Alert archive / Colorado / Mesoscale Discussions in 2021
Mesoscale Discussion 708
The Storm Prediction Center issued this mesoscale discussion at May 23, 2021, 10:53 AM MDT for 4 states. It was in force for 2 hr.
The area
The outline as issued.
The facts
- Issued
- May 23, 2021, 10:53 AM MDT (16:53 UTC)
- Expired
- May 23, 2021, 1:00 PM MDT
- In force
- 2 hr
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch likely
- Chance of a watch
- 95%
All 24 counties
Adams County, CO, Arapahoe County, CO, Broomfield County, CO, Denver County, CO, Douglas County, CO, El Paso County, CO, Elbert County, CO, Lincoln County, CO, Logan County, CO, Morgan County, CO, Washington County, CO, Weld County, CO, Banner County, NE, Box Butte County, NE, Cheyenne County, NE, Dawes County, NE, Kimball County, NE, Scotts Bluff County, NE, Sioux County, NE, Fall River County, SD, Goshen County, WY, Laramie County, WY, Niobrara County, WY, Platte County, WY
The radar
The Cheyenne radar (KCYS), 31 km from the middle of the area, began a volume at 16:56 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
Denver, CO (KDNR), launched 12:00Z, 4.9 hours before the alert went out and 181 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
- 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
The text
As transmitted.
439
ACUS11 KWNS 231653
SWOMCD
SPC MCD 231653
COZ000-NEZ000-SDZ000-WYZ000-231900-
Mesoscale Discussion 0708
NWS Storm Prediction Center Norman OK
1153 AM CDT Sun May 23 2021
Areas affected...Much of eastern Wyoming and Colorado into
southwestern South Dakota and the Nebraska Panhandle
Concerning...Severe potential...Watch likely
Valid 231653Z - 231900Z
Probability of Watch Issuance...95 percent
SUMMARY...The initiation of scattered thunderstorm development is
expected during the next few hours, with a few supercells evolving
through Noon-2 PM MDT. One or more severe weather watches likely
will be needed.
DISCUSSION...Based on latest water vapor imagery, the leading edge
of the stronger mid-level forcing for ascent and cooling has begun
to overspread the Laramie Mountains, and likely will begin to spread
into and across the Front Range between now and 18-20Z. Coinciding
with continuing insolation and low-level moisture advection (mid 50s
to around 60F surface dew points across the high plains) on
southeasterly near surface flow, steepening lapse rates appear
likely to support moderately large CAPE in excess of 1500 J/kg, near
and east of the higher terrain.
As destabilization progresses, storms will initiate first across the
higher terrain, aided by favorable orographic forcing. However,
within deepening surface troughing, near the Wyoming/Nebraska
Panhandle into the plains of eastern Colorado, the initiation of at
least widely scattered thunderstorms appears possible by 20Z.
Southerly deep-layer ambient mean flow appears on the order of 40-45
kt, but with flow in the 500-300 mb layer forecast to intensify to
50-90 kt, strengthening shear will become supportive of supercells,
with a tendency to propagate northeastward and eastward. As storms
propagate off the higher terrain, and form within the lee surface
troughing, they will intensify and pose a risk for large hail and
perhaps a couple of tornadoes by mid afternoon.
..Kerr/Guyer.. 05/23/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...UNR...GLD...PUB...BOU...CYS...
LAT...LON 43910499 43050311 40770293 39530267 38500374 38800477
40010528 40500532 41560544 42800561 43910499SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| May 23, 12:06 PM MDT | Tornado Watch | SPC | Adams, Arapahoe, Cheyenne, Crowley, Denver, Elbert and 11 more | 8 hr |
| May 23, 1:57 PM MDT | Mesoscale Discussion | SPC | Kit Carson, Logan, Morgan, Phillips, Sedgwick, Washington and 1 more | 2 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 Colorado, 2021Mesoscale Discussions in Nebraska, 2021Mesoscale Discussions in Wyoming, 2021Every 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.