Alert archive / South Dakota / Mesoscale Discussions in 2021

Mesoscale Discussion 1815

October 9, 20216 counties in South Dakota

The Storm Prediction Center issued this mesoscale discussion at Oct 9, 2021, 4:50 PM MDT for 6 counties in South Dakota. It was in force for 55 min.

The area

The outline as issued.

The facts

Issued: Oct 9, 2021, 4:50 PM MDT (22:50 UTC)
Expired: Oct 9, 2021, 5:45 PM MDT
In force: 55 min
Issued by: the Storm Prediction Center
Concerning: Severe potential...watch unlikely
Chance of a watch: 5%

Counties Haakon County, SD, Jackson County, SD, Jones County, SD, Mellette County, SD, Stanley County, SD, Todd County, SD

The radar

The Rapid City radar (KUDX), 133 km from the middle of the area, began a volume at 22:51 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, 10.8 hours before the alert went out and 136 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: 63 J/kg
Mixed-layer CIN: -169 J/kg
Mixed-layer LCL: 747 m above ground
0-6 km bulk shear: 38 kt
0-1 km storm-relative helicity: 106 m²/s²
0-3 km storm-relative helicity: 187 m²/s²
Significant tornado parameter: -0.0
Supercell composite: -0.0

Open this sounding in Storm Lab

The text

As transmitted.

927 
ACUS11 KWNS 092250
SWOMCD
SPC MCD 092250 
SDZ000-092345-

Mesoscale Discussion 1815
NWS Storm Prediction Center Norman OK
0550 PM CDT Sat Oct 09 2021

Areas affected...Portions of southwest and south-central South
Dakota

Concerning...Severe potential...Watch unlikely 

Valid 092250Z - 092345Z

Probability of Watch Issuance...5 percent

SUMMARY...Hail and gusty thunderstorm winds possible with strongest
thunderstorms. A watch is not expected.

DISCUSSION...Cold temperatures aloft associated with the core of an
upper low moving into the northern Plains this evening resulted in
most-unstable CAPE values greater than 1000 J/kg developing across
southwest and south-central South Dakota, where an axis of surface
temperatures into the mid 70s exists. Thunderstorms in this area
pose a threat for strong, gusty thunderstorm winds and hail. The
threat should diminish as the storms move east out of the better
instability axis and as diurnal heating wanes.

A watch is not expected.

..Marsh/Bunting.. 10/09/2021

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

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

LAT...LON   43810206 44560179 44860105 44610044 43990019 43460021
            43180054 43240162 43520200 43810206

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Oct 9, 11:04 AM MDT	Mesoscale Discussion	SPC	Aurora, Beadle, Brookings, Brule, Buffalo, Clark and 14 more	2 hr
Oct 9, 1:56 PM MDT	Severe Thunderstorm Watch	SPC	Aurora, Beadle, Brookings, Brown, Brule, Buffalo and 18 more	7 hr
Oct 9, 2:40 PM MDT	Mesoscale Discussion	SPC	Beadle, Clark, Codington, Deuel, Hamlin, Kingsbury	95 min
Oct 9, 5:00 PM MDT	Mesoscale Discussion	SPC	Codington, Deuel, Grant, Roberts	90 min

Nearby

Mesoscale Discussions in South 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.