Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 221922 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 322 PM EDT Sun Oct 22 2017 .SYNOPSIS...
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High pressure located over eastern Canada and the western North Atlantic this afternoon will continue to drift farther out to sea during tonight and Monday. A cold front is forecast to approach from the west on Tuesday and it should pass through our region on Tuesday night. Low pressure is expected to develop along the front and it should pass over or near New England and southeastern Canada on Wednesday and Thursday. High pressure is anticipated to follow for Friday and Saturday. Another cold front may approach from the west on Sunday.
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&& .NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
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High pressure located over New England will continue to move northeast resulting in southeasterly flow to continue on the backside of the departing high. This will allow the moisture transport from the Atlantic to continue into the region. Low clouds and fog formation will be the main highlights overnight given the increased moisture and light winds. Unlike the last few nights, radiational cooling is not expected to be as aggressive so stuck close to MET/MAV guidance with lows in the 50`s.
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&& .SHORT TERM /6 AM MONDAY MORNING THROUGH 6 PM MONDAY/...
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A strong cold front will continue to advance eastward in wake of the departing high toward our region. This will allows a strong southerly to southeasterly moisture flow to continue. Fog and low clouds will persist throughout a good portion of the day, likely even slower to burn off than today. However, sunshine will likely break through at times in the afternoon tomorrow. Several models are also hinting at a couple of passing light showers across northern NJ and Eastern PA, so have continued with slight and low chances of showers. The majority of the steadier showers will hold off till the evening. The low clouds and fog may keep temperatures down a bit from what the MOS guidance has, particularly for northern NJ and PA. Still, highs should reach the mid 70`s in Delmarva and 60`s to low 70`s in the Lehigh Valley, Poconos and northern NJ.
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&& .LONG TERM /MONDAY NIGHT THROUGH SUNDAY/...
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A deepening mid level long wave trough will be in the process of settling over the eastern half of the country on Monday night and Tuesday. A negative tilt short wave is forecast to lift northeastward on the front side of the trough and its axis should pass over our region early on Tuesday. A slow moving cold front is expected to extend from the eastern Great Lakes to the eastern Gulf of Mexico on Monday evening. The boundary will move eastward and it should arrive in our region late on Tuesday. The slow forward progress of the front will allow it ample time to tap into Gulf moisture and eventually into some Atlantic moisture as it approaches and moves into our region. As a result, we are anticipating moderate to heavy rainfall at times. We have increased our rainfall projections mainly into the 1 to 2 inch range with locally higher amounts possible. Due to the recent dry spell, we are not expecting any flooding issues other than some poor drainage flooding. Leaf-clogged drains will enhance the possibility of ponding of water on roadways. We remain under a moderate risk for severe weather on Tuesday. The negative tilt short wave and the approaching cold front suggest the potential for a QLCS set-up. If a narrow convection line develops, it should work its way from west to east across our region from late Monday night into early Tuesday afternoon. Moderate to heavy rain is anticipated to linger near the coast into Tuesday evening until the front begins to make its way out to sea. The cold front and its associated cloud cover and precipitation will continue to move slowly eastward on Wednesday as a wave of low pressure develops along the boundary and moves up into New England and vicinity. The axis of the mid level long wave trough is forecast to pass overhead on Thursday and it should finally kick the surface system well to our east. Surface high pressure is expected to begin building into our region from the southwest and south on Thursday before it slides out over the ocean on Friday and Saturday. We should experience some clear for late in the week and the early part of the weekend. The model guidance differs in handling the timing of our next cold front. It appears as though it will arrive around Sunday, so we will indicate a chance of showers at that time. Daytime temperatures should be near 10 degrees above normal on Tuesday. Readings are forecast to drop back near normal on Wednesday. Slightly below normal temperatures are anticipated for Thursday with readings rebounding to normal or slight above normal for Friday and the weekend.
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&& .AVIATION /19Z SUNDAY THROUGH FRIDAY/...
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The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. VFR through this evening. Low clouds and stratus are likely to form and at least form a broken ceiling overnight around the IFR level at all TAF sites. Visibilities will likely fall as well with fog formation toward sunrise, with restrictions of IFR or locally LIFR right likely around sunrise. It will likely take till mid and late morning to see lifting ceilings and visibilities. The 18z TAFS featured general trends for the overnight hours and the day Monday. Given higher than normal uncertainty, the timing and exact degree of restrictions will likely need to be fined-tuned with the upcoming 00z/06z TAFS. OUTLOOK... Monday night through Tuesday night...Conditions lowering to MVFR and IFR in showers. Isolated thunderstorms and moderate to heavy rain are possible, along with a south wind gusting around 25 or 30 knots. Wednesday...A chance of morning showers with conditions improving to VFR. Wednesday night through Friday...Mainly VFR.
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&& .MARINE...
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Wave heights look to be in a fairly stable state of around two feet through tomorrow morning then build in the afternoon but stay under four feet. Winds will also be under 10 knots into Monday then increase to around 10 knots during the afternoon. Some patchy fog and/or low clouds are possible overnight and on Monday which may limit visibilities in a few locations. OUTLOOK... Monday night and Tuesday...A Small Craft Advisory is in effect for southerly wind gusts near 30 knots. Localized gale force gusts are possible on Tuesday. Waves on our ocean waters should build to 7 to 10 feet. Tuesday evening...A Small Craft Advisory may need for southerly wind gusts near 30 knots. Waves on our ocean waters are forecast to be 7 to 10 feet. Late Tuesday night through Thursday night...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. Friday...No marine headlines are anticipated.
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&& .EQUIPMENT...
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44091 buoy drifted away from its mooring and has since been recovered. Its return to service date is still unknown, though we`ll try to have an answer Monday afternoon. Weather observations at KVAY may be incomplete for the remainder of the day.
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&& .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...Small Craft Advisory from midnight Monday night to 6 PM EDT Tuesday for ANZ430-431-450>455. && $$ Synopsis...Iovino Near Term...Gaines Short Term...Gaines Long Term...Iovino Aviation...Gaines/Iovino Marine...Gaines/Iovino Equipment...Staff

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