Alert archive / Nebraska / Mesoscale Discussions in 2011

Mesoscale Discussion 1978

August 14, 20114 states

The Storm Prediction Center issued this mesoscale discussion at Aug 14, 2011, 1:59 PM MDT for 4 states. It was in force for 91 min.

The area

The outline as issued.

The facts

Issued: Aug 14, 2011, 1:59 PM MDT (19:59 UTC)
Expired: Aug 14, 2011, 3:30 PM MDT
In force: 91 min
Issued by: the Storm Prediction Center

All 43 counties

Adams County, CO, Arapahoe County, CO, Cheyenne County, CO, Crowley County, CO, El Paso County, CO, Elbert County, CO, Kiowa County, CO, Kit Carson County, CO, Lincoln County, CO, Logan County, CO, Morgan County, CO, Phillips County, CO, Sedgwick County, CO, Washington County, CO, Yuma County, CO, Cheyenne County, KS, Sherman County, KS, Wallace County, KS, Arthur County, NE, Banner County, NE, Box Butte County, NE, Chase County, NE, Cheyenne County, NE, Dawes County, NE, Deuel County, NE, Dundy County, NE, Garden County, NE, Grant County, NE, Keith County, NE, Kimball County, NE, Morrill County, NE, Perkins County, NE, Scotts Bluff County, NE, Sheridan County, NE, Sioux County, NE, Bennett County, SD, Custer County, SD, Fall River County, SD, Jackson County, SD, Lawrence County, SD, Meade County, SD, Oglala Lakota County, SD, Pennington County, SD

The radar

The Cheyenne radar (KCYS), 147 km from the middle of the area, began a volume at 19:58 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 781Aug 14, 2:30 PM MDT

The nearest sounding before it

Denver, CO (KDNR), launched 12:00Z, 8.0 hours before the alert went out and 111 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: 249 J/kg
Mixed-layer CIN: -409 J/kg
Mixed-layer LCL: 1695 m above ground
0-6 km bulk shear: 23 kt
0-1 km storm-relative helicity: 16 m²/s²
0-3 km storm-relative helicity: -26 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

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

726 
ACUS11 KWNS 141959
SWOMCD
SPC MCD 141959 
NEZ000-KSZ000-SDZ000-COZ000-142130-

MESOSCALE DISCUSSION 1978
NWS STORM PREDICTION CENTER NORMAN OK
0259 PM CDT SUN AUG 14 2011

AREAS AFFECTED...NERN/E-CNTRL CO...WRN NEB...SWRN SD...FAR NWRN KS

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 

VALID 141959Z - 142130Z

THE THREAT FOR SVR STORMS MAY INCREASE THIS AFTERNOON...AND THE
ISSUANCE OF A WW IS POSSIBLE.

ISOLATED CONVECTION CONTINUES TO DEVELOP IN RESPONSE TO OROGRAPHIC
FORCING OVER THE HIGHER TERRAIN ADJACENT TO THE HIGH PLAINS.
MID-LEVEL ASCENT OFFERED BY AN IMPULSE TRANSLATING EWD ACROSS THE
GREAT BASIN TOWARD THE ROCKIES COULD PROMOTE AN INCREASE IN
CONVECTIVE COVERAGE/INTENSITY LATER THIS AFTERNOON INTO THE
EVENING...AS IT INTERACTS WITH SFC CONVERGENCE ALONG A
TROUGH/BAROCLINIC ZONE IN THE LEE OF THE ROCKIES. SSELY/SLY FLOW
EAST OF THIS FEATURE IS MAINTAINING DEWPOINTS IN THE LOWER
60S...WHILE DEWPOINTS IN THE 50S EXIST SW OF A REMNANT FRONT IN THE
MORE DEEPLY MIXED / HOTTER BOUNDARY LAYER ACROSS PORTIONS OF E-CNTRL
CO. WITH MLCAPE VALUES OF 1000-2500 J/KG ACROSS MUCH OF THE REGION
IN ASSOCIATION WITH A PLUME OF STEEP MID-LEVEL LAPSE RATES ATTENDANT
TO AN IN SITU EML...VIGOROUS CONVECTION MAY ENSUE. WHILE CAPPING
ASSOCIATED WITH THIS EML MAY SUPPRESS CONVECTIVE COVERAGE THROUGH
22Z...CINH MAY BE SURMOUNTED BY THE INFLUENCES OF THE APPROACHING
IMPULSE THEREAFTER. MODEST WLY TO WNWLY FLOW IS CONTRIBUTING TO
EFFECTIVE BULK SHEAR MAGNITUDES OF 25 TO 35 KT...WHICH MAY SUPPORT
ORGANIZED STORM STRUCTURES...POSSIBLY SUPERCELLS...WITH LARGE HAIL
AND DMGG WIND GUSTS BEING ATTENDANT THREATS. AS ACTIVITY SHIFTS EWD
TOWARD RICHER LOW-LEVEL MOISTURE OVER THE PLAINS...MERGING STORM
CLUSTERS COULD PROMOTE LOCALIZED AREAS OF UPSCALE GROWTH...WHICH MAY
BE ASSOCIATED WITH AN ENHANCED THREAT FOR DMGG WIND GUSTS.

..COHEN.. 08/14/2011

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

ATTN...WFO...LBF...UNR...GLD...PUB...BOU...CYS...

LAT...LON   38350206 38070354 38350455 39080493 39700464 40240444
            40890397 41980394 43260392 44560379 44720224 43780164
            41910127 40930123 39600140 38350206

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Aug 14, 2:29 PM MDT	Severe Thunderstorm Watch	SPC	Cheyenne, Kit Carson, Logan, Phillips, Sedgwick, Washington and 1 more	7 hr
Aug 14, 11:46 AM MDT	Mesoscale Discussion	SPC	Brown, Campbell, Edmunds, McPherson, Marshall, Walworth	59 min
Aug 14, 5:56 PM MDT	Mesoscale Discussion	SPC	Harding	94 min

Nearby

Mesoscale Discussions in Nebraska, 2011 Mesoscale Discussions in Colorado, 2011 Mesoscale Discussions in South Dakota, 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.