Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 151206 AFDOKX Area Forecast Discussion National Weather Service New York NY 706 AM EST Mon Jan 15 2018 .SYNOPSIS... A high pressure ridge along the East Coast will slowly weaken through tonight. Weak low pressure will then approach from the west on Tuesday, and pass to the north Tuesday night as another low develops off the mid Atlantic coast. This low will deepen and track east of New England on Wednesday. High pressure will then build to the south through Friday, moving into the western Atlantic next weekend. Low pressure will approach from the west on Sunday. && .NEAR TERM /THROUGH TONIGHT/...
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Stratocu deck continues to expand westward into the area, with most places becoming mostly cloudy this morning. A few stray flurries were noted by our upper air crew, and obs across Rhode Island show flurries as well, so added sct coverage to all of southern CT and eastern Long Island for the morning. Later on there could be a brief late day window where skies clear briefly except across eastern Long Island/CT, where an upper level jet streak and low level positive theta-e advection should maintain clouds, and may even produce some light freezing drizzle (moisture confined to low levels warmer than -8C as opposed to this morning`s colder environment) or spotty flurries across SE CT and eastern Long Island this evening. Clouds could briefly break again overnight mainly across southern CT and Long Island before lowering and thickening again ahead of the weak low approaching from the west. High temps today should range from 25-30, warmest toward the metro areas and the coast. Lows tonight expected to be 20-25 in NYC metro and along the immediate coast, with teens elsewhere.
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&& .SHORT TERM /TUESDAY/... The approaching weak low and associated positively-tilted upper trough/deep layer SW flow aloft will approach on Tue, with chances for light snow increasing through the day, especially NW of NYC, where an inch or two of accumulation may be possible by evening. Farther east, low level WAA and light precip intensity at best may not allow temps to cool down as much toward wet bulb temps, so afternoon precip across parts of Long Island more likely to be be a rain/snow mix. High temps should range from the upper 20s well inland, to 30-35 most elsewhere, to some upper 30s in parts of eastern Long Island. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... Guidance consensus is now rather strong for Tuesday night into Wednesday night for an upper full latitude trough to moves across the eastern United States and into the western Atlantic as the upper flow has become more progressive. The northern stream energy and surface low will be weakening across upstate New York Tuesday night into Wednesday. An inverted trough off the southeast coast Tuesday night develops into a coastal low by 12Z Wednesday off the DELMARVA as the upper trough approaches. Again guidance is well clustered in deepening the low Wednesday, and passing over or near the 70/40 benchmark. Light precipitation, snow, with the weakening low initially moves into the region Tuesday night. Then the coastal low dominates Wednesday into Wednesday night. Low level warm air wraps into the far eastern sections, mainly New London Connecticut to the twin forks of Long Island, ahead of the low late Tuesday night into Wednesday. The ECMWF wraps the warmer air the furtherest west, with the GFS and NAM just across the far eastern zones. Leaned toward this colder solution as the low will be progressive. As such there will likely be a rain/snow mix, and even a change to all rain for a time Wednesday, before colder air returns as the low departs after 21Z Wednesday. Looks to be an advisory level snow event across portions of northeastern New Jersey through the lower Hudson Valley and across southern Connecticut, while coastal locations will be in the 2 inch range. Too early at this time to post an advisory, and also some uncertainty, if the coastal low tracks farther east with the progressive flow, then snow amounts will be lower. Upper flow become zonal Wednesday night into the upcoming weekend. There is a rather weak shortwave that quickly move through the area Friday, however, likely moves through dry with little moisture in place at that time. Surface high pressure builds to the south and moves into the western Atlantic late Sunday into Monday as the next frontal system approaches. && .AVIATION /12Z MONDAY THROUGH FRIDAY/...
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high pressure north of the region gradually weakens today as low pressure passes well offshore and a clipper approaches from the Great Lakes. Area of stratus (3kft) east of NYC will continue to advance towards the NYC terminals due to an easterly low level flow. These low clouds are expected to impact the terminals, although timing and duration remains difficult. There is a chance that any MVFR cigs only last a few hours before improving to VFR. Will need to follow trends and the forecast may need to adjusted in subsequent TAFs. Ceilings do fall to MVFR late tonight and Tuesday morning as low pressure approaches from the west. There is a chance of some light snow developing late in the 30 hour TAFs. Have covered this with a prob30. Winds remain from the NE through 06Z Tue. Speeds generally 5 to less than 15kt with occasional gusts to 20 kt possible during the daytime hours Monday. Winds become light and variable after 06z. NY Metro Enhanced Aviation Weather Support... Detailed information, including hourly TAF wind component forecasts, can be found at: http:/ KJFK TAF Comments: Amendments may be needed for the timing of any MVFR cigs. The afternoon KJFK haze potential forecast is YELLOW...which implies slant range visibility 4-6SM outside of cloud. KLGA TAF Comments: Amendments may be needed for the timing of any MVFR cigs. The afternoon KLGA haze potential forecast is YELLOW...which implies slant range visibility 4-6SM outside of cloud. KEWR TAF Comments: Amendments may be needed for the timing of any MVFR cigs. 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 the timing of any MVFR cigs. KHPN TAF Comments: Amendments may be needed for changing flight categories. KISP TAF Comments: Amendments may be needed for changing flight categories. .OUTLOOK FOR 12Z TUESDAY THROUGH FRIDAY... .Tue-Wed night...MVFR or lower in light snow. N-NW winds G15-20KT Wed-Wed night. .Thu-Fri...VFR. NW winds G15-25KT Thu into Thu evening.
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&& .MARINE... SCA conditions should continue on the ocean waters into tonight, with gusts 25-30 kt today and seas building as high has 7 ft out east. Ocean seas will be at marginal SCA levels Tue into Tue night night with a light southerly flow, and likely continue into Wednesday as low pressure develops off the mid Atlantic coast. This low deepens as passes east of the waters during Wednesday. A strong and gusty northwest flow develops Wednesday and continues into Thursday night. Small craft wind gusts and marginal seas will be likely on the ocean waters Wednesday night into Thursday night with a chance of small craft gusts across eastern Long Island Sound and the eastern Long Island bays. Friday and Friday night winds and seas will be below SCA levels as high pressure builds to the south and a weaker pressure gradient is across the forecast waters. && .HYDROLOGY... No significant hydrologic impacts are expected. && .EQUIPMENT... NYC NOAA Weather Radio Station KWO-35 (162.55 MHz) is off the air for an extended period of time. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...Small Craft Advisory until 6 AM EST Tuesday for ANZ350-353-355. && $$ SYNOPSIS...Goodman/MET NEAR TERM...Goodman SHORT TERM...Goodman LONG TERM...MET AVIATION...BC MARINE...Goodman/MET HYDROLOGY...Goodman/MET EQUIPMENT... is the U.S. government's official web portal to all federal, state and local government web resources and services.