Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 282020 AFDOKX Area Forecast Discussion National Weather Service New York NY 420 PM EDT THU JUL 28 2016 .SYNOPSIS...
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Low pressure approaches from the southwest tonight and passes through the region Friday. The low departs late in the day Friday with high pressure building to the north. Weak high pressure briefly builds into the region for parts of Saturday. Unsettled weather returns Saturday night through Sunday night with the passage of another low pressure system. Drier weather is expected for the first half of next week.
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&& .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
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A coastal trough remains along with a deepening low over Virginia. This low is associated with the vigorous shortwave moving through the northern trough over the eastern states. A combination of the deepening low and warm frontogenesis through southern NJ to south of Long Island 03z to 06z will bring increasing chances for showers, and with marginal instability thunderstorms. A deep layered southwest flow around sub tropical high pressure off southern coast and into the northern stream trough was transporting tropical moisture into the region. There will be potential for heavy rain developing later this evening and overnight as lift increases with the frontogenesis. A flash flood watch has been posted to this evening and into Friday.
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&& .SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/...
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Timing and tracking of the deepening low across the region during Friday is still somewhat uncertain, although there is now more consistency with the low tracking just south of Long Island Friday afternoon. Increasing shear along the warm front late tonight into Friday afternoon will increase the threat of severe storms across metro NYC, Long Island, and into coastal CT, along with continues heavy rainfall. Speed of the low has increased and precipitation is now expected to taper off from the west during the afternoon. Weak ridging builds behind the shortwave late Friday into Friday night with surface high pressure building from the northwest. Friday night will be dry with a cooler airmass moving into the area.
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&& .LONG TERM /SATURDAY THROUGH THURSDAY/...
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Weak high pressure will remain over the region Saturday morning, resulting in a dry Saturday morning. An approaching shortwave may set off a few scattered showers and thunderstorms Saturday afternoon, mainly west of NYC. East of NYC, conditions appear to remain mostly dry. The unsettled weather becomes more widespread Saturday night into Monday, as the shortwave and its associated low pressure system moves across the region. Expect showers and thunderstorms, through this time frame with some storms producing locally heavy rainfall. High pressure builds back into the region early next week, providing mostly dry conditions. A few isolated showers or thunderstorms cannot be ruled out during the first half of next week...mainly N and W of NYC during the afternoon hours. Temperatures will remain seasonable through the long term with highs each day climbing into the 80s.
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&& .AVIATION /20Z THURSDAY THROUGH TUESDAY/...
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High Impact Weather Forecast until 18z Friday... Low pressure is forecast to gradually intensify as it moves northeast across the area Friday. Widespread IFR conditions in heavy rain and fog with embedded thunderstorms are forecast north of the low`s track across the Lower Hudson Valley and CT, mainly between 06z and 16z Friday. There is a potential for thunderstorms with damaging wind gusts along and south of the lows` track along coastal NJ, NYC, and Long Island. Weather conditions improve from west to east 18z-23z Friday. NY Metro Enhanced Aviation Weather Support... Detailed information including hourly TAF wind component fcsts can be found at: http:/www.weather.gov/zny/n90 KJFK TAF Comments: G20kt possible 20Z-23Z. KLGA TAF Comments: Brief G15-18kt possible 21Z-23Z. KEWR TAF Comments: Slight chance of a TSTM aft 22Z. Brief G15-18kt possible 20Z-22Z. The afternoon KEWR haze potential forecast is green, which implies slant range visibility 7SM or greater outside of cloud. KTEB TAF Comments: Slight chance of a TSTM aft 22z. Brief G15-18kt possible 20Z-22Z. KHPN TAF Comments: No unscheduled AMD. KISP TAF Comments: No unscheduled AMD. .OUTLOOK FOR 18Z FRIDAY THROUGH TUESDAY... .Friday Afternoon...MVFR improving to VFR as rain ends west to east by 23z. .Friday night until Noon Saturday...VFR. .Saturday Noon into Monday Night...Chance of showers/tstms with MVFR or lower conds. .Tuesday...Mainly VFR.
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&& .MARINE...
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Winds and seas are expected to remain below small craft advisory levels tonight through Friday. A wave of low pressure is forecast to track through or near the waters Friday. Depending on the track of the low briefly higher winds and seas near small craft levels will be possible on the ocean waters east of Moriches Inlet. Showers and thunderstorms will be possible from this evening through Friday. Some of the thunderstorms Friday may produce gusty winds in excess of 35 KTS, especially over the ocean waters. At this time fog formation is not expected. A light pressure gradient over the area waters will result in sub- sca conditions this weekend and early next week. However, any thunderstorms that develop on the waters may produce brief SCA conditions.
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&& .HYDROLOGY...
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A flash flood watch is in effect for the entire CWA tonight through Friday for the potential of 2 to 4 inches with locally higher amounts. The axis of heaviest rain at this time is expected across northeastern New Jersey into the Lower Hudson Valley and NYC, and into southwestern Connecticut. Uncertainty remains as to where the heaviest rain occurs and depends on the track of low pressure through the region. Also, the speed of the low will affect the timing of precipitation. Another round of showers and thunderstorms can be expected Saturday night through Sunday...with some storms possibly producing heavy rainfall. Exact precipitation amounts are unclear at this time.
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&& .OKX WATCHES/WARNINGS/ADVISORIES... CT...Flash Flood Watch from 8 PM EDT this evening through Friday afternoon for CTZ005>012. NY...Flash Flood Watch from 8 PM EDT this evening through Friday afternoon for NYZ067>075-078>081-176>179. NJ...Flash Flood Watch from 8 PM EDT this evening through Friday afternoon for NJZ002-004-006-103>108. MARINE...None. && $$ SYNOPSIS...BC/MET NEAR TERM...MET SHORT TERM...MET LONG TERM...BC AVIATION...GC MARINE...BC/MET HYDROLOGY...BC/MET

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