Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 141103 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 703 AM EDT Sun Apr 14 2024 .SYNOPSIS... High pressure will briefly be in control through this morning before an area of low pressure passes to the north of the region and drags a cold front across the Mid-Atlantic region tonight into Monday. High pressure builds back in by late Monday into Tuesday, before a series of frontal boundaries and low pressure systems affect the east coast Wednesday through Friday. && .NEAR TERM /THROUGH TONIGHT/...
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As of 700am...The forecast for today remains largely unchanged. The entire area will get into the warm sector, with temperatures getting into the upper 60s and low to mid 70s. A cold front will approach from the northwest, with showers and thunderstorms developing out ahead of it, taking on a linear mode. The highest instability will be to our west, though with good forcing and relatively high shear, especially in the low- levels, some organized convection will likely make it into our area. The limiting factor is the instability over our region, roughly 300-500 J/KG of MUCAPE. The steepest lapse rates will also be well ahead of the better dynamics. Most of the CAM guidance also has the line of storms coming in right around sunset or even later. Overall, everything really isn`t lining up perfectly for a widespread severe event, and the thinking is that it will be more localized due to the relatively limited instability. The Storm Prediction Center now has a SLIGHT risk for the southern Poconos and portions of the Lehigh Valley and northwest New Jersey. The threat diminishes significantly the further south you go as guidance has the line fizzling rather quickly once the sun goes down. Delmarva and far southern New Jersey actually will likely stay dry. The main threat is damaging wind gusts as a 50-60 kt low level jet will be overhead around the time the line of storms make it to our area which could mix down with any stronger storms. Cannot rule out a tornado as well with good low-level shear and SRH in the 0-1 km layer. The cold front passes overnight and any showers should dissipate by midnight or so. Temperatures will drop into the 50s overnight with upper 40s in the Poconos/northern New Jersey.
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&& .SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/... The main forecast challenge for Monday will be a cold front that will still be our vicinity. There is some uncertainty regarding how quickly it will move through with the NAM and GFS clearing it south through the area Monday morning into the early afternoon while the GEM Regional is several hours slower. The upshot of this is that we did add in a 20 percent chance of showers and thunderstorms for Monday afternoon for our Delmarva Counties into southern NJ as these areas will be the last to see the front clear and so will have at least a slight chance of seeing some afternoon convection. It will be another warm day with most areas seeing highs in the 70s except cooler near the coast and over the southern Poconos. High pressure builds in for Monday night and Tuesday bringing fair weather under mainly clear to partly cloudy skies. Lows Monday night will be mainly in the 40s to low 50s with highs Tuesday mainly in the low 70s except once again cooler right near the coast and over the southern Poconos. The high will start to retreat to our north and east as we head into Tuesday night as the front to our south and west starts advancing back towards the area as a warm front. This will bring an increase in cloud cover with a few showers possible by Wednesday morning, especially over Delmarva into SE PA. && .LONG TERM /WEDNESDAY THROUGH SATURDAY/... In the big picture, the weather pattern will become more unsettled once again as a large upper level trough with a closed off low gradually moves eastward from the Canadian Prairies into into Ontario and Quebec through the mid to late week period. An associated surface low will also consolidate over the Great Lakes region and then move into northern Ontario during this period. This will put our area in a moist deep layer SW flow which will overrun a frontal boundary at the surface that will remain stalled near Delmarva much of this period. The upshot of this is that it will be mostly cloudy with chances for rain/showers each day Wednesday through Friday. The best chances for widespread showers look to be late Wednesday into early Thursday and it is for this time period where we have likely POPs in the forecast. The cloud cover and showers will keep it cooler compared to this weekend and earlier in the week although temperatures will actually be fairly close to average. The upper level trough with its associated frontal system at the surface should finally swing through the area Friday night into Saturday with one final round of showers before there should be a drying trend through next weekend. && .AVIATION /11Z SUNDAY THROUGH THURSDAY/...
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The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas... Sunday...VFR expected at all terminals. Light SW winds early around 5-10 kt will increase by 14-15Z around 10-15 kt with gusts reaching up to 25-30 kt through the afternoon. Some showers and scattered thunderstorms are anticipated to move in during the late afternoon/early evening, mainly for KRDG/KABE. Sub-VFR conditions are possible within any thunderstorm that does occur. Any lingering sub-VFR conditions Sunday night will lift to VFR once the cold front comes through. Moderate confidence overall. Outlook... Monday and Tuesday...VFR conditions expected with fair weather. Wednesday and Wednesday night...Sub-VFR conditions possible (30-40%) with showers. SSE winds around 10 kts to start, gradually increasing to 15 kts by late afternoon with gusts up to 20 kts at night.
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&& .MARINE...
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Winds and seas will remain below SCA criteria for all Atlantic Ocean coastal waters until this afternoon when wind gusts and seas will increase once again to 25-30 knots and 5-7 feet respectively. As a result, an SCA has been issued beginning at 2 PM EDT this afternoon and continuing through tonight until early Monday morning. For the Delaware Bay, sub-SCA conditions are expected through Sunday night. Outlook... Monday and Tuesday...Seas may still be near 5 feet early in the day Monday but otherwise sub SCA conditions expected for this period. Wednesday and Wednesday night...Winds and seas gradually build as the next storm system approaches. SCA conditions possible by Wednesday night.
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&& .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...Small Craft Advisory from 2 PM this afternoon to 8 AM EDT Monday for ANZ450>455. && $$ SYNOPSIS...AKL/Fitzsimmons/MJL NEAR TERM...AKL/DeSilva/Hoeflich SHORT TERM...Fitzsimmons LONG TERM...Fitzsimmons AVIATION...AKL/Fitzsimmons MARINE...AKL/Fitzsimmons

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