An approaching cold front triggered showers and thunderstorms across the area. An upstream elevated mixed layer and associated mesoscale convective vortex allowed for convection to cross from lower Michigan, across southern Ontario, and into western New York by late in the evening.
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Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS BUF wrote it up.
An approaching cold front triggered showers and thunderstorms across the area. An upstream elevated mixed layer and associated mesoscale convective vortex allowed for convection to cross from lower Michigan, across southern Ontario, and into western New York by late in the evening. Sufficient deep layer shear was present to support continued severe activity as the storms approached our area. A quasi-linear convective system resulted as the activity moved through, resulting in widespread wind damage reports and one confirmed tornado.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Buffalo, NY wrote its last area forecast discussion before the first event at Sep 12, 7:22 PM EST, 3 hours 26 minutes earlier.
Area Forecast Discussion National Weather Service Buffalo NY 822 PM EDT Sun Sep 12 2021 .SYNOPSIS... A cold front dropping across the region will support showers and scattered thunderstorms. Some of the thunderstorms could produce strong winds and heavy rainfall. Unsettled weather will continue through the middle of next week with possible showers and thunderstorms. && .NEAR TERM /THROUGH MONDAY/... ...Scattered severe thunderstorms possible tonight... An MCV crossing Lower Michigan this evening is generating strong to severe convection. Upstream soundings from 18z were showing a pronounced EML...and now 00z soundings from KBUF and KDTX continue to show the very favorable environment. CAMs have been consistent with timing the convection after 04z for the western counties of New York...although some 'garden variety' storms will be possible in the hours leading up to that. The main severe weather threat will be damaging straight line winds...but there should be intense downpours and frequent lightning under the cores as they move through. Convection will diminish late tonight as the shortwave (MCV in this case) will push east. Some partial clearing could bring some fog especially to areas that receive rain. Frontal boundary does look to sneak south of the area briefly on Monday, but will start to work back north as a warm front Monday afternoon. Shortwave pushing across the area will trigger some scattered convection along the frontal boundary late in the day. && .SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY NIGHT/... A stationary front will be oriented northwest to southeast from northern Michigan to northwest Pennsylvania Monday night. Surface high pressure will be inching into the North Country resulting in dry conditions from the Finger Lakes into the North Country. A weak impulse is forecast to ride along the front further west and showers with a slight chance of thunderstorms are possible across far western NY including the western Southern Tier. Overnight lows will range from the low 50s across the North Country to the upper 50s low 60s across western NY. The front will move north as a warm front across western and north central NY Tuesday. Dewpoints and mid-level moisture will increase while surface temperatures climb to the upper 70s to low 80s. Surface based instability will climb with strong winds in the low to mid levels. Showers and thunderstorms will likely form by afternoon ahead of an approaching cold front. Some storms may become strong to severe in the afternoon into the evening. Main threats would be strong winds and large hail. Thunderstorms will track east with a short break before another round of showers and storms enters the region as a cold front approaches from the west. Uncertainty exists Tuesday night as the wind field and surface based instability decreases ahead of the front. Warm, overnight night with lows in the 60s. Model guidance is in agreement that widespread showers or rain with thunderstorms will track across the entire forecast area Wednesday and Wednesday as the cold front tracks east. This increase in low level convergence will initiate thunderstorm development with some strong to severe storms. The strongest storms are expected to be east of the forecast area however if the front slows down that could change. Slightly cooler Wednesday with highs in the mid to upper 70s. && .LONG TERM /THURSDAY THROUGH SUNDAY/... A sfc ridge will provide for mostly quiet weather for the first half of the long term period. Some guidance is suggesting an upper level trough/low over eastern PA and southern New England may cause some showers for the area. Will need to see how the scenario evolves as there is decent model spread still with how much of an impact these upper level features will have. For now have high slight chance to low chance POPs. A frontal boundary passing south across the area on Sunday will bring a few showers and some thunderstorms. The front will then shift back north as a warm front later on Sunday into Monday. Temps during the long term will be 5 to 10 degree above normal for this period. && .AVIATION /01Z MONDAY THROUGH FRIDAY/... Complex of thunderstorms with gusty winds and heavy rain looking likely to roll across western NY after 3/4z. Brief IFR possible during these storms. After the storms later tonight, expect MVFR ceilings with IFR possible across the southern Tier. May see some fog as well if any clearing occurs. Outlook... Monday and Tuesday...Mainly VFR with a chance of showers. Wednesday...Mainly MVFR with widespread showers. Thursday and Friday...Mainly VFR. && .MARINE... A pseudo stationary cold front straddling Lakes Erie and Ontario early this evening will gradually push south overnight. In its wake...gentle to moderate northwesterlies will become established. While winds and waves will average below small craft advisory criteria...there will be the risk for strong thunderstorms between 04 and 08z...particularly over Lake Erie. mariners should be alert for possible special marine warnings. High pressure centered over northern Ontario will start to pass by the north on Monday. This will support light and variable winds on Lake Erie and light northwesterlies on Lake Ontario. As the area of high pressure moves east across Quebec on Tuesday...a cold front will approach from the Upper Great lakes. A tightening sfc gradient between the two will lead to freshening winds on both Lakes Erie and Ontario. && .BUF WATCHES/WARNINGS/ADVISORIES... NY...None. MARINE...None. && SYNOPSIS...TMA NEAR TERM...RSH/TMA SHORT TERM...HSK LONG TERM...SW AVIATION...JLA/TMA MARINE...JLA/TMA
Hazardous Weather Outlook National Weather Service Buffalo NY 624 PM EDT Sun Sep 12 2021 NYZ001>006-008-010>014-019>021-085-132230- Niagara-Orleans-Monroe-Wayne-Northern Cayuga-Oswego-Lewis- Northern Erie-Genesee-Wyoming-Livingston-Ontario-Chautauqua- Cattaraugus-Allegany-Southern Erie- 624 PM EDT Sun Sep 12 2021 This Hazardous Weather Outlook is for portions of western and north central New York. .DAY ONE...Tonight. There is a marginal risk for severe thunderstorms tonight. The primary hazard is damaging wind gusts, though heavy rain is also possible. .DAYS TWO THROUGH SEVEN...Monday through Saturday. There is a marginal risk for severe thunderstorms on Tuesday. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected at this time. This product, along with other watches, warnings, advisories, and statements issued by the National Weather Service office in Buffalo can be found on the internet at http://www.weather.gov/buf NYZ007-132230- Jefferson- 624 PM EDT Sun Sep 12 2021 This Hazardous Weather Outlook is for portions of central New York. .DAY ONE...Tonight. Hazardous weather is not expected at this time. .DAYS TWO THROUGH SEVEN...Monday through Saturday. There will be the risk for severe thunderstorms on Tuesday. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected at this time. This product, along with other watches, warnings, advisories, and statements issued by the National Weather Service office in Buffalo can be found on the internet at http://www.weather.gov/buf LEZ020-040-041-LOZ030-132230- Upper Niagara River and Buffalo Harbor- Lake Erie nearshore waters from Ripley to Dunkirk- Lake Erie nearshore waters from Dunkirk to Buffalo- Lower Niagara River- 624 PM EDT Sun Sep 12 2021 This Hazardous Weather Outlook is for portions of Lake Erie and Lake Ontario. .DAY ONE...Tonight. There is a slight risk for severe thunderstorms tonight. The primary hazard is damaging wind gusts. .DAYS TWO THROUGH SEVEN...Monday through Saturday. There is a marginal risk for severe thunderstorms Monday and Tuesday. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected at this time. This product, along with other watches, warnings, advisories, and statements issued by the National Weather Service office in Buffalo can be found on the internet at http://www.weather.gov/buf LOZ042>045-062>065-SLZ022-024-132230- Lake Ontario nearshore waters from the Niagara River to Hamlin Beach- Lake Ontario nearshore waters from Hamlin Beach to Sodus Bay- Lake Ontario nearshore waters from Sodus Bay to Mexico Bay- Lake Ontario nearshore waters from Mexico Bay to the Saint Lawrence River- Lake Ontario open waters from the Niagara River to Hamlin Beach- Lake Ontario open waters from Hamlin Beach to Sodus Bay- Lake Ontario open waters from Sodus Bay to Mexico Bay- Lake Ontario open waters from Mexico Bay to the Saint Lawrence River- Saint Lawrence River from Cape Vincent to Ogdensburg- Saint Lawrence River from Ogdensburg to Saint Regis- 624 PM EDT Sun Sep 12 2021 This Hazardous Weather Outlook is for portions of Lake Ontario and Saint Lawrence River. .DAY ONE...Tonight. There is a slight risk for severe thunderstorms tonight. The primary hazard is damaging wind gusts. .DAYS TWO THROUGH SEVEN...Monday through Saturday. Hazardous weather is not expected at this time. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected at this time. This product, along with other watches, warnings, advisories, and statements issued by the National Weather Service office in Buffalo can be found on the internet at http://www.weather.gov/buf
Special Weather Statement National Weather Service Buffalo NY 833 PM EDT Sun Sep 12 2021 NYZ001-002-010>012-019>021-085-130200- Niagara-Orleans-Northern Erie-Genesee-Wyoming-Chautauqua- Cattaraugus-Allegany-Southern Erie- Including the cities of Niagara Falls, Medina, Buffalo, Batavia, Warsaw, Jamestown, Olean, Wellsville, Orchard Park, and Springville 833 PM EDT Sun Sep 12 2021 ...Strong Thunderstorms Possible after Midnight... Conditions will deteriorate across western New York this evening... as showers will become more widespread while the potential for thunderstorms will increase. Storms that develop this evening will contain some lightning and possibly wind gusts to 30 mph...but the risk for strong to severe thunderstorms should hold off until later tonight. Strong to severe thunderstorms over Lower Michigan at 8:30 PM will track east and are forecast to impact the western counties of New York after midnight. At that time...thunderstorms will contain intense downpours...frequent cloud to ground lightning and possibly damaging wind gusts. While western New York in general will have the risk for this stronger activity...the greatest threat will be found south of Buffalo and Rochester. RSH
The Buffalo radar (KBUF), 74 km away, was scanning. The volume nearest the first event began at 03:51 UTC.
6 thunderstorm wind, 1 flash flood, 1 tornado. Local standard time, as filed.
Multiple trees were reported down.
A tree was reported to be down onto a mobile home.
Multiple trees were reported to be down with a horse shed destroyed.
A tree was downed onto a powerline.
Trees were reported downed onto a roadway.
A tree was reported downed onto a powerline.
Water was flowing over several streets with a depth up to the bottom of the car doors in some spots.
Dozens of hardwood and softwood tree trunks were sheared in half with damage to the roof of an outdoor shed. The track of the tornado started just west of Route 15 and ended just east of Marrowback Road.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in New York in 2021Every state in 2021This day in weather historyThe tornado archive for New York, 2021Warnings in New York, September 2021
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 986826, 986827, 986828, 986829, 986830, 986831, 986833, 986834.