Area Forecast Discussion
Issued by NWS Upton, NY

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884 FXUS61 KOKX 190907 AFDOKX Area Forecast Discussion National Weather Service New York NY 507 AM EDT Mon Mar 19 2018 .SYNOPSIS... High pressure builds in from the northwest through tonight. An area of low pressure approaches from the south for Tuesday. Stronger low pressure will develop off the southern Mid Atlantic coast Tuesday night, pass slowly southeast of the area Wednesday into Wednesday night, and then to the east on Thursday. High pressure will then build from southern Canada from Friday through Saturday. Another storm system will move from the Ohio River Valley to the Mid Atlantic States Saturday night, then pass south of Long Island on Sunday. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Cold and dry advection is expected today as Arctic high pressure builds in from the northwest. As such, well below normal temperatures will continue, with highs more in line with what can be expected in February than in mid March. Skies will be mostly clear with the exception of a few mid and high level clouds moving in from the west. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/... Although cold and dry advection continues into the night with high pressure building to the north-northwest, winds and cloud cover will gradually increase overnight ahead of the approaching low pressure system. Despite the cooler than normal temperatures, the increase in cloud cover and winds should inhibit more favorable conditions for radiational cooling, keeping a few locations, particularly across the pine barrens of Long Island, a few degrees warmer than Sunday night. With a dry air mass expected to be in due to the antecedent Arctic high pressure, have gone with slower solutions for the onset of precipitation on Tuesday, with most locations remaining dry with the exception of perhaps northeast NJ, NYC and Long Island where there will be at least a slight chance to chance of light snow or a rain/snow mix by late afternoon. Any accumulations will be minimal and unlikely to stick to sidewalks and/or roads. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... Longer range guidance appears to have come into more focus for the Tue night-Wed night time frame, but still differs on the northward extent of the cutoff low that moves across the OH Valley Tue night and then passes off the Mid Atlantic coast on Wed, which would impact the placement of mesoscale banding that could impact our area with heavier precip. ECMWF/UKMET are most aggressive with a more northward/snowier trend, a blend of which would bring the likelihood of a 6+ inch snowfall to at least the NYC Tri-State area, Long Island, and the CT coast, and at least advy-level amounts to nearly all the rest of the area. The less aggressive (but still trending wetter) GFS and the CMC global would lead to advy amounts over 3 inches across Long Island, a 1-2 inch snowfall most elsewhere, and little to no accumulation across the interior Hudson Valley. The NAM has been rather inconsistent the last 3 runs, with the 18Z offering up a major snowstorm to the entire CWA, while the 00Z kept most snow east of NYC, and the 06Z trended northward with a warning level snowfall for Long Island. Given its inconsistency, for the time being have sided more with a blend of the global models on QPF, and played it a little conservative on snow-to-liquid ratios, with a solid advy-level event except across Orange/Putnam/W Passaic. If the overall guidance trend continues northward, the ECMWF/UKMET scenario would be realized, so will continue to mention this in the HWO. With low levels drying behind the storm, even with passage of trough axis on Thursday/Thursday night, it should be dry. Another shortwave pushes through Friday, but once again the dry low levels should preclude any precipitation. Shortwave ridging crosses the area Friday night and Saturday, so it should continue to be dry. The next storm system comes in response to a northern stream trough/developing closed low moving into the Great Lakes/Southern Canada Saturday night and Sunday. At this time there is the potential for mainly snow inland, and a rain/snow mix for NYC metro and Long Island. Temperatures will remain below normal. && .AVIATION /09Z MONDAY THROUGH FRIDAY/... High pressure extending from central Canada builds in today. VFR. Light winds will become E/NE prior to sunrise around 5-10 kt as low pressure passes just to the SW of NYC. These winds back to the N-NW around 10 kt around sunrise. Directions should remain primarily right of 310 magnetic in NYC metro through the day, although some turn to the west is possible mid afternoon. Winds turn back to the N/NE by evening and lighten to under 10 kt. ...NY Metro Enhanced Aviation Weather Support... Detailed information, including hourly TAF wind component forecasts, can be found at: KJFK TAF Comments: Low confidence in wind direction forecast after 18Z. Winds may back to the left of 310 magnetic, but remain uncertain at this time. The afternoon KJFK haze potential forecast is GREEN...which implies slant range visibility 7SM or greater outside of cloud. KLGA TAF Comments: Low confidence in wind direction forecast after 18Z. Winds may back to around 310 magnetic, but remain uncertain at this time. The afternoon KLGA haze potential forecast is GREEN...which implies slant range visibility 7SM or greater outside of cloud. KEWR TAF Comments: Low confidence in wind direction forecast after 18Z. Winds may back some, but should remain to the right of 310 magnetic. The afternoon KEWR haze potential forecast is GREEN...which implies slant range visibility 7SM or greater outside of cloud. KTEB TAF Comments: No unscheduled amendments are expected. KHPN TAF Comments: No unscheduled amendments are expected. KISP TAF Comments: Lower confidence in wind direction forecast after 18Z as winds may back toward the west. .OUTLOOK FOR 06Z TUESDAY THROUGH FRIDAY... .Late tonight...VFR. .Tuesday...Generally VFR except MVFR or lower possible in snow late in the day. Highest probability for NYC metro/coastal terminals. ENE winds G20 KT NYC metro/coastal terminals. .Tuesday night...MVFR conditions possible with any lingering snow. NE winds G20-30KT NYC metro/coastal terminals. .Wednesday...Snow with IFR or lower conditions likely, especially for coastal terminals. NE winds G20-30KT. .Thursday-Friday...VFR. N winds G15-20KT on Thu. && .MARINE... Winds and seas will remain tranquil today as high pressure builds in from the north and west. Winds then gradually begin to strengthen tonight between the high to the north and an approaching low pressure system to the south, allowing winds and seas to increase to SCA-levels by Tuesday afternoon/evening. Have issued a gale watch for the ocean for Tue night into Wed, as E- NE winds rapidly increase in response to the development of the coastal low. Expect gusts mainly 35-40 kt during this time, and peak gust up to 45 may be possible on the outer ocean waters. A few gusts to gale force may even be possible on the eastern Sound and the bays of Long Island, but overall solid SCA level conditions expected on the remaining waters. Gales may linger on the ocean into Wed evening, otherwise SCA conds expected on all waters for most of Wed night. The pressure gradient then gradually slackens from Thursday through Friday, with SCA conds lingering on the ocean into Thu and possibly Thu night. && .HYDROLOGY... It will be mainly dry through tonight. There is the potential for a prolonged period of precipitation from Tuesday through Wednesday night. Total liquid equivalent precip should likely remain below an inch, falling as snow, so no hydrologic impact expected. && .TIDES/COASTAL FLOODING... There is the potential for a prolonged period of E-NE flow from Monday night into Wednesday Night. Tidal departures of generally only 1 to 1 1/2 ft are needed for minor flooding for many locations Tuesday night through Wednesday night, and 2 to 3 ft for moderate. Depending on the exact track/strength of a coastal low or lows during this time frame, there is the potential for minor to moderate coastal flooding, but predictability on the details remains low. && .EQUIPMENT... NYC NOAA Weather Radio Station KWO-35 (162.55 MHz) is off the air for an extended period of time. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...Gale Watch from Tuesday evening through Wednesday afternoon for ANZ350-353-355. && $$ SYNOPSIS...MD/Goodman NEAR TERM...MD SHORT TERM...MD LONG TERM...Goodman AVIATION...PW MARINE...MD/Goodman HYDROLOGY...Goodman TIDES/COASTAL FLOODING... EQUIPMENT... is the U.S. government's official web portal to all federal, state and local government web resources and services.