Alert archive / New York / Severe Thunderstorm Watches in 2021
Severe Thunderstorm Watch 495
The Storm Prediction Center issued this severe thunderstorm watch at Sep 12, 2021, 10:25 PM EDT for 13 counties in New York; Erie County, Pennsylvania. It was in force for 4 hr.
The area
The outline as issued.
The facts
- Issued
- Sep 12, 2021, 10:25 PM EDT (02:25 UTC)
- Expired
- Sep 13, 2021, 2:00 AM EDT
- In force
- 4 hr
- Issued by
- the Storm Prediction Center
- Largest hail expected
- 1 in
- Strongest gust expected
- 55 kt
Counties Allegany County, NY, Cattaraugus County, NY, Chautauqua County, NY, Chemung County, NY, Erie County, NY, Genesee County, NY, Livingston County, NY, Ontario County, NY, Schuyler County, NY, Seneca County, NY, Steuben County, NY, Wyoming County, NY, Yates County, NY, Erie County, PA
The radar
The Buffalo radar (KBUF), 36 km from the middle of the area, began a volume at 02:27 UTC, the scan nearest the moment this went out.
Open the radar archive at this moment
The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.
What SPC expected
The probabilities SPC published with the watch, for the watch area over its life.
- Two or more tornadoes
- 10%
- One or more EF2 to EF5 tornadoes
- 2%
- Ten or more severe wind reports
- 40%
- One or more gusts of 65 knots or more
- 10%
- Ten or more severe hail reports
- 10%
- One or more hailstones of 2 inches or more
- 10%
- Six or more combined severe hail and wind reports
- 60%
Warnings issued inside it
8 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Sep 12, 11:00 PM EDT | Severe Thunderstorm Warning | BUF | Cattaraugus, Chautauqua, Erie | 75 min |
| Sep 12, 11:23 PM EDT | Severe Thunderstorm Warning | CLE | Erie | 37 min |
| Sep 12, 11:49 PM EDT | Severe Thunderstorm Warning | BUF | Allegany, Cattaraugus, Chautauqua, Erie, Livingston, Wyoming | 86 min |
| Sep 13, 12:09 AM EDT | Severe Thunderstorm Warning | BUF | Erie, Genesee, Wyoming | 66 min |
| Sep 13, 12:25 AM EDT | Flash Flood Warning | BUF | Erie, Genesee, Wyoming | 3 hr |
| Sep 13, 12:45 AM EDT | Severe Thunderstorm Warning | BGM | Chemung, Schuyler, Seneca, Steuben, Yates | 60 min |
| Sep 13, 12:50 AM EDT | Severe Thunderstorm Warning | BUF | Livingston, Ontario | 55 min |
| Sep 13, 1:26 AM EDT | Severe Thunderstorm Warning | BGM | Cayuga, Chemung, Cortland, Schuyler, Seneca, Steuben and 3 more | 53 min |
Discussions around it
SPC mesoscale discussions over the same counties from four hours before the watch to its end.
The nearest sounding before it
Buffalo Intl Airport, NY (KBUF), launched 00:00Z, 2.4 hours before the alert went out and 34 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.
- Mixed-layer CAPE
- 412 J/kg
- Mixed-layer CIN
- -125 J/kg
- Mixed-layer LCL
- 706 m above ground
- 0-6 km bulk shear
- 50 kt
- 0-1 km storm-relative helicity
- 205 m²/s²
- 0-3 km storm-relative helicity
- 168 m²/s²
- Significant tornado parameter
- 0.2
- Supercell composite
- 1.5
The text
As transmitted.
136 WWUS20 KWNS 130222 SEL5 SPC WW 130222 NYZ000-PAZ000-LEZ000-130600- URGENT - IMMEDIATE BROADCAST REQUESTED Severe Thunderstorm Watch Number 495 NWS Storm Prediction Center Norman OK 1025 PM EDT Sun Sep 12 2021 The NWS Storm Prediction Center has issued a * Severe Thunderstorm Watch for portions of Eastern New York Far Northwest Pennsylvania Lake Erie * Effective this Sunday night and Monday morning from 1025 PM until 200 AM EDT. * Primary threats include... Scattered damaging wind gusts to 65 mph possible SUMMARY...A compact elevated bow across southwest Ontario should spread into western New York before weakening overnight. The severe thunderstorm watch area is approximately along and 40 statute miles north and south of a line from 50 miles west northwest of Jamestown NY to 35 miles north northeast of Elmira NY. For a complete depiction of the watch see the associated watch outline update (WOUS64 KWNS WOU5). PRECAUTIONARY/PREPAREDNESS ACTIONS... REMEMBER...A Severe Thunderstorm Watch means conditions are favorable for severe thunderstorms in and close to the watch area. Persons in these areas should be on the lookout for threatening weather conditions and listen for later statements and possible warnings. Severe thunderstorms can and occasionally do produce tornadoes. && AVIATION...A few severe thunderstorms with hail surface and aloft to 1 inch. Extreme turbulence and surface wind gusts to 55 knots. A few cumulonimbi with maximum tops to 550. Mean storm motion vector 28060. ...Grams
SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Sep 12, 9:14 PM EDT | Mesoscale Discussion | SPC | Erie | 91 min |
| Sep 13, 12:26 AM EDT | Mesoscale Discussion | SPC | Allegany, Broome, Chemung, Chenango, Cortland, Delaware and 9 more | 94 min |
| Sep 13, 4:11 PM EDT | Mesoscale Discussion | SPC | Allegany, Cattaraugus, Chautauqua | 2 hr |
| Sep 13, 5:53 PM EDT | Severe Thunderstorm Watch | SPC | Cameron, Centre, Clarion, Clearfield, Clinton, Columbia and 14 more | 3 hr |
| Sep 13, 7:07 PM EDT | Mesoscale Discussion | SPC | Carbon, Centre, Clearfield, Columbia, Jefferson, Luzerne and 5 more | 113 min |
| Sep 13, 7:44 PM EDT | Severe Thunderstorm Watch | SPC | Bucks, Carbon, Lehigh, Luzerne, Monroe, Northampton | 4 hr |
Nearby
Severe Thunderstorm Watches in New York, 2021Severe Thunderstorm Watches in Pennsylvania, 2021Every severe thunderstorm watch in 2021
Sources
The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.