026 FXUS61 KBUF 291009 AFDBUF Area Forecast Discussion National Weather Service Buffalo NY 609 AM EDT Mon Jun 29 2026 .WHAT HAS CHANGED... No significant changes to the forecast with this update. && .KEY MESSAGES... 1) Increasing chances for showers and thunderstorms later tonight through Tuesday. 2) Dangerous heat and humidity expected for a majority of the week, then turning more unsettled with slowly lessening heat and humidity for the holiday weekend. && .DISCUSSION... KEY MESSAGE 1...Increasing chances for showers and thunderstorms later tonight through Tuesday. In advance of building ridging that will provide us with an extended spell of heat and humidity for a majority of the week (see Key Message 2 below)...a warm frontal boundary will slide eastward across the area between later tonight and Tuesday. An attendant increase in isentropic ascent/elevated instability along with the potential for a convectively-augmented shortwave rippling southeast along this boundary will bring an increasing potential for at least a few scattered showers and thunderstorms from west to east overnight and Tuesday. With the guidance suite continuing to struggle regarding the details of the timing/placement/coverage of this convection have capped PoPs in the chance to low likely range for now...with the greatest probabilities currently indicated across the eastern Finger Lakes/North Country during Tuesday...in line with a general multimodel consensus. While some uncertainty persists with respect to the extent of morning pcpn/cloud cover and consequently the amount of surface- based instability that can develop during Tuesday...given the amount of shear that will be in place a few stronger to severe storms cannot be ruled out...as is captured by the Marginal Risk in SPC's Day 2 Convective Outlook. Were these to materialize...damaging winds and hail would be the primary risks. KEY MESSAGE 2...Dangerous heat and humidity expected for a majority of the week, then turning more unsettled with slowly lessening heat and humidity for the holiday weekend. Guidance remains in lockstep on upper level ridging building across the eastern CONUS through Thursday...with the core of the ridge strengthening to near 600 dm while drifting east from the Tennessee Valley to the mid-Atlantic coastline. After that time...a series of shortwave impulses digging southeastward across eastern Canada will help to slowly buckle and flatten the ridge Friday through the holiday weekend...with its core correspondingly settling southwestward into the southern Plains/southeastern States. Under this regime...850 mb temps will climb to around +20C by later Tuesday afternoon...then will remain around or even a little above +20C through at least Thursday and possibly even Friday...before pulling back into the mid to upper teens next weekend. At the surface...this will initially translate into highs climbing into the mid and upper 80s today...though that's also about how warm it will actually feel with dewpoints mostly remaining in the tolerable upper 50s to lower 60s. Following the warm frontal passage...heat and humidity will then build in earnest Tuesday and especially Wednesday and Thursday...when daytime highs away from lake influences/the higher terrain will surge into the lower to mid 90s for many areas...with a few of our normal hot spots possibly even reaching the upper 90s. At the same time dewpoints will climb into the lower 70s (and possibly mid 70s in a few spots by midweek)...supporting oppressive heat indices in the upper 90s to lower 100s (heat advisory criteria) for much of our lower elevations each afternoon...with some locations across the Finger Lakes and Niagara/Orleans counties possibly even seeing these briefly approach or reach heat warning criteria (105F) Wednesday/Thursday. At this point...the greatest confidence in meeting heat headline criteria lies south of Lake Ontario Tuesday through Friday...with some potential for convection and associated cloud cover to limit temps across eastern portions of the Finger Lakes and North Country Tuesday...and then possibly again east of Lake Ontario at points Wednesday-Friday. Very warm and muggy nights will also offer little relief from the heat for those without air conditioning...and will increase the likelihood of heat-related illness for vulnerable populations. Aside from the warm frontal passage tonight/Tuesday and the potential for some additional scattered convection across the North Country (which will lie closest to the northern periphery of the ridge) at points Wednesday-Thursday...it should be largely dry much of the time through Thursday. Increasingly more unsettled conditions should then return Friday through the holiday weekend as the ridge slowly flattens and we once again become more subject to shortwave disturbances rippling along its northern periphery...though timing/ placing any such impulses and their related convection remains difficult at best this far in advance. This being said...the general increase in convective potential/associated cloud cover and slowly declining temps aloft should gradually lessen the potential for headline-worthy heat and humidity as we push through the weekend...though it will still likely remain very warm and humid. && .AVIATION /10Z MONDAY THROUGH FRIDAY/... Aside from some spotty IFR/MVFR valley fog across the Southern Tier early this morning...widespread VFR conditions are expected through this evening. An approaching warm frontal boundary will then bring a west-to-east increase in high and mid-level cloud cover during the second half of the upcoming night...with a low chance of showers/ thunderstorms arriving late in the night across far western New York. Outlook... Tuesday...Mainly VFR with scattered showers/thunderstorms and localized flight reductions possible...with the greatest potential for these across the eastern Finger Lakes and North Country. Wednesday and Thursday...Mainly VFR. Friday...Mainly VFR. Chance of showers and thunderstorms. && .MARINE... Lingering surface high pressure will keep light to modest winds and minimal wave action across the Lower Great Lakes today. A warm front will then pass across the region on Tuesday, with modest to moderate southwesterlies then following for the remainder of the week. The warm frontal passage may also bring the potential for at least a few showers and thunderstorms later tonight and Tuesday...some of which could produce locally higher winds and waves. && .BUF WATCHES/WARNINGS/ADVISORIES... NY...None. MARINE...None. && $$ DISCUSSION...JJR AVIATION...JJR MARINE...JJR