Alert archive / Iowa / Mesoscale Discussions in 2021

Mesoscale Discussion 1065

June 22, 202142 counties in Iowa; 22 counties in Nebraska

The Storm Prediction Center issued this mesoscale discussion at Jun 22, 2021, 6:51 PM CDT for 42 counties in Iowa; 22 counties in Nebraska. It was in force for 54 min.

The area

The outline as issued.

The facts

Issued: Jun 22, 2021, 6:51 PM CDT (23:51 UTC)
Expired: Jun 22, 2021, 7:45 PM CDT
In force: 54 min
Issued by: the Storm Prediction Center
Concerning: Severe thunderstorm watch 305

All 64 counties

Adair County, IA, Adams County, IA, Appanoose County, IA, Audubon County, IA, Boone County, IA, Calhoun County, IA, Carroll County, IA, Cass County, IA, Clarke County, IA, Crawford County, IA, Dallas County, IA, Decatur County, IA, Greene County, IA, Guthrie County, IA, Hamilton County, IA, Harrison County, IA, Ida County, IA, Jasper County, IA, Lucas County, IA, Madison County, IA, Mahaska County, IA, Marion County, IA, Marshall County, IA, Mills County, IA, Monona County, IA, Monroe County, IA, Montgomery County, IA, Page County, IA, Polk County, IA, Pottawattamie County, IA, Poweshiek County, IA, Ringgold County, IA, Sac County, IA, Shelby County, IA, Story County, IA, Taylor County, IA, Union County, IA, Wapello County, IA, Warren County, IA, Wayne County, IA, Webster County, IA, Woodbury County, IA, Antelope County, NE, Boone County, NE, Burt County, NE, Butler County, NE, Colfax County, NE, Cuming County, NE, Dakota County, NE, Dixon County, NE, Dodge County, NE, Douglas County, NE, Madison County, NE, Nance County, NE, Pierce County, NE, Platte County, NE, Polk County, NE, Sarpy County, NE, Saunders County, NE, Stanton County, NE, Thurston County, NE, Washington County, NE, Wayne County, NE, Wheeler County, NE

The radar

The Omaha radar (KOAX), 102 km from the middle of the area, began a volume at 23:54 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

Omaha, NE (KOAX), launched 12:00Z, 11.9 hours before the alert went out and 102 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.

Skew-T log-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.

Mixed-layer CAPE: 1 J/kg
Mixed-layer CIN: No buoyant parcel
Mixed-layer LCL: 1910 m above ground
0-6 km bulk shear: 59 kt
0-1 km storm-relative helicity: 259 m²/s²
0-3 km storm-relative helicity: 324 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

602 
ACUS11 KWNS 222352
SWOMCD
SPC MCD 222351 
IAZ000-NEZ000-SDZ000-230045-

Mesoscale Discussion 1065
NWS Storm Prediction Center Norman OK
0651 PM CDT Tue Jun 22 2021

Areas affected...eastern Nebraska into western and central Iowa

Concerning...Severe Thunderstorm Watch 305...

Valid 222351Z - 230045Z

The severe weather threat for Severe Thunderstorm Watch 305
continues.

SUMMARY...Hail and damaging wind gusts will remain likely with the
stronger storms across WW305 and the vicinity over the next couple
of hours. Storm coverage and intensity should begin to decrease
close to sunset.

DISCUSSION...Several supercells ongoing across WW305 and surrounding
areas have produced numerous severe hail and isolated wind reports
over the last 90 minutes. SPC mesoanalysis indicates the strongest
storms are ongoing in a narrow axis of 500-1500 J/kg of MLCAPE
stretching from northeast Nebraska into central Iowa. 45-55 kt
effective shear values from the OAX VWP suggest the storm mode will
likely remain supercellular as storms track southeast over the next
2-3 hours. Given the favorable storm mode and available instability,
severe hail and damaging wind gusts will remain likely.

Approaching sunset, storms across eastern Nebraska and western Iowa
will approach a much drier airmass near the Omaha metro. Deep mixing
has resulted in substantially lower surface dewpoints across this
region, severely degrading available buoyancy. As storms approach
this region, a decrease in severe weather probabilities appears
likely. A similar scenario is expected to unfold farther east across
central Iowa as storms approach the eastern edge of the instability
axis coincident with the loss of diurnal heating. Updraft strength
should gradually diminish as nocturnal inhibition increases and
storms move into a more hostile environment north of a stationary
front.

..Lyons.. 06/22/2021

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...DVN...DMX...FSD...OAX...GID...LBF...

LAT...LON   41059726 41299830 41979857 42439768 42659673 42689592
            42589396 42149283 41659239 41419222 40999217 40639258
            40629382 40719505 40969618 41059726

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jun 22, 3:41 PM CDT	Mesoscale Discussion	SPC	Adair, Adams, Audubon, Boone, Buena Vista, Calhoun and 34 more	2 hr
Jun 22, 4:49 PM CDT	Severe Thunderstorm Watch	SPC	Adair, Audubon, Carroll, Cass, Crawford, Greene and 4 more	4 hr

Nearby

Mesoscale Discussions in Iowa, 2021 Mesoscale Discussions in Nebraska, 2021 Every 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.