Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 282215 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 615 PM EDT TUE JUL 28 2015 .SYNOPSIS... HIGH PRESSURE WILL SLIDE OFF THE COAST ON WEDNESDAY GIVING WAY TO A WEAK COLD FRONT PASSAGE ON THURSDAY INTO FRIDAY MORNING. ANOTHER WEAK FRONT MAY CROSS THE REGION SUNDAY INTO MONDAY FOLLOWED BY A BRIEF SHOT OF HIGH PRESSURE. AFTER THE RESPITE OF HIGH PRESSURE A STRONGER COLD FRONT IS EXPECTED TO PASS THROUGH ON TUESDAY. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
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UPDATED POPS, WEATHER AND SKY GRIDS BASED ON THE LATEST RADAR AND SATELLITE TRENDS JUST AFTER 530 PM. A STATIONARY BOUNDARY WAS LOCATED NEAR I-95 LATE THIS AFTERNOON. ANY SHOWERS AND STORMS EARLY THIS EVENING STILL LOOKS TO BE CONFINED TO THE SOUTH AND EAST OF THIS BOUNDARY, WHERE HIGHER DEWPOINTS AND INSTABILITY EXISTS. THE COVERAGE WILL BE MAINLY ISOLATED. ADDITIONAL CONVECTION IS BEING FOCUSED ALONG THE SEA-BREEZE FRONT IN SOUTHERN NJ AND SOUTHERN DELAWARE. HIGHER POPS WERE PLACED IN THERE THRU SUNSET. THESE STORMS ARE SLOW-MOVERS (AS ALL STORMS HAVE BEEN THIS WEEK), SO THERE IS ONCE AGAIN A LOCALLY HEAVY RAINFALL WITH ISOLATED 1-2 INCHES PER HOUR CAPABLE OF POOR DRAINAGE FLOODING. PREVIOUS DISCUSSION... OTHERWISE, SCATTERED CUMULUS SHOULD DISSIPATE GRADUALLY DURING THE EVENING HOURS. WHILE SOME PATCHY LOW CLOUDS, HAZE AND LIGHT FOG MAY DEVELOP LATE TONIGHT THE MODEL GUIDANCE SUGGESTS THAT IT SHOULD NOT BE AS WIDESPREAD AS IT WAS THIS MORNING. A MID LEVEL RIDGE IS FORECAST TO EXTEND FROM THE SOUTH CENTRAL STATES UP ACROSS THE GREAT LAKES TO EASTERN ONTARIO AND WESTERN QUEBEC TONIGHT. THE RIDGE IS EXPECTED TO KEEP OUR AREA RAIN-FREE FOR TONIGHT. MINIMUM TEMPERATURES ARE ANTICIPATED TO BE MAINLY IN THE UPPER 60S AND LOWER 70S WITH A LIGHT SOUTHWEST TO SOUTH SURFACE FLOW.
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&& .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/... THE AXIS OF THE MID LEVEL RIDGE IS FORECAST TO DRIFT EASTWARD AND IT SHOULD APPROACH OUR REGION LATE ON WEDNESDAY. AS A RESULT, THE POTENTIAL FOR SHOWERS AND THUNDERSTORMS WILL BE EVEN LOWER THAN IT WAS TODAY. WE ARE EXPECTING A MOSTLY SUNNY SKY FOR WEDNESDAY WITH SOME CIRRUS OVERHEAD ALONG WITH THE DEVELOPMENT OF SCATTERED CUMULUS. MAXIMUM TEMPERATURES ARE FORECAST TO RANGE FROM 90 TO 95 IN MUCH OF OUR REGION. READINGS SHOULD GET NO HIGHER THAN THE MIDDLE AND UPPER 80S IN THE ELEVATED TERRAIN UP NORTH AND ALONG THE IMMEDIATE COAST. IT APPEARS AS THOUGH SLIGHTLY DRIER AIR WILL MIX TO THE SURFACE FROM ALOFT FOR WEDNESDAY AFTERNOON. DEW POINT READINGS ARE EXPECTED TO FAVOR THE MIDDLE 60S ON WEDNESDAY AFTERNOON, EXCEPT IN DELAWARE AND NORTHEASTERN MARYLAND WHERE THE BAYS SHOULD HELP KEEP DEW POINT READINGS IN THE UPPER 60S AND LOWER 70S. THE COMBINATION OF TEMPERATURE AND DEW POINT IS ANTICIPATED TO RESULT IN MAXIMUM HEAT INDEX VALUES BEING NEAR OR A DEGREE OR TWO ABOVE THE MAXIMUM AIR TEMPERATURES IN EASTERN PENNSYLVANIA AND NEW JERSEY. THE IMPACT OF THE HIGHER HUMIDITY ON THE DELMARVA SHOULD BRING MAXIMUM HEAT INDEX VALUES SOLIDLY INTO THE UPPER 90S THERE WITH PERHAPS A FEW SPOTS HITTING 100, ESPECIALLY SOUTH OF THE CANAL. WE WILL NOT BE ISSUING A HEAT ADVISORY OR AN EXCESSIVE HEAT WARNING AT THIS TIME SINCE ALL LOCATIONS IN OUR FORECAST AREA ARE EXPECTED TO REMAIN JUST BELOW THE ISSUANCE CRITERIA. A SOUTHWEST TO SOUTH WIND AROUND 5 TO 10 MPH IS EXPECTED FOR WEDNESDAY. && .LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
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5-WAVE MODEL GUIDANCE SHOWS SOUTHEAST RIDGING GIVING WAY TO A DEVELOPING TROUGH ACROSS THE NORTHEASTERN HALF OF THE CONUS BY THE WEEKEND. A FEW IMPULSES WILL TRAVERSE THROUGH THE BASE OF THE TROUGH NEXT WEEK PROVIDING CHANCES FOR MORE UNSETTLED WEATHER EARLY NEXT WEEK. THURSDAY...INCREASING MOISTURE FLUX AHEAD OF THE WEAKENING COLD FRONT MAY BRING IN MORE CLOUD COVER THAN PREVIOUSLY EXPECTED. THERE COULD BE ENOUGH INSTABILITY ADVECTING IN ALOFT TO SPARK SCATTERED SHOWERS WITH EMBEDDED THUNDER DURING THE MORNING HOURS, MOSTLY ACROSS THE SOUTH AND WEST, TO KEEP TEMPERATURES FROM REALLY PEAKING AS HIGH AS PREVIOUSLY THOUGHT, THOUGH LOW-90S IS NOTHING TO SNEEZE AT. THERE WILL BE SOME ENHANCED VERTICAL MIXING DURING THE AFTERNOON WHICH SHOULD KEEP DEWPOINTS FROM STAYING IN THE LOW-70S, SO EXPECTING THEM TO MIX OUT INTO THE UPPER-60S...SHOULD KEEP HEAT INDEX VALUES JUST BELOW ADVISORY CRITERIA BUT STILL HAVE SOME TIME FOR FURTHER ASSESSMENT. BESIDES THE HEAT, THE APPROACH OF THE COLD FRONT LATER IN THE AFTERNOON, WILL TRIGGER MORE SCATTERED SHOWERS AND THUNDERSTORMS. INSTABILITY IS PREVALENT BUT SHEAR IS ON THE WEAKER SIDE AS OF NOW BUT DEPENDING ON THE SHEAR AXIS ORIENTATION TO THE STORMS, WE COULD SEE CELL MERGER OCCUR FORMING A BROKEN LINE OF STORMS WITH STRONGER WINDS THE MAIN ISSUE. PWATS APPROACH AND COULD SURPASS 2" SO HEAVY EFFICIENT RAINERS IS ALSO LIKELY WITH POOR DRAINAGE AND SPOTTY FLASH FLOOD ISSUES POSSIBLE. FRIDAY - SUNDAY...AS MID-LEVEL TROUGHING BEGINS TO STRENGTHEN BY THE WEEKEND, THE AFOREMENTIONED FRONT BECOMES MORE PARALLEL TO THE UPPER- LEVEL FLOW...IT LOOKS TO STALL OFFSHORE. IT BEGINS TO SLOW ITS DEPARTURE EARLY ON FRIDAY SO THERE COULD BE SOME LINGERING SHOWERS AND THUNDERSTORMS FRIDAY MORNING BEFORE DRYING OUT. TEMPERATURES WILL STILL BE QUITE WARM BUT THE FRONT SHOULD BE ABLE TO EAT UP THE HIGHER DEWPOINTS AS THE AIRMASS DRIES OUT A BIT. WE LOOK TO BE ON THE SOUTHERN EXTENT OF THE TROUGHING SO MOST OF THE MID-LEVEL ENERGY STAYS TO OUR NORTH THROUGH THE WEEKEND KEEPING US MOSTLY DRY...COULD BE SOME ISOLATED SHOWERS ACROSS SOUTHERN DELMARVA CLOSER TO THE STALLED BOUNDARY. TEMPERATURES ON SATURDAY AND SUNDAY WILL STILL REMAIN 90+ DEGREES. MONDAY - TUESDAY...ANOTHER COLD FRONT IS PROGGED TO PUSH CLOSER TO THE REGION BY LATE MONDAY INTO TUESDAY. TEMPERATURES AHEAD OF THE FRONT WILL ONCE AGAIN BE 90+ DEGREES WITH A MOISTENING AIRMASS. MORE SCATTERED SHOWERS AND THUNDERSTORMS ARE POSSIBLE.
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&& .AVIATION /22Z TUESDAY THROUGH SUNDAY/...
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THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. AN AREA OF SHOWERS AND NEARBY STORMS CURRENTLY IMPACTING ACY WITH A BRIEF PERIOD OF IFR VSBYS. OTHERWISE, VCSH MENTIONED AT ILG AND MIV THRU 00Z. A MAINLY CLEAR SKY IS EXPECTED FOR TONIGHT. WHILE SCATTERED LOW CLOUDS, HAZE AND LIGHT FOG REMAIN POSSIBLE FOR LATE TONIGHT AND EARLY WEDNESDAY MORNING, IT SHOULD NOT BE NEARLY AS WIDESPREAD AS IT WAS THIS MORNING. VFR CONDITIONS WITH SCATTERED CUMULUS IS IN THE FORECAST FOR WEDNESDAY. THE POTENTIAL FOR SHOWERS AND THUNDERSTORMS IS VERY LOW. A LIGHT SOUTHWEST TO SOUTH WIND, GENERALLY LESS THAN 10 KNOTS, IS EXPECTED THROUGH THE TAF PERIOD. OUTLOOK... THURSDAY...EARLY MORNING FOG/HAZE WITH MVFR CONDITIONS POSSIBLE...THEN SCT AFTERNOON/EVENING TSTMS WITH MVFR OR LOWER CONDS. FRIDAY - SUNDAY...VFR.
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&& .MARINE... WEAK HIGH PRESSURE WILL CONTINUE TO AFFECT THE COASTAL WATERS OF NEW JERSEY AND DELAWARE FOR TONIGHT AND WEDNESDAY. A SOUTHWEST TO SOUTH WIND AROUND 5 TO 10 KNOTS IS EXPECTED. WAVE HEIGHTS ON THE OCEAN WILL FAVOR 2 TO 3 FEET WHILE WAVES ON DELAWARE BAY SHOULD BE 2 FEET OR LESS. OUTLOOK... THURSDAY - SUNDAY...SUB-SCA CONDITIONS EXPECTED THIS PERIOD. THUNDERSTORM CHANCES INCREASE ON THURSDAY WITH VERY HEAVY RAINFALL AND STRONG WIND GUSTS POSSIBLE. && .RIP CURRENTS... THERE IS A MODERATE RISK FOR THE DEVELOPMENT OF DANGEROUS RIP CURRENTS ALONG THE NEW JERSEY AND DELAWARE COAST INTO THIS EVENING DUE TO A LONG PERIOD SOUTHEASTERLY SWELL. THE WAVE PERIOD WILL CONTINUE TO BE AROUND 10 SECONDS. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...NONE. && $$ SYNOPSIS...HEAVENER NEAR TERM...IOVINO/KLEIN SHORT TERM...IOVINO LONG TERM...HEAVENER AVIATION...IOVINO/HEAVENER/KLEIN MARINE...IOVINO/HEAVENER RIP CURRENTS...

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