Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 231821 AFDOKX Area Forecast Discussion National Weather Service New York NY 221 PM EDT Sun Jul 23 2017 .SYNOPSIS... A frontal boundary remains to our south today. Low then moves along the front, tracking off the mid-Atlantic coast Monday. High pressure builds over the northeast late Tuesday through Wednesday, then drifts off the coast Wednesday night. Another wave of low pressure follows for Wednesday night into Friday, with a cold front moving through Friday. High pressure returns Saturday. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... As of 1240 pm, showers were developing over the New York City metro area, generally along the sea breeze. Convergence along this boundary has provided enough lift for these showers to develop. Additionally, light showers from the northwest have made their way into portions of the Lower Hudson Valley and are headed for portions of southwest Connecticut. Therefore, have added a slight chance for showers for New York City, northeast New Jersey, the Lower Hudson Valley, Nassau County, and southwest Connecticut. The threat for these showers should continue for the afternoon. Initial shortwave passes to the east early this morning, with a wave of low pressure doing the same. High pressure, with weak ridging aloft, builds across New England. Other than an isolated shower, subsidence behind shortwave will likely keep the area dry today. Some sunshine will appear, particularly in southern CT. Temperatures today will be cooler, closer to seasonal norms of the lower to mid 80s. There is a moderate risk for the development of rip currents at ocean beaches today. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/... Weak ridge yields to approaching trough through this time frame. At the sfc, two areas of low pressure approach and pass. the area looks to remain on the north side of the frontal boundary as the coastal low passes juts south Monday. Ample forcing ahead of this system will result in increasing coverage for showers and possible thunderstorms tonight, from west to east. Best chance occurs from late evening and through the overnight hours. At this time, instability appears to be weak, so widespread thunder is not anticipated. On Monday, showers are possible, but the main area in the morning departs in the afternoon. For tonight, the rain and clouds will result in normal overnight low temps. However, cool temperatures are anticipated during the day Monday. With easterly flow, and plenty of clouds, leaned toward the lower end of the guidance, with a 2/3 and 1/2 blend followed. && .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/... An upper level shortwave and accompanying wave of surface low pressure will be exiting to the east Monday night into early Tuesday. A few showers will be on-going at the beginning of the extended forecast period. CAPE values look meager. A weak ridge builds Tuesday and Wednesday. Then another shortwave amplifies into a significant trough into the eastern states Wednesday night into Thursday with a high amplitude trough, of 1 to 2 standard deviations above normal, digging all the way to northern Florida by Friday. The flow looked to be still progressive with a surface low moving through Thursday and Friday. However, there are hints that the upper low will close off again Friday into Saturday and remain along the northern coast into next weekend. At this time will keep with persistence and the more progressive flow and keep Friday night into Saturday dry as upper ridging builds to the north. Temperatures through the extended period will be near to slightly below seasonal normals. && .AVIATION /18Z SUNDAY THROUGH FRIDAY/...
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A stationary front will remain to our south into Monday morning, with a wave of low pressure moving along it towards the region tonight, then passes to the south into Monday afternoon. Conditions mainly VFR at area terminals early this afternoon, except localized MVFR at LGA. Could see some variability down to MVFR at other coastal/city terminals for the remainder of this afternoon, with conditions becoming MVFR throughout by late evening/early morning, with showers overspreading the area after midnight. An isolated rumble of thunder cannot be ruled out during the overnight hours as well, with the best chance from the city terminals on N/W. IFR conditions are probable by around sunrise, then should improve back to MVFR by mid morning. Isolated gusts to around 15kt are possible this afternoon. Winds become E throughout overnight at around 10-15kt. Gusts to around 15-20kt are probable overnight for CT/Long Island Terminals/KLGA and briefly at KJFK. Widespread 15-20kt gusts are probable throughout by mid Monday morning, as the winds back to the NE. .OUTLOOK FOR 18Z MONDAY THROUGH THURSDAY... .Monday afternoon-Tuesday...MVFR likely. IFR, NE-E winds G15-25KT and isolated-Scattered showers are possible. .Tuesday night...MVFR likely. IFR and NE winds G15-25KT are possible. .Wednesday-Thursday...VFR. There is a chance of showers and possibly a thunderstorm mainly to the N/W of city terminals Thursday afternoon. .Thursday night-Friday...MVFR or lower conditions and isolated to scattered showers and thunderstorms are possible.
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&& .MARINE... Increasing E-SE flow tonight and then E-NE flow on Monday ahead of an approaching low, with a warm front remaining to the south or only briefly entering the ocean waters, should eventually build ocean seas to minimal SCA criteria of 5 ft. This could happen in the NY Bight area as early as late tonight, but certainty in this is higher for daytime Monday. Wind gusts up to 25-30 kt are also possible on the eastern ocean/sound/bay waters daytime Monday. Ocean seas may also approach 5 ft Wed night-Thu as increasing S flow develops ahead of a cold front. Waves of low pressure passing through could also bring a chance of tstms on Thu. && .HYDROLOGY... An additional 1/2 to 1 inch of rainfall is likely from late tonight through Monday, with locally higher amounts possible. There is a small chance for minor flooding or urban and poor drainage areas, if any experience locally heavy rainfall. More rain is possible Thursday through Friday. Significant hydrologic impacts are not expected at this time. && .TIDES/COASTAL FLOODING... With the new moon phase today, tides are running high. Positive tidal departures of 1/2 to 1 ft are needed for minor flooding during the night time high tide. With east flow expected, and looking at what occurred earlier tonight, will issue a coastal flood advisory for western LI sound, the south shore bays of LI, and lower NY Harbor for the evening and night time high tides. A few locations could reach or slightly exceed moderate benchmarks across the south shore bays of Nassau and Queens. The threat for minor flooding could continue into Monday, with E/NE flow progged to continue. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...Coastal Flood Advisory from 11 PM this evening to 2 AM EDT Monday for CTZ009. NY...Coastal Flood Advisory from 11 PM this evening to 2 AM EDT Monday for NYZ071-073-176-177. Coastal Flood Advisory from 8 PM to 11 PM EDT this evening for NYZ074-075-178-179. NJ...None. MARINE...None. && $$ SYNOPSIS...PW NEAR TERM...JP/PW SHORT TERM...PW LONG TERM...MET/PW AVIATION...Maloit MARINE...PW HYDROLOGY...PW TIDES/COASTAL FLOODING... is the U.S. government's official web portal to all federal, state and local government web resources and services.