Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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193 FXUS61 KPHI 100546 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 1246 AM EST Sat Dec 10 2016 .SYNOPSIS... High pressure will build into the region through Sunday as low pressure over eastern Canada moves away. Then, low pressure will develop over the central plains on Sunday and move toward the Great Lakes on Monday. This low will bring a warm front through the area on Sunday night and a cold front across the Mid-Atlantic on Monday. Yet another cold front is expected to move across the area Tuesday night or Wednesday and a low may form along this front. A strong west to northwest flow is expected to develop by the end of the week as high pressure tries to build. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
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A band of snow has developed across eastern Pennsylvania and southern New Jersey, which extends back across north central Pennsylvania and western New York. This is associated with a vort max that is currently lifting across the area. This vort max is forecast to continue to lift northward across the area during the overnight period. So this band of snow will continue to slowly lift northward over the next few hours as well. It is putting down a light coating of snow as we`ve had reports of around a quarter of an inch. Outside of this snow band, the forecast will remain precipitation free.
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&& .SHORT TERM /6 AM SATURDAY MORNING THROUGH 6 PM SATURDAY/... There will be fairly steep lapse rates combined with some enhanced moisture across the far northern tier of the area. With the west- northwest flow remaining across the area, there should be scattered lake and moist lapse rate enhanced snow showers/flurries developing which could make their way down to I-80 (even a dusting is possible). West to northwest winds should gust 20-25 mph, especially afternoon. Forecast basis: 50 50 blend of 12z/9 GFS/NAM MOS. && .LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/... The active long term pd will start off rather quiet, with high pres over the region. This high will keep things mainly dry and cold for Sat night into early Sun. Then, as the high moves ewd, low pres will develop over the plains and move newd twd the Grtlks by Mon mrng. As it does, the low will pull a wmfnt thru the area. Precip will develop out ahead of the wmfnt beginning psbly as early as Sun aftn in the w. There continue to be some timing diffs with the onset of the precip. The GFS is slower and therefore drier on Sun, not really bringing the precip into the area until Sun night and then mainly over PA and NJ with little over DE and MD until Mon. The ECMWF brings the precip faster but also keeps srn areas dry for a good portion of Sun and Sun night. The big question is temps. How warm do they get on Sun, how quickly do they warm Sun night into Mon and what track the low takes which will impact the passage of the warm front. It is certainly psbl that the precip starts as all snow for a good portion of the area even as far s as the I-95 corridor on Sun or Sun night. However, all guid is consistent on warming things overnight from se to nw and changing any wintry precip to plain rain over the course of the night and into Monday. The Poconos and nrn NJ will be the last places to change over, but right now it looks like even they will eventually change to rain. Latest accumulation maps are similar to previous with perhaps an inch more in the extreme nrn and wrn areas and not much for the I-95 corridor before any change over to rain. The cfp from the low, which will now be in sern Canada will occur Mon aftn and end the precip. Temps Mon aftn will reach well into the 40s and 50s in many areas ahead of the cfp. Then high pres builds in and expect Tue to be dry. Around midweek, confidence drops significantly as the mdls disagree on another storm around midweek. The GFS tries to develop a coastal storm around Wed which would bring another mixed precip event, wintry precip to the n and w and genly rain s and e. However, the ECMWF is dry on Wed and then tries to bring in precip on Thu. So, for now have just kept low chc on each day. Temps will rise to nrml or abv nrml by MOn and Tue but then drop by Thu. && .AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...
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The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Overnight...Generally VFR. A band of snow showers/flurries is drifting across eastern Pennsylvania and southern New Jersey. This band will likely move across PHL, PNE, ABE, and possibly TTN and could temporarily lower conditions. West winds generally 5-10 knots. Saturday...VFR sct-bkn aoa 4000 ft. Isolated or scattered snow showers/flurries E PA and northwest NJ, which may temporarily lower conditions, especially I-80 region northward. Gusty west to northwest winds around 20-22 knots during the day. OUTLOOK... Sat night...Generally VFR. Isolated SHRA/SHSN or flurries/sprinkles are possible across the northern half of the area during the day which may temporarily lower conditions. Gusty west to northwest winds 15-20 knots during the day. High confidence. Sun...VFR early, lowering to MVFR by the afternoon. RA or SN psbl late in the day. Moderate confidence. Sun night-Mon...MVFR early, then IFR overnight into Monday. RA or SN becoming likely. Accumulating snow possible for the northern third of the area, with a chance of FZRA around daybreak. Rain/snow mix for central third of the area. Rain across the southern third. All precipitation likely to become all rain Monday from SE to NW. Moderate confidence. Mon night...Improving conditions overnight to VFR. High confidence. Tue...VFR expected. High confidence. Wed...Another sys may impact the area which could bring lower cigs/vsbys and a mixed bag of precip, generally wintry precip to the n and rain to the s. Low confidence.
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&& .MARINE...
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GLW extended through 4 am for the waters north of Atlantic city (little Egg Inlet to Sandy Hook), with gusts occasionally around 35 kt. SCA continues south and central with max gusts this evening of 28 to 32 kt. Wind gusts to 40 kt vcnty High Point NJ during mid aftn corroborates the modeled nw flow jet near 925 MB that should flow southeast through the NNJ waters this evening with wind gusts increasing a few knots from mid afternoon. Winds will be only very slow to decrease late at night and Saturday due to large over water lapse rates and the cool boundary layer temp heat sink. Gale verification for overnight and this morning: Brandywine and Cape May verified the 2 hour minimum/12 hr gale gust criteria for the southern zones and then 44065 (our closest overwater operational wind buoy) verified the far northern NJ portion of the warning this morning and gain during the past two early afternoon hours. We had many locations along the water with 30 to 100 min period of mid 30s gale gusts last night, centered near 03z/9. Outlook... Sat night-Sun night...Conds expected to remain below SCA levels, although winds could gust around 20 knots at times. Mon-Mon night...SCA conds likely. Tue-Wed...sub SCA conds expected.
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&& .CLIMATE... Note: The low temp expected at PHL Saturday morning should be the coldest of the season so far at PHL (25-29F), the first 20s of the season. Last winter, it didn`t drop into the 20s until January 4th 2016! && .PHI WATCHES/WARNINGS/ADVISORIES...
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PA...None. NJ...None. DE...None. MD...None. MARINE...Small Craft Advisory until 4 PM EST Saturday for ANZ431- 452>454. Gale Warning until 4 AM EST Saturday for ANZ450-451. Small Craft Advisory until 11 AM EST Saturday for ANZ455. Small Craft Advisory until 4 AM EST Saturday for ANZ430.
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&& $$ Synopsis...Nierenberg Near Term...Drag/Robertson/MPS Short Term...Drag Long Term...Nierenberg Aviation...Drag/Nierenberg/Robertson Marine...Drag/Nierenberg/Robertson Climate...

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