSTORMS. EVEN THOUGH THERE IS INSTABILITY, THERE IS NOT A LOT OF SHEAR FORECAST. ACTUALLY THE STRONGEST SHEAR BUILDS IN BEHIND THE FRONT. STILL, WITH ANY THUNDERSTORMS, THERE COULD BE HEAVY RAIN, ALONG WITH GUSTY WINDS AS WE SHOULD END UP WITH AN INVERTED-V SOUNDING. && .LONG TERM /TUESDAY NIGHT THROUGH MONDAY/... 500 MB: ABOVE NORMAL HEIGHTS WILL PREVAIL OVER MUCH OF THE NORTHEAST USA THIS 6 DAY PERIOD. WE JUST NEED TO MONITOR THE POSSIBLE EVENTUAL INFLUENCE OF A COASTAL SOUTHEAST USA LOW PRESSURE SYSTEM, WHICH MIGHT LEAK SOME MOISTURE NORTHWARD INTO OUR AREA NEXT WEEKEND. TEMPERATURES: CALENDAR DAY AVERAGE ABOVE NORMAL THROUGH THE PERIOD. RELATIVELY MODEST POSITIVE 5 DEGREE DEPARTURES WEDNESDAY AND THURSDAY, THEN ALMOST 10 DEGREES ABOVE FRIDAY AND POSSIBLY MORE THAN 10 DEGREES ABOVE NORMAL EACH DAY SATURDAY THROUGH MONDAY. FORECAST BASIS: UNLESS OTHERWISE NOTED, GENERALLY A 50 50 BLEND 12Z/4 GFS/NAM MOS GUIDANCE TUESDAY NIGHT - WEDNESDAY NIGHT, 12Z/4 MEX MOS THURSDAY AND THURSDAY NIGHT, THEN THE 1521Z/4 WPC GRIDDED ELEMENTS OF MAX/MIN TEMP, 12 HOUR POP, 6 HOUR DEWPOINT-SKY-WIND FROM FRIDAY THROUGH MONDAY. THE DAILIES... TUESDAY NIGHT...SCT SHOWERS/ISOLATED TSTMS, MAINLY SOUTH TWO THIRDS WITH THE CFP. ABOVE NORMAL MINIMUM TEMPS. CONFIDENCE: AVERAGE. WEDNESDAY...CONSIDERABLE CLOUDINESS. A SMALL CHANCE OF LINGERING SHOWERS OVER THE SOUTHWEST PORTION OF THE FORECAST AREA. EASTERLY FLOW IN BETWEEN THE HIGH CENTERED TO OUR NORTH AND THE LINGERING FRONTAL BOUNDARY TO OUR SOUTH WILL PRODUCE COOLER E OR NE WINDS...POSSIBLY GUSTY TO 20 MPH. NO MATTER, MAXIMUM TEMPS SHOULD REMAIN AT OR ABOVE NORMAL EXCEPT POSSIBLY RIGHT ALONG THE ATLANTIC OCEAN WHICH SHOULD BE CHILLY. CONFIDENCE: AVERAGE OR BELOW AVERAGE REGARDING THE MAXIMUM TEMPS AND WHETHER THERE MIGHT BE PATCHES OF LINGERING SHOWERS. IT COULD RUN COOLER THAN CURRENTLY POSTED IN THE PHI FCST. THURSDAY-SUNDAY...BERMUDA HIGH PRESSURE WILL EXTEND BACK TOWARD THE NORTHERN MID-ATLANTIC REGION LATE IN THE WEEK AND THIS WEEKEND. A CLOSED LOW IS FORECAST TO DEVELOP ALONG THE SOUTHEAST COAST LATE THIS WEEK. THE LOW IS NOT EXPECTED TO MOVE MUCH THROUGH THE WEEKEND SINCE IT DEVELOPED UNDERNEATH THE LARGE-SCALE RIDGE WHERE THERE IS MINIMAL STEERING FLOW. THIS WILL ALLOW THE FORECAST AREA TO REMAIN MAINLY DRY THROUGH THE WEEKEND. HOWEVER, WE COULD SEE WEAKLY-FORCED CONVECTION DRIFT EASTWARD INTO THE POCONOS DURING SUNDAY. POSITIVE TEMPERATURE DEPARTURES SHOULD INCREASE AS WE MOVE INTO THE WEEKEND. MORNING FOG AND STRATUS COULD BECOME PART OF THE REALITY THIS WEEKEND. NEXT MONDAY...RATHER WARM AND HUMID AHEAD OF AN APPROACHING COLD FRONT. CHANCE OF SHOWERS AND THUNDERSTORMS. && .AVIATION /20Z MONDAY THROUGH SATURDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. VFR CONDITIONS ARE FORECAST THROUGH TONIGHT AND INTO TUESDAY. A COLD FRONT IS EXPECTED TO SLOWLY MOVE ACROSS THE AREA TUESDAY, WITH SCATTERED SHOWERS DEVELOPING AND INCREASING IN COVERAGE DURING THE AFTERNOON, ALONG WITH A FEW THUNDERSTORMS POSSIBLE. WE HAVE KEPT THUNDERSTORMS OUT OF THE FORECAST FOR NOW, BUT WE HAVE INTRODUCED SHOWERS FOR THE AFTERNOON. IF SHOWERS AND/OR THUNDERSTORMS ARE HEAVY ENOUGH, THEY COULD BRIEFLY REDUCE CIGS/VSBYS, BUT WE WILL WAIT TO INCLUDE RESTRICTIONS UNTIL CONFIDENCE OF OCCURRENCE/TIMING IS HIGHER. GUSTY SOUTHWEST WINDS REMAIN THIS AFTERNOON, WITH GUSTS DIMINISHING/DROPPING OFF AROUND OR SHORTLY AFTER SUNSET. A STEADY SOUTHWEST BREEZE AROUND 5-10 KNOTS MAY REMAIN FOR MANY AREAS OVERNIGHT. WINDS WILL BECOME MORE WEST-NORTHWEST BEHIND THE FRONT LATE TUESDAY. OUTLOOK... TUESDAY NIGHT...PREDOMINATELY VFR. VSBY/CIG RESTRICTIONS POSSIBLE DURING THE NIGHT FROM SCT SHOWERS AND ISO STORMS. RESTRICTIONS WOULD BE LOCALIZED/TEMPORARY. LIGHT WIND. CONFIDENCE: AVERAGE WEDNESDAY..VFR CIGS. A SMALL CHANCE OF SHOWERS. A GUSTY E OR NE WIND OF 15-20 KT DURING THE DAY. CONFIDENCE: AVERAGE WEDNESDAY NIGHT THROUGH FRIDAY...VFR AND LIGHT SOUTH-SOUTHEAST WINDS WITH HIGH PRESSURE IN CONTROL. CONFIDENCE: AVERAGE (NORMALLY ABOVE AVERAGE BUT DON`T LIKE THE MODELED CLOSED LOW NOT TOO FAR TO OUR SOUTH) SATURDAY...POSSIBLE MORNING IFR FIG/STRATUS OTHERWISE VFR DURING THE AFTERNOON. MAX GUST 15 KT DURING THE AFTERNOON. CONFIDENCE: AVERAGE. && .MARINE... SUB-SMALL CRAFT ADVISORY CONDITIONS CONTINUE TO BE FORECAST TONIGHT THROUGH TUESDAY. WINDS ARE EXPECTED TO GUST IN THE LOW 20S, BUT SHOULD REMAIN BELOW ADVISORY LEVELS. THE STRONGEST WINDS WOULD BE EXPECTED ON OUR NORTHERN WATERS. SEAS SHOULD REMAIN 3-4 FEET. SEAS MAY APPROACH 5 FEET OVERNIGHT INTO TUESDAY MORNING, BUT WE THINK IT WOULD BE FARTHER OFFSHORE THAN OUR COASTAL WATERS. OUTLOOK... TUESDAY NIGHT...SWLY WINDS AHEAD OF A COLD FRONT SHOULD SHIFT N BEHIND THE FRONT DURING THE NIGHT. ISOLATED TSTMS MAY MOVE OVER THE WATERS DURING THE EVENING. AT THIS TIME NO MARINE HEADLINE ANTICIPATED THOUGH SEAS MAY EVENTUALLY REACH 5 FT IN THE SOUTHERN NJ OR DE WATERS. MARGINAL CONFIDENCE FOR MEETING SCA HAZARDOUS SEAS CRITERIA AND NO HEADLINE ATTM. WEDNESDAY THROUGH SATURDAY...WINDS AND SEAS BELOW SCA CRITERIA. && .FIRE WEATHER... RED FLAG WARNING REMAINS IN PLACE THROUGH THE EARLY EVENING AS RELATIVE HUMIDITY VALUES HAVE DROPPED INTO THE LOW 20S AND WINDS CONTINUE TO GUST AROUND 20-25 MPH. HUMIDITY VALUES SHOULD REBOUND OVERNIGHT AS TEMPERATURES COOL. ALSO, WIND GUSTS SHOULD DIMINISH BY SUNSET AS WELL. && .EQUIPMENT... OUR PHONE SYSTEM WAS CHANGED LAST WEEK AND WE`RE STILL SHORT SEVERAL PUBLIC PHONE LINES. RESULTS: FREQUENT BUSY SIGNALS FOR THOSE TRYING TO ACCESS OUR FORECASTS VIA THE PHONE. WE`RE NOT SURE WHEN THIS PROBLEM WILL BE RESOLVED. WE APOLOGIZE FOR THIS DIFFICULTY ACCESSING OUR PRODUCTS VIA THE PHONE. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...RED FLAG WARNING UNTIL 8 PM EDT THIS EVENING FOR PAZ054-055- 060>062-070-071-101>106. NJ...RED FLAG WARNING UNTIL 8 PM EDT THIS EVENING FOR NJZ001- 007>010-012-013-015>023-027. DE...NONE. MD...NONE. MARINE...NONE. && $$ SYNOPSIS...DRAG NEAR TERM...ROBERTSON SHORT TERM...ROBERTSON LONG TERM...DRAG 405 AVIATION...DRAG/ROBERTSON 405 MARINE...DRAG/ROBERTSON FIRE WEATHER... EQUIPMENT...

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