573
FXUS61 KPHI 271549
AFDPHI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
1149 AM EDT MON JUL 27 2026
WHAT HAS CHANGED
UPDATED WORDING FOR KEY MESSAGE 1.
KEY MESSAGES
1. AN ACTIVE AND UNSETTLED PATTERN BEGINS TODAY, WITH A MARGINAL
RISK FOR SEVERE WEATHER AND EXCESSIVE RAINFALL.
2. MOST IMPACTFUL WEATHER LIKELY COMES ON TUESDAY WITH THE
HIGHEST CHANCE FOR SEVERE WEATHER AND FLASH FLOODING. UNSETTLED
WEATHER CONTINUES THROUGH MID-WEEK THOUGH .
DISCUSSION
KEY MESSAGE 1... AN ACTIVE AND UNSETTLED PATTERN BEGINS TODAY,
WITH A MARGINAL RISK FOR SEVERE WEATHER AND EXCESSIVE RAINFALL.
AS A STRONG UPPER-LEVEL RIDGE EXPANDS INTO THE PLAINS EARLY
THIS WEEK, NORTHWESTERLY FLOW ALOFT WILL OCCUR ACROSS MUCH OF
THE EAST. THIS RIDGE GETS PUSHED BACK SOME AS A STRONG UPPER-
LEVEL TROUGH IN EASTERN CANADA SENDS SPOKES OF ENERGY
SOUTHEASTWARD ACROSS THE GREAT LAKES AND NORTHEAST. SOME
GUIDANCE MAINTAINS A VIGOROUS SHORTWAVE RIDING OVER THE RIDGE
AND SLIDING SOUTHEASTWARD ACROSS THE GREAT LAKES TODAY AND THEN
ACROSS THE NORTHEAST DURING TUESDAY. THIS RESULTS IN SOME MODEL
SOLUTIONS CONTINUING TO CLOSE OFF THE TROUGH ACROSS THE
NORTHEAST TUESDAY INTO WEDNESDAY. SOME OTHER GUIDANCE IS SLOWER
AND WEAKER AND THUS DOES NOT CLOSE IT OFF OR BRIEFLY CLOSES IT
OFF A DAY OR TWO LATER. THE UPPER-LEVEL SYSTEM WILL DRIVE
SURFACE LOW PRESSURE AND A COLD FRONT OUR WAY TUESDAY INTO
WEDNESDAY. IT WILL BECOME MUCH MORE HUMID DURING THE FIRST HALF
OF NEXT WEEK, WITH DEW POINTS LOOKING TO SURGE ON TUESDAY.
THESE FACTORS WILL LEAD TO THE DEVELOPMENT OF SHOWERS AND
THUNDERSTORMS ACROSS THE AREA TODAY. THE LATEST RADAR IMAGES AS
OF 1140AM SHOW THAT THE FIRST ECHOS HAVE ALREADY DEVELOPED.
THE SETUP LOOKS TO BE A PULSY, SINGLE TO MULTI CELL CLUSTER
ENVIRONMENT WITH LOW SHEAR AND MODEST INSTABILITY, SIMILAR TO
WHAT WE HAVE SEEN EARLY THIS MORNING WITH SOME SEVERE
THUNDERSTORMS OVER THE EASTERN SHORE OF MD. DEEP LAYER SHEAR
WILL BE WEAK, ONLY AROUND 10-20 KTS. INSTABILITY LOOKS TO BE IN
THE 1000-2000 J/KG RANGE. DCAPE IS ALSO MODEST AROUND 500-1000
J/KG. THIS SETUP WILL FAVOR SCATTERED, HIT OR MISS TYPE SHOWERS
AND THUNDERSTORMS DEVELOPING DURING THE AFTERNOON HOURS, WITH A
MARGINAL RISK OF SEVERE THUNDERSTORMS. ANY STRONGER STORMS COULD
PRODUCE ISOLATED STRONG TO MARGINALLY SEVERE WIND GUSTS AND
BRIEF HEAVY DOWNPOURS. CAMS HAVE BEEN FOCUSING DEVELOPMENT
MAINLY ALONG THE SEA AND BAY BREEZES, BUT LINGERING OUTFLOW
BOUNDARIES FROM CONVECTION THIS MORNING COULD ALSO BE THE NEXUS
FOR CONVECTIVE INITIATION. OUR ENTIRE AREA IS OUTLOOKED IN A
MARGINAL RISK (LEVEL 1 OUT OF 5) FOR SEVERE THUNDERSTORMS TODAY.
AN EXCESSIVE RAINFALL OUTLOOK WAS REINTRODUCED ACROSS DELAWARE
AND A SLIVER OF THE EASTERN SHORE OF MD AS OF 11AM.
KEY MESSAGE 2...MOST IMPACTFUL WEATHER LIKELY COMES ON TUESDAY
WITH THE HIGHEST CHANCE FOR SEVERE WEATHER AND FLASH FLOODING.
UNSETTLED WEATHER CONTINUES THROUGH MID-WEEK THOUGH .
TUESDAY LOOKS TO FEATURE THE MOST WIDESPREAD SHOWERS AND
THUNDERSTORMS. HEIGHT FALLS AND JET DYNAMICS ALOFT WILL FAVOR
CONVECTIVE DEVELOPMENT NEARLY ALL DAY AS SURFACE LOW PRESSURE
DEVELOPS JUST TO OUR WEST. THIS WILL KEEP A STEADY STREAM OF
WARM, MOIST AIR PUMPING INTO THE AREA AND KEEPING THE
ENVIRONMENT CONDITIONALLY UNSTABLE DESPITE CLOUD COVER. PWATS
WILL RISE TO NEAR 2" BY THE END OF THE DAY. SOME MODELS SUGGEST
WE COULD HAVE A STALLED OR SLOW MOVING FRONTAL BOUNDARY ACROSS
THE CENTRAL OR NORTHERN PORTION OF THE FORECAST AREA, WHICH
COULD ACT AS A FOCUSING MECHANISM FOR HEAVY RAINFALL. HEAVY
RAIN LEADING TO FLASH FLOODING COULD END UP BEING A BIGGER
CONCERN AND GREATER IMPACT THAN THE SEVERE THUNDERSTORM THREAT.
LONG STORY SHORT, A VERY ACTIVE DAY IS EXPECTED CONVECTION
WISE ON TUESDAY. A DUE SOUTHERLY SURFACE FLOW AND THE DYNAMICS
ALOFT WILL FAVOR AREAS ALONG AND NORTHWEST OF THE I-95 CORRIDOR
AND/OR THE FRONTAL BOUNDARY TO BE THE FOCUS OF THE HEAVIEST
RAIN, AND AREAS ALONG AND SOUTHEAST OF THE I-95 CORRIDOR AND/OR
THE FRONTAL BOUNDARY WHERE CONVECTION IS LESS MESSY AND THE
ENVIRONMENT A BIT LESS CONTAMINATED BEING THE GREATER SEVERE
THUNDERSTORM THREAT DEPENDING ON EXACTLY HOW THE CONVECTION
EVOLVES. THAT STILL REMAINS A LITTLE UNCLEAR AT THE MOMENT, AND
MAY DEPEND ON HOW STORMS EVOLVE UPSTREAM MONDAY AND MONDAY
NIGHT.
WPC HAS OUTLOOKED MOST OF OUR AREA OUTSIDE OF CENTRAL/SOUTHERN
DELMARVA IN A SLIGHT RISK (LEVEL 2 OUT OF 4) FOR EXCESSIVE
RAINFALL FOR TUESDAY. SPC HAS OUTLOOKED THE SOUTHERN HALF OF OUR
AREA FROM THE PHILLY METRO AND SOUTH IN A SLIGHT RISK (LEVEL 2
OUT OF 5) FOR SEVERE THUNDERSTORMS ON TUESDAY.
ON WEDNESDAY, LOW PRESSURE LOOKS TO BE OFFSHORE TO OUR EAST.
SCATTERED SHOWERS AND STORMS WILL LIKELY DEVELOP AGAIN BY
AFTERNOON, AT LEAST ACROSS OUR NJ AND PA ZONES, BUT THE SEVERE
THUNDERSTORM THREAT WILL BE LOWER GIVEN LOWER INSTABILITY. WILL
HAVE TO MONITOR THE FLASH FLOOD THREAT THOUGH AS WPC HAS ADDED
THE NORTHERN PART OF OUR AREA IN A SLIGHT (LEVEL 2/4) RISK FOR
EXCESSIVE RAINFALL WITH A MARGINAL (1/4) RISK ELSEWHERE.
AS WE HEAD THROUGH THURSDAY AND FRIDAY, THE RISK OF SCATTERED
SHOWERS AND STORMS WILL SLOWLY DECLINE AS THE TUESDAY-WEDNESDAY
SYSTEM SLOWLY PUSHES EAST. DETAILS ON THE LATE WEEK PERIOD ARE
STILL VERY UNCERTAIN, HOWEVER. WE MAY BRIEFLY DRY OUT COMPLETELY
SATURDAY BEFORE THE NEXT SYSTEM APPROACHES SUNDAY.
AVIATION /15Z MONDAY THROUGH FRIDAY/
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY AND SURROUNDING AREAS.
THIS AFTERNOON...PRIMARILY VFR THOUGH SCATTERED SHOWERS AND
THUNDERSTORMS DEVELOP DURING THE EARLY AFTERNOON, MAINLY FOCUSED
FROM THE I-95 CORRIDOR AND POINTS EAST. CONVERTED THE PROB30 TO
TEMPO GROUPS FOR THE I-95 AND SOUTH JERSEY TERMINALS. THE MAIN
WINDOW WILL BE FROM 16Z-17Z TO ABOUT 22Z-23Z, WITH LINGERING
SHOWERS AFTER. LESSER CHANCES FOR SHOWERS/THUNDERSTORMS FOR THE
LEHIGH VALLEY TERMINALS, SO ELECTED TO GO WITH A VCSH GROUP FOR
NOW. WINDS OUT OF THE SOUTH/SOUTHWEST AROUND 5 TO 10 KT.
LOW/MODERATE CONFIDENCE.
TONIGHT...PRIMARILY VFR. CANNOT RULE OUT SOME PATCHY FOG AT ALL
TERMINALS (10-15%) BUT CONFIDENCE WAS NOT HIGH ENOUGH TO
INCLUDE IN THE TAFS AT THIS TIME. LIGHT SOUTHERLY WINDS 5 KT OR
LESS. LOW CONFIDENCE.
TUESDAY THROUGH TUESDAY NIGHT...PERIODS OF MVFR/IFR CONDITIONS
LIKELY WITH MULTIPLE ROUNDS OF SHOWERS AND THUNDERSTORMS
EXPECTED.
OUTLOOK...
WEDNESDAY THROUGH WEDNESDAY NIGHT...RESTRICTIONS POSSIBLE WITH
LINGERING SHOWERS AND LOW CLOUDS.
THURSDAY THROUGH FRIDAY...VFR. NO SIGNIFICANT WEATHER EXPECTED.
MARINE
SUB-SCA CONDITIONS EXPECTED THROUGH TUESDAY MORNING WITH
SOUTHERLY WINDS AROUND 10-15 KT AND SEAS 2 TO 3 FEET.
OUTLOOK...
TUESDAY AFTERNOON THROUGH TUESDAY NIGHT...A SMALL CRAFT ADVISORY
IS IN EFFECT FOR ALL MARINE ZONES AS SOUTH/SOUTHWEST WINDS
AROUND 20-25 KT AND SEAS OF 3 TO 5 FEET ARE EXPECTED.
WEDNESDAY THROUGH WEDNESDAY NIGHT...SCA CONDITIONS POSSIBLE
(40-50%) ESPECIALLY ON THE NORTHERN WATERS AS SEAS NEAR 5 FEET.
THURSDAY THROUGH FRIDAY...NO MARINE HEADLINES EXPECTED.
RIP CURRENTS...
FOR TODAY, AN 8 SECOND PERIOD AND BREAKING WAVES 2 FEET OR LESS
ALONG WITH SHORE PARALLEL WINDS UP TO 10 MPH WILL RESULT IN A
LOW RISK FOR RIP CURRENTS AT ALL BEACHES.
FOR TUESDAY, SOUTHERLY FLOW STRENGTHENS WITH WINDS INCREASING TO
AROUND 15-20 MPH WITH EITHER A SHORE PARALLEL OR ONSHORE FLOW
COMPONENT TO A SOUTHERLY WIND. MULTIPLE SWELL GROUPS AND
INCREASING BREAKING WAVES TO AROUND 2 TO 3 FEET AS WELL AS THE
COMING FULL MOON WILL ALSO ADD TO THE RIP CURRENT THREAT. AS A
RESULT, THERE IS A MODERATE RISK FOR 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...SMALL CRAFT ADVISORY FROM NOON TO 8 PM EDT TUESDAY FOR ANZ430-
431.
SMALL CRAFT ADVISORY FROM NOON TUESDAY TO 6 AM EDT WEDNESDAY
FOR ANZ450>455.
DISCUSSION...AKL/GORSE/HOEFLICH/PO
AVIATION...HOEFLICH/PO
MARINE...HOEFLICH
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