Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 180954 AFDOKX Area Forecast Discussion National Weather Service New York NY 454 AM EST Wed Jan 18 2017 .SYNOPSIS...
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Weak low pressure passing south of Long Island before daybreak 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 south of eastern Long Island as of 09Z, with associated steady rainfall mainly east of NYC, and a few light showers over northern NJ. 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 in the wake of the departing surface low to keep overcast skies and lingering light rain/drizzle around, 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. Spotty light freezing rain/freezing drizzle is still possible early this AM in the highest elevations of Orange/Western Passaic/Rockland/Putnam, primarily above 750 ft, where air and ground temps are at or just below freezing. Temps in CT have warmed a little, so this threat appears over for far northern Fairfield. 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/...
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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.
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&& .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
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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.
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&& .AVIATION /09Z WEDNESDAY THROUGH SUNDAY/...
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Low pressure moves south and east of Long Island through this evening. Mainly LIFR early this morning with gradual improvements to IFR around mid morning. Conditions slowly improve to MVFR from W to E into the afternoon and evening. NE winds veer to the N this morning and then NW through the afternoon. Speeds generally 10 kt or less. 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: Some fluctuation in flight category possible through around 10z, but LIFR should prevail. Timing of improving flight categories may be off by +/- 1-2 hours. KLGA TAF Comments: Some fluctuation in flight category possible through around 10z, but LIFR should prevail. Timing of improving flight categories may be off by +/- 1-2 hours. KEWR TAF Comments: Timing of improving flight categories may be off by +/- 1-2 hours. The afternoon KEWR haze potential forecast is YELLOW...which implies slant range visibility 4-6SM outside of cloud. KTEB TAF Comments: Ceilings expected to fall to LIFR through 10z. Timing of improving flight categories may be off by +/- 1-2 hours. KHPN TAF Comments: Timing of improving flight categories may be off by +/- 1-2 hours. KISP TAF Comments: Timing of improving flight categories may be off by +/- 1-2 hours. .OUTLOOK FOR 06Z THURSDAY THROUGH SUNDAY... .Late Tonight...Becoming VFR. .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.
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&& .MARINE...
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Easterly flow ahead of the low south of Long Island has pushed seas above 5 ft on the ocean E of Moriches Inlet. After the low passes, increasing northerly flow should eventually gust up to 25 kt, with 5+ ft seas spreading westward this afternoon, with SCA conds on all ocean waters by late day, and continuing into Thu. Some residual SCA seas of 5 ft are possible on the ocean Thursday evening. SCA conditions are possible on the ocean on Sunday, and for all waters on Monday. Gales may be possible on the ocean Monday afternoon/evening. Ocean seas could reach 6-11 ft Sunday night into early next week as an easterly fetch sets up.
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&& .HYDROLOGY...
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For Sunday night into early next week, low pressure could bring a significant rainfall of 1-2 inches. Some minor flooding may be possible.
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&& .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. Small Craft Advisory from noon today to 6 PM EST Thursday for ANZ353.
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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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