FXUS61 KBUF 150638 AFDBUF Area Forecast Discussion National Weather Service Buffalo NY 238 AM EDT Wed Apr 15 2026 .WHAT HAS CHANGED... Severe thunderstorm threat has slightly increased across the Southern Tier this afternoon. Severe thunderstorms risk has also increased Thursday from the Finger Lakes to the southern Tug Hill region, with a Slight Risk (level 2/5) now in place. A Marginal Risk remains for the rest of the forecast area. && .KEY MESSAGES... 1) Warm with rounds of showers and thunderstorms through much of the week. 2) Severe thunderstorms remain possible through Thursday, with locally heavy rainfall also possible through tonight. 3) The very warm pattern continues through Saturday before much colder air arrives by early next week. && .DISCUSSION... KEY MESSAGE 1...Warm with rounds of showers and thunderstorms through the end of the work week. An unsettled and active pattern will continue through the end of the workweek with a WSW-ENE oriented frontal zone draped across the Great Lakes and Northeast. Numerous convectively augmented shortwaves will move through the zonal flow pattern aloft along the frontal zone and support numerous waves of showers and thunderstorms. A weakening MCS will reach Western NY before daybreak today, then move rapidly east across the rest of the area this morning and continue to weaken with time and eastern extent as it races out ahead of the reservoir of stronger instability over the upper Ohio Valley. Expect a period of mainly dry weather for a few hours in the wake of the departing MCS. Another round of scattered to numerous showers and thunderstorms will develop later this afternoon and evening with diurnal instability and the arrival of another convectively augmented shortwave. The best coverage of showers and thunderstorms will likely be late this afternoon through this evening south of the NYS Thruway where greater instability will develop, and forcing is forecast to maximize ahead of the next shortwave. Convection will diminish in coverage overnight as the shortwave moves east and the boundary layer stabilizes. There will still likely be a few scattered showers lingering with deep moisture still in place and the frontal zone lingering nearby. Late tonight through Thursday expect a rinse and repeat pattern, with another potential decaying area of convection arriving early in the morning, followed by additional rounds of showers and a few scattered thunderstorms Thursday afternoon and evening. Friday, a stronger mid level shortwave will cross the eastern Great Lakes in the morning, with a somewhat cooler airmass moving into the region. The cooler air will reduce the chances of thunder. Showers will continue through the first half of the day before tapering off from west to east in the afternoon and evening as a skinny ridge of high pressure builds into the eastern Great Lakes. KEY MESSAGE 2...Severe thunderstorms remain possible in some areas through Thursday, with locally heavy rainfall also possible through tonight. Active weather will persist through much of the week as described in key message (1). The eastern Great Lakes will remain in a "ridge roller" type pattern with multiple convectively enhanced shortwaves spilling across a quasi-stationary E-W oriented thermal boundary over the Great Lakes today through Thursday. This setup will be supportive for a few strong to severe thunderstorms, though the main threat area will differ each period through Thursday. The boundary will finally get shunted more firmly southeast of the region as a cold front Thursday night. The first low-end severe potential will come as a potent MCS moving east of Michigan tracks into the Eastern Great Lakes region. RAP13 environmental analysis depicts 500-1500J/kg of MUCAPE ahead of this complex, though these values decrease with eastward extent into NYS. Shear profiles appear generally unidirectional with 0-6km magnitudes of around 45kts. It is thus expected that this system will hold together and track into the forecast area early this morning, arriving in WNY around 5AM. While this MCS has a history of producing very strong surface winds, the decreasing amount of instability and unfavorable diurnal timing in our area will be working against it and should cause a general weakening trend, especially as it moves further east. Still, it will need to be closely monitored this morning. Behind this initial swath of showers and thunderstorms, there should be a break in the activity until the next convective shortwave arrives later this afternoon. The environment south of the stalled overhead boundary will recover to allow MLCAPE values to increase to around 1000-2000J/kg across the Southern Tier in particular. Wind profiles aloft will also strengthen through overall shear magnitudes will remain similar to those this morning. Severe risk will likely be mostly contingent on the exact track of this next shortwave. Latest hi-res guidance indicates a fairly well-defined QLCS moving into northern Pennsylvania which may partially clip over the NY/PA border, though there are subtle differences in this northern extent. Should this system develop as advertised and take a more northern track, could see a swath of strong wind gusts, marginally severe hail and/or even an isolated tornado in the Southern Tier later this afternoon and early evening. For Thursday, the severe threat will likely be driven by a much broader upstream shortwave that will briefly drive a strong 45kt southwesterly LLJ into the forecast area from the Ohio Valley. The arrival of this jet will likely coincide with peak diurnal heating hours in the afternoon. Instability will likely be greatest (nearing 1000J/kg) in our area across the Finger Lakes and towards the Tug Hill region, which is where the higher risk of severe weather may become focused Thursday. Shear profiles suggest strong multicellular convection growing into line segments may be possible with damaging winds being the primary hazard. In addition to the severe weather threat, given the moist antecendant conditions and PWAT values between 1.25-1.5" through Thursday, there is a low-end threat for excessive rainfall. This would mainly be a concern if the same spatial areas see repeated rounds of convection in quick succession, especially those with complex terrain such as the Southern Tier. Given the relatively quick storm motions expected and fairly large breaks between most rounds of convection, this is not the primary concern but one worth monitoring over the next couple of days. KEY MESSAGE 3...The very warm pattern continues through Saturday before much colder air arrives by early next week. A thermal ridge will build into the eastern Great Lakes and Northeast Saturday just ahead of a deepening trough over the upper Midwest. Temperatures will soar into at least the mid to upper 70s, with 80s a possibility if clouds and showers hold off until late in the day. A strong cold front will then cross the eastern Great Lakes Saturday night, with another round of showers and scattered thunderstorms along and ahead of the front. There may be some severe potential if convection arrives by late afternoon and evening Saturday when stronger diurnal instability is still available. Strong cold advection will develop behind the cold front by Saturday morning. A deep trough will become established across the eastern Great Lakes and Northeast Sunday night through Monday, delivering an unseasonably cold airmass. 850MB temps will bottom out in the -10C to -14C range, more than cold enough to support lake effect and upslope snow showers in a northwest flow regime Sunday night through Monday morning. Moisture appears limited and the favorable synoptic scale setup is brief, so any accumulations will be minor. Highs Monday will only be in the lower 40s at best, and may stay in the 30s if clouds persist most of the day. && .AVIATION /06Z WEDNESDAY THROUGH SUNDAY/... Variable flight conditions expected for the 06z TAF cycle as a couple of convective shortwaves are expected to move into the region, bringing periods of showers and thunderstorms. Conditions are expected to prevail in VFR/MVFR range in most areas through 00z this evening, with IFR cigs at times in the North Country. The first round of convection will arrive at the western terminals (KBUF/KIAG/KROC) between 09z and 10z this morning. This will likely bring TSRA at least as far east as KROC, with sharply decreasing chances across the North Country. Vsbys may briefly dip into IFR range as showers and thunderstorms with this complex move through. While the system is expected to weaken as it arrives and moves through, there is a chance for strong, brief surface wind gusts in excess of 40kts. Following a break in the precipitation, the bulk of the morning hours will be dry until additional convection moves in from the west this afternoon. Thunderstorms are likely in the Southern Tier from KJHW to KELZ between 19z and 02z, with decreasing chances further north and with time further into tonight. A stalled frontal boundary in the vicinity and another approaching shortwave may allow for additional rounds of showers and thunderstorms overnight tonight. Between these showers and warm, moist air flowing across the cold lakes, a mix of MVFR and IFR is expected to prevail across the region with patchy fog developing. Outlook... Thursday and Thursday night...VFR/MVFR with some local IFR at times. Numerous rounds of showers and scattered thunderstorms. Friday...VFR/MVFR with showers possible. Saturday...Mainly VFR with a chance of showers later in the afternoon. Sunday...A mixture of MVFR/IFR with rain showers mixing with and changing to snow through the day. && .MARINE... Multiple rounds of showers and thunderstorms are expected to cross the lakes through Thursday, a few of which may produce strong surface wind gusts and locally higher waves. Otherwise, with the warmer airmass in place and relatively cold lake temperatures, limited mixing of synoptic winds should preclude any prolonged SCA- conditions across the waters. && .BUF WATCHES/WARNINGS/ADVISORIES... NY...None. MARINE...None. && $$ DISCUSSION...Hitchcock/PP AVIATION...PP MARINE...PP