Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 102347 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 747 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/... BACKDOOR COLD FRONT HAS CLEARED OUR CWA. BUT WITH TROFFING ALOFT, THERE IS STILL SUFFICIENT INSTABILITY FOR SHOWERS AND THUNDERSTORMS TO FORM. IF 7/8/14 WAS THE DAY THE HRRR AND COSPA RAN TO THEIR AGENT AND RENEGOTIATE THEIR CONTRACTS, TODAY IS THE DAY TO BE THANKFUL THE REVERSE CANT BE DONE. DIFFICULT MORE SUBTLE SCENARIO WITH NONE OF THE MESOSCALE MODELS HANDLING/VERIFYING CONVECTION WELL AND FALLING OFF TRACK RATHER QUICKLY WITHIN OUR CWA. WITH SHORT WAVES STILL PROGGED TO PROGRESS THROUGH THE TROF, SFC BASED INSTABILITY EXCEEDING 2K JOULES WEST, BOUNDARIES PROVIDING LIFT, WE ARE GOING TO KEEP THE PRESENT FORECAST, WATCH, GOING UNTIL WE SEE WHAT COMES OF THE CONVECTION EXITING THE ALLEGHENIES. ANY ESTF UPDATES ARE GOING TO BE BASED ON ADJUSTING FOR TEMPS WHERE PCPN IS OR JUST RECENTLY HAS OCCURRED. 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. 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 /00Z FRIDAY THROUGH TUESDAY/...
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THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. 00Z TAFS CARRY SOME MVFR CONDITIONS INLAND AT FOGGIER TERMINALS AND IFR CIGS AT COASTAL TERMINALS LATER TONIGHT. FOR THIS EVENING, CONVECTION IN THE SUSQUEHANNA VALLEY IS ONLY SLOWLY DRIFTING EASTSOUTHEAST. SHOWERS INCLUDED AT KRDG INITIALLY, ALTHOUGH KILG MIGHT NEED AN AMENDMENT IF THEY STAY TOGETHER LONGER THAN ANTICIPATED. OTHERWISE NON COASTAL TERMINALS SHOULD HAVE VFR CONDITIONS WITH MAINLY MID LEVEL CIGS OR HIGHER AND LIGHT EAST WINDS. AT THE COAST, CONFIDENCE IS LESS THAN AVERAGE, BUT WITH RAIN OFFSHORE AND ONSHORE WIND, WE ARE PREDICTING AN IFR CIG TO FORM AT THE TERMINALS. OVERNIGHT, PRIMARILY VFR CONDITIONS WITH SOME MVFR RESTRICTIONS DUE TO FOG AT SMALLER AIRPORTS AND TERMINALS. ANY CIG SHOULD BE VFR MID LEVEL OR HIGHER. WINDS WILL BE LIGHT. AT THE COASTAL TERMINALS (KACY AND KMIV), WE WILL CONTINUE THE IFR CIG WITH SOME MVFR VSBY RESTRICTIONS. CONFIDENCE LESS THAN AVERAGE. ON FRIDAY VFR CONDITIONS EXPECTED OR WILL BE REACHED (AT THE COASTAL TERMINALS) AT ALL AIRPORTS DURING THE MORNING. PCPN CHANCES OVERALL ARE LESS THAN TODAY AND NO MENTION WILL BE MADE. SOME CUMULUS CLOUDS SHOULD FORM, BUT NOT EXPECTING A VFR CIG. WINDS WILL BE LIGHT FROM THE EAST AND A BAY AND SEA BREEZE FRONT SHOULD FORM. NOT SURE IF A VERY SHARP DISCONTINUITY WILL FORM AS THE GENERAL WIND FIELD SHOULD BE FROM THE EAST. 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.
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&& .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...GIGI/ROBERTSON SHORT TERM...ROBERTSON LONG TERM...KLEIN/MIKETTA AVIATION...GIGI/KLEIN MARINE...KLEIN/ROBERTSON

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