Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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520 FXUS61 KPHI 201420 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 1020 AM EDT Mon Mar 20 2017 .SYNOPSIS... High pressure located along the Appalachians early this morning will sink to the south and it should begin to lose its influence over our weather today. Weak low pressure approaching from the west is forecast to pass off the Middle Atlantic Coast on Tuesday. A cold front from the north is expected to arrive late on Tuesday night followed by strong high pressure. The center of the high is anticipated to pass nearby on Thursday before moving slowly out to sea. A warm front is forecast to lift through our region on Friday. Low pressure is expected to approach from the west over the weekend. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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A nice day for the first day of Astronomical Spring, although there remains some snow on the ground for many areas and temperatures are expected to be a few degrees below normal. The recent visible satellite pictures clearly show the snow on the ground N/W of the fall line (roughly KBLM-KTTN-KPHL). Sunny skies will prevail into the early afternoon before high and mid level clouds arrive from the N/W. High pressure builds to our south through the day and weakens its grip on our area.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM TUESDAY/... Tonight, a weak surface trough will approach the area overnight, while a weak low pressure approaches our southern areas as well. The low will stay south of the area, though the trough may make its way into the area. At the same time, a mid- level vorticity impulse will be sliding across the area as well. There is not a much deep moisture associated with these features, but there could be enough lift with the disturbance aloft to interact with the moisture across the area to create some light precipitation overnight. The most likely areas are across southeastern Pennsylvania, the Delmarva, and southern New Jersey. Temperatures across these areas where the precipitation is most likely are expected to be above freezing and be a cold rain. Areas across the Poconos and northwestern New Jersey may drop below freezing for a period overnight, but they are less likely to see any precipitation. We will still keep a chance of a wintry mix of rain, sleet, or snow. Thermal profiles don`t show a significant melting potential, so anything snow that melts may only partially melt and fall as snow or ice pellets where temperatures are cold enough. If rain does occur and temperatures are below freezing, a brief period of freezing rain may occur; but since the potential is small and confidence is low, so we`ve kept it out of the forecast for now. && .LONG TERM /TUESDAY THROUGH SUNDAY/... The mid level pattern is forecast to remain rather progressive during the period from Tuesday through Sunday, keeping the weather systems moving along in the flow. Weak low pressure is expected to be located over Virginia on Tuesday morning. The feature should pass off the coast on Tuesday. We are anticipating a fair amount of cloud cover in the morning, with a decrease in clouds as the day progresses, especially over eastern Pennsylvania and northern and central New Jersey. There is a slight chance of morning rain showers in parts of eastern Maryland and central and southern Delaware. A cold front is forecast to drop through our region late on Tuesday night with a robust shot of cold advection in its wake from late Tuesday night into Wednesday morning. No precipitation is expected with the front in eastern Pennsylvania and northern and central New Jersey. However, we will maintain the mention of a slight or low chance of rain showers in northeastern Maryland, Delaware and southern New Jersey at that time. A 1040 HPa high is anticipated to build down from the northwest on Wednesday with its center passing over or near our region on Thursday. We are forecasting chilly dry weather for both days. Wednesday should have a brisk northwest wind with a relatively light wind expected for Thursday. The center of the high is forecast to move out to sea on Friday allowing a warm front to lift through our region in the return flow. Some spotty rain is possible. Also, there could be some localized freezing rain in our northern counties on Friday morning if the precipitation arrives before the temperatures have time to recover from their morning lows. A very mild southwesterly flow is forecast to develop for Saturday as a cold front drops toward our region from the north and as low pressure approaches from the west. We will mention a chance of rain for Saturday night and Sunday. The forecast looks to get complicated for late Sunday into the early part of the new week. The center of another 1040 HPa high is expected to build into Quebec with cold air pushing southward into the northeastern state. We could see some wintry precipitation at that time in parts of our region. As is often the case during this time of the year, temperatures will be all over the place. Daytime highs should be about 10 to 15 degrees below normal on Wednesday and about 10 to 15 degrees above normal on Saturday with the other days falling somewhere between the two. && .AVIATION /14Z MONDAY THROUGH FRIDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. VFR conditions prevail across the TAF sites and will remain VFR through the day. Clouds will increase and thicken through the day, and especially tonight. An area of light rain may affect the TAF sites overnight, which could temporarily lower conditions. Northwest winds 5-10 knots through most of the day will become more westerly later this evening. Many locations may become light and variable at times overnight. OUTLOOK... Tuesday through Thursday night...Mainly VFR. Friday...Mainly VFR. A a chance of light rain and localized MVFR conditions mainly from KRDG, KABE and KTTN northward. && .MARINE... Winds remain below 25 knots, but seas on the Atlantic Ocean remain elevated this morning. Seas are expected to subside below 5 feet later in the day, so we`ve extended the Small Craft Advisory through the afternoon. Conditions are then expected to remain below advisory levels through tonight. OUTLOOK... Tuesday and Tuesday night...No marine headlines are anticipated. Wednesday and Wednesday night...Northwest to north winds may gust to 25 or 30 knots. Localized gale force gusts are possible. Thursday through Friday...No marine headlines are anticipated. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...Small Craft Advisory until 6 PM EDT this evening for ANZ450>455. && $$ Synopsis...Iovino Near Term...Robertson/PO Short Term...Robertson Long Term...Iovino Aviation...Iovino/Robertson Marine...Iovino/Robertson

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