Area Forecast Discussion
Issued by NWS Upton, NY

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995 FXUS61 KOKX 241555 AFDOKX Area Forecast Discussion National Weather Service New York NY 1155 AM EDT Mon Jul 24 2017 .SYNOPSIS... 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. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Back edge of showers was moving across eastern portions of the Lower Hudson Valley and NYC metro, which will push across LI and CT the next few hours. SPS issued for brief heavy downpours, reduced visibilities, and ponding on area roadways over the next couple of hours. Frontal wave just south of central LI will pass to the east by mid afternoon with the low-level flow backing to a more northerly direction. This will result in some unseasonably cool air for this time of year. Readings were currently in the upper 50s across interior CT, to a warm as around 70 on LI. In fact, with cloud cover in place, readings will likely drop the next few hours, especially for LI and NYC. Readings elsewhere should remain nearly steady. The one uncertainty in the forecast today is to the extent the low clouds erode across NE NJ, NYC, and the Lower Hudson Valley. Should we see some sun, instability will increase during the afternoon hours with the potential for scattered convection ahead of an upper level disturbance. Temperatures would also be warmer in these spots. Right now, the forecast is maintaining cloudy conditions based on latest satellite trends. Hi Res models also maintain a low level inversion and clouds at the base of the inversion this afternoon. There is a high risk for the development of rip currents at ocean beaches today. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/... 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. Other than an isolated shower, dry conditions return on Tuesday as high pressure builds over the area. High temperatures will be in the low to mid 70s. && .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 /16Z MONDAY THROUGH FRIDAY/... A frontal boundary will remain south of the area through Tuesday. Showers with widespread MVFR/local IFR conditions will continue until around 16Z-17Z NYC metro/Lower Hudson Valley, and until 18Z-20Z east. After showers end, MVFR cigs should linger much of the day, though think there will be enough drying aloft to allow for a period of VFR conditions late today into early this evening mainly for the NYC metro terminals. E-NE winds gusting over 20 kt will continue through the day at KBDR/KGON. Farther west, winds should slowly diminish and back N-NE this afternoon. With the front remaining just south and a lighter NE flow continuing, MVFR conditions should return to all terminals tonight. There is a chance that cigs could lower to IFR late tonight especially at KISP/KGON. NY Metro Enhanced Aviation Weather Support... Detailed information, including hourly TAF wind component fcsts, can be found at http:/www.weather.gov/zny/n90 KJFK TAF Comments: Unscheduled AMD likely to fine tune changes in flight category. The KJFK afternoon haze potential forecast is RED, which implies slant range visibility less than 4SM outside of cloud. KLGA TAF Comments: Unscheduled AMD likely to fine tune changes in flight category. The LGA afternoon haze potential forecast is RED, which implies slant range visibility less than 4SM outside of cloud. KEWR TAF Comments: Unscheduled AMD likely to fine tune changes in flight category. The KEWR afternoon haze potential forecast is RED, which implies slant range visibility less than 4SM outside of cloud. KTEB TAF Comments: Unscheduled AMD likely to fine tune changes in flight category. KHPN TAF Comments: Unscheduled AMD likely to fine tune changes in flight category. KISP TAF Comments: Unscheduled AMD likely to fine tune changes in flight category. .OUTLOOK FOR 12Z TUESDAY THROUGH THURSDAY... .Tuesday...MVFR in the morning, then 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. && .MARINE... 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 remain in effect for most waters this morning, except NY Harbor and south shore bays of LI. Winds gradually 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. && .HYDROLOGY... Localized quarter to half inch of rainfall amounts are possible as the back edge of the rain moves across the area through early this afternoon. Scattered convection is also possible later this afternoon, but do not foresee hydrologic impacts. Additional rainfall is possible Thursday through Friday night. Hydrologic impacts are not expected at this time. && .TIDES/COASTAL FLOODING... With the new moon that occurred early yesterday morning and the current easterly flow, 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. Minor coastal flooding has ended across the south shore back bays of western LI this morning. A statement though remains in effect for western LI Sound this afternoon as water levels will approach minor benchmarks. For tonight, coastal flood advisories may be needed, but will wait on another run of guidance to determine potential headlines for this subsequent high tide cycle. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...High Rip Current Risk until 9 PM EDT this evening for NYZ075- 080-081-178-179. NJ...None. 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. && $$ SYNOPSIS...Fig/DW NEAR TERM...DW SHORT TERM...Fig LONG TERM...PW AVIATION...Goodman/JM MARINE...DW/PW HYDROLOGY...Fig/DW TIDES/COASTAL FLOODING...DW

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