Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 211620 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 1220 PM EDT Sat Oct 21 2017 .SYNOPSIS... High pressure centered over the area will move offshore later today but continue to influence our weather into Monday. A cold front approaching from the west is expected to approach the region on Tuesday. Low pressure will move along the front Tuesday night through Wednesday. Another low will affect the area Thursday before more high pressure builds in for the end of the week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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This afternoon...Sunny. Light wind becoming southeast during the afternoon. High temps a couple of degrees warmer than ydy. Looking at the ECMWF 925 mb modeled temperatures current thinking is that many locations in South Jersey and Delmarva come close or even reach 80. This matches up better than the cooler GFS values based on and old rule of the 10am temperature +10 degrees for the afternoon high. Looks very good for 75-79 virtually everywhere I95 corridor northwestward with support from the 00z/21 EC 2m temp fcst at 18z today. Effective sea breezing along the coast this aftn with water temps in the 60s...which are still significantly above normal for this time of year.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SUNDAY/... Clear and nearly calm but patchy fog may form toward dawn Sunday, especially se of I-95 where shallow moisture may increase enough for fog. Certainly a dewy late night early morning. The fcst is a 50 50 blend of the GFS/NAM MOS with countryside temps lowered 2-3F below the blended guidance and not much above this mornings mins...ranging from zero to +10 of normal depending on location. && .LONG TERM /SUNDAY THROUGH FRIDAY/... High pressure will still be in control of the weather for Sunday and Monday. Moisture will begin to arrive over the area however. This will result in some cloudiness and areas of fog for Sunday morning and increasing clouds for Monday. This will likely keep temperatures a few degrees cooler than Saturday, but readings will still be above normal for this part of October. A slow moving front and a upper trough will arrive from the Ohio Valley Tuesday-Wednesday. As it approaches, it slows, as low pressure will be deepening across the Tenn Valley area. The low will move along the front, just west of our region Tue-Tue night. This should bring a period of showers and gusty winds to the area. Pops are mostly in the likely/low categorical range at this time. QPF thru 12Z Wed. could reach 1/2 to 1 inch over much of the area. The latest ECMWF model does have a few spots closer to 2 inches of QPF however. Some of the guidance suggests that some tstms are also possible. We will not have tstms in the grids at this point, but will have to consider as we get closer to the event. Temperatures will be above normal Tuesday, but then fall to normal Wednesday as the front passes. Pops will decrease back to chc or slgt chc levels after the front moves offshore. There will still be a few sct showers around Thu as the upper low crosses the area. After that, high pressure with drier air is expected for Fri. Temperatures will be near normal for both of these days. && .AVIATION /16Z SATURDAY THROUGH WEDNESDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Through today...VFR with a few cirrus, especially this afternoon. Light north to northeast wind trending southeast during this afternoon. Tonight...VFR with some cirrus. The IFR st/fog may develop, especially southeast of I-95 toward dawn Sunday...also the river valleys in ne PA and nw NJ. OUTLOOK... Sunday...A little fog or stratus early...otherwise 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. && .MARINE... Winds and seas well below SCA criteria through tonight. Light N winds 5-10 kt will veer over the next 24 hours, becoming east around midday and then S-SE late today and tonight. Seas in our coastal waters of around 2 ft through tonight. OUTLOOK... Sunday thru Monday...Sub-SCA conditions with Fair weather. Monday night...SCA developing on the ocean. Chance of showers. Tue-Tue night...SCA conditions on the ocean and Del Bay. Showers. Wed-Wed night...SCA on the ocean. Sub-SCA on Del Bay. Chc showers. && .FIRE WEATHER... RH values are likely to drop to around 25% this afternoon but light winds will limit the risk for a rapid rate of spread of any wildfires. && .CLIMATE...
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The 77 we`re fcstg at KMPO would tie the record of 77 - 1959. **Top 5 warmest October on record for PHL and ABE and probably for rest of our forecast area** Our 330 AM forecast for the next 7 days, then adding the Day8-11 from FTPRHA GFS 2meter max/min temps yields the following projections for average temperature in October. PHL projects warmest October on record. The 64.7 degrees projected average is more than 7 degrees above the October 30 year avg of 57.5. The projected positive departure is the same as it is for the first 20 days of the month. Previous top 3 average temps for October in PHL 1. 64.5 2007 2. 63.5 1971 3. 62.7 1947 To drop out of the top 3 warmest the PHL avg would have to be 2 degrees lower than currently forecast. ABE 60.3 or nearly 8 degrees above the 30 year avg of 52.5. This is #2. 1. 60.8 2007 2. 60.3 2017 projected 3. 59.5 1984 4. 59.3 1947 5. 58.8 1971 THE VALUES BELOW ARE THE OCTOBER DEPARTURES FROM NORMAL THROUGH THE 20TH (YESTERDAY). PHL 7.2 ILG 7.1 ABE 8.5 MPO 6.9 RDG 7.7 TTN 7.8 ACY 7.0 55N 5.0 GED 6.5 The last two years in PHL ending 10/20/17 is the warmest in the period of record dating back to 1872...averaging more than 3 degrees above normal. Ditto Allentown, Wilmington being the warmest in their respective periods of record.
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&& .EQUIPMENT... 44091 buoy drifted away from its mooring and was recovered. Its return to service date is unknown. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...None. && $$ Synopsis...O`Hara Near Term...Drag/Gaines Short Term...Drag Long Term...O`Hara Aviation...Drag/O`Hara Marine...Drag/O`Hara Fire Weather... Climate... Equipment... is the U.S. government's official web portal to all federal, state and local government web resources and services.