Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 281037 AFDOKX Area Forecast Discussion National Weather Service New York NY 637 AM EDT Sun May 28 2017 .SYNOPSIS... High pressure gradually retreats to the northeast as a series of weak lows track to the south of Long Island through Tuesday. A weak cold front approaches from the west Tuesday night, then crosses the area Wednesday. High pressure then builds in to the south and southwest through Thursday night. A cold front approaches on Friday then slowly crosses the area Friday night and Saturday. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Made minor changes this update to reflect the latest trends in observations and guidance. The forecast appears on track. A deep layered northern stream ridge builds over the area today. However, with abundant low level moisture being trapped under the associated subsidence inversion, should see more clouds than sun over the area. This coupled with onshore flow, should result in temperatures being towards the cooler end of guidance. This is consistent with a blend of ECS/MET guidance, NAM and ECMWF 2-meter temperatures and a mix down from 975-925 hPa per BUFKIT soundings. Highs should be around 5-10 degrees below normal.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/... The northern stream ridging slides offshore tonight, delaying the onset of light rain (in response to increasing isentropic lift) until mainly after midnight. A northern stream shortwave pushes through the area Monday. Along with it are some fairly steep mid level lapse rates, reflected with showalters progged down to around -2 and possibly as low as -4. This should be sufficient to turn the character of the precipitation to more convective driven, so have gone with showers with embedded thunderstorms. Noting showalters of -2 to -4, cannot rule out some locally strong storms. With wetbulb zero heights of 8000-9000 ft, small hail is a possibility. There is also a very small chance of an isolated sever storm, with the main threat hail of 1+" in diameter. Precipitation should taper off from SW to NE this afternoon/early this evening as the shortwave trough lifts to the NE. Lows tonight should be near normal and highs Monday around 10 degrees below normal. && .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/... A closed low will slowly track from SW Ontario/N Great Lakes Monday night to pres over southern Ontario will slowly track to near the Quebec Ontario Boarder by Thursday morning. There will be shortwaves rotating around this rather broad closed low, that could trigger some isolated to scattered showers from time to time through Wednesday night, with the best chance over northern zones. The models then differ on how fast/far the closed low works to the east Thursday-Saturday, in part because they differ on how it is re-enforced from the west. As a result, the forecast from Thursday on is of at best low-moderate confidence in the details. For now it appears that Thursday and Thursday night should be dry, with the region potentially in between main spokes of the closed low. The next spoke then influences our weather Friday or Saturday, so have just slight chance pops for now until the timing of the system can be better refined. Temperatures start out near normal Monday night and Tuesday, should be above normal Wednesday, then near normal again Thursday-Saturday. && .AVIATION /09Z SUNDAY THROUGH THURSDAY/...
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High pressure will remain fairly stationary to the east through tonight. A frontal system will begin to approach late Sunday night. BKN-OVC higher-based clouds persist north and east of the NYC metro terminals. Meanwhile a narrow band of low stratus with IFR cigs has developed from central NJ into western Long Island and Westchester, including KJFK/KLGA/KHPN. This band not expected to expand much further, so KEWR/KTEB/KISP/KBDR should remain unaffected. Light flow should become SE 8-12 kt by afternoon, then diminish again tonight. Will have to watch along the coast for development of low clouds in the onshore flow tonight. Meanwhile some light rain with MVFR conds could reach the NYC metro terminals just before 06Z. .OUTLOOK FOR 06Z MONDAY THROUGH THURSDAY... .Late tonight...MVFR conds developing from west to east, with light rain especially from NYC metro on west. IFR conds possible along the coast. .Monday...Showers likely and chance of tstms. IFR conds possible. .Monday night...Still a chance of showers/tstms early from KBDR/KISP east with MVFR or lower conds, otherwise VFR. .Tuesday...Chance of showers and possibly a tstm with brief with MVFR or lower conds in the afternoon/evening. .Wednesday...Mainly VFR. Chance of showers/tstms mainly NW of the NYC metro terminals. .Thursday...VFR.
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&& .MARINE...
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Made minor changes this update to reflect the latest trends in observations and guidance. The forecast appears on track. In the near term, will be watching the ocean waters mainly west of Moriches Inlet for development of any fog before daybreak and lasting into the morning. So far nothing has developed, but given the moist onshore low level flow, cannot rule out the possibility. An SCA may be needed for the ocean waters late tonight into the daytime hours on Monday. Increasing SE flow looks to peak at 20G25kt Monday morning, with max seas per WaveWatch and buoy wind/wave climatology 5, maybe 6 ft, with the higher conditions and longer duration more likely to be out east during the daytime hours on Monday. Otherwise, sub-small craft advisory conditions are expected through Thu night.
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&& .HYDROLOGY... Dry today. Total rainfall amounts tonight and Monday could range from around 1/3 to 1/2 of an inch, with locally higher amounts possible in areas experiencing strong convection Monday. In areas that do experience strong convection, there is the potential for at least localized ponding of water on roadways. No significant widespread hydrologic impacts are then expected at this time from Monday night through at least Thursday night. && .TIDES/COASTAL FLOODING...
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While astronomical tides are a little lower for the high tide cycle tonight, surge will likely increase a bit with strengthening SE flow. As a result, a Coastal Flood Advisory is in effect for the south shore bays of Brooklyn, Queens, and Nassau, where widespread minor and locally moderate coastal flooding are expected. Elsewhere, brief/localized minor flooding is possible along the shores of Westchester/Fairfield western Long Island Sound, and along the Kill Van Kull and Arthur Kill around Staten Island and adjacent portions of NJ. Additional minor flooding may occur with the high tide cycle Monday night in the areas that have been affected over the last several days.
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&& .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...Coastal Flood Advisory from 10 PM this evening to 3 AM EDT Monday for NYZ179. NJ...None. MARINE...None. && $$ SYNOPSIS...Maloit NEAR TERM...Maloit SHORT TERM...Maloit LONG TERM...Maloit/24 AVIATION...Goodman MARINE...Goodman/24 HYDROLOGY...Maloit/24 TIDES/COASTAL FLOODING...

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