Alert archive / Nebraska / Mesoscale Discussions in 2018

Mesoscale Discussion 1483

September 20, 20184 states

The Storm Prediction Center issued this mesoscale discussion at Sep 20, 2018, 2:31 PM CDT for 4 states. It was in force for 119 min.

The area

The outline as issued.

The facts

Issued: Sep 20, 2018, 2:31 PM CDT (19:31 UTC)
Expired: Sep 20, 2018, 4:30 PM CDT
In force: 119 min
Issued by: the Storm Prediction Center
Chance of a watch: 80%

All 90 counties

Adair County, IA, Adams County, IA, Audubon County, IA, Boone County, IA, Buena Vista County, IA, Calhoun County, IA, Carroll County, IA, Cass County, IA, Cherokee County, IA, Crawford County, IA, Dallas County, IA, Fremont County, IA, Greene County, IA, Guthrie County, IA, Harrison County, IA, Humboldt County, IA, Ida County, IA, Mills County, IA, Monona County, IA, Montgomery County, IA, Page County, IA, Plymouth County, IA, Pocahontas County, IA, Pottawattamie County, IA, Sac County, IA, Shelby County, IA, Taylor County, IA, Webster County, IA, Woodbury County, IA, Barton County, KS, Brown County, KS, Clay County, KS, Cloud County, KS, Dickinson County, KS, Ellsworth County, KS, Geary County, KS, Jewell County, KS, Lincoln County, KS, Marshall County, KS, Mitchell County, KS, Nemaha County, KS, Osborne County, KS, Ottawa County, KS, Pottawatomie County, KS, Republic County, KS, Riley County, KS, Russell County, KS, Saline County, KS, Smith County, KS, Washington County, KS, Atchison County, MO, Holt County, MO, Nodaway County, MO, Adams County, NE, Burt County, NE, Butler County, NE, Cass County, NE, Clay County, NE, Colfax County, NE, Cuming County, NE, Dakota County, NE, Dixon County, NE, Dodge County, NE, Douglas County, NE, Fillmore County, NE, Gage County, NE, Hamilton County, NE, Jefferson County, NE, Johnson County, NE, Lancaster County, NE, Merrick County, NE, Nance County, NE, Nemaha County, NE, Nuckolls County, NE, Otoe County, NE, Pawnee County, NE, Platte County, NE, Polk County, NE, Richardson County, NE, Saline County, NE, Sarpy County, NE, Saunders County, NE, Seward County, NE, Stanton County, NE, Thayer County, NE, Thurston County, NE, Washington County, NE, Wayne County, NE, Webster County, NE, York County, NE

The radar

The Omaha radar (KOAX), 32 km from the middle of the area, began a volume at 19:31 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 383Sep 20, 3:10 PM CDT

The nearest sounding before it

Omaha, NE (KOAX), launched 12:00Z, 7.5 hours before the alert went out and 32 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: 330 J/kg
Mixed-layer CIN: -151 J/kg
Mixed-layer LCL: 1471 m above ground
0-6 km bulk shear: 47 kt
0-1 km storm-relative helicity: 276 m²/s²
0-3 km storm-relative helicity: 280 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.3

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 20, 2:15 PM CDT	Mesoscale Discussion	SPC	Buena Vista, Cerro Gordo, Cherokee, Clay, Dickinson, Emmet and 12 more	3 hr
Sep 20, 3:11 PM CDT	Severe Thunderstorm Watch	SPC	Adair, Adams, Audubon, Boone, Buena Vista, Calhoun and 38 more	8 hr
Sep 20, 5:29 PM CDT	Mesoscale Discussion	SPC	Allamakee	2 hr
Sep 20, 5:48 PM CDT	Mesoscale Discussion	SPC	Audubon, Boone, Bremer, Buena Vista, Butler, Calhoun and 37 more	57 min
Sep 20, 6:23 PM CDT	Tornado Watch	SPC	Allamakee, Chickasaw, Floyd, Howard, Mitchell, Winneshiek	5 hr
Sep 19, 11:26 PM CDT	Mesoscale Discussion	SPC	Arthur, Chase, Deuel, Dundy, Hayes, Keith and 2 more	94 min

Nearby

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