Alert archive / Iowa / Mesoscale Discussions in 2017

Mesoscale Discussion 1369

July 20, 201714 counties in Iowa

The Storm Prediction Center issued this mesoscale discussion at Jul 20, 2017, 3:57 PM CDT for 14 counties in Iowa. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued: Jul 20, 2017, 3:57 PM CDT (20:57 UTC)
Expired: Jul 20, 2017, 6:00 PM CDT
In force: 2 hr
Issued by: the Storm Prediction Center
Chance of a watch: 20%

Counties Boone County, IA, Calhoun County, IA, Carroll County, IA, Crawford County, IA, Greene County, IA, Hamilton County, IA, Hardin County, IA, Ida County, IA, Marshall County, IA, Monona County, IA, Sac County, IA, Story County, IA, Webster County, IA, Woodbury County, IA

The radar

The Des Moines radar (KDMX), 89 km from the middle of the area, began a volume at 20:57 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 12:00Z, 9.0 hours before the alert went out and 316 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: 58 J/kg
Mixed-layer CIN: -429 J/kg
Mixed-layer LCL: 1266 m above ground
0-6 km bulk shear: 46 kt
0-1 km storm-relative helicity: -176 m²/s²
0-3 km storm-relative helicity: -172 m²/s²
Significant tornado parameter: 0.0
Supercell composite: -0.1

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
Jul 19, 7:06 PM CDT	Mesoscale Discussion	SPC	Lyon, Plymouth, Sioux, Woodbury	84 min
Jul 19, 8:19 PM CDT	Mesoscale Discussion	SPC	Allamakee, Cedar, Clayton, Clinton, Delaware, Dubuque and 3 more	86 min
Jul 20, 1:16 AM CDT	Mesoscale Discussion	SPC	Benton, Black Hawk, Bremer, Buchanan, Butler, Cerro Gordo and 20 more	119 min

Nearby

Mesoscale Discussions in Iowa, 2017 Every mesoscale discussion in 2017

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.