Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 290135 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 935 PM EDT Thu Mar 28 2024 .SYNOPSIS... Low pressure moves up toward Nova Scotia tonight as cold front moves off the coast. High pressure briefly builds in on Friday. A weak clipper system passes through late on Saturday with drying expected on Sunday. An area of low pressure will develop over the Central Plains on Monday with a warm front extending east into the Mid- Atlantic. This will lead to unsettled conditions through at least the middle portion of next week before drying out on Thursday. && .NEAR TERM /THROUGH FRIDAY/...
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As of 9:30PM...Forecast remains mostly in line. Brushed up sky cover and PoPs just a bit to better reflect frontal position and movement. Otherwise, no other changes to the forecast were made for this update. Secondary cold front is pushing offshore. Main cold front well offshore of our region continues to slowly move away as surface low pressure off the coast of the Carolinas nudges northeastwards. This surface low pressure will look to track out to sea tonight and will move towards the Canadian Maritimes Friday afternoon. Surface high pressure builds in from the west late tonight through Friday as an H5 trough passes through the East Coast during the day Friday. Rain continues, mostly along the coast, for the next hour or so. Skies clear out tonight, and then skies will be mostly sunny on Friday, though some mid and high clouds are possible with the passage of the trough. A tight pressure gradient forms between low pressure to the east and high pressure building in from the west. Northwest winds will increase to 10 to 15 mph tonight, and then will increase further to 15 to 20 mph with 30 to 35 mph gusts for most of Friday. Although northwest flow will be in place behind a departing cold front on Friday, there will be enough sunshine on Friday for high temperatures to rise into the mid and upper 50s.
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&& .SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/... High pressure will be located off the Southeast US on Friday night as the area lies in between low pressure systems. Winds will noticeably diminish overnight as most areas will settle underneath the surface inversion. However, breezy conditions will continue at higher elevations in excess of 30 mph. Lows will be in the 30s areawide with clear skies. Overall, the start of the weekend will be quite seasonable with widespread sunshine for Saturday morning. Temps will rebound nicely through the day with highs ranging in the mid to upper 50s to low 60s under modest southwest flow; which will aid afternoon mixing. However, the sunny weather will be short-lived as clouds increase through the afternoon as a weak clipper system transverses across the area early Saturday night. This system will be weakening as it approaches so not expecting a washout by any means. Isolated to scattered rain showers are expected late Saturday into early Saturday night before moving away from the area. The best chance for shower activity is north of the Philadelphia area. Rainfall amounts are minimal, generally less than a tenth of an inch. After the clipper system passes by, weak high pressure will build in from the Great Lakes and across the Northeast. This should result in quiet weather on Sunday under partly cloudy skies. All in all, a nicer day is expected with highs in the 60s despite a gusty northwesterly breeze. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... The long term period will be quite different from the short term as an active, wet, and unsettled period looms. A stalled frontal boundary will be located over the Carolinas as a low pressure system develops over the Central Plains. This system will extend a warm front eastward into the Mid-Atlantic region beginning as early as Monday. The warm front will continue to nose eastward with time as the low translates east toward the Great Lakes region by Wednesday. This will lead to several opportunities for rain to be directed toward our region. The first comes Sunday night into Monday where PoPs are around 40-60% across the region. A more steadier period looks to occur Monday night through much of Tuesday as PoPs further increase to 60-80% areawide. Depending on the track, evolution and timing of the low will determine how long rain lingers across the area. Model guidance this afternoon continues to show the area of low pressure lifting into the Great Lakes, then transferring its energy to a strengthening coastal low that lifts northeast toward 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. && .AVIATION /02Z FRIDAY THROUGH TUESDAY/...
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The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Tonight...VFR with skies clearing out in the latter half of the period. NNW winds around 10 kts to start, becoming more NW and increasing to 10-15 kts with gusts up to 20 kts late. Friday...VFR. NW/WNW winds 10-20 kts with gusts of 25-30 kts. High confidence. Outlook... Friday night...VFR/SKC. W-NW winds around 5-10 kt. High confidence. Saturday...VFR early, with sub-VFR later in the day with isolated to scattered rain showers. SW-W winds around 10-15 kt. Moderate confidence. Sunday...VFR expected under partly cloudy skies. Slight chance of rain showers at night. W-NW winds around 15-20 kt. Moderate confidence. Monday and Tuesday...Sub-VFR expected with periods of light rain. E- SE winds around 10 kt on Monday, becoming NE winds on Tuesday. Low confidence.
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&& .MARINE...
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Northwest winds 15-20 kts will ramp up to around 20-25 kts with 30-35 kts gusts late tonight into Friday morning. A Gale Warning remains in effect, though gale gusts of 34 kts or higher may only occur for a 2 to 3 hour window late tonight. Guidance continues to be on a downward trend regarding the possibility of gale force winds. However, given the meteorology of the situation (e.g., anticipated mixing) will keep the Gale Warning in effect. The best chances for gales will be on Delaware Bay and the Delaware ocean waters. On Friday, WNW winds will range from 20-30 kts. A Small Craft Advisory will be needed once the Gale Warning comes down. Rain until midnight or so, and then conditions improve as rain ends. Outlook... Friday night...SCA conditions likely continue. W-NW winds around 15- 20 kt with gusts up to 25 kt. Seas of 3-5 feet. Saturday through Sunday...No marine headlines expected. SW winds around 10-20 kt on Saturday, becoming W-NW around 10-15 kt on Sunday. Seas of 3-4 feet. Monday through Tuesday...No marine headlines expected. NE-E winds around 10-15 kt on Monday, becoming E-SE around 15-20 kt on Tuesday. Seas of 2-4 feet.
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&& .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...Gale Warning until 10 AM EDT Friday for ANZ430-431-450>455. && $$ SYNOPSIS...DeSilva/Staarmann NEAR TERM...MPS/Wunderlin SHORT TERM...DeSilva LONG TERM...Dodd/DeSilva AVIATION...DeSilva/MPS/Wunderlin MARINE...DeSilva/MPS/Wunderlin

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