Area Forecast Discussion
Issued by NWS Buffalo, NY

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000 FXUS61 KBUF 172357 AFDBUF Area Forecast Discussion National Weather Service Buffalo NY 757 PM EDT Thu Aug 17 2017 .SYNOPSIS...
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Showers and thunderstorms associated with a well-organized low pressure system over Upper Michigan will cross Western and North- Central New York tonight, with more scattered activity possible Friday afternoon as the low center slowly passes to our north. An upper level disturbance will bring another chance for showers Saturday before high pressure dries things out for the latter half of the weekend into Monday. Temperatures will run near to slightly above-normal through the weekend, with warmer temperatures in the mid 80s possible next week.
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&& .NEAR TERM /THROUGH FRIDAY/...
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Water vapor imagery showing a well defined circulation pushing into Lake Superior this evening. A warm front associated with this low is currently moving northeast across the lower Great Lakes. Regional radars showing a broad area of rain with a few embedded heavier convective elements tracking across western New York. This activity will continue to move eastward through midnight. Marginal instability will greatly limit any severe threat, but could have brief very heavy downpours, especially along the Southern Tier with precipitable water values in excess of 2 inches. The low level jet axis fueling the band of precipitation will cross the forecast area tonight, with the bulk of the precipitation exiting the eastern edge of the forecast area Friday morning. However, more scattered showers and thunderstorms are likely Friday afternoon, as the region will remain under the influence of troughing from the surface through the upper levels, as the large, occluded low slowly tracks to our northwest from the UP of Michigan into western Quebec. However, with the LLJ and associated moisture passing to our east, it will not be quite as muggy, with highs in the upper 70s, to lower 80s along the Lake Ontario plain, wheres downsloping southwesterly flow will bump temps up a couple of degrees.
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&& .SHORT TERM /FRIDAY NIGHT THROUGH MONDAY NIGHT/... By Friday night, a cold front will have passed through the region, bringing in cold air advection behind it enough to drop 850mb temperatures to around 10c. Combined with lake temperatures around 22c, this could produce showers overnight but will most likely result in low clouds because of a low cap and very dry air above 850mb. On Saturday, a secondary trough will bring another frontal boundary. This combined with diurnal heating may produce showers inland during the afternoon. Saturday will have the coolest temperatures of the weekend, with highs in the mid 70s and lows in the low 60s. A broad area of high pressure will build over the region Sunday, accompanied by warm and dry air, bringing us back to seasonal temperatures (near 80). High pressure will continue into Monday, where temperatures will begin to climb back up to the low to mid 80s. Monday night, the ridge will still be over the Eastern United States, with low temperatures near normal in the 60s. && .LONG TERM /TUESDAY THROUGH THURSDAY/... This period will be dominated by a steadily amplifying longwave trough over eastern Canada and the Lower Great Lakes. This will lead to notably lower day to day temperatures...although at the onset of the time frame...our temperatures will be well above normal. As for the day to day details... Our region will find itself between systems on Tuesday...as high pressure anchored off the coast and a cold front approaching from the Upper Great Lakes will support a very warm and increasingly humid environment. Temperatures should easily climb into the mid to upper 80s across the lake plains and in the valleys. This airmass will also be increasingly unstable...and while the vast majority of the day will be rain free...some showers and thunderstorms will be possible later in the day. This will mainly be the case over the western counties where lake breeze interactions and/or the presence of a pre-frontal trough could focus convection. A cold front will then push southeast across our forecast area Tuesday night and early Wednesday. Will maintain high chc pops for now...but can easily envision these pops being raised to at least likely as model consistency and forecast confidence increases. Expansive high pressure over the Upper Mississippi Valley Wednesday afternoon will gradually settle to the southeast across the Lower Great Lakes and Ohio Valley by Thursday. This will allow for significant improvement in our weather with fair weather returning...along with a pronounced turn to cooler and more comfortable (lower dew points) conditions. Temperatures by Thursday will average at least 5 deg f below normal. && .AVIATION /00Z FRIDAY THROUGH TUESDAY/...
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Conditions should remain VFR with area of rain and embedded thunderstorms his evening, with brief periods of mvfr/ifr possible in heavier -ra/tsra. As the atmosphere becomes more saturated in the wake of the evening convection, we may see the development of MVFR cigs, with IFR possible across the higher terrain of the Southern Tier, after 06Z. Conditions will improve to VFR after 12Z, as low level moisture mixes out and slightly drier air moves into the region. However, with troughing lingering across the region, expect more scattered - shra/-tsra to develop Fri afternoon, especially inland from the lakes. Outlook... Friday night...Mainly VFR with scattered showers and thunderstorms tapering off in the evening. Saturday...Mainly VFR with a chance of showers. Sunday and Monday...VFR except for late night and early morning valley fog with local IFR. Tuesday...Mainly VFR, with a chance of showers and thunderstorms late.
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&& .MARINE...
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Winds will become southerly tonight as a warm front moves northeast of the area, directing greater wave action into Canadian waters. Low pressure will then move slowly from the western Great Lakes Friday to southern Quebec by Saturday. This will bring an increase in southwesterly winds to the eastern Great Lakes, with Small Craft advisory conditions probable by Friday afternoon for Lake Erie, and Saturday for Lake Ontario. Winds and waves will decrease by Sunday as high pressure builds into the Ohio Valley and eastern Great Lakes.
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&& .BUF WATCHES/WARNINGS/ADVISORIES... NY...None. MARINE...None. && $$ SYNOPSIS...TMA/WOOD NEAR TERM...TMA/WOOD SHORT TERM.../RSH/ZAFF LONG TERM...RSH AVIATION...TMA/WOOD MARINE...HITCHCOCK/TMA/WOOD

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