Area Forecast Discussion
Issued by NWS Upton, NY

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899 FXUS61 KOKX 142105 AFDOKX Area Forecast Discussion National Weather Service New York NY 405 PM EST Sat Jan 14 2017 .SYNOPSIS... A wave of low pressure passes to the south and east tonight. High pressure builds Sunday and Sunday night. High pressure across the region Monday drifts offshore Monday afternoon into Monday night. A warm front approaches from the west Tuesday and slowly moves in Tuesday into Tuesday night. It moves through and to the north of the area late Tuesday night with a cold front to follow for early Wednesday. Weak high pressure builds in from the west from mid to late week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Very dry atmosphere earlier has moistened quickly across western locales. Warm air advection, mid level lift aided by approach and passage of H3 jet will allow for passing light snow to occur into this evening. Pops will be layered from likely NYC metro and Long Island, with chance to slight chance as you head north across the interior. Any light snow will product a coating to a half an inch. A wave of low pressure rides along a stationary frontal boundary to the south overnight. Temperatures will fall this evening especially as snow develops, then fall further late tonight as skies clear and NW winds commence. && .SHORT TERM /6 PM THIS EVENING THROUGH SUNDAY NIGHT/... Initial shortwave aloft passes well east, with a general W/NW flow expected aloft through this time frame. Surface high pressure builds across the Great Lakes Region/Ohio Valley toward and over the area Sunday night. Dry weather, with generally clear skies, can be expected. Temperatures will rise to the upper 30s to middle 40s, slightly above normal. A NW breeze during the day diminishes at night as the pressure gradient relaxes. Good radiational cooling conditions prevail, with low temperatures ranging from near 30 in NYC, to the teens across the normally colder spots, interior and pine barrens of eastern Long Island. && .LONG TERM /MONDAY THROUGH SATURDAY/... Upper levels exhibit split jet structure with subtropical jet approaching the region Monday night into Tuesday. This jet amplifies Tuesday night into Wednesday with local region being in the left front quadrant of enhanced synoptic lift. This jet will then become more suppressed to the south of the region late Wednesday through the end of the week. Upper and mid levels show slight ridging Monday into Tuesday and then a nearly steady geopotential tendency Tuesday afternoon into Tuesday evening before becoming negative Tuesday night through Wednesday. Weak ridging builds in slowly from the west thereafter. At the surface, high pressure will be across the region and will present an airmass with slightly above normal temperature under a mostly sunny sky and light winds. The sky remains mostly clear to start Monday night and winds remain light so radiational cooling will be optimal the first half of the night. Then, clouds increase as a warm front approaches with associated isentropic lift. The warm air advection aloft will set temperatures a few degrees above freezing within the 1kft to 5kft layer and with surface temperatures for most locations Monday night into early Tuesday, if precipitation arrives early enough, this would be in the form of freezing rain. Later on Tuesday by mid to late morning, temperatures rise with light onshore flow and any freezing rain would change to plain rain. The progression of this would be from south to north with interior locations being last to change to plain rain. Temperatures are expected to rise into the upper 30s to lower 40s Tuesday. Not much of a drop in temperatures Tuesday night as warm front works its way through the region. Rain continues and then tapers off late Wednesday into Wednesday night from west to east behind the cold front. Low pressure slowly moves northeast of the region eventually into the Canadian Maritimes by end of the week. Weak high pressure builds in from the west. Dry weather expected Wednesday night through end of the week. Temperatures are near normal Tuesday and above normal Tuesday night through the rest of the forecast period. && .AVIATION /21Z SATURDAY THROUGH THURSDAY/... A stationary front will remain south of the region through tonight. High pressure will build in from the west on Sunday. Snow, mainly light, will continue this evening. Snowfall rates are expected to be a half inch per hour or less. Total snowfall accumulations, due to the light rates, are not expected to exceed around a half inch at this time. Only flurries may occur at Newburgh. After the initial snow early this evening, there is a chance that visibilities are better than the TAFs indicate. Ceilings have been kept at 1000 ft in the snow, however, pockets of a few hundred feet are likely in heavier snow. VFR returns quickly after the snow ends, and remains through the remainder of the TAF period. Light flow, generally at or below 6 kt, can be expected through 6- 10Z. The flow will increase slightly out of the northwest by Sunday morning. .OUTLOOK FOR 18Z SUNDAY THROUGH THURSDAY... .Rest of Sunday...VFR. .Monday...VFR. .Monday night...Rain will attempt to develop resulting in MVFR or lower. If precipitation does develop, freezing rain is possible at Newburgh. .Tuesday...Rain with IFR. .Wednesday...MVFR possible. .Thursday...MVFR possible. && .MARINE... Light south flow this evening will turn to the NW behind a passing wave of low pressure and ahead of building high pressure later tonight and through Sunday. The winds increase late tonight and into Sunday before diminishing. At this time, expect winds to remain below 25 KTs, so no headlines planned. Seas through Sunday night remain 1 ft or less across the non ocean waters, and less than 3 feet across the ocean waters. SCA probable on the ocean Wed through Thu with otherwise sub SCA conditions expected for other marine area and for other time periods regarding the long term forecast marine period Mon through Thu. && .HYDROLOGY... No significant precipitation is forecast through the remainder of the weekend. No hydrologic impacts are expected. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...None. && $$ SYNOPSIS...JM/PW NEAR TERM...PW SHORT TERM...PW LONG TERM...JM AVIATION...JMC MARINE...JM/PW HYDROLOGY...JM/PW

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