Alert archive / Iowa / Mesoscale Discussions in 2018

Mesoscale Discussion 1399

August 31, 201830 counties in Iowa; 18 counties in Missouri; 16 counties in Nebraska

The Storm Prediction Center issued this mesoscale discussion at Aug 31, 2018, 8:47 PM CDT for 30 counties in Iowa; 18 counties in Missouri; 16 counties in Nebraska. It was in force for 118 min.

The area

The outline as issued.

The facts

Issued: Aug 31, 2018, 8:47 PM CDT (01:47 UTC)
Expired: Aug 31, 2018, 10:45 PM CDT
In force: 118 min
Issued by: the Storm Prediction Center
Chance of a watch: 60%

All 64 counties

Adair County, IA, Adams County, IA, Appanoose County, IA, Audubon County, IA, Carroll County, IA, Cass County, IA, Clarke County, IA, Crawford County, IA, Dallas County, IA, Decatur County, IA, Fremont County, IA, Greene County, IA, Guthrie County, IA, Harrison County, IA, Lucas County, IA, Madison County, IA, Marion County, IA, Mills County, IA, Monona County, IA, Monroe County, IA, Montgomery County, IA, Page County, IA, Polk County, IA, Pottawattamie County, IA, Ringgold County, IA, Shelby County, IA, Taylor County, IA, Union County, IA, Warren County, IA, Wayne County, IA, Adair County, MO, Andrew County, MO, Atchison County, MO, Caldwell County, MO, Clinton County, MO, Daviess County, MO, DeKalb County, MO, Gentry County, MO, Grundy County, MO, Harrison County, MO, Holt County, MO, Linn County, MO, Livingston County, MO, Mercer County, MO, Nodaway County, MO, Putnam County, MO, Sullivan County, MO, Worth County, MO, Burt County, NE, Butler County, NE, Cass County, NE, Dodge County, NE, Douglas County, NE, Gage County, NE, Johnson County, NE, Lancaster County, NE, Nemaha County, NE, Otoe County, NE, Richardson County, NE, Saline County, NE, Sarpy County, NE, Saunders County, NE, Seward County, NE, Washington County, NE

The radar

The Des Moines radar (KDMX), 143 km from the middle of the area, began a volume at 01:47 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 00:00Z, 1.8 hours before the alert went out and 149 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: 2615 J/kg
Mixed-layer CIN: -112 J/kg
Mixed-layer LCL: 1197 m above ground
0-6 km bulk shear: 49 kt
0-1 km storm-relative helicity: 186 m²/s²
0-3 km storm-relative helicity: 306 m²/s²
Significant tornado parameter: 2.2
Supercell composite: 24.5

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 1, 6:34 PM CDT	Mesoscale Discussion	SPC	Adair, Adams, Appanoose, Audubon, Benton, Black Hawk and 67 more	56 min
Sep 1, 2:30 AM CDT	Mesoscale Discussion	SPC	Butler, Colfax, Dodge, Hamilton, Merrick, Nance and 3 more	90 min
Sep 1, 2:45 PM CDT	Mesoscale Discussion	SPC	Adams, Franklin, Furnas, Harlan, Kearney, Nuckolls and 2 more	2 hr
Sep 1, 4:47 PM CDT	Severe Thunderstorm Watch	SPC	Cass, Clay, Douglas, Fillmore, Gage, Jefferson and 13 more	6 hr
Sep 1, 5:37 PM CDT	Mesoscale Discussion	SPC	Arthur, Chase, Cheyenne, Deuel, Dundy, Garden and 4 more	113 min
Sep 1, 6:38 PM CDT	Mesoscale Discussion	SPC	Cass, Clay, Douglas, Fillmore, Gage, Jefferson and 12 more	2 hr

Nearby

Mesoscale Discussions in Iowa, 2018 Mesoscale Discussions in Missouri, 2018 Mesoscale Discussions in Nebraska, 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.