Area Forecast Discussion
Issued by NWS Upton, NY

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406 FXUS61 KOKX 221957 AFDOKX Area Forecast Discussion National Weather Service New York NY 357 PM EDT Mon May 22 2017 .SYNOPSIS...
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A weak cold front passes through the region tonight with a portion of the front stalling in the mid Atlantic region. 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.
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&& .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
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A weak frontal system was west of the region with a cold front moving through central upstate New York and through central Pennsylvania. The warm front was rather weak with the cold front forecast to reach the front, possible occluding. Much of the lift for the ongoing precipitation was provided by a weak mid and low level short wave moving to the east of the long wave upper trough. A 30 to 40 knot low level jet was providing additional lift with areas of moderate to briefly heavy rainfall across central New Jersey and then across Long Island. Thunder not expected as little to no CAPE and instability is present. The front pushes east and south toward the beginning of the Tuesday period with a portion the front stalling to the south. Little clearing expected and will be gradual.
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&& .SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/...
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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.
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&& .LONG TERM /WEDNESDAY THROUGH MONDAY/...
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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.
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&& .AVIATION /20Z MONDAY THROUGH SATURDAY/...
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A weak frontal system will move across the area the next 24 hours. While visibilities will fluctuate...ceilings will remain IFR into early this evening and then remain IFR through most of tonight. Frontal passage is expected between 07-09z and winds will shift north to northeast shortly thereafter. After the wind shift, conditions should dry somewhat but there is uncertainty with how quickly improvement will occur as some the latest model guidance suggests a slower improvement in the early morning. By midday...VFR is expected everywhere. SE winds 5-10 kt gradually increase, generally 8 to 13 kt. Occasional gusts up 15-18 kt possible. Winds shift north to northeast 5-10 kt around 07-09z and continue Friday. 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 21Z TUESDAY THROUGH SATURDAY... .TUESDAY...Becoming VFR in the morning. .WEDNESDAY...VFR. .THURSDAY...Possible IFR conditions in rain. Slight chance of thunderstorms Thursday evening. .FRIDAY...MVFR or lower possible in showers. .SATURDAY...VFR.
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&& .MARINE...
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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.
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&& .HYDROLOGY...
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Rainfall accumulations this evening through tonight will range from just over a tenth of an inch across the lower Hudson Valley to around 1/2 inch across Long Island and southern Connecticut. Locally higher amounts are possible across Long Island. Hydrologic impacts are not expected. Unsettled weather is expected mid to late week, but no hydrologic impacts are anticipated at this time.
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&& .TIDES/COASTAL FLOODING...
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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.
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&& .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...None. && $$ SYNOPSIS...JC/MET NEAR TERM...MET SHORT TERM...MET LONG TERM...JC AVIATION...IRD MARINE...JC/MET HYDROLOGY...JC/MET TIDES/COASTAL FLOODING...JC

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