Alert archive / Minnesota / Mesoscale Discussions in 2020

Mesoscale Discussion 1539

August 21, 20208 counties in Minnesota; Deuel County, Grant County, Roberts County, South Dakota

The Storm Prediction Center issued this mesoscale discussion at Aug 21, 2020, 5:02 PM CDT for 8 counties in Minnesota; Deuel County, Grant County, Roberts County, South Dakota. It was in force for 58 min.

The area

The outline as issued.

The facts

Issued: Aug 21, 2020, 5:02 PM CDT (22:02 UTC)
Expired: Aug 21, 2020, 6:00 PM CDT
In force: 58 min
Issued by: the Storm Prediction Center
Concerning: Severe potential...watch unlikely
Chance of a watch: 20%

Counties Big Stone County, MN, Chippewa County, MN, Kandiyohi County, MN, Lac qui Parle County, MN, Redwood County, MN, Stevens County, MN, Swift County, MN, Yellow Medicine County, MN, Deuel County, SD, Grant County, SD, Roberts County, SD

The radar

The Aberdeen radar (KABR), 162 km from the middle of the area, began a volume at 22:04 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 watches that followed

Watches SPC issued over any of the same counties within four hours of this discussion.

Severe Thunderstorm Watch 447Aug 21, 6:20 PM CDT

The nearest sounding before it

Aberdeen, SD (KABR), launched 12:00Z, 10.0 hours before the alert went out and 163 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: 1536 J/kg
Mixed-layer CIN: -277 J/kg
Mixed-layer LCL: 1392 m above ground
0-6 km bulk shear: 15 kt
0-1 km storm-relative helicity: 16 m²/s²
0-3 km storm-relative helicity: 36 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.4

Open this sounding in Storm Lab

The text

As transmitted.

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SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Aug 21, 6:20 PM CDT	Severe Thunderstorm Watch	SPC	Blue Earth, Brown, Carver, Chippewa, Cottonwood, Dakota and 28 more	8 hr

Nearby

Mesoscale Discussions in Minnesota, 2020 Mesoscale Discussions in South Dakota, 2020 Every mesoscale discussion in 2020

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.