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 140117 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 917 PM EDT MON APR 13 2015 .SYNOPSIS... A COLD FRONT WILL MOVE ACROSS OUR REGION ON TUESDAY. HIGH PRESSURE BUILDS OVER THE NORTHEAST DURING MIDWEEK. SEVERAL STORM SYSTEMS WILL MOVE THROUGH THE AREA LATE THIS WEEK INTO THE WEEKEND, BRINGING UNSETTLED WEATHER TO THE REGION. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/... THE MODELS OVERALL VERIFIED TOO FAR EAST WITH THE ONSET OF PCPN AT 00Z IN PA WITH THE GFS THE MOST EGREGIOUS, ITS .25" ISOHYET MATCHED THE EASTERN EDGE OF THE SHOWERS BETTER. NEITHER CANADIAN MODEL IS HANDLING PCPN WELL OVER THE CAROLINAS AND THE CAN RGEM WAS WAY TOO WET TO OUR WEST. THIS HAS LEFT US WITH A NAM/ECMWF/UKMET BLEND TO USED FOR THE UPDATE OF PCPN TIMING. WE HAVE SLOWED IT DOWN BY A FEW HOURS OVERNIGHT. THIS IS IN LINE WITH RECENT HRRR(S) AND RAP(S) ALTHOUGH THE LATTER IS SOMETIMES TOO SLOW. WITHOUT THE PCPN FALLING TO EVAP COOL AND A SOUTH WIND CONTINUING, WE ADJUSTED TEMPS UPWARD A COUPLE OF DEGREES. THE GUSTIER SRLY WINDS CONTINUE IN MOST AREAS. WE EXPECT THIS TO CONTINUE FOR ANOTHER HOUR OR SO BEFORE DECREASING. WINDS WILL PROBABLY REMAIN 5 TO 10 MPH MUCH OF THE NIGHT, OTHERWISE, THE WEATHER FOR THE FIRST HALF OF THE NIGHT WILL BE QUIET, WITH ONLY A SLIGHT INCREASE IN CLOUD COVER. HOWEVER, CLOUDS WILL CONTINUE TO THICKEN OVERNIGHT THROUGH DAYBREAK TUESDAY AS A COLD FRONT APPROACHES THE AREA. WE EXPECT SHOWERS TO BEGIN ACROSS OUR WESTERN AREAS OVERNIGHT AND PROGRESS EASTWARD. && .SHORT TERM /6 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/... SHOWERS WILL BE ONGOING AT THE START OF TUESDAY MORNING AS A COLD FRONT WILL BE MAKING ITS WAY ACROSS THE FORECAST AREA. SHOWERS WILL INCREASE FROM WEST TO EAST EARLY IN THE MORNING AS THE FRONT MOVES EASTWARD. AN AREA OF LOW PRESSURE MAY DEVELOP ALONG THE BOUNDARY JUST TO OUR SOUTH AS A SHORT WAVE/VORTICITY MAX MOVES ACROSS THE AREA. IF THIS HAPPENS, IT MAY HELP ENHANCE SHOWER ACTIVITY AND LEAD TO A PERIOD OF HEAVIER RAINFALL ACROSS SOUTHERN NEW JERSEY AND CENTRAL/SOUTHERN DELMARVA DURING THE AFTERNOON HOURS. WE WILL KEEP A MENTION OF HEAVY RAINFALL IN THE HWO DUE TO THIS POTENTIAL. PRECIPITATION WILL END FROM WEST TO EAST THROUGH THE DAY, BUT WILL MOST LIKELY LAST THROUGH THE AFTERNOON ACROSS SOUTHERN NEW JERSEY AND CENTRAL/SOUTHERN DELMARVA. WE HAVE NOT INCLUDED THUNDERSTORMS IN THE FORECAST AS THERE IS NOT MUCH, IF ANY INSTABILITY FORECAST. AGAIN, A BLEND OF MAV/MET MOS AND MOSGUIDE WERE USED WITH SOME MINOR HAND ADJUSTMENTS. && .LONG TERM /TUESDAY NIGHT THROUGH MONDAY/... AT THE BEGINNING OF THIS TIME PERIOD WILL BE DEALING WITH THE LINGERING AFFECTS OF PRECIPITATION TO THE NORTH OF THE COLD FRONT WHICH JUST MOVED THROUGH THE REGION. 12Z EURO AND GFS HAVE BOTH TRENDED WETTER FOR TUESDAY EVENING, SLOWING DOWN THE SOUTHWARD PUSH OF THE PRECIPITATION. GRIDS WERE ADJUSTED TO ACCOUNT FOR THIS TREND. AFTER TUESDAY NIGHT...DRY WEATHER IS THE MAIN TREND FOR WEDNESDAY AND THURSDAY. FOR FRIDAY INTO MONDAY...SEVERAL PERIODS OF PRECIPITATION IN THIS TIME FRAME BUT TIMING IS MORE UNCERTAIN THAN AVERAGE AS IMPULSES MOVING THROUGH SPLIT FLOW PATTERN ARE DIFFICULT TO TIME. USED MET/MAV BLEND FOR TEMPERATURE TUESDAY NIGHT THROUGH WEDNESDAY NIGHT, THEN WPC GUIDANCE FOR REMAINDER OF TIME PERIOD. PRECIPITATION TIMING LATE WEEK INTO WEEKEND LEANED HEAVILY ON WPC GUIDANCE. HEAVY RAINFALL IS POSSIBLE IN THE WEEKEND TIMEFRAME, BUT UNCERTAINTY STILL TOO HIGH TO WARRANT MENTION IN HWO. && .AVIATION /01Z TUESDAY THROUGH SATURDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. VFR CONDITIONS WILL CONTINUE FOR THE FIRST HALF OF THE NIGHT TIME PERIOD. GUSTY WINDS WILL CONTINUE INTO THE EARLY EVENING, BEFORE THE GUSTS BEGIN TO DIMINISH SHORTLY AFTER SUNSET. A STEADY SOUTH TO SOUTHWEST BREEZE AROUND 10 KNOTS WILL PROBABLY CONTINUE OVERNIGHT. CLOUDS WILL INCREASE LATER, AND EVENTUALLY ARE EXPECTED TO BECOME MVFR FROM WEST TO EAST AS A COLD FRONT AND ASSOCIATED SHOWERS MOVE INTO THE AREA SHORTLY BEFORE DAYBREAK TUESDAY. THE FRONT AND SHOWERS WILL PROGRESS EASTWARD THROUGH THE MORNING AND INTO THE AFTERNOON, AND COULD INCREASE IN INTENSITY AS THEY MOVE ACROSS THE I-95 CORRIDOR EASTWARD. THERE IS THE POTENTIAL FOR IFR CIGS/VSBYS TO DEVELOP FROM TTN-PNE-PHL-ILG SOUTH AND EASTWARD, WITH THE GREATEST THREAT FOR ACY/MIV. AFTER THE FRONT MOVES THROUGH, THE SHOWERS SHOULD BEGIN TO DISSIPATE AND A RETURN TO VFR SHOULD BEGIN TO OCCUR FOR MOST AREAS BY LATE IN THE DAY. MIV/ACY HAVE THE BEST CHANCE TO KEEP SHOWERS AND LOWER CONDITIONS THROUGH DAY. WINDS TUESDAY WILL START OUT OF THE SOUTH-SOUTHWEST, BEFORE SWINGING TO THE NORTHWEST OR NORTH BEHIND THE FRONT, WINDS ARE THEN FORECAST TO BECOME NORTHEAST DURING THE AFTERNOON ACROSS THE AREA. OUTLOOK... TUESDAY NIGHT...CONDITIONS SLOWLY IMPROVING TUESDAY EVENING FROM IFR AND MVFR TO VFR AS RAIN MOVES OFF SHORE. VFR AFTER MIDNIGHT. WEDNESDAY AND THURSDAY...VFR CONDITIONS EXPECTED. THURSDAY NIGHT...CONDITIONS LOWERING TO MVFR AS RAIN SHOWERS MOVE IN. FRIDAY AND SATURDAY...MVFR CONDITIONS IN RAIN SHOWERS. && .MARINE... WINDS AND WAVES ARE EXPECTED TO REMAIN BELOW ADVISORY LEVELS THROUGH TUESDAY, ALTHOUGH WINDS WILL GUST IN THE LOW 20S AT TIMES. WINDS WILL BE MOSTLY SOUTHWEST THROUGH TONIGHT INTO EARLY TUESDAY, BEFORE SWITCHING TO THE NORTH AND NORTHWEST BEHIND A FRONTAL BOUNDARY DURING THE DAY TUESDAY. OUTLOOK... TUESDAY NIGHT AND WEDNESDAY...WIND GUSTS ABOVE 25 KT ARE POSSIBLE ESPECIALLY ON THE ATLANTIC COASTAL WATERS ADJACENT TO DELAWARE AND SOUTHERN NJ FOR TUESDAY NIGHT INTO EARLY WEDNESDAY MORNING. OTHERWISE, CONDITIONS ARE GENERALLY EXPECTED TO BE BELOW SCA CRITERIA. THURSDAY THROUGH SATURDAY...CONSIDERABLE UNCERTAINTY THROUGH THIS TIME, BUT SEAS ABOVE 5 FT ARE POSSIBLE ON THE ATLANTIC COASTAL WATERS. && .FIRE WEATHER... CONDITIONS WERE GUSTY TODAY, BUT DEWPOINTS SURGED UPWARD DURING THE DAY, WHICH HAS KEPT RELATIVE HUMIDITY VALUES FROM CRITICAL LEVELS. WITH A COLD FRONT AND RAINFALL EXPECTED TONIGHT INTO TUESDAY, FUELS SHOULD MOISTEN ACROSS THE AREA. IT IS POSSIBLE THAT SOME AREAS ACROSS OUR NORTHWESTERN ZONES MAY CLEAR OUT BEHIND THE FRONT DURING THE DAY AND HAVE SOME LOWER HUMIDITY VALUES LATE IN THE DAY, BUT WINDS ARE NOT EXPECTED TO BE VERY GUSTY. FOR WEDNESDAY...ALTHOUGH RELATIVE HUMIDITY VALUES WILL LIKELY ONCE AGAIN DROP INTO THE 20S ACROSS MUCH OF THE AREA, WINDS MAY NOT BE FREQUENTLY GUST ABOVE 20 MPH, AND MUCH OF THE REGION SHOULD RECEIVE WETTING RAINS OVER THE NEXT 24 TO 48 HOURS WHICH SHOULD HELP KEEP FUELS MOIST. && .HYDROLOGY... THERE REMAINS THE POTENTIAL FOR A PERIOD OF HEAVY RAINFALL ON TUESDAY DURING THE LATE MORNING INTO THE AFTERNOON, ESPECIALLY ACROSS SOUTHERN NEW JERSEY AND CENTRAL/SOUTHERN DELMARVA. HIGH PW VALUES AND ENHANCED LIFT ASSOCIATED WITH A DEVELOPING WAVE OF LOW PRESSURE ALONG THE FRONT CREATE A PERIOD OF HEAVY RAINFALL, WHICH IF IT OCCURS IN A SHORT ENOUGH TIME PERIOD COULD LEAD TO SOME URBANIZED AND POOR DRAINAGE FLOODING ACROSS PORTIONS OF SOUTHERN NEW JERSEY AND CENTRAL/SOUTHERN DELMARVA. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...NONE. && $$ SYNOPSIS...SZATKOWSKI NEAR TERM...GIGI/ROBERTSON/O`HARA SHORT TERM...ROBERTSON LONG TERM...SZATKOWSKI AVIATION...ROBERTSON/O`HARA MARINE...SZATKOWSKI/ROBERTSON FIRE WEATHER... HYDROLOGY...

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