331
FXUS61 KPHI 012352
AFDPHI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
752 PM EDT TUE SEP 1 2026
WHAT HAS CHANGED
AVIATION SECTION UPDATED FOR THE 00Z TAF ISSUANCE.
THE HEAT ADVISORY FOR THE URBAN CORRIDOR HAS BEEN ALLOWED TO
EXPIRE.
FOR WEDNESDAY, MODELS TRENDING SLIGHTLY COLDER FOR MUCH OF THE
REGION, LIMITING THE INSTABILITY WITH STORM CHANCES.
THE CHANCE FOR SHOWERS AND THUNDERSTORMS SHIFTED A BIT NORTH ON
FRIDAY. FRIDAY AFTERNOON HIGH TEMPERATURES ALSO INCHED UP A FEW
DEGREES.
KEY MESSAGES
1. SCATTERED SEVERE THUNDERSTORMS WILL CONTINUE TO TRACK
SOUTHEASTWARD ACROSS PORTIONS OF EASTERN PA, NJ, AND PERHAPS THE
DELMARVA THROUGH LATE THIS EVENING. DAMAGING WIND GUSTS, LARGE
HAIL, AND A TORNADO OR TWO WILL BE POSSIBLE.
2. ON WEDNESDAY, A SHORTWAVE TROUGH COULD SPARK ANOTHER ROUND
OF SHOWERS AND STORMS, BUT IT WILL BE WORKING AGAINST A
RELATIVELY STABLE BOUNDARY LAYER.
3. HOT AND HUMID CONDITIONS ARE FORECAST ACROSS THE REGION ON
THURSDAY.
4. UNSETTLED CONDITIONS WILL CONTINUE ON THURSDAY WITH THE
POTENTIAL FOR SEVERE THUNDERSTORMS. SCATTERED THUNDERSTORMS ARE
AGAIN POSSIBLE ON FRIDAY, MAINLY FROM PHILADELPHIA SOUTH.
5. THE LABOR DAY WEEKEND WILL FEATURE MOSTLY DRY WEATHER WITH
AT OR BELOW NORMAL TEMPERATURES AND LOWER HUMIDITY.
DISCUSSION
KEY MESSAGE 1...SCATTERED SEVERE THUNDERSTORMS WILL CONTINUE TO
TRACK SOUTHEASTWARD ACROSS PORTIONS OF EASTERN PA, NJ, AND
PERHAPS THE DELMARVA THROUGH LATE THIS EVENING. DAMAGING WIND
GUSTS, LARGE HAIL, AND A TORNADO OR TWO WILL BE POSSIBLE.
A SEVERE THUNDERSTORM WATCH REMAINS IN EFFECT FOR THE ENTIRE
AREA UNTIL MIDNIGHT TONIGHT.
A QUASI-STATIONARY FRONT IS CURRENTLY LOCATED JUST TO THE NORTH
OF THE AREA. THIS EVENING, IT SHOULD BEGIN TO WORK SOUTHWARD AS
A COLD FRONT. AHEAD OF THIS BOUNDARY, THE ENVIRONMENT HAS
BECOME CHARACTERIZED BY STRONG INSTABILITY, WITH MLCAPE VALUES
AS HIGH AS 3000 J/KG. DEEP LAYER SHEAR IS GENERALLY ON THE ORDER
OF 40-45 KT TO THE SOUTH OF THE FRONTAL BOUNDARY.
DESPITE NEBULOUS FORCING, SCATTERED THUNDERSTORMS, SOME SEVERE,
HAVE DEVELOPED ACROSS PORTIONS OF EASTERN PA INTO NORTHERN NJ.
THIS ACTIVITY WILL SPREAD SOUTHEASTWARD THROUGH LATE THIS
EVENING. GIVEN THE STRONG INSTABILITY AND SHEAR, A MIX OF
SUPERCELLS AND LINE SEGMENTS WILL CONTINUE TO BE THE STORM MODE.
SOME GUIDANCE SUGGESTS UPSCALE GROWTH INTO A QLCS, BUT SO FAR
THIS HAS YET TO OCCUR AND IT IS NOT GUARANTEED. DAMAGING WINDS
AND A FEW INSTANCES OF SEVERE HAIL ARE THE EXPECTED PRIMARY
HAZARDS. HOWEVER, A TORNADO OR TWO CANNOT BE RULED OUT WITH ANY
SUPERCELLS AS ESRH IS ON THE ORDER OF 100-125 M2/S2.
STORMS SHOULD CLEAR THE REGION BY MIDNIGHT OR SHORTLY AFTER.
ONCE THE FRONT WORKS ITS WAY THROUGH THE AREA, MUCH OF THE
OVERNIGHT PERIOD TONIGHT WILL BE DRY. HOWEVER, THE MARINE LAYER
WILL SPREAD INLAND ACROSS MUCH OF THE AREA LEADING TO WIDESPREAD
LOW CLOUDS.
KEY MESSAGE 2...ON WEDNESDAY, A SHORTWAVE TROUGH COULD SPARK ANOTHER
ROUND OF SHOWERS AND STORMS, BUT IT WILL BE WORKING AGAINST A
RELATIVELY STABLE BOUNDARY LAYER.
IN THE WAKE OF THE STORMS TUESDAY NIGHT, THE FRONT IS EXPECTED TO
SINK BACK SOUTH OF THE REGION BY WEDNESDAY MORNING, LEAVING OUR
REGION IN THE RELATIVELY COOLER AND MORE STABLE AIR MASS NORTH OF
THE FRONT. THE NET RESULT IS THAT OUR REGION SHOULD BE IN
NORTHEASTERLY FLOW, AND RELATIVELY CLOUDY CONDITIONS FOR MUCH OF THE
DAY. AS A RESULT, SURFACE-BASED INSTABILITY IS GOING TO BE ALMOST
NON-EXISTENT, THOUGH MODEL SOUNDINGS DO SHOW ELEVATED INSTABILITY
FOR PARCELS ABOVE 900 MB.
CONSEQUENTLY, THE RISK FOR SEVERE STORMS IS STILL QUITE CONDITIONAL
AND UNCERTAIN. GIVEN HOW SHARP OF A MID LEVEL SHORT WAVE TROUGH IS
APPROACHING, THERE WILL BE AMPLE FORCING, BUT IT IS A QUESTION OF IF
THE ELEVATED INSTABILITY WILL BE ENOUGH TO SUSTAIN STORMS IN OUR
REGION.
KEY MESSAGE 3...HOT AND HUMID CONDITIONS ARE FORECAST ACROSS THE
REGION ON THURSDAY.
AFTER A COOL DOWN ON WEDNESDAY FOR MOST NEIGHBORHOODS (5 TO 10
DEGREES LOWER - LESS ACROSS DELMARVA), HOT AND HUMID CONDITIONS ARE
ONCE AGAIN EXPECTED ACROSS THE REGION ON THURSDAY AS THE FRONTAL
BOUNDARY LIFTS NORTH. WITH THE FRONT TO THE NORTH, HIGH TEMPERATURES
ARE FORECAST TO CLIMB INTO THE UPPER 80S TO MID 90S FOR MANY AREAS
(AROUND 80 OR LOW 80S FAR N AND W). THESE TEMPERATURES COMBINED WITH
DEWPOINTS IN THE LOW TO MID 70S WILL AGAIN RESULT IN HEAT INDICES
WELL INTO THE 90S TO LOW 100S SOUTH OF I-78, PERHAPS EVEN AS HIGH AS
105 DEGREES FOR DELMARVA.
ANOTHER HEAT ADVISORY MAY BE NEEDED FOR PORTIONS OF THE AREA ON
THURSDAY IF THIS TREND CONTINUES.
KEY MESSAGE 4...UNSETTLED CONDITIONS WILL CONTINUE ON THURSDAY WITH
THE POTENTIAL FOR SEVERE THUNDERSTORMS. SCATTERED THUNDERSTORMS ARE
AGAIN POSSIBLE ON FRIDAY, MAINLY FROM PHILADELPHIA SOUTH.
ANOTHER ROUND OF SEVERE THUNDERSTORMS ARE POSSIBLE ON THURSDAY.
FRIDAY COULD ALSO EXPERIENCE A FEW SEVERE STORMS ACROSS DELMARVA,
DEPENDING ON HOW QUICKLY THE FRONTAL BOUNDARY PUSHES SOUTH.
SPC HAS A SLIGHT RISK (LEVEL 2 OUT OF 5) FOR SEVERE THUNDERSTORMS
ON THURSDAY FROM ABOUT WILMINGTON TO WILDWOOD NJ SOUTHWARD AND A
MARGINAL RISK (LEVEL 1) TO THE NORTH OF THIS.
THE NORTHWEST FLOW PATTERN WILL REMAIN IN PLACE ON THURSDAY AND WILL
CONTINUE TO BE SUPPORTIVE OF ALL SEVERE THREATS, INCLUDING DAMAGING
WINDS, LARGE HAIL, AND A FEW TORNADOES, DEPENDING ON HOW ALL THE
MESOSCALE DETAILS PAN OUT. THE THREAT FOR FLASH FLOODING IS
TYPICALLY LOWER WITH THESE PATTERNS, BUT NOT ZERO. TRAINING CAN
STILL OCCUR AND A SINGLE LOCALE COULD HAVE MULTIPLE DAYS WITH HEAVY
RAINFALL.
FRIDAY'S SPC'S 15% PROBABILITIES FOR SEVERE THUNDERSTORMS HAVE
SHIFTED JUST SOUTH OF OUR DELMARVA ZONES, THOUGH THERE IS STILL SOME
UNCERTAINTY WITH THIS. OUR LATEST FORECAST HAS ABOUT A 30-40% CHANCE
OF SHOWERS AND THUNDERSTORMS SOUTH OF ABOUT PHILADELPHIA.
KEY MESSAGE 5...THE LABOR DAY WEEKEND WILL FEATURE MOSTLY DRY
WEATHER WITH AT OR BELOW NORMAL TEMPERATURES AND LOWER HUMIDITY.
BY SATURDAY, CURRENT MODEL CONSENSUS INDICATES THE FRONTAL BOUNDARY
WILL BE PUSHING SOUTH OF OUR REGION WITH CANADIAN HIGH PRESSURE
BUILDING ACROSS THE NORTHEAST AND MID-ATLANTIC. THIS WILL LARGELY
END ANY SHOWER AND THUNDERSTORM POTENTIAL. THUS, LABOR DAY WEEKEND
IS STILL SHAPING UP TO FEATURE NICE WEATHER, WITH TEMPERATURES
TRENDING AT OR SLIGHTLY BELOW NORMAL AND LOWER HUMIDITY. THE ONLY
ROAD BUMP AT THE MOMENT, COULD BE A COLD FRONT THAT APPROACHES THE
FORECAST AREA VERY LATE ON MONDAY.
AVIATION /00Z WEDNESDAY THROUGH SUNDAY/
TONIGHT...EXPECT A BROKEN LINE OF STORMS TO MOVE FROM NORTH TO
SOUTH ACROSS THE TAF SITES THROUGH 04Z. AHEAD OF THIS LINE,
EXPECT VFR CONDITIONS. WITH THIS LINE, VISIBILITY RESTRICTIONS
ARE LIKELY. IN THE WAKE OF STORMS THIS EVENING, CEILINGS ARE
EXPECTED TO RAPIDLY DROP TO MVFR OR IFR BETWEEN 06-09Z. WINDS
SHOULD BE MOSTLY OUT OF THE SW AHEAD OF THE STORMS AT 5-10 KTS.
WITH THE STRONGEST STORMS, STRONG TO SEVERE WIND GUSTS ARE
POSSIBLE. BEHIND THE LINE OF STORMS, WINDS WILL LIKELY BRIEFLY
BECOME LIGHT AND VARIABLE FOR A TIME BEFORE SETTLING OUT OF THE
NORTHEAST AROUND 5 KTS. LOW CONFIDENCE.
WEDNESDAY...MVFR CEILINGS MAY REMAIN THROUGH MUCH OF THE DAY.
THERE IS A 20 TO 40% CHANCE FOR SHOWERS AND STORMS THROUGH THE
DAY TIME THAT COULD ALSO RESULT IN RESTRICTIONS, HOWEVER, THERE
IS CONSIDERABLE UNCERTAINTY TO THE EXTENT OF STORM DEVELOPMENT
TOMORROW. WINDS THROUGH MUCH OF THE MORNING ARE EXPECTED TO BE
OUT OF THE NORTHEAST AT 5-10 KTS, BEFORE SHIFTING MORE
SOUTHEASTERLY AFTER 17-18Z. LOW CONFIDENCE.
OUTLOOK...
THURSDAY AND FRIDAY...SUB-VFR CONDITIONS ARE POSSIBLE IN SHOWERS AND
THUNDERSTORMS EACH DAY (20-40% CHANCE), MAINLY DURING THE AFTERNOON
TO EVENING HOURS.
SATURDAY AND SUNDAY...PRIMARILY VFR CONDITIONS EXPECTED.
MARINE
WINDS AND SEAS ARE EXPECTED TO STAY BELOW SMALL CRAFT ADVISORY
CONDITIONS. HOWEVER, GUSTY AND ERRATIC WINDS ARE POSSIBLE IN THE
VICINITY OF ANY STORMS, PARTICULARLY TONIGHT.
OUTLOOK...
THURSDAY THROUGH SUNDAY...SUB-SCA CONDITIONS ARE EXPECTED THROUGH
THE PERIOD. THERE IS A CHANCE (40 TO 50%) FOR THUNDERSTORMS
THURSDAY, MAINLY IN THE AFTERNOON AND EVENING HOURS. FOR FRIDAY, THE
CHANCE OF THUNDERSTORMS (30 TO 40%) SHIFTS SOUTH A BIT, BASICALLY
EXTENDING FROM MANASQUAN INLET, NJ DOWN TO FENWICK ISLAND, DE.
RIP CURRENTS...
ON WEDNESDAY, NORTHEAST FLOW WILL RANGE FROM 10 TO 15 MPH WITH
GUSTS UP TO 20 MPH ALONG THE NEW JERSEY COAST. THERE WILL BE
SOUTHEAST SWELLS WITH A PERIOD AROUND 10 SECONDS AND BREAKING
WAVES OF 2 TO 3 FEET. AS A RESULT, THERE IS A MODERATE RISK FOR
THE DEVELOPMENT OF DANGEROUS AND LIFE THREATENING RIP CURRENTS
FOR THE JERSEY SHORE ALONG MONMOUTH, OCEAN, AND ATLANTIC
COUNTIES, AND A LOW RISK FOR THE DEVELOPMENT OF DANGEROUS AND
LIFE THREATENING RIP CURRENTS FOR THE JERSEY SHORE IN CAPE MAY
COUNTY AND DELAWARE BEACHES.
FOR THURSDAY, WINDS BECOME SOUTHWEST AT 10 TO 15 MPH WITH GUSTS
UP TO 20 MPH ALONG THE JERSEY SHORE. BREAKING WAVES WILL RANGE
FROM 1 TO 3 FEET WITH LIGHT EASTERLY SWELLS WITH A PERIOD AROUND
6 SECONDS. AS A RESULT, THERE IS A MODERATE RISK FOR THE
DEVELOPMENT OF DANGEROUS AND LIFE THREATENING RIP CURRENTS FOR
THE JERSEY SHORE ALONG MONMOUTH, OCEAN, AND ATLANTIC COUNTIES,
AND A LOW RISK FOR THE DEVELOPMENT OF DANGEROUS AND LIFE
THREATENING RIP CURRENTS FOR THE JERSEY SHORE IN CAPE MAY COUNTY
AND DELAWARE BEACHES.
PHI WATCHES/WARNINGS/ADVISORIES
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...NONE.
DISCUSSION...COOPER/WFO PHI
AVIATION...COOPER/WFO PHI
MARINE...MPS
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page