Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 222349 AFDOKX Area Forecast Discussion National Weather Service New York NY 749 PM EDT Mon May 22 2017 .SYNOPSIS... A weak frontal system passes through the region tonight, stalling in the mid Atlantic region late tonight into Tuesday. Weak high pressure builds in for Tuesday. Meanwhile, a wave of low pressure will move along the frontal boundary, south of the region, Tuesday and Tuesday night. Weak high pressure builds in on Wednesday, followed by low pressure Thursday into Friday. High pressure returns for the beginning half of the upcoming holiday weekend, but low pressure may bring some unsettled weather during the latter half. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
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Weak frontal system is located across east central PA and upstate NY this evening. This boundary will continue moving east and then through the region overnight. Best lift, in the form of shortwave energy and 30-40 kt low level jet, is shifting east, with steadiest rain across Long Island and southern Connecticut. This activity is expected to continue sliding east through the next few hours, with PoPs decreasing as well. Attention then turns to a meso-low, currently moving off the DelMarva coast. High resolution mesoscale guidance takes the meso-low offshore, but then possibly link it up with the approaching front to enhance showers along it across eastern Long Island and southeast Connecticut. Will continue to forecast highest PoPs here, with a gradual decreasing trend into the early morning hours. Thunder not expected as little to no CAPE and instability is present. Mainly dry conditions expected from the city north and west after midnight. Areas of fog are possible this evening as well. Visibilities should not fall much below 2SM in any fog. Improving visibilities are anticipated from west to east as the frontal boundary moves across. Gradual clearing expected behind the front. Temperatures remain nearly steady for much of the night, but could fall into the upper 40s/lower 50s NW of the city towards daybreak.
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&& .SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/... The cold frontal boundary will remain stalled to the south, through the mid Atlantic region and DELMARVA Tuesday, and weak mid and low level ridging builds. Will keep the area dry through most of the day and then bring in probabilities late in the day to the south as a wave begins to move along the frontal boundary. The wave passes to the south with some differences in placement Tuesday and Tuesday night with the NAM just about totally dry while the GFS is a little farther north. At this time leaned a little more closer to the GFS and brought chance across about the south half of the area. The wave does pass through quickly and precipitation may be ended across the eastern zones by Wednesday morning. && .LONG TERM /WEDNESDAY THROUGH MONDAY/... Weak high pressure builds in behind a departing offshore low on Wednesday. Only a slight chance of a shower in the morning mainly over Long Island. Partly sunny otherwise, and a blend of MAV/NAM MOS looked good for high temperatures. The next system to bring rainfall to the area arrives late Wednesday night, with rainfall being most likely Thursday into Thursday night. Went a little cooler than most guidance, particularly over western zones as a triple point low approaches, but the associated warm front extending to its east might only push through some of the eastern zones, if at all. Some elevated instability should be present, so have included isolated TSTMs for Thurs and Thurs night. Also included areas of fog for late Weds night into Thurs morning with the warm front not too far off to the south. For Friday, the storm exits to the NE, but is still close enough for a chance of showers, especially over the NE zones. Some lower level instability combined with a cold pool aloft may also result in a TSTM over parts of CT as well. Weak high pressure then returns for Saturday. Will go with a dry forecast and slightly above normal temperatures for now. The timing of the next low pressure system is still uncertain at this point. Some overrunning rainfall could move in by daybreak Sunday. The system would figure to move slowly enough for Monday to be affected as well. Will go with CHC PoP for now for both days. && .AVIATION /00Z TUESDAY THROUGH SATURDAY/...
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A front will cross the area tonight, as a series of weak lows track south of Long Island into Tuesday evening. IFR/LIFR conditions should continue through at least 6z, and probably last until after the front passes (4-9z from W to E). It appears conditions should improve fairly rapidly behind the front, so expect most areas to be VFR by around 12z. Light and variable winds shift to the N-NE at 10KT behind the front. An afternoon seabreeze is probable at all but KSWF/KHPN/KTEB - where winds should be mainly light and variable all day Tuesday. Occasional gusts to 15-20kt are possible Tuesday 12-16z Tuesday. 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: Amendments possible due to changes in ceilings and visibilities. KLGA TAF Comments: Amendments possible due to changes in ceilings and visibilities. KEWR TAF Comments: Amendments possible due to changes in ceilings and visibilities. KTEB TAF Comments: Amendments possible due to changes in ceilings and visibilities. KHPN TAF Comments: Amendments possible due to changes in ceilings and visibilities. KISP TAF Comments: Amendments possible due to changes in ceilings and visibilities. .OUTLOOK FOR 00Z WEDNESDAY THROUGH SATURDAY... .Tuesday night-Wednesday evening...VFR. NE winds G15-20KT possible Wednesday. .Wednesday night-Friday night...MVFR or lower possible. Slight chance of thunderstorms Thursday evening. LLWS possible Thursday-Thursday evening. NW winds G15-20KT possible Friday. .Saturday...VFR.
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&& .MARINE... A southeast flow continues this evening and into tonight ahead of an approaching cold front. Winds then shift to the northwest to north with the frontal passage, and then shift to the northeast to east Tuesday into Tuesday night as a wave of low pressure passes to the south of the forecast waters. Winds and seas are expected to remain below small craft levels tonight through Tuesday night. A weak pressure gradient will be over the waters on Wednesday with weak high pressure ridging in behind a departing offshore low. NE winds at 10 KT or less shift SE in the afternoon, and seas should remain below 5 FT. The next storm system so far would not appear to create a pressure gradient strong enough for advisory level winds over the region. Relatively stronger winds associated with this system would be on Friday when the center of this system is northeast of the waters. Winds are therefore forecast to remain below advisory levels through this period and should remain that way on Saturday as winds diminish. However on the ocean, guidance suggests a significant swell. Have gone with a forecast of wave heights below guidance, but still at advisory criteria Wednesday night through Saturday morning. && .HYDROLOGY... Hydrologic impacts are not expected with rainfall through tonight. Additional amounts of one quarter to one half inch possible across eastern Long Island and southern Connecticut. Unsettled weather is expected mid to late week, but no hydrologic impacts are anticipated at this time. && .TIDES/COASTAL FLOODING... Minor coastal flooding thresholds may be reached with Wednesday night`s high tide cycle for southern sections of NY Harbor, the south shore back bays of western LI/Queens/Brooklyn, and western Long Island. A better chance of minor flooding arrives for Thursday night, with northern NY Harbor and parts of central LI sound also included. Chances then lower on Friday night as winds likely shift offshore. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...None. && $$ SYNOPSIS...JC/MET NEAR TERM...DS/MET SHORT TERM...MET LONG TERM...JC AVIATION...Maloit MARINE...JC/MET HYDROLOGY...DS/JC TIDES/COASTAL FLOODING...

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