Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 291427 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 1027 AM EDT Mon May 29 2017 .SYNOPSIS... Low pressure located off the Middle Atlantic coast early this morning will move farther out to sea today. Another weak low is expected to follow along a trailing frontal boundary and it should pass off the Middle Atlantic coast on Tuesday night. A cold front is forecast to approach from the northwest on Wednesday and it should pass through our region on Wednesday night. Another cold front is anticipated to arrive on Friday night or Saturday. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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An area of low pressure located offshore of the Mid-Atlantic this morning will continue to move eastward and away from the area through today. The associated stationary boundary to our south is forecast to remain to our south, while an approaching occluded front will likely wash out and dissipate as it approaches the area from the west this afternoon. High pressure across the Canadian Maritimes will nose its way down the eastern seaboard and keep a cool and moist easterly flow across the area. Showers and a few thunderstorms across NE Pennsylvania and the northern half of New Jersey are continuing to move northeast and will be out of the area around noon. A few showers have recently developed across Chester county PA. Overall, the mechanisms for precipitation are diminishing, but the low level moisture will remain in many areas with the lowest flow still from the E. We will likely see some breaks develop in the lo clouds, especially across SE PA and Delmarva. It`s difficult to get too optimistic with regards to how much sun will develop across NJ or NE PA. Where clouds remain through the day, temperatures will likely have a hard time rising, but if/where any breaks of sun occur across the southern areas, temperatures will rise more. We used a blend of available MOS and MOSGuide for daytime highs.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM TUESDAY/... The aforementioned occluded front is expected to have dissipated by this evening, while high pressure from eastern Canada continues nosing down the eastern seaboard. With an easterly flow continuing across the area, this will keep cool and moist conditions across the area through the night. It is possible some isolated showers may develop overnight, but patchy areas of fog and drizzle may also occur. Uncertain as how dense fog will get because not much of the guidance gets visibilities below 1-2 miles. So we will keep patchy fog and drizzle in the forecast for now, but we are not expecting widespread dense fog at this time. && .LONG TERM /TUESDAY THROUGH SUNDAY/... A mid level low is forecast to meander over upper Ontario and vicinity during the mid week period before shifting eastward over Quebec and eventually Atlantic Canada during the weekend. An initial mid level trough axis is expected to pass over our region around Wednesday night with a secondary axis anticipated around Saturday night. The pattern should be rather unsettled with the best chance for dry weather extending from Wednesday night into early Friday. We are expecting Tuesday to begin with a low overcast in much of eastern Pennsylvania, New Jersey and the upper Delmarva. Some fog is anticipated at that time, as well. A southeasterly surface flow on Tuesday should keep the clouds from lifting and breaking quickly. As a result, we are forecasting a mostly cloudy day along with a chance of showers and perhaps some thunder. High temperatures should be in the 60s up north and right along the coast. Maximum readings are expected to be in the lower 70s from the Philadelphia metropolitan area southward. The most likely area for a substantial break in the cloud cover is southern Delaware and the adjacent counties of northeastern Maryland. There the highs could reach the upper 70s. A weak surface low is forecast to pass off the middle Atlantic coast on Tuesday night with partial clearing possible in its wake for Wednesday. However, a cold front approaching from the northwest along with some marginal instability may result in the development of showers and thunderstorms mainly during the afternoon and evening hours. The best chance for precipitation at that time will be in eastern Pennsylvania and northern New Jersey. The cold front is expected to pass through our region on Wednesday night followed by dry weather and seasonable temperatures for Thursday and Thursday night. Another cold front is anticipated to approach from the northwest on Friday and it should pass slowly through our region on Friday night and Saturday. We will mention another chance for showers and thunderstorms in advance of the front. The southward progress of the front over the weekend is a low confidence forecast. The models differ on how progressive the boundary will be. As a result, we will keep a chance or slight chance of showers into Sunday. && .AVIATION /15Z MONDAY THROUGH FRIDAY/...
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The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. An easterly flow will continue through today across the area as low pressure moves out to sea, and high pressure noses down the eastern seaboard across the area. This will keep plenty of moisture low level moisture across the area through today. IFR/MVFR conditions are expected to continue through much of the day. However, there is a chance for some improvement this afternoon into this evening. Even if this improvement does occur, clouds are expected to fill back in overnight with low clouds and fog developing again, leading to IFR conditions overnight. There is also the possibility for patchy drizzle to develop overnight as well. OUTLOOK... Tuesday...IFR conditions in the morning improving to MVFR and VFR during the course of the day. A chance of showers and thunderstorms developing. Tuesday night and Wednesday morning...Conditions may lower back to MVFR and IFR for a time. Wednesday afternoon and evening...Mainly VFR with a chance of showers and thunderstorms. Wednesday night through Friday morning...Mainly VFR. Friday afternoon...Mainly VFR with a chance of showers and thunderstorms.
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&& .MARINE... A Small Craft Advisory flag has been issued for the Delaware and southern New jersey coastal waters for today. Seas at buoy 44009 have increased to around 5 ft and the sea seen via webcam near ACY looks quite choppy. We will keep the flag for the daytime hours, although this may be longer than necessary. Small Craft Advisory continues across the northern half of the Atlantic Coastal waters as seas are being observed around 5 feet and winds will remain gusty to around 25 knots. We have extended the flag for the remainder of the day. OUTLOOK... Tuesday through Wednesday...Wind speeds and wave heights are forecast to remain below the Small Craft Advisory criteria. However, some fog is possible on the waters. Wednesday night through Friday...No marine headlines are anticipated. RIP CURRENTS... The potential for the development of dangerous rip currents is low for today. && .TIDES/COASTAL FLOODING... Tidal departures of around 1 foot are expected again tonight for coastal areas of New Jersey and Delaware and areas along Delaware Bay. These tidal departures would lead to another round of minor coastal flooding for tonight`s high tide. Therefore we`ve issued a Coastal Flood Advisory for tonight. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...Coastal Flood Advisory from 10 PM this evening to 4 AM EDT Tuesday for NJZ012>014-020>027. DE...Coastal Flood Advisory from 10 PM this evening to 4 AM EDT Tuesday for DEZ002>004. MD...None. MARINE...Small Craft Advisory until 6 PM EDT this evening for ANZ450>455. && $$ Synopsis...Iovino Near Term...Robertson/PO Short Term...Robertson Long Term...Iovino Aviation...Iovino/Robertson/PO Marine...Iovino/Robertson/PO Tides/Coastal Flooding... is the U.S. government's official web portal to all federal, state and local government web resources and services.