Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 301948 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 348 PM EDT THU APR 30 2015 .SYNOPSIS... LOW PRESSURE NEAR THE COAST OF THE SOUTHEASTERN STATES WILL MOVE NORTHEASTWARD THOUGH FRIDAY. HIGH PRESSURE WILL THEN BUILD IN BEHIND THE DEPARTING LOW FOR THE WEEKEND AND INTO EARLY NEXT WEEK. A COLD FRONT WILL APPROACH ON TUESDAY AND MAY STALL OVER OUR REGION BY THE MIDDLE OF NEXT WEEK. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... A BACKDOOR COLD FRONT LOCATED OVER NEW ENGLAND WILL CONTINUE MOVING SOUTHWEST TOWARD THE REGION. ALSO, LOW PRESSURE WILL BE ORGANIZING ALONG THE SOUTHEAST COAST WITH ANOTHER UPPER LEVEL LOW PRESSURE APPROACHING FROM THE GREAT LAKES AND OHIO VALLEY. THESE FEATURES WILL RESULT IN A INCREASE IN CLOUDS ACROSS THE REGION THROUGHOUT THE NIGHT. WITH THE FRONTAL PASSAGE NORTHWEST WINDS UNDER 10 MPH WILL SHIFT TO MORE EASTERLY AND BRING IN A COOLER AIRMASS TO THE REGION. THE INCREASE IN CLOUDS WILL LIKELY LIMIT RADIATIONAL COOLING SOME TONIGHT, NOT EXPECTING A RAPID DROP IN TEMPERATURES WITH LOWS STILL GETTING DOWN TO ABOUT 50 ON AVERAGE. MET/MAV/ECMWF CONSENSUS USED. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH 6 PM FRIDAY/... THE UPPER AIR LOW AND COASTAL LOW WILL BOTH BE MOVING TOWARD THE REGION ON THURSDAY. HOWEVER, THE UPPER AIR LOW WILL GRADUALLY TRANSITION TO THE COASTAL LOW LEADING TO THE MAJORITY OF THE MOISTURE AND SHOWER ACTIVITY ONLY CLIPPING AREAS SOUTH AND WEST OF PHILLY. EASTERLY WINDS WILL CONTINUE WITH THE POTENTIAL FOR A FEW GUSTS AROUND 20 MPH, ON AVERAGE THE GUIDANCE LOOKS A LITTLE LOW COMPARED TO SOUNDING ANALYSIS. NEEDED QPF LOOKS RATHER LIGHT AS WELL, NOT ENOUGH TO ACCOUNT FOR SHORT TERM DEFICITS (UNDER .1 INCHES). HIGH TEMPERATURES MAY END UP FAIRLY UNIFORM AREAS CLOSER TO NYC LOOK TO SEE MORE SUN BUT ARE MORE ENTRENCHED IN THE COOLER AIRMASS. LOCATIONS FURTHER SOUTHWEST WILL SEE MORE IN THE WAY OF SCATTERED SHOWERS TO KEEP TEMPERATURES IN CHECK. ADJUSTED THE MET/MAV/ECMWF CONSENUS TO ACCOUNT FOR THIS. OVERALL COOLER AND IN THE 60`S FOR MOST. && .LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/... 5-WAVE MODEL GUIDANCE SHOWS THE LONGWAVE TROUGH CONTINUING TO LIFT TOWARDS THE NORTHEAST AND BETTER ESTABLISHED SOUTHEAST RIDGING BEGINS TO OVERTAKE THE REGION. BY MID-NEXT WEEK THE FLOW ALOFT BECOMES MORE ZONAL ALLOWING A FEW EMBEDDED DISTURBANCES TO PASS THROUGH ADDING TO SOME UNSETTLED WEATHER. SATURDAY...WEAK RIDGING ALOFT MAY NOT HAVE ENOUGH OF A CAP TO PREVENT SOME LOW-TOPPED SHOWERS WITH EMBEDDED THUNDER POSSIBLE SATURDAY AFTERNOON AS THE LAST WAVE OF MID-LEVEL ENERGY PASSES THROUGH. THE PLACEMENT AND MOVEMENT OF THE ENERGY SHOULD STAY MORE TOWARDS OUR WEST AS IT HEADS TOWARDS THE SOUTHEAST SO WE KEEP THE ISOLATED SHOWERS/THUNDER IN THE HIGHER TERRAIN WITH SOME DIFFERENTIAL HEATING OF THE RIDGES EXPECTED. OTHERWISE A MOSTLY DRY DAY IS EXPECTED WITH A DIURNAL CU FIELD FORMING AS TEMPERATURES CLIMB BACK TOWARDS NORMAL. SUNDAY - MONDAY...A BETTER WARMING TREND EXPECTED WITH A BUILDING SOUTHEAST U.S. RIDGE. 850MB TEMPERATURES CLIMB TOWARDS THE DOUBLE DIGIT MARK BY MONDAY WITH A MORE PRONOUNCED RETURN FLOW SETTING UP. TEMPERATURES BOTH DAYS ARE EXPECTED TO BE ABOVE NORMAL WITH MONDAY FLIRTING WITH THE 80F MARK. THINGS SHOULD BE PRETTY WELL CAPPED SO EXPECT A DRY PERIOD DURING THIS TIMEFRAME. TUESDAY - THURSDAY...A WEAK LOW PRESSURE SYSTEM PUSHES A DECAYING COLD FRONT THROUGH THE REGION TUESDAY INTO WEDNESDAY. STILL MAINTAIN THE LOW END CHANCE POPS AT THIS TIME BUT ALSO INTRODUCE A SLIGHT CHANCE OF CONVECTION WITH THE ABOVE AVERAGE TEMPERATURES EXPECTED ON BOTH DAYS. THE FRONT MAY STALL FOR A TIME HEADING INTO THURSDAY AS THE FLOW ALOFT BECOMES PARALLEL TO IT BUT SHOULD BEGIN TO MOVE SOUTHWARD LATE IN THE PERIOD. && .AVIATION /19Z THURSDAY THROUGH TUESDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. REST OF THIS AFTERNOON... VFR,SCATTERED MID-LEVEL CLOUDS NW WIND GUST UNDER 20KT. COASTAL SEA BREEZES DEVELOPING THIS AFTERNOON. ONLY MODERATE CONFIDENCE WE WILL SEE WINDS SHIFT DUE TO SEABREEZE AT ILG AND ACY. TONIGHT... VFR, WINDS SHIFTING TO NORTHEAST UNDER 10 KNOTS BY MORNING. SCATTERED AND BROKEN MID-LEVEL CLOUDS. THURSDAY... CLOUDS BECOMING BROKEN AND LOWERING SOME TO AROUND 5,000 FT THROUGHOUT THE DAY. SOME POTENTIAL FOR LOWERING TO MVFR CEILINGS LATE IN THE DAY, LOW CONFIDENCE OF MVFR CEILINGS. ANY SHOWER CHANCE TO SPOTTY FOR TAF MENTION ATTM. SOME EASTERLY WIND GUSTS 15-20 KNOTS IN THE AFTERNOON. OUTLOOK... SATURDAY...MOSTLY VFR. ISOLATED SHOWERS/THUNDER POSSIBLE AROUND RDG/ABE WITH LOWER CHANCES FARTHER EAST. LIGHT NORTHERLY WINDS EXPECTED. SUNDAY - MONDAY...VFR EXPECTED WITH HIGH PRESSURE MOVING IN. TUESDAY...MOSTLY VFR. SCATTERED SHOWERS AND THUNDERSTORMS POSSIBLE AS A COLD BEGINS TO SLIDE THROUGH THE REGION BY THE AFTERNOON HOURS. && .MARINE... SEAS AND WINDS LOOK TO STAY UNDER SCA CRITERIA THROUGHOUT. WITH THE APPROACH OF A LOW PRESSURE SYSTEM TO OUR SOUTHEAST SEAS WILL BUILD TO AROUND FOUR FEET. A WIND SHIFT FROM NORTHWESTERLY TO EASTERLY IS ALSO EXPECTED LATE TONIGHT. WIND GUSTS AROUND 20 KNOTS ARE ALSO POSSIBLE IN THE AFTERNOON. OUTLOOK... SATURDAY...WE CONTINUE THE SCA SEAS THROUGH SATURDAY MORNING BEFORE CONDITIONS DROP BELOW AS THE CENTER OF THE HIGH PRESSURE MOVES OVERHEAD. PRIMARILY LIGHT N-NW WINDS EXPECTED. SUNDAY - TUESDAY...SUB-SCA CONDITIONS EXPECTED AS HIGH PRESSURE MOVES OFFSHORE. SOUTHERLY WINDS COMMENCE WITH A BIT OF AN INCREASE IN SEAS BY TUESDAY. && .TIDES/COASTAL FLOODING... WITH THE FULL MOON APPROACHING THIS WEEKEND, 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 ON FRIDAY. 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, THE EARLY FRIDAY MORNING 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 5 AM EDT SATURDAY FOR ANZ451>455. SMALL CRAFT ADVISORY UNTIL 6 PM EDT FRIDAY FOR ANZ431-450. && $$ SYNOPSIS...FRANCK NEAR TERM...GAINES SHORT TERM...GAINES LONG TERM...HEAVENER AVIATION...GAINES/HEAVENER MARINE...GAINES/HEAVENER TIDES/COASTAL FLOODING...GIGI

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