Alert archive / South Dakota / Mesoscale Discussions in 2021

Mesoscale Discussion 1329

July 22, 20214 counties in North Dakota; 6 counties in South Dakota

The Storm Prediction Center issued this mesoscale discussion at Jul 22, 2021, 4:42 PM MDT for 4 counties in North Dakota; 6 counties in South Dakota. It was in force for 3 hr.

The area

The outline as issued.

The facts

Issued: Jul 22, 2021, 4:42 PM MDT (22:42 UTC)
Expired: Jul 22, 2021, 7:15 PM MDT
In force: 3 hr
Issued by: the Storm Prediction Center
Concerning: Severe potential...watch unlikely
Chance of a watch: 20%

Counties Adams County, ND, Grant County, ND, Hettinger County, ND, Sioux County, ND, Butte County, SD, Corson County, SD, Lawrence County, SD, Meade County, SD, Perkins County, SD, Ziebach County, SD

The radar

The Rapid City radar (KUDX), 127 km from the middle of the area, began a volume at 22:41 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.

The nearest sounding before it

Rapid City, SD (KUNR), launched 12:00Z, 10.7 hours before the alert went out and 134 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-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

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: 578 J/kg
Mixed-layer CIN: -149 J/kg
Mixed-layer LCL: 2111 m above ground
0-6 km bulk shear: 12 kt
0-1 km storm-relative helicity: -5 m²/s²
0-3 km storm-relative helicity: 50 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

277 
ACUS11 KWNS 222242
SWOMCD
SPC MCD 222242 
NDZ000-SDZ000-WYZ000-230115-

Mesoscale Discussion 1329
NWS Storm Prediction Center Norman OK
0542 PM CDT Thu Jul 22 2021

Areas affected...southwest North Dakota into western South Dakota

Concerning...Severe potential...Watch unlikely 

Valid 222242Z - 230115Z

Probability of Watch Issuance...20 percent

SUMMARY...Isolated severe gusts remain possible this evening, mainly
through 01 or 02Z. Coverage of severe is not expected to warrant a
watch.

DISCUSSION...A broken line of storms producing strong to severe wind
gusts and sporadic/marginal hail continues to propagate east across
the western Dakotas. Hot temperatures over 100 F exist ahead of this
line with a deep mixed layer. While large-scale support is weak
beneath the upper ridge, the heated air mass, 55-60 F dewpoints, and
deep-layer shear near 30 kt support isolated severe gust potential
as late as 02Z. Thereafter, CIN will increase and there will be
little nocturnal low-level jet, suggesting the threat will end. The
latest CAMs also support this scenario, with diurnal storms ending
between 01-02Z.

..Jewell/Edwards.. 07/22/2021

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...ABR...BIS...UNR...

LAT...LON   44150406 44880374 45390344 45810324 46210307 46730237
            46690148 46430086 46080048 45360071 44620164 44230233
            43990288 44010373 44150406

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jul 22, 2:24 PM MDT	Mesoscale Discussion	SPC	Billings, Bowman, Dunn, Golden Valley, McKenzie, Slope and 1 more	2 hr

Nearby

Mesoscale Discussions in South Dakota, 2021 Mesoscale Discussions in North Dakota, 2021 Every mesoscale discussion 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.