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Area Forecast Discussion
Issued by NWS Mt. Holly, NJ
Issued by NWS Mt. Holly, NJ
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143 FXUS61 KPHI 151728 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 128 PM EDT Mon Jul 15 2024 .SYNOPSIS... Bermuda high pressure remains offshore through the middle of the week. A thermal trough looks to develop east of the Appalachians Monday and Tuesday. Excessive heat and humidity are expected through Wednesday along with daily thunderstorm chances. A cold front will cross the region Wednesday night into Thursday, stalling out and lingering near or just south of the area through the end of the week. && .NEAR TERM /THROUGH TONIGHT/... Bermuda high pressure will usher an increasingly hot and humid airmass into the region today. High temperatures today will soar into the mid and upper 90s for most of the area, except for the mountains and along the immediate shorelines, where highs will be in the 80s. Surface dew points start out in the low to mid 70s. West winds will increase to 10 to 15 mph with occasional gusts up to 20 mph, and along with those mostly sunny skies, there should be enough mixing in the afternoon for those dew points to drop back to around 70, and possibly even in the upper 60s, during peak heating of the day. This will still yield max heat index values of 100 to 105. No changes will be made to the Heat Advisories and Excessive Heat Warnings that were in effect for today. There is another threat for severe weather late this afternoon and into this evening. An MCS currently over the Great Lakes and Ohio Valley will track east today and will move into western New York and western Pennsylvania by this afternoon. With some troughiness and shortwave energy approaching from the west, this will trigger another round of late day showers and thunderstorms. For most of the area, PoPs will be capped at chance, but will introduce likely PoPs for the southern Poconos towards this evening. With the heat and humidity, SB CAPE values will be upwards of 1500 to 2000 J/kg. BUFKIT soundings indicating an inverted-V pattern along with fairly steep low level lapse rates. Also, PWATs will be almost 2 inches. Damaging wind gusts, frequent cloud to ground lightning strikes, and heavy rain will once again be the threats. Showers and thunderstorms taper off after sunset. Another warm and muggy night on tap with lows in the 70s. Patchy fog may develop once again along the coasts and in areas where heavy rain develops later today. && .SHORT TERM /TUESDAY THROUGH TUESDAY NIGHT/... The excessively hot and humid stretch continues through Tuesday and Tuesday night. For Tuesday, temperatures increase even more along with lower chances for convection during the daytime period. Tuesday is still expected to be the hottest and most oppressive of this stretch, with highs largely in the upper 90s to near 100, most likely in the I-95 urban corridor. Dew points remaining in the lower 70s will support peak heat indices of 105-110 degrees across much of the area. Lows Tuesday night will likely be the warmest of this hot stretch, with lows in the mid to upper 70s in many areas, and near 80 degrees in the urban centers. Given the latest forecast is largely unchanged, we have maintained the current Excessive Heat Warning and Heat Advisories across the region for Tuesday. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... Summary...Excessive heat Wednesday begins to diminish as a cold front and associated showers and thunderstorms move toward the region late Wednesday, then temperatures should be closer to average Thursday through Sunday with lowered humidity. Synoptic Overview...An upper-level trough is forecast to pivot into and across the Northeast and Mid-Atlantic regions Thursday into Friday. The western Atlantic ridge may try to expand eastward again into the Mid-Atlantic Saturday, however an upper- level trough is forecast to remain from eastern Canada down across the Great Lakes and into the Mid-Mississippi Valley. This may be enough to keep the main part of the ridge at bay along with the associated hotter temperatures. At the surface, a cold front arrives Wednesday night and gradually shifts offshore during Thursday. High pressure should then extend eastward into our area Friday into Saturday. For Wednesday and Thursday...As an upper-level trough arrives, a cold front will approach during the day Wednesday before crossing our region Wednesday night and Thursday. A pre-frontal trough may also develop on the leeward side of the mountains. This combined with increasing forcing for ascent and greater effective shear should result in showers and thunderstorms developing and becoming more widespread with time, especially by late afternoon and evening. The convective organization may be more tied to the pre-frontal trough as it shifts eastward later Wednesday, and given ample instability and enough shear some thunderstorms could be strong to severe Wednesday afternoon and evening. The details however remain a bit unclear. The highest PoPs are included Wednesday afternoon and evening, however the PoPs remain at least in the chance range Thursday for most of the region as the front may be slow to clear our area. High temperatures are forecast to be well into the 90s yet again, with resulting heat indices near 100-107 or so across much of the area (especially along and south of I-78). Thus, the Excessive Heat Watch remains in effect for Wednesday. The arrival of convection and also the cold front will knock down the excessive heat, and therefore Thursday is expected to be noticeably cooler and drier than Wednesday. For Friday through Sunday...The main part of the upper-level trough should be lifting up across the Canadian Maritimes later Friday, however this trough (weaker form) may extend southwestward across the Great Lakes and into the Mid- Mississippi Valley. Pending that the front clears our entire area by Friday and drier air advects in, precipitation chances then drop off during this time frame. Surface high pressure centered near the Midwest should then extend eastward with time and into our area. This should promote a more light northerly flow, although may result in a sea breeze both days, and therefore temperatures much closer to average and also lowered humidity. By the back half of the weekend though, the high may lift far enough north that chances for showers and thunderstorms may return. && .AVIATION /18Z MONDAY THROUGH SATURDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Rest of this afternoon (through 00Z)...Prevailing VFR. SHRA/TSRA possible after 21Z and could result in brief restrictions and strong wind gusts should a storm pass over a given terminal. Terminals that could be affected are KRDG/KABE/KTTN where VCTS was added. Lower confidence for KPNE/PHL/KILG. SW winds 5 to 10 kt, becoming 10 to 15 kt with gusts up to 20 kt this afternoon. Moderate confidence overall, low confidence in convection coverage and timing. Tonight...Any lingering SHRA/TSRA will taper off by 03Z or so. Primarily VFR, but patchy fog possible again late at night that could result in sub-VFR VSBYs. Light S winds. Moderate confidence. Outlook... Tuesday through Tuesday night...Generally prevailing VFR. A 20-30% chance of showers or thunderstorms, mainly northwest of I-95. Wednesday and Thursday...Showers and thunderstorms likely, especially Wednesday afternoon and evening, likely leading to sub-VFR conditions at times. Friday...VFR conditions with no significant weather expected. && .MARINE... Conditions remain below Small Craft Advisory criteria. A prevailing SW flow of 10 to 15 kt will persist for today and tonight with gusts up to 20 kt or so this afternoon. Seas will average 3 to 4 feet. Afternoon and evening thunderstorms may result in VSBY restrictions in heavy rain, wind gusts in excess of 34 kt, and frequent lightning strikes. Areas of fog on the waters will also result in VSBY restrictions today and tonight, especially for waters very close to the coast. Outlook... Tuesday through Tuesday night...The conditions should be below Small Craft Advisory criteria. Some fog possible at times. Wednesday and Thursday...A Small Craft Advisory may be needed, especially Wednesday. Showers and thunderstorms develop Wednesday afternoon with some continuing into Thursday. Areas of fog possible. Friday...Conditions are expected to be below SCA criteria. Rip Currents... For Today and Tuesday, south to southwest flow will average 10 to 15 mph. Gusts up to 20 mph are possible during the daytime hours. Wave heights will average 1 to 3 feet and a 5 to 7 second period. Therefore, there is a MODERATE RISK for the development of dangerous and life threatening rip currents for the Jersey Shore in Ocean, Atlantic, and Cape May counties, and a LOW risk for the Jersey Shore in Monmouth county and Delaware Beaches. Late day showers and thunderstorms are possible, mainly for the Jersey Shore in Monmouth and Ocean counties. Some areas of fog at times will cause reduced visibility along the shoreline. For specific beach forecasts, visit weather.gov/beach/phi && .CLIMATE... Near record breaking temperatures are forecast from Monday through Wednesday. Records for our climate sites are listed below: Record High Temperatures July 15 Site Record/Year Allentown (ABE) 98/1995 AC Airport (ACY) 100/1995 AC Marina (55N) 99/1995 Georgetown (GED) 96/1993 Mount Pocono (MPO) 92/1954 Philadelphia (PHL) 103/1995 Reading (RDG) 96/1995 Trenton (TTN) 101/1995 Wilmington (ILG) 99/1995 & 1997 Record Warmest Low Temperatures July 15 Site Record/Year Allentown (ABE) 79/1995 AC Airport (ACY) 78/1995 AC Marina (55N) 80/1995 Georgetown (GED) 75/2012 & 2016 Mount Pocono (MPO) 69/2013 Philadelphia (PHL) 81/1995 Reading (RDG) 79/1995 Trenton (TTN) 78/1995 Wilmington (ILG) 78/1995 Record High Temperatures July 16 Site Record/Year Allentown (ABE) 101/1988 AC Airport (ACY) 100/1983 AC Marina (55N) 100/1983 Georgetown (GED) 97/1953 & 1992 Mount Pocono (MPO) 93/1988 Philadelphia (PHL) 102/1988 Reading (RDG) 100/1900 Trenton (TTN) 102/1988 Wilmington (ILG) 100/1983 Record Warmest Temperatures July 16 Site Record/Year Allentown (ABE) 76/1983 AC Airport (ACY) 77/1983 AC Marina (55N) 80/2013 Georgetown (GED) 80/1955 Mount Pocono (MPO) 70/1955 Philadelphia (PHL) 80/2013 Reading (RDG) 78/1955 Trenton (TTN) 78/1983 Wilmington (ILG) 77/2013 Record High Temperatures July 17 Site Record/Year Allentown (ABE) 99/1999 AC Airport (ACY) 99/2012 AC Marina (55N) 95/1937 Georgetown (GED) 100/2019 Mount Pocono (MPO) 91/1999 Philadelphia (PHL) 102/1988 Reading (RDG) 102/1988 Trenton (TTN) 100/1988 Wilmington (ILG) 100/1988 && .PHI WATCHES/WARNINGS/ADVISORIES... PA...Excessive Heat Warning until 6 AM EDT Wednesday for PAZ060>062- 070-071-101>106. Air Quality Alert until 11 PM EDT this evening for PAZ070-071- 101>106. Excessive Heat Watch from Wednesday morning through Wednesday evening for PAZ060>062-070-071-101>106. Heat Advisory until 8 PM EDT Tuesday for PAZ054-055. NJ...Excessive Heat Warning until 6 AM EDT Wednesday for NJZ009-010- 012-013-015-017>020-027. Air Quality Alert until 11 PM EDT this evening for NJZ008>010- 012>027. Excessive Heat Watch from Wednesday morning through Wednesday evening for NJZ001-007>010-012-013-015>022-027. Heat Advisory until 6 AM EDT Wednesday for NJZ001-007-008-014- 016-021>023. DE...Excessive Heat Warning until 6 AM EDT Wednesday for DEZ001. Air Quality Alert until 11 PM EDT this evening for DEZ001>004. Excessive Heat Watch from Wednesday morning through Wednesday evening for DEZ001>004. Heat Advisory until 6 AM EDT Wednesday for DEZ002>004. MD...Excessive Heat Warning until 6 AM EDT Wednesday for MDZ012-015- 019-020. Air Quality Alert until 11 PM EDT this evening for MDZ012-015- 019-020. Excessive Heat Watch from Wednesday morning through Wednesday evening for MDZ012-015-019-020. MARINE...None. && $$ SYNOPSIS...Staarmann NEAR TERM...AKL/Johnson/MJL/MPS SHORT TERM...AKL/Gorse/Staarmann LONG TERM...AKL/Gorse/Staarmann AVIATION...AKL/Johnson/MJL/MPS/Staarmann MARINE...AKL/Hoeflich/Johnson/MPS/Staarmann CLIMATE...