Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 010133 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 933 PM EDT SUN AUG 31 2014 .SYNOPSIS... HIGH PRESSURE WELL OFF THE EAST COAST WILL MAINTAIN A SOUTHWESTERLY FLOW OVER THE AREA THROUGH THE FIRST PART OF THE WEEK. A WEAK COLD FRONT IS THEN EXPECTED TO MOVE ACROSS OUR AREA LATE TUESDAY. HIGH PRESSURE WILL BUILD IN BEHIND THIS FRONT FOR THE SECOND HALF OF THE WEEK BEFORE ANOTHER COLD FRONT ARRIVES IN THE REGION THIS WEEKEND. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/... SCATTERED SHOWERS AND THUNDERSTORMS CONTINUE ACROSS THE AREA, ESPECIALLY ACROSS SOUTHERN NEW JERSEY AND THE DELMARVA. THE STRENGTH OF THE STORMS HAS DIMINISHED AS INSTABILITY IS WANING NOW THAT NIGHT HAS FALLEN. HOWEVER, AS A COUPLE OF SHORT WAVES/VORTICITY IMPULSES SLIDE ACROSS THE AREA, THE POTENTIAL FOR SHOWERS AND THUNDERSTORMS WILL EXIST THROUGH THE NIGHT. THE FIRST IS SLIDING ACROSS THE NORTHERN HALF OF THE AREA NOW, SO THE SHOWERS AND THUNDERSTORMS ACROSS MOST OF NEW JERSEY WILL CONTINUE TO SLIDE OFF THE COAST OVER THE NEXT COUPLE OF HOURS. A SECOND IS EXPECTED TO SLIDE ACROSS THE SOUTHERN PART OF THE AREA LATER TONIGHT, WHICH COULD HELP SHOWERS AND THUNDERSTORMS EITHER CONTINUE OR REDEVELOP ACROSS OUR SOUTHERN AREAS OVERNIGHT. ONCE BOTH OF THESE PASS TO OUR EAST BY DAYBREAK TOMORROW, WE SHOULD END UP WITH A BREAK IN SHOWER ACTIVITY. WITH THE PWATS BEING WELL ABOVE NORMAL, ANY OF THE SHOWERS WILL BE WATER LADEN AND PRODUCE VERY HEAVY DOWNPOURS. THESE DOWNPOURS COULD PRODUCE LOCALIZED SMALL STREAM AND POOR DRAINAGE FLOODING...GOOD THING THE STORM MOTION IS RELATIVELY QUICK. && .SHORT TERM /6 AM MONDAY MORNING THROUGH 6 PM MONDAY/... SOUPY AIRMASS REMAINS IN PLACE WITH WEAK MID-LEVEL SHORTWAVE MOVING THROUGH. THE WAVE ALOFT LOOKS TO GET SHEARED OUT AS IT MOVES IN ALOFT SO IT DOES NOT APPEAR TO BE A GREAT TRIGGER FOR CONTINUED CONVECTIVE ACTIVITY. THAT BEING SAID, ANY DIFFERENTIAL HEATING THAT OCCURS COMBINED WITH WEAK SURFACE CONVERGENCE CAN BE THE SPARK NEEDED TO GET CONVECTION GOING. WE CONTINUE TO HAVE AT LEAST 40-50 PERCENT POPS FOR A MAJORITY OF THE REGION. TEMPERATURES TOMORROW WILL BE SEVERAL DEGREES ABOVE NORMAL. UPTICKED THE MAX TEMPERATURES A DEGREE ACROSS THE I-95 CORRIDOR AS ANY BREAKS IN THE CLOUDS WILL BE ENOUGH FOR SUBSTANTIAL HEATING. && .LONG TERM /MONDAY NIGHT THROUGH SUNDAY/... AT THE BEGINNING OF THIS PERIOD, WE SEE A TRANSITION TO MOSTLY ZONAL FLOW FROM THE LOWER THROUGH UPPER LEVELS. TUESDAY...BEFORE MUCH DRY AIR ADVECTION WITH THE ZONAL FLOW CAN KICK IN THOUGH, WE WILL SEE A RATHER UNCOMFORTABLE DAY WITH HIGHS IN THE 80S AND 90S, WHILE HEAT INDEX VALUES COULD APPROACH THE MID AND UPPER 90S IN DELMARVA AND THE I95 CORRIDOR. TUESDAY NIGHT...MODELS STILL SHOWING THE FRONT ARRIVING DURING THIS PERIOD, BRINGING SOMEWHAT COOLER, BUT MOSTLY DRIER AIR. STILL SOME CHANCE FOR SHOWERS AND STORMS AHEAD OF AND WITH THE FRONT, HOWEVER WITH THE ZONAL FLOW IN PLACE, AND MODEST DRY AIR ADVECTION OCCURRING AHEAD OF THE FRONT, MOISTURE AVAILABILITY WILL BE SOMEWHAT QUESTIONABLE. WEDNESDAY THROUGH FRIDAY...A HIGH BUILDS OVER THE REGION IN THE WAKE OF THE COLD FRONT. AS A RESULT EXPECT A FEW, NICE, SUMMER LIKE DAYS WITH HIGHS IN THE 80S. SATURDAY THROUGH SUNDAY...THE NEXT COLD FRONT IS SET TO ARRIVE OVER THE WEEKEND. THOUGH THERE IS SOME QUESTION WITH THE CONTINUED ZONAL FLOW HOW FAR SOUTH THE FRONT WILL DIG, BOTH THE GFS AND ECMWF HAVE BEEN CONSISTENT IN SHOWING THE FRONT MOVING SOUTH OF OUR REGION THROUGH THIS PERIOD. && .AVIATION /01Z MONDAY THROUGH FRIDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. TONIGHT...MOSTLY VFR TO MVFR. SCATTERED SHOWERS AND A FEW THUNDERSTORMS POSSIBLE, ESPECIALLY FOR MIV/ACY WHERE THEY ARE ONGOING AND SHOULD CONTINUE THROUGH MIDNIGHT LOCAL; SO TSRA WERE CONTINUED IN THE 00Z TAFS. FOR THE REST OF THE TAF SITES, THERE REMAINS THE POTENTIAL FOR SCATTERED SHOWERS, SO -SHRA/VCSH WERE INCLUDED FOR THE EARLY PART OF THE NIGHT. WINDS LIGHTEN AND MAY BECOME VARIABLE AT MANY LOCATIONS, BUT SHOULD REMAIN MOSTLY SOUTH-SOUTHWESTERLY WHERE THERE IS A DIRECTION. NOT ENTIRELY SURE WE WILL SEE WIDESPREAD MVFR CIGS, AS WE MAY END UP WITH MORE LIGHT FOG OVERNIGHT, ESPECIALLY WERE RAIN FELL. HOWEVER, WE STILL HAVE A PERIOD OF MVFR CIG AND/OR VSBY OVERNIGHT AND TOWARD DAYBREAK. TOMORROW...VFR. ANY STRATUS/FOG MIXES OUT BY LATE MORNING. ANOTHER ROUND OF SHOWERS AND THUNDERSTORMS ARE POSSIBLE BUT AT THIS TIME, LOCATION IS A BIG QUESTION, SO ONLY INCLUDED -SHRA IN THE AFTERNOON TIME PERIOD. OUTLOOK... MONDAY NIGHT...COVERAGE OF STORMS DECREASES THROUGH THE EVENING HOURS. HOWEVER, WITH LOW LEVEL MOISTURE IN PLACE, IFR VISIBILITIES DUE TO BR COULD LINGER FOR MUCH OF THE NIGHT. TUESDAY AND TUESDAY NIGHT...CONDITIONS IMPROVING TO VFR EARLY IN THE DAY. SOME SHOWERS AND THUNDERSTORMS POSSIBLE LATE TUESDAY AFTERNOON AND TUESDAY EVENING, ALONG WITH AN ABRUPT WIND SHIFT AS A COLD FRONT MOVES THROUGH THE REGION. WEDNESDAY THROUGH FRIDAY...GENERALLY VFR CONDITIONS EXPECTED. && .MARINE... SUB-SCA CONDITIONS EXPECTED TONIGHT AND TOMORROW. SEAS WILL CONTINUE TO BUILD THROUGH TOMORROW...AROUND 4 FEET. WINDS SHOULD BE LIGHTER TOMORROW THAN TODAY. OUTLOOK... MONDAY NIGHT THROUGH FRIDAY...SEAS AND WINDS ARE EXPECTED TO REMAIN BELOW SMALL CRAFT ADVISORY CRITERIA. SOME GUSTY WINDS WILL BE POSSIBLE IN THE VICINITY OF THUNDERSTORMS MONDAY EVENING AND AGAIN TUESDAY NIGHT. && .HYDROLOGY... VERY HIGH PWAT AIRMASS IN PLACE TODAY AND TONIGHT. NUMEROUS MID-LEVEL WAVES/TROUGHS MOVE THROUGH THE REGION TAPPING INTO THE MOISTURE ALLOWING FOR VERY HEAVY DOWNPOURS, ESPECIALLY IN CONVECTION. STORM MOTIONS SHOULD BE QUICK ENOUGH FOR MOSTLY POOR DRAINAGE AND SOME SMALL STREAM FLOODING. THROUGH TOMORROW AFTERNOON, WHEN MORE SHOWERS AND THUNDERSTORMS ARE POSSIBLE, QPF ACCUMULATIONS OF AROUND AN INCH ARE POSSIBLE...HIGHER WITHIN SOME STORMS. CURRENT CONDITIONS ACROSS THE REGION HAVE BEEN DRY SO NOT EXPECTING MUCH IN THE WAY OF FLASH FLOODING CONCERNS. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...NONE. && $$ SYNOPSIS...JOHNSON NEAR TERM...HEAVENER/ROBERTSON SHORT TERM...HEAVENER LONG TERM...JOHNSON AVIATION...HEAVENER/JOHNSON/ROBERTSON MARINE...HEAVENER/JOHNSON HYDROLOGY...HEAVENER

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