Area Forecast Discussion
Issued by NWS Buffalo, NY

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000 FXUS61 KBUF 061048 AFDBUF Area Forecast Discussion National Weather Service Buffalo NY 648 AM EDT Thu Aug 6 2020 .SYNOPSIS... High pressure will provide dry weather today. A weak upper level disturbance will then bring an increase in clouds and a chance of showers to Western NY late tonight, then much of the region on Friday. A few showers may linger into Saturday east of Lake Ontario, while mainly dry weather returns to Western NY. Cooler temperatures late this week will give way to increasing warmth and humidity by early next week. && .NEAR TERM /THROUGH TONIGHT/... IR satellite imagery showing a few patches of high cirrus drifting across the eastern Great Lakes this morning. River valley fog in the typical locations across the Southern Tier will dissipate by mid morning. Temperatures this morning are the coolest we have seen since late June, with 50s in most areas and even some upper 40s across the cooler Southern Tier valleys and North Country. High pressure will remain draped from the Midwest into the eastern Great Lakes today, providing dry weather and a good deal of sunshine. Some patches of high/thin cirrus will continue to drift east across the area, and scattered diurnal cumulus will also develop along and inland of the lake breeze boundaries. Temperatures will be a few degrees warmer than yesterday, with highs in the upper 70s at lower elevations and low to mid 70s on the hills and along the Lake Ontario shore. Tonight a weak mid level trough will approach from the west and begin to sharpen with time, reaching Lake Erie and central Ohio by 12Z Friday. Increasing southerly flow ahead of this trough will capture a plume of moisture across the Ohio Valley and mid Atlantic, spreading it north towards western and central NY late tonight. DPVA and isentropic upglide will increase ahead of the mid level trough late tonight, providing an increase in large scale forcing. There remains some differences in model guidance with timing and placement of rain potential, with many of the high-res WRF runs being on the faster and farther west side of the guidance envelope, while the GFS is a little slower and farther east. Given the model differences, went with a compromise solution with POPS reaching the western Southern Tier first around midnight, then spreading north towards the NY Thruway by late tonight. The increase in clouds will keep lows in the upper 50s to lower 60s across Western NY, while less cloud cover across the North Country allows lows to drop into the lower 50s. && .SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/... An upper level trough will approach the area Friday, then slowly cross the lower Great Lakes region Friday night through Saturday. Meanwhile, an area of low pressure will slowly move northeast from the Delmarva to the southern New England coast along a stalled frontal boundary during the same time. Guidance continues to show better chances for precip across our area on Friday, especially across the southern half of our forecast area closer to the deeper moisture associated with the surface low. Forcing and moisture provided by the two above-mentioned features will be enough to produce some occasional light showers/isolated storms across much of the Southern Tier and Finger Lakes region, thus have raised PoPs into the low likely range for these areas, with slight chance and chance PoPs further north. Upper level trough will cross the area Friday night and Saturday, while surface low pressure slowly makes its` way northeast toward the southern New England coast. Deeper moisture associated with the slowly departing low will begin to pull eastward, however with the upper trough overhead, there will still be the chance for some scattered light showers from the Genesee Valley east Friday night into Saturday morning. The upper trough will move into New England Saturday afternoon, while surface low pressure continues northeast along the New England coast. With the better forcing and moisture exiting east of the area, this should allow for any lingering light showers/isolated thunderstorms across the eastern half of our forecast area to taper off by late in the day. High pressure will build in for Saturday night with dry weather expected. Otherwise, temperatures will remain within a few degrees of average. Highs will be in the mid to upper 70s on Friday, with upper 70s to low 80s on Saturday. && .LONG TERM /SUNDAY THROUGH WEDNESDAY/... High pressure centered over the central Appalachians Sunday morning, will slide east off the Mid Atlantic coast by Monday. Despite a weak shortwave embedded in the quasi-zonal flow aloft crossing the area on Sunday, expecting a dry finish to the weekend as there will be little in the way instability or available moisture. A weak warm front will cross the area Sunday night, however with continued limited moisture to work with and little in the way of upper level support, expecting mainly dry conditions with just the chance of a few isolated light showers. A southwesterly return flow of warmer, more humid air will ensue on Monday as surface high pressure slides off the Mid Atlantic coast. There will again be a lack of any upper level energy on Monday. However, with low level moisture/instability on the increase due to the more humid airmass in place, there will be the chance for a diurnally driven storm or two Monday afternoon. After a dry start to Monday night, chances for showers and storms will gradually increase through the night as a cold front approaches from the west. The best chance for showers and storms will come on Tuesday as the cold front moves into the lower Great Lakes region. With the addition of upper level support, some of these storms may be on the stronger side. A few lingering showers and storms will be possible into Tuesday night, before high pressure builds into the region on Wednesday, bringing a return to dry weather. We`ll really start to feel the return of the heat and humidity, especially to start the new work week, with the warm and humid conditions lasting through mid week. High temperatures will be mainly in the lower to mid 80s. However, the warmest day of the next week will Monday, when highs will range from the mid and upper 80s to the lower 90s. The combination of heat and humidity will allow apparent temperatures to climb into the low and possibly mid 90s across the lake plains south of Lake Ontario, Genesee Valley and Finger Lakes region. && .AVIATION /12Z THURSDAY THROUGH MONDAY/... IR satellite imagery showing a few patches of high cirrus level clouds drifting across the eastern Great Lakes this morning. Areas of fog will continue across the river valleys of the western Southern Tier with local IFR, and some of this may impact KJHW briefly as the fog begins to lift out of the valleys below the hilltop airfield. The fog will dissipate by mid morning, leaving VFR to prevail through the rest of the day with nothing more than high cirrus. A mid level trough will approach from the west tonight, reaching Lake Erie and Ohio by 12Z Friday. An area of deeper moisture ahead of the trough over PA will begin to move northward, bringing an increase in mainly VFR level clouds late tonight across the Southern Tier, along with a chance of showers. Outlook... Friday...Areas of MVFR and local/brief IFR with showers likely and a chance of thunderstorms. Saturday...Areas of MVFR with a chance of showers east of Lake Ontario, VFR elsewhere. Sunday through Monday...Mainly VFR. && .MARINE... High pressure will bring light winds today with local lake breezes producing onshore flow this afternoon. Northeast winds will increase on Lake Erie tonight through Friday, producing very choppy conditions especially southwest of Sturgeon Point. Winds and waves are expected to remain below Small Craft Advisory criteria. East to northeast winds will increase a little on Lake Ontario as well, with a light chop along the south shore of the lake. Light winds will return for Saturday. && .BUF WATCHES/WARNINGS/ADVISORIES... NY...None. MARINE...None. && $$ SYNOPSIS...Hitchcock NEAR TERM...Hitchcock SHORT TERM...JM LONG TERM...JM AVIATION...Hitchcock MARINE...Hitchcock

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