Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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179 FXUS61 KPHI 030905 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 405 AM EST Sat Dec 3 2016 .SYNOPSIS... Strong low pressure near Newfoundland will move east today with high pressure following into the northeast United States on Sunday. A weak warm front approaches from the west Sunday night, followed by high pressure Monday. Low pressure systems in south central Canada and the lower Mississippi Valley on Tuesday will eventually consolidate into a large storm over southeast Canada by early Friday. The coldest air of the season so far, is likely to follow on blustery westerly winds. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... The weather pattern for today features surface low pressure and a trof aloft over the Canadian maritimes and surface high pressure with ridging aloft over the Midwest. A fairly strong pressure gradient between the two systems will result in continued gusty northwest winds over the area today. Low level moisture off the lower Great Lakes should maintain considerable cloudiness today, especially north and west of PHL. We also extended a chance of flurries or sprinkles through much of the day for higher elevations in the Poconos. By late in the day the pressure gradient should begin to relax as the whole pattern shifts east and the center of high pressure approaches from the Ohio Valley. Max temps this afternoon should be similar to today. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SUNDAY/... The surface high pressure will continue slowly eastward tonight toward the mid-Atlantic region. Winds above the surface will continue from the NW but should be diminishing. This plus the usual nocturnal decoupling will result in lighter winds overnight. Somewhat less low-level moisture and cloudiness is also expected which combined with the lighter winds should result in overnight min temps a few degrees cooler than early this morning. && .LONG TERM /SUNDAY THROUGH FRIDAY/... 500MB: A short wave in the Great Lakes weakens as it moves across the northeast early Monday. A short wave in Texas Monday afternoon weakens as it opens up northeastward toward the mid Atlantic states Tuesday. A larger scale trough in the Plains states on Wednesday strengthens as it crosses the northeast USA Friday. Temperatures: Calendar day averages will run above normal daily Sunday through Thursday and then cool below normal next Friday. Forecast basis: Unless otherwise noted, a 50 50 blend of the 00z/3 GFS/NAM MOS guidance Sunday-Monday, thereafter the 00z/3 GFS MEXMOS Monday night, and then the 04z/3 WPC guidance Tuesday-Friday, at times blended with the 00z/3 GFS MEXMOS guidance. The dailies... This will be an active pattern for most of the week. Sunday...Partly sunny, Mixed sc and ci. Confidence: well above average. Sunday night and early Monday morning prior to 9 am...Cloudy with a 2 to 7 hour period of pcpn (mainly midnight to 8 am). Rain Delmarva, and a mix of r/s vcnty PHl-ACY and generally all snow near and N of I-78. A small snow accumulation is anticipated in the north, since qpf should generally be under one tenth inch. No matter, a slippery covering of half an inch to an inch is expected on all untreated surfaces (nighttime) for ne PA into nw NJ. Fcst temps may be two degrees too cool and that could alter-lower any accum potential s of I-78. Light wind. Confidence: Above average. Monday late morning through Monday night...becoming mostly clear with light wind. Confidence: Average. since we`re not sure how much clearing there will be or how extensive the formation of fog- stratus Monday night. Tuesday...becoming cloudy with rain spreading northeastward and maybe a little snow on the northern fringe as low pressure moves northeast from the southern states becomes. Most of the rain will be at night. Confidence: average. Wednesday...Probably cloudy and dreary with moisture remains of the eastward departing low pressure. Periods of rain/drizzle. Confidence: below average on details. Thursday...A strong CFP expected and it should clear out the moisture but timing of this clean out is very uncertain due tomodel disparity. There is a chance the EC will be correct in its expectation of a frontal wave on Thursday. Confidence: average. Thursday night...turning noticeably colder and blustery. Confidence: average. Friday...Blustery and cold with partly cloudy skies (flurries in the Poconos?). Confidence: well above average. && .AVIATION /09Z SATURDAY THROUGH WEDNESDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. VFR conditions are expected through tonight across the area. Ceilings BKN-OVC 040-050 are expected to continue much of the day today for PHL vicinity and northwest owing to low-level moisture and clouds from the lower Great Lakes. Surface winds have been somewhat gusty through the night and gusts will increase after sunrise with heating/mixing. Gusts should diminish around sunset with light NW winds continuing through this evening. OUTLOOK... Sunday...VFR sct-bkn aoa 4000 ft. NW winds 5-10 KT may gust 15 kt. Sunday night and Monday...Sub-VFR possible, mainly Sunday night (05z-11z/4) KABE/KRDG where a few hours of snow are likely and generally rain or snow mixed with rain elsewhere. Conditions improve by midday Monday afternoon. light south wind turns to northwest Monday afternoon and may gust 15 kt. Monday night...VFR but with small potential IFR st/fog late. light northwest wind turns north late. Tuesday through Wednesday...Periods of MVFR/IFR conditions, mainly late Tuesday into Wednesday. Generally rain/drizzle. northeast winds...gusty to 20 or 25 kt coast late Tuesday becoming light Wednesday. && .MARINE... A gale warning remains in effect for coastal waters and the lower Delaware Bay through this afternoon. NW winds will continue to gust up to 35 kts for much of the day before diminishing late this afternoon. The NW flow pattern leads to waves 4 to 5 feet in the coastal waters well offshore (20 nm) and 2 to 4 feet over the lower Delware Bay. Winds and seas will diminish tonight but a SCA will likely be needed at least for a while this evening. OUTLOOK... Sunday through Monday night. Generally tranquil conditions and no marine headlines. Tuesday through Wednesday...Low pressure off the mid Atlantic coast could produce a short period of easterly gales. Seas build to 5-7 feet on the ocean. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...Gale Warning until 6 PM EST this evening for ANZ431-450>455. Small Craft Advisory until 6 PM EST this evening for ANZ430. && $$ Synopsis...Drag 405 Near Term...AMC 405 Short Term...AMC 405 Long Term...Drag 405 Aviation...AMC/Drag 405 Marine...AMC/Drag 405

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