Area Forecast Discussion
Issued by NWS Buffalo, NY

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000 FXUS61 KBUF 291508 AFDBUF Area Forecast Discussion National Weather Service Buffalo NY 1108 AM EDT WED JUN 29 2016 .SYNOPSIS... High pressure centered over Lake Michigan will promote fair weather across western New York today. A mid level trough will continue mostly cloudy skies and scattered showers east of Lake Ontario. High pressure will bring dry weather for all on Thursday before the next cold front brings a chance of rain showers on Friday. The upcoming fourth of July weekend will feature plenty of sunshine with a day to day warming trend. && .NEAR TERM /THROUGH TONIGHT/... Considerable cloudiness continues across much of western and north- central NY late this morning. Moist cyclonic flow within a mid-level trough is responsible for this cloudiness and the isolated to scattered showers over eastern Lake Ontario and central NY. Diurnally driven instability will also support some isolated afternoon non-severe thunderstorms. Drier air across Ontario province will gradually work its way across western NY through this afternoon which will promote clearing from west to east. The increasing amount of sun will take the edge off an otherwise cool airmass...as H85 temps in the vcnty of 10c will only support afternoon highs in the low to mid 70s. Tonight...high pressure centered over Lake Michigan will gradually build across the Lower Great Lakes. The relatively fresh dry airmass will lead to good radiational cooling tonight under starlit skies...allowing temperatures to fall well below normal. Temperatures by daybreak will range from the mid 40s across a good chunk of the Srn Tier to the upper 50s along the immediate lake shores. && .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... Surface high pressure will build into the lower Great Lakes on Thursday and provide subsidence and dry air to support nearly full sunshine outside of a few flat diurnal cumulus inland from the lakes. The airmass will modify with 850mb temps returning to around +10C, which will bring highs into the lower 80s at lower elevations with deep mixing. The strong differential heating and weak synoptic scale flow will allow local lake breeze circulations to develop by afternoon, with cooler temperatures within a few miles of the lakes. Thursday night the surface high will drift to the east coast and allow southerly return flow to develop across the lower Great Lakes. A plume of low level moisture will move northward through PA and into portions of the eastern Finger Lakes and central NY late Thursday night, but any scattered showers should remain east of our area. Otherwise expect mainly clear skies across the bulk of the area. Lows will range from the upper 50s on the lake plains to the lower 50s in a few of the cooler Southern Tier valleys. On Friday a rather sharp mid level trough will move east across Ontario and Quebec. The stronger forcing for ascent associated with DPVA and height falls ahead of the trough will remain well north of the Canadian border. Farther south, the tail end of the trough will enter western NY by mid to late morning, then move to the eastern Lake Ontario region by afternoon. A period of modest DPVA ahead of this trough combined with low level convergence along a pre-frontal trough will produce a few scattered showers and thunderstorms, first across western NY by mid to late morning and then central NY and the North Country by early afternoon. The pre-frontal trough will likely arrive too early in the day for stable lake shadows to be established yet, so the risk for a shower or thunderstorm will be areawide. The actual cold front will not arrive until late in the day, but the bulk of the moisture and convergence appear to be tied to the pre- frontal trough. The cold front may interact with local lake breeze boundaries to produce a few more widely scattered showers and thunderstorms during the afternoon and evening. By this time stable lake shadows will be established in the southwest flow regime, so expect the Buffalo and Watertown areas to avoid most of the afternoon and evening deep moist convection. The passage of the pre-frontal trough relatively early in the day will interfere with the destabilization of the atmosphere, with only modest instability values of less than 1000J/kg in most model guidance. The limited instability and lack of stronger forcing and convergence late in the day will keep the severe weather risk very low. Any widely scattered showers and storms will end from west to east Friday evening with the passage of the cold front. Drying and subsidence will bring clearing skies in most areas overnight, with some lingering cloud cover across the North Country. && .LONG TERM /SATURDAY THROUGH TUESDAY/... High pressure will build into the western Great Lakes and Ohio Valley on Saturday, while a deep trough swings through Quebec. The pressure gradient between the two will produce a moderate breeze across the area, especially east and southeast of Lake Ontario where winds may gust to around 30 mph. Ascent and somewhat deeper moisture rotating through the base of the Quebec trough may produce a few scattered showers and increased cloud cover across the North Country Saturday afternoon and evening. Otherwise expect the rest of the area to remain dry. A brief push of cooler air will enter the region with highs in the mid 70s at lower elevations and around 70 across higher terrain. High pressure will build into the lower Great Lakes Sunday and Monday with abundant sunshine. Temperatures will warm to around 80 for highs on Sunday, then into the lower or even mid 80s for Monday on Independence Day. By Tuesday both the GFS and ECMWF suggest the start of building heat as a much warmer airmass upstream over the midwest states begins to make headway building into the lower Great Lakes. This will push highs into the upper 80s at lower elevations inland from the lakes. Looking a little farther ahead, a strong ridge building over the central US will make enough headway eastward to allow very warm temperatures to reach our region for the second half of next week. Zonal flow will remain just north of the Canadian border, with a building ridge just to our south. This may allow for an active corridor of ridge riding thunderstorm complexes passing through the Great Lakes for several days late next week. && .AVIATION /15Z WEDNESDAY THROUGH SUNDAY/... A slow moving mid level trough will gradually push east across the Adirondacks today while sfc high pressure will approach from Lake Michigan. MVFR cigs continue at KROC and KJHW at 15z but should lift to VFR levels by midday...with most of the TAF sites over the western counties totally losing their CIGS by 18z. For sites east of Lake Ontario though...cloud cover will be slower to clear with scattered showers or even a isolated afternoon thunderstorm. VFR conditions with light winds are anticipated tonight as high pressure will build across the Lower Great Lakes. Outlook... Thursday...VFR. Friday...VFR/MVFR. A chance of showers or thunderstorms. Saturday and Sunday...VFR. && .MARINE... High pressure over Lake Michigan will gradually build across the Ohio Valley and Lower Great Lakes later today into Thursday. This will keep a weak sfc pressure gradient in place over Lakes Erie and Ontario with relatively light winds and negligible waves remaining intact. The favorable conditions for recreational boating will deteriorate somewhat on Friday...as a cold front will cross the region. This will support scattered thunderstorm activity...and in the wake of the front...freshening winds on Lake Erie. Moderate to fresh winds can be expected throughout the Lower Great Lakes Friday night and Saturday ahead of the next high pressure system. Lower winds and waves are anticipated for Sunday into the fourth of July. && .BUF WATCHES/WARNINGS/ADVISORIES... NY...None. MARINE...None. && $$ SYNOPSIS...RSH/SMITH NEAR TERM...RSH/SMITH SHORT TERM...HITCHCOCK LONG TERM...HITCHCOCK AVIATION...RSH/SMITH MARINE...RSH/SMITH

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