Alert archive / Iowa / Mesoscale Discussions in 2021
Mesoscale Discussion 921
The Storm Prediction Center issued this mesoscale discussion at Jun 11, 2021, 9:35 AM CDT for 25 counties in Iowa; 14 counties in Minnesota. It was in force for 115 min.
The area
The outline as issued.
The facts
- Issued
- Jun 11, 2021, 9:35 AM CDT (14:35 UTC)
- Expired
- Jun 11, 2021, 11:30 AM CDT
- In force
- 115 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch unlikely
- Chance of a watch
- 5%
All 39 counties
Boone County, IA, Bremer County, IA, Butler County, IA, Calhoun County, IA, Cerro Gordo County, IA, Chickasaw County, IA, Emmet County, IA, Floyd County, IA, Franklin County, IA, Greene County, IA, Grundy County, IA, Hamilton County, IA, Hancock County, IA, Hardin County, IA, Howard County, IA, Humboldt County, IA, Kossuth County, IA, Mitchell County, IA, Palo Alto County, IA, Pocahontas County, IA, Webster County, IA, Winnebago County, IA, Winneshiek County, IA, Worth County, IA, Wright County, IA, Blue Earth County, MN, Dodge County, MN, Faribault County, MN, Fillmore County, MN, Freeborn County, MN, Le Sueur County, MN, Martin County, MN, Mower County, MN, Nicollet County, MN, Olmsted County, MN, Rice County, MN, Steele County, MN, Waseca County, MN, Watonwan County, MN
The radar
The Des Moines radar (KDMX), 168 km from the middle of the area, began a volume at 14:36 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 12:00Z, 2.6 hours before the alert went out and 181 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.
- Mixed-layer CAPE
- 752 J/kg
- Mixed-layer CIN
- -207 J/kg
- Mixed-layer LCL
- 1602 m above ground
- 0-6 km bulk shear
- 19 kt
- 0-1 km storm-relative helicity
- -28 m²/s²
- 0-3 km storm-relative helicity
- -40 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
656
ACUS11 KWNS 111435
SWOMCD
SPC MCD 111435
IAZ000-MNZ000-111630-
Mesoscale Discussion 0921
NWS Storm Prediction Center Norman OK
0935 AM CDT Fri Jun 11 2021
Areas affected...Portions of south-central and southeast Minnesota
into north-central and northeast Iowa
Concerning...Severe potential...Watch unlikely
Valid 111435Z - 111630Z
Probability of Watch Issuance...5 percent
SUMMARY...A couple damaging gusts and perhaps a couple severe
hailstones may occur with the stronger storm cores. The relatively
low coverage and brevity of the severe threat precludes a WW
issuance.
DISCUSSION...Convective outflow/potential gravity wave, remnant from
the decaying portion of an MCS, continues to progress eastward
across central and eastern Minnesota to the Iowa border this
morning. Over the past few hours, this outflow feature has triggered
sporadic convective development despite 50-100 J/kg MLCINH in place,
though the lifespan of individual cells has been short owing to weak
deep-layer flow and associated vertical shear. Despite the weak
shear and MLCINH present, storms have been initiating within a
marginally unstable environment characterized by up to 1000 J/kg
given 7+ C/km mid-level lapse rates atop near 70 F surface
dewpoints.
Some of these short-lived storms have managed to produce measured
45-50 kt gusts within the past hour, and additional damaging gusts
remain possible through the morning/early afternoon hours as the
propagating outflow continues to lift buoyant parcels above the
boundary layer. Given the modest mid-level lapse rates in place, a
couple severe hailstones cannot be completely ruled out for any cell
that manages to obtain any longevity. Still, the severe threat is
expected to be isolated and brief given the short cellular
lifespans, and a WW issuance is not expected.
..Squitieri/Grams.. 06/11/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...ARX...MPX...DMX...
LAT...LON 42059461 42899487 43999468 44379445 44469364 44469283
44239242 43839213 43429175 42939202 42469270 42149320
41919411 42059461SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jun 11, 5:36 AM CDT | Severe Thunderstorm Watch | SPC | Harrison, Monona, Pottawattamie, Shelby | 5 hr |
| Jun 11, 7:28 AM CDT | Mesoscale Discussion | SPC | Harrison, Mills, Monona, Pottawattamie | 92 min |
| Jun 11, 8:30 AM CDT | Severe Thunderstorm Watch | SPC | Fremont, Mills, Montgomery, Page | 7 hr |
| Jun 11, 1:58 AM CDT | Severe Thunderstorm Watch | SPC | Clay, Norman, Polk, Wilkin | 5 hr |
| Jun 11, 2:15 AM CDT | Severe Thunderstorm Watch | SPC | Big Stone, Traverse | 5 hr |
| Jun 11, 4:37 AM CDT | Mesoscale Discussion | SPC | Big Stone, Clay, Grant, Kittson, Lac qui Parle, Marshall and 6 more | 83 min |
| Jun 11, 11:34 AM CDT | Mesoscale Discussion | SPC | Dakota, Dodge, Fillmore, Goodhue, Houston, Olmsted and 3 more | 116 min |
Nearby
Mesoscale Discussions in Iowa, 2021Mesoscale 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.