Area Forecast Discussion
Issued by NWS Upton, NY

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897 FXUS61 KOKX 141702 AFDOKX Area Forecast Discussion National Weather Service New York NY 1202 PM EST Thu Dec 14 2017 .SYNOPSIS...
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An area of low pressure will quickly move eastward out to sea today, followed by high pressure building from the west tonight. A series of weak low pressure and frontal systems will pass through Friday through early next week, with high pressure building between each.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Snow has ended across the area with the exception of some light returns/flurries across eastern coastal CT. Expect these to diminish rapidly early this afternoon. The advection of drier air and subsidence in the wake of the departing system has allowed cloud cover to quickly decrease across the area, with mostly clear skies developing from west to east. Breezy conditions are developing as the pressure gradient remains tight between the departing low and high pressure building from the west. Combined with well below normal temperatures in the upper 20s to mid 30s, wind chill values will once again be in the teens across interior portions of the forecast area, and low to mid 20s elsewhere.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM FRIDAY/...
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High pressure settles over the Tri-State tonight. With diminishing winds, mostly clear skies, cold airmass, and some snowpack on the ground, temperatures should bottom out in the lower teens and even single digits inland and middle and upper teens elsewhere (around 20 in the NYC metro area). The high moves offshore Fri aftn as the next shortwave trough and associated sfc low approach from the Great Lakes region with another low also developing along the Mid Atlantic coast. Have kept the PoPs from the previous forecast as it still appears pcpn could start to move into NW and SE areas late in the period. It is cold enough for snow. Highs on Fri will be similar to those today.
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&& .LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/... The first in a series of upper level shortwaves in a progressive pattern pushes across the region Friday night into early Saturday morning. An offshore low develops well southeast of the area Friday night out ahead of the shortwave energy. While some light snow will be possible Saturday night, most if not all of the 00z forecast guidance keeps the bulk of the associated QPF offshore, and to our NW, closer to the inland parent low. Therefore, will continue to keep low chance POPs in the forecast. This shortwave passes Saturday as ridge builds, and remains in control through much of the weekend. The forecast becomes a bit more uncertain Sunday night through Tuesday as a series of weak shortwaves pass over the region. The latest 00z forecast guidance continues to show timing differences for each of these shortwaves along with their exact placement. Forecast guidance does however show each of these waves moving across the area with very low QPF values. So for now, will go with at least a chance or slight chance POPS Sunday night through Tuesday to account for the timing uncertainty. Surface high pressure and upper level ridging builds over the region for Wednesday and Thursday. Chilly temperatures continue Saturday and Sunday, then gradually warm closer to normal as zonal flow or weak ridging develops for Monday and Tuesday. Temperatures fall back below normal for Wednesday and Thursday. && .AVIATION /18Z THURSDAY THROUGH TUESDAY/... As of 14Z light SN now east of the NY Metro and will be east of LI/Southeastern CT by 16Z. Skies clear quickly behind the Alberta Clipper with winds backing to NW and becoming gusty of the afternoon. VFR as wind gusts diminish this evening with high pressure building in. 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: Direction averages 310-320 magnetic this afternoon with +/- 20 degrees of variablity. High confidence forecast. The afternoon KJFK haze potential forecast is GREEN, which implies slant range visibility 7SM or greater outside of cloud. KLGA TAF Comments: Direction averages 320-330 magnetic this afternoon with +/- 20 degrees of variablity. High confidence forecast. The afternoon KLGA haze potential forecast is GREEN, which implies slant range visibility 7SM or greater outside of cloud. KEWR TAF Comments: Direction averages 320-330 magnetic this afternoon with +/- 20 degrees of variablity. High confidence forecast. The afternoon KEWR haze potential forecast is GREEN, which implies slant range visibility 7SM or greater outside of cloud. KTEB TAF Comments: No Unscheduled TAF Amendments Expected. KHPN TAF Comments: TAF Amendments Not Scheduled KISP TAF Comments: High confidence forecast. .OUTLOOK FOR 12Z FRIDAY THROUGH MONDAY... .Friday...VFR. .Friday night...VFR. W winds G15-20KT develop towards early Saturday morning. .Saturday-Saturday night...VFR. WNW winds G20-25KT daytime and G15- 20KT evening. .Sunday...Mainly VFR. .Sunday night and Monday...MVFR or lower flight cat possible in snow/rain. && .MARINE...
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Minor update this afternoon to increase seas on the harbor to just under SCA-levels. Otherwise, SCA conds will remain on the ocean waters for both winds and seas through the day, with winds diminishing this eve, and just residual seas remaining into tonight. Have extended the advsy through midnight tonight west of Fire Island Inlet and through 6am to the east, although they may fall below a few hours earlier. Could have gusts reaching 25 kt at times on eastern LI Sound and LI bays today, but not expecting them to be frequent enough to warrant the continuation of SCA. Sub-advsy conds all waters on Fri. Low pressure develops Friday night just east of the waters and deepens as it departs Saturday, with increasing westerly winds, and building seas expected behind it. Winds abate and seas subside as high pressure builds Saturday night through Sunday. Winds and seas remain below SCA levels Monday and Tuesday. Winds and seas build back to SCA levels Tuesday night and Wednesday as the pressure gradient increases behind a departing low and approaching high pressure system.
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&& .HYDROLOGY... No significant hydrologic impacts expected. && .EQUIPMENT... NYC NOAA Weather Radio Station KWO-35 (162.55 MHz) is off the air for an extended period of time. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...Small Craft Advisory until midnight EST tonight for ANZ355. Small Craft Advisory until 6 AM EST Friday for ANZ350-353. && $$ SYNOPSIS...DS/PW NEAR TERM...MD/DS/DW SHORT TERM...DS LONG TERM...PW AVIATION...JP/Tongue MARINE...DS/DW/PW HYDROLOGY...DS/PW EQUIPMENT...

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