Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 260208 AFDOKX Area Forecast Discussion National Weather Service New York NY 1008 PM EDT WED MAY 25 2016 .SYNOPSIS... High pressure weakens and moves farther offshore through Thursday. Meanwhile a weak cold front moves in Thursday. This front will back north as a warm front Thursday Night. A Bermuda high will then dominate through the weekend, bringing summertime warmth as a series of weak upper level disturbances touch off convection each afternoon and early evening. A back door cold front will approach Sunday into Sunday night, then retreat back north early next week as a weak front slowly approaches from the west and a broad area of low pressure slowly approaches from the south. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
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Forecast is on track. Minor adjustments made to t/td and sky based on latest obs and trends. Otherwise...mainly clear skies to start however...high clouds will begin to spill over the upper ridge axis overnight. Used a blend of mav/met for lows with manual adjustments up near some coastal rural locations due to partial onshore flow.
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&& .SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/... For Thursday, some slight ridging takes place aloft with overall the ridge still exhibiting a rather flat structure. The models are pointing to a relatively stronger shortwave that will be riding along the top of the ridge, arriving into western portions of the region by Thursday Evening. At the surface, high pressure will shift farther offshore and weaken. A cold front moves across during the day and weakens as it does so. This will bring some extra clouds during the day. With the weak pressure gradient, sea breezes set up sooner with a more southerly component. This will keep coastal location temperatures a few degrees cooler compared to the previous day while interior locations will be nearly the same temperatures as the previous day. Weather will start out dry with enough subsidence of residual ridging and then with the approach of the shortwave as well as increasing instability, some showers and thunderstorms will be possible late in the day and evening. The subsidence will still be enough to prevent much in the way of any convection from developing. With the approach of the shortwave, places north and west of NYC will have a slight chance of showers and thunderstorms late in the day since those locations will be relatively closer to the shortwave. For Thursday Night, the shortwave moves across while at the surface, the weak cold front will move back north as a warm front. The presence of the frontal boundary and the increased positive vorticity advection aloft will allow for a relatively greater chance of showers. Convection with the lack of CAPE will be minimal with any coverage being isolated. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... Earlier forecast reasoning still holds, with summertime warmth through the weekend as longwave upper ridging moves across. A warm front will clear the entire area Fri morning, and with H8 temps near 16C and H5-10 thicknesses near 570 dm, high temps are likely to reach the lower 90s both Fri/Sat NW of NYC, with 80s elsewhere except for the south shore of eastern Long Island. There is a good chance for late day tstms from NYC north/west as a mid level disturbance interacts with a lee trough. Wind fields are not particularly strong aloft, but deep layer shear might still support a few strong to locally severe storms. Any late convection on Saturday will be isolated in nature and tied more to differential heating in/near the higher terrain. The northern stream disturbance moving across eastern Canada has trended faster, which means any associated back door cold front may not make it into the area at all, or only into eastern CT/Long Island. So Sunday will still be a warm day, though not quite as warm as the previous two days. Once again looking mainly at scattered late day convection tied either to the front or to a lee trough NW of NYC, and as another weak mid level vort max approaches from the west. Monday should be cooler, with more cloud cover as shortwave energy Atlantic moisture ride up the coast, well in advance of a low off the Southeast coast, and on the back side of the retreating offshore ridging. Once this passes, we should return to warm weather and chances for sct mainly inland late day convection as another upper ridge moves in from the west. && .AVIATION /02Z THURSDAY THROUGH MONDAY/...
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High pressure builds to the south overnight and Thursday. VFR forecast. Light west/southwest expected overnight. Light winds in the morning become south around 10 kt. Sea breezes are expected by afternoon, sooner across CT terminals. .OUTLOOK FOR 00Z Friday through Monday... .Thursday night through Friday morning...Mainly VFR but sub-VFR possible in showers/evening thunderstorms. .Friday through Friday night...Mainly VFR, but sub-VFR possible in isolated showers and evening thunderstorms. .Saturday...Mainly VFR. Isolated showers and thunderstorms north of NYC/Long Island. .Sunday...Sub-VFR possible in afternoon showers and thunderstorms. .Monday...Sub-VFR possible in showers and thunderstorms.
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&& .MARINE... With the pressure gradient overall remaining rather weak...the seas and wind gusts will stay below SCA criteria through Thursday Night. S-SW flow increasing to near 20 kt may bring a brief period of 5-ft seas to the western ocean waters late day Fri into Fri evening. Otherwise, expect quiet winds/waves outside of any potential thunderstorms. && .HYDROLOGY... No significant widespread precipitation expected through Thursday Night. Local minor flood impacts from heavier showers/tstms are possible with any late day convection, on Friday and Sunday, mainly NW of NYC. Heavy rain may also be possible on Monday with an upper level disturbance and Atlantic moisture riding up the coast, but timing and location are uncertain, and at this time looks likely to pass just offshore Long Island. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...None. && $$

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