Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 231315 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 915 AM EDT Sat Mar 23 2019 .SYNOPSIS... Strong low pressure will gradually work its way across the Canadian Maritimes today and tonight. Meanwhile, high pressure will build into the Ohio Valley today then just to our south tonight and Sunday. A cold front will settle southeastward across our area late Sunday night and Monday while a weak area of low pressure tracks along it. High pressure builds in Tuesday and Wednesday before slowly shifting eastward later Thursday and Friday. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Increased wind gusts just a bit in the far north to account for observations in that area showing a peak gust of 58 MPH at High Point NJ (1800 feet ASL) and certainly not respresentative of the entire area. Vsbl satellite imagery shows cloud cover moving out with the departing low, and is represented very well by the current forecast. Temperatures also look on track, so no major changes to the current forecast package. ...Previous near term discussion below.... Strong low pressure will drift to the northeast across Canada`s Maritime Provinces and the Gulf of Saint Lawrence today. Meanwhile, high pressure will build from the western Great Lakes and the Ohio River Valley toward the Carolinas. The tight pressure gradient between the two features will maintain a strong west northwest wind in our region. Sustained wind speeds should range from 15 to 25 MPH with gusts up to 30 or 40 MPH. Wind speeds are forecast to begin slowly diminishing during the course of the afternoon. Clouds are expected to linger through about mid morning, especially over parts of eastern Pennsylvania and New Jersey. Very dry air will build into our region for this afternoon, with a clear sky anticipated at that time. Maximum temperatures are expected to range from the lower 40s on the Pocono Plateau to the middle 50s in southern Delaware. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SUNDAY/... The strong low will move farther away to our northeast tonight as high pressure settles in the Carolinas and Virginia. We are anticipating a clear sky. The west northwest wind is forecast to decrease to less than 10 MPH early this evening with the wind becoming light and variable overnight. The ideal radiating conditions should allow temperatures to fall into the 20s in much of our region. Readings may not drop below the lower 30s in urban locations and in areas near the coast and bays. && .LONG TERM /SUNDAY THROUGH FRIDAY/... Summary...Mainly some rain later Sunday night and Monday with a cold front and wave of weak low pressure; Cooler Tuesday; Warming takes place Wednesday through Friday. Synoptic Overview...A large upper-level trough amplifies across New England later Sunday and Monday with a cold front pressing southeastward across our region. A trough remains in the East through Tuesday, then the flow becomes more zonal for a time. An upper-level trough amplifies into the Plains toward late next week, building a ridge to the east. For Sunday and Monday...Surface high pressure is forecast to be shifting east of the Carolinas Sunday. An upper-level trough amplifies across eastern Canada and eventually into the Northeast, with a cold front arriving in our area Sunday night and Monday morning. There looks to be limited moisture with the cold front, however some showers should occur as it arrives. A short wave embedded within the northwesterly flow aloft tracks from the Midwest Sunday to the Mid-Atlantic coast by late Monday. This eventually looks to get absorbed with the incoming amplifying trough, however a weak surface low associated with it tracks along the aforementioned surface cold front as it settles southeastward. While the guidance does vary some with how much shower activity accompanies the front, the bulk of the guidance focuses more precipitation with the wave of low pressure. The QPF looks to be on the lighter side as the system should be moving right along. The majority of this is anticipated to be rain, however if enough cooling arrives across the north some snow could mix in. Overall though it looks like the colder air arrives after the majority of the precipitation ends. In addition, much drier air looks to move in a bit faster from south to north during Monday and this should also help to keep the more organized precipitation becoming more focused across the southern areas with time. Prior to the arrival of the cold front, a milder flow will occur Sunday allowing temperatures away from the coast to get well into the 50s to near 60 degrees, then cooling occurs during Monday and especially Monday night when it turns colder. For Tuesday...As an upper-level trough amplifies across the East, some ridging across the Midwest will drive an expansive high pressure system eastward into our area during Tuesday. This should drive much drier air southward despite a northeast low-level flow. As a result, any precipitation lingering across the Delmarva early should rapidly end as low pressure moves out to sea. Our sensible weather is then dominated by the aformentioned surface high building over and to our north and northeast through Tuesday night, and this will keep a chilly airmass in place. For Wednesday through Friday...Looks like a sliver of tranquil weather for our area as surface high pressure becomes entrenched across our area and extends to the northeast. This is between an eventual trough that ejects out into the Plains toward the end of the week, and low pressure east of the Southeast coast. The trough out West eventually will send low pressure northeastward from the southern Plains, however that will probably not approach until later Friday night. In the meantime, a warming trend is expected to take place after a chilly to cold start. The warming however may be slowed closer to the coast given the surface winds may retain an onshore component longer. For now, kept some rather low PoPs especially for the western areas by late Friday. && .AVIATION /13Z SATURDAY THROUGH WEDNESDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Today...VFR. Decreasing clouds this morning, clear this afternoon. West northwest wind 16 to 22 knots with gusts of 28 to 36 knots. Tonight...VFR under a clear sky. West northwest wind around 8 to 12 knots becoming variable 6 knots or less. OUTLOOK... Sunday...VFR as clouds increase and lower, especially at night. Some showers possible toward daybreak Monday. West-southwest winds 10 knots or less. Monday...VFR ceilings, which may briefly lower to MVFR with some rain especially from the PHL area southward. West-northwest winds becoming northerly around 10 knots. Tuesday and Wednesday...VFR. Northeast winds around 10 knots, becoming east to southeast less than 10 knots by later Wednesday. && .MARINE... A west northwest wind at 20 to 30 knots is forecast to continue for much of the day. Frequent gusts in the 30 to 40 knot range are expected. Wind speeds will likely begin to decrease slowly this afternoon. We will keep the Gale Warning in place until 6:00 PM for the coastal waters of New Jersey and Delaware and for Delaware Bay. The west northwest wind will continue to diminish tonight, with conditions anticipated to fall below Small Craft Advisory levels shortly after midnight. Outlook... Sunday and Monday...The conditions are anticipated to be below Small Craft Advisory, however northeast winds increase later Monday night and may gust to around 25 knots. Tuesday...Small Craft Advisory conditions probable for a time, especially for the Atlantic coastal waters where seas will be around 5 feet. Wednesday...The winds are anticipated to be below Small Craft Advisory criteria, however seas may linger around 5 feet especially in the southern Atlantic coastal waters. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...Gale Warning until 6 PM EDT this evening for ANZ430-431- 450>455. && $$ Synopsis...Gorse Near Term...Iovino/Miketta Short Term...Iovino Long Term...Gorse Aviation...Gorse/Iovino Marine...Gorse/Iovino

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