Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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401 FXUS61 KPHI 142345 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 645 PM EST Sat Jan 14 2017 .SYNOPSIS... High pressure off the New England coast and weak low pressure over the waters off North Carolina will both move farther out to sea tonight and Sunday. Another area of high pressure is anticipated to build into our region from the west for Sunday night and Monday. A warm front is expected to approach from the south on Tuesday followed by another frontal boundary from the west on Wednesday morning. High pressure is forecast to build in for much of Thursday through Saturday. && .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/... A challenging forecast given a variety of precipitation types occurring. We appear to be losing the isentropic lift across the north which is diminishing the precipitation, with the most focus now shifting to our southern zones. In addition, some drying aloft following the initial wave of precipitation is resulting in a loss of ice crystals. As a result, the light snow is mixing with or changing to some light freezing rain/drizzle in spots north and west of Philadelphia. This is resulting in some slippery conditions being reported. The precipitation may be ending in the very near term however. Farther south, enough warming is resulting in mostly plain rain with temperatures above freezing. Some sleet however has mixed in especially earlier. The grids were completely updated to hopefully better capture this (PoPs increased substantially with an earlier update), although it is challenging. Looks overall like little in the way of additional snow/ice accumulations from here on out. A Special Weather Statement was issued earlier to cover some icy spots mainly north and west of Philadelphia. The precipitation will end from west to east later this evening overall, then lots of clouds should linger through the overnight especially for the southern and eastern areas. The hourly temperature and dew point grids were adjusted based on the latest observations, then the LAMP/LAV guidance was blended in to assist. && .SHORT TERM /6 AM SUNDAY MORNING THROUGH 6 PM SUNDAY/... A dry, warmer and mainly sunny day is expected for Sunday, albeit with a nw flow so it won`t feel quite as temps in the 40s would have it seem. Still not bad for mid-January. && .LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/... The general mid level pattern features a ridge axis passing overhead on Tuesday followed by a couple of short wave troughs on Wednesday then a trend toward mid level ridging over the east during the period from Thursday through Saturday. The GFS is more progressive with the arrival of the mid level ridge than is the ECMWF. The center of surface high pressure is expected to build across our region from the west early on Monday bringing dry weather and seasonable temperatures for Sunday night and Monday. A warm front is forecast to lift toward our region on Tuesday. A lobe of mid level moisture in the warm advection is anticipated to pass overhead on Monday night. There may be some light precipitation associated with it. Additional moisture is expected to arrive on Tuesday during the daylight hours along with an increasing chance for precipitation. The forecast temperature profiles continue to suggest warming aloft with the arrival of the precipitation. However, sub-freezing air may linger near the surface in parts of eastern Pennsylvania and central and northern New Jersey for Monday night into Tuesday morning. As a result, we will continue to mention the potential for some freezing rain at that time. The last of the sub-freezing air in our northern counties should erode and mix out of that area by Tuesday afternoon. While the potential for rain will continue, the threat of freezing rain will come to an end at that time. High temperatures on Tuesday should be mainly in the 40s in eastern Pennsylvania and northern and central New Jersey,and in the lower and middle 50s in southern New Jersey, Delaware and northeastern Maryland. A cold front approaching from the west is anticipated to arrive early on Wednesday. We will carry a chance of showers for both Tuesday night and Wednesday. Also, abundant low level moisture in advance of the front will likely result in the development of areas of fog at that time. Temperatures should remain mild even with the arrival of the front. Lows on Tuesday night are forecast to be mostly in the upper 30s and 40s and highs are expected to range from the upper 40s in the north to the lower 60s in the south. The air mass in the wake of Wednesday`s front will not be particularly cold. In fact, it appears as though dry and relatively mild conditions will affect our region for Thursday, Friday and Saturday. We should be mainly under the influence of high pressure. && .AVIATION /00Z SUNDAY THROUGH THURSDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Tonight...VFR/MVFR ceilings lowering to IFR, then improving back to VFR after 09z. Light snow and rain will taper off from west to east later this evening, with some terminals experiencing some light freezing rain/drizzle (mainly RDG). Winds light and variable overall, becoming northwest after 06z near 5 knots. Sunday...VFR. North-northwest winds increasing to mainly 10-15 knots. OUTLOOK... Sunday night and Monday...Mainly VFR. Monday night...Mainly VFR. A chance of light rain late at night. There may be light freezing around KRDG, KABE and KTTN. Tuesday...Conditions lowering to MVFR and IFR in rain. Some lingering freezing rain is possible in the morning around KRDG and KABE. Tuesday night...IFR and MVFR conditions are expected with fog and rain. Wednesday...IFR and MVFR conditions are expected with fog and rain showers in the morning. Improvement to VFR is anticipated in the afternoon. Wednesday night and Thursday...Mainly VFR. && .MARINE... No marine headlines are expected thru the nr and short term pds. Seas will genly be 2-3 feet. Wind cud gust as high as 20 kts for awhile Sun mrng. OUTLOOK... Sunday night through Thursday...No marine headlines are anticipated. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...Winter Weather Advisory until midnight EST tonight for PAZ101- 102. NJ...None. DE...None. MD...Winter Weather Advisory until midnight EST tonight for MDZ008- 012. MARINE...None. && $$ Synopsis...Iovino Near Term...Gorse Short Term...Nierenberg Long Term...Iovino Aviation...Gorse/Iovino Marine...Iovino/Nierenberg

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