Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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792 FXUS61 KPHI 221030 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 630 AM EDT Wed Mar 22 2017 .SYNOPSIS... Strong northwest flow will develop today in between the departing low to our northeast and approaching high from the northwest. The high will build across the east coast Wednesday night into Thursday, then shift offshore Thursday night. A warm front will lift to our northwest Friday, while a backdoor cold front pushes through the area Saturday. This front is forecast to stall near the southern portions of the area or just to our south into early next week. A couple of low pressure systems may form along the boundary and move eastward as well. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Cold front continues to work its way south through the region, and is through almost all of PA and northern NJ. Cold front should be off the Atlantic coast between 8am-10am. NW winds beginning to increase over the Poconos to 15-20 MPH with gusts up to 30 MPH. Some flurries and brief snow showers have developed in the wake of the cold front, aided by some upper level support from a strong shortwave. Accumulating snow is not expected. Will adjust hourly grids to account for latest surface obs. Otherwise, low pressure over eastern Quebec moves towards the Canadian Maritimes and intensifies today as high pressure over the Northern Plains digs towards the Great Lakes. This will result in a tight NW pressure gradient across the Northeast and into the Mid-Atlantic. Winds at the top of the mixed layer will range from 35-40 KT, and with strong CAA, most of those winds will mix down to the surface. NW winds should range from 20-30 MPH with 30-40 MPH gusts. Wind gusts should stay under Wind Advisory criteria. Meanwhile, a deep upper trough will dig into the Northeast U.S., and H8 temps will drop to -12C to -15C throughout the day today. Highs will be 15-20 degrees below normal, topping off in the low 20s in the Poconos, and in the low 30s for much of northern NJ. For SE PA and central and southern NJ, highs will be in the mid to upper 30s, and in SE MD and DE, highs will be in the low 40s. Minimum wind chills today will be in the single digits in the Poconos and in the teens for much of PA and NJ.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM THURSDAY/... Low pressure over the Canadian Maritimes moves offshore as surface high pressure over the Great Lakes builds towards the Ohio Valley. The pressure gradient over the area will relax, and winds diminish to 5-10 MPH this evening. Lows tonight will remain some 15-20 degrees below normal, dropping into the single digits in the higher elevations of the Poconos and northern NJ, and otherwise in the teens to around 20. && .LONG TERM /THURSDAY THROUGH TUESDAY/... The extended forecast starts off quiet for Thursday, but becomes unsettled for the majority of the rest of the forecast. On Thursday, high pressure builds across the area, then pushes offshore Thursday night. Dry conditions will prevail across the area through Thursday night. On Friday, a warm front will lift to our northwest during the morning hours. At the same time, a short wave/vorticity impulse will slide across the area. This is expected to help create an area of precipitation that is forecast to move across the area during the morning into the early afternoon hours Friday. Depending on how early this precipitation begins, there could be a period of a wintry mix of freezing rain/sleet/snow across portions of eastern Pennsylvania and northern New Jersey. The rest of the area should remain all rain with warmer temperatures. Friday night is expected to start out dry as the precipitation associated with the warm front moves away from the area. However, a backdoor frontal boundary is forecast to be approaching the area from the north overnight. It will likely not reach the area until the daytime Saturday, but there could be a slight chance for some showers across the northern areas overnight as a short wave approaches. Saturday begins an extended period of possible unsettled weather across the area. A backdoor cold front will sink through the area during the day Saturday, then likely stall just to our south. It may waver north across our area at times late in the weekend into early next week as a couple of waves of low pressure form and move along the boundary. Along with the waves of low pressure on the front, there will also be several short wave/vorticity impulses moving across the area through the period as well. This will lead to a chance of precipitation each day from Saturday through Tuesday of next week. Sunday night into Monday morning is forecast to be the potential for the heaviest rainfall of the period as the front is forecast to lift into the area as one wave of low pressure move across the area. Another possibility is if temperatures are cold enough across far northeast Pennsylvania and far northwest New Jersey, a wintry mix may occur. && .AVIATION /10Z WEDNESDAY THROUGH SUNDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. VFR through the TAF period with unlimited CIGs/VSBYs as high pressure builds east. NW winds will increase to 15-25 KT with 30-35 KT gusts from late morning through this afternoon. NW winds diminish to 5-10 KT after 00Z Thursday. OUTLOOK... Thursday-Thursday night...VFR with winds diminishing through the day. Friday...A period of MVFR or slightly lower conditions possible with a period of light rain; mostly during the morning into early afternoon. If precipitation begins early enough, a wintry mix is possible, especially for northern areas. Southwest winds may gust 20- 25 knots. Friday night...Conditions improving to VFR. Saturday-Sunday...MVFR or IFR conditions with periods of rain possible. && .MARINE... Cold front moves across the waters this morning. A tight NW pressure gradient develops across the waters. Gale force winds will develop this morning and will continue into this evening. For NJ ocean waters, Gale Warning runs until 03Z Thursday, and for the DE ocean waters and DE Bay, the Gale Warning will run until 00Z Thursday. OUTLOOK... Thursday-Thursday night...Conditions expected to be below Small Craft Advisory levels. Friday-Friday night...Small Craft Advisory conditions likely to return to the waters. Saturday-Saturday night...Conditions expected to fall below advisory levels. Sunday...A return to Small Craft Advisory levels expected. && .FIRE WEATHER... Dry and windy conditions in place today, with NW winds ranging from 20-30 MPH with 30-40 MPH gusts. Min RH Values will range from 25-35 percent. After coordinating with fire weather partners on Tuesday, soil moisture is still rather high in many areas, so do not plan on issuing any statements regarding fire concerns. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...Gale Warning until 11 PM EDT this evening for ANZ450>453. Gale Warning until 8 PM EDT this evening for ANZ430-431-454- 455. && $$ Synopsis...Robertson Near Term...MPS Short Term...MPS Long Term...Robertson Aviation...Robertson/MPS Marine...Robertson/MPS Fire Weather... Climate...

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