308 FXUS61 KPHI 291713 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 113 PM EDT Mon Jun 29 2026 .WHAT HAS CHANGED... Aviation section updated for 18Z. && .KEY MESSAGES... 1. A warming trend in temperatures expected through Tuesday. A few showers or thunderstorms possible this afternoon and Tuesday. 2. Dangerous heat and humidity will build over the Northeast and Mid Atlantic beginning Wednesday through Saturday. All time record high temperatures could be challenged Thursday and Friday. 3. There is the potential for afternoon and evening thunderstorms starting on Friday and lasting into the holiday weekend. && .DISCUSSION... KEY MESSAGE 1...A warming trend in temperatures expected through Tuesday. A few showers or thunderstorms possible this afternoon and Tuesday. A strengthening ridge of high pressure to our west will result in a warming trend in temperatures through Tuesday. Highs will end up in the mid to upper 80s today, and closer to 90 degrees for some areas by Tuesday. With a lack of low level moisture return locally until late Tuesday, dewpoints are anticipated to mix out each afternoon. So although it'll be quite warm, humidity won't be too oppressive until the heat ramps up on Wednesday. Lows in the 60s. Strong insolation and lingering moisture will result in a slight chance of showers this afternoon, especially across the Poconos, but these should dwindle this evening. By Tuesday afternoon and evening, we could get some MCSs coming into our region out of the Great Lakes region amid the northwesterly flow aloft. Greatest chances of any thunderstorms will be focused mainly north of the Philly metro. Details on this activity remains to be seen, but will be something to monitor. It is possible convection remains mainly north of our area, and latest guidance trends have shifted northward compared to models earlier today. Damaging winds would be the main threat with any thunderstorms. KEY MESSAGE 2...Dangerous heat and humidity will build over the Northeast and Mid Atlantic beginning Wednesday through Saturday. All time record high temperatures could be challenged Thursday and Friday. Strong mid-level ridging will develop over the Great Lakes and Ohio Valley early this week. Ridging will then build eastward into the Northeast and Mid Atlantic by Wednesday and persist through into the holiday weekend. A west to southwest flow on Wednesday will shift more west to northwest by Friday. The ridge will finally start to break and retreat some starting Saturday into Sunday. High temperatures will climb into the mid and upper 90s on Wednesday, and then from 100 to 105 degrees on Thursday and Friday. With a south to southwest flow on Wednesday, dewpoints are less likely to mix out significantly in the afternoon. Resulting heat indices are forecast to range mainly from around 100-105 degrees. By Thursday and Friday, the shift to a more west or northwest flow will allow for better mixing out of dewpoints during the afternoon, and also a component of downsloping (adiabatic warming) from the Appalachians. This will support temperatures climbing above 100 degrees as dewpoints mix out into the mid 60s during the afternoon hours. Resulting forecast heat indices are mostly in the 105-110 degree range. This is indeed the type of synoptic pattern that could challenge all time record high temperatures in our region. See the Climate section below for more information on record temperatures. Temperatures will abate somewhat on Saturday as the ridge begins to break and retreat. However, high temperatures will still be in the mid 90s to near 100 degrees. The prevailing flow direction will dictate how much mixing out of dewpoints occur on Saturday. Currently, we have upper 60s to near 70 degree dewpoints, which results in 100-105 degree heat indices, locally as much as 110 degree for areas that don't mix out. Highs will remain in the low to mid 90s Sunday and Monday as well, with heat indices still in the mid 90s to low 100s. So we certainly could see heat related impacts continuing beyond Saturday despite a slight improvement in temperatures. The Extreme Heat Watch remains in effect for New Jersey, southeast Pennsylvania, the Delaware Valley including Philadelphia and northern Delaware, and the southern Poconos. Future shifts will likely expand the Watch to include the rest of Delmarva. The valid start time of the Extreme Heat Watch for far southern New Jersey and the barrier island was pushed back to now begin at noon Thursday, as we have been consistently forecasting heat indices below advisory criteria on Wednesday for those zones. The mid-level ridge will break and retrograde back towards the south and west on Saturday, and a mid-level trough will try to slide down into the Northeast. This pattern change will begin to favor slightly cooler temperatures and a break in the extreme heat by Sunday or Monday, as well as the potential for showers and thunderstorms next weekend (see Key Message 3 below). KEY MESSAGE 3...There is the potential for afternoon and evening thunderstorms starting on Friday and lasting into the holiday weekend. The mid-level ridge looks to break down and retrograde back to the south and west starting on Friday, and this will allow mid- level troughiness to develop over the Northeast. With several shortwaves riding over the top of the ridge and into the local area, this may touch off afternoon and evening showers and thunderstorms starting on Friday, but the better chances for convection arrive on Saturday and Sunday. Currently, PoPs are around 20-30% on Friday and 30-50% on Saturday and Sunday. While details of this activity won't become clear until later this week, it is important to point out that any holiday weekend festivities could be impacted by thunderstorms (in addition to the extreme heat). The environmental setup would be favorable for strong to severe thunderstorms, if any storms do develop. We'll continue to monitor this potential. && .AVIATION /18Z MONDAY THROUGH SATURDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Rest of Today...VFR. ENE winds increasing to near 5-10 kts from I-95 and southeast, then shifting SE to S. Very low risk of a stray shower. High confidence overall. Tonight...Very low risk of a stray shower early. Low chance of restrictions in fog overnight. Otherwise, VFR. Winds becoming light/variable. Low confidence in fog, high confidence otherwise. Tuesday...VFR. Winds shifting south-southwest and increasing with gusts up around 20 kts in the afternoon. High confidence. Outlook... Tuesday night through Friday...VFR. Low chance (20%) of a thunderstorm Tuesday and Friday, otherwise no significant weather. && .MARINE... No marine hazards are forecast through most of Tuesday. Northeast to east winds 5-10 kts, shifting southerly by Tuesday. Seas 1-3 feet, increasing to 2-4 feet Tuesday. Outlook... Tuesday night through Friday...Overall, no marine hazards are forecast. Cannot rule out a brief period of southerly 25+ kt gusts or seas approaching 5 feet late Tuesday and/or Wednesday afternoon, mainly north of Atlantic City. Rip Currents... For today, breaking waves in the surf zone will be around 2 feet or less with east to northeast winds around 10 mph and a southeast swell. As a result, there is a LOW risk of dangerous rip currents for both the Jersey Shore and Delaware Beaches. For Tuesday, conditions remain similar, with east to southeast winds around 10-15 mph and a southeast swell. Breaking waves in the surf zone will be around 1-2 feet as a result, and therefore, the LOW risk of dangerous rip currents for both the Jersey Shore and Delaware Beaches looks to continue. For specific beach forecasts, visit weather.gov/beach/phi && .CLIMATE... Record breaking heat is forecast from Wednesday through Saturday. Temperature records for our climate sites are listed below: All Time Record High Temperatures Site Record / Date Allentown (ABE) 105 / July 3, 1966 AC Airport (ACY) 106 / June 28, 1969 AC Marina (55N) 104 / August 7, 1918 Georgetown (GED) 104 / July 22 & 23, 2011 Mount Pocono (MPO) 103 / July 3, 1911 Philadelphia (PHL) 106 / August 7, 1918 Reading (RDG) 106 / July 22, 2011 Trenton (TTN) 106 / July 9, 1936 & July 22, 2011 Wilmington (ILG) 107 / August 7, 1918 All Time Record Warmest Low Temperatures Site Record / Date Allentown (ABE) 79 / July 15, 1995 AC Airport (ACY) 84 / July 23, 2011 AC Marina (55N) 82 / July 21, 2019 Georgetown (GED) 84 / July 23, 2011 Mount Pocono (MPO) 76 / July 12, 1952 Philadelphia (PHL) 83 / July 24, 2010 & July 23, 2011 Reading (RDG) 81 / August 7, 1918 Trenton (TTN) 84 / August 11, 1895 Wilmington (ILG) 84 / August 7, 1918 Record Number of Consecutive 100+ Degree Days Site Record / Date Allentown (ABE) 3 days / July 9-11, 1936 & July 2-4, 1966 AC Airport (ACY) 3 days / July 2-4, 1966 & July 22-24, 2011 AC Marina (55N) 1 day / Occurred multiple times Georgetown (GED) 2 days / Most recent June 24-25, 2025 Mount Pocono (MPO) 1 day / July 3, 1911 Philadelphia (PHL) 3 days / July 2-4, 1966 & July 8-10, 1993 Reading (RDG) 3 days / Most recent July 21-23, 2011 Trenton (TTN) 3 days / Most recent July 21-23, 2011 Wilmington (ILG) 3 days / Most recent July 9-11, 1936 Record High Temperatures July 1 Site Record / Year Allentown (ABE) 98 / 2018 AC Airport (ACY) 99 / 1968 AC Marina (55N) 98 / 1968 Georgetown (GED) 99 / 2012 Mount Pocono (MPO) 88 / 1963, 1964, 1968, & 2018 Philadelphia (PHL) 102 / 1901 Reading (RDG) 101 / 1901 Trenton (TTN) 98 / 1898, 1901, & 1945 Wilmington (ILG) 97 / 1931 & 1963 Record Warmest Low Temperatures July 1 Site Record / Year Allentown (ABE) 74 / 1930 AC Airport (ACY) 77 / 1945 AC Marina (55N) 79 / 1945 Georgetown (GED) 76 / 1945 Mount Pocono (MPO) 67 / 1946, 1971, 2013, 2017, 2025 Philadelphia (PHL) 82 / 1901 Reading (RDG) 76 / 1968 Trenton (TTN) 77 / 1945 Wilmington (ILG) 75 / 2013 Record High Temperatures July 2 Site Record / Year Allentown (ABE) 102 / 1966 AC Airport (ACY) 100 / 1966 AC Marina (55N) 97 / 1968 Georgetown (GED) 99 / 1953 Mount Pocono (MPO) 93 / 1911 Philadelphia (PHL) 103 / 1901 Reading (RDG) 102 / 1966 Trenton (TTN) 100 / 1901 Wilmington (ILG) 98 / 1941 & 1966 Record Warmest Low Temperatures July 2 Site Record / Year Allentown (ABE) 75 / 2013 AC Airport (ACY) 79 / 2002 AC Marina (55N) 76 / 2012 Georgetown (GED) 77 / 1959 Mount Pocono (MPO) 70 / 1903 Philadelphia (PHL) 82 / 1901 Reading (RDG) 79 / 1901 Trenton (TTN) 79 / 1901 Wilmington (ILG) 75 / 1941 & 2014 Record High Temperatures July 3 Site Record / Year Allentown (ABE) 105 / 1966 AC Airport (ACY) 104 / 1966 AC Marina (55N) 99 / 1919 Georgetown (GED) 101 / 1954 Mount Pocono (MPO) 103 / 1911 Philadelphia (PHL) 104 / 1966 Reading (RDG) 103 / 1898 & 1966 Trenton (TTN) 102 / 1966 Wilmington (ILG) 102 / 1966 Record Warmest Low Temperatures July 3 Site Record / Year Allentown (ABE) 75 / 2018 AC Airport (ACY) 78 / 2018 AC Marina (55N) 76 / 1983, 2002, & 2018 Georgetown (GED) 79 / 1953 Mount Pocono (MPO) 69 / 2013 Philadelphia (PHL) 77 / 1876, 1901, &2002 Reading (RDG) 76 / 2018 Trenton (TTN) 76 / 1901 & 1966 Wilmington (ILG) 76 / 2002 Record High Temperatures July 4 Site Record / Year Allentown (ABE) 102 / 1949 AC Airport (ACY) 102 / 1966 AC Marina (55N) 99 / 1966 Georgetown (GED) 100 / 1966 Mount Pocono (MPO) 99 / 1911 Philadelphia (PHL) 103 / 1966 Reading (RDG) 100 / 1911 & 1966 Trenton (TTN) 99 / 1919, 1999, & 2010 Wilmington (ILG) 102 / 1966 Record Warmest Low Temperatures July 4 Site Record / Year Allentown (ABE) 75 / 1999 AC Airport (ACY) 75 / 1974, 1983, 1999, & 2002 AC Marina (55N) 79 / 2002 Georgetown (GED) 75 / 1999 & 2012 Mount Pocono (MPO) 70 / 2002 & 2013 Philadelphia (PHL) 79 / 1919 Reading (RDG) 78 / 1966 Trenton (TTN) 78 / 1966 Wilmington (ILG) 76 / 1999 && .PHI WATCHES/WARNINGS/ADVISORIES... PA...Extreme Heat Watch from Wednesday afternoon through Saturday evening for PAZ054-055-060>062-070-071-101>106. NJ...Extreme Heat Watch from Wednesday afternoon through Saturday evening for NJZ001-007>010-012>020-027. Air Quality Alert until 11 PM EDT this evening for NJZ001- 007>010-012>015. Extreme Heat Watch from Thursday afternoon through Saturday evening for NJZ021>026. DE...Extreme Heat Watch from Wednesday afternoon through Saturday evening for DEZ001. MD...None. MARINE...None. && $$ DISCUSSION...MPS/Staarmann AVIATION...MPS/RCM/Staarmann MARINE...AKL/MPS/Staarmann