Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 210828 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 328 AM EST Tue Feb 21 2017 .SYNOPSIS... High pressure centered over southern Quebec early this morning will slide southeastward and it should pass off the coasts of New England and Nova Scotia late today. The high is then forecast to progress southward to the waters off the Middle Atlantic Coast for Wednesday and Thursday. The high is expected to begin losing its influence over our weather on Friday as a cold front approaches from the west. The cold front is anticipated to arrive on Saturday afternoon followed by another area of high pressure for Sunday and Monday. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Mid-level ridge traversing our region today begins to attenuate, in response to shortwave energy approaching the Appalachians late this afternoon. This will lead to an increasingly west flow aloft, allowing mid and upper level moisture to overspread the area. Expect increasing cloudiness, but the sun will manage to make it through. As high pressure moves to the south coast of New England, winds will veer from easterly this morning to southerly by this afternoon. As modest warm air advection aloft gets underway, an inversion will develop around 900 hPa, which will limit mixing. In addition, the low-level air mass will moisten, due to the increasing maritime influence. Both of these factors, in addition to increased clouds, will limit the maximum temperature potential. As such, went more in line w/ guidance, generally a MAV/MET blend. Also checked this against EC 18Z 2-meter temperatures. Grids reflect warmer temperatures in the PHL-TTN urban corridor and interior Delmarva, trending down southeastward to the coast, particularly the barrier islands. Overall, temperatures still running 5 to 10 degrees above normal. Winds will gust 10 to 15 knots at times late this morning into the afternoon. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM WEDNESDAY/... A diffuse shortwave will traverse our region overnight, while its associated cold front essentially washes out (frontolysis) across the Appalachians. A southerly flow will be maintained across the area, but model cross sections indicate low-level dry air remaining, with saturation confined closer to I-80. Aloft, weak mid-level positive vorticity advection occurs, within the left-rear quadrant of the upper-level jet, along with some weak isentropic lift. The lifting mechanisms are generally diffuse and weak, so the added moisture and terrain forcing, generally northward of I-78, leads to the greatest chance for light precipitation across this area. Thus, highest PoPs (chance) were focused closer to I-80, with lower (slight chance) Pops south to I-78. Low temperatures around 10 degrees above average across our region. && .LONG TERM /WEDNESDAY THROUGH MONDAY/... The period from Wednesday through Friday is expected to feature unseasonably mild weather as high pressure over the western North Atlantic maintains a southerly surface flow in our region. It appears as though Thursday will be the warmest of the three days with maximum temperatures running about 25 degrees above normal. The record high temperatures for Wednesday, Thursday and Friday are listed below in the climate section of this product. An impulse traveling in the westerly mid level flow is forecast to pass overhead and to our east on Wednesday morning. We are anticipating a mostly to partly cloudy sky for Wednesday. A partly cloudy sky (mainly cirrus) is expected for Wednesday night into Thursday morning. An increase in low level moisture may result in patchy fog at that time. Another mid level impulse is forecast to approach from the west late on Thursday and it should pass over our region late on Thursday night. The feature is expected to bring an increase in cloud cover along with a chance of rain showers. The chance of rain showers may linger into Friday, especially in parts of eastern Pennsylvania and central and northern New Jersey. A strong cold front is expected to extend from the Great Lakes to the Texas Gulf Coast late on Friday. The boundary will continue to progress eastward and it should pass through our region on Saturday afternoon. We will continue to mention an increasing potential for rain showers on Friday night into Saturday along with a chance of thunderstorms on Saturday afternoon. High pressure and dry weather are anticipated to follow the cold front for Sunday and Monday. Temperatures should be considerably colder than those ahead of the front. However, readings are forecast to remain slightly above normal at that time. && .AVIATION /09Z TUESDAY THROUGH SATURDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Today...VFR. Easterly winds early this morning will veer to the south-southeast from late morning into the afternoon, generally less than 10 knots with some occasional gusts to 15 knots. Tonight...MVFR ceilings may develop toward daybreak at ABE and RDG, with highest confidence at ABE. As a result, we have inserted a TEMPO group at ABE to reflect this. Otherwise, VFR. OVC100 ceilings across the area. At TTN, PNE, PHL, and ILG, SCT050 ceilings possible toward day break. Winds will maintain a southerly direction, generally less than 10 knots. OUTLOOK... Wednesday...Mainly VFR. Wednesday night and Thursday morning...Mainly VFR with patchy fog possibly lowering conditions to MVFR or IFR for a time. Thursday...Mainly VFR. Thursday night and Friday...Mainly VFR. However, there is a chance of showers which may result in a period of MVFR or IFR conditions. Friday night and Saturday...An increasing potential for showers along with MVFR and IFR conditions. Also, there is a chance of thunderstorms on Saturday afternoon. && .MARINE... Today and tonight...High pressure will continue to move slowly eastward over the northwest Atlantic. Winds initially out of the east this morning will veer to the southeast this afternoon, and continue veering to the south tonight. On the ocean waters, winds less than 20 knots, and seas generally 1-3 feet through the period. On the Delware Bay, southeast wind gusts around 20 knots along with seas of 1-3 feet are expected this afternoon into this evening. Sub-SCA conditions across the coastal waters through the period. OUTLOOK... Wednesday through Friday night...No marine headlines are anticipated. Saturday...Southerly wind gusts around 25 knots are possible. Wave heights on the coastal waters off Delaware and New Jersey may build to 5 or 6 feet. && .CLIMATE... Records for late this week. Most of these records will probably remain intact, but there appears to be opportunity for approaching within 2 degrees at PHL/ABE/TTN/MPO on 1 to 3 days. Wednesday 2/22 Thursday 2/23 Friday 2/24 ACY 68-1991 72-1985 75-1985 PHL 68-1997/1974 75-1874 74-1985 ILG 69-1997/1974 72-1985 78-1985 ABE 68-1974 71-1985 76-1985 TTN 66-1997 74-1874 74-1985 GED 72-1997 no data no data RDG 70-1974 72/1932/1922 77-1985 MPO 56-1997 60-1977 60-1984 && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...None. && $$ Synopsis...Iovino Near Term...Franck Short Term...Franck Long Term...Iovino Aviation...Franck/Iovino Marine...Franck/Iovino Climate...Staff is the U.S. government's official web portal to all federal, state and local government web resources and services.