Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 181811 AFDOKX Area Forecast Discussion National Weather Service New York NY 111 PM EST Wed Jan 18 2017 .SYNOPSIS...
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Low pressure continues to work farther offshore and gradually strengthens 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/... Only minimal changes needed to the forecast to reflect current temperature/dew point trends. The 1010 mb surface low is southeast of Long Island as of 17z. 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. && .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 /18Z WEDNESDAY THROUGH MONDAY/...
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Offshore low pressure continues to work away from the terminals through tonight, while high pressure works in from the west. The theme will be gradual improvement through tonight as widespread IFR cigs at the onset lift to MVFR this afternoon and then VFR overnight. Areas of fog possible tonight. N-NE winds this afternoon will gradually back to the N-NW through tonight. Speeds around 10 kt or less expected, a bit higher at the city terminals. 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 timing of improving flight categories. KLGA TAF Comments: Amendments likely for timing of improving flight categories. KEWR TAF Comments: Amendments likely for timing of improving flight categories. KTEB TAF Comments: Amendments likely for timing of improving flight categories. KHPN TAF Comments: Amendments likely for timing of improving flight categories. KISP TAF Comments: Amendments likely for timing of improving flight categories. .OUTLOOK FOR 18Z THURSDAY THROUGH MONDAY... .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. .Monday...Chance of IFR with heavy rain and strong E-NE winds.
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&& .MARINE... Surface winds have backed to a more north-northeasterly direction as the low has now moved southeastward of Long Island. Gusts 20-25kt are currently being measured on the ocean waters. Seas are rising in response, with 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. && .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... 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. && $$ SYNOPSIS...Goodman/JM NEAR TERM...MD/Goodman SHORT TERM...Goodman LONG TERM...JM AVIATION...DW MARINE...Goodman/JM HYDROLOGY...Goodman/JM

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