Area Forecast Discussion
Issued by NWS Upton, NY

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227 FXUS61 KOKX 300229 AFDOKX Area Forecast Discussion National Weather Service New York NY 1029 PM EDT FRI JUL 29 2016 .SYNOPSIS... Low pressure moves south and east of the region through this evening. High pressure then briefly builds into the region tonight into the first half of Saturday. This high shift towards the New England coast for remainder of the weekend as low pressure slowly approaches from the Ohio Valley. This low slowly moves along a frontal boundary to the south into early next week. High pressure then returns for the middle of the week. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/... Any showers have dissipated over the area. Only minor changes made to reflect current observations. Drier air in the middle and upper atmosphere as seen on water vapor continues to move over the area behind the departing low. This has allowed for clearing skies with a fair weather cumulus field developing as solar heating increases. Main forecast challenge in the near term is with temperatures as significant heating has taken place across much of the region behind the departing low. Temps from the city north and west have warmed well into the 80s, with some upper 80s in the Lower Hudson Valley. Highs for the day east of the city may occur late this afternoon, in the lower and middle 80s. It will remain muggy with dew points in the upper 60s and lower 70s. MRMS Regional radar mosaic shows some isolated showers developing across New England and Upstate New York. Some of these may advance into the interior this evening before loss of daytime heating. With dry air aloft, do not think these will be anything more than isolated and brief with no thunder mentioned. Weak ridging builds aloft tonight. Scattered clouds are likely to continue with some lingering low level moisture indicated on BUFKIT soundings. Dry and muggy conditions forecast with the potential for patchy fog towards daybreak across E LI and SE CT. && .SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/...
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Weak ridging flattens aloft on Saturday as a broad shortwave trough approaches from the midwest/Ohio Valley. The weak surface high will move off the New England coast in the afternoon with low pressure across the Ohio Valley associated with the shortwave trough. Instability is not impressive on Saturday, with the highest CAPE confined to western portions of the area. As has been the case with the last several systems, the models are struggling with the placement of precipitation and convection. However, there appears to be good agreement that the best coverage will be west of the Hudson River. The high resolution 4-km NAM and SBU-WRF also agree with this idea and have lowest PoPs across Long Island and SE CT increasing to high chance from the city north and west. Steering flow is weak so will need to keep an eye on any slow moving showers and isolated thunderstorms for locally heavy rainfall as PWATS approach 2 inches. Instability diminishes overnight, but lift may improve across the interior so will show likely POPs here tapering to chance across the far east end. The 12z GFS may be overdone with its depiction of widespread precipitation for the whole area overnight and have elected to follow a blend of the NAM and ECMWF as well as the Stony Brook WRF.
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&& .LONG TERM /SUNDAY THROUGH FRIDAY/... A frontal boundary will remain in the vicinity of the tri-state area Sunday through Monday. A few weak waves of low pressure develop along the boundry and move near the region. Will continue to keep chance pops in through this period. An upper trough approaches Monday and moves through Monday night with additional scattered showers and thunderstorms. Drier weather builds into the area Tuesday through Friday. A few isolated showers will be possible on Tuesday right behind the upper trough. Temperatures remain at or slightly below normal Sunday through Tuesday. Then, an increase in heat and humidity start to return. && .AVIATION /03Z SATURDAY THROUGH WEDNESDAY/... High pressure briefly builds tonight into the first half of Saturday. Then low pressure slowly approaches from the Ohio Valley. Mainly VFR conditions are expected overnight with increasing mid clouds. Patchy fog development, generally for terminals away from New York metro, is possible overnight. Low probability for VSBY reductions to MVFR or lower in BR. Showers are possible Saturday afternoon, especially west of NYC. Light winds overnight into Saturday morning. Winds become S/SE in the afternoon at 5 to 10 KT. .OUTLOOK FOR 00Z SATURDAY NIGHT THROUGH WEDNESDAY... .Saturday night into Sunday...Chance of showers and possibly a tstm. MVFR or lower conditions possible. .Sunday night-Monday night...Chance of showers. MVFR conditions possible. .Tuesday-Wednesday...Mainly VFR, although isolated showers possible. && .MARINE... Winds on the ocean have been diminishing as low pressure moves further offshore. However, a few gusts around 25 kt are possible east of Moriches inlet through the rest of the afternoon. Winds diminish tonight as high pressure builds across the waters. This high will move off the New England coast Saturday afternoon as low pressure slowly approaches from the Ohio Valley through Saturday night. Winds and seas are expected to remain below SCA levels during this time period. A fairly light pressure gradient will continue on the area waters resulting in conditions remaining below small craft conditions Sunday through Thursday. && .HYDROLOGY... The next chance for organized rainfall Saturday into Sunday. Less than an inch is expected with the highest amounts north and west of New York City. Locally higher amounts are possible in any heavier showers. Minor urban flooding would be the main hydrologic impact in any heavier shower/isolated thunderstorm. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...None. && $$ SYNOPSIS...BC/DS NEAR TERM...JP SHORT TERM...DS LONG TERM...BC AVIATION...PW MARINE...BC/DS HYDROLOGY...BC/DS is the U.S. government's official web portal to all federal, state and local government web resources and services.