Alert archive / Iowa / Mesoscale Discussions in 2021
Mesoscale Discussion 986
The Storm Prediction Center issued this mesoscale discussion at Jun 16, 2021, 9:34 PM CDT for 19 counties in Iowa. It was in force for 116 min.
The area
The outline as issued.
The facts
- Issued
- Jun 16, 2021, 9:34 PM CDT (02:34 UTC)
- Expired
- Jun 16, 2021, 11:30 PM CDT
- In force
- 116 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch possible
- Chance of a watch
- 40%
Counties Adair County, IA, Adams County, IA, Audubon County, IA, Buena Vista County, IA, Calhoun County, IA, Carroll County, IA, Cass County, IA, Crawford County, IA, Dallas County, IA, Greene County, IA, Guthrie County, IA, Harrison County, IA, Ida County, IA, Mills County, IA, Montgomery County, IA, Pottawattamie County, IA, Sac County, IA, Shelby County, IA, Union County, IA
The radar
The Omaha radar (KOAX), 114 km from the middle of the area, began a volume at 02:34 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 00:00Z, 2.6 hours before the alert went out and 114 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
- 2997 J/kg
- Mixed-layer CIN
- -144 J/kg
- Mixed-layer LCL
- 1946 m above ground
- 0-6 km bulk shear
- 40 kt
- 0-1 km storm-relative helicity
- 120 m²/s²
- 0-3 km storm-relative helicity
- 435 m²/s²
- Significant tornado parameter
- 0.1
- Supercell composite
- 27.9
The text
As transmitted.
762
ACUS11 KWNS 170235
SWOMCD
SPC MCD 170234
IAZ000-170430-
Mesoscale Discussion 0986
NWS Storm Prediction Center Norman OK
0934 PM CDT Wed Jun 16 2021
Areas affected...Western IA
Concerning...Severe potential...Watch possible
Valid 170234Z - 170430Z
Probability of Watch Issuance...40 percent
SUMMARY...Isolated large hail and damaging wind gusts are possible
within the ongoing convective line as it continues southward across
western Iowa.
DISCUSSION...Ongoing convective line over northwestern IA has shown
an increase in forward motion over the past half hour, with recent
storm motion estimates now at 40 kt. Nocturnal destabilization is
well underway downstream of this storm, but the organized character
of this line coupled with persistent moist inflow via an increasing
low-level jet and steep mid-level lapse rates should allow it to
maintain intensity for at least the next hour or two. Large hail and
damaging wind gusts are possible within the stronger updrafts.
Given its current motion, the line will likely be south/east of the
main low-level jet axis in a few hours. This displacement coupled
with strong low-level stabilization, casts doubt into its
maintenance past about two hours. Even so, trends will be monitored
for organization/strengthening closely over the next few hours.
..Mosier/Guyer.. 06/17/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...DMX...FSD...OAX...
LAT...LON 41809593 42719574 42779478 41749399 40989419 40899558
41809593SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jun 16, 10:05 PM CDT | Severe Thunderstorm Watch | SPC | Adair, Adams, Audubon, Cass, Clarke, Dallas and 11 more | 4 hr |
| Jun 16, 11:49 PM CDT | Mesoscale Discussion | SPC | Adair, Adams, Audubon, Cass, Clarke, Dallas and 9 more | 86 min |
| Jun 17, 2:57 PM CDT | Mesoscale Discussion | SPC | Allamakee, Black Hawk, Bremer, Buchanan, Butler, Cerro Gordo and 17 more | 63 min |
| Jun 17, 3:50 PM CDT | Severe Thunderstorm Watch | SPC | Allamakee, Black Hawk, Bremer, Butler, Cerro Gordo, Chickasaw and 15 more | 6 hr |
Nearby
Mesoscale Discussions in Iowa, 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.