Alert archive / Minnesota / Mesoscale Discussions in 2021

Mesoscale Discussion 1759

September 16, 202131 counties in Minnesota; Burnett County, Douglas County, Wisconsin

The Storm Prediction Center issued this mesoscale discussion at Sep 16, 2021, 3:47 PM CDT for 31 counties in Minnesota; Burnett County, Douglas County, Wisconsin. It was in force for 118 min.

The area

The outline as issued.

The facts

Issued: Sep 16, 2021, 3:47 PM CDT (20:47 UTC)
Expired: Sep 16, 2021, 5:45 PM CDT
In force: 118 min
Issued by: the Storm Prediction Center
Concerning: Severe potential...watch likely
Chance of a watch: 80%

All 33 counties

Aitkin County, MN, Anoka County, MN, Benton County, MN, Carlton County, MN, Carver County, MN, Cass County, MN, Chippewa County, MN, Chisago County, MN, Crow Wing County, MN, Douglas County, MN, Hennepin County, MN, Isanti County, MN, Itasca County, MN, Kanabec County, MN, Kandiyohi County, MN, Koochiching County, MN, Lake County, MN, McLeod County, MN, Meeker County, MN, Mille Lacs County, MN, Morrison County, MN, Pine County, MN, Pope County, MN, Renville County, MN, Saint Louis County, MN, Sherburne County, MN, Stearns County, MN, Swift County, MN, Todd County, MN, Wadena County, MN, Wright County, MN, Burnett County, WI, Douglas County, WI

The radar

The Duluth radar (KDLH), 93 km from the middle of the area, began a volume at 20:49 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.

The nearest sounding before it

Minneapolis, MN (KMPX), launched 12:00Z, 8.8 hours before the alert went out and 194 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: 1213 m above ground
0-6 km bulk shear: 36 kt
0-1 km storm-relative helicity: 362 m²/s²
0-3 km storm-relative helicity: 428 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 3.0

Open this sounding in Storm Lab

The text

As transmitted.

878 
ACUS11 KWNS 162047
SWOMCD
SPC MCD 162047 
MNZ000-WIZ000-162245-

Mesoscale Discussion 1759
NWS Storm Prediction Center Norman OK
0347 PM CDT Thu Sep 16 2021

Areas affected...northeast and central MN

Concerning...Severe potential...Watch likely 

Valid 162047Z - 162245Z

Probability of Watch Issuance...80 percent

SUMMARY...Severe thunderstorms are expected by 22-23z. Large hail,
damaging gusts and a couple of tornadoes will be possible with this
activity. A watch likely will be needed in the next couple of hours.

DISCUSSION...Stronger heating on the southern edge of thicker
stratus across central MN has resulted in temperatures warming into
the mid 80s to near 90 F amid low/mid 60s F dewpoints. Modified
forecast soundings for current observations show inhibition has
nearly eroded across this region. Visible satellite imagery further
indicates inhibition has rapidly eroded as CU field across the area
has become more agitated with vertical development over the past
hour or so. While CAMs guidance suggest convective initiation may
not occur until closer to 00z, observational trends suggest storms
could develop sooner.  

Steep midlevel lapse rates atop a moist boundary layer are aiding in
generally 1000-2000 J/kg MLCAPE across the warm sector ahead of a
east/southeast moving cold front. Strong vertical shear already is
in place, with effective shear magnitudes around 35-50 kt. This
parameter space will support initial supercells, though deep-layer
southwesterly flow parallel to the surface front could result in
evolution of a messy storm mode with time via outflow interactions.
Large hail (especially with discrete convection), damaging gusts and
a tornado or two are possible through this evening.

..Leitman/Hart.. 09/16/2021

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

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

LAT...LON   45459261 44999326 44719390 44589449 44639516 44779565
            45059594 45409594 45929565 46979496 48109402 48569335
            48649299 48689236 48599163 48349126 48099100 47749091
            47479106 46209199 45459261

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Sep 16, 5:57 PM CDT	Tornado Watch	SPC	Aitkin, Carlton, Crow Wing, Kanabec, Lake, Mille Lacs and 4 more	4 hr
Sep 16, 6:23 PM CDT	Mesoscale Discussion	SPC	Chippewa, Cottonwood, Jackson, Kandiyohi, Lac qui Parle, Lincoln and 13 more	97 min
Sep 16, 6:39 PM CDT	Severe Thunderstorm Watch	SPC	Benton, Brown, Chippewa, Cottonwood, Isanti, Kandiyohi and 14 more	4 hr

Nearby

Mesoscale Discussions in Minnesota, 2021 Mesoscale Discussions in Wisconsin, 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.