Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 150139 AFDOKX Area Forecast Discussion National Weather Service New York NY 839 PM EST Tue Nov 14 2017 .SYNOPSIS... High pressure builds over the Tri State Area tonight and Wednesday. A warm front approaches from the southwest Wednesday night, then lifts to the north Thursday morning, followed quickly by a cold frontal passage Thursday afternoon. High pressure builds into the region Friday. A complex low impacts the area Saturday into Sunday, followed by high pressure building in Monday and Tuesday. && .NEAR TERM /THROUGH WEDNESDAY/...
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The forecast has been updated to increase cloud cover, particularly across eastern CT and Long Island based on satellite. No other significant changes were made. Showers offshore are associated with a weak surface trough and low level moisture convergence. High-res models show little overall movement to this activity, since surface trough should remain nearly stationary, but gradually weakens everything thru late afternoon as moisture convergence begins to diminish. Cloudiness will be slow to erode however, as upper flow is initially cyclonic, but ridging aloft and drying through lower levels will allow skies to clear early tonight. Lows will fall back into the upper 20s to mid 30s, except upper 30s in NYC.
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&& .SHORT TERM /WEDNESDAY NIGHT THROUGH 6 PM WEDNESDAY/... High pressure builds over region Wednesday, resulting in plenty of sunshine and light winds, though we should see some increase in mid and high clouds during afternoon ahead of next system. Highs will reach mid 40s to around 50. && .LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/... Watching a couple of systems which are both expected to bring a round of showers and are followed by strong winds and reinforcement of colder air - one Wednesday night into Thursday and the second Saturday into Sunday. For first system, upper ridge moves quickly offshore Wednesday night and allows deepening trough to approach from eastern Great Lakes. There are some differences among operational models as to how fast and exactly where upper trough closes off, with 12z ECMWF doing so much more rapidly, resulting in stronger secondary low east of Long Island Thursday afternoon. Given this is more of an outlier and doesn`t have much support from ensembles, which do not support such rapid deepening, prefer to keep system progressive with cold front crossing area Thursday followed by reinforcing shot of cold air on gusty NW winds. We will have a quick break Friday as high pressure once again builds over region. However, upper pattern remains progressive and next system should already be on our doorstep Saturday morning. Once again there are timing differences among operational models, with 12z GFS on faster side of consensus, bringing showers into area Saturday morning as opposed to afternoon. This faster timing is not preferred since upper trough should deepen with time as it approaches area, resulting in slower onset of showers, with most of rain falling from Saturday afternoon into Sunday morning. However, if other models should trend more in line with faster GFS, it would mean greater potential for light snow or wintry mix at start across lower Hudson Valley late Friday night or early Saturday morning. This second system looks to be more robust than first once according to ensembles, but nothing overly anomalous for this time of year. Potential hazards include strong gusty winds, both ahead of and behind system, due to strong low level jet. Potential looks to be greater in cold advection pattern behind it Sunday, when we could see NW winds gust as high as 35-45 mph. System should exit quickly Sunday afternoon, with dry weather expected Monday and Tuesday as high pressure builds over region. However, with upper flow remaining cyclonic due to cutoff over SE Canada, expect more in way of cloudiness and perhaps some flurries across Orange County. && .AVIATION /02Z WEDNESDAY THROUGH SUNDAY/... High pressure remains centered over the northeast. VFR tonight, however MVFR cigs over KISP early this evening and briefly over KJFK at times over the next hour or two. NE winds 5-10 KT. For Wednesday, likely VFR all day, but late day or early evening MVFR cigs could occur. Winds will veer E briefly before shifting SE during the 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: Brief broken cigs around 2500 ft possible until 02z. KLGA TAF Comments: No unscheduled amendments expected. KEWR TAF Comments: No unscheduled amendments expected. KTEB TAF Comments: No unscheduled amendments expected. KHPN TAF Comments: No unscheduled amendments expected. KISP TAF Comments: Improvement to VFR may be off by an hour or two this evening. .OUTLOOK FOR 00Z THURSDAY THROUGH SUNDAY... .Wednesday night-Thursday...MVFR or lower possible in showers. W-NW winds G20-30KT possible Thursday afternoon. .Thursday night-Friday...VFR. NW winds G25-30KT, strongest Thursday night. .Saturday...Sub VFR conditions possible by the afternoon and becoming likely towards evening. S-SW winds G25KT. .Sunday...Conditions improve to VFR. NW winds G25-30KT. && .MARINE... Winds and seas expected to remain below Small Craft Advisory levels tonight and Wednesday as high pressure builds over waters. Increasing southerly flow expected Wednesday night ahead of cold front, which crosses area Thursday and should bring NW 20-30kt gusts behind it Thursday afternoon into Friday morning. It`s possible gusts reach Gale force (34kt) on ocean waters south of Long Island, but confidence is not high enough to issue Gale Watches at this time, since it looks marginal. High pressure briefly builds over waters Friday, resulting in diminishing winds and seas. Next strong cold front affects waters Saturday into Sunday. Potential exists for Gale force gusts both ahead of, and especially behind front Sunday into Monday, especially on ocean waters south of Long Island. Gale potential will continue to be highlighted in the Hazardous Weather Outlook (HWO). && .HYDROLOGY... Looking at two rounds of rainfall over next few days - first Wednesday night into Thursday and a second Saturday into Sunday. Rainfall appears to be light with the first round, on the order of up to 0.50 inch, which would have little impact on rivers and streams. There is the potential for heavier rainfall with the second round Saturday into Sunday, but it is still too early to specify amounts or possible impacts. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...None. && $$

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