Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 102001 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 401 PM EDT THU JUL 10 2014 .SYNOPSIS... A STATIONARY FRONTAL BOUNDARY WILL REMAIN OVER THE DELMARVA TONIGHT BEFORE SLOWLY PUSHING SOUTH OF THE AREA FRIDAY. HIGH PRESSURE BUILDS IN FROM THE NORTHEAST FRIDAY INTO SATURDAY. RETURN FLOW DEVELOPS LATE IN THE WEEKEND AND EARLY NEXT WEEK AS HIGH PRESSURE MOVES OFFSHORE AND AN STRONG UPPER LOW DIGS INTO THE UPPER MIDWEST. A COLD FRONT WILL APPROACH THE EASTERN SEABOARD TUESDAY BEFORE MOVING OFFSHORE BY WEDNESDAY. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... A FLASH FLOOD WATCH HAS BEEN ISSUED FOR OUR DELMARVA AND SOUTHERN NEW JERSEY COUNTIES WHERE IT HAS RAINED HEAVILY DURING THE DAY TODAY, AND THE POTENTIAL FOR ADDITIONAL HEAVY RAIN EXISTS. THE FRONTAL BOUNDARY HAS STALLED ACROSS SOUTHERN NEW JERSEY AND CENTRAL DELMARVA TODAY. PW VALUES REMAIN HIGH WITH VALUES 1.75-2 INCHES ACROSS THE AREA. MEANWHILE, THE MID-LEVEL TROUGH CONTINUES TO APPROACH THE AREA FROM THE WEST AND SEVERAL VORTICITY IMPULSES WILL CONTINUE TO SLIDE ACROSS THE AREA THROUGH THIS EVENING. ALL OF THIS COMBINED WILL HELP ADDITIONAL SHOWERS AND THUNDERSTORMS DEVELOP. IT HAS ALREADY RAINED ACROSS PORTIONS OF THE WATCH AREA TODAY, AND WHERE IT HAS RAINED, IT`S BEEN VERY HEAVY WITH UP TO 3-4 INCHES IN SOME AREAS IN AN HOUR OR TWO. WITH THE POTENTIAL FOR ADDITIONAL HEAVY RAINFALL ACROSS THESE AREAS, WE HAVE ISSUED A FLASH FLOOD WATCH THROUGH THIS EVENING. THERE ARE SCATTERED SHOWERS AND THUNDERSTORMS MOVING THROUGH CENTRAL AND NORTHEASTERN PENNSYLVANIA, THROUGH THESE HAVE BEEN MOVING AND WILL LIKELY BE MORE DIURNAL IN NATURE AND SHOULD DISSIPATE AROUND SUNSET; SO NO WATCH FURTHER NORTH. WE EXPECT MUCH OF THE PRECIPITATION TO BEGIN TO DIMINISH LATER THIS EVENING AND TOWARD MIDNIGHT AS INSATIABILITY WANES AND PW VALUES BEGIN TO LOWER. THEREFORE THE WATCH ENDS AT LOCAL MIDNIGHT. HOWEVER, WITH THE FRONT REMAINING NEARBY AND THE MID-LEVEL TROUGH STILL TO OUR WEST, THERE WILL STILL BE THE POTENTIAL FOR A FEW SHOWERS AND THUNDERSTORMS INTO FRIDAY MORNING. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH 6 PM FRIDAY/... THE PESKY FRONTAL BOUNDARY IS EXPECTED TO PUSH BACK OFFSHORE ON FRIDAY, AND STALL ACROSS THE OCEAN WATERS TO OUR EAST. PW VALUES CONTINUE TO LOWER THROUGH THE DAY, BUT THE MID-LEVEL THROUGH WILL BE MOVING OVERHEAD THROUGH THE DAY. THERE WILL REMAIN THE CHANCE FOR ISOLATED-SCATTERED SHOWERS AND THUNDERSTORMS ACROSS THE AREA, WITH THE BEST POTENTIAL ACROSS SOUTHERN NEW JERSEY AND SOUTHERN DELMARVA. HIGHS ON FRIDAY WILL DEPEND ON HOW MUCH SUNSHINE WE GET, WITH CLOUDY AREAS LIKELY BEING CLOSER TO THE COOLER MET GUIDANCE AND SUNNIER AREAS CLOSER TO THE WARMER MAV GUIDANCE. FOR NOW, WE TOOK A BLEND OF THE MAV/MET/MOSGUIDE FOR DAYTIME HIGHS. && .LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/... SURFACE HIGH PRESSURE CENTERED JUST EAST OF NEW ENGLAND WILL PROVIDE NICE WEATHER THROUGH SATURDAY. FRIDAY NIGHT WILL FEATURE CLEAR SKIES AND COOL TEMPERATURES FOR THIS TIME OF YEAR, AND AN EASTERLY FLOW WILL KEEP HIGHS IN THE 80S ON SATURDAY. CONDITIONS WILL BEGIN TO DETERIORATE SOMEWHAT ON SUNDAY AS A FRONTAL BOUNDARY APPROACHES FROM THE WEST. CLOUDS WILL BE ON THE INCREASE AND SHOWERS AND THUNDERSTORM ACTIVITY WILL BECOME INCREASINGLY LIKELY FROM WEST TO EAST AS THE DAY WEARS ON. THESE CLOUDS SHOULD KEEP THE HIGH TEMPERATURES ON SUNDAY ONE OR TWO DEGREES COOLER THAN SATURDAY. AN ANOMALOUSLY STRONG NRN STREAM CLOSED LOW IS FORECAST TO DIVE SOUTHWARD FROM NEAR HUDSON BAY INTO THE UPPER MIDWEST EARLY NEXT WEEK, SETTING UP A RATHER UNUSUAL PATTERN FOR THIS TIME OF YEAR. THE MID-ATLANTIC REGION WILL BE SITUATED IN AN INCREASINGLY DIFFLUENT FLOW PATTERN ALOFT ON THE SOUTHEASTERN PERIPHERY OF THE AMPLIFYING UPPER TROUGH AND ON THE WESTERN PERIPHERY OF THE WESTERN ATLANTIC RIDGE. THE HEAT AND HUMIDITY WILL RETURN MONDAY AND TUESDAY DURING THIS TIME AS STRENGTHENING SOUTHWESTERLY FLOW AHEAD OF THE LOW BECOMES ESTABLISHED OVER THE EASTERN CONUS. MAX TEMPS IN THE LOWER 90S APPEAR LIKELY MONDAY AND TUESDAY. LEANED TOWARD THE SLOWER ECMWF SOLUTION REGARDING THE ARRIVAL OF THE FROPA ON TUESDAY. RAISED MAX TEMPS A FEW DEGREES FROM 12Z WPC GUIDANCE AS A SLOWER SOLUTION WOULD KEEP THE PRE-FRONTAL WARM AIRMASS THAT IS CHARACTERIZED BY 850 MB TEMPS NEAR 20C OVER THE AREA INTO TUESDAY. MAX TEMPS IN THE LOWER 90S OVER THE COASTAL MID-ATLANTIC REGION FOR ONE MORE DAY. MONDAY AND TUESDAY BOTH LOOK TO BE A RATHER STORMY PERIOD FOR THE AREA. THE FOCUS FOR CONVECTION APPEARS TO BE A PRE-FRONTAL/LEE TROUGH ON MONDAY AND THE MAIN COLD FRONT FOR TUESDAY. FAVORABLE DYNAMICS IN THE RIGHT ENTRANCE REGION OF AN UNSEASONABLY STRONG UPPER-LEVEL JET STREAK AND AHEAD OF THE APPROACHING LONGWAVE TROUGH ALSO LOOKS TO CONTRIBUTE TO SYNOPTIC LIFT OVER THE AREA ON TUESDAY. THERE ARE STILL PLENTY OF DETAILS THAT NEED TO BE WORKED OUT THIS FAR OUT, BUT THE POTENTIAL IS THERE FOR SEVERE THUNDERSTORM EVENTS BOTH DAYS. SPC HAS DEPICTED THE AREA IN A DAY 6 SLIGHT RISK FOR TUESDAY. COLD FROPA LIKELY TUESDAY NIGHT OR EARLY WEDNESDAY. MUCH COOLER AND DRIER CONDITIONS ARE FORECAST TO RETURN BEHIND THE COLD FRONT BY WEDNESDAY. THE 12Z ECMWF INDICATES H8 TEMPS DROPPING INTO THE SINGLE DIGITS BEHIND THE FRONT. && .AVIATION /20Z THURSDAY THROUGH TUESDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. WE ARE FORECASTING VFR CONDITIONS FOR MOST AREAS THROUGH THE TAF PERIOD. THE EXCEPTION IS MIV/ACY WHERE THERE HAVE BEEN MVFR AND EVEN IFR CIGS/VSBYS ASSOCIATED WITH SHOWERS AND THUNDERSTORMS AND CLOUD COVER FROM THE FRONTAL BOUNDARY OFF THE COAST. THERE COULD BE SOME PATCH FOG OVERNIGHT TONIGHT AS WELL, ESPECIALLY FOR RDG/MIV AND POSSIBLY ACY. THE REST OF THE TAF SITES WE DO NOT ANTICIPATE MUCH FOG POTENTIAL. THERE REMAINS THE POSSIBILITY OF SHOWERS AND THUNDERSTORMS LATE THIS AFTERNOON INTO THIS EVENING, ESPECIALLY FOR SOUTHERN NEW JERSEY AND DELMARVA. WE HAVE KEPT ANY SHRA/TSRA GROUP OUT OF THE TAFS EXCEPT AT MIV/ACY. THERE ARE A SOME SHOWERS/THUNDERSTORMS MOVING ACROSS CENTRAL AND NORTHEASTERN PENNSYLVANIA, BUT WE EXPECT THESE TO MOSTLY DISSIPATE AS THEY APPROACH OUR AREA. IF THEY MAINTAIN THEMSELVES, WE WILL AMEND AS NECESSARY. WINDS WILL GENERALLY BE OUT OF THE EAST TO NORTHEAST TODAY, BEFORE GOING LIGHT AND VARIABLE OVERNIGHT, THEN SETTLING BACK TO A NORTHEAST DIRECTION AGAIN ON FRIDAY. THE NAM SHOWS THE POSSIBILITY OF MVFR/IFR CIGS DEVELOPING OVERNIGHT FOR ACY/MIV, SO WE WILL NEED TO MONITOR THIS IN CASE THIS COMES TO FRUITION. OUTLOOK... FRIDAY NIGHT THRU SATURDAY NIGHT...POTENTIAL FOR IFR CIGS WITH MARINE STRATUS TO IMPACT TERMINALS, PARTICULARLY ACY/MIV, FRIDAY AND SATURDAY NIGHTS WITH ONSHORE FLOW. OTHERWISE VFR EXPECTED WITH DRY CONDITIONS. SUNDAY AND MONDAY...CHANCE FOR SHRA/TSRA BOTH DAYS. BETTER CHANCE MAY BE MONDAY WITH A WELL-DEFINED SFC TROUGH DEVELOPING OVER THE EASTERN SEABOARD. LOCAL/BRIEF RESTRICTIONS POSSIBLE. TUESDAY...BETTER CHANCE FOR SHRA/TSRA TUESDAY AS A COLD FRONT APPROACHES. && .MARINE... SUB-ADVISORY CONDITIONS ARE EXPECTED THROUGH TONIGHT AND FRIDAY WITH A FRONTAL BOUNDARY DRAPED ACROSS THE WATERS. THERE REMAINS A CHANCE FOR SHOWERS AND THUNDERSTORMS THROUGH FRIDAY; EXPECT HIGHER WINDS AND WAVES NEAR THUNDERSTORMS. OUTLOOK... FRIDAY NIGHT THROUGH AND SATURDAY NIGHT...HIPRES BUILDS IN FROM THE NORTHEAST STATES TO START THE WEEKEND. ONSHORE FLOW WILL BE LIGHT. SUNDAY THROUGH TUESDAY...WINDS VEER, BECOMING SOUTHWESTERLY ON SUNDAY. SOUTHWEST WINDS STRENGTHEN MONDAY BUT SHOULD REMAIN BELOW SCA LEVELS. GUSTY SOUTHERLY WINDS AHEAD OF A COLD FRONT ON TUESDAY. MARGINAL SCA POSSIBLE. CHANCE FOR SHRA/TSRA LATE SUNDAY. BETTER CHANCE ON MONDAY AND TUESDAY. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...FLASH FLOOD WATCH UNTIL MIDNIGHT EDT TONIGHT FOR NJZ016- 021>024. DE...FLASH FLOOD WATCH UNTIL MIDNIGHT EDT TONIGHT FOR DEZ001>004. MD...FLASH FLOOD WATCH UNTIL MIDNIGHT EDT TONIGHT FOR MDZ008-012- 015-019-020. MARINE...NONE. && $$ SYNOPSIS...KLEIN NEAR TERM...ROBERTSON SHORT TERM...ROBERTSON LONG TERM...KLEIN/MIKETTA AVIATION...KLEIN/ROBERTSON MARINE...KLEIN/ROBERTSON

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