Area Forecast Discussion
Issued by NWS Mt. Holly, NJ
Issued by NWS Mt. Holly, NJ
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098 FXUS61 KPHI 270159 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 959 PM EDT Thu Sep 26 2024 .SYNOPSIS... A cold front will stall over the southern half of the area tonight, as moisture from Tropical Cyclone Helene moves in. An unsettled pattern will continue for the weekend and into next week as an upper level low meanders off to the southwest. A pattern change potentially comes by the middle of next week as a sweeping cold front approaches. && .NEAR TERM /THROUGH FRIDAY NIGHT/... Overnight, low pressure with its associated upper trough moves from Quebec towards the Canadian Maritimes dragging a cold front southward into the area. This could result in some additional scattered showers and storms, mainly over eastern PA into central and northern NJ. In fact the front is expected to slow and stall overnight as it reaches southern NJ and the Delmarva. It will be another warm night for this time of year with lows mostly in the mid to upper 60s except some upper 50s over the southern Poconos and NW NJ. The warm and moist air mass settling over the region overnight is now posing an increasing risk of widespread dense fog late tonight. Starting to get some low visibilities already as of near 10 PM. Have increased fog potential in grids for the time being. Dense fog advisories may be required by early Friday morning. Helene is forecast to be over northern Georgia on Friday morning, becoming absorbed into a closed upper level low over the southeast US. This system is expected to be quite expansive, and some moisture from the edge of Helene is anticipated to move in Friday into Friday night. A stalled boundary over the Delmarva peninsula will be the focus for precipitation and currently where the highest PoPs are for Friday afternoon/evening (around 60-70%). This said, rainfall amounts are not overly impressive (only up to a half inch of rain at most). Showers become more scattered to isolated the further north you get from Philadelphia, and some areas of far northern New Jersey could see little to no rainfall at all. Along and south of the front, temperatures will be in the mid to upper 70s, with upper 60s/low 70s north of the front. Overnight lows on Friday night will be in the upper 50s to low 60s north and west with upper 60s to around 70 south and east. && .SHORT TERM /SATURDAY THROUGH SUNDAY/... Onshore flow looks to continue Saturday, bringing a cool and moist airmass. The remnants of Helene will retrograde westward, with the expansive upper level low positioned over Kentucky/Tennessee. With the maritime airmass in place, and the closed low off to the southwest, a few showers could develop, mainly in New Jersey and eastern Pennsylvania. Will not be a washout by any means, but more of a cloudy day with some showers around, similar to what we have seen the past few days. With a stalled boundary still bisecting the region, temperatures will be in the upper 60s/low 70s north of Philadelphia, and upper 70s/low 80s from Philly on south. The upper level low that will eventually absorb Hurricane Helene will be positioned somewhere over the Ohio River or Tennessee River Valley on Sunday with the region positioned on the northeast quadrant of the closed low. This looks to bring some unsettled weather, but no day will be a washout. We look to be in for more days of clouds with periods of on and off showers until the upper level low moves offshore or transitions to more of an open wave. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... The aforementioned upper low will transition into an open wave sometime Monday or Tuesday, though we will not kick the clouds/showers until midweek, with guidance hinting at a cold front coming through and a pattern change (finally). It certainly will be feeling like fall with cloudy and cool conditions expected for the end of the weekend and into next week. Temperatures will be a few degrees below normal for late September/early October, with upper 60s/low 70s for highs. Overnight lows may actually end up a few degrees above normal with limited diurnal ranges continuing with an abundance of cloud cover in place. && .AVIATION /02Z FRIDAY THROUGH TUESDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Tonight...Cigs lowering once again with IFR possible by late evening, becoming likely by the predawn hours. Guidance is tanking vsby and cigs to VLIFR late tonight with widespread dense fog in some areas so have leaned TAFs in that general direction. Winds backing to E/NE around 5 knots as a cold front pushes south into the area. Low confidence. Friday...IFR, possibly VLIFR cigs/vsby to start the day with gradual improvement possible to MVFR possible by the afternoon. Showers possible, mainly across the southern tier. Low confidence Outlook... Friday Night...MVFR/IFR conditions likely (80- 90%) with periods of rain moving through. Saturday through Saturday Night...Sub-VFR conditions expected at times, potentially as low as IFR, though stretches of VFR possible, mainly from KPHL on south. Sunday through Tuesday...sub-VFR conditions possible with 20-40% chance of showers and low clouds hanging around in between periods of rain. && .MARINE... Small Craft Advisory for our waters north of Cape May remains in effect until 2 AM early Friday morning. This is mainly due to 4-6 ft seas. Southerly winds will generally average 10 to 20 kts. Sub-SCA conditions Friday with easterly winds less than 10 kts in the morning, becoming 10 to 20 kts in the afternoon. Outlook... Friday Night...No marine headlines expected. Saturday through Saturday Night...Small Craft Advisory conditions possible (30-40%), mainly for the New Jersey coastal waters as seas get near 5 feet. Sunday through Tuesday...Small Craft Advisory conditions possible (50%) with seas around 5 feet and gusts nearing 20 kt. Rip Currents... For the remainder of today...A High Risk of Dangerous Rip Currents is in effect until 8 PM for both the Jersey Shore and Delaware Beaches. For Friday...East winds around 5-10 mph. Breaking waves heights of 2-3 feet with a 10-11 second period. As a result, have maintained a MODERATE risk of the development of dangerous rip currents for both the Jersey Shore and Delaware Beaches. For Saturday...East winds around 10-20 mph for Monmouth, Ocean, and Atlantic Counties with breaking wave heights of 3-4 feet. Due to onshore flow and higher wave heights, have opted to go with a HIGH risk of rip currents for these areas. For Cape May and Sussex Counties, east-southeast winds around 10-15 mph and breaking waves of 2-3 feet. Due to lesser wind/wave values, opted for a MODERATE risk of rip currents for these areas. Rip currents occur often in the vicinities of jetties and piers and the speed of the currents are generally maximized at low tides. For specific beach forecasts, visit weather.gov/beach/phi && .TIDES/COASTAL FLOODING... Tides and water levels continue to diminish through Friday. The Coastal Flood Advisory remains in effect through Friday evening for Sussex County, DE as Little Assawoman Bay and the Indian River Inlet have been slow to drain. Minor tidal flooding remains likely through the end of the week within the back bays. The Coastal Flood Advisory in Ocean County remains in effect through 11 PM tonight, as periods of minor tidal flooding are expected within Barnegat Bay. No further advisories are expected thereafter. Along the Eastern Shore, some spotty minor tidal flooding remains possible through the end of the week around the night- time high tide, though no advisories are expected to be needed. Otherwise, no other tidal issues are expected on the Delaware Bay, tidal Delaware River, nor the New Jersey coast outside of Ocean County through the rest of the week. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...Coastal Flood Advisory until 11 PM EDT this evening for NJZ020- 026. DE...Coastal Flood Advisory until 8 PM EDT Friday for DEZ003-004. MD...None. MARINE...Small Craft Advisory until 2 AM EDT Friday for ANZ450>455. && $$ SYNOPSIS...Robertson NEAR TERM...MJL/RCM SHORT TERM...Robertson LONG TERM...Robertson AVIATION...MJL/RCM/Robertson MARINE...DeSilva/MJL/RCM/Robertson TIDES/COASTAL FLOODING...