A cold front dropped southward across the region and interacted with modestly moist and unstable conditions. A humid boundary layer was in place as evidenced by surface dewpoints in the upper 60s to lower 70s.
Every event with a place to put it. Tap one for its entry below.
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.
A cold front dropped southward across the region and interacted with modestly moist and unstable conditions. A humid boundary layer was in place as evidenced by surface dewpoints in the upper 60s to lower 70s. All of this worked to generate widespread thunderstorms mid-afternoon into the early evening over the Southern Tier. A cold front came through in pieces though with first a wind shift to the north noted as early as the early afternoon over Southern Tier, however lower dewpoints failed to arrive until late evening and overnight. Strong low level lapse rates were present, however shear was weak and the mean layer flow was only around 5 knots. The one hour flash flood guidance was about 1.5 inches across the Southern Tier. The storms that developed were very slow movers and flash flooding was observed in all three southern Tier counties. Storms that had stronger cores aloft produced isolated downbursts in southeastern Chautauqua County and southeastern Allegany County. Of interest, peak wind gusts with convection came from the east, which is a non-typical wind direction. This likely resulted in more wind damage to trees than normal for these cells.
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 Jun 9, 10:38 AM EST, 3 hours 2 minutes earlier.
Area Forecast Discussion National Weather Service Buffalo NY 1138 AM EDT Wed Jun 9 2021 .SYNOPSIS... Another warm and humid day anticipated with a risk of showers and thunderstorms as a cold front sweeps through the region. Mainly Dry and cooler Thursday but there will remain a small chance of a shower or storm over the Southern Tier. Weak system moves through Friday with again a chance of a few showers or a thunderstorm. && .NEAR TERM /THROUGH THURSDAY/... Only minor changes needed to going forecast for the afternoon. Marine advection fog is hanging tough within a mile of the Lake Erie shoreline in Downtown Buffalo and also along the southeast and eastern shoreline of Lake Ontario. Lingered the fog in the forecast a couple more hours before it finally dissipates. Thunderstorms still expected to develop early to mid afternoon as MLCAPES rise over 1000 j/kg and backdoor cold front drops crossing northern North Country continues to drop across region. Similar to yesterday, deep layer shear weak and storm motions slow, so heavy rainers will be primary hazard. A bit more dry air in the mid-levels today per 12z BUF sounding so DCAPE will be slightly higher this afternoon, thus stronger storms that build higher cores will also pose risk of stronger wind gusts. Behind the front, chances for storms will quickly diminish in coverage as a drier air mass begins to work into the Lower Lakes. Still anticipating a muggy and very warm day ahead of the front, highs may be a tad bit warmer than yesterday as H850T nudge up a degree or two. Highs in the mid to upper 80s to around 90F in the warmest locations from the Genesee valley toward the Finger Lakes. Tonight, showers and thunderstorms will diminish from north to south with humidity levels beginning to slowly fall off overnight. A cooler air mass will also begin to infiltrate from the northeast into the region. The greatest impact from the cooler airmass will be felt over the North Country as we head into Thursday. Lows anticipated in the mid 50s east of Lake Ontario to the upper 50s to low 60s elsewhere by sunrise. Skies will turn mostly clear later in the night just in time for the solar eclipse that will impact our area around daybreak on Thursday. Thursday, sfc high pressure from the Hudson Bay to the Gulf of Maine will largely provide a dry and pleasant day. With that said, there may still be a small chance of a shower or storm along the NY/PA board where the cold front will stall to our south. Otherwise, nice day anticipated with highs in the upper 70s to low and mid 80s with less humidity. && .SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/... Chance for showers temporarily pushes south of the NY/PA line Thursday night. On Friday, signs showing up in latest round of model guidance that primary front may not make it too far into NY. Main mechanism for showers and thunderstorms now on Friday may just be daytime heating and convergence along weak lake breeze boundaries. && .LONG TERM /SATURDAY THROUGH TUESDAY/... The long term period will be fairly active with the overall pattern featuring a few different mid/upper level troughs that will cause showers and the potential for thunderstorms. The best chance for showers and thunderstorms will be on Sunday, but each day during the long term has at least slight chance POPs in place with the overall lack of high pressure/ridging over the region. Guidance suggests general larger scale troughing develops early next week over the Great Lakes and Northeast as a large area of high pressure and ridging dominate the western half of the country. The building trough over the Northeast will continue the active pattern, and bring cooler and less humid conditions compared to what is occurring this week. && .AVIATION /16Z WEDNESDAY THROUGH SUNDAY/... Lingering MVFR cigs at KART will diminish by early afternoon. Otherwise, VFR conditions will prevail rest of today all areas. A back door cold front will sweep through the region today, occurring at present over the North Country (KART), then across all other terminals this afternoon and evening. With its arrival, some showers and storms will be possible with brief periods of IFR/MVFR within any storms at area terminals, especially across the S. Tier. Tonight, the passage of the front will allow for VFR to resume at all terminals. Skies will become mostly clear late evening and overnight. Outlook... Thursday and Friday...Mainly VFR. A few spotty showers or storm still possible across the S. Tier. Saturday and Sunday...Mainly VFR. Chance of showers and thunderstorms, especially Sunday. && .MARINE... Back door cold front will sweep across the region today with some showers and storms. Light wind flow will then veer to the east and northeast behind the front with moderate winds resulting in choppier conditions at times through Thursday lasting into Friday, especially on Lake Ontario. && .BUF WATCHES/WARNINGS/ADVISORIES... NY...None. MARINE...None. && SYNOPSIS...AR NEAR TERM...AR/JLA SHORT TERM...JLA LONG TERM...JLA/SW AVIATION...AR/JLA MARINE...AR
Hazardous Weather Outlook National Weather Service Buffalo NY 521 AM EDT Wed Jun 9 2021 NYZ001>008-010-011-100930- Niagara-Orleans-Monroe-Wayne-Northern Cayuga-Oswego-Jefferson-Lewis- Northern Erie-Genesee- 521 AM EDT Wed Jun 9 2021 This Hazardous Weather Outlook is for portions of western and north central New York. .DAY ONE...Today and tonight. No hazardous weather is expected at this time. .DAYS TWO THROUGH SEVEN...Thursday through Tuesday. No hazardous weather is 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 LEZ040-041-LOZ042>045-062>065-100930- Lake Erie nearshore waters from Ripley to Dunkirk- Lake Erie nearshore waters from Dunkirk to Buffalo- 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- 521 AM EDT Wed Jun 9 2021 This Hazardous Weather Outlook is for portions of Lake Erie and Lake Ontario. .DAY ONE...Today and tonight. No hazardous weather is expected at this time. .DAYS TWO THROUGH SEVEN...Thursday through Tuesday. No hazardous weather is 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 LEZ020-LOZ030-SLZ022-024-100930- Upper Niagara River and Buffalo Harbor-Lower Niagara River- Saint Lawrence River from Cape Vincent to Ogdensburg- Saint Lawrence River from Ogdensburg to Saint Regis- 521 AM EDT Wed Jun 9 2021 This Hazardous Weather Outlook is for portions of Lake Erie, Lake Ontario and Saint Lawrence River. .DAY ONE...Today and tonight. No hazardous weather is expected at this time. .DAYS TWO THROUGH SEVEN...Thursday through Tuesday. No hazardous weather is 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 NYZ012>014-019>021-085-100930- Wyoming-Livingston-Ontario-Chautauqua-Cattaraugus-Allegany- Southern Erie- 521 AM EDT Wed Jun 9 2021 This Hazardous Weather Outlook is for portions of western New York. .DAY ONE...Today and tonight. Scattered thunderstorms this afternoon will be capable of producing locally heavy rain which could lead to minor flooding. .DAYS TWO THROUGH SEVEN...Thursday through Tuesday. No hazardous weather is 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 Reynolds
Special Weather Statement National Weather Service Buffalo NY 851 AM EDT Wed Jun 9 2021 NYZ006-007-091400- Oswego-Jefferson- Including the cities of Oswego and Watertown 851 AM EDT Wed Jun 9 2021 ...Areas of Dense Fog East of Lake Ontario This Morning... Areas of dense fog east of Lake Ontario shore will persist through 10 AM...before gradually diminishing the rest of the morning. Visibility near the Lake Ontario shoreline and in the higher terrain will be as low as just a few hundred feet at times. If traveling this morning east of Lake Ontario...allow extra time to reach your destination and be sure to leave plenty of room between vehicles. JLA
Special Weather Statement National Weather Service Buffalo NY 128 PM EDT Wed Jun 9 2021 NYZ019>021-091900- Chautauqua-Cattaraugus-Allegany- 128 PM EDT Wed Jun 9 2021 ...DEVELOPING THUNDERSTORMS WILL AFFECT SOUTHERN CATTARAUGUS... SOUTHERN CHAUTAUQUA AND SOUTHERN ALLEGANY COUNTIES... At 124 PM EDT, radar indicated thunderstorms were developing along a line extending from near Clymer to Andover and Whitesville. The storms are moving southwest at 10 mph. The strongest cluster of storms will impact far southeast Allegany county as storms over Stueben county move westward into the area. Winds in excess of 40 mph and pea size hail are possible with these storms. Locations impacted include... Jamestown, Olean, Salamanca, Wellsville, Allegany State Park, Lakewood, Falconer, Allegany, Clymer, St. Bonaventure, Jamestown West, Whitesville, Weston Mills, Frewsburg, Busti, Hinsdale, Scio, Carrollton, Celoron and Bolivar. This includes Interstate 86 near exit 12, between exits 17 and 19, and between exits 21 and 26. Torrential rainfall is also occurring with these storms, and may cause localized flooding. Do not drive your vehicle through flooded roadways. These storms may intensify, so be certain to monitor local radio stations and available television stations for additional information and possible warnings from the National Weather Service. LAT...LON 4200 7976 4210 7976 4220 7774 4200 7775 TIME...MOT...LOC 1724Z 029DEG 4KT 4206 7964 4212 7765 JLA
Special Weather Statement National Weather Service Buffalo NY 233 PM EDT Wed Jun 9 2021 NYZ021-091900- Allegany- 233 PM EDT Wed Jun 9 2021 ...A STRONG THUNDERSTORM WILL AFFECT SOUTH CENTRAL ALLEGANY COUNTY... At 233 PM EDT, a strong thunderstorm was located near Wellsville, moving southwest at 15 mph. Winds in excess of 40 mph and half inch hail are possible with this storm. Locations impacted include... Wellsville, Alma, Stannards and Knight Creek. Torrential rainfall is also occurring with this storm, and may cause localized flooding. Do not drive your vehicle through flooded roadways. Frequent cloud to ground lightning is occurring with this storm. Lightning can strike 10 miles away from a thunderstorm. Seek a safe shelter inside a building or vehicle. LAT...LON 4200 7824 4215 7798 4203 7784 4200 7787 TIME...MOT...LOC 1833Z 046DEG 15KT 4204 7797 Mitchell
The Buffalo radar (KBUF), 115 km away, was scanning. The volume nearest the first event began at 18:41 UTC.
5 flash flood, 3 thunderstorm wind. Local standard time, as filed.
Multiple trees were downed in the Trout Run Camp Resort.
State route 305 was closed due to water flowing over the roadway.
A section of Hoyett Road was washed out in West Clarksville.
Route 219 flooded and closed in front of the Dollar General.
Water was pouring into four homes with at least four feet of water in each. The fire department was unable to successfully pump the water out for a time due to the rate of water coming into each home.
Trees were downed onto Garfield Road.
South Main Street Extension closed from Bacon Road to the Pennsylvania state line due to high water.
Trees were downed onto power lines east of Busti between Forest Avenue and South Main Street Extension.
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 historyWarnings in New York, June 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: 968830, 968823, 968824, 968827, 968829, 968831, 968826, 968832.