Area Forecast Discussion
Issued by NWS Upton, NY

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979 FXUS61 KOKX 251426 AFDOKX Area Forecast Discussion National Weather Service New York NY 1026 AM EDT Thu May 25 2017 .SYNOPSIS... Low pressure will deepen over the Mid-Atlantic today, track through the Tri-State Region tonight and into the Maritimes on Friday. A broad area of high pressures builds in for the first half of the weekend, then a slow moving frontal system will bring the potential for showers from Sunday into Tuesday. && .NEAR TERM /THROUGH FRIDAY/...
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Overall rainfall this morning not too impressive with the local area split between two heavier batches of rain, one off to the NW and one offshore. Rain intensity is expected to remain on the light side for the remainder of the morning with just a few pockets of moderate rain. Much of this rain is due to isentropic lift/warm advection. No thunder is expected with this activity. Middle level drying from the south will serve to cut off widespread rain this afternoon. Have adjusted PoPs and Wx grids to account for this trend, and included mention of a chance of light rain or drizzle as the lowest 5,000 feet remain saturated. Areas of fog are also possible this afternoon. Easterly winds will be highest this morning with gusts as high as 25-30 mph, strongest near the coast. Winds will gradually weaken this afternoon as the pressure gradient slackens. Attention then turns to the H5 low, which moves over tonight. Initially middle levels look to dry to support anything more than light rain or drizzle, but then significant dpva and lapse rates from h85 to h4 range avg around 6.5C/km. The models all produce convective pcpn. As a result, showers and embedded thunderstorms are expected overnight. The upper low reaches the Gulf of ME on Fri. This will allow for decreasing coverage and intensity of showers through the day. The downslope flow could allow for clearing, especially along the coast, by the end of the day. Temps will be below normal today, then will nudge closer on Fri as the rain ends. A blend of the guidance and raw model data was used.
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&& .SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY NIGHT/... Weak ridging builds in Fri ngt and Sat which will attempt to produce fair weather. There is a suggestion of shrtwv energy swinging thru on Sat. If this materializes, isold-sct shwrs will be possible. A rainy day however is not expected attm. A broad upr lvl low then drops into the Midwest, producing sw flow aloft across the fcst area Sun. This will produce an increasing chance for shwrs, particularly Sun aftn thru Sun ngt. Temps will remain close to or blw normal thru the period. The Superblend was used. && .LONG TERM /MONDAY THROUGH WEDNESDAY/... The upr low over the Midwest will drive a slow moving frontal sys thru the region for the beginning of the week. There is some uncertainty wrt the timing, with the ECMWF slightly faster than the GFS. Chance POPs remain in the fcst. Weak ridging builds in Tuesday, followed by more shortwaves rotating around the S Canada closed low, which has slid a bit farther E into Hudson bay/NW Ontario), Tuesday night and Wednesday - with maybe some more isolated- scattered showers. Temperatures should be within a few degrees of either side of normal Sunday-Monday night, then run above normal Tuesday- Wednesday. && .AVIATION /14Z THURSDAY THROUGH MONDAY/...
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An area of low pressure will move across the region through the TAF period. IFR/LIFR conds developing this morning in band of light to moderate rain...and expected to continue into this evening. Steady rain moves north between 18-20z...with areas of drizzle/light rain in its wake this afternoon. Potential for LIFR visibilities this evening in fog. Moderate potential for an area of showers and thunderstorms to move through the region between 02z and 08z. Heavy downpours are the main threat. Easterly winds 10-20kt with gusts to 25kt this morning...weakening late this afternoon into tonight. Northwest flow develops Friday morning. NY Metro Enhanced Aviation Weather Support... Detailed information, including hourly TAF wind component forecasts, can be found at: http:/www.weather.gov/zny/n90 KJFK TAF Comments: Isolated gusts to 30 kt this morning. IFR/LIFR Vsby this afternoon will be conditional on coverage of drizzle. KLGA TAF Comments: Isolated gusts to 30 kt this morning. IFR/LIFR Vsby this afternoon will be conditional on coverage of drizzle. KEWR TAF Comments: Amendments may be needed for changing flight categories. IFR/LIFR Vsby this afternoon will be conditional on coverage of drizzle. The afternoon KEWR haze potential forecast is YELLOW...which implies slant range visibility 4-6SM outside of cloud. KTEB TAF Comments: Amendments may be needed for changing flight categories. IFR/LIFR Vsby this afternoon will be conditional on coverage of drizzle. KHPN TAF Comments: Amendments may be needed for changing flight categories. IFR/LIFR Vsby this afternoon will be conditional on coverage of drizzle. KISP TAF Comments: Isolated gusts to 30 kt this morning. IFR/LIFR Vsby this afternoon will be conditional on coverage of drizzle. .OUTLOOK FOR 12Z FRIDAY THROUGH MONDAY... .Friday...MVFR/IFR possible. Chance of showers. .Saturday...VFR. .Sunday-Monday...MVFR/IFR possible in showers.
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&& .MARINE...
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E winds will increase today with SCA criteria across all the waters. Low pressure will track over the area tonight, so winds will lighten below SCA levels. Seas on the ocean however will remain in the 5-10 ft range thru Fri. The SCA has therefore been extended for these areas. Winds and seas currently look to remain below SCA levels for entire Memorial Day Weekend.
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&& .HYDROLOGY...
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0.75-1.5 inches of rain is forecast through Fri. Locally higher amounts possible where thunderstorms occur tonight. Minor urban and poor drainage flooding is possible. Hydrologic impacts are otherwise not expected Sat-Tue.
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&& .TIDES/COASTAL FLOODING...
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A Coastal Flood Warning has been issued for south shore back bay locations of Nassau County for tonight, otherwise advisories are in place for areas adjacent to western Long Island Sound, NY Harbor, and the south shore back bays of the western Long Island. While astronomical tides are lower this morning, a strengthening easterly flow will bring the potential for localized brief minor flooding for those areas under either a warning or advisory later tonight. A statement is in effect for this morning. The primary threat for minor to moderate coastal flooding will be during the high tide cycle tonight. How quickly easterly winds begin to weaken this afternoon/evening will be key to the potential for seeing widespread versus localized moderate coastal flooding along the southern bays of NYC and Western LI. The best chance for widespread moderate coastal flooding at this time appears to be across the south shore back bays of Nassau County, where a warning is in effect. Along Western LI Sound, NY/NJ Harbor including Manhattan, and the southern bays of Suffolk County, widespread minor coastal flooding is likely with less than 1/2 ft of surge needed in many places to reach minor flood thresholds. Minor flood thresholds could briefly be touched along the eastern bays of LI and SE CT. The potential for dune erosion looks to be low and localized. Minor coastal flooding is likely during the nighttime high tides for the southern bays of Western LI through the memorial day weekend. While along western Long Island Sound, lower NY Harbor, and the southern bays of NYC minor coastal flooding it is a possible at those times.
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&& .OKX WATCHES/WARNINGS/ADVISORIES... CT...Coastal Flood Advisory from 10 PM this evening to 1 AM EDT Friday for CTZ009-010. NY...Coastal Flood Advisory from 7 PM to 10 PM EDT this evening for NYZ074-075-178. Coastal Flood Advisory from 10 PM this evening to 1 AM EDT Friday for NYZ071-073-078-176-177. Coastal Flood Advisory from 8 PM this evening to midnight EDT tonight for NYZ080. Coastal Flood Advisory from 7 PM this evening to 1 AM EDT Friday for NYZ072. Coastal Flood Warning from 7 PM to 11 PM EDT this evening for NYZ179. NJ...Coastal Flood Advisory from 7 PM to 10 PM EDT this evening for NJZ006-106-108. MARINE...Small Craft Advisory until 6 PM EDT this evening for ANZ330- 335-338-340-345. Small Craft Advisory until 6 PM EDT Friday for ANZ350-353-355. && $$ SYNOPSIS...JMC NEAR TERM...JMC/DS/DW SHORT TERM...JMC LONG TERM...JMC/Maloit AVIATION...BC/NV MARINE...JMC HYDROLOGY...JMC TIDES/COASTAL FLOODING...

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