Alert archive / Iowa / Mesoscale Discussions in 2018

Mesoscale Discussion 1406

September 1, 20185 states

The Storm Prediction Center issued this mesoscale discussion at Sep 1, 2018, 6:34 PM CDT for 5 states. It was in force for 56 min.

The area

The outline as issued.

The facts

Issued: Sep 1, 2018, 6:34 PM CDT (23:34 UTC)
Expired: Sep 1, 2018, 7:30 PM CDT
In force: 56 min
Issued by: the Storm Prediction Center
Chance of a watch: 40%

All 95 counties

Adair County, IA, Adams County, IA, Appanoose County, IA, Audubon County, IA, Benton County, IA, Black Hawk County, IA, Boone County, IA, Bremer County, IA, Buchanan County, IA, Butler County, IA, Calhoun County, IA, Carroll County, IA, Cass County, IA, Cedar County, IA, Chickasaw County, IA, Clarke County, IA, Clayton County, IA, Clinton County, IA, Crawford County, IA, Dallas County, IA, Davis County, IA, Decatur County, IA, Delaware County, IA, Des Moines County, IA, Dubuque County, IA, Fayette County, IA, Franklin County, IA, Fremont County, IA, Greene County, IA, Grundy County, IA, Guthrie County, IA, Hamilton County, IA, Hardin County, IA, Harrison County, IA, Henry County, IA, Iowa County, IA, Jackson County, IA, Jasper County, IA, Jefferson County, IA, Johnson County, IA, Jones County, IA, Keokuk County, IA, Linn County, IA, Louisa 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, Muscatine County, IA, Page County, IA, Polk County, IA, Pottawattamie County, IA, Poweshiek County, IA, Ringgold County, IA, Sac County, IA, Scott County, IA, Shelby County, IA, Story County, IA, Tama County, IA, Taylor County, IA, Union County, IA, Van Buren County, IA, Wapello County, IA, Warren County, IA, Washington County, IA, Wayne County, IA, Webster County, IA, Wright County, IA, Carroll County, IL, Henderson County, IL, Henry County, IL, Jo Daviess County, IL, Mercer County, IL, Rock Island County, IL, Warren County, IL, Whiteside County, IL, Atchison County, MO, Gentry County, MO, Harrison County, MO, Mercer County, MO, Nodaway County, MO, Putnam County, MO, Schuyler County, MO, Worth County, MO, Burt County, NE, Cass County, NE, Douglas County, NE, Sarpy County, NE, Washington County, NE, Grant County, WI

The radar

The Des Moines radar (KDMX), 74 km from the middle of the area, began a volume at 23:34 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.

Severe Thunderstorm Watch 364Sep 1, 8:20 PM CDT

The nearest sounding before it

Omaha, NE (KOAX), launched 12:00Z, 11.6 hours before the alert went out and 296 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: 162 J/kg
Mixed-layer CIN: -379 J/kg
Mixed-layer LCL: 1980 m above ground
0-6 km bulk shear: 53 kt
0-1 km storm-relative helicity: -269 m²/s²
0-3 km storm-relative helicity: -188 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
Aug 31, 8:47 PM CDT	Mesoscale Discussion	SPC	Adair, Adams, Appanoose, Audubon, Carroll, Cass and 24 more	118 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 Illinois, 2018 Mesoscale Discussions in Missouri, 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.