Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 211743 AFDOKX Area Forecast Discussion National Weather Service New York NY 143 PM EDT Sun May 21 2017 .SYNOPSIS... High pressure moves east of the area today. A series of low pressure systems impact the area through the week, resulting in unsettled weather. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Under full sun, temps cont to rise higher than fcst...approaching 70 degs in Metro NYC/NJ. Updated the sky cover and temp fcsts to reflect current observations and near term forecast trends. Otherwise...Models in agreement in overall features. Clouds will slowly advect east aft 18z across Northern NJ and aft 21z across NYC. Southeast winds off the cool water will in result in cooler than normal temperatures along the coast. && .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 /18Z SUNDAY THROUGH FRIDAY/...
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High pressure moves offshore today as a frontal system approaches from the west. VFR through at least 06z tonight. S-SE winds 8-15 kt this afternoon. Winds gradually diminish overnight, and remain from the SE. Some gusts may be possible through 23Z, however they may be more occasional than frequent. Clouds lower and thicken this evening and overnight...but rain and MVFR conditions look to hold off until around daybreak. IFR conditions expected to develop after 12z. There may be some embedded thunder with the rain on Monday. Confidence on timing and placement is too low to include in the TAFs at this time. .OUTLOOK FOR 18Z MONDAY THROUGH FRIDAY... .MONDAY Afternoon...IFR in rain. Slight chance of thunderstorms. .MONDAY NIGHT-TUESDAY...Cold frontal passage around midnight Monday night at the metros. Becoming VFR Tue morning. .WEDNESDAY-FRIDAY...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...GC SHORT TERM...PW LONG TERM...FEB/PW AVIATION...BC MARINE...24 HYDROLOGY...PW

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