Alert archive / Nebraska / Mesoscale Discussions in 2011

Mesoscale Discussion 1998

August 17, 2011Cheyenne County, Kansas; 16 counties in Nebraska; Mellette County, Todd County, Tripp County, South Dakota

The Storm Prediction Center issued this mesoscale discussion at Aug 17, 2011, 9:18 PM CDT for Cheyenne County, Kansas; 16 counties in Nebraska; Mellette County, Todd County, Tripp County, South Dakota. It was in force for 57 min.

The area

The outline as issued.

The facts

Issued: Aug 17, 2011, 9:18 PM CDT (02:18 UTC)
Expired: Aug 17, 2011, 10:15 PM CDT
In force: 57 min
Issued by: the Storm Prediction Center

Counties Cheyenne County, KS, Blaine County, NE, Brown County, NE, Chase County, NE, Cherry County, NE, Dundy County, NE, Frontier County, NE, Hayes County, NE, Hitchcock County, NE, Hooker County, NE, Keith County, NE, Keya Paha County, NE, Lincoln County, NE, Logan County, NE, McPherson County, NE, Perkins County, NE, Thomas County, NE, Mellette County, SD, Todd County, SD, Tripp County, SD

The radar

The North Platte radar (KLNX), 17 km from the middle of the area, began a volume at 02:20 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

N. Platte/Lee Bi, NE (KLBF), launched 00:00Z, 2.3 hours before the alert went out and 79 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: 1270 J/kg
Mixed-layer CIN: -74 J/kg
Mixed-layer LCL: 1399 m above ground
0-6 km bulk shear: 46 kt
0-1 km storm-relative helicity: 55 m²/s²
0-3 km storm-relative helicity: 180 m²/s²
Significant tornado parameter: 0.6
Supercell composite: 7.5

Open this sounding in Storm Lab

The text

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

742 
ACUS11 KWNS 180218
SWOMCD
SPC MCD 180218 
SDZ000-NEZ000-KSZ000-COZ000-180315-

MESOSCALE DISCUSSION 1998
NWS STORM PREDICTION CENTER NORMAN OK
0918 PM CDT WED AUG 17 2011

AREAS AFFECTED...SRN SD...PARTS OF CENTRAL-SWRN NEB...AND FAR NWRN
KS

CONCERNING...SEVERE THUNDERSTORM WATCH 783...

VALID 180218Z - 180315Z

THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 783
CONTINUES.

LOCAL WFO AREAL AND TEMPORAL EXTENSION OF WW 783 IS POSSIBLE OVER
NORTH CENTRAL NEB.

THE GREATEST SEVERE WEATHER THREAT /PRIMARILY DUE TO LARGE HAIL/
SHOULD CONTINUE TO AFFECT SOUTH CENTRAL SD /ERN TODD AND SRN TRIPP
COUNTIES/ AND MOVE INTO NORTH CENTRAL NEB /FAR NERN CHERRY...KEYA
PAHA...BROWN...AND ROCK COUNTIES/.  THIS ACTIVITY SHOULD EXIT SRN SD
BY 03Z AND MAY AFFECT NRN NEB THROUGH 04-05Z.

OTHERWISE...AT 02Z...REGIONAL RADAR IMAGERY SHOWED THE STRONG-SEVERE
STORM THAT HAD MOVED SWD OUT OF SRN CHERRY COUNTY NEB HAS WEAKENED
CONSIDERABLY OVER MCPHERSON COUNTY NEB...WHILE A SIMILAR TREND IS
OCCURRING WITH THE CHASE COUNTY NEB STORM.

THERMODYNAMICALLY...OBJECTIVE ANALYSES INDICATED STRENGTHENING
SURFACE-BASED INHIBITION...GIVEN THE LOSS OF DAYTIME HEATING...AND
THE MIDLEVEL CAP /AROUND 700 MB/ PER 00Z LBF SOUNDING ARE RESULTING
IN A HOSTILE ENVIRONMENT FOR SUSTAINING UPDRAFTS.  THE ONLY
EXCEPTION APPEARS TO BE ACROSS THE NERN EXTENT OF WW 783 WHERE A
LOCAL WFO EXTENSION IN AREA AND TIME IS POSSIBLE THROUGH 04-05Z. 
01Z RUC SUGGESTS THE OVERALL LIKELIHOOD FOR CONVECTION WILL DECREASE
BY 05Z.

..PETERS.. 08/18/2011

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

ATTN...WFO...FSD...ABR...LBF...UNR...GLD...BOU...

LAT...LON   43730081 43729966 42829936 41979958 41799981 41720024
            40960021 40100060 39870115 39730202 40000220 41420176
            42460128 43510088 43730081

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Aug 17, 7:19 PM CDT	Mesoscale Discussion	SPC	Morton, Stanton	56 min
Aug 18, 5:26 PM CDT	Mesoscale Discussion	SPC	Barton, Edwards, Ellis, Ellsworth, Lincoln, Ness and 6 more	64 min
Aug 18, 6:00 PM CDT	Mesoscale Discussion	SPC	Atchison, Brown, Doniphan, Douglas, Jackson, Jefferson and 5 more	60 min
Aug 18, 12:31 PM CDT	Mesoscale Discussion	SPC	Antelope, Boone, Burt, Butler, Cass, Cedar and 21 more	89 min
Aug 18, 1:27 PM CDT	Severe Thunderstorm Watch	SPC	Antelope, Boone, Burt, Cass, Cedar, Colfax and 17 more	8 hr
Aug 18, 2:51 PM CDT	Mesoscale Discussion	SPC	Antelope, Boone, Burt, Butler, Cass, Colfax and 24 more	84 min
Aug 18, 6:18 PM CDT	Mesoscale Discussion	SPC	Antelope, Blaine, Boone, Boyd, Brown, Burt and 47 more	27 min
Aug 18, 6:38 PM CDT	Tornado Watch	SPC	Antelope, Blaine, Boone, Boyd, Brown, Butler and 46 more	5 hr
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, 2011 Mesoscale Discussions in South Dakota, 2011 Mesoscale Discussions in Kansas, 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.