Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 180817 AFDOKX Area Forecast Discussion National Weather Service New York NY 417 AM EDT Tue Sep 18 2018 .SYNOPSIS...
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The remnants of Florence will pass through the region today. High pressure builds in from the west on Wednesday, then ridges down from the Canadian Maritime Provinces Wednesday night and Thursday, then retreats to the northeast Thursday night. A cold front approaches from the west on Friday, then crosses the area Friday night, followed by high pressure building in for the weekend into early next week.
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&& .NEAR TERM /THROUGH TONIGHT/...
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Steady or rising temps over the last few hours as a tropical airmass builds in. Band of shwrs and tstms across sern PA into NJ have not been modeled well, but based on radar timing these should be into the cwa by 6 am, if not sooner. Additional pcpn developing e of the line should reach NYC shortly thereafter. The heaviest cells were producing estimated rates of up to an inch per hour based on KDIX radar, although they look a bit weaker attm. Nevertheless, there looks to be some hvy rain impacts during the mrng commute, especially w and n of NYC. Instability is increasing per laps, and will continue to do so until the sfc trof/cold front passes this aftn. The position of the main low, tracking roughly along the Mass Pike, will keep the best directional shear n of the area. As a result, svr tstms/tors have not been included in the fcst attm, although the mesoscale environment will continue to be monitored thru the day. The 03z SREF was used for pops. The bulk of the rainfall comes during the day, with the pcpn winding down aft 18z from nw to se...ending aft 00z ern edge of the cwa. Sly flow this mrng with the lljet should produce the strongest gust potential thru 15-17z. The sfc trof coming thru then lightens wind as it progresses thru the cwa. Light wind fields behind the front with winds up to h85 maxing out at 20kt. A blend of the mos was used for temps today and tngt.
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&& .SHORT TERM /WEDNESDAY/...
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High pres builds across Quebec with a drier airmass building in. Pwats fall to an inch or less. There is hint of a weak backdoor frontal passage, which could spark an isold shower. The fcst was left dry for now as the convergent region of the jet arrives. However, if the modeling becomes more consistent a few shwrs or sprinkles may need to be added. The NBM was used for temps.
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&& .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
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The core of a deep layered ridge builds to our southwest then south Wednesday night through Thursday night, with its axis sliding offshore on Friday. Subsidence under the ridge should keep things dry Wednesday night- Thursday night and relatively cloud free Wednesday night and Thursday. Week low level warm advection should bring some cloud cover on Thursday night. Lows Wednesday night should be a few degrees above normal. Highs on Thursday should be a few degrees below normal and lows Thursday night around 5 degrees above normal. A 700 hPa shortwave working its way up the back side of the ridge on Friday warrants slight chance pops for showers/thunderstorms to the northern Tier of the Lower Hudson Valley/W Passaic County/far N Fairfield County, with dry conditions expected elsewhere. Highs on Friday should be around 5 degrees above normal. A northern stream trough passes to the north Friday night, with mainly zonal flow over the region, the bulk of the energy associated with this trough will stay north of the area. As a result only have slight chance pops Friday night. The region remains under zonal-wsw flow aloft Saturday-Monday. The ECMWF is along in suggesting shortwaves embedded in the flow could bring some showers on Sunday and possibly Sunday night. So have slight chance pops Sunday/Sunday night and have gone the remainder of the time frame from Saturday-Monday. Temperatures should be above normal Friday night, then near normal Saturday, with below normal temperatures forecast Sunday and Monday.
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&& .AVIATION /08Z TUESDAY THROUGH SATURDAY/... Weak high pressure will remain offshore overnight as the remnants of Florence track west of the terminals, and interact with a frontal boundary that moves across the region this aftn and evening. Conditions will be gradually lowering to MVFR from W to E through the remainder of the night. Scattered showers will become more widespread towards daybreak, and there is also a chance of thunder, although the area entering SE PA that bears watching, may just clip NYC terminals around 11-12z. Will include VCTS for KEWR/KTEB for now and watch trends over the next few hours. Local IFR conditions will be possible late tonight into early Tuesday morning. Then the terminals are expected to remain generally MVFR with showers and isolated thunderstorms until fropa, 21-00Z. Best chance for tstms will be with the front this aftn, generally 16z-23z NW to SE, 17-22z or so in NYC. VFR returns thereafter, except there could be patchy MVFR/IFR fog development outside of NYC this eve. S winds 10-15 kt into mid morning at coastal terminals, 5-10 kt elsewhere. Ocnl gusts around 20 kt are possible through 12z at coastal terminals, then should diminish. Winds shift to the southwest this morning and aftn, then NW-N after the frontal passage this aftn/eve. .OUTLOOK FOR 06Z WEDNESDAY THROUGH SATURDAY... .Tonight...Patchy MVFR/IFR fog possible outside NYC, otherwise VFR. .Wednesday ...VFR. N winds G15-20KT. .Thursday...VFR. .Friday...Chance of showers with MVFR conditions at times. .Saturday...Mainly VFR. && .MARINE...
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Winds and seas build to sca lvls on the ocean today, and just blw on the remaining waters. A few 25 kt gusts cannot be ruled out especially on the s shore bays. The sca was extended thru tngt on the ocean as seas stay in the 3-5 ft range, and may need to be extended thru Wed as the ne flow builds seas once again. Winds blw sca lvls elsewhere. The waters around Long Island should experience a light to moderate pressure gradient from Wednesday night-Saturday night, with winds around 15 kt or less. Gusts to around 20 kt are possible on the coastal ocean waters Wednesday night. Seas on the coastal ocean waters could be around 5 ft, especially over the southern 1/2 of each zone Wednesday night and Thursday. Otherwise, sub-Small Craft Advisory conditions are expected from Wednesday night through Saturday night.
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&& .HYDROLOGY...
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1-2 inches of rainfall today with locally higher amounts possible. Rainfall rates of an inch per hour or greater can be expected at times, especially this aftn as the main frontal sys comes thru. Some minor flooding can be expected, with an isold flash flood threat where the heaviest activity develops. No significant hydrologic impacts are expected from Wednesday night through Monday.
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&& .EQUIPMENT... NYC NOAA Weather Radio Station KWO-35 (162.55 MHz) remains off the air for an extended period of time. && .OKX WATCHES/WARNINGS/ADVISORIES...
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CT...None. NY...High Rip Current Risk from 8 AM EDT this morning through this evening for NYZ075-080-081-178-179. NJ...None. MARINE...Small Craft Advisory until 6 AM EDT Wednesday for ANZ350-353- 355.
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&& $$ SYNOPSIS...JMC/Maloit NEAR TERM...JMC SHORT TERM...JMC LONG TERM...Maloit AVIATION... MARINE...JMC/Maloit HYDROLOGY...JMC/Maloit EQUIPMENT...

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