Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 161300 AFDOKX Area Forecast Discussion National Weather Service New York NY 900 AM EDT Thu Aug 16 2018 .SYNOPSIS... Weak high pressure remains south of the area through tonight as a backdoor front approaches tonight and lifts back to the north Friday. A cold frontal passage on Saturday will usher in high pressure through Monday. A frontal system may bring active weather late Tuesday and Wednesday. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... The fcst is on track this mrng. Ridge in place today and associated subsidence will result in partly to mostly sunny conditions. Westerly wind flow will allow for warm to hot temperatures across the entire region, even coastal locations will warm well into the 80s to near 90. The westerly flow however will mix out dew points, keeping humidity levels down somewhat. As such, will maintain the heat advisory for the metropolitan area where temperatures remain warmer in the lower to middle 90s. Any isolated showers or thunderstorms should remain to our west. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM FRIDAY/... Upper ridge slides to the east as upstream shortwave slowly approaches this time frame. At the sfc, a backdoor cold front should sag south across portions of the area, mainly SE CT and perhaps the twin forks of Long Island. Partly cloudy skies are anticipated, and temperatures will remain quite warm. Lows will range from the upper 60s to the upper 70s in NYC. On Friday, clouds will be on the increase, and shower and thunderstorm chances will increase, mainly from west to east. Although a few thunderstorms may develop just north of the area along the weakening back door front that washes out, or lifts to the north as a warm front. Feel the bulk of the thunderstorm activity holds off until late in the day, mainly across western locations. With increasing clouds, temps warm, but not quite as high, peaking around 90. However, increasing southerly flow ahead of a prefrontal trough will allow dew points to rise into the 70s. This will create heat indices in the lower to mid 90s across the advisory area. Will thus maintain the heat advisory for the same locations. There will likely be a moderate risk for rip currents on Friday. && .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... A cluster of tstms associated with a prefrontal trof are expected to roll across the area Fri ngt. It looks like the main challenge will be whether the forcing from ongoing convection along with the trof will be sufficient to keep the tstms robust as they encounter increasing cin. The NAM suggests the answer is yes, and based on the model`s recent track record with tstms recently, this soln has been accepted. Some svr activity cannot be ruled out with strong sly bl flow, llvl veering and cape over 2000. Progged lcls are blw 1000 ft as well. There should be a window Sat mrng with no activity before the next round of tstms with the fropa. Amount of convective debris will have an impact on destabilization, so if there is much less convection Fri ngt than expected, the svr threat could be a bit better on Sat. For now it is too far out to really have a solid handle on the environment, and without that it is pure speculation. Winds become nely behind the front late Sat, and dry wx is then ushered in for Sun and Mon. High temps both days slightly blw avg. The modeling shows some sct-isold shwrs on the periphery of the high, but with the cwa progged to remain right in the sfc ridge axis, the fcst has been kept dry. Any change in this setup could result in some sct aftn shwrs across the area. The next sys gets here for the middle of the week. After a surge of warm air, a much cooler airmass flows in behind a substantial cold front. 540 thicknesses are showing up on the maps with this one, although whether they end up in nrn Quebec or nrn ME remains a question. Chance pops have been included in the fcst. The NBM was generally followed for temps thru the long term. && .AVIATION /13Z THURSDAY THROUGH MONDAY/... Weak high pressure over the region slowly slides east today. VFR conditions through the TAF period. W-SW winds 5-10 kt with coastal sea breezes developing by afternoon at KJFK/KISP/KBDR. Trickiest forecast aspects look to be timing of sea breeze arrival at KLGA late day, which could occur a couple of hours later than forecast with a 180-190 degree direction (true) possible. Wind direction is also tricky at KGON. All hi-res guidance keep them SW but can`t rule out a due S sea breeze. NY Metro Enhanced Aviation Weather Support... Detailed information, including hourly TAF wind component fcsts, can be found at: http:/ KJFK TAF Comments: Timing of seabreeze may be +/- 1-2 hours from forecast. The afternoon KJFK haze potential forecast is GREEN, which implies slant range visibility P6SM outside of cloud. KLGA TAF Comments: Timing of seabreeze may be 1-2 hours later than forecast with direction possibly 180-190 degrees true. The afternoon KLGA haze potential forecast is GREEN, which implies slant range visibility P6SM outside of cloud. KEWR TAF Comments: Gusts may diminish 1-2 hours earlier than forecast. The afternoon KEWR haze potential forecast is GREEN, which implies slant range visibility P6SM outside of cloud. KTEB TAF Comments: Gusts may diminish 1-2 hours earlier than forecast. KHPN TAF Comments: No unscheduled amendments. KISP TAF Comments: Timing of seabreeze may be +/- 1-2 hours from forecast. .OUTLOOK FOR 12Z FRIDAY THROUGH MONDAY... .Fri...MVFR or lower conditions possible in showers/tstms mainly late day/evening, but sct activity could occur near the NYC metros as early as 17Z-19Z. S winds 10-15G20kt in the afternoon, except gusty/erratic in/near tstms. .Sat...MVFR or lower conds at times in any showers/tstms. W flow becoming NE Sat eve. .Sun...Chance of MVFR cigs in the morning. .Mon...VFR. && .MARINE... High pressure remains south of the waters today. Westerly to sw wind flow prevails, and seas remain 3 ft or less on the ocean waters. A backdoor front approaches tonight, but weakens or retreats to the north Friday. Relatively light winds tonight will turn to the south, and increase later in the day Friday ahead of a frontal boundary. Seas build late in the day. Winds and seas will likely hit sca lvls with strong sly flow on the ocean Fri ngt, before subsiding just blw criteria on Sat. Elsewhere, winds and seas look to remain blw criteria. Increasing ne flow on Sun may result in sca cond, especially on the ocean. Winds and seas all areas blw sca lvls Mon and Tue with high pres. && .HYDROLOGY... Dry conditions are anticipated through tonight. Heavy tstms late Fri and Fri ngt could result in areas of minor flooding. No hydrologic impacts are anticipated Sat-Wed. && .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...Heat Advisory until 6 PM EDT Friday for NYZ071>075-176>179. NJ...Heat Advisory until 6 PM EDT Friday for NJZ006-104-106>108. MARINE...None. && $$ SYNOPSIS...JMC/PW NEAR TERM...JMC/PW SHORT TERM...PW LONG TERM...JMC AVIATION...MD/24 MARINE...JMC/PW HYDROLOGY...JMC/PW EQUIPMENT... is the U.S. government's official web portal to all federal, state and local government web resources and services.