Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 160803 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 303 AM EST Thu Feb 16 2017 .SYNOPSIS...
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An area of low pressure will continue to intensify as it moves into the Canadian Maritimes tonight and lingers there through Friday. Weak high pressure affects the area Friday into Friday night. An area of low pressure will pass well to our north Saturday night into Sunday, pulling a cold front across our area early Sunday, then another boundary may move into the area later in the day. High pressure affects the area Monday into Tuesday, before moving offshore Tuesday night.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Strong cold air advection will continue through the day under a continued northwest flow pattern. A mid level trough axis digging southeast on the back side of the closed low will cross our region later today. The combination of this plus the continued strong northwesterly flow should result in scattered snow showers across the Poconos, Lehigh Valley and northern NJ. As with the snow showers last evening, expect most places to see a dusting, though localized amounts up to an inch are possible. As for the winds, expect the strongest winds to be through early afternoon before the pressure gradient begins to decrease late in the afternoon. The mixed layer could be as deep as through 800mb. If this is the case, could see peak gusts up to 35 mph. Trended the max temperature forecast down slightly as mid level cloud deck has already moved over much of the region, and should persist for much of the day, limiting solar insolation. Highs should be about 10 to 15 degrees below highs yesterday.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM FRIDAY/...
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Closed low continues to lift further away from the region. As it does so, the pressure gradient over the region will continue to decrease. By late this evening, expect winds across the region to drop off to around 10 mph. With the winds dropping off and the mid level cloud deck expected to erode, should see efficient radiational cooling, with lows ranging from the teens to mid 20s. Even so, this will mean lows will be near or just slightly below normal.
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&& .LONG TERM /FRIDAY THROUGH WEDNESDAY/...
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A mostly dry forecast for the majority of the extended. For Friday, low pressure will continue to drift through the Canadian Maritimes and the pressure gradient will weaken across our area as weak high pressure moves across the area through Friday night. The northwest winds are not expected to be as strong as they were during the day Thursday, but they will still elevated with gusts around 20 mph at times. On Saturday, a warm front may lift north of the area as low pressure moves across southern tier of Canada. The low passes to our north overnight Saturday into early Sunday. This will bring a couple of cold fronts/surface troughs across the area early Sunday morning and later Sunday afternoon. The airmass is forecast to be relatively dry and there is not much in the way of short waves/vorticity impulses to help create any shower activity. So we`ll keep the forecast dry. High pressure is then expected to affect the area on Monday into Tuesday. Dry weather should continue on Monday, but a warm front may pass to our west on Tuesday as high pressure begins to shift offshore. A couple of short wave/vorticity impulses may cross the area Tuesday through Wednesday which may help create some isolated showers.
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&& .AVIATION /08Z THURSDAY THROUGH MONDAY/...
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The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. VFR conditions are expected through the TAF period. Mid level deck between 4000 and 6000 ft AGL is expected to persist through at least 21Z before slowly dissipating. Winds are expected to stay northwesterly through the TAF period. Peak winds are expected between 15 and 21Z. At their peak, winds could be as strong as 20G30KT. We should see a gradual decrease in speeds between 21 and 03Z, before settling in around 10KT through the rest of the night. OUTLOOK... Friday-Monday...Generally VFR expected, although MVFR CIGS may be possible during the day if clouds develop. Gusty winds 15-20 knots during the day.
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&& .MARINE...
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The gale warning on the lower Delaware Bay has been converted to a Small Craft Advisory. The SCA on all of the Bay now goes through midnight tonight. No changes to the gale warning on the Atlantic coastal waters. We are in a temporary lull in the winds currently, but they are expected to increase once again in the pre-dawn hours with gale force conditions expected on the ocean waters and small craft advisory conditions expected on the Delaware Bay. Winds are expected to slowly subside through the late afternoon and evening hours. Once winds drop below gale conditions on the Atlantic coastal waters, an SCA will be needed. OUTLOOK... Friday...Small Craft Advisory level conditions possible early, then diminishing during the day. Friday night-Monday...Sub Small Craft Advisory conditions expected. Winds may gust around 20 knots at times however.
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&& .CLIMATE...
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The month as a whole has so far averaged 3 to 5 degrees above normal through Valentines Day, except just a little more than a degree above normal at KMPO. There isn`t any sign of long duration substantially colder than normal air coming in February and in fact some of the guidance is suggesting near record warmth is possible this weekend. We`ll take a closer look at that later today. Suffice to say...February is highly likely to average above normal. We`ll try and figure to what degree, also later today. Snowfall continues to average well below normal. It`s still too early to look at the lower value ranking for the season, especially since there is some ensemble guidance indicating a more active storm track developing in our area by the first week of March.
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&& .PHI WATCHES/WARNINGS/ADVISORIES...
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PA...None. NJ...None. DE...None. MD...None. MARINE...Gale Warning until 6 PM EST this evening for ANZ450>455. Small Craft Advisory until 6 PM EST this evening for ANZ430. Gale Warning until 6 AM EST early this morning for ANZ431.
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&& $$ Synopsis...Robertson Near Term...Johnson Short Term...Johnson Long Term...Robertson Aviation...Johnson/Robertson Marine...Johnson/Robertson Climate...

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