Alert archive / Minnesota / Mesoscale Discussions in 2021

Mesoscale Discussion 1571

August 20, 202115 counties in Minnesota

The Storm Prediction Center issued this mesoscale discussion at Aug 20, 2021, 8:17 PM CDT for 15 counties in Minnesota. It was in force for 88 min.

The area

The outline as issued.

The facts

Issued
Aug 20, 2021, 8:17 PM CDT (01:17 UTC)
Expired
Aug 20, 2021, 9:45 PM CDT
In force
88 min
Issued by
the Storm Prediction Center
Concerning
Severe thunderstorm watch 451...452

Counties Benton County, MN, Blue Earth County, MN, Carver County, MN, Le Sueur County, MN, McLeod County, MN, Meeker County, MN, Morrison County, MN, Nicollet County, MN, Scott County, MN, Sherburne County, MN, Sibley County, MN, Stearns County, MN, Todd County, MN, Waseca County, MN, Wright County, MN

The radar

The Minneapolis radar (KMPX), 35 km from the middle of the area, began a volume at 01:21 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

Minneapolis, MN (KMPX), launched 00:00Z, 1.3 hours before the alert went out and 33 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, Minneapolis, MN at 00:00Z on 2021-08-21Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 395 joules per kilogram.LCLLFCEL10008507005003002001001 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, Minneapolis, MN at 00:00Z on 2021-08-21The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 233 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
395 J/kg
Mixed-layer CIN
-100 J/kg
Mixed-layer LCL
1368 m above ground
0-6 km bulk shear
24 kt
0-1 km storm-relative helicity
233 m²/s²
0-3 km storm-relative helicity
303 m²/s²
Significant tornado parameter
0.2
Supercell composite
2.4

Open this sounding in Storm Lab

The text

As transmitted.

618 
ACUS11 KWNS 210117
SWOMCD
SPC MCD 210117 
MNZ000-210245-

Mesoscale Discussion 1571
NWS Storm Prediction Center Norman OK
0817 PM CDT Fri Aug 20 2021

Areas affected...Minnesota

Concerning...Severe Thunderstorm Watch 451...452...

Valid 210117Z - 210245Z

The severe weather threat for Severe Thunderstorm Watch 451, 452
continues.

SUMMARY...Convection is expected to weaken across Minnesota this
evening.

DISCUSSION...Despite large-scale upper support, north-south band of
broken convection appears to have peaked in intensity across MN this
evening. This activity has progressed steadily across the eastern
portions of ww451 and ww452, but is now encountering lesser
moisture/buoyancy. Thunderstorms have responded accordingly and are
weakening as they approach a boundary-layer air mass characterized
by lower 60s dew points. There is some reason to believe convection
near the IA border may linger due to higher instability, but this
activity should propagate slowly east with an attendant locally
damaging wind threat.

..Darrow.. 08/21/2021

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

ATTN...WFO...DLH...MPX...

LAT...LON   43869409 46009498 46699420 44489342 43709319 43869409

Nearby

Mesoscale Discussions in Minnesota, 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.