Area Forecast Discussion
Issued by NWS Upton, NY

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921 FXUS61 KOKX 160931 AFDOKX Area Forecast Discussion National Weather Service New York NY 431 AM EST Sat Dec 16 2017 .SYNOPSIS... Weak low pressure passes to the north today bringing a cold front south of the region. High pressure builds in for tonight and Sunday. Then a series of lows will pass through the area through mid week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Heights will be slowly rising through the day as northern stream trough lifts out to the northeast. A weak shortwave and associated vort max rotates through the trough, with much of the energy passing to the north. At the surface a weak low will pass through New England. A cold front does come through late this afternoon and into early this evening. However, the front is rather weak, and will be more reflected by a wind shift. Precipitation will be minimal, and have lowered probabilities across the region as the NAM and HRRR show light precipitation, mainly across the northern and western areas of the CWA. Also, will be more convective in nature, so keeping snow showers wording. Only a tenth or two of snow will be possible, with accumulations mainly across the lower Hudson Valley. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SUNDAY/... A few flurries may be lingering into the early evening hours if the cold front is slower to push through. At this time will keep the evening dry. After 03Z heights will continue to rise through Sunday as the flow becomes more zonal. A dampening shortwave will be moving into the weak upper ridge late Sunday and Sunday night, and pass through Sunday night. && .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/... A weakening shortwave passes through Sunday night into Monday. Have lowered the probabilities slightly as the shortwave is weakening and flat, with little moisture. Warmer air will be pushing into the region, and as the warm air lifts north of the cold surface air a period of freezing rain, some ice pellets and snow will be possible. Too early for specific details on this light precip event. Thereafter, models in fairly good agreement with the broad bu shallow northern stream trough approaching the region on Tuesday and sliding through during the midweek. At the surface, the primary low pressure system rides through Quebec/Ontario with trailing cold front approaching the region Tuesday Night. Overall, appears to be mainly a light qpf event for the Monday night into Tuesday evening period, due to limited interaction between northern and southern stream. Thermal profile suggests precip would be mainly liquid, but could be dealing with freezing rain across interior Monday night as cold air typically has a tough time scouring our in this setup. Upper trough swings through the NE Tue Night into Wed with a glancing shot of modifying arctic air in the wake of the cold front for Wed/Thu. Upper flow flattens and even becomes a bit ridged for Thursday ahead of the next northern stream trough digging into the Upper Plains, which should allow for a moderation in temps ahead of next potential frontal system. && .AVIATION /09Z SATURDAY THROUGH WEDNESDAY/... Weak low pressure tracks across New England today dragging a cold front through this evening. VFR into mid morning or so with CIGS between 3-5 KFT developing from late morning through the afternoon. Local MVFR or IFR conditions cannot be ruled out in isolated rain or snow showers late in the day mainly N and W of NYC terminals. Westerly winds 5 to 10 kt continue early this morning. Occasional gusts to around 20 kt are possible, mainly across NYC metro terminals. After 12-14Z, westerly winds increase to 15 to 20 kt, with gusts 20 to 30 kt. Gusts become less frequent after 20-21Z. By evening, winds turn to the NW and diminish. .OUTLOOK FOR 06Z SUNDAY THROUGH WEDNESDAY... .Late tonight...VFR. .SUN...VFR during the day. Chance MVFR in a mix of -RA/-SN towards midnight. .MON...Low chance MVFR in -RA for coastal terminals, light wintry mix inland. Improvement as the day progresses. .TUE...MVFR possible with a slight chance of showers. .WED...VFR. NW winds G20-30KT. && .MARINE... Gusty small craft winds will be likely across all the forecast waters today into early this evening as a rather tight pressure gradient moves through the waters as low pressure moves into the Atlantic and high pressure builds to the west. So, will continue with the small craft advisory as posted. Gusty winds may linger into this evening on the ocean waters. Ocean seas may remain around small craft levels into Sunday evening as well. So, the advisory remains into this evening on the ocean. The next chance for SCA conditions will be late Tuesday/Tue eve ahead of approaching cold front, but higher likelihood of widespread SCA Tuesday Night through Wednesday night with tight pressure gradient and strong caa in wake of cold front. Gales are possible during this time frame. && .HYDROLOGY... No significant hydrologic impacts expected. && .EQUIPMENT... NYC NOAA Weather Radio Station KWO-35 (162.55 MHz) is off the air for an extended period of time. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...Small Craft Advisory until 7 PM EST this evening for ANZ330- 335-338-340-345. Small Craft Advisory until 1 AM EST Sunday for ANZ350-353-355. && $$ is the U.S. government's official web portal to all federal, state and local government web resources and services.