Alert archive / Nebraska / Mesoscale Discussions in 2011
Mesoscale Discussion 2001
The Storm Prediction Center issued this mesoscale discussion at Aug 18, 2011, 12:31 PM CDT for 9 counties in Iowa; 27 counties in Nebraska; 5 counties in South Dakota. It was in force for 89 min.
The area
The outline as issued.
The facts
- Issued
- Aug 18, 2011, 12:31 PM CDT (17:31 UTC)
- Expired
- Aug 18, 2011, 2:00 PM CDT
- In force
- 89 min
- Issued by
- the Storm Prediction Center
All 41 counties
Crawford County, IA, Harrison County, IA, Ida County, IA, Mills County, IA, Monona County, IA, Plymouth County, IA, Pottawattamie County, IA, Shelby County, IA, Woodbury County, IA, Antelope County, NE, Boone County, NE, Burt County, NE, Butler County, NE, Cass County, NE, Cedar County, NE, Colfax County, NE, Cuming County, NE, Dakota County, NE, Dixon County, NE, Dodge County, NE, Douglas County, NE, Greeley County, NE, Holt County, NE, Knox County, NE, Madison County, NE, Nance County, NE, Pierce County, NE, Platte County, NE, Polk County, NE, Sarpy County, NE, Saunders County, NE, Stanton County, NE, Thurston County, NE, Washington County, NE, Wayne County, NE, Wheeler County, NE, Bon Homme County, SD, Clay County, SD, Hutchinson County, SD, Union County, SD, Yankton County, SD
The radar
The Omaha radar (KOAX), 113 km from the middle of the area, began a volume at 17:33 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.
The nearest sounding before it
Omaha, NE (KOAX), launched 12:00Z, 5.5 hours before the alert went out and 113 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.
- Mixed-layer CAPE
- 1181 J/kg
- Mixed-layer CIN
- -126 J/kg
- Mixed-layer LCL
- 683 m above ground
- 0-6 km bulk shear
- 47 kt
- 0-1 km storm-relative helicity
- 234 m²/s²
- 0-3 km storm-relative helicity
- 385 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 11.7
The text
As transmitted, in the capitals the NWS used until 2016.
255
ACUS11 KWNS 181731
SWOMCD
SPC MCD 181731
IAZ000-NEZ000-SDZ000-181900-
MESOSCALE DISCUSSION 2001
NWS STORM PREDICTION CENTER NORMAN OK
1231 PM CDT THU AUG 18 2011
AREAS AFFECTED...PARTS OF SERN SD...NERN NEB...WRN IA
CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE
VALID 181731Z - 181900Z
WHILE A WW LIKELY WILL BE NEEDED LATER THIS AFTERNOON...IT IS NOT
OUT OF THE QUESTION THAT A WW COULD BECOME NECESSARY WITHIN THE NEXT
HOUR OR TWO.
AT LEAST A SHORT TERM RECENT INTENSIFICATION OF CONVECTIVE
DEVELOPMENT HAS OCCURRED NEAR YANKTON SD...AIDED BY LARGE-SCALE
FORCING FOR UPWARD VERTICAL MOTION DOWNSTREAM OF A WEAK SHORT WAVE
IMPULSE MIGRATING THROUGH THE NORTH CENTRAL HIGH PLAINS. AS THIS
FEATURE CONTINUES EASTWARD AND SOUTHEASTWARD AROUND THE SOUTHERN
ROCKIES SUBTROPICAL RIDGE...LOWER/MID TROPOSPHERIC WARM ADVECTION
APPEARS LIKELY TO SUPPORT A FURTHER INCREASE IN STORMS ACROSS THE
MID MISSOURI VALLEY. STEEP MID-LEVEL LAPSE RATES ARE CONTRIBUTING
TO SIZABLE MOST UNSTABLE CAPE ON THE ORDER OF 3000+ J/KG ACROSS THIS
REGION...WHICH PROBABLY WILL BE SUFFICIENT FOR ADDITIONAL
STRONG/SEVERE STORMS IN THE PRESENCE OF FAVORABLE VERTICAL SHEAR FOR
UPDRAFT ROTATION...BENEATH 30-35 KT WEST NORTHWESTERLY 500 MB FLOW.
THE RISK FOR LARGE HAIL APPEARS THE MOST PROMINENT SEVERE THREAT
THROUGH 20-21Z...BEFORE CONVECTION BEGINS TO BECOME MORE
SUBSTANTIALLY ROOTED IN A MODERATELY TO STRONGLY UNSTABLE BOUNDARY
LAYER WITH WEAKENING INHIBITION.
..KERR.. 08/18/2011
...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...
ATTN...WFO...DMX...FSD...OAX...GID...LBF...
LAT...LON 43389806 43259695 42679576 42039509 41309501 40879549
40939693 41389843 42189894 42889873 43389806SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 18, 1:27 PM CDT | Severe Thunderstorm Watch | SPC | Adair, Adams, Audubon, Carroll, Cass, Cherokee and 17 more | 8 hr |
| Aug 18, 2:51 PM CDT | Mesoscale Discussion | SPC | Adair, Adams, Audubon, Cass, Fremont, Guthrie and 9 more | 84 min |
| Aug 18, 6:18 PM CDT | Mesoscale Discussion | SPC | Fremont, Harrison, Mills, Monona, Montgomery, Page and 2 more | 27 min |
| Aug 18, 6:38 PM CDT | Tornado Watch | SPC | Fremont, Mills, Page | 5 hr |
| Aug 17, 9:18 PM CDT | Mesoscale Discussion | SPC | Blaine, Brown, Chase, Cherry, Dundy, Frontier and 10 more | 57 min |
| Aug 18, 6:00 PM CDT | Mesoscale Discussion | SPC | Johnson, Nemaha, Pawnee, Richardson | 60 min |
| Aug 18, 3:43 PM CDT | Mesoscale Discussion | SPC | Beadle, Brookings, Brown, Campbell, Clark, Codington and 20 more | 92 min |
| Aug 18, 4:45 PM CDT | Severe Thunderstorm Watch | SPC | Bennett, Brown, Buffalo, Campbell, Corson, Dewey and 22 more | 4 hr |
Nearby
Mesoscale Discussions in Nebraska, 2011Mesoscale Discussions in Iowa, 2011Mesoscale Discussions in South Dakota, 2011Every mesoscale discussion in 2011
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.