Alert archive / Iowa / Mesoscale Discussions in 2018

Mesoscale Discussion 1241

August 5, 201835 counties in Iowa; 23 counties in Nebraska

The Storm Prediction Center issued this mesoscale discussion at Aug 5, 2018, 9:32 PM CDT for 35 counties in Iowa; 23 counties in Nebraska. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued
Aug 5, 2018, 9:32 PM CDT (02:32 UTC)
Expired
Aug 6, 2018, 12:00 AM CDT
In force
2 hr
Issued by
the Storm Prediction Center
Chance of a watch
40%
All 58 counties

Adair County, IA, Adams County, IA, Audubon County, IA, Boone County, IA, Butler County, IA, Calhoun County, IA, Carroll County, IA, Cass County, IA, Crawford County, IA, Dallas County, IA, Franklin County, IA, Greene County, IA, Grundy County, IA, Guthrie County, IA, Hamilton County, IA, Hardin County, IA, Harrison County, IA, Humboldt County, IA, Ida County, IA, Jasper County, IA, Madison County, IA, Marion County, IA, Marshall County, IA, Mills County, IA, Monona County, IA, Montgomery County, IA, Polk County, IA, Pottawattamie County, IA, Sac County, IA, Shelby County, IA, Story County, IA, Tama County, IA, Warren County, IA, Webster County, IA, Wright County, IA, Adams County, NE, Burt County, NE, Butler County, NE, Cass County, NE, Clay County, NE, Colfax County, NE, Cuming County, NE, Dodge County, NE, Douglas County, NE, Fillmore County, NE, Hall County, NE, Hamilton County, NE, Lancaster County, NE, Merrick County, NE, Platte County, NE, Polk County, NE, Saline County, NE, Sarpy County, NE, Saunders County, NE, Seward County, NE, Washington County, NE, Webster County, NE, York County, NE

The radar

The Omaha radar (KOAX), 77 km from the middle of the area, began a volume at 02:35 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, 2.5 hours before the alert went out and 77 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-pSkew-T log-p diagram, Omaha, NE at 00:00Z on 2018-08-06Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 1818 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Omaha, NE at 00:00Z on 2018-08-06The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 190 square meters per square second.193958Sfc1 km3 km6 km9 kmRMLM
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
1818 J/kg
Mixed-layer CIN
-158 J/kg
Mixed-layer LCL
1308 m above ground
0-6 km bulk shear
55 kt
0-1 km storm-relative helicity
190 m²/s²
0-3 km storm-relative helicity
387 m²/s²
Significant tornado parameter
0.8
Supercell composite
12.2

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.

IssuedProductOfficeCountiesLasted
Aug 6, 2:31 PM CDTMesoscale DiscussionSPCHarrison, Mills, Pottawattamie89 min
Aug 6, 6:38 PM CDTMesoscale DiscussionSPCAdams, Appanoose, Clarke, Davis, Decatur, Fremont and 11 more2 hr
Aug 5, 7:05 PM CDTMesoscale DiscussionSPCBanner, Cheyenne, Kimball, Scotts Bluff, Sioux115 min
Aug 5, 8:16 PM CDTMesoscale DiscussionSPCHarlan119 min
Aug 6, 3:02 PM CDTMesoscale DiscussionSPCBanner, Kimball88 min
Aug 6, 3:37 PM CDTSevere Thunderstorm WatchSPCBanner, Cheyenne, Kimball, Morrill, Scotts Bluff7 hr
Aug 6, 3:49 PM CDTMesoscale DiscussionSPCBox Butte, Cherry, Dawes, Sheridan, Sioux86 min
Aug 6, 6:24 PM CDTMesoscale DiscussionSPCBanner, Box Butte, Cheyenne, Kimball, Morrill, Scotts Bluff and 1 more66 min

Nearby

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