Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 220114 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 914 PM EDT SUN SEP 21 2014 .SYNOPSIS... LOW PRESSURE OFF THE MID-ATLANTIC COAST WILL MOVE NORTHEASTWARD AND AWAY FROM THE REGION THROUGH TONIGHT. MEANWHILE, A COLD FRONT OVER THE OHIO VALLEY THIS AFTERNOON WILL MOVE THROUGH OUR AREA TONIGHT. A LARGE AREA OF HIGH PRESSURE BUILDS IN FROM THE MIDWEST EARLY IN THE WEEK. THE HIGH IS EXPECTED TO PARK OVER THE NORTHEAST STATES THROUGH THE REMAINDER OF THE WEEK. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
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A CDFNT WAS APPROACHING FROM THE W AN A BROKEN AREA OF SHWRS WITH A FEW EMBEDDED LIGHTNING STRIKES WAS EVIDENT ON RADAR. IT APPEARS TO BE HOLDING TOGETHER AT IT MOVES EWD. THE HRRR INDICATES AT LEAST SOME PORTION OF THE PRECIP WILL SURVIVE INTO THE ERN PORTIONS OF OUR CWA. SO HAVE UPPED THE POPS INTO NJ, BUT NOT ALL THE WAY TO THE CST JUST YET. STILL THINK WITH LOSS OF DAYTIME HEATING AND NOT MUCH DYNAMICS TO WORK WITH THERE COULD BE SOME WEAKENING WITH TIME. WINDS WILL SHIFT TO WRLY/NWRLY BEHIND THE FRONT. DRIER AIR WILL OVERSPREAD THE AREA BY MORNING. LOWS WILL DIP INTO THE LOW.MID 50S NORTH/WEST TO THE UPPER 50S/LOW 60S SOUTH/EAST.
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&& .SHORT TERM /6 AM MONDAY MORNING THROUGH 6 PM MONDAY/... A PLEASANT FALL-LIKE DAY IS EXPECTED ACROSS THE REGION MONDAY AS COOL AND DRIER AIR CONTINUES TO BUILD OVER THE AREA. A GUSTY W/NW WIND WILL BE IN PLACE EARLY AND CONTINUE THROUGH THE AFTERNOON. WINDS GUSTS OF 20 TO 25 MPH ARE EXPECTED. HIGH TEMPERATURES MONDAY WILL BE MOSTLY IN THE UPPER 60S/LOW 70S ACROSS THE AREA...WITH THE NRN MOST AREAS ONLY HAVING HIGHS IN THE UPPER 50S (MOUNT POCONO) TO THE MID 60S. DEW POINTS MOSTLY IN THE LOW/MID 40S. && .LONG TERM /MONDAY NIGHT THROUGH SUNDAY/... EXPANSIVE AREA OF HIGH PRESSURE OVER THE MIDWEST WILL BUILD EASTWARD INTO MID-ATLANTIC REGION STATES MONDAY NIGHT AND TUESDAY. MEANWHILE, A SOUTHERN PIECE OF ENERGY ASSOCIATED WITH THE UPPER LOW THAT IS CURRENTLY OVER THE GREAT LAKES REGION IS FORECAST TO LAG BEHIND THE MAIN UPPER TROUGH AND POTENTIALLY DEVELOP INTO A CLOSED LOW OVER THE SOUTHEAST STATES. A CAA REGIME WILL BECOME ESTABLISHED OVER OUR REGION DURING THIS TIME UNDER NORTHWEST FLOW. MINIMAL CLOUD COVER AND BELOW NORMAL TEMPS ARE EXPECTED. TEMPS MONDAY NIGHT MAY DIP INTO THE UPPER 30S IN THE POCONOS BUT THE NW WINDS OVERNIGHT SHOULD PRECLUDE ANY FROST FROM FORMING. WITH H8 TEMPS IN THE SINGLE DIGITS, MAX TEMPS ON TUESDAY WILL STRUGGLE TO REACH 70F. HIGH PRESSURE WILL RETREAT NORTHEASTWARD INTO NEW ENGLAND TUESDAY NIGHT AND REMAIN ANCHORED THERE THROUGH THE END OF THE WEEK. FORECAST UNCERTAINTY DECREASES DURING THE SECOND HALF OF THE WEEK AS MODELS HAVE HAD A DIFFICULT TIME COMING TO AGREEMENT REGARDING WHAT HAPPENS WITH THE ABOVE MENTIONED DISTURBANCE OVER THE SOUTHEAST STATES. OVER THE PAST FEW DAYS, THE ECMWF AND GEM CONTINUE TO ADVERTISE A STRONGER DISTURBANCE DRIFTING UP THE MID-ATLANTIC COAST LATE IN THE WEEK, WHICH WOULD BRING RAIN TO SOUTHERN PORTIONS OF THE AREA THURSDAY AND POSSIBLY INTO FRIDAY. MEANWHILE, THE OPERATIONAL GFS AND JUST ABOUT ALL OF ITS GEFS MEMBERS (INCLUDING THE LATEST 12Z RUN) HAS BEEN PERSISTENT IN SUPPRESSING THE DISTURBANCE FAR ENOUGH TO THE SOUTH AND EAST TO KEEP US DRY. THIS HAS A LOW PREDICTABILITY PATTERN WRITTEN ALL OVER IT GIVEN THE WEAK STEERING FLOW THE LOW WILL ENCOUNTER UNDERNEATH THE UPPER RIDGE. OPTED TO CLOSELY FOLLOW THE LATEST WPC GUIDANCE, WHICH PREFERRED AN IN-BETWEEN SCENARIO USING THE 00Z ECMWF ENSEMBLE MEAN. FORECAST WAS RATHER CONSERVATIVE WITH SLIGHT CHANCE POPS CONFINED TO THE DELMARVA AND SOUTHERN NJ. REGARDLESS OF WHICH SOLUTION PANS OUT, THE SETUP OF HIGH PRESSURE TO OUR NORTHEAST AND LOW PRESSURE TO OUR SOUTH WILL RESULT IN PERSISTENT FLOW OFF THE ATLANTIC OCEAN, SEASONABLY COOL TEMPS AND INCREASING CLOUD COVER. THE COASTAL DISTURBANCE IS FORECAST TO MOVE OFFSHORE BY THE WEEKEND WHILE HIGH PRESSURE BUILDS BACK INTO THE AREA. STRENGTHENING SUBSIDENCE FROM THE HIGH OVERHEAD WOULD YIELD A WARMING TREND WITH HIGHS POTENTIALLY NEAR 80F BOTH DAYS THIS WEEKEND. && .AVIATION /01Z MONDAY THROUGH FRIDAY/...
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THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. VFR CONDS ARE GENLY EXPECTED. HOWEVER, THERE IS A BKN LINE OF SHWRS MOVG ACRS ERN PA ATTM. THIS LINE COULD BRIEFLY DROP CIGS/VSBYS INTO THE MVFR OR EVEN IFR RANGE. STILL SOME UNCERTAINTY AS TO HOW FAR E THIS PRECIP WILL GET. HAVE ADDED SOME BRIEF SHRA/MVFR AT KPHL...KPNE AND KTTN. BEHIND THE FRONT WINDS WILL SHIFT TO WRLY/NWRLY AND SKIES WILL BECOME MOSTLY CLR. MON...VFR WITH A GUSTY WNW WIND THRU THE DAY. OUTLOOK... MONDAY NIGHT THROUGH TUESDAY NIGHT...VFR UNDER MAINLY SKC AND LIGHT NORTHWEST WINDS. WEDNESDAY AND WEDNESDAY NIGHT...ONSHORE FLOW DEVELOPS. EXPECT STRATOCU TO INCREASE AS MARINE LAYER DRAWS INLAND. SOME POTENTIAL FOR MVFR CIGS ESPECIALLY CLOSER TO THE COAST. THURSDAY AND FRIDAY...LOWER THAN NORMAL FORECAST CONFIDENCE AS LOPRES OVER THE SOUTHEAST STATES DRIFTS NORTHWARD. SUB-VFR CONDITIONS AND LIGHT RA COULD OCCUR (PARTICULARLY SOUTHERN TERMINALS) IF THE LOW TRACKS FAR ENOUGH NORTH, WHICH IS STILL UNCERTAIN ATTM.
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&& .MARINE... WINDS ARE BEGINNING TO SWITCH AROUND TO NW BEHIND THE DEPARTING LOW OFFSHORE. THE WINDS WILL REMAIN MOSTLY AROUND 10 KTS AND THEN SWITCH MORE SWRLY THIS EVENING...BEFORE A COLD FRONT CROSSES THE WATERS OVERNIGHT. WINDS BEHIND THE FRONT WILL SHIFT WRLY...THEN NWRLY AND INCREASE TO 10 TO 20 KTS WITH SOME GUSTS AROUND 25 KTS. SEAS ON THE OCEAN WILL BUILD TO AROUND 5 FT OVERNIGHT. WE HAVE ISSUED A SCA FLAG FOR THE OCEAN WATERS AND LOWER DEL BAY TO COVER THE EXPECTED CONDITIONS. WINDS/SEAS WILL BEGIN TO SUBSIDE BY AROUND NOON MONDAY...SO WE WILL SET THE EXPIRATION TIME TO THAT FOR NOW...ITS POSSIBLE IT MAY NEED TO BE EXTENDED A FEW HOURS HOWEVER. OUTLOOK... MONDAY NIGHT...BREEZY NW FLOW CONTINUES AS HIPRES BUILDS INTO THE WATERS. CAPPED WINDS AROUND 20 KT, BUT STILL SOME POTENTIAL FOR A SCA IF THE PRESSURE GRADIENT WINDS UP BEING A TAD STRONGER THAN INDICATED BY THE LATEST GUIDANCE. TUESDAY AND TUESDAY NIGHT...NW WINDS DIMINISH TUESDAY BEFORE SHIFTING OUT OF THE NE TUESDAY NIGHT. WEDNESDAY AND WEDNESDAY NIGHT...NE WINDS STRENGTHEN TO NEAR SCA CRITERIA ON WEDNESDAY. IN RESPONSE TO THE FLOW, SEAS ARE FORECAST TO BUILD TO AROUND 5 FT BY WEDNESDAY NIGHT. THURSDAY THROUGH FRIDAY...FOUR TO SIX FT SEAS MAY CONTINUE THRU THURSDAY NIGHT OR FRIDAY DESPITE A WEAKER ONSHORE FLOW. SCA MAY BE NEEDED. && .RIP CURRENTS...
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A MODERATE RISK OF RIP CURRENTS IS BEING FORECAST FOR MONDAY.
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&& .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...SMALL CRAFT ADVISORY FROM MIDNIGHT TONIGHT TO NOON EDT MONDAY FOR ANZ431-450>455. && $$ SYNOPSIS...KLEIN NEAR TERM...NIERENBERG/O`HARA SHORT TERM...O`HARA LONG TERM...KLEIN AVIATION...KLEIN/NIERENBERG/O`HARA MARINE...KLEIN/O`HARA

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