Alert archive / Nebraska / Mesoscale Discussions in 2021

Mesoscale Discussion 711

May 23, 20217 counties in Colorado; 11 counties in Nebraska; Fall River County, South Dakota

The Storm Prediction Center issued this mesoscale discussion at May 23, 2021, 1:57 PM MDT for 7 counties in Colorado; 11 counties in Nebraska; Fall River County, South Dakota. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued: May 23, 2021, 1:57 PM MDT (19:57 UTC)
Expired: May 23, 2021, 4:00 PM MDT
In force: 2 hr
Issued by: the Storm Prediction Center
Concerning: Tornado watch 196

Counties Kit Carson County, CO, Logan County, CO, Morgan County, CO, Phillips County, CO, Sedgwick County, CO, Washington County, CO, Yuma County, CO, Banner County, NE, Box Butte County, NE, Cheyenne County, NE, Dawes County, NE, Deuel County, NE, Garden County, NE, Kimball County, NE, Morrill County, NE, Scotts Bluff County, NE, Sheridan County, NE, Sioux County, NE, Fall River County, SD

The radar

The Cheyenne radar (KCYS), 146 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 nearest sounding before it

Denver, CO (KDNR), launched 12:00Z, 8.0 hours before the alert went out and 169 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: 0 J/kg
Mixed-layer CIN: No buoyant parcel
Mixed-layer LCL: 1106 m above ground
0-6 km bulk shear: 59 kt
0-1 km storm-relative helicity: 73 m²/s²
0-3 km storm-relative helicity: 177 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

525 
ACUS11 KWNS 231957
SWOMCD
SPC MCD 231957 
NEZ000-KSZ000-SDZ000-COZ000-WYZ000-232200-

Mesoscale Discussion 0711
NWS Storm Prediction Center Norman OK
0257 PM CDT Sun May 23 2021

Areas affected...Parts of northeastern Colorado and southeastern
Wyoming into southwestern South Dakota...the Nebraska Panhandle and
northwestern Kansas

Concerning...Tornado Watch 196...

Valid 231957Z - 232200Z

The severe weather threat for Tornado Watch 196 continues.

SUMMARY...Thunderstorms are expected to continue to increase in
coverage through late afternoon.  This may be accompanied by
continuing risk for large hail and tornadoes, but it appears that
activity will begin consolidating into an organizing, northeastward
and eastward advancing cluster with strong surface gusts becoming
the more prominent hazard by 4-5 PM MDT.

DISCUSSION...Scattered strong to severe thunderstorm development is
ongoing, particularly within deepening surface troughing near/just
west of the Wyoming/Nebraska border, southward to near Limon, CO. 
This is occurring in the presence of an increasingly less inhibited,
moist boundary-layer characterized by moderately large CAPE of
1000-2000 J/kg, and strong deep-layer vertical shear.

As the southeastern-most vigorous mid-level perturbation (within
larger-scale mid-level troughing emerging from the Intermountain
West) gradually accelerates north-northeastward across the Front
Range through 21-23Z, a substantive further increase in thunderstorm
development appears likely.  A convective outflow generated or
enhanced surface front already appears to be surging east of the
Laramie Mountains.  As convection continues to increase, steepening
lower/mid tropospheric lapse rates may support strengthen outflows,
which probably will begin to consolidate and contribute to an
upscale growing and organizing convective system.  This should tend
to propagate north-northeastward and eastward with increasing
potential for strong surface gusts by early evening.

..Kerr.. 05/23/2021

...Please see www.spc.noaa.gov for graphic product...

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

LAT...LON   43960330 42790207 40090190 38970288 38920324 40010383
            42370420 43960330

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
May 23, 10:53 AM MDT	Mesoscale Discussion	SPC	Adams, Arapahoe, Broomfield, Denver, Douglas, Elbert and 6 more	2 hr
May 23, 12:06 PM MDT	Tornado Watch	SPC	Adams, Arapahoe, Cheyenne, Crowley, Denver, Elbert and 11 more	8 hr
May 23, 2:41 PM MDT	Mesoscale Discussion	SPC	Baca, Bent, Prowers	94 min
May 23, 4:07 PM MDT	Severe Thunderstorm Watch	SPC	Baca, Bent, Las Animas, Otero, Prowers	7 hr
May 23, 4:37 PM MDT	Mesoscale Discussion	SPC	Cheyenne, Kiowa, Kit Carson, Lincoln, Logan, Phillips and 3 more	113 min
May 23, 12:58 PM MDT	Mesoscale Discussion	SPC	Haakon, Meade, Oglala Lakota, Pennington, Perkins, Ziebach	2 hr
May 23, 1:50 PM MDT	Tornado Watch	SPC	Bennett, Butte, Corson, Custer, Dewey, Fall River and 9 more	7 hr
May 23, 5:25 PM MDT	Mesoscale Discussion	SPC	Bennett, Butte, Corson, Custer, Dewey, Fall River and 9 more	95 min

Nearby

Mesoscale Discussions in Nebraska, 2021 Mesoscale Discussions in Colorado, 2021 Mesoscale Discussions in South Dakota, 2021 Every mesoscale discussion in 2021

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.