Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 271334 AFDOKX Area Forecast Discussion National Weather Service New York NY 934 AM EDT Thu Oct 27 2016 .SYNOPSIS... Low pressure approaches from the west today and passes through tonight. High pressure then builds back in on Friday and lasts into Saturday. A cold front will approach from the north Saturday night, then sink through the area on Sunday as low pressure moves along it. High pressure then returns Monday and Tuesday, with a weak cold frontal passage on Wednesday. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Updated the probabilities and weather this morning as light precipitation has spread east into central Connecticut and central Long Island as isentropic lift increases ahead of the warm front through central Pennsylvania into southeastern Pennsylvania. With dew point depressions highs in the low levels and temperatures were right around freezing at 2000 FT from 12Z at Upton and looking at model sounding data, periods of light sleet have been reported across NYC metro, across Long Island, and portions of coastal Connecticut. Expect a snow/sleet mix across the interior to gradually change to rain by midday or early afternoon, and all rain elsewhere. Regarding snow totals before the changeover to rain, going with up to an inch for the higher interior elevations, and less than an inch down to about I-95 in CT and to about I-287 in NY/NJ. Clouds and precip will hold high daytime temperatures well below average. The high temperature for the calendar day for many spots might not occur until the evening hours.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM FRIDAY/... As the parent low center of the storm moves through eastern Great Lakes region, a secondary low is progged to develop and move over the CWA tonight. Associated lift and a developing low level jet will enhance rainfall, and it could be heavy at times generally over the eastern half of the CWA. With some elevated instability present, a thunderstorm cannot be ruled out either. Better chances of this will be over the southern zones. Rain then ends overnight, and only a lingering shower will still possible by daybreak for the easternmost zones. Varying amounts of cloud cover is expected through the day Friday along with breezy conditions. It still appears that remains dry as the timing of cyclonic flow aloft, low level heating, and sufficient moisture won`t coincide well enough. High temperatures will be below normal once again. && .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... There are some changes in the offing for the weekend. Guidance has trended more slowly with the cold frontal approach Sat into Sat night, which should allow a wave of low pressure associated with an approaching northern stream upper trough to ride east along the front, and more directly impact the area on Sunday before the front sinks south Sunday night. Have bumped PoP up to likely for most of the area on Sunday to reflect this. High pressure should return thereafter, with only a dry/weak frontal passage expected on Wednesday. Temps on Sunday are quite uncertain and will depend on the amt of rain and cloud cover, and the position of the approaching front. Otherwise with the exception of Monday into Monday night as Canadian high pressure briefly builds in, temps through the period should be at or a little above average. && .AVIATION /14Z THURSDAY THROUGH MONDAY/... An area of low pressure approaches from the Ohio valley today and move across the area tonight. Light Northeast/East winds veer to the East/Southeast through the day and increase during the afternoon with gusts. Mid and high level clouds continue to overspread the region with light rain developing around daybreak. At KSWF...precip could start as a period of wet snow with little to no accumulation expected. There is a low chance of any freezing rain and/or sleet. MVFR conditions develop from west to east during the mid to late morning with steadier light rain...dropping to IFR in the late aft/eve in moderate rain. Timing of deteriorating conditions may be off by 1 to 2 hrs...depending on how quickly the low-levels moisten. After midnight, winds become more westerly and conditions improve to VFR. Sub-VFR conditions may linger east of NYC. NY Metro Enhanced Aviation Weather Support... Detailed information, including hourly TAF wind component forecasts, can be found at: http:/ KJFK TAF Comments: Timing of changing flight categories may be off by 1 to 2 hrs. KLGA TAF Comments: Timing of changing flight categories may be off by 1 to 2 hrs. KEWR TAF Comments: Timing of changing flight categories may be off by 1 to 2 hrs. The afternoon KEWR haze potential forecast is GREEN...which implies slant range visibility 7SM or greater outside of cloud. KTEB TAF Comments: Timing of changing flight categories may be off by 1 to 2 hrs. KHPN TAF Comments: Timing of changing flight categories may be off by 1 to 2 hrs. KISP TAF Comments: Timing of changing flight categories may be off by 1 to 2 hrs. .OUTLOOK FOR 12Z FRIDAY THROUGH SUNDAY... .Friday...VFR with strong northwest flow behind a cold front. Gusts 25-30kt. .Saturday and Sunday...VFR with gusty southwest flow possible. Low chance of showers during the afternoon/evening both days. .Monday...VFR. && .MARINE... SCA remains on the ocean waters starting this afternoon. There could be a few gusts to 25 kt on the other waters late this afternoon as the pressure gradient tightens. The better chance of SCA conds on the other waters will be for a period this evening ahead of the passage of a low center, and late at night when the low shifts east of the waters. Will go with a SCA for the non- ocean waters for tonight although there could be an extended period where advisory conditions might not be met. There is also a chance on the ocean waters for a few gale force gusts, but thinking is that frequent gales will be more likely during the day Friday. Have therefore gone with a gale warning east of Fire Island Inlet during the day Friday where the pressure gradient on the backside of the departing storm will be tighter. SCA conds otherwise for all other waters through the day Friday. NW gales are lily to continue into Fri evening on the eastern ocean waters, with SCA conditions most elsewhere. Any respite should be brief, as WSW flow on Sat well in advance of a cold front should reach SCA levels on most waters, and may gust to minimal gale force out east late day Sat. SCA conditions could last on the ocean thereafter into Sunday morning in advance of the front and low pressure approaching from the west, then return late Sunday night into Mon via post-frontal N flow gusting up to 25 kt. && .HYDROLOGY... Liquid equivalent precipitation is expected to range from 0.75 to1.25 inches through tonight. The higher amounts are expected generally over CT and Long Island. Although not likely, there is at least a chance for minor urbanized/poor drainage/small stream flooding in heavier downpours that might occur this evening. Widespread significant precipitation is not expected for the rest of the forecast period. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...Small Craft Advisory from 8 PM this evening to 6 PM EDT Friday for ANZ330-335-338-340-345. Small Craft Advisory from 2 PM this afternoon to 6 AM EDT Friday for ANZ350-353. Gale Warning from 6 AM to 6 PM EDT Friday for ANZ350-353. Small Craft Advisory from 2 PM this afternoon to 6 PM EDT Friday for ANZ355. && $$ is the U.S. government's official web portal to all federal, state and local government web resources and services.