Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 151809 AFDOKX Area Forecast Discussion National Weather Service New York NY 209 PM EDT Tue Aug 15 2017 .SYNOPSIS... A weak cold front approaches from the northwest, moving through tonight. High pressure builds from the northwest on Wednesday. The high will move offshore Wednesday night and Thursday, followed by a warm front moving north Thursday night into Friday. A slow moving cold front will approach from the west and pass through on Saturday. High pressure will build Saturday night into the beginning of next week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Made a few adjustments to forecast through early this evening. The first was to fine tune PoPs more in line with latest radar trends. Upper level jet streak to our north is providing lift along a stationary front to the south for a wave of showers, mainly to our south and west. The northern edge of these showers will clip portions of NE NJ, NYC, and Long Island this afternoon. Have confined highest PoPs across these locations, with a gradual trend down to slight chance across the north. The heaviest showers will likely remain offshore. Some of the latest mesoscale guidance is indicating some showers along the approaching weak front late this afternoon/early evening, but this may be overdone to due clouds lingering and preventing instability from being realized. Have also adjusted high temps down into the middle and upper 70s with clouds hanging on through much of the afternoon. A high rip current risk continues today for the Suffolk County ocean beaches. A moderate risk elsewhere to start should also become high late this afternoon as long period swells from Hurricane Gert begin to arrive. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM WEDNESDAY/... A weak frontal boundary approaching from the NW should move across late, with onshore flow turning SW this evening and then NW after midnight. Any remaining showers, mostly across Long Island/SE CT and also well inland, should end this evening, with dry conditions overnight and low temps in the 60s to lower 70s. As high pressure builds in on Wed, a drying downslope flow and mixing to 800-850 mb in the afternoon should lead to one of the warmer days so far this month, with highs in the upper 80s/lower 90s, at least a couple of degrees above the warmer of the GFS/NAM MOS guidance numbers. The deep mixing should also allow dewpoints to mix out to the upper 50s and lower 60s in most places by afternoon, keeping heat index values close to ambient temps. A high surf advisory may eventually be needed for the ocean beaches for Wednesday as the highest long period swells from Gert approach 7-8 ft. && .LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/... Long period south to southeast swells will likely be ongoing Wednesday night, and possibly into Thursday, as Gert tracks well east of the forecast waters. See the official NHC forecast for the track of Gert. The persistent longwave trough across eastern Canada will be exiting Wednesday night as the northern stream flow becomes more progressive with a series of shortwaves to affect the area Thursday into Saturday. A rather flat ridge will be left in the wake of the departing trough Thursday with surface high pressure over the area Wednesday night moving offshore Thursday. A return flow sets up ahead of the next system deepening across the upper midwest. There remains some uncertainty with the timing of the shortwaves moving across the northeast Thursday night into Saturday night. A warm frontal boundary approaches from the southwest Thursday night into Friday. With the associated low remaining well to the west, leaned toward a frontal passage during Friday. The area then becomes warm sectored and instability will be increasing, especially inland, away from a marine influence. With the series of shortwaves moving through the upper flow the surface low is slow to track east and northeast with the associated cold front also slow to move through. Timing at this time will be sometime Saturday. A little stronger ridge builds for Sunday into Monday as surface high pressure remains over the northeast. && .AVIATION /18Z TUESDAY THROUGH SUNDAY/...
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A weak cold front moves across late tonight with high pressure building in from the west Wednesday. Mainly MVFR conditions with rain showers for the rest of this afternoon into early evening. Patchy fog development occurs late tonight into early Wednesday reducing visibilities to MVFR and possibly IFR. There is uncertainty with this so amendments will certainly be possible to refine this timing. Winds less than 10 kt through the period. The wind direction is S-SE through the afternoon, variable tonight, but becoming more west to northwest overnight into daybreak Wednesday. NY Metro Enhanced Aviation Weather Support... Detailed information, including hourly TAF wind component forecasts, can be found at: http:/www.weather.gov/zny/n90 KJFK TAF Comments: IFR will be possible at times before 22Z. KLGA TAF Comments: IFR will be possible at times before 22Z. KEWR TAF Comments: IFR will be possible at times before 22Z. KTEB TAF Comments: IFR will be possible at times 19-22Z. KHPN TAF Comments: IFR will be possible at times 19-22Z. KISP TAF Comments: IFR will be possible at times before 22Z. .OUTLOOK FOR 18Z WEDNESDAY THROUGH SUNDAY... .Wednesday-Thursday...VFR. Late day sea breeze possible Wed. Widespread sea breezes Thu afternoon. .Thursday night through Saturday night...MVFR or lower flight cat possible in showers/tstms. .Sunday...VFR.
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&& .MARINE... SCA for hazardous seas over the ocean waters for tonight through Wed as long period swells from Hurricane Gert arrive and push seas to 5-7 ft. Conditions at the ocean inlets may become rough late this afternoon as the first sets of these swells arrive. Ongoing swell from hurricane Gert will maintain SCA level ocean seas through Wednesday night. See the official NHC forecast for the track of Gert. A slow moving frontal system will be moving through the waters late Thursday into the weekend. Conditions are expected to remain below small craft levels into the weekend. && .HYDROLOGY... No hydrologic impacts are anticipated from any showers that occur through this evening. A slow moving-frontal system may also bring periods of heavy rainfall Friday into Saturday. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...High Rip Current Risk until 9 PM EDT this evening for NYZ075- 080-081-178-179. NJ...None. MARINE...Small Craft Advisory for hazardous seas from 10 PM this evening to 6 PM EDT Wednesday for ANZ350-353-355. && $$ SYNOPSIS...Goodman/MET NEAR TERM...Goodman/DS SHORT TERM...Goodman LONG TERM...MET AVIATION...JM MARINE...Goodman/MET HYDROLOGY...Goodman/MET

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