Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 272214 AFDOKX Area Forecast Discussion National Weather Service New York NY 614 PM EDT Tue Sep 27 2016 .SYNOPSIS... A weakening cold front will remain offshore through Wednesday night while high pressure builds in from the Canadian Maritimes. A nearly stationary low pressure system over the Ohio Valley and Mid Atlantic regions, with an associated warm front remaining to our south due to strong high pressure over New England and the Canadian maritimes, will then bring an extended period of unsettled weather from Wednesday night into the weekend. The low will weaken and move slowly northeast early next week. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... The cold front further weakens as it remains southeast of Long Island. Winds at the surface will be light out of a general southwest direction. The forecast is generally on track with dry conditions still anticipated. Clouds are thinning out from NW to SE going into the afternoon as drier air works in with the more westerly flow. The dry conditions will continue into tonight. Starting aloft with tonight, there will be some ridging taking place across the region. This will allow for subsidence and help decrease clouds for the evening. The local region will actually be inbetween a large cutoff upper level low in the Ohio Valley and an elongating upper level trough in the Canadian Maritimes as it becomes more of an open wave. Clouds increase late from east to west. At the surface, the front will further weaken and move farther offshore as high pressure builds into the Canadian Maritimes. Mainly dry conditions should prevail but there could be a few showers southeast of Long Island tonight, closer to the lingering frontal boundary. Lows tonight were taken from the ECS guidance which was relatively warmer and exhibited less spatial range between temperatures. There remains a moderate risk of rip current development at the ocean beaches into the early evening. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/... The weather continues to become more unsettled during this timeframe. For Wednesday through Wednesday Night, the region will remain between a southward shifting large cutoff upper level low going towards the Tennessee Valley and the upper level shortwave in the Canadian Maritimes. There will be continued ridging between the two upper level features. However, at the surface, the center of high pressure remains strong and centered more towards Southeast Canada. There will be a low pressure area well southwest of the region that will be approaching. There is evident too from the model MSLP fields an inverted trough that will be approaching ahead of the surface low. Aloft, there will be increasing isentropic lift especially Wednesday afternoon through Wednesday night. This goes along with the SW flow in the mid to upper levels setting up warm air advection aloft. At the surface, a persistent pattern with high pressure in Southeast Canada and the local region being on the SW periphery of this high. This will give the region increasing NE flow and with the high being strong centered in the Canadian Maritimes, a steep pressure gradient will setup, resulting in winds becoming gusty. Model precipitation fields are showing some very light precipitation amounts across the region Wednesday and increasing towards the western portions of the region Wednesday night. This all conveys here a situation with moisture getting trapped under an inversion. This low level moisture will increase Wednesday and eventually materialize as drizzle or light rain to start with and a higher chance of rain Wednesday night when it will increase in intensity, coverage, and become more steady. At that time, the atmospheric column becomes more moist as well. Regarding temperatures Wednesday, used the ECS guidance and slightly adjusted downward. NE flow and increasing clouds points to a cooler than normal day on average out east while farther west highs are forecast to be near normal. Wednesday night features lows from a MAV/MET blend with again not much of a spatial range, mostly mid 50s to near 60 across the area. && .LONG TERM /THURSDAY THROUGH TUESDAY/... NWP guidance is in remarkably good agreement on the big picture through the weekend, with a large upper low completely cutting off from the westerlies and stalling over the Ohio Valley from Thu through Sat, then lifting across the Great Lakes on Sunday and weakening into an upper trough that slides across the Northeast on Monday. Meanwhile, as a strong upper high builds over the Western Atlantic, upper level confluence to its north where it meets the westerlies will maintain strong surface high pressure over northern New England and the Canadian Maritimes,that should nose down into our area and keep a warm front to our south. This combination will keep us in an unsettled weather pattern through at least the weekend, with periods of moderate to heavy rain. The first of these is likely to come Thu night into Fri morning via strengthening easterly low level Atlantic inflow, moistening mid levels via deep southerly flow aloft, a mid level vort max riding up the coast, and increasingly difluent flow aloft. Another bout of heavy rain may come to Long Island and southern CT on Saturday as another mid level impulse rides up the coast and as a weak wave of low pressure forms along the front just to the south. In between these bouts of heavier rain skies should remain overcast, with periods of intermittent light rain. An exception to this may take place Thu afternoon, when some guidance indicates the high may build down strongly enough from the north to shut off precip for a time across the interior. Some elevated instability will be present Sat into Sat night, with some rumbles of thunder possible. As the upper low lifts into the Great Lakes on Sunday, an associated weak triple-point low and/or occluded front should slowly lift across, with precip becoming more showery in nature. The upper low will continue to weaken and move east, but not clear our area until Tue morning, so forecast carries at least slight chance PoP until then. High temps in this regime will be slightly below average Thu-Fri, with a return to near average Sat into Mon, and then slightly below average on Tue as Canadian high pressure starts to return. Low temps meanwhile should be mostly warmer than average until Mon night. && .AVIATION /22Z TUESDAY THROUGH SUNDAY/...
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Weak seabreeze front has pushed north of KJFK and looks to have enough momentum to reach at KEWR by 23Z. Winds will back around to 160-170. Less confident of it reaching KTEB and KLGA. At KBDR, a sound breeze was noted with an easterly flow which will allow for winds to vary from E-SE. Elsewhere, generally expecting a weak S-SW wind at 10 kt or less. Long stretch of unsettled weather begins Wednesday. VFR expected across all terminals for a good part of the night but pockets of MVFR can`t be ruled out after midnight, especially toward Wednesday morning. By early Wednesday afternoon, clouds lower and thicken with a chance of drizzle/light rain in MVFR and lower conditions, especially at coastal terminals. Light and variable wind this evening becoming NE around 10 kt early Wednesday morning. By midday, NE winds increase to near 15 kt and become gusty at times near 20-25 kt. ...NY Metro Enhanced Aviation Weather Support... Detailed information, including hourly TAF wind component forecasts, can be found at: http:/www.weather.gov/zny/n90 KJFK TAF Comments: Amendments possible to adjust wind direction and/or ceilings, especially Wednesday morning. KLGA TAF Comments: Possible early evening seabreeze. Amendments possible to adjust wind direction and/or ceilings, especially Wednesday morning. KEWR TAF Comments: Amendments possible to adjust wind direction and/or ceilings, especially Wednesday morning. KTEB TAF Comments: Possible early evening seabreeze. Amendments possible to adjust wind direction and/or ceilings, especially Wednesday morning. KHPN TAF Comments: Amendments possible to adjust wind direction and/or ceilings, especially Wednesday morning. KISP TAF Comments: Winds may vary to the SE early this evening. Amendments possible to adjust wind direction and/or ceilings, especially Wednesday morning. .Outlook for 18Z Wednesday through Saturday... .WED...Becoming MVFR late morning/early afternoon. NE winds G25KT possible in the afternoon. .THU-SAT...IFR/MVFR in showers. NE winds 15-20 kt with gusts 25-30 kt possible THU-FRI. .SUN...Mainly VFR but MVFR possible with a chance of showers. N winds 10-20 kt.
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&& .MARINE... Sub SCA initially but with a weak wind field, there will not be much to resist incoming swells from the south. Thinking there will be some higher seas eventually getting back into the ocean zones that may meet SCA criteria tonight with otherwise sub SCA conditions. There is potential here that SCA may need to start earlier and sometime tonight if the swells reach close enough to the ocean waters. Then Wednesday into Wednesday Night, SCA looks more probable across all waters especially on the ocean. There will be a tight pressure gradient setting up between a Southeast Canada high and low pressure southwest of the region. Think max gusts reach near 30 kt, mostly Wednesday night. Then as the pressure gradient tightens further, easterly gales appear likely from Thu into Fri morning mainly on the ocean, but perhaps also on the nearby bays of eastern Long Island and eastern Long Island Sound, with SCA conds on the harbor and western Sound. Issued gale watch for the ocean for Thu into Thu night. SCA conds are likely to continue thereafter on all waters into Fri, on the eastern Sound/bays into Fri night, and on the ocean into Sat. && .HYDROLOGY... Dry weather expected through tonight and any rain Wednesday through Wednesday night will be light with rainfall totals less than a quarter of an inch. The heaviest rainfall amounts with a nearby low pressure system should fall to our west, but there could still be some periods of heavier rain Thu night into Fri morning, also on Saturday. Total basin average rainfall from Thu through Sat should range from 3/4 to 1-3/4 inches, with potential for local amounts of 2-3 inches across parts of Long Island and southern CT. This is not expected to cause major hydrologic impacts. && .TIDES/COASTAL FLOODING... A persistent moderate easterly flow during mid to late week may combine with increasing astronomical high tides associated with the new moon on Friday to cause minor to locally moderate coastal flooding. The high tide cycles from Thu night into Fri morning appear to be of most concern. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...Small Craft Advisory from noon Wednesday to 6 AM EDT Thursday for ANZ330-335-338-340-345. Gale Watch from Thursday morning through late Thursday night for ANZ350-353-355. Small Craft Advisory from 10 AM Wednesday to 6 AM EDT Thursday for ANZ350-353-355. && $$ SYNOPSIS...Goodman/JM NEAR TERM...JM SHORT TERM...JM LONG TERM...Goodman AVIATION...IRD/DW MARINE...Goodman/JM HYDROLOGY...Goodman/JM TIDES/COASTAL FLOODING...

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