308
FXUS61 KPHI 022320
AFDPHI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
720 PM EDT WED SEP 2 2026
WHAT HAS CHANGED
THE AVIATION SECTION WAS UPDATED FOR THE 00Z TAFS.
KEY MESSAGES
1. THROUGH TONIGHT, A SHORTWAVE TROUGH COULD SPARK ANOTHER
ROUND OF SHOWERS AND STORMS, BUT IT WILL BE WORKING AGAINST A
RELATIVELY STABLE BOUNDARY LAYER.
2. HOT AND HUMID CONDITIONS ARE FORECAST ACROSS THE REGION ON
THURSDAY.
3. UNSETTLED CONDITIONS WILL CONTINUE ON THURSDAY WITH THE
POTENTIAL FOR SEVERE THUNDERSTORMS. SCATTERED THUNDERSTORMS ARE
AGAIN POSSIBLE ON FRIDAY, MAINLY SOUTH OF PHILADELPHIA.
4. THE LABOR DAY WEEKEND WILL FEATURE MOSTLY DRY WEATHER WITH
AT OR BELOW NORMAL TEMPERATURES AND LOWER HUMIDITY.
DISCUSSION
KEY MESSAGE 1...THROUGH TONIGHT, A SHORTWAVE TROUGH COULD SPARK
ANOTHER ROUND OF SHOWERS AND STORMS, BUT IT WILL BE WORKING AGAINST
A RELATIVELY STABLE BOUNDARY LAYER.
AN ADDITIONAL ROUND OF SEVERE THUNDERSTORMS IS POSSIBLE TONIGHT.
MODEL GUIDANCE HAS STRUGGLED WITH THE CONVECTION TODAY WITH
UNCERTAINTY CONTINUING INTO TONIGHT. CURRENTLY, IT LOOKS AS THOUGH
THE BACKDOOR COLD FRONT MOVES BACK THROUGH THE AREA AS A WARM FRONT
LATE THIS EVENING INTO TONIGHT. CONFIDENCE IN DETAILS REGARDING THIS
REMAINS RELATIVELY LOW, BUT SHOULD THE REGION EXPERIENCE MORE
DESTABILIZATION AND EROSION OF THE MARINE LAYER THAN IS CURRENTLY
ANTICIPATED, STORMS WILL BE CAPABLE OF DAMAGING WINDS, SOME HAIL,
AND PERHAPS AN ISOLATED TORNADO. THE GREATER RISK OF ANY SEVERE
STORMS WILL BE TOWARD OUR SOUTHERN AND WESTERN ZONES. AS OF RIGHT
NOW, MODEL SOUNDINGS CONTINUE TO SHOW A STEP INVERSION INTO TONIGHT
WITH INSTABILITY REMAINING ELEVATED. HOWEVER, FORCING AND SHEAR
VALUES REMAIN FAVORABLE. LOCALLY HEAVY RAINFALL WILL ALSO BE A
THREAT WITH ANY TRAINING SHOWERS AND STORMS, EVEN IF A SEVERE
THUNDERSTORM THREAT DOES NOT MATERIALIZE. PORTIONS OF EASTERN PA
HAVE BEEN HIGHLIGHTED IN A SLIGHT (LEVEL 2 OUT OF 4) RISK FOR
EXCESSIVE RAINFALL, WHICH COULD LEAD TO LOCALIZED FLASH FLOODING.
SPC MAINTAINS A SLIGHT RISK (LEVEL 2 OUT OF 5) FOR SEVERE
THUNDERSTORMS FOR MUCH OF OUR AREA, BUT AGAIN, THIS RISK IS HIGHLY
CONDITIONAL AND LOW CONFIDENCE INTO TONIGHT.
KEY MESSAGE 2...HOT AND HUMID CONDITIONS ARE FORECAST ACROSS THE
REGION ON THURSDAY.
FOLLOWING THE BRIEF COOL DOWN IN THE MARINE LAYER TODAY FOR MOST
AREAS, HOT AND HUMID CONDITIONS ARE ONCE AGAIN EXPECTED ACROSS THE
REGION ON THURSDAY AS THE FRONTAL BOUNDARY LIFTS NORTH AGAIN. WITH
THE FRONT TO THE NORTH, HIGH TEMPERATURES ARE FORECAST TO CLIMB INTO
THE UPPER 80S TO MID 90S FOR MANY AREAS (LOW TO MID 80S FAR NORTH).
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.
A HEAT ADVISORY REMAINS IN EFFECT FOR PORTIONS OF SOUTHEASTERN PA
AND NJ. THIS ADVISORY HAS BEEN EXPANDED INTO DELMARVA GIVEN THE
CONTINUED TREND OF FORECAST HEAT INDICES NEAR 105 DEGREES. NORTH OF
THE CURRENT ADVISORY AREA, MAXIMUM HEAT INDICES ARE FORECAST TO TOP
OUT IN THE LOW TO MID 90S, THUS THE ADVISORY IS UNLIKELY TO NEED TO
BE EXPANDED FARTHER NORTH.
KEY MESSAGE 3...UNSETTLED CONDITIONS WILL CONTINUE ON THURSDAY WITH
THE POTENTIAL FOR SEVERE THUNDERSTORMS. SCATTERED THUNDERSTORMS ARE
AGAIN POSSIBLE ON FRIDAY, MAINLY SOUTH OF PHILADELPHIA.
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 FOR DELMARVA AND A MARGINAL RISK (LEVEL 1) TO AS FAR NORTH
AS THE I-78 CORRIDOR.
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 ISOLATED 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 OUTLOOK ONLY HAS A SMALL PORTION OF THE MARYLAND
EASTERN SHORE AND SOUTHERN DELAWARE IN A MARGINAL RISK FOR
SEVERE WEATHER. TH REST OF THE AREA INCLUDES GENERAL
THUNDERSTORMS (NO SEVERE RISK), THOUGH THERE IS STILL SOME
UNCERTAINTY WITH THIS. OUR LATEST FORECAST HAS ABOUT A 40-60%
CHANCE OF SHOWERS AND THUNDERSTORMS FROM ABOUT I-78 ON
SOUTHWARDS, INCLUDING THE ENTIRE PHILADELPHIA METRO AREA.
KEY MESSAGE 4...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 WELL 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
ON TUESDAY.
AVIATION /00Z THURSDAY THROUGH MONDAY/
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY AND SURROUNDING AREAS.
TONIGHT...IFR CIGS, POSSIBLY AS LOW AS LIFR. SEVERAL ROUNDS OF
SHRA/TSRA WILL IMPACT THE TERMINALS TONIGHT, THE FIRST BEING
FROM 02Z TO 06Z AT KRDG/KABE, 03Z TO 07Z AT THE I-95 CORRIDOR
TERMINALS, AND 04Z TO 08Z AT KMIV/KACY. THE SECOND ROUND WILL
IMPACT THE TERMINALS AROUND 12Z. VSBY RESTRICTIONS IN THE
STRONGER TSRA, AND VSBY RESTRICTIONS IN BR. LGT/VRB WINDS. LOW
CONFIDENCE.
THURSDAY...IFR CIGS IN THE MORNING, LIFTING TO VFR AFTER 15Z.
SHRA/TSRA MAY IMPACT THE TERMINALS IN THE 12Z TO 16Z TIMEFRAME,
AND THEN THE NEXT ROUND OF CONVECTION MAY IMPACT KRDG/KABE
AFTER 22Z. SW WINDS 5 TO 10 KT. MODERATE CONFIDENCE.
THURSDAY NIGHT...SHRA/TSRA TAPER OFF BY 06Z. VFR. LIGHT W TO NW
WINDS. MODERATE CONFIDENCE.
OUTLOOK...
FRIDAY...SUB-VFR CONDITIONS ARE POSSIBLE IN SHOWERS AND
THUNDERSTORMS (40-60% CHANCE), MAINLY DURING THE AFTERNOON TO
EVENING HOURS.
SATURDAY THROUGH MONDAY...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 AND AGAIN TOMORROW
AFTERNOON/EVENING.
OUTLOOK...
THURSDAY NIGHT THROUGH MONDAY...SUB-SCA CONDITIONS ARE EXPECTED
THROUGH THE PERIOD. THERE IS A CHANCE (20 TO 40%) FOR
THUNDERSTORMS TO LINGER THURSDAY NIGHT. FOR FRIDAY, THE CHANCE
OF THUNDERSTORMS IS AROUND 30 TO 50%, MAINLY IN THE AFTERNOON
AND EARLY EVENING HOURS.
RIP CURRENTS...
FOR THURSDAY, WINDS WILL MAINLY BE OUT OF THE SOUTH/SOUTHWEST
AROUND 10 MPH OR LESS. BREAKING WAVES WILL BE 2 FEET OR LESS
WITH A DOMINANT WAVE PERIOD OF 9 SECONDS. GIVEN LIGHT WINDS, AND
NOT MUCH IN TERMS OF WAVE HEIGHTS, ELECTED FOR A LOW RISK FOR
RIP CURRENTS AT ALL BEACHES.
SIMILAR CONDITIONS EXPECTED FRIDAY THOUGH WINDS TURN MORE
OFFSHORE, LOWERING THE RIP CURRENT RISK EVEN FURTHER. WILL
CONTINUE THE LOW RISK THROUGH THE END OF THE WEEK FOR THE JERSEY
SHORE AND DELAWARE BEACHES.
PHI WATCHES/WARNINGS/ADVISORIES
PA...HEAT ADVISORY FROM 11 AM TO 8 PM EDT THURSDAY FOR PAZ060-070-
071-101>104-106.
NJ...HEAT ADVISORY FROM 11 AM TO 8 PM EDT THURSDAY FOR NJZ013>015-
017>020-027.
DE...HEAT ADVISORY FROM 11 AM TO 8 PM EDT THURSDAY FOR DEZ001>003.
MD...HEAT ADVISORY FROM 11 AM TO 8 PM EDT THURSDAY FOR MDZ012-015-
019-020.
MARINE...NONE.
DISCUSSION...AKL/GUZZO
AVIATION...AKL/GUZZO/MPS
MARINE...AKL/GUZZO/HOEFLICH
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