Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 210138 AFDOKX Area Forecast Discussion National Weather Service New York NY 938 PM EDT Sun Aug 20 2017 .SYNOPSIS... High pressure building into the region through Monday morning will settle to the south and east Monday afternoon, allowing a weak warm front to approach Monday night. After a hot and humid Tuesday, a cold frontal passage on Wednesday will produce a drastic cool down for the end of the week. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
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No changes made to the forecast tonight. Daytime cumulus have diminished. Weak ridging aloft with high pressure building in will lead to mostly clear skies for the rest of the night. This along with diminishing winds should allow temps to drop to the 50s and 60s in most areas, with only NYC remaining above 70 overnight.
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&& .SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/... Sky cover could be tricky in spots for the partial solar eclipse, which should run from about 120 PM to 400 PM in NYC and peak at 244 PM. Do expect some sct high clouds and also some sct Cu, possibly a narrow band of broken Cu with the sea breeze closer to the north shore of Long Island and in southern CT. South facing coastlines may be better viewing locations as any lower clouds that form inland with the sea breeze. Temps should rise quickly into early afternoon, and per 15Z run of the HRRRX which has been modified to incorporate impact on incoming solar radiation due to the eclipse, may actually drop a couple of degrees between 2-4 PM, then rebound. Overall temps should still reach the mid/upper 80s, possibly 90 in parts of urban NE NJ. The approaching warm front could spark an isolated shower or tstm toward sunset well west of NYC, with slight chances overspreading nearly all the area later Mon night. Lows should be in the upper 60s/lower 70s, and it will become muggy as dewpoints also increase into that range. There is a moderate risk of rip currents at Atlantic beaches on Monday. && .LONG TERM /TUESDAY THROUGH SUNDAY/... A cold front will reach the area on Wednesday per the 12Z suite of model guidance, which was in good agreement. This means that Tue is setting up to be hot and humid. Winds progged around 200 degrees will pump lots of humidity into the area, and across the ern half of the CWA keep actual temps slightly suppressed despite H85 warming towards 20C. The humidity will compensate for any lack of heat, with just about all areas likely aoa 90 for a heat index. Across the normally hottest areas like NJ zones, the heat index attm looks to reach about 100. There could be a few aftn and eve tstms, particularly N and W of NYC, but there will at least be an increase in dense cirrus from upstream convective debris. As a result the fcst goes mostly cloudy by Tue eve. Shwrs and tstms ahead of the front Tue ngt and Wed, then the area dries out for the remainder of the fcst period. The cold front will be driven by a 100-kt H3 jet, so tstms will be easier to sustain or initiate at ngt. If the timing ends up slightly slower, a svr outbreak is possible on Wed as CAPE could soar to 3000 J/kg or more. Even with the progged faster timing however, there could still be svr at any time ahead of the front with the jet acting on MUCAPE around 1500-2000 J/kg. Much cooler weather will then settle in for Thu-Sun, with temps averaging blw climo. && .AVIATION /02Z MONDAY THROUGH FRIDAY/...
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VFR through the TAF period as high pressure remains in control through Monday. NW winds will diminish this evening to around 5 kt at city terminals and become light and variable elsewhere. Winds will increase late Monday morning into the afternoon out of the SW and back towards the south at coastal terminals. Sea breeze enhancement may allow for gusts in the upper teens at KJFK and KISP in the afternoon. .OUTLOOK FOR 00Z TUESDAY THROUGH FRIDAY... .Monday night...Mainly VFR, with low chance MVFR or lower at mainly Long Island terminals. .Tuesday-Wednesday...A chance of showers and thunderstorms with brief periods of MVFR or lower possible. SW winds G15-20KT Tuesday afternoon. .Wednesday Night-Friday...VFR.
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&& .MARINE...
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High pressure over the waters will lead to sub-SCA conditions through Monday night. A few gusts up to 20 kt are possible on the waters west of Fire Island Inlet in the afternoon due to sea breeze enhancement. Winds and seas will ramp up on Tue, with SCA conditions developing on all waters. Winds will decrease after a cold frontal passage, bringing winds the protected waters blw SCA lvls by Wed eve. On the ocean, seas should linger around 5 ft into Wed ngt. Winds and seas are then progged to remain, in the absence of any increased swell, blw SCA lvls thru the weekend.
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&& .HYDROLOGY...
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No widespread hydrologic impacts are forecast through the week.
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&& .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...None. && $$ SYNOPSIS...JMC/Goodman NEAR TERM...Goodman/DS SHORT TERM...Goodman LONG TERM...JMC AVIATION...DS MARINE...JMC/Goodman HYDROLOGY...JMC/Goodman

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