FXUS61 KPHI 091007 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 607 AM EDT Thu Jul 9 2026 .WHAT HAS CHANGED... A Flood Watch was issued for southeast Pennsylvania, northern Delaware, and portions of South Jersey. && .KEY MESSAGES... 1) Showers and thunderstorms develop this afternoon and evening with heavy rain and damaging wind gusts being the primary threat. A Flood Watch was issued for southeast PA, northern DE, and portions of South Jersey. 2) Additional rounds of showers and thunderstorms are expected on Friday which may linger into Saturday before drier conditions return on Sunday and into early next week. && .DISCUSSION... KEY MESSAGE 1...Showers and thunderstorms develop this afternoon and evening with heavy rain and damaging wind gusts being the primary threat. A Flood Watch was issued for southeast PA, northern DE, and portions of South Jersey. High pressure moves offshore this morning with return flow setting up behind the departing high, and southerly flow strengthening through the day. Dew points will climb into the low to mid 70s. Although temperatures will "only" be in the mid 80s or so, which is right around normal for this time of the year, the heat index will be in the upper 80s to low 90s. The main concern on will be the potential for showers and thunderstorms in the afternoon and evening. Low pressure approaches from the west and tracks towards the Mid- Atlantic by this evening A mid-level trough will move into the Northeast with some shortwave energy passing through the Delaware Valley, Delmarva, and southern New Jersey. SBCAPE values will be in excess of 1500 J/kg with PWATS from 2-2.5 inches, highest values from the Delaware Valley, including Philadelphia, south into Delmarva. 0-6 km shear will be from 25 to 30 kt. The two main threats from severe weather will be damaging wind gusts and heavy rain leading to localized flash flooding. Given the high PWATs and potential for some periods of training, have gone ahead and issued a Flood Watch for southeast PA, northern Delaware, and portions of South Jersey from noon until Midnight. Some areas within the Flood Watch also saw a good amount of rain lately and while we are still in a drought, the soils may be overwhelmed if some training were to occur over a certain area. Rainfall rates of 1-2" are likely witin the Flood Watch area. The Weather Prediction Center has a Slight Risk (2 out of 4) for Excessive Rainfall for southeast Pennsylvania, southern New Jersey, the eastern shores of Maryland, and Delaware, and a Marginal Risk (1 out of 4) for the southern Poconos and northern New Jersey. Ended up leaving the rest of Delmarva out of the Watch because of the more rural nature of the landscape and ability to take more rainfall than urban areas. The Storm Prediction Center has a Slight Risk for severe weather (2 out of 5) for the Delaware Valley south of Philadelphia, Delmarva, and southern New Jersey, and a Marginal Risk (1 out of 5) from around Philadelphia north to Allentown. No changes were made this morning to the Severe Weather Outlook. Although some showers and thunderstorms will fire up over far western portions of the forecast area from noon-2pm, the main timing will be from 3PM to 9 PM across the Delaware Valley, including Philadelphia, the eastern shores of Maryland, Delaware, and southern New Jersey. While showers and thunderstorms capable of damaging winds and localized flash flooding are likely for the northern zones as well, the highest impacts in terms of potential severe weather and flash flooding should be focused generally south of Philadelphia. A warm and muggy night with patchy fog developing Thursday night after showers and thunderstorms come to an end by midnight. Lows will be in the upper 60s to low 70s.KEY MESSAGE 2...Additional rounds of showers and thunderstorms are expected on Friday which may linger into Saturday before drier conditions return on Sunday and into early next week. On Friday, another round of showers and thunderstorms are expected to develop out ahead of a cold front moving southward into the area. Similarly to Thursday, moisture is anticipated to increase ahead of the front, where PWAT values are progged to be in excess of 1.8 inches. This supports that any given shower or storm will have the ability to produce heavy rainfall and flash flooding. As of now, the majority of our forecast area is highlighted in an MARGINAL risk (Level 1/4) for excessive rainfall. Held off on expanding the Flood Watch through Friday due to uncertainty in where the heaviest rainfall will set up today. In terms of the severe weather threat, ML CAPES are expected to reach at least 1000 J/kg with bulk shear values around 30 kt. Given better frontal forcing, there looks to be at least another opportunity for severe weather. As of now, SPC has our entire area highlighted in just a general thunder risk, however some of the MLP guidance indicate higher probabilities especially in terms of damaging winds. It is also worth noting that Friday will be quite sticky outside with highs in the upper 80s to low 90s with dew points in the low to mid 70s. This will result in heat indicies in the mid to upper 90s. We may get close to Heat Advisory criteria in some spots, but basis the current forecast, heat indicies are expected to remain just below advisory criteria. There remains a vast amount of uncertainty with how Saturday will pan out as guidance continues to struggle with how quickly the cold front clears the area. Some guidance slows the progression of the front, keeping more in the way of showers around on Saturday, whereas others show a faster progression, yielding mainly dry weather. As mentioned by the previous shift, opted to stay very close to NBM PoPs for this period, which keeps 10-30% PoPs north, with 30-60% PoPs mainly across south Jersey and the Delmarva. Temperatures will mainly be in the 80s. By Sunday and into early next week, guidance is showing an expansive upper level ridge setting up over the northern High Plains. This will yield dry weather and mainly clear skies across the Mid- Atlantic. Temperatures will be around normal for Sunday and Monday, but will swing back above normal by Tuesday and Wednesday. && .AVIATION /10Z THURSDAY THROUGH MONDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Today...MVFR conditions expected as some stratus moves through the area this morning. Expecting stratus to lift by the afternoon before some scattered showers and thunderstorms begin to develop in the afternoon and early evening. Coverage of showers/thunderstorms will be focused mainly from KRDG/KTTN on south. Have maintained TEMPO TSRA groups at all terminals except KABE as a period of thunderstorms are increasingly likely (60-70%) sometime between 18z-00z. Winds generally out of the south/southwest around 10 kt with higher gusts anticipated in any thunderstorms. Moderate confidence overall. Tonight...Primarily VFR as showers and thunderstorms move offshore. Cannot rule out some patchy fog, especially over areas that see rainfall. Winds out of the west/southwest around 5 kt or less. Low confidence. Outlook... Friday through Friday night...Primarily VFR but sub-VFR conditions likely (60-70%) in the afternoon and evening with another round of showers and thunderstorms. Saturday...Primarily VFR though cannot rule out a shower or thunderstorm developing. Saturday Night through Monday...VFR. No significant weather. && .MARINE... Sub-SCA conditions expected through Friday. Southwest winds around 10-15 kt expected with seas 2 to 3 feet. Showers and thunderstorms possible (40-60%) on the waters both Thursday afternoon and evening and Friday afternoon and evening. Outlook... Friday Night through Saturday Night...No marine headlines anticipated. Sunday through Sunday Night...SCA conditions possible (20-30%) as seas near 5 feet. Monday...No marine headlines expected. Rip Currents... For today, winds are more southerly, and the moderate swell also becomes more southeasterly. Southerly flow will be a bit stronger (winds 10 to 20 MPH) and wave heights a bit higher for the Ocean and Monmouth County beaches. This will result in a MODERATE risk for rip currents at these locales. Lower winds and wave heights for the southern Jersey Shore and Delaware Beaches will result in a LOW risk for rip currents. For Friday, winds turn southwesterly, and the swell weakens. Thus, this should result in a LOW risk of rip currents for all beaches. For specific beach forecasts, visit weather.gov/beach/phi && .PHI WATCHES/WARNINGS/ADVISORIES... PA...Flood Watch from noon EDT today through this evening for PAZ060-070-071-101>104-106. NJ...Flood Watch from noon EDT today through this evening for NJZ016>019. DE...Flood Watch from noon EDT today through this evening for DEZ001. MD...None. MARINE...None. && $$ DISCUSSION...DeSilva/Hoeflich AVIATION...Hoeflich MARINE...Hoeflich