Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 210744 AFDOKX Area Forecast Discussion National Weather Service New York NY 344 AM EDT Sun May 21 2017 .SYNOPSIS...
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High pressure moves east today. Thereafter, a series of weather systems impact the area through the week, resulting in unsettled weather.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Upper level ridge axis slowly moves overhead today. Surface high slides east of the area, offshore. Models in agreement in overall features, and expect a dry day today, with increasing mid and high level clouds. The clouds and southeast flow off the cool water will in result in cooler than normal temperatures, with 60s near the coast, and lower 70s across interior locations.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH MONDAY NIGHT/...
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Upper ridge axis passes east as closed upper low spins across the Great Lakes region. Low level southeast flow veers with height as deep southwest flow and warm air advection commences. The column saturates, as depicted in model plane views and time height cross sections, and expect showers to approach late tonight as lifts increases ahead of a warm front. Models indicate a piece of the upper low shears and moves northeast, with vigorous trough developing and amplifying across the mid west in time. The warm front Monday nears the area, but likely remains just south of Long Island as a wave of low pressure develops. Meanwhile the cold front slowly moves east across the area Monday night, with general model agreement on this occurrence. High coverage of showers is expected during the day Monday, with any showers passing east Monday evening. Will maintain slight chance for thunder, although instability is not too impressive according to both the NAM and GFS during the day Monday. The showers could be heavy at times with gulf moisture tapped, and precipitable water of around one and a half inches progged. With the onshore flow, clouds and rain, expect cooler than normal temperatures, 40s and 50s tonight, 60s during the day Monday, and 40s/50s again Monday night.
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&& .LONG TERM /TUESDAY THROUGH SATURDAY/...
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The developing and anomalous deep upper trough over the central U.S. will move slowly east through the week, resulting in unsettled weather through the period as a series of lows/upper level vorts move through bringing multiple chances for rain to the region. Tuesday, possibly into Tuesday night, will be the most likely time for dry weather as weak sfc high builds, and upper level shortwave remains well upstream. Then some differences begin to emerge in the models as the trough amplifies over the midwest and southern plains. This results in differences in the timing and location of the resulting shortwaves and associated sensible weather. Kept PoPs at chance during Wednesday, with likely PoPs Thursday as the trough draws near. Do expect another round of rain during the midweek time period. The trough finally begins to exit to the east on Friday as a ridge builds in from the west, with only a few lingering showers by late Friday into Saturday. Temperatures should moderate to near normal for the remainder of the week.
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&& .AVIATION /07Z SUNDAY THROUGH THURSDAY/... VFR forecast through the TAF period. High pressure moves offshore today as a frontal system approaches from the west. Winds will once again be the challenge today. Light S winds continue at the metro terminals...vrb to calm elsewhere. The S winds are expected to back to the SE by 09z with a E-NE flow developing around 12z for a few hours...then veer back to the SE 10-15 kt mid to late morning. Timing of all these shifts could be +/- 1-2 hours...however speeds will be less than 10 kt until mid-late morning. Gusts don`t appear likely at KJFK/KISP/KBDR/KGON where temps will be cooler with the onshore flow. However warmer locations are expected to gust up to 20kt this aftn. .OUTLOOK FOR 06Z MONDAY THROUGH THURSDAY... .SUNDAY NIGHT-MONDAY...VFR tonight lowering to IFR on Monday in showers. Slight chance of thunderstorms on Monday. .MONDAY NIGHT-TUESDAY...Becoming VFR. .WEDNESDAY-THURSDAY...Chance of MVFR or lower in showers. Slight chance of thunderstorms Wednesday night into Thursday. && .MARINE...
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Sub-advsy conds will remain across the waters through tonight as high pressure gradually slides off the New England coast. SE winds will increase on Monday as the pressure gradient tightens. A 30-40 kt LLJ will also track across the waters on Monday...however a sfc inversion will keep most of these winds from mixing down. Gusts could approach SCA levels...but not thinking they will reach 25 kt attm. Seas on the ocean could also reach marginal SCA levels Monday night. Since this is a marginal 4th period event will hold off on issuing any headlines at this time. Winds and seas then remain below SCA conditions until mid-late week when seas begin to increase ahead of the next system.
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&& .HYDROLOGY...
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Widespread one half to one and a half inches of rainfall accumulation on Monday could result in minor poor drainage/urban flooding.
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&& .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...None. && $$ SYNOPSIS...PW NEAR TERM...PW SHORT TERM...PW LONG TERM...FEB/PW AVIATION...24 MARINE...24 HYDROLOGY...PW

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