Area Forecast Discussion
Issued by NWS Upton, NY

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358 FXUS61 KOKX 120849 AFDOKX Area Forecast Discussion National Weather Service New York NY 349 AM EST Wed Dec 12 2018 .SYNOPSIS...
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High pressure then builds in from the north through tonight. A weak upper level disturbance passes on Thursday. A frontal system and associated low pressure will then impact the area over the weekend before high pressure builds in for early next week.
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&& .NEAR TERM /THROUGH TODAY/...
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Upper level shortwave departs today while at the surface, high pressure builds in from the north. Cold air advection behind the front will mean a continuation of the below normal temperatures the area has been seeing as of late. Highs will top out in the middle 30s to near 40. Conditions will be mostly clear as subsidence from high pressure limits cloud formation.
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&& .SHORT TERM /TONIGHT THROUGH 6 PM THURSDAY/...
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Conditions remain dry through tonight as surface high pressure remains centered over southeastern Canada/northern New England and an upper level ridge moves through the Northeast. Low temperatures tonight will be problematic, especially for the outlying areas as clouds start to increase late tonight ahead of an approaching weak upper level low over the eastern Great Lakes region. Currently, the forecast is for temperatures to drop early in the night, but as the clouds move in, temperatures will remain steady or rise. However, if clouds move in later, temperatures will likely drop in the outlying areas, but if the clouds come in earlier, temperatures will remain steady or rise earlier than is currently forecast. The upper low will track near central or southern New York by Thursday afternoon. There will be a slight chance for precipitation for western areas during the late morning, with a slight chance for the entire area by the afternoon hours. However, the upper low will be weakening as it approaches and only very light amounts of precipitation are expected. As for precipitation type, precipitation could start off as all snow for most places. Much of New York City will start off as a rain/snow mix transitioning to all rain as the boundary layer warms up. By the afternoon, plain rain is expected across Long Island, New York City, and much of northeast New Jersey. The one concern will be the possibility of freezing rain across western Passaic and interior portions of the Lower Hudson Valley during the middle to late afternoon time frame. Soundings indicate the possibility of ice crystals NOT being present, while at the surface it will be at or below freezing, so any precipitation will fall as liquid and freeze on contact in these areas. Precipitation amounts will be very light, only looking at a couple of hundredths of an inch. If snow does accumulate, it will be limited to north and west of New York City, and only a couple of tenths of an inch, in other words a dusting. Again, the one concern would be the ice across the aforementioned interior locations. If this does end up happening, a Winter Weather Advisory would likely be needed. Do not have any ice accumulation in the forecast, but even a widespread trace amount of freezing rain would warrant an advisory. Will continue to monitor the situation.
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&& .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
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While any lingering showers or flurries should be offshore by Thursday night, the combination of light east-southeast flow and lingering low level moisture will result in the chance of patchy drizzle and/or freezing drizzle generally north and west of NYC. The best chance for any freezing drizzle appears to be across Orange, Putnam, and western Passaic counties, where moisture will linger the longest and temperatures will be several degrees below freezing. Thereafter, attention then turns to the frontal system progged to impact the region over the weekend. Models remain in good agreement with both the surface and upper level evolution of the system through early Saturday morning as low pressure slowly traverses the Lower Mississippi Valley. Thereafter, models diverge significantly, with the 00Z GFS allowing the closed low to drift much farther north, which has implications for the duration of precipitation over the area through the weekend. These differences are related to how the southern stream system interacts with numerous northern stream shortwaves, which will become better resolved as the energy comes onshore in the coming days. For now, the majority of the daylight hours on Friday look to remain dry as surface high pressure initially over the area drifts offshore. Rain then overspreads the area Friday night and continues into Saturday morning before beginning to taper off Saturday afternoon. At least a chance of rain could linger into Saturday night and Sunday, especially if the more northern low track comes to fruition. Dry weather then returns for the start of the next work week as high pressure builds in behind the departing low. Temperatures will be 5-10 degrees above normal on Friday and Saturday ahead of the system before falling back to near to slightly below normal for the remainder of the long terms period.
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&& .AVIATION /08Z WEDNESDAY THROUGH SUNDAY/...
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High pressure builds today. VFR today and into tonight. NW winds 10-15 kt are expected, with a few gusts 15-20 kt. Winds lighten later today and tonight as they veer to the NE. MVFR ceilings are possible late tonight. ...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: Winds right around 310 true through much of the day. The afternoon KJFK haze potential forecast is GREEN...which implies slant range visibility 7SM or greater outside of cloud. KLGA TAF Comments: Winds right around 310 true through much of the day. The afternoon KLGA haze potential forecast is GREEN...which implies slant range visibility 7SM or greater outside of cloud. KEWR TAF Comments: Winds right around 310 true through much of the day. The afternoon KEWR haze potential forecast is YELLOW...which implies slant range visibility 4-6SM outside of cloud. KTEB TAF Comments: No unscheduled amendments are expected. KHPN TAF Comments: No unscheduled amendments are expected. KISP TAF Comments: No unscheduled amendments are expected. .OUTLOOK FOR 06Z THURSDAY THROUGH SUNDAY... .Late tonight...MVFR ceilings possible. .Thursday...MVFR possible in flurries/sprinkles. .Friday...VFR/MVFR to start, then sub-VFR conditions likely late in rain. .Saturday...IFR likely in rain. .Sunday...Mainly VFR, but MVFR possible in rain.
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&& .MARINE...
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Gusty NW winds behind a cold front will mean SCA will continue with gusts of 25 to 30 kt on the ocean waters. Seas of 3 to 5 ft are also expected. Conditions will diminish through the day however as the high pressure builds in from the north. Winds and waves will then remain below SCA tonight and Thursday. A frontal system and associated low pressure will approach the area Friday night through Saturday. SCA may be needed starting on Saturday as winds and seas increase in response to the passing system. Ocean seas then appear to remain elevated into at least Sunday, although significant uncertainty remains in the evolution of the system during the second half of the weekend.
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&& .HYDROLOGY...
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No significant widespread liquid equivalent amounts expected through Friday. Rainfall amounts Friday night into Saturday will range from 0.5 to 1 inch across the region. This could result in minor flooding in poor drainage areas, otherwise the recent dry conditions should limit any flooding potential.
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&& .EQUIPMENT... NYC Central Park winds are out of service until further notice. Loss of data is due to a severed cable. Parts are on order. NYC NOAA Weather Radio Station KWO35 (162.55 MHz) will remain off the air for an extended period of time. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...Small Craft Advisory until noon EST today for ANZ353-355. Small Craft Advisory until 3 PM EST this afternoon for ANZ350. && $$ SYNOPSIS...FEB/JP NEAR TERM...JP SHORT TERM...JP LONG TERM...FEB AVIATION...PW MARINE...FEB/JP HYDROLOGY...FEB/JP EQUIPMENT...

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