Area Forecast Discussion
Issued by NWS Upton, NY

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996 FXUS61 KOKX 201123 AFDOKX Area Forecast Discussion National Weather Service New York NY 723 AM EDT Wed Jun 20 2018 .SYNOPSIS... High pressure retreats to the east, as an area of low pressure riding along a stalled frontal boundary tracks from the Ohio River Valley today to near the Mid-Atlantic Coast by Thursday morning. This low exits to the east on Thursday as a separate cold front pushes to our south, followed by weak high pressure building over the region into Friday. A frontal system will slowly approach the area on Friday, as the high retreats to the northeast, and then impacts the region over the weekend. High pressure will build in behind the system into next Tuesday. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Clouds were increased this mrng based on stlt, otherwise the fcst is on track. WNW flow aloft this morning, flattens as a northern stream shortwave approaches from the west this afternoon. There could be some stray showers by late afternoon as the shortwave approaches, mainly across far western zones. Highs today should be near normal, mainly from the mid 70s to around 80 across the region. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/... A northern stream trough builds into the area tonight, this coupled with some low level instability (focused mainly over the southern 1/2 of the CWA) should bring some showers to the region tonight, and possibly a rumble of thunder as well (mainly to the southern 1/2 of the CWA). Precipitable Waters increase to from 1.75 to around 2 inches (with values around 2 inches focused over the southern 1/2 of the CWA), so locally heavy rainfall is possible, especially in association with any stronger convection overnight. Refer to the hydrology section of the AFD for details on expected rainfall amounts and any impacts. There is some uncertainty on the timing of the showers tonight, but for now a consensus timing would be for the most numerous showers and best chance for any locally heavy rainfall to occur from around 9pm- 5am. The timing for the end of the rainfall has slowed, with showers now expected to linger into Thursday morning. The showers likely should come to an end by mid-late morning, as the axis of the northern stream trough exits to the east, allowing for a drying NW flow to set up over the region by afternoon. Lows tonight and highs on Thursday should be near to slightly above normal. && .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/... The models are in good agreement with the general pattern in the long term, although some timing and placement issues remain. An approximately 1020 hi will be set up from the Maritimes swwd to cntrl New England Fri. At the same time, sw flow aloft develops as an h5 low spins over the Midwest. This will result in increasing thetae and chcs for shwrs and tstms Fri and particularly Fri ngt. The upr support arrives Sat and Sat ngt. The GFS is a bit faster than the ECMWF. Likely pops have been included during the day on Sat based on a blend of all of the model data. As the upr trof arrives on Sun and Mon, there will be additional chances for pcpn. These appear to be a bit more diurnally focused, with daytime heating providing the added instability boost needed. High pres then builds in on Tue and dries out the area. The NBM was used for temps thru the period. && .AVIATION /12Z WEDNESDAY THROUGH SUNDAY/...
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High pressure will be over the region today, then weak low pressure passes through or nearby the area tonight. VFR today, then mostly MVFR tonight in -shra/-ra. Light and variable winds with an easterly component shifts SE-S this morning, increasing to around 10 kt by noon. ...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: Timing of wind shift to S could be off by 1-2 hours. The afternoon KJFK haze potential forecast is GREEN...which implies slant range visibility 7SM or greater outside of cloud. KLGA TAF Comments: Timing of wind shift to S could be off by 1-2 hours. The afternoon KLGA haze potential forecast is GREEN...which implies slant range visibility 7SM or greater outside of cloud. KEWR TAF Comments: Timing of wind shift to SE could be off by 1-2 hours. The afternoon KEWR haze potential forecast is GREEN...which implies slant range visibility 7SM or greater outside of cloud. KTEB TAF Comments: Timing of wind shift to S could be off by 1-2 hours. KHPN TAF Comments: Timing of wind shift to SE then S could be off by 1-2 hours. KISP TAF Comments:Timing of wind shift to S could be off by 1-2 hours. .OUTLOOK FOR 12Z THURSDAY THROUGH SUNDAY... .Thursday...MVFR early with showers ending, then becoming VFR. .Friday...VFR. .Saturday...A chance of showers, possibly a thunderstorm, Sat into Sat night. .Sunday...VFR expected. Slight chc of a shower.
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&& .MARINE... A relaxed pressure gradient over the waters will generally limit winds to around 10 kt or less through Thursday. The possible exception is over the coastal ocean waters west of Moriches Inlet this afternoon and evening, where sustained winds up to around 15 kt are possible. Winds and seas will remain below Small Craft Advisory (SCA) levels Thu night, then increase to SCA levels, mainly on the ocean, Fri thru Sun. && .HYDROLOGY... Dry this morning. Then expect around 1/4 to 1 inch of basin average rainfall from this afternoon into Thursday morning. The lowest amounts will be across northern interior portions of the Tri-State and heaviest amounts across NYC/Long Island and NE NJ. With very high precipitable waters forecast, there is the potential for locally heavy rainfall with any stronger convection. Areas experiencing locally heavy rainfall could experience minor flooding of mainly urban and known poor drainage areas. There is also a very small (generally around 10% or less) of localized flash flooding, with the highest potential (around 10%) across NYC/NE NJ/Long Island. No significant widespread hydrologic impacts are currently expected from Thursday afternoon through Tuesday. && .EQUIPMENT... NYC NOAA Weather Radio Station KWO-35 (162.55 MHz) remains off the air for an extended period of time. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...None. && $$ SYNOPSIS...JMC/Maloit NEAR TERM...JMC/Maloit SHORT TERM...Maloit LONG TERM...JMC AVIATION...JC MARINE...JMC/Maloit HYDROLOGY...JMC/Maloit EQUIPMENT...

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