Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 261635 AFDOKX Area Forecast Discussion National Weather Service New York NY 1235 PM EDT Sat May 26 2018 .SYNOPSIS... A cold front approaches from the north and drops south of the area tonight and early 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. && .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 will remain across portions of the area, mainly the southern half as temperatures were into the 80s, and near 90 across northeastern NJ, and dew points have risen into the mid and upper 60s. There is little forcing, and will be mainly with the weak shortwave later this afternoon, and with convection expected to develop along sea breeze boundaries. So have updated probabilities to adjust for area coverage and timing of expected convection development. Early this evening there likely will be break in precipitation, until the approach of the back door cold front. However, did not want to remove probabilities completely, and kept slight chance. 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/... 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. && .LONG TERM /MONDAY THROUGH FRIDAY/... 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. && .AVIATION /18Z SATURDAY THROUGH THURSDAY/... High pressure will move farther offshore today. A cold front will approach from the north late today into this evening. The cold front moves across late tonight. Mainly VFR through the TAF period, with SW flow gusting between 15- 20 kt this afternoon. Will have to watch for potential scattered late day (after 19Z) and evening tstms, especially at or invof the NYC metros, KHPN, and KISP, that could produce brief local vsby restrictions and gusty winds. Low confidence on timing and location of any thunderstorms that pop up and develop within the region. Late tonight is when rain will be likely. Widespread MVFR/local IFR ceilings will develop with winds becoming more E-NE. .OUTLOOK FOR 12Z SUNDAY THROUGH WEDNESDAY... .Sunday...Rain likely, especially in the morning, with widespread MVFR/local IFR cigs. ENE winds G20kt. .Sunday night...More widespread IFR cigs developing late at night, especially outside of the NYC metro area, where MVFR cigs may hang on. .Monday...MVFR cigs in the morning, then VFR. .Tuesday-Wednesday...VFR. && .MARINE... Conds will be fluctuating on the ocean waters through Sunday morning. with seas coming down from 5 ft initially out east, then possibly reaching 5 ft again this evening. A cold frontal passage tonight will be followed by ENE winds likely gusting to 25 kt and seas 5+ ft, both on the ocean. Hazardous ocean seas may linger into Monday. Decided to issue SCA through Sunday night to cover all these periods of elevated seas. && .HYDROLOGY... 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. && .TIDES/COASTAL FLOODING... 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. && .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... 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. && $$ SYNOPSIS...PW NEAR TERM...19/PW SHORT TERM...PW LONG TERM...12/PW AVIATION...Goodman/JM MARINE...Goodman/19 HYDROLOGY...PW TIDES/COASTAL FLOODING... EQUIPMENT...

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