Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 130910 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 410 AM EST Fri Jan 13 2017 .SYNOPSIS...
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A cold front moving across the area early this morning will push farther offshore through today. High pressure will build just to our north tonight, then weaken Saturday into Saturday night as it moves offshore. An area of low pressure passes to our south Saturday night, then high pressure will reestablish itself to our north Sunday, then build offshore Sunday night into Monday. An area of low pressure is forecast to move into the Great Lakes region Tuesday, lifting a warm front across the area Monday night into Tuesday morning. A warm southwest flow will likely develop across the east coast for the middle to end of the week with a weak cold front possible Wednesday or Wednesday night.
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&& .NEAR TERM /UNTIL 6 AM THIS MORNING/...
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The cold front continues to make progress through our region early this morning and is expected to exit offshore around sunrise. With cooler air moving in behind the front, we will see temperatures start to fall throughout the day, although with the direct sunlight temperatures may remain fairly steady through the peak heating of this afternoon. Max temps have already occurred overnight closer to midnight. Winds will pick up once the sun rises and we start to mix efficiently. Winds will become pretty gusty through the afternoon with gusts around 20 to 30 mph.
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&& .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM SATURDAY/...
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High pressure will build into central New York tonight. This will help to keep us fairly dry and cold as cold air damming sets up in the northerly flow. Clouds will start to move back into the region and increase in coverage as several waves of moisture move into our area. For now, the precipitation looks to hold off until early Saturday morning. With temperatures being right near their minimums when the precipitation starts to move in, we could see more of wintry mix of snow/sleet/freezing rain at the onset across Delmarva. A cold night across the region. We went below guidance as it may take a little while for the thicker cloud cover to arrive and we should radiate fairly well at the start of the period, especially across the northern areas and higher elevations. Overnight lows will drop down into the 20s with teens across the southern Poconos, parts of the Lehigh Valley and parts of northwest New Jersey.
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&& .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
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Several periods of unsettled weather possible through the extended forecast. As we move into Saturday, the high to our north is forecast to weaken and move offshore late in the day and into Saturday night. As we move through the day, plenty of low-mid level moisture, along with enhanced vertical lift will spreading across the area as several short wave/vorticity impulses are forecast to slide across the area during this time period. This will lead to a period of precipitation developing and spreading across the area during the day and into the evening Saturday. The question becomes what kind of p-type develops across the area. With the weakening high pressure to our north, we should have cold air get trapped across the area. The precipitation should start out as snow as the vertical column should be all below freezing to start. However, through the day, some warm air aloft could be making its way across some of the area. This will present a problem for P-Types. For areas north of the PA Turnpike and I-195 in New Jersey, precipitation should remain all snow or a mixture of snow and possibly sleet. However, south of this line things get a little more tricky. If surface temperatures have a hard time rising during the day, this could lead to a period of a wintry mix of snow/sleet/freezing rain. We have decided to not issue an advisory yet as there is still some uncertainty in where the freezing rain will develop. The moisture and enhanced lift should push south of the area overnight Saturday and precipitation should come to an end during the overnight hours. High pressure will reestablish itself Sunday and move just to our north during the day before moving offshore overnight. Drier air is expected to move across the area which should keep the forecast dry. There is an area of moisture and lift that is forecast to pass to our south, but should remain just south of the area. By Monday, the high builds offshore to our north and return flow develops across the area which will allow for some warming across the area. A warm front is forecast to lift across the area overnight Monday and move to our north Tuesday as an area of low pressure moves into the Great Lakes. Several short wave/vorticity impulses will continue to move across the area in the westerly flow aloft. This will keep the chance for precipitation to develop as the warm front lifts across the area and passes to our north. There is the potential for a wintry mix of snow/sleet/freezing rain for areas along and north of I-78 Monday night into Tuesday morning. South of this area, the precipitation may be mostly rain, or a mix of rain, sleet, and snow with surface temperatures above freezing. The warm front lifts north of the area by Tuesday. A warm southwest flow then develops through Tuesday and Wednesday across the area. Several short wave/vorticity impulses will continue to move across the area, which will lead to a chance of precipitation. Temperatures are forecast to be above freezing, so any precipitation should be all rain. A weakening cold front is forecast to move across the area during the middle of the week. However, the there is timing differences with the GFS being about 12 hours faster than the ECMWF. Nevertheless, a chance of precipitation will continue through Thursday, and with warm temperatures, any precip is expected to be all rain.
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&& .AVIATION /09Z FRIDAY THROUGH TUESDAY/...
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The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. West to southwest winds less than 10 knots continue at the terminals. As the cold front moves through, winds will start to shift more to the west and then northwest. The light showers ahead of the cold front have mostly dissipated with only isolated showers remaining along the I-95 corridor and points to the south and east. Not expecting any restrictions as a result of the remaining showers. Today we expect VFR conditions to continue with breezy northwest winds 10 to 20 knots with gusts up to 25 knots. Winds will gradually diminish later this afternoon and then we should lose the gustiness entirely by early evening. Ceilings are expected to lower towards the end of the TAF period as the next system arrives. Light precipitation may arrive towards the tail end of the TAf period, mainly at KILG and KMIV. OUTLOOK... Saturday-Saturday night...Deteriorating conditions with MVFR or IFR conditions developing Saturday and continuing into Saturday night. Wintry mixture of precipitation possible, with mainly snow/sleet for ABE/RDG/TTN, and snow/sleet/freezing rain possible for the remainder of the TAF sites. Sunday-Sunday night...Conditions improving to VFR. Monday-Tuesday...Generally VFR early, lowering to MVFR, then to IFR late Monday night into Tuesday. Chance of precipitation late Monday into Tuesday. A wintry mix possible, mainly north of TAF sites Monday night into early Tuesday
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&& .MARINE...
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The Small Craft Advisory remains up on the ocean waters through 6pm tonight. Winds will gust out of the northwest through the early evening as decent cold air advection arrives and drags the colder air over the warmer waters. Seas are still running around 5 to 7 feet but will start to drop through this afternoon. Both seas and winds are expected to fall below Small Craft Advisory criteria by early this evening. Both may fall below criteria by late afternoon and the advisory may be able to be cancelled a bit early. OUTLOOK... Saturday-Tuesday..Sub-Small Craft Advisory conditions expected through the period, although winds may gust 15-20 knots at times Saturday night/Sunday.
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&& .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...Small Craft Advisory until 6 PM EST this evening for ANZ450>455. && $$ Synopsis...Robertson Near Term...Meola Short Term...Meola Long Term...Robertson Aviation...Robertson/Meola Marine...Robertson/Meola

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