Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 260759 AFDOKX Area Forecast Discussion National Weather Service New York NY 359 AM EDT Sat May 26 2018 .SYNOPSIS...
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A cold front approaches from the north and drops south of the area tonight and Sunday. The front becomes nearly stationary south of the waters through Memorial Day. Another cold front will move through from the north on Tuesday, followed by high pressure building in through the middle of next week. A storm system should then impact the region for the end of next week.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Weak upper trough approaches as large ridge builds to the north across Hudson Bay. At the surface, large western Atlantic ridge drifts east, with sfc high well north in Canada pushing a backdoor cold front southward toward the area today. Moderate/marginal instability builds today across portions of the area, but lack of forcing other than sea breeze boundaries should limit shower/thunderstorm development this afternoon to isolated or at most scattered coverage. Under partly to mostly sunny skies, temperatures should soar well into the 80s, likely reaching 90 in spots away from the coasts. 70s near the coast expected. There is a moderate risk for rip currents today at area Atlantic Beaches.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH SUNDAY NIGHT/...
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With the approach of weak trough, and the passage of a back door front that is progged to move south of the region from high pressure to the north, shower and thunderstorm coverage will increase tonight. Some convection could produce heavy downpours, and ample instability is present, along with lift/low level convergence for thunder. Many forecast stability parameters suggest scattered thunderstorm coverage initially. As the night progresses, atmosphere becomes capped, so thunder chances diminish late at night and into Sunday. The backdoor front does settle to the south, and approaching upper trough should result in weak cyclogenesis along the front to the south later Sunday. Warm temperatures tonight ahead of the front will abruptly tumble behind the front as winds shift to the northeast. Expect frontal passage across CT zones first, then southwestward across NYC/NE NJ toward 10Z. Will follow ARW/NMM/namwrf with front timing, and lean toward cooler overnight lows, closer to MET numbers as temps fall late at night. On Sunday, cloudy skies, E/NE flow and fairly high coverage for showers will result in much cooler temps. Will once again lean or blend cooler MET numbers, just feel namwrf has a better handle on this shallow cool air behind the backdoor front.
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&& .LONG TERM /MONDAY THROUGH FRIDAY/...
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As the wave of low pressure departs to the east, shower chances diminish Sunday night. High pressure looks to produce dry weather beginning Monday. The guidance has trended up with temperatures as a result. A warmup on Tuesday as upper level ridging builds in, but a backdoor cold front comes through during the day. Forecast has been kept dry, as GFS in better agreement with consensus. High pressure and dry weather on Wednesday, then a warm front and possible low pressure system for late Thursday and Friday. Chances for showers and thunderstorms have been included in the forecast. There could be a connection to Alberto moisture, so if this does occur, locally heavy rain will be possible.
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&& .AVIATION /08Z SATURDAY THROUGH WEDNESDAY/... High pressure will move further offshore tonight into Saturday. A back door cold front approaches late Saturday and moves through Saturday night. Mainly VFR through the TAF period. SW winds will continue to diminish below 10 kt tonight and become light and variable outside of city terminals. SW winds will increase in the morning and afternoon to around 10 kt on Saturday. There is a chance of thunderstorms late Saturday afternoon into Saturday evening, mainly from NYC terminals on north and west. Showers become more likely after 00z with possible MVFR. .OUTLOOK FOR 00Z SUNDAY THROUGH WEDNESDAY... .Saturday Night...Showers likely with a chance of thunderstorms. MVFR developing late. .Sunday...IFR in the morning, becoming MVFR in the afternoon. Showers likely through early afternoon. .Monday...MVFR possible. .Tuesday-Wednesday...VFR. && .MARINE... Minor changes were made with this update to reflect the latest trends in observations and guidance. The forecast appears on track. Sub-Small Craft Advisory (SCA) conditions are expected on all waters around Long Island overnight, with winds generally 10 kt or less on the non-ocean zones and 15 kt or less on the coastal ocean waters (with gusts up to around 20 kt). Saturday and Saturday night winds and seas will remain below small craft levels with a weak surface pressure gradient force. Winds are expected to remain below SCA levels Sunday-Wednesday. 5 ft seas are possible from Sunday into Monday on the ocean with NE flow. && .HYDROLOGY...
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Rainfall amounts this weekend could vary quite a bit across the area, but generally expect up to an inch near the coast, with much less possible across the interior locations through the weekend. Cannot rule out minor urban and poor drainage flooding, mainly tonight into Sunday morning. No significant hydrologic impacts are anticipated Sunday night- Thursday. There is a low potential for locally heavy rain from Thursday night through Friday.
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&& .TIDES/COASTAL FLOODING...
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Water levels may be near minor flood thresholds along the south shore back bays of Nassau County and in western Long Island Sound with the Sunday late afternoon and evening high tide cycle. Forcing for increased water levels will be increasing E-NE flow as a front stalls to the south and strong high pressure sets up E of New England, along with increasing astronomical high tides with the full moon on Tue the 29th.
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&& .EQUIPMENT... NYC NOAA Weather Radio Station KWO-35 (162.55 MHz) is off the air for an extended period of time. && .OKX WATCHES/WARNINGS/ADVISORIES...
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CT...None. NY...None. NJ...None. MARINE...Small Craft Advisory from noon Sunday to 6 AM EDT Monday for ANZ355. Small Craft Advisory until 6 AM EDT Monday for ANZ350-353.
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&& $$ SYNOPSIS...PW NEAR TERM...PW SHORT TERM...PW LONG TERM...12/PW AVIATION...Goodman MARINE...Goodman HYDROLOGY...PW TIDES/COASTAL FLOODING... EQUIPMENT...

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