Alert archive / Iowa / Mesoscale Discussions in 2021

Mesoscale Discussion 1369

July 27, 202111 counties in Iowa; 6 counties in Minnesota; 4 counties in Wisconsin

The Storm Prediction Center issued this mesoscale discussion at Jul 27, 2021, 10:35 PM CDT for 11 counties in Iowa; 6 counties in Minnesota; 4 counties in Wisconsin. It was in force for 55 min.

The area

The outline as issued.

The facts

Issued
Jul 27, 2021, 10:35 PM CDT (03:35 UTC)
Expired
Jul 27, 2021, 11:30 PM CDT
In force
55 min
Issued by
the Storm Prediction Center
Concerning
Severe thunderstorm watch 397
All 21 counties

Allamakee County, IA, Bremer County, IA, Buchanan County, IA, Chickasaw County, IA, Clayton County, IA, Delaware County, IA, Dubuque County, IA, Fayette County, IA, Howard County, IA, Mitchell County, IA, Winneshiek County, IA, Dodge County, MN, Fillmore County, MN, Houston County, MN, Mower County, MN, Olmsted County, MN, Winona County, MN, Crawford County, WI, Grant County, WI, La Crosse County, WI, Vernon County, WI

The radar

The La Crosse radar (KARX), 73 km from the middle of the area, began a volume at 03:37 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

Davenport, (KDVN), launched 00:00Z, 3.6 hours before the alert went out and 217 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, Davenport, at 00:00Z on 2021-07-28Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 1554 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, Davenport, at 00:00Z on 2021-07-28The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 68 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
1554 J/kg
Mixed-layer CIN
-284 J/kg
Mixed-layer LCL
1342 m above ground
0-6 km bulk shear
40 kt
0-1 km storm-relative helicity
68 m²/s²
0-3 km storm-relative helicity
148 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.1

Open this sounding in Storm Lab

The text

As transmitted.

161 
ACUS11 KWNS 280335
SWOMCD
SPC MCD 280335 
ILZ000-WIZ000-IAZ000-MNZ000-280430-

Mesoscale Discussion 1369
NWS Storm Prediction Center Norman OK
1035 PM CDT Tue Jul 27 2021

Areas affected...Southeast MN...southwest WI...northeast IA

Concerning...Severe Thunderstorm Watch 397...

Valid 280335Z - 280430Z

The severe weather threat for Severe Thunderstorm Watch 397
continues.

SUMMARY...The severe risk continues across the remaining valid
portions of the watch area.

DISCUSSION...Regional radar composite imagery shows a broken line of
strong/occasionally severe thunderstorms over extreme southeast MN
east to near La Crosse, WI moving generally south.  Thus far,
marginally severe hail has been reported in Olmsted County, MN, with
wind gusts in the 40-50 mph range.  Recent radar trends suggest the
potential for strong/possibly severe wind gusts may be increasing as
a more elongated reflectivity structure develops and forward motion
increases.  The evolving complex of storms should tend to move
south-southwest along the instability gradient over the next few
hours, and the downstream environment will remain favorable for a
continued severe wind/hail risk with strong instability (MUCAPE in
excess of 4000 J/kg) and 35-40 kts of northwesterly effective shear.

..Bunting.. 07/28/2021

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

ATTN...WFO...DVN...ARX...MPX...DMX...

LAT...LON   43979304 44279231 44269148 44069110 43719080 43499048
            42949047 42559046 42289106 42299181 42479204 43049271
            43259290 43349298 43979304

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Jul 27, 7:33 PM CDTMesoscale DiscussionSPCAllamakee, Black Hawk, Bremer, Buchanan, Butler, Cerro Gordo and 11 more87 min
Jul 27, 8:03 PM CDTSevere Thunderstorm WatchSPCAllamakee, Bremer, Buchanan, Chickasaw, Clayton, Delaware and 7 more6 hr
Jul 28, 12:50 AM CDTMesoscale DiscussionSPCBenton, Buchanan, Clayton, Delaware, Dubuque, Jackson and 2 more55 min
Jul 28, 2:48 AM CDTMesoscale DiscussionSPCBig Stone, Chippewa, Douglas, Grant, Kandiyohi, Lac qui Parle and 12 more2 hr
Jul 28, 10:28 AM CDTMesoscale DiscussionSPCAitkin, Beltrami, Cass, Clearwater, Hubbard, Itasca2 hr
Jul 28, 12:59 PM CDTMesoscale DiscussionSPCKoochiching, Lake, Lake of the Woods, Saint Louis2 hr
Jul 28, 3:32 PM CDTMesoscale DiscussionSPCBeltrami, Clearwater, Lake of the Woods, Mahnomen, Red Lake118 min
Jul 28, 5:09 PM CDTMesoscale DiscussionSPCAitkin, Anoka, Benton, Carlton, Chisago, Crow Wing and 7 more2 hr

Nearby

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