Alert archive / Iowa / Mesoscale Discussions in 2011

Mesoscale Discussion 741

May 11, 201112 counties in Iowa; Cedar County, Dakota County, Dixon County, Nebraska; 5 counties in South Dakota

The Storm Prediction Center issued this mesoscale discussion at May 11, 2011, 5:03 PM CDT for 12 counties in Iowa; Cedar County, Dakota County, Dixon County, Nebraska; 5 counties in South Dakota. It was in force for 57 min.

The area

The outline as issued.

The facts

Issued: May 11, 2011, 5:03 PM CDT (22:03 UTC)
Expired: May 11, 2011, 6:00 PM CDT
In force: 57 min
Issued by: the Storm Prediction Center

Counties Buena Vista County, IA, Cherokee County, IA, Clay County, IA, Dickinson County, IA, Ida County, IA, Lyon County, IA, O'Brien County, IA, Osceola County, IA, Plymouth County, IA, Sac County, IA, Sioux County, IA, Woodbury County, IA, Cedar County, NE, Dakota County, NE, Dixon County, NE, Clay County, SD, Lincoln County, SD, Turner County, SD, Union County, SD, Yankton County, SD

The radar

The Sioux Falls radar (KFSD), 80 km from the middle of the area, began a volume at 22:03 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 12:00Z, 10.1 hours before the alert went out and 177 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: 909 J/kg
Mixed-layer CIN: -95 J/kg
Mixed-layer LCL: 1123 m above ground
0-6 km bulk shear: 24 kt
0-1 km storm-relative helicity: 55 m²/s²
0-3 km storm-relative helicity: 177 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 3.2

Open this sounding in Storm Lab

The text

As transmitted, in the capitals the NWS used until 2016.

612 
ACUS11 KWNS 112204
SWOMCD
SPC MCD 112203
IAZ000-MNZ000-NEZ000-SDZ000-112300-

MESOSCALE DISCUSSION 0741
NWS STORM PREDICTION CENTER NORMAN OK
0503 PM CDT WED MAY 11 2011

AREAS AFFECTED...FAR NORTHEAST NEB/SOUTHEAST SD AND NORTHWEST
IA/SOUTHWEST MN

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 112203Z - 112300Z

MONITORING SHORT TERM TRENDS TO THE NORTH OF TORNADO WATCH 281 FOR
THE POSSIBILITY OF A NEW WATCH ACROSS FAR NORTHEAST NEB/SOUTHEAST SD
AND NORTHWEST IA/SOUTHWEST MN.

A ROUGHLY WEST-EAST BAND OF STRONG/SEVERE TSTMS CONTINUES TO
STEADILY ADVANCE NORTH-NORTHEASTWARD ACROSS FAR NORTHEAST NEB LATE
THIS AFTERNOON. AT THE SAME TIME...IT APPEARS THAT A SEGMENT OF A
WARM FRONT HAS GRADUALLY RETURNED NORTHWARD ACROSS FAR NORTHEAST
NEB/NORTHWEST IA OVER THE PAST SEVERAL HOURS. GIVEN THE CURRENT
TRENDS/EXISTING ORGANIZATION OF THE ONGOING CONVECTION...BOUTS OF
SEVERE HAIL AND DAMAGING WINDS GUSTS WILL REMAIN POSSIBLE OVER THE
NEXT FEW HOURS...AND A WATCH COULD BE NEEDED. NORFOLK NEB RECENTLY
/2127Z/ REPORTED A 49 KT WIND GUST.

..GUYER.. 05/11/2011

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...DMX...FSD...OAX...

LAT...LON   42659765 43219753 43669633 43549504 42909483 42279512
            42389714 42659765

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
May 10, 8:45 PM CDT	Mesoscale Discussion	SPC	Allamakee, Howard, Mitchell, Winneshiek, Worth	90 min
May 11, 8:09 AM CDT	Mesoscale Discussion	SPC	Allamakee, Appanoose, Benton, Black Hawk, Bremer, Buchanan and 32 more	66 min
May 11, 1:23 PM CDT	Severe Thunderstorm Watch	SPC	Allamakee, Benton, Buchanan, Cedar, Clayton, Clinton and 17 more	6 hr
May 11, 2:31 PM CDT	Mesoscale Discussion	SPC	Adair, Adams, Audubon, Carroll, Cass, Crawford and 13 more	59 min
May 11, 2:53 PM CDT	Tornado Watch	SPC	Adair, Adams, Appanoose, Audubon, Boone, Carroll and 33 more	6 hr
May 11, 3:38 PM CDT	Mesoscale Discussion	SPC	Allamakee, Appanoose, Benton, Black Hawk, Buchanan, Cedar and 26 more	2 hr
May 11, 6:17 PM CDT	Mesoscale Discussion	SPC	Appanoose, Clarke, Davis, Decatur, Jasper, Lucas and 9 more	28 min
May 11, 12:16 PM CDT	Severe Thunderstorm Watch	SPC	Adams, Buffalo, Butler, Cass, Clay, Colfax and 37 more	5 hr
May 11, 3:57 PM CDT	Mesoscale Discussion	SPC	Nemaha, Pawnee, Richardson	48 min
May 11, 4:52 PM CDT	Tornado Watch	SPC	Dundy, Furnas, Harlan, Hitchcock, Red Willow	6 hr

Nearby

Mesoscale Discussions in Iowa, 2011 Mesoscale Discussions in South Dakota, 2011 Mesoscale Discussions in Nebraska, 2011 Every 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.