Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 222307 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 707 PM EDT SUN MAY 22 2016 .SYNOPSIS... A low is expected to develop off the coast of North Carolina and then slowly drift northeast, lingering just offshore of our region through Tuesday. A ridge will build over our region by mid week. The ridge will slowly shift east through the remainder of the week. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/... A upper low pressure system and an associated low pressure trough will continue moving southeast into Virgina tonight. scattered showers are currently located across in the Delmarva and Eastern PA. However, a gradual decrease is expected as the upper level low pressure moves south of us overnight. Cloud cover will likely keep temperatures a degree or warmer than the met/mav guidance in the low and mid 50`s. Some patchy fog could occur as well around sunrise with light winds and residual moisture in place. A hindrance for fog formation will be a mid to high cloud deck which can prevent the formation of radiational fog around sunrise. && .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 /23Z SUNDAY THROUGH FRIDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Tonight...VFR ceilings outside of KMIV and KACY, possible window from 09-13z Monday for some patchy fog at all sites with lower ceilings and VSBYS. Highest chances for fog are at KRDG and KMIV. KMIV and KACY are likely to hang on to IFR/MVFR into the early evening hours. Lingering showers tonight should slowly decrease in coverage this evening. Outlook... 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. && .CLIMATE... We`ve recalculated the projected monthly temperature based on our forecast and we`re still holding to a substantial warmup (summerlike by Friday), lowering the average temperature departure by about 3 degrees from where we were through the 21st...still below normal for the month at Philadelphia. A backdoor cold frontal intrusion this weekend as proposed by the GFS would leaves us cooler for the month, than now expected and projected. Rainfall through 7 pm today (5.03) has raised Philadelphia`s month of May ranking to 22nd wettest, dating back to 1872. Atlantic City`s 4.61 total makes this so far, the 25th wettest May dating back to 1874. Corrected por PHl and 7 PM monthly amounts both locations. && .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...Johnson Near Term...Gaines Short Term...Gaines Long Term...Johnson Aviation...Gaines/Johnson Marine...Gaines/Johnson Climate...707P is the U.S. government's official web portal to all federal, state and local government web resources and services.