Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 171547 AFDOKX Area Forecast Discussion National Weather Service New York NY 1047 AM EST Wed Jan 17 2018 .SYNOPSIS... Low pressure tracks from south of Long Island into the Gulf of Maine today. High pressure then builds in from the southwest through Thursday, then to the south through Friday, and then moves into the western Atlantic this weekend. A warm front will slowly lift to the north on Monday, then a cold front will pass through on Tuesday. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Rain/snow line has pushed east, and as of 1430Z is now over Nassau and Fairfield Counties. Expecting this line to advance eastward as the morning. At the same time, PoPs diminish east to west. An additional 1.0 to 1.5 inches of snow expected mainly north of the city with lighter accumulations elsewhere. Have lowered the total snowfall forecast in the city and most spots within about 20 miles of it. Will however keep all headlines as they are to address slippery road conditions. Low level cold advection in the wake of the coastal low should lower temperatures into this afternoon. Temps are expected to be mostly 30-35 across the area by sunset. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/... A closed 700-500 hPa low tracks across the Mid Atlantic States tonight, then to the SE of Long Island on Thursday, as northern stream shortwave ridging builds into the area. Given that the best forcing stays to the S tonight, and subsidence from the ridging on Thursday, it should be dry both periods. AS far as cloud cover goes, should see decreasing cloud cover tonight from W to E, then mostly sunny sky conditions on Thursday. Lows tonight should be up to 5 degrees below normal and highs on Thursday around 5 degrees below normal. && .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/... Surface high pressure will build to our south through Friday. An upper trough passing through Thu night into Fri morning should bring an increase in clouds but no precip. Temps on Friday should be slightly above avg. As low pressure passes to the north and high pressure to the south on Sat. expect a brisk W flow to develop, especially along the coast. These winds should weaken on Sunday as the low continues east. GFS and ECMWF disagree a little as to whether the flat upper ridge to the south or the flat trough to the north will prevail, but at any rate temps will continue to trend above avg into the weekend, with highs 45-50 if not a little higher. An amplifying but progressive upper trough entering the Plains states late this weekend will send sfc low pressure NE toward the upper Great Lakes. A leading warm front will approach our area late Sunday night into Mon, and its progress may be delayed by high pressure to the NE. There could be some spotty wintry precip inland late Sunday night into Mon morning, otherwise light rain into Mon evening. Followed slower model trend with a cold front trailing from the Great Lakes low, with its approach late Mon night into Tue. We could be setting up for a moderate to locally heavy rain event during this time as the low taps Atlantic moisture via a strengthening LLJ, with both it and difluent flow aloft likely providing enhanced lift, and a possible triple-point low passing nearby and concentrating low level convergence. && .AVIATION /16Z WEDNESDAY THROUGH SUNDAY/...
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A coastal low will continue northeastward into the Canadian Maritimes through tonight. Mainly LIFR-IFR conditions will continue into the early afternoon as snow gradually ends from west to east. Eastern terminals including KBDR/KGON/KISP will start as initially rain but may transition to a rain/snow mix or all snow by early afternoon. Conditions may then be slow to improve as precipitation ends, with a period of MVFR possible before evening. Overnight, skies will eventually clear with VFR conditions prevailing. Winds mainly NW with the exception of KBDR/KGON and KISP...where NE flow will switch to NW by afternoon. As precipitation ends, expect gusts to gradually increase through the afternoon and evening. 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 snow tapering off and ending this afternoon may be off by +/- 1 hour. Timing of VFR conditions may be off by +/- 1 to 2 hours this afternoon. The afternoon KJFK haze potential forecast is YELLOW...which implies slant range visibility 4-6SM outside of cloud. KLGA TAF Comments: Timing of snow tapering off and ending this afternoon may be off by +/- 1 hour. Timing of VFR conditions may be off by +/- 1 to 2 hours this afternoon. The afternoon KLGA haze potential forecast is YELLOW...which implies slant range visibility 4-6SM outside of cloud. KEWR TAF Comments: Timing of snow tapering off and ending this afternoon may be off by +/- 1 hour. Timing of VFR conditions may be off by +/- 1 to 2 hours this afternoon. The afternoon KEWR haze potential forecast is YELLOW...which implies slant range visibility 4-6SM outside of cloud. KTEB TAF Comments: Timing of snow tapering off and ending this afternoon may be off by +/- 1 hour. Timing of VFR conditions may be off by +/- 1 to 2 hours this afternoon. KHPN TAF Comments: Timing of snow tapering off and ending this afternoon may be off by +/- 1 hour. Timing of VFR conditions may be off by +/- 1 to 2 hours this afternoon. KISP TAF Comments: Precipitation may end as a brief period of snow early this afternoon, but confidence is low. Timing of VFR conditions may be off by +/- 1 to 2 hours this afternoon. .OUTLOOK FOR 12Z THURSDAY THROUGH SUNDAY... .Thursday-Thursday Night...VFR. WNW winds G20KT on Thursday. .Friday...VFR. W-SW winds G15-20KT possible. .Saturday-Sunday...VFR.
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&& .MARINE... A moderate pressure gradient over the waters will allow winds on the ocean waters to reach up to 20 kt with gusts up to 25 kt through Thursday and over the non-ocean waters up to 15 kt with gusts up to 20 kt through Thursday. With seas on the ocean waters forecast to 3 to 7 ft as well, have extended the Small Craft Advisory (SCA) there through 6PM Thursday. Marginal SCA conds may continue on the outer ocean waters into Thu night and Fri. SCA conds are also likely Sat into Sat evening on the ocean as a moderate W flow develops between low pressure passing well to the north and high pressure building to the south. && .HYDROLOGY... No significant hydrologic impacts are expected through at least the upcoming weekend. A frontal system passing through Mon night into Tue has potential to bring over an inch of rain during that time. Mainly nuisance urban/poor drainage impacts expected attm. && .EQUIPMENT...
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NYC NOAA Weather Radio Station KWO-35 (162.55 MHz) is off the air for an extended period of time. The Riverhead (RVH) NOAA Weather Radio Station WXM-80 (162.475) is emitting a loud buzzing noise that is currently being worked on by technicians.
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&& .OKX WATCHES/WARNINGS/ADVISORIES... CT...Winter Weather Advisory until 1 PM EST this afternoon for CTZ005>008. NY...Winter Weather Advisory until noon EST today for NYZ069-070. Winter Storm Warning until noon EST today for NYZ067-068. NJ...Winter Weather Advisory until noon EST today for NJZ002-004- 103>105-107. MARINE...Small Craft Advisory until 6 PM EST Thursday for ANZ350-353- 355. && $$ SYNOPSIS...Goodman/Maloit NEAR TERM...JC/Goodman/Maloit SHORT TERM...Maloit LONG TERM...Goodman AVIATION...MD/JE MARINE...Goodman/Maloit HYDROLOGY...Goodman/Maloit EQUIPMENT...

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