Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 110554 AFDOKX Area Forecast Discussion National Weather Service New York NY 1254 AM EST Mon Dec 11 2017 .SYNOPSIS... A low pressure trough will pass through late tonight, followed by building high pressure on Monday. Low pressure will then pass across the Great Lakes Monday night, while an associated warm front lifts through the waters Tuesday morning, followed by a strong trailing cold front in the afternoon. Intensifying low pressure will move from the New England coast into the Canadian Maritimes from Tuesday night into Wednesday night, then slowly loosen its grip on the area on Thursday as weak high pressure slides across. An Alberta clipper low will pass to the south on Thursday, then another low will develop just off the coast late Friday into Friday night. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... A shortwave and upper trough axis will approach from the west overnight, with a low pressure trough at the surface. The best combination of lift and moisture arrive after midnight with isolated to scattered snow showers. A dusting is possible. Low temps will be around 30 in NYC and the adjacent suburbs, with 20s for the rest of the area. && .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM TUESDAY/... High pressure will briefly build in behind the departing trough Monday morning, with a lingering snow shower still possible mainly east of the city. Skies will start off partly to mostly sunny, then higher level clouds will begin to increase in the afternoon. High temperatures will be a few degrees below normal. Low pressure moves across the Great Lakes Monday night. An associated warm front approaches us with increasing chances of precip late at night, more likely NW of the city. A digging upper trough and the low center then approach us during Tuesday. Associated deeper moisture and lift bring then likelihood of precip across the most of the rest of the area during the morning. The low passes us to the north before exiting during the afternoon, with maybe a secondary low center moving through. Expect precip chances to diminish in the afternoon with the best lift and moisture exiting. A cold front then follows shortly thereafter, so precip chances will continue through the day. Warm advection ahead of the main portion of the storm will make this a mixed precip event. Primarily rain is expected for the city, adjacent suburbs and coastal section, although some snow can mix in at first. Farther inland, snow or a snow/rain mix changes over to rain by noon on Tuesday. Only perhaps the elevated sections of western Orange County could see an all snow event. Snow accumulations expected to be 1 or 2 inches for the northern suburbs, with perhaps 3 inches in some spots across Orange County. Less than an inch is expected anywhere else where snow manages to accumulate. Highs in the 40s expected for most spots on Tuesday, with even some 50 degree readings for Long Island. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... At the start of the period, blustery and cold weather expected from Tuesday night into Thursday as intensifying surface low pressure moves from the eastern New England coast up into the Maritimes. The parent upper low/trough will be closing off and becoming negatively tilted during this time, and a strong vort max rotating around the upper low may help spark a few snow showers late Tue night into Wed morning, especially out east. Blustery conditions expected as the pressure gradient tightens up on the back side of the low, with sustained winds 25-35 mph and gusts 45-50 mph possible Wed into Wed night. With temps falling to the teens and lower 20s Wed night, wind chills should fall to 0 to 5 below well inland, and to the single digits in NYC metro and along the coast. High temps both Wed/Thu should range from the mid 20s to lower 30s. ECMWF has been more consistent than the GFS in the longer term beyond Wed night and was followed for the most part. A weak Alberta Clipper low should pass just south on Thu as an associated mid level impulse passes just south, then another low should develop close by late Friday as a more significant negatively-tilted upper trough swings through, that could bring a period of light snow Fri afternoon/evening. Upper level flow after passage of the upper trough on Friday should become zonal, with moderating temps, rising to the upper 30s/lower 40s on Sat, and into the 40s on Sunday. A surface low passing well to the north may manage to produce a few sprinkles/showers of snow or rain late Sat night into Sunday in the low level warm advection to its southeast. && .AVIATION /06Z MONDAY THROUGH FRIDAY/...
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A cold front will pass today. VFR through about 8Z, then ceilings drop to around 3000 ft with snow showers in the area early this morning. Little or no runway accumulation, although visibility could be briefly reduced to MVFR or lower. Ceilings improve to VFR after 15Z, with VFR through the remainder of the TAF period. Generally westerly winds through the TAF period. Direction will be just south of west until the frontal passage, then will become just north of west. Occasional gusts early this morning, then more frequent gusts to 20 kt today. Gusts will end after 23Z. .OUTLOOK FOR 06Z TUESDAY THROUGH THURSDAY... .Late Monday night-Tuesday...MVFR or lower possible with a wintry mix to rain at northern terminals and rain at southern terminals. Conditions improve to VFR Tuesday afternoon. SE-SW winds G15-25KT possible. .Tuesday night-Wednesday...Mainly VFR, with a chance of MVFR in snow showers. W-NW winds G20-35KT probable. .Wednesday night-Thursday night...VFR. W-SW winds G15-25KT possible. .Friday...MVFR possible with snow. W-NW winds G15-20KT possible.
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&& .MARINE... SCA conditions expected on the ocean waters through Monday with winds and seas meeting criteria. Marginal SCA conditions expected on the eastern Sound/bays. Winds and seas should fall below criteria Monday night, then increase during Tuesday, with SCA conds becoming likely on some of the waters. As intensifying low pressure pulls away, gales should develop on the ocean Tue night, with SCA conds continuing on the remaining waters. NW gales expected on all waters Wed night into Thu with a tight pressure gradient and strong cold air advection. SCA conds may linger into Thu, then quiet conditions expected Thu night into Fri, though winds and seas in westerly flow after the passage of a weak low Fri night could flirt once again with SCA levels. && .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. See our headline news on the web at: http:/weather.gov/nyc The Riverhead NOAA Weather Radio Station WXM-80 (162.475 MHz) is currently out of service. NWS technicians are working with Verizon to restore service. An estimated time of return to service is not currently known. && .OKX WATCHES/WARNINGS/ADVISORIES...
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CT...None. NY...None. NJ...None. MARINE...Small Craft Advisory until 6 PM EST this evening for ANZ350- 353-355. Small Craft Advisory until 6 AM EST early this morning for ANZ330-340.
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&& $$ SYNOPSIS...JC/Goodman NEAR TERM...JMC/JC/Goodman SHORT TERM...JC LONG TERM...Goodman AVIATION...BC/JMC MARINE...JC/Goodman HYDROLOGY...JC/Goodman EQUIPMENT...

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