Area Forecast Discussion
Issued by NWS Upton, NY

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732 FXUS61 KOKX 221752 AFDOKX Area Forecast Discussion National Weather Service New York NY 152 PM EDT Sat Apr 22 2017 .SYNOPSIS... A couple of weak waves of low pressure will pass to the south and east of Long Island today into this evening. High pressure will then slowly build into the region from the west tonight, and across the area on Sunday, then move offshore on Monday. A wave of low pressure will move off the Southeastern coast Monday, and track slowly north through midweek. High pressure will build back in for the end of the week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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A northern stream shortwave trough will approach the region from the west this afternoon. At the surface...a couple of weak waves of low pressure will track east today...along a cold front slowly pushing well se away from the region. Light rain and sprinkles will slowly taper off from NW to SE through this evening...tapering off across NYC/LI by around midnight. Expect temps to hold in the 50s across most of the area. If breaks of sun can materialize across interior portions of the region this afternoon...lower 60s possible.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SUNDAY/... With the slower movement of the upper trough and weak building heights to the west, have probabilities into this evening along the coast, and just south of Long Island this evening. If the trough is slower to move east, precipitation may remain longer across eastern Long Island and southeastern Connecticut. Otherwise high pressure builds for the remainder of tonight. && .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/... With the weak high to the north moving east and weakening farther the southern low now is expected to move north a little faster and have introduced probabilities into the region Monday morning. A split upper flow across the Eastern U.S. will feature a departing shortwave trough across the Northeast at the onset of the period, with an anomalously far south closed low moving into the southeast. The latter of which will likely bring some inclement weather to the area for the first half of next week. High pressure will initially be in place Sunday into Monday with some uncertainty to the northern extent of the rain shield during this time. A confluent upper flow will reside across the area at the start of the period, with a deep layered W/SW flow converging with the northern branch of the polar jet. Initial thinking is this should keep the area under subsidence and drying, but any shift in this zone could bring light rain/clouds in sooner. The best timing for a steady rain appears to be Monday night through Tuesday night as the upper low moves offshore and warm, moist air overruns the region. This mainly appears to be an overrunning rain event. Up to an inch rainfall seems to be a reasonable possibility at this time. High pressure follows Wednesday night into Thursday with model differences on the amplitude of a deepening western trough and the ridging east of the Mississippi River Valley. A weakening cold front works across the area on Thursday per the GFS and GGEM, while the ECMWF dissipates it to the west. Leaned toward the ECMWF at this time, but these details are far too early to resolve. As for temperatures, near seasonable levels through mid week, if not a bit cooler during the daytime due to cloud cover and rain. A significant warmup is possible for the end of the week with warming heights aloft. && .AVIATION /18Z SATURDAY THROUGH THURSDAY/...
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Waves of low pressure will move along a frontal boundary located to the south into this evening. High pressure will build in from the west tonight. Mainly VFR this afternoon, with MVFR cigs possible in any light rain through 22Z. VSBY should remain VFR. NE winds will gradually back to the NW this afternoon. Speeds should remain around 10 kt or less. Winds will stay to the right of 310 magnetic at the city terminals. .OUTLOOK FOR 18z SUNDAY THROUGH THURSDAY... .Sunday...VFR. .Monday...VFR during the day. Chance MVFR in rain at night. .Tuesday...Chance IFR in rain. NE gusts 20-25 KT near coast possible. .Wednesday...MVFR possible early, becoming VFR. .Thursday...Possible MVFR.
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&& .MARINE... 5 ft E swells on the ocean should gradually subside this afternoon...which will allow seas to fall below SCA levels. 5 ft seas may briefly develop on the eastern ocean waters once again tonight as NW winds increase to 15 to 20 kt. Winds and seas will fall below SCA levels Sunday into Monday as high pressure builds from the north tonight into Sunday night. The high weakens Monday as low pressure moves off the southeastern coast begins to track slowly to the north. The low pressure system moving off the southeastern coast Monday will track slowly north through midweek. A prolonged and increasing easterly flow will set up from Monday night into Wednesday. There may be a period of gusts approaching small craft levels on the ocean waters Tuesday and Tuesday night. However, with the easterly flow, ocean seas are expected to build to small craft levels by late Monday night and remain into Wednesday. As the low tracks through the forecast waters and weakens Wednesday winds will remain below small craft levels, but seas will be slow to subside below small craft. && .HYDROLOGY...
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An additional tenth of an inch of rainfall is possible into this evening, mainly from portions of northeastern New Jersey, across New York City, and Long Island. Lower amounts to the north. Up to an inch of rainfall is possible late Monday into Wednesday. No hydrologic impacts are anticipated at this time.
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&& .TIDES/COASTAL FLOODING... Potential for minor coastal flooding for vulnerable coastal communities with the Tue high tide cycles due to a potential coastal storm working up the coast. The evening cycle may have the higher threat as only 1/2 to 1 ft of surge is needed to reach minor flood thresholds. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...Small Craft Advisory for hazardous seas until 6 PM EDT this evening for ANZ350-353. && $$ SYNOPSIS...MET NEAR TERM...MET/NV SHORT TERM...MET LONG TERM...MET/DW AVIATION...CB MARINE...MET HYDROLOGY...MET TIDES/COASTAL FLOODING...NV

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