Area Forecast Discussion
Issued by NWS Upton, NY

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744 FXUS61 KOKX 241237 AFDOKX Area Forecast Discussion National Weather Service New York NY 737 AM EST Tue Jan 24 2017 .SYNOPSIS... Strong low pressure just south of Long Island this morning will track slowly northeast through tonight and up into the Canadian Maritimes on Wednesday. High pressure builds in briefly for Wednesday. Low pressure moves across the Great Lakes Wednesday night and deepens as it moves into southeast Canada, remaining nearly stationary through the upcoming weekend. This low will send a series of cold fronts through the area, one on Thursday and then again over the weekend. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Winter Weather Advisory has been extended both in time and area across the Lower Hudson Valley and interior Southwest Connecticut. The advisory was expanded to include Northern Fairfield in Connecticut and Northern Westchester and Rockland Counties in New York. A shallow dome of cold air, which models are having a tough time handling, has been a bit colder and deeper. There has been little ground truth overnight, but mesonets and recent public reports have indicted 1-2 inches of sleet. There is still a fair amount of uncertainty as to how quickly temperatures will rise this morning on the backside of a strong coastal low as winds become even more northerly. Latest mesoscale models support nearly steady temperatures or slight rises across the interior. For now, have extended the advisory through noontime. This may have to be extended into the afternoon. Warmer air aloft wrapping in off the Atlantic should provide a strong enough warm nose for a transition to all liquid. In addition, the wind advisory has expired as the 60-70 kt low- level jet has lifted north and of the area. The steadiest precipitation has ended as the best dynamics and thermal forcing have lifted north of the area. Expect mainly light precipitation this morning. As the negatively tilted closed upper low lifts to northeast today, models are keying in on a deformation zone on its west side with the potential for banded moderate rain this afternoon, mainly impacting NYC metro and points north and west. There is some uncertainty as to where this will exactly set up. An additional quarter to half inch of rainfall is possible with this band with lesser amounts elsewhere. Temperatures will be slow to rise to today, with many locations holding nearly steady, ranging from the mid 30s inland to the lower 40s at the coast. Gusty North winds up to 30 mph will be possible into this afternoon. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM WEDNESDAY/... The vertically stacked low moves slowly along the New England coast tonight with the chances of precipitation slowly lowering from the southwest to the northeast. Heights begin to rise late at night as weak ridging builds to the west. Some of the rain on the backside of this system could transition over to sleet or freezing rain briefly before coming an to end tonight. Overnight lows will drop to around freezing inland, and in the mid and upper 30s at the coast. High pressure and sunny skies will be on tap for Wednesday. Building heights aloft and winds backing to the west will result in a much warmer day, with highs in the mid and upper 40s. This is about 10 degrees above normal. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... The next shortwave trough moves across the Great Lakes Wednesday night and swings across the region on Thursday. The GFS and some of its ensemble members indicate potential for showers as the cold front associated with this shortwave moves through Thursday. Other models and ensembles are drier. This appears to be due to the amplitude of H5 energy and moisture return. Will cap pops off at 30 percent at this time. Cold front moves offshore Thursday afternoon and evening. This front signifies a return to more seasonable temperatures, potentially a few degrees below normal. There is also good agreement among the models and ensemble means with a hemispheric pattern change with deep ridging across Western North America and mean troughing over the east. Dry forecast into the weekend although there is enough energy aloft within cyclonic flow that a few snow showers may reach interior sections. Late in the weekend into early next week, there are signals the mean trough across the east may sharpen up, but it is a bit early to say if there any impacts to sensible weather. && .AVIATION /13Z TUESDAY THROUGH SATURDAY/...
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Low pressure will stall south of Long Island today, then track northeast into the Gulf of Maine tonight. Gusty northeast flow will continue this morning before beginning to decrease and back to the northwest late this afternoon into tonight. Gusts this morning will generally top out at around 25 kts, with a few 30 kt gusts possible over the next couple hours at the coast. A mix of MVFR and IFR conditions to start. Where they are not already IFR, ceilings will fall to IFR at most of the city and coastal terminals through the morning hours. Ceilings then begin to improve this evening, eventually becoming VFR by Wednesday morning. While the steadiest rain has moved north of the area, periods of light rain and drizzle will continue throughout the day. Most terminals will see plain rain, however KSWF will see a mix of rain, sleet, and freezing rain this morning. Sleet may also mix in for a brief period this morning at KHPN. Steadier rain may return in and around the city terminals this afternoon, although exactly where any more persistent rain sets up remains in question. 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: Amendments possible this morning for changes in ceiling and visibility. KLGA TAF Comments: Amendments possible this morning for changes in ceiling and visibility. KEWR TAF Comments: Amendments possible this morning for changes in ceiling and visibility. The afternoon KEWR haze potential forecast is YELLOW...which implies slant range visibility 4-6SM outside of cloud. KTEB TAF Comments: Amendments possible this morning for changes in ceiling and visibility. KHPN TAF Comments: Amendments possible this morning for changes in ceiling and visibility. Sleet may briefly mix with rain this morning. KISP TAF Comments: Amendments possible this morning for changes in ceiling and visibility. .OUTLOOK FOR 12Z WEDNESDAY THROUGH SATURDAY... .Wednesday and Thursday...VFR. NW winds become W-SW Wednesday near 10 kt. SW-W winds Thursday 10-15 kt gusts to near 20 kt. .Friday...VFR. W winds 10-15 kt gusts to 20 kt. .Saturday...VFR. W winds 10-15 kt.
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&& .MARINE... Storm warning on the ocean waters has been downgraded to a gale, while the remaining waters are under an SCA. Low pressure just south of the waters this morning will track slowly northeast today and up into the Canadian Maritimes on Wednesday. Winds are forecast to subside quickly this morning with SCA conditions likely on all waters by afternoon. The low continues to pull away tonight with a tight enough pressure gradient for SCA conditions to continue with NW gusts 25-30 kt. Winds diminish on all waters Wednesday with a weakening pressure gradient as high pressure settles over the waters. Ocean seas should also subside below 5 ft by evening. SCA conditions are likely on all waters on Thursday with a steepening pressure gradient with a cold front passage. These conditions may continue into Friday and possibly into Saturday, especially on the ocean waters. && .HYDROLOGY... An additional quarter to half inch of rainfall is possible today as a band of moderate rain develops on the backside of departing low pressure. The exact placement is uncertain, but likely from from around the NYC metro to points north and west. These amounts should not pose any hydrologic issues. && .TIDES/COASTAL FLOODING...
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Added western LI sound to the cstl flood advisory based on trends. One more round of minor to moderate coastal flooding in the southern and eastern bays of Long Island this morning. Major cstl flooding near lindenhurst. Elsewhere mainly localized minor coastal flooding. Will maintain current headlines. An ensemble of guidances is showing surge of 2 1/2 to 3 ft early this morning but with a higher astro tide. The other continuing concern will be for widespread dune erosion and localized washovers at Atlantic ocean beaches from elevated waters levels and an east to west sweep of 8 to 14 ft surf.
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&& .OKX WATCHES/WARNINGS/ADVISORIES...
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CT...Winter Weather Advisory until noon EST today for CTZ005. Coastal Flood Advisory until 11 AM EST this morning for CTZ009- 010. NY...Winter Weather Advisory until noon EST today for NYZ067>070. Coastal Flood Advisory until 11 AM EST this morning for NYZ071- 078-177. Coastal Flood Warning until 11 AM EST this morning for NYZ079>081-179. NJ...Winter Weather Advisory until noon EST today for NJZ002. MARINE...Small Craft Advisory until 6 AM EST Wednesday for ANZ330-335- 338-340-345. Gale Warning until noon EST today for ANZ350-353-355.
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&& $$ SYNOPSIS...DW NEAR TERM...DW SHORT TERM...DW LONG TERM...DS/DW AVIATION...FEB MARINE...DW HYDROLOGY...DW TIDES/COASTAL FLOODING...pw

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