Alert archive / Virginia / Tornado Watches in 2021
Tornado Watch 445
The Storm Prediction Center issued this tornado watch at Aug 17, 2021, 1:06 PM EDT for 8 counties in North Carolina; 13 counties in Virginia. It was in force for 5 hr.
The area
The outline as issued.
The facts
- Issued
- Aug 17, 2021, 1:06 PM EDT (17:06 UTC)
- Expired
- Aug 17, 2021, 6:31 PM EDT
- In force
- 5 hr
- Issued by
- the Storm Prediction Center
- Largest hail expected
- 0.5 in
- Strongest gust expected
- 60 kt
All 21 counties
Alleghany County, NC, Ashe County, NC, Rockingham County, NC, Stokes County, NC, Surry County, NC, Watauga County, NC, Wilkes County, NC, Yadkin County, NC, Carroll County, VA, City of Galax, VA, City of Martinsville, VA, City of Radford, VA, Floyd County, VA, Franklin County, VA, Grayson County, VA, Henry County, VA, Montgomery County, VA, Patrick County, VA, Pulaski County, VA, Smyth County, VA, Wythe County, VA
The radar
The Roanoke radar (KFCX), 67 km from the middle of the area, began a volume at 17:08 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
- 40%
- 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
6 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 17, 1:19 PM EDT | Tornado Warning | RNK | Wilkes | 41 min |
| Aug 17, 1:48 PM EDT | Tornado Warning | RNK | Alleghany, Wilkes | 42 min |
| Aug 17, 2:43 PM EDT | Tornado Warning | RNK | Rockingham, Stokes | 32 min |
| Aug 17, 3:17 PM EDT | Tornado Warning | RNK | Franklin, Henry, Patrick | 28 min |
| Aug 17, 3:18 PM EDT | Tornado Warning | RNK | Franklin, Henry, City of Martinsville | 27 min |
| Aug 17, 3:41 PM EDT | Tornado Warning | RNK | Franklin, Henry, Patrick | 34 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
Greensboro/Hi Pt, NC (KGSO), launched 12:00Z, 5.1 hours before the alert went out and 111 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.
644 WWUS20 KWNS 171702 SEL5 SPC WW 171702 NCZ000-VAZ000-172300- URGENT - IMMEDIATE BROADCAST REQUESTED Tornado Watch Number 445 NWS Storm Prediction Center Norman OK 105 PM EDT Tue Aug 17 2021 The NWS Storm Prediction Center has issued a * Tornado Watch for portions of Northwest North Carolina Southwest Virginia * Effective this Tuesday afternoon and evening from 105 PM until 700 PM EDT. * Primary threats include... A couple tornadoes possible Isolated damaging wind gusts to 70 mph possible SUMMARY...Isolated thunderstorms may continue to occasionally producing brief tornadoes as they track northward across the watch area this afternoon. The tornado watch area is approximately along and 30 statute miles north and south of a line from 105 miles west northwest of Greensboro NC to 30 miles north northeast of Greensboro NC. For a complete depiction of the watch see the associated watch outline update (WOUS64 KWNS WOU5). 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...CONTINUE...WW 444... AVIATION...Tornadoes and a few severe thunderstorms with hail surface and aloft to 0.5 inches. Extreme turbulence and surface wind gusts to 60 knots. A few cumulonimbi with maximum tops to 500. Mean storm motion vector 17025. ...Hart
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, 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, 6:28 PM EDT | Tornado Watch | SPC | Alexander, Alleghany, Ashe, Avery, Buncombe, Burke and 24 more | 10 hr |
Nearby
Tornado Watches in Virginia, 2021Tornado Watches in North 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.