Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 240747 AFDOKX Area Forecast Discussion National Weather Service New York NY 347 AM EDT Mon Jul 24 2017 .SYNOPSIS...
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A frontal boundary will remain south of the area through Tuesday. High pressure builds over the northeast late Tuesday through Wednesday, then drifts off the coast Wednesday night. Another wave of low pressure follows for Thursday into Saturday. High pressure returns Sunday.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Showers and thunderstorms will spread across the region this morning as a weak area of low pressure moves northeast across the area. The steadier rain should taper off to showers this afternoon and into tonight. High temperatures today will be in the mid to upper 70s. There is a high risk for the development of rip currents at ocean beaches today.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/...
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Showers continue through late tonight as an upper level trough remains over the area. Low temperatures tonight will be in the low to mid 60s along the coast and in the upper 50s inland. Dry conditions return on Tuesday as high pressure builds over the area. High temperatures will be in the low to mid 70s.
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&& .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... The extended forecast mainly remains consistent with the previous forecast with the exception that precipitation is expected remain into Saturday as was hinted at by the ECMWF late Saturday, as an upper trough is slower to move east. The northern stream flow along the US/Canadian border remains nearly zonal and progressive with embedded shortwaves moving through the flow. One shortwave will be exiting the northeastern coast, along with the accompanying surface low, Tuesday. CAPE and instability remain limited so will continue with showers. A weak ridge axis builds into southern Canada from the southern ridge over the southwest and moving into the plain states mid week. Another shortwave was coming onshore of the Canadian Pacific coast as seem on the upper level water vapor loop. And these system has been picked up by the models. This shortwave open and tracks quickly across southern Canada then digs and large trough along the eastern United States late in the week into the weekend as a western north Atlantic ridge builds and blocks the eastern trough. This will keep waves of low pressure tracking along a frontal boundary Thursday into Saturday before the last one exits later Saturday. So now have chances of precipitation through Friday into Saturday. The upper trough weakens Sunday as surface high pressure builds to the north resulting in a dry Sunday. Temperatures through the extended period will be near seasonal normals, except for being below normal Tuesday. && .AVIATION /08Z MONDAY THROUGH FRIDAY/...
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Low pressure will move along a front to the south overnight, then pass over or just south of NYC metro and Long Island today. Widespread MVFR cigs are already in place NW of NYC metro, with some patches of lower clouds farther east. Moderate to locally heavy showers and a few tstms extending from SE PA into nearby NJ/DE will weaken and move NE toward the NYC metro terminals, arriving 08Z-09Z and bringing widespread MVFR/local IFR conditions there until about 11Z. Additional activity over NE/Central PA should then move E and impact mainly the Lower Hudson Valley and CT terminals from about 12Z-16Z, with IFR conditions expected at KBDR/KGON. After these showers exit east, MVFR cigs should linger at the NYC metro terminals until about 19Z, and at KISP until about 22Z. MVFR conditions should linger north of there through the rest of the 06Z TAF period. E flow should gradually increase this morning, with gusts around 20 kt at the NYC metros, and higher out east especially at KBDR/KGON where gusts over 25 kt likely. Winds should back N and then NW after this low passes, then become NE again tonight. .OUTLOOK FOR 00Z TUESDAY THROUGH THURSDAY... .Late tonight...MVFR conds likely, IFR possible, with chance of showers. Diminishing NE winds. .Tuesday...Becoming VFR. NE winds 10-15 kt. .Tuesday night...Patchy fog with MVFR vsby possible late at KSWF, otherwise VFR. .Wednesday and Wednesday night...VFR. .Thursday...Chance of showers and possibly a tstm with MVFR or lower conds NW of the NYC metros in the afternoon, otherwise VFR. .Thursday night and Friday...MVFR or lower conditions possible, with chance of showers/tstms.
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&& .MARINE...
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Gusty winds ahead of a wave of low pressure riding along a front can be expected this morning. By afternoon, the low and front track across the ocean waters, just south of Long Island. This wave of low pressure moves east tonight, with another low along the front passing to the south. High pressure then builds to the north of the waters Tuesday and Wednesday. SCA has been posted for most waters this morning, except NY Harbor and south shore bays of LI. Winds diminish this afternoon. Across the eastern waters, a few gusts in excess of 30 kt are possible early. Ocean seas remain rather rough today, and tonight. Will extend the SCA for the ocean waters through tonight for now, but it likely will need to extend into Tuesday as well. The easterly flow continues into Wednesday and then gradually diminishes and becomes southeasterly as high pressure moves well east of the forecast waters. Ocean seas are expected to subside below 5 feet by mid week. Then winds and seas remain below small craft levels Wednesday night into Friday.
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&& .HYDROLOGY...
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Heavy rainfall possible this morning for the entire area. Generally, 1 to 1.5 inches is forecast, with locally higher amounts possible in any thunderstorms. Ponding of water on roadways would occur with the heavier rainfall along with some minor flooding of poor drainage and low lying areas possible. A Flash Flood Watch has been issued for portions of the area. Additional rainfall is possible Thursday through Friday night. Hydrologic impacts are not expected at this time.
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&& .TIDES/COASTAL FLOODING...
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With the new moon that occurred early yesterday morning, tides are running astronomically high. Tidal departures of 1 1/2 to 2 ft are needed for minor flooding during daytime high tide. Only 1/2 to 1 ft departures are needed at night. With easterly winds, will issue a coastal flood statement for the south shore back bays of Nassau, Queens and Kings, and across the western LI Sound as tides approach minor benchmarks. Elsewhere, feel tides remain below minor benchmarks. For tonight, coastal flood advisories may ne needed, but will wait on another run of guidance to determine potential headlines for this subsequent high tide cycle.
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&& .OKX WATCHES/WARNINGS/ADVISORIES...
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CT...None. NY...Flash Flood Watch until 11 AM EDT this morning for NYZ067-069- 071>075-078-080-176>179. High Rip Current Risk through this evening for NYZ075-080-081- 178-179. NJ...Flash Flood Watch until 11 AM EDT this morning for NJZ002-004- 006-103>108. MARINE...Small Craft Advisory until 6 PM EDT this evening for ANZ330- 340. Small Craft Advisory until 2 PM EDT this afternoon for ANZ335. Small Craft Advisory until 6 AM EDT Tuesday for ANZ350-353-355.
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&& $$

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