Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 211138 AFDOKX Area Forecast Discussion National Weather Service New York NY 738 AM EDT Sun May 21 2017 .SYNOPSIS... High pressure moves east today. Thereafter, a series of weather systems impact the area through the week, resulting in unsettled weather. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Forecast generally on track. Updates to reflect latest trends early this morning. 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. && .SHORT TERM /6 PM THIS EVENING THROUGH MONDAY NIGHT/... 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. && .LONG TERM /TUESDAY THROUGH SATURDAY/... 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. && .AVIATION /12Z SUNDAY THROUGH THURSDAY/...
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High pressure moves offshore today as a frontal system approaches from the west. VFR through at least 06z tonight. Light/vrb winds will give way to a light E-NE flow for a few hours this morning...which then veer to the SE 10-15 kt mid to late morning. Timing of the shift to the SE could be +/- 1-2 hours. Winds aloft look too strong for seabreeze development this aftn. 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. Winds then diminish below 10 kt this eve. Clouds lower and thicken this eve and overnight...but rain and MVFR conds look to hold off until around daybreak. IFR conds expected to develop aft 12z. .OUTLOOK FOR 12Z MONDAY THROUGH THURSDAY... .MONDAY...IFR with showers. Slight chance of thunderstorms on Monday. .MONDAY NIGHT-TUESDAY...Cold fropa around midnight Mon night at the metros. Becoming VFR Tue morning. .WEDNESDAY-THURSDAY...Chance of MVFR or lower in showers. Slight chance of thunderstorms Wednesday night into Thursday.
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&& .MARINE... 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. && .HYDROLOGY... Widespread one half to one and a half inches of rainfall accumulation on Monday could result in minor poor drainage/urban flooding. && .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 is the U.S. government's official web portal to all federal, state and local government web resources and services.