367 FXUS61 KPHI 052235 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 635 PM EDT Tue Sep 5 2023 .SYNOPSIS... High pressure continues to dominate through mid-week with increasing heat and humidity. Precipitation chances return Thursday as a surface trough develops across the area. A cold front passes late in the week and precipitation chances continue into the weekend as low pressure develops along the front. && .NEAR TERM /THROUGH WEDNESDAY/... Warm and humid conditons on tap for tonight. Lows outside of the higher elevations likely won't drop below 70 degrees. With dew points hovering around that range as well, a sticky night lies ahead. Winds will decouple quickly after sunset and go light and variable to calm with clear skies, and some localized patchy fog is possible akin to this morning, but not expecting anything widespread. Wednesday will largely be a rinse and repeat of Tuesday. Thickness values and 850 mb temperatures of 18-20C will be very similar to that of Tuesday if not just a smidge higher on both fronts, and the upper ridge axis will extend overhead, so with little change in the airmass will likely see another day with high temperatures in the mid 90s, and if dew points follow a similar trend to Tuesday, likely will see values in the upper 60s/low 70s again in the afternoon, resulting in heat index values again exceeding 100F. The heat advisory remains in effect through Wednesday and has been expanded to include Western Chester, Montgomery, Berks, and Southeastern Burlington Counties. Some record highs again are in play, see climate section. Aside from some scattered diurnal cumulus, another dry day ahead with plenty of sunshine and a light northwesterly breeze. && .SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/... The upper ridge will continue to weaken Wed night/Thu while moving offshore. Troughing over the Great Lakes will slowly intensify and move east later Thu and into Fri. This will bring a few shortwaves and a slow moving front to the area by later Fri. We'll keep a dry fcst Wed night and bring some chance pops for showers/tstms for Thu. There has been a trend towards slowing the front, so lower pops for Thu remain a possibility as the time approaches. Scattered showers/tstms will arrive later Thu and continue into Friday as the system approaches. Pops will be higher across the western/northern counties while the shore areas and Delmarva may see more isolated convection these periods. Hot temperatures will continue Thu with widespread low/mid 90s and mid 80s for the southern Poconos. More records could fall Thu (except for PHL - 102 !). On Friday, the increased clouds and showers will keep slightly cooler temps for the area, mostly upper 80s/low 90s, but still uncomfortably humid. && .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/... An upper air pattern will continue to transition to an eastern U.S. trough and ridging offshore during the long term. This will bring noticeably different weather this weekend (compared to last) with more seasonable temperatures but higher chances for showers. The southerly flow aloft will bring deeper moisture up from the south. This along with a slow moving low pressure system and trough arriving from the Ohio Valley will bring better chances for showers/tstms at the start of the long term with likely/high chance pops for Fri night and Sat. The system may depart Sunday but we'll keep the pops at chance levels for now in case the system slows further. Dry weather is currently foreseen for early next week as the upper trough weakens (temporarily) and surface high pressure arrives from the west. Temperatures will still be a few degrees above normal Sat with highs in the low/mid 80s for the area. Readings will tick down a few degrees Sunday and by Monday, highs will be normal with upper 70s for the north and low 80s for Delmarva and metro Philadelphia areas. Humidity levels will be moderate to high Sat/Sun but then become drier for Monday. && .AVIATION /00Z WEDNESDAY THROUGH SUNDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Tonight...VFR overall. Some fog may develop prior to daybreak that could result in MVFR VSBYs. Will TEMPO BR from 10Z to 12Z at a few of the outlying terminals. LGT/VRB to nearly calm winds. High confidence. Wednesday...VFR with some scattered afternoon cumulus. Northwesterly wind 5-10 knots. Afternoon sea breezes at KACY/KMIV likely. High confidence. Outlook... Wed night/Thursday... VFR expected. Increasing clouds Thu. medium/high confid. Thursday night/Friday... Lower conditions possible with a chance of showers/tstms arriving. medium confid. Fri night thru Sat night... MVFR/IFR probable at times with low clouds and occasional showers/tstms. medium confid. Sunday... Lower CIGS early then VFR expected. low/medium confid. && .MARINE... No marine headlines expected. Fair weather. South to southwest wind 5-10 knots. Seas 2-4 feet. Outlook... Wed night/Thu/Thu night... sub-SCA conditions. Fair. Fri thru Sat night... sub-SCA but gusts around 20 kts at times. Scattered showers tstms with localized higher winds and seas. Sunday... sub-SCA. Scattered showers. Rip currents... For today, still expecting a fairly strong 4ft 11-12 second easterly swell as a result of a number of strong post-tropical lows in the North Atlantic and continue to cause hazardous rip currents. Wave heights will be around 2 to 4 feet. As a result, a HIGH risk for the development of dangerous rip currents for the Delaware and New Jersey beaches will continue. For Wednesday, the long period onshore swell diminishes slightly to around 3-4 feet around 10-11 seconds. Breaking wave heights are also expected to fall to 3 feet or lower. Flow will be mainly parallel to the coastline. NWPS Rip Probabilities are significantly lower on Wednesday compared to the previous several days. As a result, there will be a MODERATE risk for the development of dangerous rip currents at the Jersey Shore and Delaware Beaches. && .CLIMATE... Near record breaking heat is forecast through Thursday. Records for our climate sites are listed below: Record High Temperatures Tue Sept 5 Wed Sept 6 Thu Sept 7 Site Record/Year Record/Year Record/Year Allentown (ABE) 94/2018 96/1983 91/2016 AC Airport (ACY) 93/1985 98/1983 94/1983 AC Marina (55N) 94/1880 92/1985 92/1983 Georgetown (GED) 93/2018 93/2018 94/1983 Mount Pocono (MPO) 85/2018 88/2018 85/2015 Philadelphia (PHL) 95/2018 95/2018 102/1881 Reading (RDG) 93/2018 95/1943 97/1983 Trenton (TTN) 95/1985 99/1983 94/1983 Wilmington (ILG) 93/2018 98/1983 95/1983 && .PHI WATCHES/WARNINGS/ADVISORIES... PA...Heat Advisory until 8 PM EDT Wednesday for PAZ070-071-102-104- 106. Heat Advisory from 8 AM to 8 PM EDT Wednesday for PAZ060-101- 103. NJ...Heat Advisory until 8 PM EDT Wednesday for NJZ008>010-012-013- 015>019. High Risk for Rip Currents until 9 PM EDT this evening for NJZ014- 024>026. Heat Advisory from 8 AM to 8 PM EDT Wednesday for NJZ027. DE...Heat Advisory until 8 PM EDT Wednesday for DEZ001. High Risk for Rip Currents until 9 PM EDT this evening for DEZ004. MD...None. MARINE...None. && $$ SYNOPSIS...Brudy/MJL/RCM NEAR TERM...Brudy/MPS SHORT TERM...OHara LONG TERM...OHara AVIATION...Brudy/MPS/OHara MARINE...Brudy/OHara CLIMATE...