Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 220121 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 921 PM EDT Sat Oct 21 2017 .SYNOPSIS... High pressure will shift offshore on Sunday and Monday. A strong cold front is forecast to move across our region Tuesday night. Low pressure is expected to develop along the front and it should be located over or near New England and southeastern Canada on Wednesday and Thursday. High pressure is anticipated to follow for Friday and Saturday. && .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/... Despite the cirrus overhead, light/calm winds and low enough dew points have allowed the temperatures to quickly cool this evening across the entire area. Some updates were issued earlier to keep the temperatures more current based on the faster drop. The 930 PM update adjusted these again, however low temperatures were not changed much at this time especially since the dew points have now come up more across much of the region. Otherwise, an upper air analysis this evening shows a ridge axis near the East Coast. A 250 mb jet is positioned from the Southern Plains to the Midwest with a second segment from the Mid- Mississippi Valley to north of the Great Lakes. At the surface, high pressure is centered near the Delmarva coast. High pressure at the surface will slowly move offshore through the overnight. Satellite imagery shows quite a bit of cirrus streaming northward all the way from the Gulf Coast states this evening, and this is expected to continue through the overnight although it may thin at times. The sky cover was adjusted upward a bit more. The presence of the cirrus, especially if it is thick enough, should limit fog development late tonight despite the dew points rebounding. Given the light to calm winds at the surface though, we kept some patchy fog especially for parts of northeastern Pennsylvania and northwestern New Jersey (valleys). && .SHORT TERM /6 AM SUNDAY MORNING THROUGH 6 PM SUNDAY/... Winds will still be light but start to turn from out of the southeast on the backside of the high. This will lead to a further increase of moisture and warm air into the region. The overall moisture transport looks slow, so we should be able to get one more mostly sunny day Sunday. Temperatures will warm fairly rapidly as well into the mid and upper 70`s, perhaps a degree or two cooler than today (Saturday) based on modeled 925 mb temperatures. && .LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/... The surface high will be well off the coast on Sunday night and Monday. The return flow on the back side of the high is expected to bring increasing moisture into our region. As a result, we continue to anticipate low clouds and patchy fog for late Sunday night into Monday morning. The axis of the mid level ridge is forecast to be located along the east coast on Sunday evening. A mid level low is expected to be centered over Missouri at that time. As the ridge moves out to sea, a re-enforcing long wave trough should begin to drop over the Mississippi River Valley. The mid level low is anticipated to fill with its remnants being drawn up and over our region late on Monday night. The long wave trough is forecast to influence the eastern states during the mid week period before it lifts to the northeast. The surface cold front is expected to extend from the Great Lakes to the central Gulf Coast on Sunday night. The feature should already be tapping into gulf moisture at that time. As the remnants of the mid level low pass overhead and as the cold front approaches, there will be an increasing chance of showers in our region from Monday night into Tuesday. Enhanced lift from late Monday night into Tuesday will likely result in period of moderate to heavy rain along with a chance of thunder. It appears as though rainfall totals will favor the 0.25 to 1.00 inch range. The cyclonic flow aloft along with the slowly departing cold front and surface low pressure over or near New England should keep clouds and a low or slight chance of showers in our region during the mid week period. High pressure is expected to bring some clearing for Friday and Saturday. Daytime temperatures will remain about 10 degrees above normal on Monday and Tuesday. Readings are forecast to drop back to more typical levels for late October during the period from Wednesday through Saturday. && .AVIATION /01Z SUNDAY THROUGH THURSDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Overnight...VFR with clouds around 25000 feet. Light and variable to calm winds. Sunday...VFR. Light and variable to calm winds, becoming southeasterly less than 10 knots. Any low cloud development late in the afternoon however is anticipated to stay offshore. OUTLOOK... Sunday night and Monday...Low clouds and fog are possible mainly late Sunday night into Monday morning. Otherwise...mainly VFR. Monday night through Tuesday night...Conditions lowering to MVFR and IFR in showers. Isolated thunderstorms and moderate to heavy rain are possible on Tuesday, along with a south wind gusting around 25 or 30 knots. Wednesday...Conditions improving to VFR. Wednesday night and Thursday...Mainly VFR. && .MARINE... Wave heights will be in a fairly stable state of around two feet through Sunday. Southerly winds will be 10 knots or less through Sunday. OUTLOOK... Sunday night through Monday night...No marine headlines are anticipated. Tuesday and Tuesday evening...A Small Craft Advisory may be need for southerly wind gusts near 30 knots. Waves on our ocean waters may build to 7 to 10 feet. Late Tuesday night through Thursday...A Small Craft Advisory may be needed on our ocean waters for wave heights of 5 to 6 feet, even as the wind becomes west to northwest around 10 to 20 knots. && .EQUIPMENT... 44091 buoy drifted away from its mooring and has since been recovered. Its return to service date is still unknown. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...None. && $$ Synopsis...Iovino Near Term...Gorse Short Term...Gaines Long Term...Iovino Aviation...Gorse/Iovino Marine...Gaines/Iovino Equipment... is the U.S. government's official web portal to all federal, state and local government web resources and services.