Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 230147 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 947 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/...
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The mid/upper low affecting the area will continue to sink southward tonight, but our area will remain on the northern side. Cool an damp conditions will continue through the night. Showers will dissipate from north to south overnight, and clouds may begin to thin from north to south as well through the overnight hours. Depending on how much thinning of the clouds occurs, some fog could develop overnight light winds expected.
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&& .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 /01Z MONDAY THROUGH FRIDAY/...
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The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. VFR conditions are currently in place across all TAF sites this evening, and scattered showers will dissipate from north to south this evening and overnight. There is the potential for some fog development overnight into Monday morning if clouds thin out enough. We`ve introduced some light fog for all TAF sites, with the thickest potential at RDG. Any fog should lift and dissipate after sunrise Monday, and a return to VFR is expected. Scattered showers could again develop during the day Monday. 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.
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&& .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/Robertson Short Term...Gaines Long Term...Johnson Aviation...Gaines/Johnson/Robertson Marine...Gaines/Johnson Climate...

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