Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 212001 AFDOKX Area Forecast Discussion National Weather Service New York NY 401 PM EDT SAT MAY 21 2016 .SYNOPSIS...
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Low pressure moves southeast of Long Island tonight and Sunday. An upper low over the Mid Atlantic States Monday morning lifts slowly northeast through mid week. High pressure will then briefly follow for Wednesday and Thursday with a frontal system approaching from the northwest late in the week.
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&& .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
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Upper trough amplifies as it tracks east tonight per model consensus. At the sfc, low pressure off the Mid Atlantic coast will track just southeast of the 40N/70W benchmark. The trend toward less QPF continues, and have lowered pops somewhat from previous forecast. Pops layered from categorical across Long Island, to chance pops interior. Temps range from the upper 40s to mid 50s under cloudy skies.
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&& .SHORT TERM /6 AM SUNDAY MORNING THROUGH SUNDAY NIGHT/...
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Upper trough closes off over the Mid Atlantic states this time frame. At the sfc, initial area of low pressure moves northeast Sunday as secondary low develops ahead of closed low and moves off the mid atlantic coast. Most model solutions produce very little QPF across our area. A few stray showers are possible due to the presence of the upper trough, but not much of a trigger for shower development noted. Clouds in the morning will give way to partial sunshine during the afternoon, with partly cloudy skies continuing Sunday night. High`s will range from the lower 70s to the mid 60s Sunday, with lows at night in the 50s, with some upper 40s possible.
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&& .LONG TERM /MONDAY THROUGH SATURDAY/...
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Global models continue to slow down with the progress of an upper trough over the Eastern U.S. at the start of the week. A closed low at the base of the trof over the Mid Atlantic states, will lift slowly north into Tue, and then northeast Tue night into Wed. There are some discrepancies amongst the guidance with how quickly this feature lifts out, with the operational GFS being the slowest of the operational solutions. The interaction with a northern branch trof moving across Hudson Bay appears to the kicker, with the magnitude of this feature varying. A model consensus approach seems to be best here with the differences being rather small for this juncture in time. Upper level ridging then expands across the area for the second half of the week with very warm conditions to ensue. In addition, the Sub tropical high over the western Atlantic begins to retrograde toward the East Coast at the close of the period. This will allow for a moist SW flow to develop around the periphery of the high. As for any rain, the best chance looks to be Mon eve into Tue with the approach of the upper low. The GFS is the deepest, farthest west, and slowest with the sfc low. Model consensus is for a weaker and faster low, thus will keep rain chances at around 50 percent. There is general agreement for up to a few tenths of an inch across the area. There could even be some isolated thunderstorms Tue aft/eve with the steepening lapse rates with the upper trof overhead. It becomes much more sketchy at the end of the week with ridging aloft and likely capping. A frontal system approaches from the NW, but will likely struggle reaching the area. Chance of convection at this time is low. Near seasonable temps at the onset of the period, will become unseasonably warm from mid week into the weekend with many locations away from the coast getting into the lower 80s, possibly warmer.
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&& .AVIATION /19Z SATURDAY THROUGH THURSDAY/...
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s of 20Z, no limitation to visibilities with any of the rain that moved through the city terminals. This area of rain will weaken as it moves east across Long Island and should have little, if any impact to eastern terminals. Another round of very light rain is forecast to move into the city terminals after 22Z. Again, this should have little impact to visibilities and ceilings should remain VFR. MVFR ceilings with light rain begin to move into the area mainly after 01Z Sunday as low pressure deepens along the Carolina coast. Some terminals may even remain VFR the entire TAF period, mainly for terminals away from the coast. TEMPO showers from 07Z through 11Z Sunday as the rain tapers off. By 12Z Sunday the low is expected to be well southeast of Montauk Point. Dry conditions expected to return by this time. Winds should shift to the northeast as the low pulls away from the region. Sea breeze is likely to develop at KJFK after 16Z Sunday. .OUTLOOK FOR 12z Sunday through Thursday... .Sunday-Tuesday...VFR. However, a few showers will be possible from time to time with local MVFR conditions. .Wednesday-Thursday...VFR.
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&& .MARINE...
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As low pressure approaches the waters from the south this evening, winds will back around to the northeast and pick up in speed, mainly over the ocean waters. Seas are expected to build per nearshore wave prediction model, and wave watch III output. Will maintain SCA for the ocean waters tonight, but these conditions may not be realized until around or shortly after midnight. The area of low pressure moves northeast Sunday, but a secondary area of low pressure will develop well to the south. Winds diminish Sunday between the two lows, but lingering rough seas continue through this time frame. SCA seas will linger into Tue as one area of low pressure departs to the NE and another area approaches from the South. Winds and seas will subside Tue night into Wed with high pressure building across the waters.
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&& .HYDROLOGY...
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Around a quarter of an inch or less of QPF is expected tonight with the highest amounts closer to the coast. No hydrologic issues are anticipated. Showers Mon into Tue will bring potentially a few tenths at a time where they do occur.
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&& .OKX WATCHES/WARNINGS/ADVISORIES...
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CT...None. NY...None. NJ...None. MARINE...Small Craft Advisory until 6 AM EDT Monday for ANZ350-353-355.
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&& $$ SYNOPSIS...PW NEAR TERM...PW SHORT TERM...PW LONG TERM...DW AVIATION...JP MARINE...DW/PW HYDROLOGY...DW/PW

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