Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 281629 AFDOKX Area Forecast Discussion National Weather Service New York NY 1229 PM 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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An upper ridge axis moves through the region today with weak high pressure at the surface. The forecast is mostly on track. Only minor adjustments to temps/dewpoints/sky cover based on the latest trends. Still partly sunny with sun filtered through cirrus for most spots, but thicker cumulus and mostly cloudy for interior sections.
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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 /18Z SUNDAY THROUGH FRIDAY/... High pressure will remain fairly stationary to the east through tonight. A frontal system will begin to approach late tonight and cross the region on Tuesday. SE winds of 8-12 kt this afternoon...with gusts 15 to 20 possible. Gusts diminish this evening...but then E/SE winds increase for coastal terminals to 10 to 15 kt late tonight into Monday morning as a wave of low pressure tracks to the south. Gusts to 20 kt possible. Will have to watch along the coast for development of low clouds in the onshore flow tonight. Meanwhile deteriorating conds late tonight...with MVFR conds developing for the NYC metro terminals towards 06Z, with IFR conditions possible by daybreak Mon in developing rain. Potential for sparse tsra heading into morning push. .OUTLOOK FOR 12Z MONDAY THROUGH THURSDAY... .Monday...IFR conds likely. Rain likely and chance of tstms in the morning into early aft. -DZ possible in aft. E gusts to 20 kt along the coast in the morning...lighter NE winds in the afternoon. .Monday night...MVFR or lower conds possible .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. && .MARINE... The forecast appears to be on track. In the near term, will be watching the ocean waters and eastern Long Island Sound for development of any fog later today into this evening. Given a second night moist onshore low level flow, cannot rule out the possibility of fog later today into tonight. 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-advy conditions expected through Thu night. && .HYDROLOGY... 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... 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 continues for the south shore bays of Brooklyn, Queens, and Nassau, where widespread minor coastal flooding is 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. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...Coastal Flood Advisory from 10 PM this evening to 3 AM EDT Monday for NYZ075-178-179. NJ...None. MARINE...None. && $$ SYNOPSIS...24/Maloit NEAR TERM...JC/Maloit SHORT TERM...Maloit LONG TERM...24/Maloit AVIATION...Goodman/NV MARINE...Goodman/24 HYDROLOGY...24/Maloit TIDES/COASTAL FLOODING... is the U.S. government's official web portal to all federal, state and local government web resources and services.