Alert archive / North Carolina / Tornado Watches in 2021
Tornado Watch 446
The Storm Prediction Center issued this tornado watch at Aug 17, 2021, 6:28 PM EDT for 30 counties in North Carolina; 15 counties in South Carolina; 21 counties in Virginia. It was in force for 10 hr.
The area
The outline as issued.
The facts
- Issued
- Aug 17, 2021, 6:28 PM EDT (22:28 UTC)
- Expired
- Aug 18, 2021, 4:00 AM EDT
- In force
- 10 hr
- Issued by
- the Storm Prediction Center
- Largest hail expected
- 0.5 in
- Strongest gust expected
- 50 kt
All 66 counties
Alexander County, NC, Alleghany County, NC, Ashe County, NC, Avery County, NC, Buncombe County, NC, Burke County, NC, Cabarrus County, NC, Caldwell County, NC, Caswell County, NC, Catawba County, NC, Cleveland County, NC, Davie County, NC, Gaston County, NC, Henderson County, NC, Iredell County, NC, Lincoln County, NC, McDowell County, NC, Mecklenburg County, NC, Mitchell County, NC, Polk County, NC, Rockingham County, NC, Rowan County, NC, Rutherford County, NC, Stokes County, NC, Surry County, NC, Union County, NC, Watauga County, NC, Wilkes County, NC, Yadkin County, NC, Yancey County, NC, Cherokee County, SC, Chester County, SC, Fairfield County, SC, Greenville County, SC, Greenwood County, SC, Kershaw County, SC, Lancaster County, SC, Laurens County, SC, Lexington County, SC, Newberry County, SC, Richland County, SC, Saluda County, SC, Spartanburg County, SC, Union County, SC, York County, SC, Bedford County, VA, Botetourt County, VA, Carroll County, VA, City of Danville, VA, City of Galax, VA, City of Martinsville, VA, City of Radford, VA, City of Roanoke, VA, City of Salem, VA, Craig County, VA, Floyd County, VA, Franklin County, VA, Grayson County, VA, Henry County, VA, Montgomery County, VA, Patrick County, VA, Pittsylvania County, VA, Pulaski County, VA, Roanoke County, VA, Smyth County, VA, Wythe County, VA
The radar
The Greer radar (KGSP), 123 km from the middle of the area, began a volume at 22:29 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
- 70%
- One or more EF2 to EF5 tornadoes
- 20%
- Ten or more severe wind reports
- 20%
- One or more gusts of 65 knots or more
- 10%
- Ten or more severe hail reports
- 5%
- One or more hailstones of 2 inches or more
- 5%
- Six or more combined severe hail and wind reports
- 30%
Warnings issued inside it
17 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 17, 6:42 PM EDT | Tornado Warning | GSP | Polk, Rutherford | 48 min |
| Aug 17, 6:46 PM EDT | Tornado Warning | GSP | Cherokee, Spartanburg | 44 min |
| Aug 17, 6:51 PM EDT | Tornado Warning | GSP | Laurens, Spartanburg, Union | 39 min |
| Aug 17, 6:57 PM EDT | Flash Flood Warning | GSP | Burke, McDowell | 6 hr |
| Aug 17, 7:13 PM EDT | Flash Flood Warning | RNK | Watauga | 8 hr |
| Aug 17, 7:59 PM EDT | Tornado Warning | GSP | Cleveland | 46 min |
| Aug 17, 8:00 PM EDT | Tornado Warning | GSP | Cherokee, Spartanburg, Union, York | 45 min |
| Aug 17, 8:43 PM EDT | Tornado Warning | CAE | Lexington, Saluda | 32 min |
| Aug 17, 9:57 PM EDT | Flash Flood Warning | RNK | Ashe, Wilkes | 5 hr |
| Aug 17, 10:21 PM EDT | Flash Flood Warning | GSP | Catawba | 3 hr |
| Aug 17, 10:44 PM EDT | Tornado Warning | GSP | Alexander, Iredell | 31 min |
| Aug 17, 10:47 PM EDT | Tornado Warning | RNK | Surry, Wilkes, Yadkin | 28 min |
| Aug 17, 11:45 PM EDT | Flash Flood Warning | CAE | Lexington, Richland | 2 hr |
| Aug 18, 12:08 AM EDT | Tornado Warning | RNK | Surry | 37 min |
| Aug 18, 12:24 AM EDT | Tornado Warning | RNK | Surry | 21 min |
| Aug 18, 1:01 AM EDT | Tornado Warning | RNK | Surry | 29 min |
| Aug 18, 2:10 AM EDT | Flash Flood Warning | RNK | Alleghany, Surry | 5 hr |
Discussions around it
SPC mesoscale discussions over the same counties from four hours before the watch to its end.
The nearest sounding before it
Greensboro/Hi Pt, NC (KGSO), launched 12:00Z, 10.5 hours before the alert went out and 126 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
- 522 J/kg
- Mixed-layer CIN
- -5 J/kg
- Mixed-layer LCL
- 593 m above ground
- 0-6 km bulk shear
- 26 kt
- 0-1 km storm-relative helicity
- 77 m²/s²
- 0-3 km storm-relative helicity
- 99 m²/s²
- Significant tornado parameter
- 0.1
- Supercell composite
- 0.9
The text
As transmitted.
607 WWUS20 KWNS 172223 SEL6 SPC WW 172223 NCZ000-SCZ000-VAZ000-180600- URGENT - IMMEDIATE BROADCAST REQUESTED Tornado Watch Number 446 NWS Storm Prediction Center Norman OK 625 PM EDT Tue Aug 17 2021 The NWS Storm Prediction Center has issued a * Tornado Watch for portions of Western North Carolina Parts of central and Upstate South Carolina Southwestern Virginia * Effective this Tuesday night and Wednesday morning from 625 PM until 200 AM EDT. * Primary threats include... A few tornadoes likely Isolated damaging wind gusts to 60 mph possible SUMMARY...Broken bands of supercells will likely persist on the east side of the remnants of tropical cyclone Fred as it moves north-northeastward through tonight. A several tornadoes can be expected, along with isolated wind damage in the strongest storms. The tornado watch area is approximately along and 85 statute miles north and south of a line from 60 miles south southeast of Dublin VA to 20 miles southwest of Spartanburg SC. For a complete depiction of the watch see the associated watch outline update (WOUS64 KWNS WOU6). PRECAUTIONARY/PREPAREDNESS ACTIONS... REMEMBER...A Tornado Watch means conditions are favorable for tornadoes and 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. && OTHER WATCH INFORMATION...This tornado watch replaces tornado watch number 444...tornado watch number 445. Watch number 444 445 will not be in effect after 625 PM EDT. AVIATION...Tornadoes and a few severe thunderstorms with hail surface and aloft to 0.5 inches. Extreme turbulence and surface wind gusts to 50 knots. A few cumulonimbi with maximum tops to 500. Mean storm motion vector 20025. ...Thompson
SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 17, 10:42 AM EDT | Tornado Watch | SPC | Alexander, Avery, Buncombe, Burke, Cabarrus, Caldwell and 20 more | 8 hr |
| Aug 17, 12:35 PM EDT | Mesoscale Discussion | SPC | Alexander, Cabarrus, Catawba, Cleveland, Davie, Forsyth and 9 more | 85 min |
| Aug 17, 1:06 PM EDT | Tornado Watch | SPC | Alleghany, Ashe, Rockingham, Stokes, Surry, Watauga and 2 more | 5 hr |
| Aug 17, 3:25 PM EDT | Mesoscale Discussion | SPC | Buncombe, Burke, Cleveland, Gaston, Henderson, Lincoln and 4 more | 2 hr |
| Aug 17, 5:55 PM EDT | Mesoscale Discussion | SPC | Alexander, Alleghany, Ashe, Avery, Buncombe, Burke and 28 more | 65 min |
| Aug 17, 8:22 AM EDT | Mesoscale Discussion | SPC | Abbeville, Anderson, Edgefield, Greenwood, McCormick | 113 min |
Nearby
Tornado Watches in North Carolina, 2021Tornado Watches in Virginia, 2021Tornado Watches in South Carolina, 2021Every tornado 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.