Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 232106 AFDOKX Area Forecast Discussion National Weather Service New York NY 406 PM EST Mon Jan 23 2017 .SYNOPSIS...
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Strong low pressure moving up the east coast passes to our southeast Tuesday afternoon into night. High pressure then builds in on Wednesday. Low pressure moves across the Great Lakes Wednesday night and deepens as it moves into SE 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.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Strong low pressure system moves north along the Mid-Atlantic coast with high pressure centered over SE Canada. The pressure gradient created between these two systems will continue to produce strong sustained winds across the area, and sufficient mixing down of winds from a 925mb low level jet of 65-70 KT will produce strong gusts. The High Wind Warnings therefore remain up at the coast into the overnight hours, with Wind Advisories up for much of the interior. Regarding PCPN, with the low level jet and mid-level frontogenetic forcing pushing in from the south, expecting rain to be heavy at times. The main question is how much dynamic cooling we get aloft, having implications for PCPN type for interior sections, especially the NW zones. Models at least agree that below the warm nose at 850- 750mb, temps above the surface start out at -5C to -6C before warming, which is cold enough to turn rain aloft to sleet. What is more uncertain is the warmest temperature that will occur in the warm nose. The warm nose should warm up as the night wears on, however GFS/ECMWF continue to be colder than NAM/RAP/HRRR regarding max warm nose temp. Went with a compromise between the 2 camps, with the current forecast trending a little colder than the previous. Should the heavy precipitation fall as snow for a longer period of time, snowfall totals would be higher than currently forecast, and vice versa if more as rain. Right now, those locations under a winter weather advisory are forecast to see 2 to 4 inches of snow and sleet. Have trimmed back with freezing rain potential, but perhaps a light coating of ice possible over the higher elevations of Orange County. A Flood Watch remains up for the NYC metro, southern portions of the Lower Hudson Valley, and coastal SW Connecticut. This is mainly for urban and small stream flooding concerns, especially if localized rainfall amounts exceed 3 inches. Flooding could still be exacerbated by lingering effects of high tide early this evening. This includes locations along tidally affected rivers, such as the Passaic, Hackensack, and Hudson. Winds and heavy precip should fall off late tonight, but rain still remains likely by daybreak.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/...
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The center of the storm slowly shifts east through the day south of Long Island as the surface low becomes stacked with the 500mb low. Rain remains likely through at least early afternoon with chances dropping off by the evening. It could be cold enough across mainly the higher elevations of Orange County for sleet to be mixed in. It`ll be breezy to start, but winds will diminish through the day as they shift more northerly behind the departing storm.
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&& .LONG TERM /TUESDAY NIGHT THROUGH MONDAY/...
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Global models and ensembles are in general agreement through the long term period. The main story will be a return to more seasonable temperatures late in the week into the weekend with drier than normal conditions favored. For Tuesday night...Strong low pressure affecting the area early this week will gradually depart to the east as negatively tilted trough axis swings across. Energetic flow and moisture wrapping around the low could still bring some precipitation Tuesday evening, tapering off from west to east after midnight. Will need to watch thermal profiles mainly across Orange county as warm nose aloft may still support a rain/sleet mix. Precipitation ends after midnight as lift departs to the east. Lows range from the lower 30s inland to the middle and upper 30s near the coast. High pressure ridge briefly returns on Wednesday. Temperatures will still be on average ten degrees above normal with forecast highs in the upper 40s to near 50 degrees. 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.
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&& .AVIATION /21Z MONDAY THROUGH SATURDAY/...
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A strengthening coastal storm tracks southeast of Long Island tonight into Tuesday. This will bring a period of very gusty winds in excess of 40kt for most terminals through much of tonight along with conditions deteriorating from MVFR to IFR as steadier and heavier rain moves in. Peak gusts will be between 50 and 60 kt for coastal terminals, particularly into this evening and to just after midnight, a few hours later east of the city terminals. Some sleet and snow will be seen mainly north and west of city terminals, particularly at KSWF into tonight with total snow accumulations 2-3 inches. Rain mixing with sleet will be seen going into early evening for the city and nearby terminals. Winds will trend down first early Tuesday with rainfall becoming more light. Wind gusts are forecast to drop to closer to 25-35 kt going into daybreak Tuesday. IFR will likely remain through Tuesday morning and into Tuesday afternoon. 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 forecast peak gusts and IFR could be off by 1-3 hours. Some brief sleet could mix in with rain before 02Z. KLGA TAF Comments: Timing of forecast peak gusts and IFR could be off by 1-3 hours. KEWR TAF Comments: Timing of forecast peak gusts and IFR could be off by 1-3 hours. KTEB TAF Comments: Timing of forecast peak gusts and IFR could be off by 1-3 hours. KHPN TAF Comments: Timing of forecast peak gusts and IFR could be off by 1-3 hours. KISP TAF Comments: Timing of forecast peak gusts and IFR could be off by 2-4 hours. .OUTLOOK FOR 21Z TUESDAY THROUGH SATURDAY... .Tuesday Afternoon-Tuesday night...IFR improving to MVFR Tuesday Evening and eventually VFR late Tuesday night. Rain will come to an end beginning late Tuesday afternoon. Winds NE backing to NW during the day with gusts decreasing to 20-25 kt. .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...
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An intensifying storm moving up the coast will bring storm to marginal hurricane force wind gusts to the ocean waters late this this evening. On the non-ocean waters, storm warnings remain in effect. Expect peak winds 60-65 kt where storm warnings remain, and closer to 50-55 KT elsewhere. Max seas could peak at around 20 ft on the ocean, 9-12 ft from Orient Point east in the sound, and 8-9 ft on central Long Island Sound, per combo of WaveWatch/NWPS guidance and wind/wave climatology. Winds and seas then diminish throughout the day Tuesday, but with Gales still likely early on. The low pressure system departs Tuesday night with a steep enough pressure gradient to bring potential for SCA winds on all waters. Ocean seas will also range from 6 to 9 ft. 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. 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.
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&& .HYDROLOGY...
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QPF through tonight will likely be in the 1-2 inch range, with locally higher amounts possible with the heaviest rainfall. If high end rainfall amounts are realized, this will bring a threat for moderate urban flooding and minor small stream flooding in NE NJ and the Lower Hudson Valley. This will be exacerbated by any lingering effects of high tide early this evening combining with heavy rain along coastal waterfront and shoreline roads...including along tidally affected rivers. Potential for minor flooding on larger rivers is slight.
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&& .TIDES/COASTAL FLOODING...
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Slower storm movement continues to point to widespread minor...with moderate impacts for southern and eastern bays and beachfront of LI...for this afternoon into evening high tide. A higher residual surge into Tuesday morning will result in another round of minor to moderate coastal flooding...mainly for for the southern and eastern bays of Long island. In fact...water levels for Tuesday morning high tides will likely be slightly higher than this evening for several locations on the southern and eastern bays of LI. An ensemble of guidances is showing potential for surge to build to 3 to 4 ft by this evening and 2 1/2 to 3 1/2 ft for Tuesday morning. The other 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 today into Tue.
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&& .OKX WATCHES/WARNINGS/ADVISORIES...
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CT...High Wind Warning until 6 AM EST Tuesday for CTZ009>012. Flood Watch through late tonight for CTZ009. Wind Advisory until 1 AM EST Tuesday for CTZ005. Coastal Flood Advisory until 11 PM EST this evening for CTZ009>012. Wind Advisory until 6 AM EST Tuesday for CTZ006>008. NY...Coastal Flood Warning until 11 PM EST this evening for NYZ079>081-179. Coastal Flood Warning from 4 AM to 11 AM EST Tuesday for NYZ079>081-179. High Wind Warning until 6 AM EST Tuesday for NYZ071>075- 078>081-176>179. Winter Weather Advisory until 7 AM EST Tuesday for NYZ067-068. Flood Watch through late tonight for NYZ069>075-176>179. Wind Advisory until 1 AM EST Tuesday for NYZ069-070. Coastal Flood Advisory until 9 PM EST this evening for NYZ072- 075-178. Coastal Flood Advisory from 4 AM to 8 AM EST Tuesday for NYZ074-075-178. Coastal Flood Advisory until 11 PM EST this evening for NYZ073- 176. Coastal Flood Warning from 7 PM to 11 PM EST this evening for NYZ071-078-177. Coastal Flood Warning until 7 PM EST this evening for NYZ074. NJ...High Wind Warning until 6 AM EST Tuesday for NJZ006-106-108. Winter Weather Advisory until 7 AM EST Tuesday for NJZ002. Flood Watch through late tonight for NJZ004-006-103>108. Wind Advisory until 1 AM EST Tuesday for NJZ004-103>105-107. Coastal Flood Advisory until 9 PM EST this evening for NJZ006- 106-108. Coastal Flood Advisory from 4 AM to 8 AM EST Tuesday for NJZ006-106-108. MARINE...Storm Warning until 1 AM EST Tuesday for ANZ335-338-345. Storm Warning until 6 AM EST Tuesday for ANZ330-340. Hurricane Force Wind Warning until 1 AM EST Tuesday for ANZ350- 353-355.
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&& $$ SYNOPSIS...JC/DS NEAR TERM...JC/Goodman SHORT TERM...JC/Goodman LONG TERM...DS AVIATION...JM MARINE...JC/Goodman/DS HYDROLOGY...JC/DS TIDES/COASTAL FLOODING...nv

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