Alert archive / South Dakota / Mesoscale Discussions in 2021

Mesoscale Discussion 698

May 21, 20214 counties in South Dakota

The Storm Prediction Center issued this mesoscale discussion at May 21, 2021, 9:04 PM MDT for 4 counties in South Dakota. It was in force for 86 min.

The area

The outline as issued.

The facts

Issued
May 21, 2021, 9:04 PM MDT (03:04 UTC)
Expired
May 21, 2021, 10:30 PM MDT
In force
86 min
Issued by
the Storm Prediction Center
Concerning
Severe thunderstorm watch 192

Counties Fall River County, SD, Haakon County, SD, Jackson County, SD, Oglala Lakota County, SD

The radar

The Rapid City radar (KUDX), 54 km from the middle of the area, began a volume at 03:06 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, 3.1 hours before the alert went out and 51 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, Rapid City, SD at 00:00Z on 2021-05-22Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 0 joules per kilogram.LCL10008507005003002001001 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, Rapid City, SD at 00:00Z on 2021-05-22The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 450 square meters per square second.19395878Sfc1 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
0 J/kg
Mixed-layer CIN
No buoyant parcel
Mixed-layer LCL
579 m above ground
0-6 km bulk shear
62 kt
0-1 km storm-relative helicity
450 m²/s²
0-3 km storm-relative helicity
741 m²/s²
Significant tornado parameter
0.0
Supercell composite
5.4

Open this sounding in Storm Lab

The text

As transmitted.

286 
ACUS11 KWNS 220305
SWOMCD
SPC MCD 220304 
SDZ000-NEZ000-220430-

Mesoscale Discussion 0698
NWS Storm Prediction Center Norman OK
1004 PM CDT Fri May 21 2021

Areas affected...Northwestern Nebraska/Western South Dakota

Concerning...Severe Thunderstorm Watch 192...

Valid 220304Z - 220430Z

The severe weather threat for Severe Thunderstorm Watch 192
continues.

SUMMARY...Large hail remains possible with the strongest convection,
especially from northwestern Nebraska into southwestern South
Dakota.

DISCUSSION...Surface front has crept south across the central High
Plains this evening with the leading edge of this notable density
current now stretching from Stanley County SD-Sheridan County
NE-just south of CYS. Over the last hour or so, the strongest
convection appears to be along the cool side of the boundary. With
LLJ expected to increase across NE into south-central SD, this trend
may continue, though near-surface based thunderstorms may also
develop along the frontal zone. Large hail, possible in excess of 1
inch at times, may occur with the strongest updrafts.

..Darrow.. 05/22/2021

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

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

LAT...LON   42950400 45190142 44680074 42730233 42950400

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
May 21, 6:30 PM MDTMesoscale DiscussionSPCBennett, Oglala Lakota, Todd90 min

Nearby

Mesoscale Discussions in South Dakota, 2021Every 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.