Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 281109 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 709 AM EDT Thu Mar 28 2024 .SYNOPSIS... A slow moving cold front will approach our region from the west as a wave of low pressure tracks northeastward off the coast today, resulting in a period of unsettled weather. Weak high pressure will begin to build in on Friday. A weak clipper system may move through on Saturday, otherwise fairly quiet and seasonable conditions will prevail over the weekend. Another period of rainy weather is expected early next week as low pressure tracks toward our region from the Ohio Valley. && .NEAR TERM /THROUGH TONIGHT/...
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No major changes have occurred with the forecast through today. Much of the area will experience a rainy day with increasing northerly winds and temperatures near 50 degrees. Troughing shifting eastward toward the East Coast will amplify by later today, with broad diffluence across the region aloft. Surface low pressure across eastern coastal North Carolina this morning will lift northeastward and eventually offshore later today along a baroclinic zone in place due to a stalled frontal boundary. Meanwhile, a subtle cold front will pass southward across the area and offshore throughout the day. The strongest forcing with this system will impact the area around midday as the surface low begins making its closest pass to our area. This is when more widespread, steadier/heavier rain is currently anticipated. The rain so far has been fairly periodic in nature. The system and rain will depart late this afternoon and evening. The rain may linger near the coast as late as 10 PM to midnight or so. As of 7 AM, roughly 0.25-0.75" of rain has fallen across the area. Additional rainfall amounts of 0.10-0.50" are forecast along and northwest of I-95 (greatest amounts along I-95), and around 0.50-1.50" are forecast across the coastal plain with the highest amounts likely along the immediate coast. This rain may lead to additional rises on creeks, streams, and river across the area, however the likelihood of any significant flooding with this event is low (10% or less). Winds will settle out of the north to northwest today around 5-10 mph. The winds will increase into tonight to near 10-20 mph with gusts up to 25 mph possible. Temperatures will remain mild in the 40s to near 50s through today, although the cold advection beginning tonight will drop us back into the mid to upper 30s for low temperatures by Friday morning.
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&& .SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/... Friday will feature a return to dry and sunny but windy weather as a broad upper-level ridge encompassing much of the central and eastern portions of the United States expands eastward toward the East Coast. Surface high pressure centered across the southeastern US with a weak ridge extending northward to the west of the Appalachians will start to take control, but as strong low pressure lifts out toward Nova Scotia, a strong pressure gradient will keep gusty northwest winds across the mid-Atlantic and Northeast on Friday. Expect gusts of 30 to 35 mph, locally/briefly higher over exposed higher elevations toward the Appalachians. Temperatures will be fairly seasonable, gradually moderating heading into the weekend, with lows mainly in the 30s and highs in the 50s. A weak `clipper` system is still is projected in the model guidance to pass ESE across PA toward Delaware Bay on Saturday, along with a weak shortwave trough. The system will lack much moisture, so while some scattered showers are forecast to pass through portions of the area, some spots may end up dry, with less than a quarter-inch of rain even where showers or a briefly steadier period of rain does focus in around midday through Saturday afternoon. Westerly breezes will continue to ease Saturday into Saturday night. && .LONG TERM /SUNDAY THROUGH WEDNESDAY/... Weak high pressure passing eastward from the Great Lakes across the Northeast should result in quiet weather on Sunday, and the overall nicer day of the weekend as milder air continues to filter in on a westerly breeze. Lows in the 40s should be followed by highs mainly in the 60s. Some partial sunshine can be expected, but the sky cover forecast is somewhat questionable as one shortwave passes by to our north, as a warm front begins to approach from the Ohio Valley, probably at least resulting in some high cloudiness around. Heading into early next week, the weather pattern will turn increasingly active across the eastern US. An upper-level trough over the Southwest will eject northeastward, with low pressure tracking across the Ohio Valley by Tuesday. An approaching warm front could bring some rain into our region as early as Monday, but models vary on that timing, so we have just a 30-50 percent chance of rain right now. Tuesday and Tuesday night, possibly into Wednesday, looks like the most likely period of wet weather, as that low pressure area lifts toward the lower Great Lakes, then transfers to a strengthening coastal low that lifts northeastward from the northern mid-Atlantic or New England. A rather potent upper-trough will drop southeastward across the Great Lakes and possibly phase with the aforementioned trough, supporting this strong area of low pressure. Will have to monitor this system for some heavy rain potential, followed by some gusty winds later Wednesday into Thursday. The greater impacts though look to target New England, especially northern portions, where a late-season snowstorm looks likely for them. Our temperatures will remain seasonably mild, with highs generally in the 50s and lows in the 40s early through mid next week. && .AVIATION /11Z THURSDAY THROUGH MONDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Through Today...Generally prevailing IFR conditions this morning in light to moderate rain should gradually improve toward MVFR this afternoon between 16-20Z. There may be some brief periods of improvement to MVFR or VFR at times, but this will not be the prevailing condition through 16Z. Light and variable winds early will settle out of the north to northwest by late morning near 5-10 kts. Improvement to VFR is forecast for all locations between 20- 00Z. High confidence on restrictions in rain today, and moderate confidence on the timing of improvements later today. Tonight...VFR with clearing skies. Northwest winds 10-15 kts with some gusts near 20 kts possible at times. North to northwest winds near 2kft increasing to 35-40 kts may lead to some LLWS, but surface winds should remain elevated enough to preclude a TAF mention. High confidence. Outlook... Friday: Mainly clear and VFR. Windy with gusts to 30 kt. Saturday: Mainly VFR but at least some mid-level ceilings with a chance of showers. Sunday: Mainly VFR and rain-free. Monday: Chance of rain and possible sub-VFR conditions in both CIGs and VSBY. && .MARINE...
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Rain and fog will restrict visibility to around 1-3 NM for much of the day and into the evening. North to northwest winds will increase this evening with wind gusts near 35 kts forecast for a few hours between midnight tonight and mid-morning Friday. Thus, the Gale Watch was upgraded to a Gale Warning for tonight for all Atlantic and Delaware Bay coastal waters. Seas will also increase to around 4-7 feet tonight. Outlook... Friday...In the wake of low pressure lifting out east of New England, fair but windy weather is forecast, with northwest winds prompting Gale Warnings overnight into early Friday morning. If we do have some gale gusts (greater than 34 kt) across portions of the coastal waters lingering early in the morning, we have high confidence that those will diminish to SCA level winds/seas later Friday. However, gusts to 30 kt will still linger, even across Delaware Bay, with rough seas 5 to 7 ft across the open ocean. Saturday and Sunday...SCA conditions with respect to both winds and seas should end by Saturday morning, with westerly winds around 10-15 kt for the weekend. Chance of light rain later Saturday, otherwise mainly fair weather. Seas around 3 ft. Monday...Winds switching to easterly 10-15 kt as a warm front approaches with a chance of rain. Seas around 3 ft.
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&& .TIDES/COASTAL FLOODING... The threat of coastal flooding has come to an end, and it looks like we will continue to have no concerns for flooding through the weekend. We have been keeping an eye on tide gauges along the lower Delaware River overnight, but it looks like water levels are trending a little lower than forecast, so we may not even see any spotty minor flooding with high tide this morning. && .PHI WATCHES/WARNINGS/ADVISORIES...
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PA...None. NJ...None. DE...None. MD...None. MARINE...Gale Warning from 6 PM this evening to 10 AM EDT Friday for ANZ430-431-450>455.
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&& $$ SYNOPSIS...Staarmann NEAR TERM...Staarmann SHORT TERM...Dodd LONG TERM...Dodd AVIATION...Dodd/Staarmann MARINE...Dodd/Staarmann TIDES/COASTAL FLOODING...Dodd

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