Alert archive / South Dakota / Mesoscale Discussions in 2021

Mesoscale Discussion 1814

October 9, 20216 counties in South Dakota

The Storm Prediction Center issued this mesoscale discussion at Oct 9, 2021, 3:40 PM CDT for 6 counties in South Dakota. It was in force for 95 min.

The area

The outline as issued.

The facts

Issued: Oct 9, 2021, 3:40 PM CDT (20:40 UTC)
Expired: Oct 9, 2021, 5:15 PM CDT
In force: 95 min
Issued by: the Storm Prediction Center
Concerning: Severe thunderstorm watch 514

Counties Beadle County, SD, Clark County, SD, Codington County, SD, Deuel County, SD, Hamlin County, SD, Kingsbury County, SD

The radar

The Aberdeen radar (KABR), 114 km from the middle of the area, began a volume at 20:45 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

Aberdeen, SD (KABR), launched 12:00Z, 8.7 hours before the alert went out and 63 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: 4 J/kg
Mixed-layer CIN: -89 J/kg
Mixed-layer LCL: 713 m above ground
0-6 km bulk shear: 37 kt
0-1 km storm-relative helicity: 97 m²/s²
0-3 km storm-relative helicity: 200 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.1

Open this sounding in Storm Lab

The text

As transmitted.

269 
ACUS11 KWNS 092041
SWOMCD
SPC MCD 092040 
SDZ000-092215-

Mesoscale Discussion 1814
NWS Storm Prediction Center Norman OK
0340 PM CDT Sat Oct 09 2021

Areas affected...Parts of east central/northeastern South Dakota

Concerning...Severe Thunderstorm Watch 514...

Valid 092040Z - 092215Z

The severe weather threat for Severe Thunderstorm Watch 514
continues.

SUMMARY...More rapid intensification of thunderstorms is probable
through 4-6 PM CDT.  This may include the evolution of one or two
supercells gradually posing increasing potential to produce
tornadoes, along a narrow corridor initially near or south of Huron
into the Brookings/Watertown vicinity.

DISCUSSION...Within a broader developing cluster of thunderstorms,
strongest convection is currently focused near/northwest of Huron. 
This is near a slowly deepening lower/mid tropospheric cyclone, just
to the north of a developing surface low now centered to the west
northwest of Yankton.  20Z surface observations indicate 3-4 mb
2-hourly surface pressure falls across much of southeastern South
Dakota, as far north as the Huron and Brookings vicinities, which is
now just south of where lower/mid tropospheric warm advection has
become maximized.  

With the warm sector boundary layer becoming characterized by CAPE
up to 1500 J/kg, in the presence of strong deep-layer shear,
substantive further thunderstorm intensification seems likely
through 22-00Z.  This probably will include the evolution of
supercell structures, particularly near the southern flank of the
evolving convective system, with low-level hodographs gradually
enlarging and becoming more conducive to the risk for a tornado or
two.

..Kerr/Hart.. 10/09/2021

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

ATTN...WFO...FSD...ABR...

LAT...LON   44849848 45179739 44979647 44279686 44159755 44049805
            44039859 44419840 44849848

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Oct 9, 12:04 PM CDT	Mesoscale Discussion	SPC	Aurora, Beadle, Brookings, Brule, Buffalo, Clark and 14 more	2 hr
Oct 9, 2:56 PM CDT	Severe Thunderstorm Watch	SPC	Aurora, Beadle, Brookings, Brown, Brule, Buffalo and 18 more	7 hr
Oct 9, 5:50 PM CDT	Mesoscale Discussion	SPC	Haakon, Jackson, Jones, Mellette, Stanley, Todd	55 min
Oct 9, 6:00 PM CDT	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.