Area Forecast Discussion
Issued by NWS Upton, NY

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688 FXUS61 KOKX 241738 AFDOKX Area Forecast Discussion National Weather Service New York NY 1238 PM EST Tue Jan 24 2017 .SYNOPSIS... Strong low pressure just south of Long Island 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/... The Winter Weather Advisory has been extended into early evening across Putnam, Orange, and Western Passaic Counties. Temperatures are currently in the low to mid 30s across these zones, and based on northerly winds and upstream obs, temps expected to drop to around freezing. At the same time, max temp in the warm nose aloft increases a little before dropping off late this afternoon into this evening. The layer beneath this warm nose could be just cold enough for some sleet, but more so late day/early evening. Rain and freezing rain with perhaps some sleet is therefore forecast for these zones. There is a chance that freezing rain is not widespread, but felt it would be better option to extend the advisory for these areas. Sleet accumulation of under an inch with under a tenth of an inch of ice accretion expected. For Rockland and Northern Westchester Counties, there is more confidence that freezing rain would not be widespread - perhaps limited to the highest elevations. Elsewhere, plain rain is forecast as a deformation band sets up over the central part of the CWA. Up to an additional quarter to half inch of rainfall is expected 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 /18Z TUESDAY THROUGH SUNDAY/...
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Low pressure tracks into the Gulf of Maine through tonight, then into the Canadian Maritime Provinces into Wednesday afternoon. IFR conditions developing/continuing into this evening, except at KSWF where probably will remain MVFR. conditions could vary +/- 1 category through the evening. Conditions should improve to VFR 5-7z...except around 11z KGON. Winds continue to back to the NW into this evening 15-20g25-30kt. Winds subside slightly late tonight/early Wednesday morning throughout and back to the WNW at mainly city terminals. 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 likely into this evening for varying conditions between IFR and MVFR. Timing of changes in wind speed and direction could be off +/- 1-2 hours. KLGA TAF Comments: Amendments likely into this evening for varying conditions between IFR and MVFR. Timing of changes in wind speed and direction could be off +/- 1-2 hours. KEWR TAF Comments: Amendments likely into this evening for varying conditions between IFR and MVFR. Timing of changes in wind speed and direction could be off +/- 1-2 hours. KTEB TAF Comments: Amendments likely into this evening for varying conditions between IFR and MVFR. Timing of changes in wind speed and direction could be off +/- 1-2 hours. KHPN TAF Comments: Amendments likely into this evening for varying conditions between IFR and MVFR. Timing of changes in wind speed and direction could be off +/- 1-2 hours. KISP TAF Comments: Amendments likely into this evening for varying conditions between IFR and MVFR. Timing of changes in wind speed and direction could be off +/- 1-2 hours. .OUTLOOK FOR 18Z WEDNESDAY THROUGH SATURDAY... .Wednesday afternoon-Wednesday evening...VFR. WNW_WSW winds G15-20kt possible. .Late Wednesday night/Thursday morning...Low chance of MVFR. .Thursday afternoon-Sunday...VFR. W-WSW winds G15-25kt possible.
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&& .MARINE... Gale warning over the ocean waters has been extended through tonight. There could be a few hours this afternoon where criteria isn`t being met, but guidance and a tight pressure gradient behind the departing storm suggests winds increasing back to gales by tonight. For the other waters, SCA continues through tonight. 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. This band is expected to be centered near the city and Lower Hudson Valley. These amounts should not pose any hydrologic issues. && .TIDES/COASTAL FLOODING... High tide has passed. However, there is some residual minor coastal flooding for shorelines of Southwest Suffolk County on Long Island, particularly at Lindenhurst. For Southern Nassau County on Long Island, this is expected to be quite localized with the residual minor coastal flooding. Expecting all gages to fall below minor coastal flooding benchmarks by 1pm. Tidal departures are approximately 2 to 2.5 ft above astronomical. Tonight`s high tide levels will be the lower of the daily high tidal cycles and along with increasing offshore flow, no other coastal flooding is expected. However, Wednesday morning`s high tides will be approximately 0.1 to 0.2ft higher than this morning`s high tides. There will be increasing offshore flow as winds become more westerly. There could be some isolated tidal gages that touch or slightly exceed minor coastal flooding thresholds across the South Shore Bays but this is a low probability at this time. 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 9 to 13 ft surf. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...Winter Weather Advisory until 7 PM EST this evening for CTZ005. NY...Winter Weather Advisory until 7 PM EST this evening for NYZ067- 068. Coastal Flood Advisory until 1 PM EST this afternoon for NYZ080. NJ...Winter Weather Advisory until 7 PM EST this evening for NJZ002. MARINE...Small Craft Advisory until 6 AM EST Wednesday for ANZ330-335- 338-340-345. Gale Warning until 6 AM EST Wednesday for ANZ350-353-355. && $$ SYNOPSIS...DW NEAR TERM...JC/DW SHORT TERM...DW LONG TERM...DS/DW AVIATION...Maloit MARINE...DW HYDROLOGY...DW TIDES/COASTAL FLOODING...JM

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