Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 210354 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 1154 PM EDT Fri Oct 20 2017 .SYNOPSIS... High pressure centered over the area tonight will move offshore late Saturday but continue to influence our weather into Monday. A cold front approaching from the west is expected to arrive on Tuesday night. Low pressure is anticipated to develop over New England and its coastal waters late in the week as another area of high pressure noses into our region from the southwest and south. && .NEAR TERM /THROUGH SATURDAY/...
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Overnight...Clear or mostly clear. Calm or light wind. Patchy fog possible in some of the river valleys toward dawn. Saturday...Sunny. Light wind becoming southeast during the afternoon. High temps similar to or a couple of degrees warmer than ydy. Using a 50 50 blend of the 00z/21 GFS/NAM. Max temps about 10 to 15F above normal.
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&& .SHORT TERM /SATURDAY NIGHT/...
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Clear and nearly calm but patchy fog may form toward dawn Sunday, especially se of I95. The 330 am fcst will be a 50 50 blend of the GFS/NAM MOS with countryside temps lowered a couple of degrees below the blended guidance.
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&& .LONG TERM /SUNDAY THROUGH FRIDAY/... The axis of the mid level ridge is forecast to pass overhead on Saturday night. Meanwhile, a sharp trough is expected to be located over the middle part of the country during the weekend. A mid level low is anticipated to develop over the south central states on Sunday. A re-enforcing mid level trough is expected to drop over the eastern states for the mid week period. The trough is forecast to pull the mid level low east then northeastward and over our region on Tuesday. The long wave trough should begin to lift to our northeast late in the week. At the surface, high pressure moving out to sea should maintain some influence over our weather for Sunday and Monday with no precipitation expected. However, there should be an increase in cloud cover during the period. A return southerly flow may result in the development of low clouds and perhaps some fog from late Sunday night into Monday morning. The end of our current dry spell is anticipated to arrive on Monday night. Showers ahead of an approaching cold front should begin to move into our region at that time. We are expecting an increasing chance of showers on Tuesday. As the surface cold front nears our area and as the remnants of the mid level low pass overhead there should be added lift. As a result, there may be a period of moderate and perhaps briefly heavy rain along with isolated thunderstorms on Tuesday afternoon and into Tuesday evening. There is the potential for a half inch to an inch of rain in spots. The cold front and the precipitation associated with it should pass off the coast on Tuesday night. Low pressure is forecast to develop along the departing front off the Middle Atlantic coast. The low is expected to lift over New England and its coastal waters late in the week. The system may push clouds and showers back into our region from the northeast for the period from Wednesday night into Thursday night. Otherwise, surface high pressure will likely try to build into our region from the southwest and south. Daytime temperatures will remain about 10 degrees above normal on Sunday, Monday and Tuesday. Readings are forecast to drop back to near normal levels for late October on Thursday, Friday and Saturday. && .AVIATION /04Z SATURDAY THROUGH WEDNESDAY/...
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The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Through Saturday...VFR with a few cirrus, especially afternoon. Light northwest wind trending northeast later this Saturday morning and then southeast during this Saturday afternoon. Saturday night...VFR with some cirrus. The IFR st/fog may develop southeast of I-95 toward dawn Sunday. OUTLOOK... Sunday...Mainly VFR. Sunday night and Monday...Low clouds and fog are possible from 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 afternoon and Tuesday evening, along with a south wind gusting around 25 to 30 MPH. Wednesday...Conditions improving to VFR.
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&& .MARINE...
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Winds and seas well below SCA criteria through Saturday night. Light NW winds 5-10 kt over the waters will veer over the next 24 hours, becoming N overnight, E around midday Saturday and then S-SE late in the day and Saturday night. Seas in our coastal waters of 2-3 ft this evening will settle closer to 2 ft Saturday and Saturday night. Fog may develop on the coastal waters toward dawn dawn Sunday. OUTLOOK... Sunday through Monday night...No marine headlines are anticipated. Tuesday and Tuesday evening...A Small Craft Advisory may be need for southerly wind gusts of 25 to 30 knots. Waves on our ocean waters may build to 6 to 8 feet. Late Tuesday night and Wednesday...A Small Craft Advisory may be needed on our ocean waters for wave heights of 5 to 6 feet, even as the wind becomes westerly and diminishes to 10 to 15 knots.
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&& .FIRE WEATHER...
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RH values are likely to drop to around 30% again Saturday afternoon but light winds will limit the risk for a rapid rate of spread of any wildfires.
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&& .EQUIPMENT...
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KMPO METAR had been erroneously reporting -RA in clear skies starting this past afternoon. The Present Weather Sensor on the ASOS has been temporarily turned off until technicians are able to fix the issue this weekend. 44091 buoy drifted away from its mooring and was recovered. Its rts date is unknown.
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&& .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...None. && $$ Synopsis...Iovino Near Term...Drag/Klein 1154 Short Term...Drag/Gaines 1154 Long Term...Iovino Aviation...Drag/Iovino/Klein 1154 Marine...Drag/Iovino/Klein 1154 Equipment...1154

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