Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 250758 AFDOKX Area Forecast Discussion National Weather Service New York NY 358 AM EDT WED MAY 25 2016 .SYNOPSIS... High pressure builds to the south, then southeast, through tonight followed by a weak cold front crossing the area on Thursday. This front then lifts north as a warm front Thursday night, with high pressure building in behind the front through Saturday night. A series of frontal boundaries then impact the area from Sunday into Tuesday. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... A SPS has been issued for patchy fog, locally dense at times, for Suffolk County and S CT through 7am. There is some potential a short fused dense fog advisory might be needed, especially across S CT. Also monitoring fog potential over the lower Hudson Valley early this morning. Otherwise, deep layered ridging builds in today, with associated subsidence keeping cloud cover relatively at bay, once any morning fog burns off, other than some passing cirrus in the afternoon. It appears the subsidence should also be strong enough to keep any convection at bay this afternoon over the County Warning Area (CWA), so have gone with a dry forecast. For highs today, a blend of mixing down from 825-775 hPa, per BUFKIT soundings, NAM 2-meter temperatures, and a mixture of MAV/ECS/MET guidance was used. Highs should be around 15 degrees above normal. It would not be surprising if a location of two in NE NJ, the Lower Hudson Valley and maybe even normally warmer locations in NYC reached the 90 degree mark. The afternoon seabreeze should prevent any record highs from being reached. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/... Deep layered ridging remains in control tonight and Thursday. It will be dry tonight, with only some high clouds around. However, a 700-500 hPa shortwaves passes over the top of the ridge, and through the area Thursday afternoon. This, coupled with surface based CAPE of 5000-1000 J/kg, Showalter Indices from -2 to 2, and 20-25kt of Bulk shear over roughly the NW 2/5 of the CWA, warrants slight chance to chance pops in that region. It should be noted that the ECMWF suggests that there should be sufficient subsidence under the ridge to keep things dry throughout the area on Thursday. The GFS however suggests fairly extensive convection over roughly the NW 2/5 of the CWA, with the NAM somewhat in between (though closer to the ECMWF than the GFS). Noting, that in addition to the passing shortwave, will also have a cold front sinking south into the region. Based on this, it appears there is enough forcing to warrant pops at this time. However, there is still the potential for no precipitation at all on Thursday. For lows tonight, a blend of MAV/MET/ECS guidance and NAM 2-meter temperatures was used, with values around 10-15 degrees above normal. A blend of MAV/ECS/MET guidance, NAM 2-meter temperatures and a mix down from 850-750 hPa, per BUFKIT soundings, was used for highs on Thursday. Highs should be around 15 degrees above normal, but probably a degree or so lower than today. If the more extensive convection suggested by the GFS plays out, highs, especially over western areas, might need to be lowered by at least 5 degrees. && .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/... Frontal boundary lifts north of the area as a warm front Thursday night. A southerly flow and ridging aloft will allow for the above normal temperatures to continue Friday and Saturday. It will also mean a noticeable increase in humidity as inland areas will see dewpoints into the lower to middle 60s by Friday afternoon, mainly away from the coast. The relatively cool ocean waters will keep temperatures and dewpoints down along coastal areas. However, temperatures across central Nassau and Suffolk may reach the upper 70s to near 80 on both Friday and Saturday. The warm front then approaches our area again late Saturday night into Sunday morning as a back door cold front. High pressure behind this cold front over southeastern Canada slips off the New England coast and into the western Atlantic during this time period. This high is weaker than in previous model runs, and thus will not push as far into our area as previously forecast. This will help to keep the frontal boundary in the vicinity through Monday morning. Sunday`s temperature may be a difficult one depending on which side of the front we will be on. We will be warm sectored on Monday. However, clouds and will keep temperatures down. A cold front then approaches for Tuesday. Something to watch is the disturbance well off the Southeast coast. Models show this disturbance moving inland over the Southeast coast and having little, if any, impact for our area through the forecast period. However, moisture from this system could make its way into our area on Tuesday, but right now it looks like a low chance of that happening. It is still a few days out with a good deal of uncertainty in the forecast. As far as rainfall, nothing looks organized for the long term. There is a fair amount of moisture available given the humid airmass and surface based CAPE values are high for the afternoons from Friday through Monday, but lift does not look overly impressive. Afternoon showers and thunderstorms are possible for areas north and west of NYC Friday and Saturday. Then there is at least a slight chance for the entire area on Sunday with the approach of the back door cold front, which will remain in the vicinity through Monday. Continued unsettled for Tuesday with the approach of the cold front from the west. None of these days are expected to be a washout, just passing showers and thunderstorms. && .AVIATION /07Z WEDNESDAY THROUGH SUNDAY/... High pressure builds in today. VFR, except reduced vsbys in BR/FG at Hudson Valley and CT terminals through 12z. Light/calm winds pre-dawn bcmg West 5 to 10 kt in the morning, increasing 9-14 kt in the afternoon and backing slightly, more so at the coastal terminals. Gusts 15-19 kt. .OUTLOOK FOR 06Z Thursday through Sunday... .Wednesday night through Thursday...VFR. .Thursday night through Friday morning...Mainly VFR but sub-VFR possible in showers/evening thunderstorms. .Friday-Saturday...MVFR possible in afternoon/evening tstms. .Sunday...Mainly VFR, but sub-VFR in showers possible NW of NYC. && .MARINE... A Marine Weather Statement has been issued for locally dense fog, mainly nearshore, for Long Island Sound and the bays of Long Island through 7am. Outside of afternoon seabreezes bring gusts to around 20 kt to the New York Bight Region Today and Thursday, a light to moderate pressure gradient over the area will keep winds to 15 kt or less through Sunday. With no significant swell forecast, these relatively light winds will keep seas below Small Craft Advisory criteria as well throughout the forecast period. && .HYDROLOGY... Dry through Thursday morning. Scattered to Isolated Showers and Thunderstorms, mainly from NYC on N/W Thursday afternoon/evening could bring less than 1/2 inch of rain to that area. There are no significant hydrologic impacts expected from Thursday Night into early next week. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...None. && $$ SYNOPSIS...Maloit/JP NEAR TERM...Maloit SHORT TERM...Maloit LONG TERM...JP AVIATION...JC MARINE...Maloit/JP HYDROLOGY...Maloit/JP is the U.S. government's official web portal to all federal, state and local government web resources and services.