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Area Forecast Discussion
Issued by NWS Mt. Holly, NJ
Issued by NWS Mt. Holly, NJ
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783 FXUS61 KPHI 150540 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 140 AM EDT Thu Aug 15 2024 .SYNOPSIS... High pressure over the area moves offshore late Friday. A cold front will slowly work its way across the region over the region until departing on Monday. Meanwhile, Hurricane Ernesto will remain well east of the coasts through the weekend. High pressure builds in from the west starting on Tuesday. && .NEAR TERM /THROUGH TODAY/... Broad and weak surface high pressure will continue to influence our region through Thursday as it migrates eastward. Tranquil weather conditions will continue through the term. Some upper-level shortwave energy is posed to pass through early this morning. The isolated convection that developed earlier has dissipated, and no additional convection is expected. A tranquil night is on tap. Mostly clear skies with lows mainly in the low to mid 60s (upper 50s at higher elevations) expected. Light NNW winds and/or winds going light and variable for most locations. Some very light patchy ground or valley fog may occur. For Thursday, high temperatures in mid 80s for most locations; highs in the mid to upper 70s for the higher elevations and coasts. Winds 5 kts or less, favoring a N to NW direction, or remaining light and variable through much of the period. A sea- breeze will likely develop, given the weak overall flow, and could penetrate fairly inland by the evening. Some upper-level shortwave energy could again pass through during the afternoon and evening; a few isolated pop-up showers should not be ruled during these time frames for areas, mainly north of the Philly metro and along the sea breeze in interior southern New Jersey. && .SHORT TERM /TONIGHT THROUGH SATURDAY/... High pressure will be over the Northeast and will extend down into the Mid-Atlantic Thursday night before lifting to the northeast Friday night. With the high still influencing the local area on Friday, this results in a slower approach of the cold front. Tranquil conditions Thursday night, and then clouds increase throughout the day Friday. Temperatures will warm to several degrees above normal with lows in the 60s Thursday night and then highs in the mid to upper 80s with cooler temperatures at the coasts and in the mountains on Friday. With the slower approach of the cold front, showers really will not get going in the western zones until after midnight Friday night, and even then, PoPs are capped at chance. Scattered showers and thunderstorms continue into Saturday, but the activity really gets going by Saturday afternoon as shortwave energy moves in from the west. Although temperatures will be a few degrees shy of normal, dew points will rise into the upper 60s and low 70s, so it will feel humid and muggy. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... What is currently Hurricane Ernesto will stay well east of the Jersey Shore this weekend. However, large swells will impact the coasts this weekend with elevated surf and dangerous rip currents. Low pressure over the Great Lakes will have a trough extending down through the Ohio and Tennessee Valleys and into the Mid- Atlantic. A cold front will extend down from this system and will slowly work its way east over the weekend. Shortwave energy exiting from the base of the trough will spin off a secondary low near the Delmarva Peninsula Saturday night. With southerly flow ahead of this system picking up moisture from the Atlantic Ocean as well as Tropical Storm Ernesto which should be several hundred miles east of Atlantic City, dew points will be up in the low 70s, resulting in PWATs up around 2 inches. This will result in periods of heavy rain Saturday night, which could lead to localized flooding. This secondary low departs by Sunday morning, and then there may be a lull in the precip until Sunday afternoon. Low pressure moves into central New York on Sunday, dragging the cold front closer to the region. Another round of showers and thunderstorms will develop Sunday afternoon and evening. Cold front then works its way through the region Sunday night, and should be cleared by Monday morning. The trough, however, will lag behind the cold front, and a secondary cold front will develop with this trough. Another round of showers and thunderstorms will develop Monday afternoon with the passage of this secondary front, but PoPs for now will be capped mostly at chance with a small area of likely PoPs in the southern Poconos. The trough, however, may get hung up over the East Coast. While dew points will be coming down on Monday behind the initial cold front, this secondary front will not exactly moisture-starved with dew points in the 60s. By this point, Ernesto will be long gone. With that trough over the area, unsettled weather may continue into Tuesday and maybe even Wednesday. && .AVIATION /06Z THURSDAY THROUGH MONDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Early this morning...VFR/SKC. Winds 5 kts or less, favoring a N to NW direction. Some sites (e.g., KMIV/KACY) will see winds go light and variable for the period. High confidence. Thursday...VFR. Winds 5 kts or less, favoring a N to NW direction, or remaining light and variable through much of the day. A sea- breeze will likely once again develop causing a SE/SSE wind shift for at least KMIV/KACY. Sea-breeze my end up penetrating further inland toward I-95 given the prevailing background flow. High confidence overall, low confidence in sea- breeze timing and distance. Outlook... Thursday night through Friday...VFR. Friday night through Sunday night...Sub-VFR conditions from time to time in SHRA, which may be heavy at times Saturday night and Sunday night. Scattered TSRA as well. Monday...Generally VFR. Scattered afternoon SHRA/TSRA possible that may result in brief sub-VFR conditions. && .MARINE... No marine headlines are anticipated through Thursday. Winds 5-10 kts. Seas 1-2 feet. Fair weather. Outlook... Thursday night through Friday...Sub-SCA conditions. Friday night through Sunday...SCA conditions expected, mainly for elevated seas due to larger swells from Ernesto. Monday...SCA conditions may continue as seas will be slow to subside. Rip Currents... Thursday...Light north winds will become south 5 to 10 mph in the afternoon as sea breezes develop. Breaking waves will be around 1 foot with a 9 second period. Therefore, there is a LOW risk for the development of dangerous and life threatening rip currents at the Jersey Shore and at Delaware Beaches. On Friday, south winds will increase to 10 to 15 mph with occasional gusts up to 20 mph in the afternoon. Breaking waves will average 2 to 3 feet. Given the flow will be parallel to the Jersey Shore, there is a MODERATE risk for the development of dangerous and life threatening rip currents for the Jersey Shore and a LOW risk for the development of dangerous rip currents for Delaware Beaches. Over the weekend, Hurricane Ernesto will pass well east of the mainland. Large swells from this storm will result in elevated seas that should result in dangerous and life threatening rip currents at the Jersey Shore and at Delaware Beaches for at least Saturday and Sunday. For specific beach forecasts, visit weather.gov/beach/phi && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...None. && $$ SYNOPSIS...MPS NEAR TERM...AKL/Staarmann/Wunderlin SHORT TERM...MPS LONG TERM...MPS AVIATION...AKL/MPS/Staarmann/Wunderlin MARINE...MPS/Wunderlin