Alert archive / North Dakota / Severe Thunderstorm Watches in 2021

Severe Thunderstorm Watch 476

August 30, 202112 counties in North Dakota

The Storm Prediction Center issued this severe thunderstorm watch at Aug 30, 2021, 12:38 PM MDT for 12 counties in North Dakota. It was in force for 5 hr.

The area

The outline as issued.

The facts

Issued
Aug 30, 2021, 12:38 PM MDT (18:38 UTC)
Expired
Aug 30, 2021, 5:56 PM MDT
In force
5 hr
Issued by
the Storm Prediction Center
Largest hail expected
2.5 in
Strongest gust expected
60 kt

Counties Adams County, ND, Burleigh County, ND, Dunn County, ND, Emmons County, ND, Grant County, ND, Hettinger County, ND, McLean County, ND, Mercer County, ND, Morton County, ND, Oliver County, ND, Sioux County, ND, Stark County, ND

The radar

The Bismarck radar (KBIS), 40 km from the middle of the area, began a volume at 18:39 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
20%
One or more EF2 to EF5 tornadoes
5%
Ten or more severe wind reports
20%
One or more gusts of 65 knots or more
20%
Ten or more severe hail reports
40%
One or more hailstones of 2 inches or more
40%
Six or more combined severe hail and wind reports
60%

Warnings issued inside it

16 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.

IssuedProductOfficeCountiesLasted
Aug 30, 12:42 PM MDTSevere Thunderstorm Warning Considerable damage threatBISMorton, Oliver63 min
Aug 30, 12:44 PM MDTSevere Thunderstorm WarningBISMercer, Oliver61 min
Aug 30, 1:17 PM MDTSevere Thunderstorm Warning Destructive damage threatBISMorton58 min
Aug 30, 2:15 PM MDTSevere Thunderstorm Warning Considerable damage threatBISMorton60 min
Aug 30, 2:48 PM MDTSevere Thunderstorm WarningBISMcLean42 min
Aug 30, 3:16 PM MDTSevere Thunderstorm Warning Considerable damage threatBISMorton59 min
Aug 30, 3:32 PM MDTSevere Thunderstorm WarningBISHettinger58 min
Aug 30, 3:43 PM MDTSevere Thunderstorm WarningBISGrant, Morton47 min
Aug 30, 4:00 PM MDTSevere Thunderstorm Warning Considerable damage threatBISGrant, Morton60 min
Aug 30, 4:28 PM MDTSevere Thunderstorm WarningBISMercer, Oliver47 min
Aug 30, 4:29 PM MDTSevere Thunderstorm Warning Destructive damage threatBISAdams, Hettinger61 min
Aug 30, 4:43 PM MDTSevere Thunderstorm WarningBISMcLean, Mercer47 min
Aug 30, 4:54 PM MDTSevere Thunderstorm WarningBISGrant, Morton38 min
Aug 30, 5:02 PM MDTSevere Thunderstorm Warning Destructive damage threatBISGrant, Morton, Sioux58 min
Aug 30, 5:30 PM MDTSevere Thunderstorm Warning Considerable damage threatBISAdams60 min
Aug 30, 5:49 PM MDTSevere Thunderstorm WarningBISEmmons, Grant, Morton, Sioux35 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

Bismarck Municip, ND (KBIS), launched 12:00Z, 6.6 hours before the alert went out and 43 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.

Skew-T log-pSkew-T log-p diagram, Bismarck Municip, ND at 12:00Z on 2021-08-30Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 8 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Bismarck Municip, ND at 12:00Z on 2021-08-30The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 93 square meters per square second.193958Sfc1 km3 km6 km9 kmRMLM
The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.
Mixed-layer CAPE
8 J/kg
Mixed-layer CIN
-262 J/kg
Mixed-layer LCL
1949 m above ground
0-6 km bulk shear
39 kt
0-1 km storm-relative helicity
93 m²/s²
0-3 km storm-relative helicity
131 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

The text

As transmitted.

407 
WWUS20 KWNS 301807
SEL6  
SPC WW 301807
NDZ000-310000-

URGENT - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Watch Number 476
NWS Storm Prediction Center Norman OK
110 PM CDT Mon Aug 30 2021

The NWS Storm Prediction Center has issued a

* Severe Thunderstorm Watch for portions of 
  South-central North Dakota

* Effective this Monday afternoon and evening from 110 PM until
  700 PM CDT.

* Primary threats include...
  Scattered large hail and isolated very large hail events to 2.5
    inches in diameter possible
  Isolated damaging wind gusts to 70 mph possible
  A tornado or two possible

SUMMARY...A couple of slow-moving supercells have developed and may
persist along a baroclinic zone. The primary hazard should be large
hail, but a tornado or two is possible as well.

The severe thunderstorm watch area is approximately along and 40
statute miles east and west of a line from 5 miles northeast of
Garrison ND to 55 miles south southwest of Bismarck ND. For a
complete depiction of the watch see the associated watch outline
update (WOUS64 KWNS WOU6).

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.

&&

OTHER WATCH INFORMATION...CONTINUE...WW 475...

AVIATION...A few severe thunderstorms with hail surface and aloft to
2.5 inches. Extreme turbulence and surface wind gusts to 60 knots. A
few cumulonimbi with maximum tops to 550. Mean storm motion vector
34010.

...Grams

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Aug 30, 1:54 PM MDTMesoscale DiscussionSPCAdams, Dunn, Emmons, Grant, Hettinger, McLean and 5 more2 hr
Aug 30, 4:58 PM MDTMesoscale DiscussionSPCAdams, Dunn, Emmons, Grant, Hettinger, Mercer and 4 more62 min
Aug 30, 5:56 PM MDTSevere Thunderstorm WatchSPCAdams, Burleigh, Dunn, Emmons, Grant, Hettinger and 6 more3 hr

Nearby

Severe Thunderstorm Watches in North Dakota, 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.