Alert archive / South Dakota / Mesoscale Discussions in 2021

Mesoscale Discussion 315

April 5, 20214 states

The Storm Prediction Center issued this mesoscale discussion at Apr 5, 2021, 6:21 PM CDT for 4 states. It was in force for 114 min.

The area

The outline as issued.

The facts

Issued: Apr 5, 2021, 6:21 PM CDT (23:21 UTC)
Expired: Apr 5, 2021, 8:15 PM CDT
In force: 114 min
Issued by: the Storm Prediction Center
Concerning: Severe potential...watch unlikely
Chance of a watch: 20%

All 27 counties

Lyon County, IA, Sioux County, IA, Brown County, MN, Cottonwood County, MN, Lincoln County, MN, Lyon County, MN, Murray County, MN, Nobles County, MN, Pipestone County, MN, Redwood County, MN, Rock County, MN, Antelope County, NE, Cedar County, NE, Dixon County, NE, Holt County, NE, Knox County, NE, Pierce County, NE, Bon Homme County, SD, Clay County, SD, Hutchinson County, SD, Lincoln County, SD, McCook County, SD, Minnehaha County, SD, Moody County, SD, Turner County, SD, Union County, SD, Yankton County, SD

The radar

The Sioux Falls radar (KFSD), 53 km from the middle of the area, began a volume at 23:23 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, 11.4 hours before the alert went out and 210 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: 2662 m above ground
0-6 km bulk shear: 38 kt
0-1 km storm-relative helicity: 194 m²/s²
0-3 km storm-relative helicity: 190 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

167 
ACUS11 KWNS 052321
SWOMCD
SPC MCD 052321 
MNZ000-IAZ000-SDZ000-NEZ000-060115-

Mesoscale Discussion 0315
NWS Storm Prediction Center Norman OK
0621 PM CDT Mon Apr 05 2021

Areas affected...Southwestern MN to northeast NE

Concerning...Severe potential...Watch unlikely 

Valid 052321Z - 060115Z

Probability of Watch Issuance...20 percent

SUMMARY...Gusty winds, along with some potential for hail, are
expected with convection this evening. Severe thunderstorm watch is
not currently anticipated.

DISCUSSION...Strong boundary-layer heating has contributed to steep
surface-3km lapse rates from north-central NE to southwestern MN. As
a result, it appears parcels have reached their convective
temperatures and weak convergence along the front is now aiding
deeper updrafts along this corridor. Over the last half hour,
updrafts have gradually strengthened, and may continue to do so, as
this activity encounters somewhat higher moisture content just
downstream. With the primary large-scale forcing for ascent expected
to remain north of these storms, organizational potential may be
limited, and a severe thunderstorm watch is not currently
anticipated. Even so, isolated severe wind gusts may be noted with
these storms given the relatively low sub-cloud RH and steep lapse
rates. Some hail may also occur.

..Darrow/Thompson.. 04/05/2021

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

ATTN...WFO...MPX...FSD...OAX...LBF...

LAT...LON   42179911 43769741 45039532 44289451 41989751 42179911

Nearby

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