Alert archive / Iowa / Mesoscale Discussions in 2021
Mesoscale Discussion 1619
The Storm Prediction Center issued this mesoscale discussion at Aug 27, 2021, 4:01 PM CDT for 26 counties in Iowa; 7 counties in Minnesota; 5 counties in Wisconsin. It was in force for 59 min.
The area
The outline as issued.
The facts
- Issued
- Aug 27, 2021, 4:01 PM CDT (21:01 UTC)
- Expired
- Aug 27, 2021, 5:00 PM CDT
- In force
- 59 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch possible
- Chance of a watch
- 40%
All 38 counties
Allamakee County, IA, Black Hawk County, IA, Bremer County, IA, Butler County, IA, Calhoun County, IA, Cerro Gordo County, IA, Chickasaw County, IA, Clayton County, IA, Fayette County, IA, Floyd County, IA, Franklin 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, Faribault County, MN, Fillmore County, MN, Freeborn County, MN, Houston County, MN, Mower County, MN, Olmsted County, MN, Winona County, MN, Crawford County, WI, La Crosse County, WI, Monroe County, WI, Richland County, WI, Vernon County, WI
The radar
The Des Moines radar (KDMX), 156 km from the middle of the area, began a volume at 21:03 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, 9.0 hours before the alert went out and 218 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
- 487 J/kg
- Mixed-layer CIN
- -63 J/kg
- Mixed-layer LCL
- 644 m above ground
- 0-6 km bulk shear
- 24 kt
- 0-1 km storm-relative helicity
- -9 m²/s²
- 0-3 km storm-relative helicity
- -16 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
488
ACUS11 KWNS 272102
SWOMCD
SPC MCD 272101
WIZ000-IAZ000-MNZ000-272200-
Mesoscale Discussion 1619
NWS Storm Prediction Center Norman OK
0401 PM CDT Fri Aug 27 2021
Areas affected...Northern Iowa...Southwest Wisconsin...and Southern
Minnesota
Concerning...Severe potential...Watch possible
Valid 272101Z - 272200Z
Probability of Watch Issuance...40 percent
SUMMARY...Intensification and new convective development remain
possible this evening. Area continues to be monitored for possible
watch issuance.
DISCUSSION...Visible satellite continues to show widespread cloud
cover over southern Minnesota into north-central Iowa associated
with ongoing elevated convection. Farther south, a reservoir of
moderate instability (MLCAPE of 3000-3500 J/kg) has developed within
a deeply mixed boundary layer. Despite these conditions, convective
activity has struggled to intensify, perhaps owing to the residual
cloud cover and somewhat modest mid-level lapse rates.
Short-term evolution of the ongoing convection and any new
development remains unclear. Visible satellite shows some signs of
more vigorous updrafts developing over north-central Iowa. Modest
deep-layer shear remains present over the region, which will help to
organize this convection should it become rooted in the boundary
layer, and favorable low-level shear over this region will support a
tornado threat where low-level winds can remain backed, in addition
to a hail/wind threat. This area will continue to be monitored for
possible watch issuance in the next few hours.
..Karstens/Dial.. 08/27/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...MKX...DVN...ARX...MPX...DMX...FSD...
LAT...LON 42299294 42119456 42519533 43659414 44089206 43919015
42929064 42299294SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 26, 8:03 PM CDT | Severe Thunderstorm Watch | SPC | Buena Vista, Cherokee, Clay, Dickinson, Ida, Lyon and 5 more | 7 hr |
| Aug 26, 10:45 PM CDT | Mesoscale Discussion | SPC | Bremer, Buena Vista, Butler, Calhoun, Cerro Gordo, Cherokee and 25 more | 2 hr |
| Aug 27, 1:53 PM CDT | Mesoscale Discussion | SPC | Black Hawk, Bremer, Butler, Calhoun, Cerro Gordo, Chickasaw and 18 more | 97 min |
| Aug 27, 5:15 PM CDT | Tornado Watch | SPC | Allamakee, Bremer, Butler, Cerro Gordo, Chickasaw, Clayton and 12 more | 6 hr |
| Aug 27, 5:30 PM CDT | Mesoscale Discussion | SPC | Allamakee, Cerro Gordo, Chickasaw, Floyd, Howard, Winneshiek | 60 min |
| Aug 27, 6:28 PM CDT | Mesoscale Discussion | SPC | Audubon, Calhoun, Carroll, Crawford, Greene, Guthrie and 6 more | 92 min |
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.