Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 181208 AFDOKX Area Forecast Discussion National Weather Service New York NY 708 AM EST Wed Jan 18 2017 .SYNOPSIS...
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Weak low pressure passing south of Long Island early this morning will move out to sea and gradually strengthen through tonight. Meanwhile weak high pressure will build from the west tonight into Thursday, and settle overhead Thursday night into early Friday. A weakening frontal system will approach Friday night into Saturday, and then dissipate. Strengthening low pressure will approach from the southwest from Sunday into Monday while a gradually strengthening high builds into the Canadian Maritimes. The low will continue to approach Monday night into Tuesday while slowly weakening.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Sfc obs indicate a 1010 mb low still south of eastern Long Island as of 11Z. Most of the associated steady light rain has moved to the east, with leftover patchy fog and drizzle remaining. Spotty light freezing rain/freezing drizzle is likely still occurring early this AM in the highest elevations of Orange/Western Passaic/Rockland/Putnam, primarily above 750 ft, where air and ground temps remain at or just below freezing. After the surface low passes, and as a mid level low moves into the Mid Atlantic region, weak sfc troughing and cyclonic flow should linger, maintaining overcast skies and lingering light rain/drizzle, especially across central/eastern Long Island where orographic lift of the nearly saturated air mass will also come into play as sfc flow backs northerly. Highs today should be from the upper 30s well inland, to the lower/mid 40s elsewhere, per MAV/MET blend which was on the mark yesterday.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/... Low level moisture will remain trapped beneath an inversion, but as shortwave mid level ridging passes across this evening behind the mid level low moving out over the Atlantic, there could be a break in any light rain/drizzle before another mid level shortwave trough approaches and moves across NY and New England after midnight. Still the possibility for some spotty light freezing rain/freezing drizzle well inland as temps drop to the upper 20s well inland, to the mid 30s across NYC metro and Long Island. Deep layer high pressure should return on Thu as this next shortwave trough passes east. After any early to mid morning clouds and patchy fog, afternoon sunshine and a drying downslope NW flow should send temps into the lower 50s across NYC metro and Long Island on Thu, with mid/upper 40s inland. && .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/... In the mid to upper levels, a more amplified pattern is shaping up starting Thursday night and going into early next week. There will be intermittent influences from the upper level subtropical jet, the most prominent being Sunday night through Monday night. This is when jet stream speeds will be the highest on average. At the surface, two frontal systems will be featured in the long term making for the next chances of precipitation. The first being Friday night into Saturday associated with a weakening frontal system. These features essentially dissipate Saturday leaving the region on the western side of a broad weak area of high pressure. A stronger frontal system approaches late Sunday into early next week with some more baroclinicity as evidenced from the sharpening wavelengths. The winds pick up and set up an easterly fetch in response to an increasing pressure gradient as a strengthening high pressure builds southward from Southeast Canada and this strong frontal system approaches from the Southeast U.S. The persistent fetch may lead to some possible coastal flooding as we approach a new moon which will be a few days later. Too soon to tell how much surge there will be though. The high eventually traverses Nova Scotia and settles southeast of there in the Northern Atlantic, keeping the region in an easterly flow. With a cool maritime airmass in place, there will be a low chance of rain mainly on Friday night associated with the approach of the first week frontal system. Amounts of rain forecast from this look to remain under a quarter of an inch. The second stronger frontal system will have both higher chances of rain plus larger rainfall amounts due to the longer period of time of rain forecast. Chances of rain begin mainly Sunday afternoon and will be highest (mainly between 50-60 percent) on Monday and Monday night. See hydro section for further details on this event. Both of the aforementioned systems look to be mainly rainfall with the setup and positioning of the forecast high and low pressure areas. Across the interior areas, some mixing with sleet will be possible late Sunday night into early Monday. Temperatures during the long term look to remain above normal. Highs mainly in the 40s except for Saturday and Tuesday when highs are forecast more into the low 50s on average. Relatively coldest night forecast is Thursday night when lows are forecast to range from the mid 20s to mid 30s. Otherwise other nights in the long term are forecast to have lows mainly in the 30s with NYC not deviating too much from the 40 degree mark. && .AVIATION /12Z WEDNESDAY THROUGH SUNDAY/... Low pressure moves south and east of Long Island today followed by high pressure building in from the west tonight. Mainly IFR this morning with pockets of LIFR. IFR is expected to continue through the morning with gradual improvements to MVFR this afternoon. There is some potential for IFR conditions to linger through the afternoon and possibly into the evening. Improvements in flight categories should occur tonight with VFR likely by daybreak Thursday morning. NE winds this morning will back to the N and then NW this afternoon and evening. Speeds around 10 kt or less expected. 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 for flight categories as duration of IFR is a bit uncertain. Winds back to the NW this afternoon staying to the right of 310 magnetic. KLGA TAF Comments: Amendments likely for flight categories as duration of IFR is a bit uncertain. Winds back to the NW this afternoon staying to the right of 310 magnetic. KEWR TAF Comments: Amendments likely for flight categories as duration of IFR is a bit uncertain. Winds back to the NW this afternoon staying to the right of 310 magnetic. The afternoon KEWR haze potential forecast is YELLOW...which implies slant range visibility 4-6SM outside of cloud. KTEB TAF Comments: Amendments likely for flight categories as duration of IFR is a bit uncertain. KHPN TAF Comments: Improvement in flight category from LIFR to IFR this morning could be off by a few hours. IFR may linger longer this afternoon than indicated. KISP TAF Comments: Amendments likely for flight categories as duration of IFR is a bit uncertain. .OUTLOOK FOR 12Z THURSDAY THROUGH SUNDAY... .Thursday-Friday...VFR. .Friday night...Chance of MVFR or lower in -RA. .Saturday-Saturday night...VFR. .Sunday...Chance of MVFR of lower in -RA, with best chance at CT/Long Island Terminals. && .MARINE...
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Easterly flow ahead of the low south of Long Island is producing SCA conditions on the ocean E of Fire Island Inlet, and wind gusts on the eastern Sound/Bays have briefly peaked at 25 kt per Central Sound buoy ob. As the surface low just south of Long Island passes, winds should back northerly and increase once again, with gusts up to 25 kt, and 5+ ft seas spreading westward to all ocean waters late today. These SCA conds should continue into Thu afternoon, with some residual 5-ft seas still possible Thu evening. SCA conditions are possible on the ocean on Sunday, and for all waters on Monday, with the approach of the next storm. Gales may be possible on the ocean Monday afternoon/evening, and ocean seas could reach 6-11 ft Sunday night into early next week as an easterly fetch sets up.
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&& .HYDROLOGY... For Sunday night into early next week, low pressure could bring a significant rainfall of 1-2 inches. Some minor flooding may be possible. && .OKX WATCHES/WARNINGS/ADVISORIES...
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CT...None. NY...None. NJ...None. MARINE...Small Craft Advisory from 4 PM this afternoon to 6 PM EST Thursday for ANZ355. Small Craft Advisory until 6 PM EST Thursday for ANZ350-353.
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&& $$ SYNOPSIS...Goodman/JM NEAR TERM...Goodman SHORT TERM...Goodman LONG TERM...JM AVIATION...DS MARINE...Goodman/JM HYDROLOGY...Goodman/JM

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