Alert archive / South Dakota / Mesoscale Discussions in 2021

Mesoscale Discussion 1301

July 16, 2021Dawes County, Nebraska; Bennett County, Fall River County, Oglala Lakota County, South Dakota

The Storm Prediction Center issued this mesoscale discussion at Jul 16, 2021, 6:16 PM MDT for Dawes County, Nebraska; Bennett County, Fall River County, Oglala Lakota County, South Dakota. It was in force for 89 min.

The area

The outline as issued.

The facts

Issued: Jul 16, 2021, 6:16 PM MDT (00:16 UTC)
Expired: Jul 16, 2021, 7:45 PM MDT
In force: 89 min
Issued by: the Storm Prediction Center
Concerning: Severe thunderstorm watch 381

Counties Dawes County, NE, Bennett County, SD, Fall River County, SD, Oglala Lakota County, SD

The radar

The Rapid City radar (KUDX), 106 km from the middle of the area, began a volume at 00:15 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 00:00Z, 0.3 hours before the alert went out and 100 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: 0 J/kg
Mixed-layer CIN: No buoyant parcel
Mixed-layer LCL: 3551 m above ground
0-6 km bulk shear: 47 kt
0-1 km storm-relative helicity: 73 m²/s²
0-3 km storm-relative helicity: 211 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

723 
ACUS11 KWNS 170017
SWOMCD
SPC MCD 170016 
NEZ000-SDZ000-170145-

Mesoscale Discussion 1301
NWS Storm Prediction Center Norman OK
0716 PM CDT Fri Jul 16 2021

Areas affected...Southwestern SD...Northwestern NE

Concerning...Severe Thunderstorm Watch 381...

Valid 170016Z - 170145Z

The severe weather threat for Severe Thunderstorm Watch 381
continues.

SUMMARY...Severe threat will gradually shift southeast this evening.

DISCUSSION...Scattered convection that initiated over the northern
Black Hills has propagated off the higher terrain and a
well-identifiable outflow boundary has surged ahead of this cluster.
Several storm mergers are now occurring along this boundary over
Oglala Lakota County SD, while new updrafts are developing along the
wind shift between Chadron and Hot Springs. This activity should
continue to grow upscale over the next few hours as it propagates
southeast. With LLJ expected to increase into this region it should
provide some longevity to the expanding complex. Hail and wind
remain possible with this maturing MCS.

..Darrow.. 07/17/2021

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

ATTN...WFO...LBF...UNR...CYS...

LAT...LON   43070395 43420304 44010253 43550137 42690151 42420294
            43070395

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jul 16, 9:17 PM MDT	Mesoscale Discussion	SPC	Arthur, Cherry, Grant, Hooker, McPherson, Thomas	88 min
Jul 17, 2:40 PM MDT	Mesoscale Discussion	SPC	Banner, Box Butte, Cheyenne, Dawes, Deuel, Garden and 5 more	3 hr

Nearby

Mesoscale Discussions in South Dakota, 2021 Mesoscale Discussions in Nebraska, 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.