Alert archive / Iowa / Mesoscale Discussions in 2021
Mesoscale Discussion 1615
The Storm Prediction Center issued this mesoscale discussion at Aug 26, 2021, 10:45 PM CDT for 4 states. It was in force for 2 hr.
The area
The outline as issued.
The facts
- Issued
- Aug 26, 2021, 10:45 PM CDT (03:45 UTC)
- Expired
- Aug 27, 2021, 12:45 AM CDT
- In force
- 2 hr
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch possible
- Chance of a watch
- 40%
All 49 counties
Bremer County, IA, Buena Vista County, IA, Butler County, IA, Calhoun County, IA, Cerro Gordo County, IA, Cherokee County, IA, Chickasaw County, IA, Clay County, IA, Dickinson County, IA, Emmet County, IA, Floyd County, IA, Franklin County, IA, Hancock County, IA, Howard County, IA, Humboldt County, IA, Ida County, IA, Kossuth County, IA, Lyon County, IA, Mitchell County, IA, O'Brien County, IA, Osceola County, IA, Palo Alto County, IA, Plymouth County, IA, Pocahontas County, IA, Sac County, IA, Sioux County, IA, Webster County, IA, Winnebago County, IA, Woodbury County, IA, Worth County, IA, Wright County, IA, Blue Earth County, MN, Cottonwood County, MN, Dodge County, MN, Faribault County, MN, Fillmore County, MN, Freeborn County, MN, Jackson County, MN, Martin County, MN, Mower County, MN, Murray County, MN, Nobles County, MN, Pipestone County, MN, Rock County, MN, Steele County, MN, Waseca County, MN, Watonwan County, MN, Dakota County, NE, Union County, SD
The radar
The Minneapolis radar (KMPX), 184 km from the middle of the area, began a volume at 03:48 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 00:00Z, 3.8 hours before the alert went out and 183 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
- 0 J/kg
- Mixed-layer CIN
- No buoyant parcel
- Mixed-layer LCL
- 792 m above ground
- 0-6 km bulk shear
- 49 kt
- 0-1 km storm-relative helicity
- 393 m²/s²
- 0-3 km storm-relative helicity
- 392 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.1
The text
As transmitted.
022
ACUS11 KWNS 270346
SWOMCD
SPC MCD 270345
IAZ000-MNZ000-NEZ000-SDZ000-270545-
Mesoscale Discussion 1615
NWS Storm Prediction Center Norman OK
1045 PM CDT Thu Aug 26 2021
Areas affected...portions of southern MN and northern IA
Concerning...Severe potential...Watch possible
Valid 270345Z - 270545Z
Probability of Watch Issuance...40 percent
SUMMARY...Strong to isolated severe thunderstorms producing locally
strong gusts and hail are possible into the early overnight period
across parts of southern MN into northern IA.
DISCUSSION...Isolated to scattered convection has developed across
far southern MN into far northern IA late this evening. This
activity is to the north of a west-to-east oriented stationary
surface boundary extending across northern IA. This activity has
intensified recently as warm advection increases across the region
as a southerly low level jet has strengthened over the mid-MO valley
vicinity. Strong inhibition exists, especially north of the
boundary, but moderate instability amid steep midlevel lapse rates
and effective shear greater than 35 kt is aiding in organized
clusters. Hail and locally strong gusts could accompany this
activity into the early overnight period. However, the elevated
nature of convection may temper the overall severe threat as
convection shifts northeast into a somewhat less favorable
environment. While a severe thunderstorm watch does not appear
imminent at this time, convective trends are being monitored, both
with activity across northern IA as well as further west across
northeast NE/southeast SD. If better organized clusters develop, a
watch could become necessary.
..Leitman/Bunting.. 08/27/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...ARX...MPX...DMX...FSD...OAX...
LAT...LON 44159610 44259541 44179345 44029257 43759202 43259193
42779202 42539265 42339426 42219599 42169667 42689678
44069644 44159610SPC 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 27, 1:53 PM CDT | Mesoscale Discussion | SPC | Black Hawk, Bremer, Butler, Calhoun, Cerro Gordo, Chickasaw and 18 more | 97 min |
| Aug 27, 4:01 PM CDT | Mesoscale Discussion | SPC | Allamakee, Black Hawk, Bremer, Butler, Calhoun, Cerro Gordo and 20 more | 59 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 |
| Aug 26, 7:25 PM CDT | Mesoscale Discussion | SPC | Boyd, Brown, Cherry, Holt, Keya Paha, Rock | 2 hr |
| Aug 27, 3:55 PM CDT | Mesoscale Discussion | SPC | Butte, Harding, Perkins | 2 hr |
| Aug 27, 6:33 PM CDT | Mesoscale Discussion | SPC | Butte, Perkins, Ziebach | 117 min |
Nearby
Mesoscale Discussions in Iowa, 2021Mesoscale Discussions in Minnesota, 2021Mesoscale Discussions in Nebraska, 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.