Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
-- Remove Highlighting --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS61 KPHI 030127 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 927 PM EDT SUN AUG 2 2015 .SYNOPSIS... A HIGH PRESSURE SYSTEM OVER THE CENTRAL APPALACHIANS WILL GRADUALLY MOVE SOUTHEAST THROUGH MONDAY. A COLD FRONT FROM THE GREAT LAKES IS FORECAST TO CROSS OUR REGION EARLY TUESDAY WITH A SECONDARY COLD FRONT FOLLOWING EARLY WEDNESDAY. THIS FRONT WILL STALL JUST SOUTH OF OUR AREA THROUGH THE END OF THE WEEK AS WAVES OF LOW PRESSURE MOVE ALONG IT. THE LAST AND STRONGEST WAVE OF LOW PRESSURE SHOULD PASS OFFSHORE ON SATURDAY WITH A HIGH PRESSURE SYSTEM FROM EASTERN CANADA BUILDING SOUTHWARD ON SUNDAY. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
-- Changed Discussion --
NO CHANGES NEEDED TO THE EARLIER FCST. HIGH PRESSURE AFFECTING THE AREA WILL WEAKEN OVERNIGHT. QUIET WEATHER CONTINUES TO BE EXPECTED AS THERE ARE NO SHORT WAVE IMPULSES EXPECTED TO CREATE ANY SHOWER ACTIVITY OVERNIGHT. CLEAR SKIES OVERNIGHT SHOULD ALLOW FOR ANOTHER DECENT RADIATIONAL COOLING NIGHT WITH CALM WINDS, ALTHOUGH NOT LIKELY AS COOL AS LAST NIGHT. OVERNIGHT LOWS ARE A BLEND OF MAV/MET MOS AND MOSGUIDE.
-- End Changed Discussion --
&& .SHORT TERM /6 AM MONDAY MORNING THROUGH 6 PM MONDAY/... ON MONDAY, A COLD FRONT WILL BE ADVANCING THROUGH WESTERN AND CENTRAL PENNSYLVANIA AS AN AREA OF LOW PRESSURE LIFTS INTO EASTERN CANADA. THE FRONT WILL NOT MAKE ITS WAY INTO THE AREA DURING THE DAYTIME PERIOD, BUT A PRE-FRONTAL/LEE-SIDE TROUGH WILL DEVELOP ACROSS THE MID ATLANTIC REGION. MOST OF THE AREA IS EXPECTED TO BE DRY THROUGH THE DAY MONDAY, HOWEVER, ISOLATED SHOWERS/THUNDERSTORMS MAY DEVELOP LATE IN THE DAY ACROSS THE NORTHWEST PORTIONS OF THE AREA AS A SHORT WAVE/VORTICITY IMPULSE MOVES INTO THE AREA. MONDAY WILL BE A FEW DEGREES WARMER THAN SUNDAY, WITH EVERYONE BEING ABOVE NORMAL ONCE AGAIN. HIGH TEMPERATURES ARE A BLEND OF MIXED 925MB ECMWF TEMPS, MAV/MET MOS, AND MOSGUIDE. && .LONG TERM /MONDAY NIGHT THROUGH SUNDAY/... THE WRF-NMMB/NAM INITIALIZATION LOOKED BETTER AT 500MB IN THE EAST, BUT THE GFS WAS BETTER IN THE WEST. THE NEVADA ENERGY OVERALL TRENDED WEAKER WITH THE WRF-NMMB STILL TOO STRONG WITH IT. THERMALLY THE WRF/NAM WAS BETTER AT 850MB (GFS INITIALIZED TOO WARM) AND A COMBINATION OF THE WRF (TOO COOL) AND GFS (TOO WARM) WORKED BEST AT 925MB. DP/DT, THE WEST COAST TROF WAS NOT AS STRONG, THIS MAY BE WHY SOME MORE PROGRESSIVE SOLUTION HAVE OCCURRED WITH THE 12Z RUNS. IN ADDITION, THE MODEL RUNS THAT HAVE LESS FEEDBACK VORTS ALSO OFFERED FASTER SOLUTIONS. THE OP GFS WAS FASTER THAN THE GEFS MEAN AND WAS NOT USED. ON THE OPPOSITE END OF THE SPECTRUM, THE NAVY NOGAPS HAS SATURDAY AS THE DAY WITH THE HEAVIEST RAIN. WE HAVE GONE CLOSEST WITH THE 12Z ECMWF AS ITS CLOSEST TO A MODEL COMPROMISE AND WPC GUIDANCE. MODEL DIFFERENCES START FROM THE GET GO ON MONDAY NIGHT WITH THE GFS REMAINING MOST BULLISH WITH CARRYING CONVECTION TO THE COAST AND THROUGH THE NIGHT. THIS INCLUDES THE STRONGEST MID LEVEL QVEC CONVERGENCE OF ALL THE MODELS. THE PREDICTED BULK SHEAR AND EML SUPPORTS POTENTIALLY SOME HEFTY TSTMS NORTHWEST OF OUR CWA DURING THE DAY ON MONDAY. IF ANYTHING, MODEL TRENDS ARE SLIGHTLY SLOWER AND THERE ARE STILL SOME MODELS THAT HAVE PCPN DISSIPATE BEFORE REACHING THE I95 CORRIDOR. WE REMAIN SLIGHTLY OPTIMISTIC BECAUSE ORGANIZATION IS LIKELY NORTHWEST OF US, OUR IN SITU AIR MASS ALOFT SHOULD BE ABLE TO MAINTAIN CONVECTION AND THERE WILL BE A LLJ OVERNIGHT. GIVEN THE EVENING, OVERNIGHT TIMING WE DID NOT CARRY ANY ENHANCED WORDING. THE EASTWARD EXTENSION OF SPC SLGT RISK FOR SEVERE STORMS REMAINS RIGHT ALONG OUR NORTHWEST BORDER. BECAUSE OF DECENT SOUTHWEST WINDS AT NIGHT, WE WENT WITH RELATIVELY HIGH STAT GUIDANCE MINS. ON TUESDAY, WE SEE THE MODELS EDGING TOWARD EACH OTHER. THE GFS HAS SOME MIXED LAYER CAPE VS HAVING NONE AT ALL YESTERDAY. THE ECMWF AND NAM ARE MORE BULLISH, BUT THEN THERE BIAS IS TO BE SLOW. OVERALL THERE IS A RACE BETWEEN DRIER AIR MOVING INTO OUR CWA AND CONVECTION BEING ABLE TO OCCUR. HIGHEST CHANCES ARE IN THE EASTERN/SOUTHEASTERN PART OF OUR CWA WITH AN ADDED POP FAR NORTHWEST LATE FOR PROXIMITY TO THE STRONGER SHORT WAVE. BECAUSE OF LOW CONFIDENCE OF OCCURRENCE, COVERAGE AND STORM RELATIVE INFLOW BEING WEAK, NO ENHANCED WORDING HWO MENTION WILL BE MADE. WE EXPECT DOWNSLOPING FLOW TO COMPENSATE FOR CAA AND KEPT MAX TEMPS CLOSE TO CONTINUITY. TUESDAY NIGHT AND WEDNESDAY, A LOW CHANCE EARLY IN DELMARVA, OTHERWISE THERE IS CONSENSUS OF THE CONVECTIVE TEMP NOT BEING REACHED WEDNESDAY. THIS IS THE ONE DRY DAY FORECAST DURING THE WORK WEEK. WITH LIGHT WINDS AND NOT MANY CLOUDS EXPECTED, WE RADIATE OUTLYING, MORE RURAL AREAS TUESDAY NIGHT. PREDICTED 1000-850MB THICKNESSES SUGGEST A 1-2F DROP OFF IN MAX TEMPS ON WEDNESDAY FROM TUESDAY LEVELS. WHILE CONFIDENCE IS INCREASING FOR A HEAVY RAIN EVENT FOR THE MIDDLE ATLANTIC STATES, TIMING OF WHEN THIS WILL OCCUR IS STILL UNCERTAIN. NAEFS ENSEMBLE MEANS ARE SHOWING THE LATE WEEK SFC SYSTEM IS MORE THAN 2SD FROM NORMAL EARLY AUGUST MSLP AND THE ENSEMBLE MEAN OVER WVA REPRESENT A ONCE IN 5 YEAR RETURN INTERVAL. MUCH TO BE MADE AS TO THE DETAILS AND THE GEOGRAPHICAL IMPACT. THIS HAS SOME SIMILARITIES TO THE JUNE 27TH EVENT. FOR NOW WE RAMP UP POPS STARTING WEDNESDAY NIGHT, BUT THE MODEL CONSENSUS IS CLOSEST TO A THURSDAY NIGHT TO FRIDAY DAY TIME FRAME AS OUR GREATEST POTENTIAL FOR PCPN AND HEAVIEST RAIN. BECAUSE CONVECTION IS INVOLVED, THE MCV VORTS ARE SHOWING LITTLE RUN TO RUN CONTINUITY AND HAVE A TENDENCY WHEN THERE ARE MORE OF THEM TO SLOW THE WORKS DOWN AND DRAG HEAVIER PCPN FARTHER NORTH. AT LEAST WITH THE 12Z RUNS, THE RELATIVE GOOD NEWS IS FOR IMPROVING CONDITIONS OVER THE WEEKEND, WITH SUNDAY THE MORE CONFIDENT DRY DAY AT THIS POINT. WITH A TROF FORMING AND STAYING OVER ERN NOAM, TEMPERATURES WILL TREND DOWNWARD AND SHOULD BE AT OR BELOW NORMAL THROUGH THE SECOND HALF OF THE LONG TERM. && .AVIATION /02Z MONDAY THROUGH FRIDAY/...
-- Changed Discussion --
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. VFR CONDITIONS ARE EXPECTED THROUGH THE TAF PERIOD. WINDS WILL BE LIGHT AND VARIABLE/CALM OVERNIGHT. A FEW AREAS MAY KEEP A LIGHT SW FLOW. WINDS ON MONDAY WILL INCREASE OUT OF THE SOUTH TO SOUTHWEST BY MID-LATE MORNING, AND BEGIN TO GUST 15-20 KNOTS BY LATE MORNING AND INTO THE AFTERNOON OUTLOOK... MONDAY NIGHT...A LOWERING TO MVFR WITH CIG/VSBY RESTRICTIONS IN SCATTERED SHWRS/TSTMS. TUESDAY AND TUESDAY NIGHT...MOSTLY VFR CONDITIONS. ISOLATED TO PERHAPS SCATTERED SHWRS/TSTMS ARE POSSIBLE EASTERN AIRPORTS AND TERMINALS. TUESDAY OVERNIGHT THROUGH WEDNESDAY NIGHT...MAINLY VFR CONDITIONS. THURSDAY THROUGH FRIDAY...MVFR CONDITIONS DURING SHWRS AND TSTORMS WITH SOME IFR CONDITIONS POSSIBLE. WHILE CONFIDENCE OF OCCURRING IS INCREASING, TIMING CONFIDENCE REMAINS LOW.
-- End Changed Discussion --
&& .MARINE... SUB-SMALL CRAFT ADVISORY CONDITIONS WILL CONTINUE THROUGH TONIGHT AS HIGH PRESSURE BEGINS TO WEAKEN LOSE CONTROL OVER THE AREA. A SMALL CRAFT ADVISORY HAS BEEN ISSUED STARTING LATE MONDAY AFTERNOON DUE TO AN EXCEPTED INCREASE IN WINDS LATE IN THE DAY. OUTLOOK.. MONDAY NIGHT AND TUESDAY...WE WILL CONTINUE THE SMALL CRAFT ADVISORY FOR THE OCEAN WATERS. THE LOW LEVEL JET DOES PASS OVER THE OCEAN WATERS AND WHILE SEAS NORMALLY RAMP UP TOO QUICKLY, WAVE WATCH GUIDANCE (7 FEET) LEAVES MORE THAN ENOUGH WIGGLE ROOM TO STILL MEET CRITERIA FOR SEAS. WE ARE NOT AS SURE ABOUT DELAWARE BAY AND WILL HOLD OFF WITH THIS PACKAGE. SMALL CRAFT ADVISORY CONDITIONS (SEAS LAST) SHOULD CEASE ON THE OCEAN DURING THE DAY ON TUESDAY. TUESDAY NIGHT THROUGH WEDNESDAY NIGHT...SUB SMALL CRAFT ADVISORY CONDITIONS ARE EXPECTED. THURSDAY THROUGH FRIDAY...A STALLED FRONT AND A WAVE OF LOW PRESSURE MOVING ALONG IT COULD ENHANCE SEAS AND/OR WINDS FOR THE OCEAN COASTAL WATERS AND MIGHT BRING SMALL CRAFT ADVISORY CONDITIONS AGAIN. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...SMALL CRAFT ADVISORY FROM 4 PM MONDAY TO 10 AM EDT TUESDAY FOR ANZ450>455. && $$ SYNOPSIS...GIGI/KLINE NEAR TERM...ROBERTSON/O`HARA SHORT TERM...ROBERTSON LONG TERM...GIGI AVIATION...GIGI/KLINE/ROBERTSON MARINE...GIGI/KLINE/ROBERTSON

USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.