Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 251103 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 703 AM EDT Mon Sep 25 2023 .SYNOPSIS... The remnants of Ophelia will drift slowly southward and offshore through Wednesday, resulting in onshore flow and some lingering rain, especially toward the coast. High pressure builds over southern Quebec and the Northeast states, pressing southward through early Thursday. An upper level low passes by late in the week, but otherwise high pressure will expand southward from New England down the Appalachians through the weekend. && .NEAR TERM /THROUGH TONIGHT/... Another dreary day is expected across the region as the remnants of Ophelia continue to spin through the region early this morning before moving offshore. Latest observations place the low to the southeast of Philadelphia, in South Jersey. Areas of rain and drizzle continue to pivot around the low, mainly on the northern side with the heaviest rain just to the north of our region across northeastern PA and southern NY. This pattern of drizzle closer to the low with relatively heavier areas further north will continue as the low spins off to the southeast and offshore late this morning/early this afternoon. This action will draw the more concentrated precip back into the northern portions of our area but accumulations are expected to be light with little in the way of instability. Less than 0.50 inches is expected across most of the area with localized totals around 1 inch possible, across northwest New Jersey and the southern Poconos where upslope along the terrain may provide a bit of extra forcing. The other main concern as the remnant low moves offshore will be increasing winds and wind gusts, particularly at the immediate shore. With a tightening pressure gradient, gusts as high as 35 to 40 mph will be possible at the immediate coast, with gusts generally around 20 to 30 mph inland. These higher gusts will initially be limited to the northern Jersey Shore before spreading from north to south as the low continues to pivot away offshore. By late tonight/early Tuesday, the higher gusts will be possible across the entire Atlantic Ocean coast of New Jersey as well as the Atlantic coast of Delaware. Otherwise, with the overcast skies temperatures will continue to be rather cool with highs mainly in the 60s today before decreasing into the 50s tonight. && .SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/... Tuesday through Wednesday will feature a blocking ridge over eastern Canada, with strong surface high pressure slowly building southward from Quebec across New York and New England, as the synoptic pattern across the eastern US remains rather slow-moving and stagnant. Meanwhile, our weather locally will be largely determined by the remnant area of low pressure from former Tropical Storm Ophelia, which will drift slowly southeastward off the mid-Atlantic coast. The low will eventually drop to east of Cape Hatteras by late Wednesday, though model guidance is in some disagreement on the exact placement by that point. Not completely unlike the pattern we have been dealing with all weekend, the key component here will be a strong pressure gradient between the aformentioned high to the north and low pressure drifting south. That will drive strong onshore flow at least on Tuesday, gradually easing on through Wednesday as the low drifts farther away. While more dynamic forcing will be lacking compared to the weekend, and stronger isentropic lift will be positioned farther offshore, there will be enough low-level moisture advection and convergence, particularly toward the shore and the Delmarva, to keep overcast skies along with light rain. This will be aided by frontogenesis along a baroclinic zone, as cooler air in association with the high to the north presses southward against our prevailing warm, moist airmass. Initially, dewpoints along the coastal plain Tuesday morning will be in the upper 50s and low 60s, but will drop through the 50s heading into Tuesday night, with some 40s making their way southeast to I-95. That will represent some drier air and subsidence making it`s way in aloft as well, allowing for at least some partial clearing skies northwest of I-95 Tuesday night through Wednesday. Clouds will persist to the southeast. The misty rain will only add up to perhaps a quarter-inch or so along the immediate coast from Tuesday through Wednesday, with only around a few hundredths back to the urban corridor on Tuesday. That will be accompanied by a raw northeast breeze, occasionally gusting to 20 mph inland, with downright windy conditions along the immediate coast, with gusts over 30 mph common. Those winds will ease substantially on Wednesday, but it will remain rather breezy, mainly overcast and a little damp near the coast. Some drying and breaks in the clouds may make it down to Tom`s River. Highs both days will be only in the low to mid-60s, with Tuesday being the coolest day of the week. This stretch of early autumn weather will represent some of our coolest daytime temperatures since early May. && .LONG TERM /THURSDAY THROUGH SUNDAY/... Blocking high pressure centered over Quebec will remain in control Thursday, but will weaken with associated surface high pressure shifting east across New England. That will maintain relatively cool onshore flow, but will at least allow the airmass to modify more, with high temperatures approaching 70 from near Philadelphia southward. Unfortunately, that will also allow for a weak upper-low near Lake Michigan to escape eastward, reaching the northern mid- Atlantic by Thursday night. That suggests that skies will probably stay mostly cloudy Thursday. Have a slight chance of showers late per NBM guidance, but to be honest that seems doubtful given the position of the surface high still wedging down the Appalachians, keeping the low-levels rather dry. Even by Friday when NBM has low chance showers in, the surface high remains, so that any showers that make it in will likely be spotty and light at worst. Later shifts may consider pulling shower chances altogether. By Saturday, that upper low will push quickly offshore. A rather strong late-season ridge will expand and shift eastward from the Plains across the Ohio and Tennessee Valleys through the weekend, with broad surface high pressure drifting down the Appalachians. Kept some slight chance POPs in on Saturday and down to the coast on Sunday per NBM, but that looks aggressive as well. If the pattern holds on the next model run or two, later shifts should probably trend more optimistic. In fact, next weekend could turn out very pleasant. We have highs in the forecast warming into the low to mid 70s, but warmer than that is a good possibility given then pattern, and that may be accompanied by more sun than clouds as well. && .AVIATION /11Z MONDAY THROUGH FRIDAY/...
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The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas... Monday...IFR ceilings may lift to low-end MVFR through the day. Occasional MVFR visibility during some rain especially north of PHL. North to northeast winds 5-10 knots, increasing to 15-20 knots with gusts up to 25 knots from mid-morning into the afternoon. Strongest winds should be closer to the coast. Low confidence. Monday night...MVFR/IFR gradually improving towards high-end MVFR. Continued periods of rain possible, particularly closer to the coast. Gusts largely dropout with northeasterly winds becoming sustained around 10 to 15 kts, with the higher speeds closer to the coast. Low confidence, especially on timing of any improvements. Outlook... Tuesday...Starting out MVFR to IFR ceilings everywhere, with misty light rain especially from I-95 to the coast resulting in MVFR to IFR VSBY, especially in the morning. CIGS improve to VFR ABE/RDG, MVFR I-95 TAF sites. Winds NE 10-15 G 20 kt, with G 30 kt near the coast. Moderate confidence. Wednesday... MVFR to IFR from I-95 to the coast at least in the morning due to ceilings. Some lingering light rain near the coast. Improvement to VFR possible I-95 northwestward. Winds NE 10-15 kt. Moderate confidence. Thursday through Saturday...Mainly VFR. NE-E winds around 10-15 kt. Low confidence.
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&& .MARINE...
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As the remnant low of Ophelia continues to track near our area, multiple marine hazards remain. As we head through the day, waters north of Little Egg Inlet will see the development of Gale force wind gusts of up to 40 knots as northeasterly winds restrengthen. Seas will also build to 7 to 9 feet in this area. Therefore, a Gale Warning is in effect for this area and will continue through Monday night. Coastal waters south of Little Egg Inlet but north of Cape May will continue to see SCA conditions so the SCA will continue through the day for these areas. Seas south of Cape May as well as on the Delaware Bay will be less than 5 feet with winds around 10 knots. As we head into this evening, conditions will begin to degrade further, particularly south of Cape May and on the Delaware Bay. Northeasterly winds restrengthen in this area with gusts increasing to 25 to 30 kts and seas on the ocean increasing to 7 to 9 feet. Therefore, new Small Craft Advisories are in place beginning at 6 PM and 8 PM on the Delaware Bay and for Atlantic Ocean waters south of Cape May respectively. These will continue through Monday night as will the SCA for Atlantic Ocean waters south of Great Egg Inlet. The strengthening winds this evening will cause gusts off the coast of Atlantic County to strengthen to Gale force as well so the SCA for ANZ452 will be converted to a Gale Warning as well beginning at 6 PM. Outlook... Leftover remnant low pressure from former Tropical Storm Ophelia will continue sinking southward off the southern NJ/DE/MD coast Tuesday, eventually pushing southeast to offshore of Cape Hatteras later Wednesday. Meanwhile, strong high pressure pushing in from New England will result in another tight pressure gradient, with strong onshore winds through Tuesday, lessening on Wednesday. Extended the Gale Warning through midday on Tuesday, as we are forecasting gusts near 34 kt north of Atlantic City. SCA conditions will continue over Delaware Bay until Tuesday evening when winds finally start to ease, but elsewhere over the adjacent ocean, advisories will likely continue right into the end of the week at least due to seas. Either way, nasty conditions overall Tuesday with rough seas building to around 9-11 ft. Seas will lower to around 6-8 ft on Wednesday, with NE winds still gusting to around 25 kt. Additionally, there may be some VSBY restrictions in misty light rain, especially on Tuesday. Thursday through Saturday...SCA conditions likely due to seas. NE winds around 15-20 kt. Seas 4-6 feet. Rip Currents... A west to northwest wind 5 to 10 mph is expected for the Delaware Beaches and for Cape May County in New Jersey on Monday. Breaking waves should be around 2 to 5 feet with the higher waves along the shore of Cape May County. As a result, we have been able to lower the rip current risk to MODERATE for those areas for Monday. An increasing north to northeast wind is anticipated for the coastline from Monmouth County down to Atlantic County on Monday with breaking waves of 4 to 6 feet along the Atlantic County shore and 5 to 7 feet further north. Those areas will likely continue to experience a HIGH risk for the development of dangerous rip currents at that time. The increasing northeast wind and building surf will affect the entire New Jersey coast and the Delaware coast on Tuesday. All areas will again be under a HIGH risk for rip currents. The elevated risk of rip currents will likely continue through much of the balance of the new week.
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&& .TIDES/COASTAL FLOODING... Water levels with the evening and overnight high tide cycle were not quite as high as expected, and we were able to cancel the Coastal Flood Advisories early. As of the predawn hours Sunday, all sites are below minor flood stage. Would not rule out some very spotty minor flooding at times today in some of the back bays, mainly along the Ocean County (NJ) and Sussex County (DE) coast. Otherwise, the focus will shift toward Tuesday, and to a lesser degree tonight. First things first...the model guidance suggests that while some spotty minor flooding will be possible along the NJ shore and coastal DE, water levels will fall shy of advisory thresholds. Later shifts will keep an eye on it, though. Heading into Tuesday, with strengthening onshore NE winds, reaching low-end gale force gusts in some areas, and building seas on the open ocean over 10 feet, combined with rising astronomical tides (the full `Harvest` Moon on Friday)...some sites look like they will breach the moderate coastal flood threshold. Have issued Coastal Flood Watches proactively for coastal Kent, Sussex in DE, and the Atlantic and Cape May County coasts. Other sites along DE Bay and farther north along the NJ shore and back bays will probably see minor flooding during Tuesday evenings high tide as well. Thankfully by Wednesday the onshore flow will weaken and seas will subside, which should limit the severity of coastal flooding, but some minor flooding will still be a possibility near high tide Wednesday evening. .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...Coastal Flood Watch from Tuesday afternoon through Tuesday evening for NJZ022>025. High Risk for Rip Currents through Tuesday evening for NJZ014-025- 026. DE...Coastal Flood Watch from Tuesday afternoon through Tuesday evening for DEZ002>004. MD...None. MARINE...Small Craft Advisory from 6 PM this evening to midnight EDT Tuesday night for ANZ430-431. Small Craft Advisory until 6 AM EDT early this morning for ANZ450-451. Gale Warning until 6 PM EDT Tuesday for ANZ450-451. Small Craft Advisory until 6 PM EDT this evening for ANZ452. Gale Warning from 6 PM this evening to 6 PM EDT Tuesday for ANZ452. Small Craft Advisory until 8 AM EDT Wednesday for ANZ453. Small Craft Advisory from 8 PM this evening to 8 AM EDT Wednesday for ANZ454-455. && .PHI WATCHES/WARNINGS/ADVISORIES...
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PA...None. NJ...Coastal Flood Watch from Tuesday afternoon through Tuesday evening for NJZ022>025. High Risk for Rip Currents through Tuesday evening for NJZ014-025- 026. DE...Coastal Flood Watch from Tuesday afternoon through Tuesday evening for DEZ002>004. MD...None. MARINE...Small Craft Advisory from 6 PM this evening to midnight EDT Tuesday night for ANZ430-431. Gale Warning until 6 PM EDT Tuesday for ANZ450-451. Small Craft Advisory until 6 PM EDT this evening for ANZ452. Gale Warning from 6 PM this evening to 6 PM EDT Tuesday for ANZ452. Small Craft Advisory until 8 AM EDT Wednesday for ANZ453. Small Craft Advisory from 8 PM this evening to 8 AM EDT Wednesday for ANZ454-455.
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&& $$ SYNOPSIS...Dodd NEAR TERM...AKL SHORT TERM...Dodd LONG TERM...Dodd AVIATION...AKL/Dodd MARINE...AKL/Dodd TIDES/COASTAL FLOODING...

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