Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 230130 AFDOKX Area Forecast Discussion National Weather Service New York NY 930 PM EDT SUN MAY 22 2016 .SYNOPSIS... Weakening low pressure heads up into the Canadian Maritimes tonight. Another weak low will approach the region from the south on Monday, passing to the south and east on Tuesday. High pressure will then briefly follow for Wednesday and Thursday with a cold front slipping south of the area Thursday night. The front returns north as a warm front on Friday. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/... As a weakening coastal low heads up into the Canadian Maritimes tonight, drying and subsidence on the backside of the low will result in clearing from NE to SW. There remains a slight chance of a shower this evening, mainly across the interior. Biggest change with this update was in decrease cloud cover through the night. There were also small adjustments based on initial conditions. Low temperatures will be near normal, ranging from the upper 40s to lower 50s. The Pine Barrens region of LI may get as low as the lower 40s. && .SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/... There will be a chance for showers once again north and west of New York City on Monday, with the upper level low still in the vicinity. Another coastal low will develop off the Mid-Atlantic coast and track northeast through Monday night. This will allow the chance for showers to overspread the region into the afternoon and continuing into Monday night. The best chances for precipitation will be late Monday night. Operational models have been keying in on a band of moderate rainfall that may affect the region. However, there is disagreement on when and where this will occur. The NAM shows this band of up to half an inch of rain in a 6 hour period between 2 am and 8 am over Long Island and New York City. GFS shows a quarter of an inch across Eastern Long Island from 8 pm to 2 am, then pivoting into Connecticut and the Lower Hudson Valley after 2 am. The ECMWF looks like a compromise between the two, with less in the way of precipitation. High temperatures will be near normal, in the upper 60s and lower 70s. && .LONG TERM /TUESDAY THROUGH SUNDAY/...
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While there is good overall agreement amongst the global models in taking a closed upper low northeast of the area Tue night with its associated sfc low passing east of LI, difference arise later in the week with short wave energy rounding the top of the building upper ridge across the eastern half of the conus. Anomalously warm heights aloft will feature the westward expansion of the the sub-tropical ridge into the eastern third of the country. This all points toward an unseasonably warm, and increasingly humid air mass toward the end of the week. The one caveat here is the aforementioned short wave energy riding over top the ridge Thu night into Fri morning. The 12Z guidance points toward a cold frontal passage Thu night into Fri. Differences arise with how far south it gets and how quickly the boundary returns to the north. The operational GFS and its ensemble mean keep the boundary south of the area through the weekend, while the ECMWF returns it north of the area Fri night. The Global GEM never gets it south of the area. So for the time, the forecast will ease into a solution of dropping the boundary to the south but quickly returning it north on Friday. However, should the other global guidance come around to the GFS, then a cooler forecast will be in store with an easterly flow undercutting the warm air aloft. While we are looking for unseasonably warm conditions Wed-Sun, temps have been nudged down several degrees Fri into Sat. The warmest conditions still remain across the interior with highs in the lower 80s and the 70s at the coast. As for rainfall, the best chance will be Tue with a good chance of showers on the west side of the upper low. There is the potential for some embedded thunderstorms during the afternoon hours. Rainfall amounts with this activity could be up to a few tenths of an inch with isolated higher amounts in any embedded stronger convection. It becomes much more sketchy at the end of the week with ridging aloft and likely capping. The GFS suggests the potential for an MCS at the southern edge of the westerlies The night into Fri with the frontal boundary serving as a lift source. It is much too early at this time to resolve such a feature but to note the potential with the synoptic scale setup.
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&& .AVIATION /02Z MONDAY THROUGH FRIDAY/...
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Low pressure well to the east departs and weakens into tonight. Another low will approach from the south Monday. VFR conditions much of tonight. with light/variable winds becoming NW late. Could see some brief MVFR vsby at some outlying terminals close to daybreak. N winds around 5 kt after daybreak should veer NE 5-10 kt and then ENE through the morning, then give way to afternoon sea breezes. Sea breeze onset should be at least 1 hour earlier than that of today, maybe 2 hours, and direction may initially be SE and then veer S. A brief mid to late shower or tstm possible at KSWF where there will be some instability. .OUTLOOK FOR 00Z Tuesday through Friday... .Monday night-Tuesday...Good chance MVFR or lower conditions in any showers and possible tstms. .Wednesday-Thursday...VFR. .Thursday night-Friday...MVFR or lower conditions possible in scattered showers/thunderstorms.
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&& .MARINE... Winds will remain below SCA criteria through the near and short term. Waves will remain above 5 ft across all ocean waters through tonight as they slowly diminish. 5 ft seas are possible a few hours after sunrise on Monday for the eastern ocean zone. For Tuesday afternoon into the evening, 5 ft seas could briefly impact the eastern ocean waters as another low passes to the east. Winds and seas will subside Tue night into Wed with high pressure building across the waters. && .HYDROLOGY... Between a quarter and a third of an inch of rain is forecast through Monday night. This should have little if any impact. An additional few tenths of an inch is possible during the day Tuesday, with locally higher amounts possible in any embedded stronger convection. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...Small Craft Advisory until 6 AM EDT Monday for ANZ350-353-355. && $$

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