Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 230349 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 1149 PM EDT SUN MAY 22 2016 .SYNOPSIS... Low pressure continues to develop off of the North Carolina coast overnight, which will then slowly drift northeastward and linger just offshore of our region through Tuesday. A ridge will build over our region by mid week, then it will slowly shift eastward through the remainder of the week. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/... A developing closed low centered to our southwest will pivot southeastward overnight. This places our area on the northern side with much of the forcing being pulled to our south. As a result, some lingering showers across mainly our southern zones should be pushed farther south. Some showers off the central New Jersey coast are tending to weaken as they slowly move westward. Otherwise, breaks in the cloud cover continues to occur and this is already leading to some shallow fog development in open areas such as fields. This is expected to continue, however the extent of the fog will depend on the coverage of mid/high clouds. && .SHORT TERM /6 AM MONDAY MORNING THROUGH 6 PM MONDAY/... A low pressure system will start the day to our southeast and move northeast toward Cape Cod by nighttime. While the system will be offshore, daytime heating will result in some instability by the afternoon hours. This will likely result in another round of scattered showers forming and even some thunderstorms with CAPE values of a few hundred J/KG. The highest chances look to be across Eastern PA where the terrain may help out a little as well. Temperatures should rise into the low and mid 70`s for the region tomorrow. && .LONG TERM /MONDAY NIGHT THROUGH SUNDAY/... Tuesday...the upper level low will linger over the northeastern U.S. for one more day before lifting further northeast. As such, should see any lingering showers across the region taper off by the evening. A modest warming trend is expected going into Tuesday resulting in temperatures once again near normal. Wednesday and Thursday...Upper level ridge will shift east, with the ridge axis over our region by Thursday morning. However, unlike previous model runs, the 12z ECMWF and GFS now show the center of the high much further south. As such, though there should be a lull in rain chances on Wednesday, rain chances will increase once again on Thursday, primarily for locations expected to be west of the ridge axis (Generally E Central PA and NW NJ). Of more certainty is that the region will have a very noticeable warming trend, with 80s expected across much of the region both days. Friday through Sunday...The GFS has poor run to run consistency through this period, as it now shows a backdoor cold front arriving in the region by Friday. If this scenario is correct, persistent onshore flow could result in temperatures well below normal especially Saturday and Sunday, and generally light and steady precip through much of the period. For now though, have not included this in the forecast, not only due to the poor run to run consistency, but also because it seems an unlikely pattern for late May that a cold front would be able to push this far south under an upper level ridge. Even with models and ensemble members that show the ridge lingering over the region, should still see chances for showers and thunderstorms through the weekend as the region could be on the periphery of the ridge. && .AVIATION /04Z MONDAY THROUGH FRIDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Overnight...VFR overall as some lingering showers have shifted south of KMIV. Some fog development is expected, especially where the clouds thin out more. Some light fog has been included for all TAF sites, with the lowest restriction potential at KRDG. Light winds. Monday...MVFR/IFR visibility due to fog early for some terminals, otherwise VFR. Showers are expected to develop from about midday on, with the greatest chance from KTTN-KPNE/KPHL-KILG on westward. A few thunderstorms are anticipated as well. Given low coverage of thunderstorms it was not included in the TAF`s. Light and variable winds to start, becoming mostly northeast 4-8 knots then possibly becoming southeast toward evening. Outlook... Monday night...Local restrictions due to showers or a thunderstorm in the evening, however the showers should be diminishing through the night. Otherwise, mainly VFR. Light southerly winds overall, which if enough clearing takes place overnight then local fog should develop. Tuesday...Occasional MVFR conditions possible with showers and fog especially Tuesday morning. Wednesday and Thursday...VFR conditions likely. Small chance of MVFR conditions with showers and thunderstorms Thursday afternoon and evening. Friday...Intermittent MVFR conditions with rain showers possible. && .MARINE... SCA tonight through late tomorrow afternoon on the ocean. While winds will generally be northeasterly from 10-15 knots, seas will remaining around five feet through tomorrow afternoon on the ocean waters. Seas will likely be slower than wavewatch indicates coming down because of an easterly, onshore flow component in the wind direction. However, it is still expected that seas fall below five feet by days end on Monday. Outlook... Tuesday through Friday...winds and seas should stay below SCA criteria. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...Small Craft Advisory until 6 PM EDT Monday for ANZ452>455. Small Craft Advisory until 6 AM EDT Monday for ANZ450-451. && $$ Synopsis...Gorse/Johnson Near Term...Gorse Short Term...Gaines Long Term...Johnson Aviation...Gorse/Johnson/Robertson Marine...Gaines/Johnson is the U.S. government's official web portal to all federal, state and local government web resources and services.