Area Forecast Discussion
Issued by NWS Buffalo, NY

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000 FXUS61 KBUF 231557 AFDBUF Area Forecast Discussion National Weather Service Buffalo NY 1157 AM EDT Sun Sep 23 2018 .SYNOPSIS... An area of high pressure will maintain fair weather and seasonably cool temperatures through the remainder of the weekend. Temperatures will climb back above normal Monday and through mid-week. A storm system will bring the next chance for rain showers Monday night, with unsettled weather remaining through Wednesday night. && .NEAR TERM /THROUGH TONIGHT/... Surface high pressure will edge towards New England this afternoon, with fair weather, plenty of sunshine and temperatures warming back into the 60s. Tonight will not be as cold as this morning as the main pool of cold air aloft is displaced eastward, and a light easterly flow begins with the departure of the surface high. Skies tonight will again be mainly clear. && .SHORT TERM /MONDAY THROUGH WEDNESDAY NIGHT/... Our first rain of astronomical fall is expected to arrive during the first half of this week although temperatures will run 5 to 10 degrees above normal. Monday into Monday night a surface high will shift from central Quebec east to center over the Canadian Maritimes. In this process, winds across New York will increase and further veer from southeast to south by daybreak Tuesday. Warm air advection and moisture transport will increase with a warm front lifting across the upper Great Lakes by Tuesday morning. While Monday morning will remain dry, enhanced synoptic moisture will support chance POPs across WNY by Monday afternoon with likely to categorical POPs for rain showers Monday night. The warm air advection will push temperatures back above normal for Monday with highs in upper 60s to lower 70s. Lows Monday night will run a bit more milder than recent nights with cloud cover and showers. The flavor of Tuesday and Wednesday will be warm and showery with a chance for some thunderstorms depending on available instability. Western and north-central NY will be within the warm sector of low pressure well to our north crossing northern Quebec Tuesday. The lack of a surface front crossing our region during this time should result in scattered to at times widespread rain showers ahead of a cold front into Tuesday night. Instability per 00z GFS SBCAPE looks weak with less than 500 J/kg but bulk wind shear of 35-45knots during this time could support some isolated to scattered storms perhaps reaching severe levels. SPC has included our forecast area in a Day 3 Marginal Risk largely due to available wind shear. 00z model consensus is to push the surface cold front across the eastern Great Lakes Wednesday with high pressure then building across our region in its wake Wednesday night. PWAT anomaly of +2 top +3 shows atmospheric moisture will be above normal especially Tuesday night and Wednesday where showers and storms would likely bring heavy downpours. SBCAPE forecast by 00z GFS climbs a bit higher Wednesday with perhaps some pockets reaching near or above 1000 j/kg ahead of the cold front while bulk shear may reach near 50 kts. This has lead to a Day 4 (Wednesday) severe weather outlook across New York state. Forecast QPF through 00z Wednesday is around one-half inch but factoring in heavy rain possible through Tuesday night the WPC 1-3 Day QPF is one to one and one-half inches. As mentioned above temps will run above normal with highs generally in the low to mid 70s Tuesday and Wednesday. Lows dipping into the 50s Monday night but then not fall below the 60s Tuesday night. A cold and dry air mass arriving from Canada Wednesday night will help temps to slip back into the low 50s for most. && .LONG TERM /THURSDAY THROUGH SATURDAY/... Generally benign weather can be expected across our region during this period...as a deamplifying longwave trough over the center of the country will evolve into a pseudo zonal flow with the main H25 jet aligned from the high plains to the St Lawrence Valley. This will support temperatures that will average close to normal throughout the period. In the wake of a cold front...high pressure will make its way across the Lower Great Lakes to New England on Thursday. This will result in cooler weather than the days leading up to this point...as H85 temps in the vcnty of 6c will only support afternoon highs in the upper 60s. Otherwise it will be a pleasant day that will feature a fair amount of sunshine. A stacked storm system tracking just northwest of Lake Superior looks to push an occluding frontal system across the lower Great Lakes Thursday night. A triple point along this occlusion will be found in the vcnty of Georgian Bay or southern Ontario. This feature will serve as the pivot for an advancing weak warm front that will do little more than to increase some high and mid level clouds over our forecast area with a slight chance of some showers. As the parent storm system moves to near James Bay on Friday...its negatively tilted mid level support will push a cold front across our region. While this may lead to scattered showers...the majority of the day will be rain free. Colder air in the wake of the front will overspread the Lower Great Lakes Friday night...while a very broad...low amplitude trough will become situated across the eastern half of Canada. H85 temps in the lower single digits c will certainly support some instability over the lakes...but will there be enough synoptic moisture to allow for a legitimate lake response? From this long range vantage point...it appears that low and mid level moisture will be limited...but the confidence is not high enough to rule out some nuisance showers. This will mainly be the case for sites east of Lake Ontario in the vcnty of the Tug Hill. Otherwise...an uneventful night is expected. On Saturday, high pressure stretching from the oil fields of western Canada to the Mid Atlantic region should encourage fair dry weather over our region although the 00z GFS is showing another cold front passage across the Great Lakes. It should be relatively cool though as H85 temps in the lower single digits c will only support afternoon highs in the low to mid 60s. && .AVIATION /16Z SUNDAY THROUGH THURSDAY/... Widespread VFR conditions are expected this afternoon and early tonight. Winds will remain light as surface high pressure remains near the region. High clouds will begin to increase late tonight and will likely restrict any fog to the immediate river valleys of southern New York, with KJHW likely to remain VFR through the night. Outlook... Monday...VFR. Showers likely late Monday night. Tuesday and Wednesday...Areas of MVFR (IFR possible in So. Tier) with showers likely. Thursday...Mainly VFR. && .MARINE... Area of high pressure was over the eastern Great Lakes early this afternoon, with light winds and minimal waves on the lakes. These light winds and low wave heights will continue through the first half of tonight. As the surface high moves eastward late tonight and into Monday an easterly flow will increase on the Lakes, with possible small craft conditions late tonight in Monday. Ahead of a cold front slowly marching eastward towards the eastern Great Lakes a southerly flow will begin to increase later Monday through Wednesday, with a likely bring another round of small craft conditions on the lakes. && .BUF WATCHES/WARNINGS/ADVISORIES... NY...None. MARINE...None. && $$ SYNOPSIS...Thomas/TMA NEAR TERM...Thomas/TMA SHORT TERM...Smith LONG TERM...RSH/Smith AVIATION...Thomas/TMA MARINE...Thomas/TMA

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