Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 250131 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 931 PM EDT Sun Mar 24 2024 .SYNOPSIS... High pressure over southeast Canada will extend into the Mid- Atlantic region through Tuesday. An area of low pressure will track northwest of the area on Wednesday with a trailing cold front that will approach from the Midwest on Thursday. A coastal low may potentially develop along this front and track northward into the Canadian Provinces by Friday. High pressure returns late Friday ahead of a weak disturbance arriving later next weekend. && .NEAR TERM /THROUGH MONDAY/...
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As of 930 PM, all remains quiet across the area with a clear sky and light winds. Given the chilly and dry air mass, temperatures have dropped a decent amount so far especially locations where the wind has gone calm. Overall, no significant changes were needed with this update with just some tweaks to the hourly grids to keep them current based on the latest observations and trends. Low temperatures tonight will drop into the mid/upper 20s to low 30s for most areas. Otherwise, low pressure well offshore will meander around out there through Monday. As this occurs, the pressure gradient will tighten some to its northwest into our area late tonight and especially during Monday. This combined with strong high pressure to our north will result dry and cool weather, however there will be an uptick in the winds Monday especially closer to the coast. A mostly clear sky is expected Monday, and after cold morning lows, temperature readings will climb into the upper 40s/low 50s for most areas. An increasing northeast wind however will also become gusty at times especially closer to the coast. Wind gusts along the coast look to be about 30-35 mph.
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&& .SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/... The short term period will be relatively quiet as our area remains wedged between two separate low pressure systems. The ridge axis of the high pressure over southern Canada remains over the Mid-Atlantic region through most of Tuesday before departing by Tuesday night. To the east over the Western Atlantic, will be a stalled area of low pressure whereas to the west across the High Plains, will be an area of low pressure tracking north of the Great Lakes. Despite our area remaining under high pressure, some low level marine stratus will stream in off the western Atlantic on Monday night persisting into Tuesday. Some drizzle may be possible near coastal areas due to the combination of northeast winds and moisture trapped underneath the surface inversion. Elsewhere, expect dry conditions under mostly cloudy skies. Moving into Tuesday night, the cold front associated with low pressure tracking north of the Great Lakes will begin to approach. With better forcing over our northern and western areas, some rain showers are possible. Overall, should remain pretty light in nature as frontal boundary will be weakening as it approaches. In terms of temps, expect lows in the 30s Monday night and highs in the 40s-50s on Tuesday. With more low-level moisture around on Tuesday night, temps will be a bit warmer than the night prior, generally in the lower 40s. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... The long term period as whole will become unsettled with several chances for some precipitation. The cold front to the west will slow down in forward motion and weaken as it approaches; coming to a crawl near our region on Wednesday. As the front potentially stalls, the majority of deterministic and ensemble long range guidance depicts a coastal trough and an eventual coastal low forming along the boundary on Thursday. This will bring another round of rain to the region, with PoPs holding steady in the 60-80% range through Thursday. The low begins to pull away Thursday night as it nears Nova Scotia, resulting in just some residual showers. For Friday and Saturday, mostly dry conditions are expected as high pressure builds in from the south and west. Will have to watch a warm front that approaches from the west later Saturday associated with another low pressure system that may impact the area for the second half of the weekend. This may bring another round of showers during the Saturday night and Sunday period, but PoPs are only around 20% at this time. && .AVIATION /02Z MONDAY THROUGH FRIDAY/...
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The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas... Rest of tonight...VFR. Northeast winds 10 knots or less, becoming locally light and variable. High confidence. Monday...VFR. Northeasterly winds 8-15 knots with gusts 20-25 knots, with the strongest winds at KMIV and KACY. Moderate confidence. Outlook... Monday night...VFR early, becoming sub-VFR overnight with some marine stratus. NE winds 7-12 kt. Higher gusts up to 20 kt possible at KACY. Moderate confidence. Tuesday through Tuesday night...Sub-VFR. Drizzle possible near KACY during the day, with showers developing at night. NE-E winds around 10 kt during the day, becoming 5 kt or less at night. Low confidence. Wednesday through Wednesday night...Sub-VFR with periods of rain. SE-S winds around 5-10 kt during the day, becoming NW-N winds around 5 kt at night. Low confidence. Thursday through Thursday night...Sub-VFR with periods of rain. NW-N winds around 10-15 kt with gusts up to 20 kt. Low confidence. Friday...VFR with clearing skies. NW winds around 15-20 kt with gusts up to 30 kt. Moderate confidence.
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&& .MARINE...
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Low pressure well offshore will meander out there through Monday. It should be far enough away to keep winds up, especially during Monday, however they should remain Gale-force. Enhanced seas will continue. The northeast winds have diminished some this evening, however an increase is expected overnight and especially during Monday. It appears the winds for the upper Delaware Bay will remain below Small Craft Advisory criteria while lower Delaware Bay will continue with advisory level gusts and seas (near the mouth) at least through Monday. Outlook... Monday night through Tuesday...SCA conditions likely to continue. NE winds around 25-30 kt. Seas of 8-12 feet. Tuesday night through Wednesday night...SCA conditions likely to continue due to elevated seas. NE winds around 10-15 kt on Tuesday night, becoming N-NE winds around 5-10 kt for Wednesday and Wednesday night. Seas of 5-8 feet. Thursday...Marginal SCA conditions. NW-N winds around 10-20 kt. Seas of 4-5 feet. Thursday night through Friday...SCA conditions likely to return. NW winds around 15-25 kt with gusts up to 30 kt. Seas of 4-6 feet.
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&& .TIDES/COASTAL FLOODING... The coastal low that brought the heavy rain Saturday has departed to the north and east but a second low has developed along its cold front and is located off the southeast coast. This low will strengthen while moving north and then lingering out over the Atlantic. This will result in an extended duration of long period swells and rough surf impacting the Atlantic coast. Surge values of 2-3 feet are currently forecast by Monday. This will result in widespread moderate flooding along the oceanfront and Delaware side of the Delaware Bay. Thus, we have issued Coastal Flood Warnings starting early Monday, when widespread minor flooding begins, but right now the highest tide appears to be Monday evening`s. Some guidance has moderate flooding lingering several cycles, but for now have cut off the warning at 2 PM Tuesday. Minor flooding looks likely across the New Jersey side of the Delaware Bay and the New Castle County portion of the Delaware side by Monday evening, but as that is still over 24 hours out, and some uncertainty remains regarding how the event will transpire, will hold off another cycle before issuing coastal flood advisories for these areas. Only spotty minor flooding is expected along the Tidal Delaware river north of Delaware through Philadelphia up to Trenton. Coastal flooding is not anticipated along the eastern shore of Maryland. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...Coastal Flood Warning from 6 AM Monday to 2 PM EDT Tuesday for NJZ020-022>027. Coastal Flood Warning from 6 PM Monday to 2 PM EDT Tuesday for NJZ012>014. DE...Coastal Flood Warning from 6 AM Monday to 2 PM EDT Tuesday for DEZ002>004. MD...None. MARINE...Small Craft Advisory until 7 PM EDT Monday for ANZ431. Small Craft Advisory until 6 AM EDT Tuesday for ANZ450>455. && $$ SYNOPSIS...DeSilva/Fitzsimmons NEAR TERM...Gorse/OHara SHORT TERM...DeSilva LONG TERM...DeSilva/Fitzsimmons AVIATION...DeSilva/Gorse/OHara MARINE...DeSilva/Gorse/OHara TIDES/COASTAL FLOODING...RCM

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