Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 151357 AFDOKX Area Forecast Discussion National Weather Service New York NY 957 AM EDT Tue Aug 15 2017 .SYNOPSIS... A warm front will remain south of Long Island today, while a weak cold front approaches from the northwest. This weak front will move across tonight, followed by high pressure building 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/... Brief lull in showers this morning will come to end by late this morning and early afternoon as a second upper jet streak passes to the north. The best chance at showers appears to be across the south where the best lift will be confined. Have removed mention of thunder as any instability is weak. The last few runs of the HRRR have shifted the axis of most widespread showers south of Long Island, and latest radar trends appear to be heading this way as well. Will continue to monitor trends through the morning, but some briefly moderate showers are possible across Long Island with the second round of showers. The most widespread showers, associated with an offshore warm front and tropical moisture will remain well south of Long Island and NYC. High temps should be in the upper 70s and lower 80s per guidance blend. 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 MONDAY/... 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 /14Z TUESDAY THROUGH SATURDAY/... Weak low pressure passes to the south today while a cold front approaches. The cold front weakens as it passes through tonight. Overall confidence of forecast is moderate. Category will be mainly VFR today but could lower to MVFR this afternoon with shower development. The showers could extend into early this evening. Otherwise, VFR continues tonight with a chance for some light fog late into early Wednesday with possible MVFR conditions. Winds should remain under 10 kt all day, primarily SE. Winds become light (less than 5 kt) and variable tonight. 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: MVFR could prevail instead of tempo this aftn. The afternoon KJFK haze potential forecast is GREEN...which implies slant range visibility 7SM or greater outside of cloud. KLGA TAF Comments: MVFR could prevail instead of tempo this aftn. The afternoon KLGA haze potential forecast is GREEN...which implies slant range visibility 7SM or greater outside of cloud. KEWR TAF Comments: MVFR could prevail instead of tempo this aftn. The afternoon KEWR haze potential forecast is GREEN...which implies slant range visibility 7SM or greater outside of cloud. KTEB TAF Comments: MVFR could prevail instead of tempo this aftn. KHPN TAF Comments: MVFR could prevail instead of tempo this aftn. KISP TAF Comments: MVFR could prevail instead of tempo this aftn. .OUTLOOK FOR 14Z WEDNESDAY THROUGH SATURDAY... .Wednesday thru Thursday...VFR. .Thursday night through Saturday...MVFR or lower flight cat possible, with chance of showers and tstms. && .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... Rainfall amounts with a second round of showers, mainly across NE NJ, NYC, and Long Island late this morning into the afternoon will be light and generally under 1/4 inch. No hydrologic impacts are anticipated. 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...JC/JM MARINE...Goodman/MET HYDROLOGY...Goodman/MET

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