994
FXUS61 KPHI 082221
AFDPHI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
621 PM EDT SAT AUG 8 2026
WHAT HAS CHANGED
REMAINDER OF SEVERE THUNDERSTORM WATCH ACROSS THE DELMARVA WAS
ALLOWED TO EXPIRE AT 6 PM.
KEY MESSAGES
1. HOT AND HUMID CONDITIONS ARE EXPECTED TO PERSIST THROUGH
TUESDAY OF NEXT WEEK, THOUGH AN IMPROVEMENT IN HUMIDITY IS
EXPECTED SUNDAY INTO MONDAY.
2. SUNDAY STILL LOOKS TO BE LARGELY DRY, THEN DAILY CHANCES FOR
SHOWERS AND THUNDERSTORMS WILL RETURN MONDAY AND INTO THE
MIDDLE OF NEXT WEEK. THERE IS A RISK FOR STRONG TO SEVERE
THUNDERSTORMS AS WELL AS A MARGINAL RISK FOR LOCALIZED HEAVY
RAINFALL LEADING TO FLASH FLOODING.
DISCUSSION
KEY MESSAGE 1...HOT AND HUMID CONDITIONS ARE EXPECTED TO PERSIST
THROUGH TUESDAY OF NEXT WEEK, THOUGH AN IMPROVEMENT IN HUMIDITY IS
EXPECTED SUNDAY INTO MONDAY.
A RELATIVELY STAGNANT SYNOPTIC PATTERN WILL REMAIN IN PLACE ACROSS
OUR REGION. QUASI ZONAL MID AND UPPER LEVEL FLOW WILL BE IN PLACE
THROUGH THE MIDDLE OF NEXT WEEK AS BERMUDA HIGH PRESSURE PERSISTS
OFFSHORE. THIS WILL KEEP A STEADY STREAM OF VERY WARM AND MOIST AIR
IN PLACE ACROSS THE REGION THROUGH THE PERIOD.
A PROLONGED PERIOD OF HOT AND HUMID CONDITIONS WILL CONTINUE FOR THE
NEXT SEVERAL DAYS. WITH DEWPOINTS REMAINING IN THE LOW TO MID 70S
AND HIGHS IN THE UPPER 80S TO LOW 90S TODAY, HEAT INDICES WILL AGAIN
BE NEAR 100 DEGREES THIS AFTERNOON, MAINLY ALONG AND SOUTHEAST OF
THE I-95 CORRIDOR. A WEAK COLD FRONTAL PASSAGE SUNDAY WILL HELP
USHER IN SLIGHTLY DRIER AIR AND ALLOW DEWPOINTS TO MIX OUT DURING
THE AFTERNOON HOURS BOTH SUNDAY AND MONDAY. THIS WILL GIVE SOME
SLIGHT REPRIEVE FROM THE EXCESSIVE HUMIDITY, THOUGH HIGHS WILL STILL
BE IN THE UPPER 80S TO LOW OR EVEN MID 90S. THE LOWER DEWPOINTS
SUNDAY AND MONDAY WILL RESULT IN MAXIMUM HEAT INDICES MAINLY IN THE
MID TO UPPER 90S, THOUGH COULD GET NEAR 100 DEGREES IN DELMARVA.
SINCE THE FORECAST IS DECIDEDLY BELOW HEAT ADVISORY CRITERIA, WE'VE
OPTED NOT TO EXTEND IT TO COVER ADDITIONAL DAYS AT THIS TIME, THOUGH
IT WILL STILL BE HOT AND HUMID.
FROM THIS FORECAST UPDATE, THERE REMAINS SOME MOISTURE ADVECTION
AHEAD OF THE COLD FRONT. HOWEVER, THE COLD FRONT TIMING LOOKS A BIT
EARLIER TUESDAY WHICH HAS RESULTED IN SOME LOWER TEMPERATURES AND
HEAT INDEX VALUES. TEMPERATURES INTO THE MID 80S TO LOW 90S FOR MANY
AND HEAT INDEX VALUES PEAKING NEAR OR IN THE 90S FOR MANY. ONCE THE
COLD FRONT FULLY COMES THROUGH, WE WILL SEE A CONTINUED SLIGHT
REDUCTION IN TEMPERATURES INTO WEDNESDAY AND THURSDAY. HIGHS BY
WEDNESDAY AND THURSDAY ARE MOSTLY IN THE MID TO UPPER 80S, WHICH
WILL BE CLOSER TO AVERAGE FOR EARLY TO MID AUGUST.
KEY MESSAGE 2...SUNDAY STILL LOOKS TO BE LARGELY DRY, THEN
DAILY CHANCES FOR SHOWERS AND THUNDERSTORMS WILL RETURN MONDAY
AND INTO THE MIDDLE OF NEXT WEEK. THERE IS A RISK FOR STRONG TO
SEVERE THUNDERSTORMS AS WELL AS A MARGINAL RISK FOR LOCALIZED
HEAVY RAINFALL LEADING TO FLASH FLOODING.
SHOWERS AND STORM THREAT HAS CEASED FOR THE EVENING. WEATHER
SHOULD REMAIN MOSTLY TRANQUIL THIS EVENING INTO THE OVERNIGHT
WITH SOME AREAS OF PATCHY FOG POSSIBLE.
WE LOOK TO HAVE A WEAK COLD FRONTAL PASSAGE BY SUNDAY, USHERING IN
SLIGHTLY DRIER AIR. THIS COMBINED WITH SUBTLE SUBSIDENCE ALOFT WILL
HELP BRIEFLY LIMIT CONVECTION POTENTIAL ON SUNDAY, THOUGH CANNOT
COMPLETELY RULE OUT SOME ISOLATED SEA BREEZE CONVECTION IN THE
AFTERNOON.
BETTER SUPPORT FOR FORCING ALOFT WILL RETURN BY LATE MONDAY AS MEAN
FLOW SHIFTS MORE WESTERLY AND MID LEVEL FLOW INCREASES.
AT THIS POINT THOUGH, IT APPEARS THE GREATER THREAT OF STORMS WILL
BE TO OUR WEST ON MONDAY WHERE SPC HAS A MARGINAL RISK HIGHLIGHTED.
STILL COULD GET SOME ISOLATED STORMS, BUT MONDAY IS TRENDING DRIER
LOCALLY AS THE LINGERING LOWER DEWPOINTS SHOULD LIMIT OUR
INSTABILITY A BIT.
RECENT FORECAST TRENDS HAVE RESULTED IN LOWER INSTABILITY COMPARED
TO PREVIOUS MODEL RUNS ON TUESDAY GIVEN THE TIMING OF THE COLD FRONT
TO BE EARLIER. THERE DOES REMAIN UNCERTAINTY AROUND THE SPECIFIC
TIMING DETAILS OF THE FRONT AT THIS TIME. HOWEVER, WITH THAT SAID,
THERE IS STILL BETTER STORM CHANCES ON TUESDAY COMPARED TO MONDAY.
WITH THE STRONGER MID LEVEL FLOW ALOFT, SEVERE THUNDERSTORMS STILL
LOOK TO BE A GREATER THREAT COMPARED TO FLASH FLOODING, BUT THESE
DETAILS CONTINUE TO REMAIN UNCLEAR.
BEHIND THE SOMEWHAT STRONGER COLD FRONT THAT LOOKS TO COME THROUGH
TUESDAY INTO WEDNESDAY, WHICH WILL HELP BREAK THE EXCESSIVE HEAT AND
HUMIDITY SOME, THE PATTERN ALOFT MAY STILL SUPPORT DIURNALLY DRIVEN
CONVECTION.
AVIATION /22Z SATURDAY THROUGH THURSDAY/
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY AND SURROUNDING AREAS.
TODAY...ISOLATED TO SCATTERED THUNDERSTORMS IN THE AFTERNOON
MAY CAUSE LOCALIZED RESTRICTIONS, HOWEVER CONFIDENCE ON WHERE
ANY OF THIS MAY DEVELOP IS LOW. SOUTHWEST WINDS NEAR 10 KTS,
WITH GUSTS UP TO 18 KTS. STRONG GUSTS UP TO 40-50 KTS POSSIBLE
WITH ANY THUNDERSTORMS. HIGH CONFIDENCE IN PREVAILING VFR, LOW
CONFIDENCE ON SHOWER AND STORM DETAILS.
TONIGHT...PREVAILING VFR, THOUGH SOME PATCHY FOG MAY DEVELOP.
SOME ISOLATED SHOWERS AND THUNDERSTORMS COULD LINGER THROUGH
06Z, BUT CONFIDENCE ON THIS IS TOO LOW TO INCLUDE A TAF MENTION
AT THIS TIME. SOUTHWEST WINDS NEAR 5 KTS OR LESS. MODERATE
CONFIDENCE.
SUNDAY...PREVAILING VFR. CAN'T RULE OUT AN AFTERNOON
THUNDERSTORM BRINGING RESTRICTIONS TO KACY OR KMIV BUT
CONFIDENCE IS TOO LOW TO INCLUDE AT THIS TIME. WESTERLY WINDS
AROUND 5-10 KTS. MODERATE CONFIDENCE.
OUTLOOK...
SUNDAY NIGHT...VFR CONDITIONS EXPECTED.
MONDAY-THURSDAY...MOSTLY VFR EXCEPT RESTRICTIONS POSSIBLE WITH
AFTERNOON/EVENING SHOWERS AND THUNDERSTORMS.
MARINE
OUTSIDE OF ANY STORMS, SOUTHWEST TO SOUTH WINDS AROUND 10-20 KT
WITH SEAS OF 2-4 FEET ARE EXPECTED THROUGH SUNDAY.
OUTLOOK...
MONDAY THROUGH THURSDAY...NO PREVAILING MARINE HAZARDS EXPECTED.
THUNDERSTORMS POSSIBLE TUESDAY AFTERNOON INTO TUESDAY NIGHT AND
AGAIN WEDNESDAY NIGHT.
RIP CURRENTS...
FOR SUNDAY...SOUTHWEST WINDS WILL PREVAIL AROUND 10 TO 15 MPH.
BREAKING WAVE HEIGHTS GENERALLY AROUND 1 TO 2 FEET, WITH SOME
LOCALIZED BEACHES UP TO 3 FEET AS WELL AS A SOUTHERLY 2 TO 3
FOOT SWELL WITH A PERIOD AROUND 6 TO 8 SECONDS. GIVEN THESE
CONDITIONS, HAVE OPTED TO GO WITH A LOW RISK FOR THE DEVELOPMENT
OF DANGEROUS RIP CURRENTS AT BOTH THE JERSEY SHORE AND DELAWARE
BEACHES.
FOR MONDAY...SOUTH-SOUTHWEST WINDS WILL BE AROUND 5 TO 10 MPH IN
THE MORNING, INCREASING TO AROUND 10 TO 20 MPH IN THE AFTERNOON.
BREAKING WAVE HEIGHTS WILL GENERALLY RANGE BETWEEN 1 TO 2 FEET,
WITH MULTIPLE SWELL GROUPS AND PERIODS. GIVEN THESE CONDITIONS,
HAVE OPTED TO GO WITH A LOW RISK FOR THE DEVELOPMENT OF
DANGEROUS RIP CURRENTS AT ALL BEACHES.
FOR SPECIFIC BEACH FORECASTS, VISIT WEATHER.GOV/BEACH/PHI
PHI WATCHES/WARNINGS/ADVISORIES
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...NONE.
DISCUSSION...AKL/DESILVA/GUZZO/STAARMANN
AVIATION...AKL/GUZZO
MARINE...AKL/DESILVA/GUZZO
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