Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 140716 AFDOKX Area Forecast Discussion National Weather Service New York NY 316 AM EDT Mon Aug 14 2017 .SYNOPSIS...
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High pressure drifts across the region today. A cold front approaches from the north Tuesday before dissipating Tuesday night. High pressure builds into the region Wednesday and slides offshore Wednesday night. A slow moving frontal system impacts the region Thursday through Saturday. High pressure then builds back in for Sunday.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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High based low clouds around 4-5k ft and cirrus can be expected today. Although no rain is fcst with a lack of forcing and deep moisture, the humidity will begin to increase by late in the day as return flow over the departing high kicks in. Water temps on the ocean are in the low to mid 70s, so it will not take much to get dewpoints to around 70, particularly along the s coasts, the next few days. A blend of the guidance, which was in good agreement, was used for high temps. Seas are down to 3-4 ft at the buoys, so the rip current risk has been kept in the moderate category.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/...
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Water vapor showed some convective initiation invof sern AR this mrng, which is where the weak wave which is progged to cross the area tngt supposedly originates. Because of this, a few shwrs were added to the fcst for tngt, keeping in line with the ECMWF, NAM and SREF solns. MU CAPE is only a few hundreds so tstms were not included attm. Otherwise, despite an increase in cloud cover, the increasingly moist lvls could allow for some patchy fog development, especially along the coasts under an advection fog scenario. Fog banks were noted over Nantucket and the nearby Atlantic this mrng. Humid on Tue with a chance for isold aftn tstms. Ern LI and sern CT are usually too stable for storms on sly llvl flow, so these areas have been kept dry for now. It remains to be seen if the faster GFS or slower ECMWF will verify for timing. The slower timing of the ECMWF may be why the model is fairly dry despite the dpva coming thru, as it misses peak heating. Temps thru the period a blend of the guidance and raw model data due to the increasing llvl moisture.
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&& .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
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Cold front dissipates over the region Tuesday night. An isolated thunderstorm NW of the city early on, otherwise dry weather. High pressure builds in from the NW during Wednesday with rising heights. Sided with the warmer guidance considering an offshore flow into the afternoon hours and 850mb temps of 15-16C. Highs in the upper 80s to lower 90s. A frontal boundary will be to our south Wednesday night before pushing north towards us as a warm front. Models are in pretty good agreement that we can get through at least Thursday morning without any showers. Increasing moisture and lift with the approach of the front then bring chances of showers Thursday afternoon before chances increase further Thursday night as the warm front passes through. There may be just enough elevated instability Thursday night for an isolated thunderstorm as well. A wave of low pressure approaches on Friday and Friday night for additional chances of showers and storms. Its associated cold front then maintains chances into Saturday. High pressure behind the front returns drier conditions for Sunday. High temperatures for Thursday through Sunday will be close to normal.
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&& .AVIATION /07Z MONDAY THROUGH FRIDAY/... VFR as high pressure builds in through this morning, and then passes east Monday afternoon and evening. Expect light winds through most of the morning, VRB in or N-NE direction. Winds should become SSE at or just under 10 kt late morning into the afternoon, with KLGA taking longest to shift from an ENE fetch off Long Island Sound by about 17Z. May have to watch KGON and KISP for possible development of low clouds and/or fog with IFR conditions after 00Z. .OUTLOOK FOR 06Z TUESDAY THROUGH FRIDAY... .Late Monday Night...Low clouds/fog with IFR/LIFR conds possible at KGON/KISP. Otherwise, BKN VFR cigs with possible sprinkles. .Tuesday and Tuesday night...Any early morning low clouds and fog out east should burn off by 12Z, followed by mainly VFR conds. Can`t rule out an isold shower or tstm from NYC metro NW in the afternoon and early evening. .Wednesday and Wednesday night...VFR. .Thursday...MVFR conds possible from NYC metro west, with chance of showers. .Thursday night and Friday...MVFR or lower flight cat possible, with chance of showers and tstms. Best chance for tstms in the afternoon. && .MARINE...
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Winds and seas will mainly remain blw sca lvls thru Sat. The exception will be during Tuesday night and Wednesday when seas may be around 5 feet on the ocean waters as a system moving well southeast of the forecast waters generates an east to southeast swell.
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&& .HYDROLOGY... No hydrologic impacts are expected through Sunday. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...None. && $$ SYNOPSIS...JMC/JC NEAR TERM...JMC SHORT TERM...JMC LONG TERM...JC AVIATION...Goodman MARINE...JMC/JC HYDROLOGY...JMC/JC

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