Alert archive / Iowa / Mesoscale Discussions in 2018

Mesoscale Discussion 1497

September 25, 201830 counties in Iowa

The Storm Prediction Center issued this mesoscale discussion at Sep 25, 2018, 9:27 AM CDT for 30 counties in Iowa. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued: Sep 25, 2018, 9:27 AM CDT (14:27 UTC)
Expired: Sep 25, 2018, 11:30 AM CDT
In force: 2 hr
Issued by: the Storm Prediction Center
Chance of a watch: 20%

All 30 counties

Adair County, IA, Adams County, IA, Audubon County, IA, Boone County, IA, Carroll County, IA, Cass County, IA, Clarke County, IA, Dallas County, IA, Greene County, IA, Grundy County, IA, Guthrie County, IA, Hardin County, IA, Jasper County, IA, Lucas County, IA, Madison County, IA, Mahaska County, IA, Marion County, IA, Marshall County, IA, Mills County, IA, Montgomery County, IA, Page County, IA, Polk County, IA, Pottawattamie County, IA, Poweshiek County, IA, Shelby County, IA, Story County, IA, Tama County, IA, Taylor County, IA, Union County, IA, Warren County, IA

The radar

The Des Moines radar (KDMX), 52 km from the middle of the area, began a volume at 14:27 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

Davenport, (KDVN), launched 12:00Z, 2.5 hours before the alert went out and 319 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: 47 J/kg
Mixed-layer CIN: -108 J/kg
Mixed-layer LCL: 703 m above ground
0-6 km bulk shear: 41 kt
0-1 km storm-relative helicity: 4 m²/s²
0-3 km storm-relative helicity: 38 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

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SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Sep 25, 1:07 PM CDT	Mesoscale Discussion	SPC	Appanoose, Benton, Buchanan, Cedar, Clayton, Clinton and 23 more	113 min
Sep 25, 1:36 PM CDT	Severe Thunderstorm Watch	SPC	Cedar, Clinton, Des Moines, Dubuque, Henry, Jackson and 5 more	8 hr
Sep 25, 3:39 PM CDT	Mesoscale Discussion	SPC	Cedar, Clinton, Des Moines, Dubuque, Jackson, Jones and 4 more	96 min

Nearby

Mesoscale Discussions in Iowa, 2018 Every mesoscale discussion in 2018

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.