Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 011348 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 948 AM EDT FRI MAY 1 2015 .SYNOPSIS... LOW PRESSURE NEAR THE COAST OF THE SOUTHEASTERN STATES WILL CONTINUE TO PUSH FURTHER AWAY FROM THE COAST THROUGH THE WEEKEND. IN ITS WAKE, HIGH PRESSURE WILL BUILD IN AND REMAIN OVER THE REGION THROUGH MONDAY. A COLD FRONT WILL APPROACH ON TUESDAY AND MAY STALL OVER OUR REGION BY THE MIDDLE OF NEXT WEEK. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... ADJUSTMENTS TO THE ESTF BASED ON LATEST RADAR TRENDS AND HRRR/RAP. SHIFT IN POP ADJUSTMENT IS TO LOWER IT SOUTHEAST WHERE PCPN IS REMAINING JUST SOUTH OF OUR CWA AND INCREASE NW WHERE MESOSCALE MODELS HAVE UPSLOPE FLOW AND RELATIVELY LOWER INSTABILITY. MORNING SOUNDINGS ARE SUPPORTING MAX TEMPS, SO NOT MUCH OF AN ADJUSTMENT MADE THERE. AN UPR LOW OVER NC WILL MOVE EWD AND OFF THE CST TODAY. AS IT MOVES EWD IT WILL CAUSE A SFC LOW OFF THE CAROLINA CST TO BE PUSHED FURTHER OUT TO SEA. WITH THE NELY FLOW CONTINUING, IT WILL FEEL COOL ONCE AGAIN, WITH TEMPS STRUGGLING TO MAKE THE LWR 60S, AND REMAINING IN THE 50S IN MANY AREAS. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SATURDAY/... ANY PRECIP SHUD WIND DOWN TONIGHT, THE WIND WILL BECOME MORE NLY AS THE UPR LOW AND SFC LOW MOVE OFF THE CST AND HIGH PRES BEGINS TO SLOWLY BUILD IN BY DAYBREAK SAT. CLOUDS SHOULD DECREASE BY THE END OF THE PD. && .LONG TERM /SATURDAY THROUGH THURSDAY/... AN UPPER LEVEL ZONAL FLOW PATTERN LOOKS TO BE SETTING UP FOR MUCH OF THE LONG TERM. SATURDAY THROUGH SUNDAY...THE COASTAL TROUGH CONTINUES TO PULL AWAY FROM OUR REGION, AND IN ITS WAKE, A PAIR OF UPPER LEVEL SHORT WAVE RIDGES SLIDE OVER OUR REGION. AT THE SURFACE, A BROAD HIGH WILL SLOWLY PROPAGATE EAST THROUGH THIS TIME. WITH SYNOPTIC SCALE SUBSIDENCE, EXPECT MOSTLY DRY CONDITIONS. HOWEVER, AS THE PREVIOUS SHIFT NOTED, THERE IS A VERY WEAK SHORT WAVE TROUGH AT 500 MB EXPECTED ON SATURDAY, WHICH, COMBINED WITH TERRAIN INDUCED DIFFERENTIAL HEATING, COULD BE ENOUGH FOR A FEW STORMS TO INITIATE. AS FOR TEMPERATURES, THE LARGER SCALE PATTERN WITH INCREASING THICKNESSES WILL ALLOW FOR A SIGNIFICANT WARMING TREND ESPECIALLY GOING INTO SUNDAY. MONDAY LOOKS TO BE THE WARMEST DAY OF THE WEEK. THICKNESS VALUES INCREASE AGAIN, LEADING TO CONTINUED WARMING FROM SUNDAY. AS A RESULT, A FEW LOCATIONS MAY EVEN REACH 80 DEGREES ON MONDAY. TUESDAY THROUGH THURSDAY...THE BIG QUESTION THROUGH THIS PERIOD WILL BE HOW QUICKLY AND HOW FAR SOUTH THE COLD FRONT DIGS. ZONAL FLOW, SUGGESTING A SLOWER SOUTHWARD PROGRESSION OF THE FRONT, SHOULD PERSIST THROUGH AT LEAST EARLY TUESDAY, BUT THEN WE SEE A TRANSITION BACK TO A SLIGHTLY MORE MERIDIONAL PATTERN AS THE FRONT LOOKS TO SLIDE INTO OUR REGION AND THEN STALL. FRIDAY...BOTH THE GFS AND ECMWF ARE DEPICTING ANOTHER COASTAL LOW DEVELOPING OFF OF THE FL COAST AND BEGINNING TO LIFT NE. HOWEVER, AS WE HAVE SEEN WITH THIS CURRENT COASTAL LOW, MODEL SKILL WITH THE EXACT TRACK OF THIS LOW THIS FAR OUT IS QUITE UNCERTAIN. THEREFORE, HAVE STAYED CLOSE TO GUIDANCE AND KEPT THE FORECAST DRY FOR NOW. && .AVIATION /14Z FRIDAY THROUGH TUESDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. 12Z TAFS VFR THROUGHOUT. THIS MORNING...A LOWER VFR CIG EXPECTED TO DEVELOP. NORTHEAST WINDS WILL AVERAGE CLOSE TO 10 KNOTS WITH GUSTINESS AVERAGING 15 TO 20 KTS FROM THE KPHL TERMINAL EAST AND SOUTHEAST AT OTHER TERMINALS AND AIRPORTS. THIS AFTERNOON...VFR CIG CONTINUING. WINDS SLOWLY VEERING TO THE EAST AND SOUTHEAST. SPEEDS SHOULD AVERAGE SLIGHTLY LOWER THAN THIS MORNING WITH MOST GUSTINESS ENDING. SOME GUSTS MIGHT LINGER AT COASTAL AIRPORTS. WIDELY SCATTERED SHOWERS EXPECTED INLAND, BUT TOO LOW A COVERAGE TO INCLUDE AT THE TERMINALS. TONIGHT...GENERAL VFR CIG DURING THE EVENING EITHER LIFTING OR DISSIPATING OVERNIGHT. WINDS SHOULD BACK MORE TO THE NORTH AND BECOME LIGHT. NO VSBY RESTRICTIONS EXPECTED. OUTLOOK... SATURDAY...MOSTLY VFR. MVFR WITH ISOLATED THUNDERSTORMS POSSIBLE AROUND KRDG AND KABE. SUNDAY - MONDAY...VFR EXPECTED WITH HIGH PRESSURE MOVING IN. TUESDAY...MOSTLY VFR WITH LOCALIZED MVFR POSSIBLE WITH SCATTERED SHOWERS AND THUNDERSTORMS. && .MARINE... THE SCA WILL BE CANCELLED FOR ZONE 450 AS WINDS HAVE DECREASED AND LATEST WAVE WATCH GUIDANCE DOES NOT BRING SEAS UP TO 5 FEET THAT NORTH. THE SCA FLAG WILL REMAIN IN PLACE ELSEWHERE AND HAS BEEN EXTENDED THRU 12Z SAT. LATEST GUID IS HIGH BASED ON WHAT IS CURRENTLY OCCURRING (WRT WIND AND SEAS) BUT WITH THE UPR LOW YET TO MOVE THRU, I AM HESITANT TO MAKE ANY CHANGES. CONFIDENCE REMAINS LOW. OUTLOOK... SATURDAY...SEAS NEAR OR ABOVE 5 FT MAY LINGER THROUGH SATURDAY MORNING AND AFTERNOON. HOWEVER, SO FAR, GUIDANCE HAS BEEN TOO HIGH WITH SEAS SO HAVE HELD OFF ON EXTENDING THE SCA INTO SATURDAY FOR NOW UNTIL WE SEE IF THE HIGHER SEAS DEVELOP. SUNDAY THROUGH TUESDAY...WINDS AND SEA SHOULD REMAIN BELOW SCA CRITERIA. WIND GUSTS NEAR OR JUST ABOVE 20 KT ARE POSSIBLE MONDAY NIGHT INTO TUESDAY. && .TIDES/COASTAL FLOODING... WITH THE FULL MOON ON SATURDAY, ASTRONOMICAL TIDES WILL BE INCREASING. COUPLED WITH THE ONSHORE FLOW AROUND THE DEPARTING COASTAL LOW, TIDAL DEPARTURES SHOULD REMAIN ABOVE NORMAL. THEY ARE CURRENTLY AVERAGING CLOSE TO ONE FOOT ABOVE NORMAL. THE FORECAST APPROACH WITH THE COASTAL SYSTEM IS TO TAKE A GENERAL MODEL CONSENSUS. GIVEN THAT THE CURRENT GFS RUN REMAINS THE MOST ROBUST (THUS ITS SURGE GUIDANCE ALSO). IT ONLY BARELY HAS THE SOUTHERN AREAS REACHING MINOR TIDAL FLOODING LEVELS DURING THE EARLY EVENING HIGH TIDE TODAY. WHILE WE WILL CONTINUE TO MONITOR THE DEVELOPMENT OF THIS COASTAL LOW, PRESENT TRENDS AND INDICATIONS ARE THAT WE SHOULD REMAIN BELOW COASTAL FLOOD ADVISORY THRESHOLDS. BACKING UP, THIS MORNINGS ASTRONOMICAL HIGH TIDE CYCLE IS LOWER, SO NO ISSUES ARE EXPECTED WITH THAT ONE. THE LOW PRESSURE SYSTEM SHOULD BE SUFFICIENTLY OFFSHORE TO NOT BE THE CAUSE OF ANY SUBSEQUENT TIDAL ISSUES ON THE WEEKEND. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 8 AM EDT SATURDAY FOR ANZ451>455. SMALL CRAFT ADVISORY UNTIL 6 PM EDT THIS EVENING FOR ANZ431. && $$ SYNOPSIS...JOHNSON NEAR TERM...GIGI/NIERENBERG SHORT TERM...NIERENBERG LONG TERM...JOHNSON AVIATION...GIGI/JOHNSON MARINE...JOHNSON/NIERENBERG TIDES/COASTAL FLOODING...

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