AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 510 PM EDT THU JUL 7 2011 .SYNOPSIS... A WEAK FRONT ACROSS THE AREA WILL CONTINUE TO BRING UNSETTLED WEATHER ACROSS THE REGION THROUGH FRIDAY EVENING. A HIGH PRESSURE SYSTEM WILL BUILD OVER THE AREA SATURDAY AND BRING FAIR AND MORE COMFORTABLE WEATHER TO THE AREA THIS WEEKEND AND INTO MONDAY. ANOTHER FRONTAL SYSTEM MAY BRING MORE SHOWERS TO THE REGION LATER MONDAY INTO TUESDAY. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... SHOWERS AND THUNDERSTORMS CONTINUE TO IMPACT THE FORECAST AREA AND WILL CONTINUE THROUGH THIS EVENING BEFORE DIMINISHING OVERNIGHT. THE THUNDERSTORMS WILL PRODUCE LOCALLY HEAVY RAINS AND GUSTY WINDS, ALONG WITH SOME SMALL HAIL. AFTER THE STORMS DISSIPATE, THINGS BEGIN TO CLEAR OUT A LITTLE BIT WITH SKIES BECOMING PARTLY CLOUDY FOR THE OVERNIGHT PERIOD. AREAS OF FOG MAY DEVELOP IN AREAS THAT RECEIVE RAIN TODAY. THE OVERNIGHT LOWS WILL BE VERY WARM AND IT WILL REMAIN VERY HUMID TONIGHT. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH SUNDAY/... FRIDAY AND FRIDAY NIGHT SHOULD BE CONVECTIVELY ACTIVE WITH THE HOT AND HUMID AIRMASS FINALLY GIVING WAY TO AN APPROACHING UPPER TROUGH/SFC COLD FRONT. THE SPC IS INDICATING A SLGT CHC FOR CONVECTION ACROSS THE SRN AREAS WITH AMPLE CAPE AND DECENT SHEAR IMPOSED OVER THE SAME AREAS. GUSTY WINDS/HEAVY RAINS WILL ACCOMPANY TSTMS. TEMPERATURES FRI WILL BE LESS THAN TODAY WITH MORE CLOUDS AND SHOWERS IN PLACE. SAT THRU SUN WILL FEATURE FAIR WEATHER AS HIGH PRESSURE BUILDS IN TO THE MIDDLE ATLANTIC. A VERY SMALL CHC FOR SHOWERS WILL REMAIN IN THE GRIDS FOR SAT MORNING...IN CASE ANY LINGERING ACTIVITY WITH THE FRONT FROM FRI NIGHT LASTS INTO SAT. THE BEST CHC FOR THIS HAPPENING WILL BE OVER THE DELMARVA AREA. IT WILL STILL BE VERY WARM THIS WEEKEND...BUT THE LOWER DEW POINTS WILL MAKE THE AIR MUCH MORE COMFORTABLE THAN RECENT DAYS. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... NOT TOO MANY CHANGES IN THE LONG TERM FROM THE LATEST SUITE OF MODEL RUNS. THE CAN GGEM WAS NOT USED AS NONE OF THE OTHER MODELS HAD AS STRONG A LOW EXITING NORTH CAROLINA AND THIS AFFECTED THE CAN FOR THE REST OF THE LONG TERM. THIS PACKAGE LEANED TOWARD THE ECMWF. THE LONG TERM WILL BEGIN WITH HOTTER AND INCREASINGLY MORE HUMID WEATHER EXPECTED. A DECAYING FRONTAL BOUNDARY MIGHT ACT AS A FOCUS FOR AFTERNOON CONVECTION. ALTHOUGH CONFIDENCE IS NOT HIGH AND THUS POPS WERE KEPT NORTHWEST OF THE I95 CORRIDOR CLOSER TO THE APPROACHING COLD FRONT. PENDING SKY COVER AND FRONTAL POSITION ON TUESDAY, MONDAY SHOULD BE THE HOTTEST DAY OF THE LONG TERM WITH SOME MID 90S POSSIBLE. THE APPROACHING COLD FRONT SHOULD THEN ACT AS A TRIGGER FOR MORE ORGANIZED SHOWERS AND THUNDERSTORMS. WE KEPT POPS RELATIVELY LOW DUE TO THE CONSENSUS TIMING IN WHICH IT LOOKS TO BE TOO FAR TO THE NORTHWEST ON MONDAY AND POSSIBLY TOO DEEP INTO OUR CWA ON TUESDAY. THE GFS IS MORE AGGRESSIVE WITH MOVING THE COLD FRONT THROUGH WHICH WE TEMPERED SOMEWHAT GIVEN JULY CLIMO. THUS OUR MAX TEMPS ON TUE AS THE FRONT IS MOVING THROUGH AND ON WED AS THE RELATIVELY COOLER AIR IS ARRIVING IS ABOVE MEX MOS GUIDANCE. AT THIS POINT THERE IS FAIRLY GOOD MODEL CONSENSUS FOR OUR CWA TO BE NEAR THE CANADIAN HIGH PRESSURE SYSTEM WITH THE RELATIVELY DRIEST AND COOLEST DAY OF THE LONG TERM PERIOD. && .AVIATION /21Z THURSDAY THROUGH TUESDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. TONIGHT... VFR TO START WITH CONVECTION PROBABLY SETTLING DOWN BUT NOT COMPLETELY CONVINCED IT CANNOT RE-FIRE DURING THE EARLY MORNING. MVFR VSBY IN FOG/HAZE EXPECTED LATER TONIGHT....ESP IN THE FRONTAL ZONE WHICH MAY END UP N OF PHL ALL NIGHT. CONFIDENCE BELOW AVG ON CONVECTIVE OCCURRENCE AFTER 01Z. OUTLOOK... FRIDAY...VFR CIGS DEVELOP BY 17Z WITH CLUSTERS OF HEAVY RAIN SHOWERS AND TSTMS...ISOLATED SEVERE TSTMS EXPECTED. WIDESPREAD MVFR CONDS MAY DEVELOP IN THE AFTERNOON NNJ AND NE PA...ESPECIALLY VCNTY KABE AND THE POCONOS. LIGHT WIND TRENDING NE. QUASI STATIONARY FRONT PROBABLY JUST N OF KPHL TO START THE DAY BUT PROBABLY MOVES SOUTHWARD DURING THE AFTERNOON DOWN INTO N DEL. FRIDAY NIGHT...MVFR CONDS PROBABLY SPREADING SEWD TO MOST TAF LOCATIONS IN THE WAKE OF THE DEPARTING COLD FRONT AND ASSTD CONVECTION. THIS WEEKEND...WEAK HIGH PRESSURE BUILDING EAST FROM THE GREAT LAKES SHOULD PROVIDE VFR CONDITIONS. THE ONLY EXCEPTION HERE COULD BE SATURDAY EVENING...AS WIDELY SCATTERED THUNDERSTORMS COULD AFFECT NORTHERN AREAS. LIGHT WIND. NEXT MONDAY...VFR EXCEPT PATCHY MVFR FOG NEAR DAWN MAY SEE TSTMS LATE AT NIGHT IN WARM AIR ADVECTION ASSOCIATED WITH A WARM FRONTAL PASSAGE. SW WIND MAY GUST 15-20 KTS IN THE AFTN. && .MARINE... NO HEADLINES ATTM. LOW PROB WE WILL NEED AN SCA FRI NIGHT IN THE ATLC WATERS OFF DEL. CONVECTIVE GUSTS AND LIGHTNING ARE THE BIG PROBLEM THIS AFTERNOON AND AGAIN FRIDAY INTO FRIDAY EVENING IN ASSN WITH QSTNRY FRONT FM NYC TO JUST N OF PHL. THAT FRONT SAGS SOUTHEAST OF OUR AREA TOMORROW NIGHT AND THE CONVECTION MOVES OUT TO SEA. A DRY NICE WEEKEND IS ENVISIONED AS HIGH PRESSURE SETTLES IN WITH A DRIER AIRMASS AND LIGHT WIND. NEXT MONDAY...SW FLOW GUSTING 15 KTS AND POSSIBLE TSTMS AT NIGHT. && .HYDROLOGY... THERE IS AMPLE MOISTURE THIS EVENING TO CREATE DOWNPOURS AND LOCALIZED FLOODING CONCERNS FOR THIS EVENING. THE CELLS MOVEMENT MAY BE ENOUGH TO PREVENT ANY WIDESPREAD PROBLEMS. THIS CONTINUES INTO FRIDAY WITH CONTINUED HIGHER MOISTURE AND TSTM FORMATION EXPECTED BY AFTERNOON. THE FFG IS LOWER ACROSS THE NORTH...SO THE LATER SHIFTS MAY CONSIDER A WATCH FOR THOSE AREAS. THERE IS ENOUGH UNCERTAINTY ATTM TO PRECLUDE A WATCH NOW. WE WILL KEEP THE HEAVY RAINS WORDING IN THE GRIDS/ZONES FOR NOW. && .CLIMATE... HEAT WAVE CONTINUES TODAY ILG/PHL REGION AND LOW PROBABILITY IT MAY EXTEND INTO FRIDAY PER THE ULTIMATE POSITION OF THE QUASI STATIONARY FRONT MIDDAY FRIDAY AND THE RESULTANT TIMING OF PERSISTENT CONVECTION PRIOR OR SUBSEQUENT TO 18Z FRIDAY. TODAY THE MODEST HEAT WAVE IS DAY5 FOR PHL AND DAY4 FOR ILG. SINCE MAY 6TH AT KPHL...ONLY 8 DAYS BELOW NORMAL WITHIN A PERIOD OF 61 DAYS....IE 53 AOA NORMAL IN THESE 61. REGARDING TOMORROW... HAVE BEEN LOOKING ALOT AT PARALLEL NAM MOS VS THE ACTUAL NAM MET MOS. IT SEEMS OVERALL TO BE PERFORMING SLIGHTLY BETTER THAN NAM MOS. TODAYS 12Z GFS MAVMOS HAS AN IDEA THAT TOMORROW COULD REACH 87 AT KILG...WHILE THE 12Z/7 METMOS HAS 82 BUT THE PARALLEL METMOS 87. THE IDEA...ITS WORTHY OF COMPROMISING AND PROBABLY RUNNING A BIT HIGHER THAN THE METMOS GUIDANCE. MUCH IF NOT ALL OF THIS SECTION WILL PROBABLY BE DELETED IN SUBSEQUENT AFD EFFORTS. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...NONE. && $$ SYNOPSIS...MEOLA/O`HARA