Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 220850 AFDOKX Area Forecast Discussion National Weather Service New York NY 350 AM EST Wed Nov 22 2017 .SYNOPSIS...
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Rain this morning ends from west to east as a cold front moves through. High pressure builds in Wednesday through the end of the week. A cold front crosses Saturday night, with high pressure building in from the west for the beginning of next week.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Jet Dynamics resulting in very rapid development of the rain event for this morning with Cold FROPA resulting in a rapid end from mid morning to mid afternoon (west to east). The right rear jet entrance to the 120+ KT is the forcing. Rather complex, but interesting pattern. High resolution CAM`s and HREF appear to have good handle on the pattern/timing - uncertainty though lies in the QPF. Have gone with around 1/4" for the City and 3/4" for the Twin Forks of Suffolk County. 06Z NAM has gone back to 1.5" and is consistent with the RAPx (Version 4). While the operational RAP/HRRR time-lagged runs keep with what we`ve gone with. Other uncertainty is will back edge be west or east of the NY Metro? Have followed the short range NWP guidance here and gone with categorical POPs well west of the NY Metro. BUT - looking at RADAR as of 3 AM, have to wonder if this will happen? I think the jet dynamics will evolve over the next few hours "widening" and pulling the band of precip west over the Metro and lower Hudson Valley. It`s a quick shot for the City with rain ends around 10 AM. Thank goodness it`s not February and we were dealing with snow! A nice case for zero to 12+" of uncertainty in the first few hours of the forecast. Otherwise - skies clear and NW winds gust up to 25 mph by late afternoon as CAA sets in.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/...
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Clear, with diminishing winds overnight allows for radiational thermal decoupling in the rural areas. A blend of MOS was used with near freezing in the NY Metro for lows forecast. Sunny and chilly, but with a light wind for Thanksgiving. Cooler NAM/ECMWF blend seems best for temps (about 8 degrees below normal).
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&& .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
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High pressure at the surface, pushes off the East Coast late Friday into Friday night as a warm front over the Eastern Great Lakes lifts well north of the area. Warm air advection doesn`t seem to kick in until Friday evening, so dry and continued cool for Friday, but slightly warmer than Thursday with highs in the middle to upper 40s. Another cold front approaches the area late Saturday and passes through Saturday night. Southwesterly flow ahead of the front will bring temperatures to normal levels to above normal levels, in the upper 40s to upper 50s. 00Z GEFS keeps it dry. A secondary cold front moves through on Sunday with a reinforcing shot of cold air. Some instability with the colder air aloft associated with the upper level trough may produce some light rain showers. High pressure then keeps the area dry through the beginning of next week.
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&& .AVIATION /08Z WEDNESDAY THROUGH SUNDAY/...
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A cold front approaches from the west early this morning, then crosses the area later this morning. A coastal low passes to the east of Long Island this afternoon. High pressure then builds in from the west into tonight. MVFR conditions develop towards daybreak as rain overspreads the terminals, except IFR conditions at KHPN/KISP/KGON. There is a chance that the city terminals have IFR conditions during the morning, as well, but confidence in this is too low to put in the TAFs at this time. Rain likely ends by around noon for the city terminals and points west, and early afternoon farther east. There is a low chance for isolated thunderstorms at KGON and KISP through around 15z. Light and variable winds become NW and increase by mid morning. 20-25KT gusts become frequent during the afternoon, then taper of during the evening. ...NY Metro Enhanced Aviation Weather Support... Detailed information, including hourly TAF wind component fcsts, can be found at: http://www.weather.gov/zny/n90 KJFK TAF Comments: Timing of changes in wind speed, direction and gusts could be off +/- 1-2 hours. Low chance of IFR conditions this morning. Moderate to high confidence in winds to the right of 300 True/310 Magnetic this afternoon. The afternoon KJFK haze potential forecast is green...which implies slant range visibility 7SM or greater outside of cloud. KLGA TAF Comments: Timing of changes in wind speed, direction and gusts could be off +/- 1-2 hours. Very low chance of IFR conditions this morning. Moderate to high confidence in winds to the right of 300 True/310 Magnetic this afternoon. The afternoon KLGA haze potential forecast is green...which implies slant range visibility 7SM or greater outside of cloud. KEWR TAF Comments: Timing of changes in wind speed, direction and gusts could be off +/- 1-2 hours. Very low chance of IFR conditions this morning. Moderate to high confidence in winds to the right of 300 True/310 Magnetic this afternoon. The afternoon KEWR haze potential forecast is green...which implies slant range visibility 7SM or greater outside of cloud. KTEB TAF Comments: Timing of changes in wind speed, direction and gusts could be off +/- 1-2 hours. Very low chance of IFR conditions this morning. KHPN TAF Comments: Timing of changes in wind speed, direction and gusts could be off +/- 1-2 hours. There is a low chance conditions do not fall to IFR and only to MVFR. KISP TAF Comments: Timing of changes in wind speed, direction and gusts could be off +/- 1-2 hours. There is a very low chance conditions do not fall to IFR and only to MVFR. There is a low chance that IFR conditions could linger up to a few hours longer than forecast. .OUTLOOK FOR 06Z THURSDAY THROUGH SUNDAY... .Late tonight-Friday night...VFR. NW winds G15-20KT possible late tonight/Thursday morning. SW winds G15-20KT possible Friday night, mainly at eastern terminals. .Saturday-Saturday night...MVFR possible. W-NW winds G15-20KT possible Saturday night. .Sunday...Becoming VFR. NW winds G20-30KT possible.
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&& .MARINE...
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SCA continues for the ocean waters as seas will be slower to subside. A cold front will be moving east of the forecast waters this afternoon as high pressure builds to the west, with SCA gusts likely all waters in its wake. 5 to 6 ft waves on the ocean waters on Thursday as a northwest flow shifts to the west-southwest. Waves will diminish Friday, generally coming down below 5 ft for most areas on the ocean by Friday afternoon. Waves increase again on the ocean late Friday night as a southwesterly flow sets up ahead of an approaching cold front, diminishing Saturday night. Winds should generally remain below 25 kt until Sunday afternoon as a northwest flow strengthens behind the passage of a cold front. Winds should remain above 25 kt from Sunday evening throughout the rest of the long term.
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&& .HYDROLOGY...
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Rain this morning 1/4-3/4" with the potential for up to 1.5 inches across Long Island to SE CT. Some urban ponding possible. Otherwise, No hydrologic problems are anticipated the next 7 days.
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&& .OKX WATCHES/WARNINGS/ADVISORIES...
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CT...None. NY...None. NJ...None. MARINE...Small Craft Advisory from 3 PM this afternoon to midnight EST tonight for ANZ330-335-338-340-345. Small Craft Advisory until 6 AM EST Thursday for ANZ350-353- 355.
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&& $$ SYNOPSIS...Tongue NEAR TERM...Tongue SHORT TERM...Tongue LONG TERM...Tongue AVIATION...Maloit MARINE...Tongue HYDROLOGY...Tongue

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