Alert archive / Iowa / Mesoscale Discussions in 2021
Mesoscale Discussion 1592
The Storm Prediction Center issued this mesoscale discussion at Aug 24, 2021, 12:44 PM CDT for 10 counties in Iowa; Houston County, Minnesota; 6 counties in Wisconsin. It was in force for 91 min.
The area
The outline as issued.
The facts
- Issued
- Aug 24, 2021, 12:44 PM CDT (17:44 UTC)
- Expired
- Aug 24, 2021, 2:15 PM CDT
- In force
- 91 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch possible
- Chance of a watch
- 40%
Counties Allamakee County, IA, Bremer County, IA, Butler County, IA, Chickasaw County, IA, Clayton County, IA, Fayette County, IA, Floyd County, IA, Howard County, IA, Mitchell County, IA, Winneshiek County, IA, Houston County, MN, Crawford County, WI, Grant County, WI, Iowa County, WI, Richland County, WI, Sauk County, WI, Vernon County, WI
The radar
The La Crosse radar (KARX), 72 km from the middle of the area, began a volume at 17:46 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
Davenport, (KDVN), launched 12:00Z, 5.7 hours before the alert went out and 191 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
- 1809 J/kg
- Mixed-layer CIN
- -127 J/kg
- Mixed-layer LCL
- 1284 m above ground
- 0-6 km bulk shear
- 15 kt
- 0-1 km storm-relative helicity
- 35 m²/s²
- 0-3 km storm-relative helicity
- 9 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
729
ACUS11 KWNS 241744
SWOMCD
SPC MCD 241744
WIZ000-IAZ000-MNZ000-241915-
Mesoscale Discussion 1592
NWS Storm Prediction Center Norman OK
1244 PM CDT Tue Aug 24 2021
Areas affected...northeast Iowa...extreme southeast Minnesota and
southwest Wisconsin
Concerning...Severe potential...Watch possible
Valid 241744Z - 241915Z
Probability of Watch Issuance...40 percent
SUMMARY...Threat for damaging wind may undergo an increase across
northeast Iowa, southeast Minnesota into southwest Wisconsin this
afternoon. Overall scenario is not particularly high confidence, but
trends are being monitored for a possible severe thunderstorm watch.
DISCUSSION...As of early afternoon a line of storms has recently
undergone some intensification along the southern MN / northern IA
border. These storms are developing on the cool side of an east-west
oriented convective outflow boundary. South of this boundary the
atmosphere is destabilizing with MLCAPE from 2000-2500 J/kg
supported by strong diabatic heating of the moist surface layer.
Theta-e advection from the unstable warm sector may contribute to
further intensification of storms north of the boundary. It also
appears that an MCV or meso-gamma-scale circulation is evident along
the northern end of the line which might help to sustain an
organized linear MCS next few hours despite tendency for slight
warming aloft.
..Dial/Kerr.. 08/24/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...MKX...DVN...ARX...DMX...
LAT...LON 43539274 43769148 43728986 43178960 42698997 42549171
42669328 43539274SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 24, 6:00 AM CDT | Mesoscale Discussion | SPC | Allamakee, Cerro Gordo, Chickasaw, Clayton, Dubuque, Fayette and 6 more | 90 min |
| Aug 24, 1:52 PM CDT | Severe Thunderstorm Watch | SPC | Audubon, Benton, Black Hawk, Boone, Bremer, Buchanan and 36 more | 5 hr |
| Aug 24, 5:10 PM CDT | Mesoscale Discussion | SPC | Benton, Cedar, Clinton, Iowa, Jackson, Jasper and 7 more | 2 hr |
| Aug 24, 1:10 AM CDT | Mesoscale Discussion | SPC | Anoka, Benton, Carver, Chippewa, Dakota, Douglas and 26 more | 95 min |
| Aug 24, 2:17 AM CDT | Severe Thunderstorm Watch | SPC | Anoka, Benton, Big Stone, Brown, Carver, Chippewa and 34 more | 7 hr |
| Aug 24, 3:00 AM CDT | Mesoscale Discussion | SPC | Anoka, Benton, Big Stone, Brown, Carver, Chippewa and 35 more | 2 hr |
| Aug 24, 5:00 AM CDT | Mesoscale Discussion | SPC | Anoka, Carver, Dakota, Hennepin, Kandiyohi, McLeod and 8 more | 90 min |
| Aug 24, 7:10 AM CDT | Mesoscale Discussion | SPC | Blue Earth, Chisago, Dakota, Dodge, Fillmore, Freeborn and 13 more | 95 min |
| Aug 24, 9:13 AM CDT | Mesoscale Discussion | SPC | Brown, Calumet, Menominee, Oconto, Outagamie, Shawano and 3 more | 62 min |
| Aug 24, 3:09 PM CDT | Mesoscale Discussion | SPC | Green, Rock, Walworth | 66 min |
| Aug 24, 3:55 PM CDT | Severe Thunderstorm Watch | SPC | Green, Lafayette, Rock, Walworth | 5 hr |
Nearby
Mesoscale Discussions in Iowa, 2021Mesoscale Discussions in Wisconsin, 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.