Alert archive / Iowa / Mesoscale Discussions in 2021
Mesoscale Discussion 1281
The Storm Prediction Center issued this mesoscale discussion at Jul 14, 2021, 1:40 PM CDT for 44 counties in Iowa; Burt County, Washington County, Nebraska. It was in force for 2 hr.
The area
The outline as issued.
The facts
- Issued
- Jul 14, 2021, 1:40 PM CDT (18:40 UTC)
- Expired
- Jul 14, 2021, 3:45 PM CDT
- In force
- 2 hr
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch likely
- Chance of a watch
- 95%
All 46 counties
Audubon County, IA, Black Hawk County, IA, Boone County, IA, Bremer County, IA, Buena Vista County, IA, Butler County, IA, Calhoun County, IA, Carroll County, IA, Cerro Gordo County, IA, Cherokee County, IA, Chickasaw County, IA, Clay County, IA, Crawford County, IA, Dallas County, IA, Emmet County, IA, Fayette County, IA, Floyd County, IA, Franklin County, IA, Greene County, IA, Grundy County, IA, Guthrie County, IA, Hamilton County, IA, Hancock County, IA, Hardin County, IA, Harrison County, IA, Howard County, IA, Humboldt County, IA, Ida County, IA, Kossuth County, IA, Marshall County, IA, Mitchell County, IA, Monona County, IA, Palo Alto County, IA, Pocahontas County, IA, Pottawattamie County, IA, Sac County, IA, Shelby County, IA, Story County, IA, Tama County, IA, Webster County, IA, Winnebago County, IA, Woodbury County, IA, Worth County, IA, Wright County, IA, Burt County, NE, Washington County, NE
The radar
The Des Moines radar (KDMX), 83 km from the middle of the area, began a volume at 18:41 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
Omaha, NE (KOAX), launched 12:00Z, 6.7 hours before the alert went out and 212 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
- 967 J/kg
- Mixed-layer CIN
- -125 J/kg
- Mixed-layer LCL
- 1201 m above ground
- 0-6 km bulk shear
- 43 kt
- 0-1 km storm-relative helicity
- 35 m²/s²
- 0-3 km storm-relative helicity
- -7 m²/s²
- Significant tornado parameter
- -0.0
- Supercell composite
- -0.1
The text
As transmitted.
506
ACUS11 KWNS 141840
SWOMCD
SPC MCD 141840
IAZ000-MNZ000-NEZ000-142045-
Mesoscale Discussion 1281
NWS Storm Prediction Center Norman OK
0140 PM CDT Wed Jul 14 2021
Areas affected...much of Iowa...far eastern Nebraska
Concerning...Severe potential...Watch likely
Valid 141840Z - 142045Z
Probability of Watch Issuance...95 percent
SUMMARY...Storms are expected to develop by 21Z from the
Nebraska/Iowa border across northwest Iowa, with supercell potential
spreading east/northeast across Iowa and perhaps extreme southern
Minnesota this evening. A few tornadoes will be possible, along with
damaging gusts and hail.
DISCUSSION...A diffuse warm front currently extends from northeast
NE across central IA, with outflow-cooled air from northeast IA into
southwest WI. The outflow farther west across north-central IA has
modified somewhat with dewpoints holding near 70 F along with backed
surface winds.
Southerly winds are currently gusting to over 20 kt across the MO
Valley, with area of heating across western IA and NE. Continued
destabilization is therefore likely across these areas, and this is
also where surface convergence is focused along the low pressure
trough. Farther to the northwest, a secondary from extends from
southwest MN into northern NE, and low-topped convection has been
noted over far northwest IA.
Lift will continue to consolidate over western IA over the next few
hours, where instability and shear parameters will also maximize. A
downstream zone of supercell potential will exist in association
with the warm front/outflow with enhanced low-level shear and low
LCLs. A few tornadoes will be possible, as well as large hail.
Damaging wind potential may increase should more of a linear storm
mode materialize a few hours after initiation.
..Jewell/Bunting.. 07/14/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...DVN...ARX...MPX...DMX...FSD...OAX...
LAT...LON 41329506 41289585 41399618 41609637 41999651 42339640
42929574 43439459 43669304 43479232 43279197 43079187
42779175 42179196 41949301 41329506SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jul 14, 7:02 AM CDT | Mesoscale Discussion | SPC | Allamakee, Benton, Black Hawk, Boone, Bremer, Buchanan and 43 more | 2 hr |
| Jul 14, 8:54 AM CDT | Severe Thunderstorm Watch | SPC | Allamakee, Black Hawk, Bremer, Buchanan, Butler, Cerro Gordo and 13 more | 5 hr |
| Jul 14, 11:45 AM CDT | Mesoscale Discussion | SPC | Allamakee, Clayton, Dubuque, Jackson, Jones | 2 hr |
| Jul 14, 2:35 PM CDT | Tornado Watch | SPC | Audubon, Benton, Black Hawk, Boone, Bremer, Buchanan and 41 more | 8 hr |
| Jul 14, 4:17 PM CDT | Mesoscale Discussion | SPC | Boone, Butler, Calhoun, Franklin, Greene, Grundy and 5 more | 58 min |
| Jul 14, 5:42 PM CDT | Mesoscale Discussion | SPC | Allamakee, Clayton, Delaware, Dubuque, Jackson, Jones | 63 min |
| Jul 14, 5:47 PM CDT | Mesoscale Discussion | SPC | Audubon, Benton, Black Hawk, Boone, Bremer, Buchanan and 29 more | 118 min |
| Jul 14, 6:13 PM CDT | Tornado Watch | SPC | Allamakee, Cedar, Clayton, Clinton, Delaware, Dubuque and 7 more | 6 hr |
| Jul 13, 11:30 PM CDT | Mesoscale Discussion | SPC | Banner, Box Butte, Cheyenne, Dawes, Garden, Grant and 4 more | 90 min |
Nearby
Mesoscale Discussions in Iowa, 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.