Alert archive / Virginia / Tornado Watches in 2021
Tornado Watch 481
The Storm Prediction Center issued this tornado watch at Sep 1, 2021, 12:56 AM EDT for 10 counties in Maryland; 12 counties in Virginia. It was in force for 6 hr.
The area
The outline as issued.
The facts
- Issued
- Sep 1, 2021, 12:56 AM EDT (04:56 UTC)
- Expired
- Sep 1, 2021, 6:52 AM EDT
- In force
- 6 hr
- Issued by
- the Storm Prediction Center
- Strongest gust expected
- 60 kt
All 22 counties
Anne Arundel County, MD, Baltimore County, MD, Carroll County, MD, Charles County, MD, City of Baltimore, MD, Frederick County, MD, Harford County, MD, Howard County, MD, Montgomery County, MD, Prince George's County, MD, Arlington County, VA, City of Alexandria, VA, City of Fairfax, VA, City of Falls Church, VA, City of Fredericksburg, VA, City of Manassas, VA, City of Manassas Park, VA, Fairfax County, VA, Fauquier County, VA, Loudoun County, VA, Prince William County, VA, Stafford County, VA
The radar
The Sterling radar (KLWX), 17 km from the middle of the area, began a volume at 04:56 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
8 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Sep 1, 1:09 AM EDT | Severe Thunderstorm Warning | LWX | Culpeper, Fauquier, Orange | 51 min |
| Sep 1, 1:42 AM EDT | Severe Thunderstorm Warning | LWX | Fauquier | 35 min |
| Sep 1, 2:34 AM EDT | Severe Thunderstorm Warning | LWX | Fairfax, City of Fairfax | 41 min |
| Sep 1, 2:59 AM EDT | Severe Thunderstorm Warning | LWX | Arlington, Fairfax, City of Alexandria, City of Fairfax, City of Falls Church | 46 min |
| Sep 1, 3:01 AM EDT | Flash Flood Warning | LWX | Fairfax, Prince William, City of Manassas Park | 2 hr |
| Sep 1, 3:24 AM EDT | Severe Thunderstorm Warning | LWX | Montgomery, Prince George's | 51 min |
| Sep 1, 4:00 AM EDT | Severe Thunderstorm Warning | LWX | Anne Arundel, Prince George's | 60 min |
| Sep 1, 4:50 AM EDT | Severe Thunderstorm Warning | LWX | Anne Arundel, Baltimore, City of Baltimore | 40 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
Washington/Dulle, VA (KIAD), launched 00:00Z, 4.9 hours before the alert went out and 11 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
- 723 J/kg
- Mixed-layer CIN
- -24 J/kg
- Mixed-layer LCL
- 969 m above ground
- 0-6 km bulk shear
- 32 kt
- 0-1 km storm-relative helicity
- 96 m²/s²
- 0-3 km storm-relative helicity
- 171 m²/s²
- Significant tornado parameter
- 0.3
- Supercell composite
- 2.7
The text
As transmitted.
480 WWUS20 KWNS 010452 SEL1 SPC WW 010452 DCZ000-MDZ000-VAZ000-CWZ000-011200- URGENT - IMMEDIATE BROADCAST REQUESTED Tornado Watch Number 481 NWS Storm Prediction Center Norman OK 1255 AM EDT Wed Sep 1 2021 The NWS Storm Prediction Center has issued a * Tornado Watch for portions of District Of Columbia Central and northern Maryland Northeastern Virginia Coastal Waters * Effective this Wednesday morning from 1255 AM until 800 AM EDT. * Primary threats include... A couple tornadoes possible Isolated damaging wind gusts to 70 mph possible SUMMARY...A potentially tornadic supercell on the fringes of Ida's remnants will exit tornado watch 480 in the next 1-2 hours and is moving generally toward the DC metro. Other convection also may develop and become supercellular overnight, along a frontal zone draped across the watch area. The tornado watch area is approximately along and 30 statute miles either side of a line from 50 miles west southwest of Washington DC to 30 miles northeast of Baltimore MD. For a complete depiction of the watch see the associated watch outline update (WOUS64 KWNS WOU1). 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 480... AVIATION...Tornadoes and a few severe thunderstorms with hail surface and aloft to 0 inches. Extreme turbulence and surface wind gusts to 60 knots. A few cumulonimbi with maximum tops to 500. Mean storm motion vector 23035. ...Edwards
SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Sep 1, 12:19 AM EDT | Mesoscale Discussion | SPC | Anne Arundel, Calvert, Charles, Montgomery, Prince George's | 86 min |
| Sep 1, 4:01 AM EDT | Mesoscale Discussion | SPC | Anne Arundel, Baltimore, Carroll, Cecil, Harford, Howard and 4 more | 119 min |
| Sep 1, 11:03 AM EDT | Mesoscale Discussion | SPC | Anne Arundel, Baltimore, Calvert, Caroline, Carroll, Cecil and 14 more | 2 hr |
| Sep 1, 11:46 AM EDT | Tornado Watch | SPC | Anne Arundel, Baltimore, Calvert, Carroll, Cecil, Charles and 11 more | 9 hr |
| Sep 1, 12:40 PM EDT | Tornado Watch | SPC | Caroline, Kent, Queen Anne's, Talbot | 9 hr |
| Sep 1, 1:32 PM EDT | Mesoscale Discussion | SPC | Anne Arundel, Baltimore, Calvert, Carroll, Cecil, Charles and 9 more | 118 min |
| Sep 1, 3:09 PM EDT | Mesoscale Discussion | SPC | Caroline, Cecil, Dorchester, Harford, Kent, Queen Anne's and 2 more | 3 hr |
| Aug 31, 11:01 PM EDT | Mesoscale Discussion | SPC | Albemarle, Amherst, Augusta, Bath, Botetourt, Culpeper and 15 more | 89 min |
Nearby
Tornado Watches in Virginia, 2021Tornado Watches in Maryland, 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.