Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 291426 AFDOKX Area Forecast Discussion National Weather Service New York NY 1026 AM EDT Mon May 29 2017 .SYNOPSIS... A low pressure system approaches passes through into this evening. A weak cold front approaches from the west Tuesday, then crosses the area Tuesday night...followed by another on Wednesday. High pressure then builds to the south through Thursday night. Another cold front approaches on Friday then slowly crosses the area Friday night. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Two vorticity maximums ahead of a broader upper low to the west are influencing the development of showers across the area this morning. Localized brief moderate to heavy rainfall will be possible as another round moves across NJ into portions of southern NY/CT including Long Island, evident in upstream observations and given convective appearance on satellite. Showers gradually taper off from west to east by evening, though with onshore flow expect a continuation of patchy drizzle and fog. Unseasonably cool temperatures today as clouds and rain keep temperatures in the upper 50s to around 60 for highs, some 10 to 15 degrees below normal. There is a moderate risk of rip currents for area beaches.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/...
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Frontal system pushes east of the area tonight, along with the coastal storm. After some lingering showers early this evening, conditions should remain dry. However, drizzle and fog may persist overnight, with low level moisture trapped under an inversion. Another front approaches slowly from the west. Chances for rain increase from west to east during the day Tuesday. Enough instability for some thunder, but nothing severe expected. Temperatures continue to be below normal.
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&& .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... The models continue to have differences in how they handle the very broad closed low that will be over SE Canada Tuesday Night through Thursday night. As a result they also differ in the strength and timing of shortwaves rotating around the base of the low, and hence on the precise timing of precipitation during this time frame. However, do have likely pops in for Tuesday night, as the models do agree there should be some measurable rainfall across the region then, but do have differences in timing during the night. Lows Tuesday night should be a few degrees above normal. For Wednesday and Wednesday night have mainly chance pops across northern zones and slight chance pops across southern zones. With Showalter Indices progged to 0 to -2, also have a slight chance of thunder in for Wednesday afternoon and evening. Highs Wednesday and lows Wednesday night should be a few degrees above normal as well. Zonal flow sets up Thursday and Thursday night, and it appears the region and with significant shortwaves progged to the NE and NW during this time frame, have gone with a dry forecast then. The model differences become even more noticeable Friday-Saturday. For Friday, do have chance pops throughout by afternoon and continue through Friday evening (along with a slight chance of thunder). Then limit pops to slight chance from late Friday night-Saturday morning. Then go with a dry forecast Late Saturday/Saturday night as both the GFS and ECMWF show the core of the closed low to the NE then. The new ECMWF has joined the 00z GFS in keeping Sunday dry, but noting it previously had a coastal low approaching (now just suppressed farther S), do have slight chance pops for Sunday. Temperatures Thursday through Saturday night will feature near normal highs and lows a few degrees above normal. Highs Sunday are currently forecast to be a few degrees below normal. && .AVIATION /14Z MONDAY THROUGH FRIDAY/... A weakening frontal system will approach from the west, while low pressure passes off to the southeast today. The area will be between the two systems, under an area of weak high pressure. This will result in widespread clouds and periods of light rain and/or drizzle. Expect widespread MVFR cigs through this evening, with local IFR at KHPN. Showers moving in from the west could bring tempo IFR vsby to the NYC metros toward midday, with thunder chances nil as instability off to the west weakens. Thereafter could see tempo IFR cigs at any time from mid afternoon into the evening, but the main push for IFR cigs looks to be after midnight tonight. High confidence in E to ENE winds 8-15 kt this morning, diminishing to 10 kt or less this afternoon. Confidence still only medium at best on wind direction this evening, which could range anywhere from NW to SE, but speeds should be light. NY Metro Enhanced Aviation Weather Support... Detailed information, including hourly TAF wind component fcsts, can be found at: http:/www.weather.gov/zny/n90 KJFK TAF Comments: High confidence in winds through this afternoon. Low chance of IFR cigs developing as early as late this afternoon. KLGA TAF Comments: High confidence in winds through this afternoon. Low chance of IFR cigs developing as early as late this afternoon. KEWR TAF Comments: High confidence in winds through this afternoon. Low chance of IFR cigs developing as early as late this afternoon. The afternoon KEWR haze potential forecast is YELLOW, which implies slant range visibility 4-6SM outside of cloud. KTEB TAF Comments: High confidence in winds through this afternoon. Low chance of IFR cigs developing as early as late this afternoon. KHPN TAF Comments: High confidence in winds through this afternoon. KISP TAF Comments: High confidence in winds through this afternoon. Low chance of IFR cigs developing as early as late this afternoon. .OUTLOOK FOR 12Z TUESDAY THROUGH FRIDAY... .Tuesday...IFR to start, improving to MVFR/VFR by afternoon. Chance of an afternoon shower or tstm from NYC metro NW, but mainly at KSWF. .Tuesday night...Low clouds with IFR conditions. Showers also likely, possibly a tstm. .Wednesday...IFR to start, improving to VFR by afternoon. Chance of showers and possibly a tstm from the NYC metro terminals NW. .Wednesday night and Thursday...VFR. .Friday...Afternoon/evening showers/tstms possible with MVFR or lower conds. && .MARINE...
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SCA in effect today with seas 4 to 7 ft. Increased seas slightly to account for current trends, though seas will slowly begin to subside below SCA levels tonight. A relaxed pressure gradient over the region from Tuesday night into Friday should keep sustained winds over the waters around Long Island to around 10 kt or less during this time frame. The pressure gradient is currently forecast to tighten a tad later on Friday, with sustained winds of around 15 kt or less possible over the waters then. Given the relatively light winds, and no significant swell, sub Small Craft Advisory conditions are forecast Tuesday night- Friday.
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&& .HYDROLOGY...
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0.25"-0.50" expected through today, with isolated higher amounts possible across southeastern NY. This should have no hydrologic impact. No significant widespread hydrologic impacts are then expected at this time from Monday night through at least Thursday night.
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&& .TIDES/COASTAL FLOODING... Additional minor coastal flooding may occur with the high tide cycle tonight...mainly for the southern bays of Nassau/NYC. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...Small Craft Advisory until 11 PM EDT this evening for ANZ350- 353-355. && $$ SYNOPSIS...Maloit/JP NEAR TERM...MD/Maloit/JP SHORT TERM...JP LONG TERM...Maloit AVIATION...Goodman/DW MARINE...Maloit/JP/MD HYDROLOGY...Maloit/JP TIDES/COASTAL FLOODING...

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