Alert archive / Nebraska / Mesoscale Discussions in 2021
Mesoscale Discussion 747
The Storm Prediction Center issued this mesoscale discussion at May 26, 2021, 11:45 AM MDT for 5 counties in Colorado; 11 counties in Nebraska; 5 counties in Wyoming. It was in force for 2 hr.
The area
The outline as issued.
The facts
- Issued
- May 26, 2021, 11:45 AM MDT (17:45 UTC)
- Expired
- May 26, 2021, 1:45 PM MDT
- In force
- 2 hr
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch likely
- Chance of a watch
- 80%
All 21 counties
Logan County, CO, Morgan County, CO, Phillips County, CO, Sedgwick County, CO, Weld County, CO, Arthur County, NE, 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, Sioux County, NE, Converse County, WY, Goshen County, WY, Laramie County, WY, Niobrara County, WY, Platte County, WY
The radar
The Cheyenne radar (KCYS), 112 km from the middle of the area, began a volume at 17:51 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, 5.8 hours before the alert went out and 223 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
- 138 J/kg
- Mixed-layer CIN
- -221 J/kg
- Mixed-layer LCL
- 1456 m above ground
- 0-6 km bulk shear
- 40 kt
- 0-1 km storm-relative helicity
- 128 m²/s²
- 0-3 km storm-relative helicity
- 61 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.1
The text
As transmitted.
278
ACUS11 KWNS 261745
SWOMCD
SPC MCD 261745
NEZ000-COZ000-SDZ000-WYZ000-261945-
Mesoscale Discussion 0747
NWS Storm Prediction Center Norman OK
1245 PM CDT Wed May 26 2021
Areas affected...portions of eastern Wyoming and northeastern
Colorado...and into the Nebraska Panhandle
Concerning...Severe potential...Watch likely
Valid 261745Z - 261945Z
Probability of Watch Issuance...80 percent
SUMMARY...Initial storm development is expected across portions of
the central High Plains, focused on eastern WY/northeastern CO,
within the next 1 to 2 hours. WW will likely be required.
DISCUSSION...Latest surface analysis shows a warm front -- extending
from a low over central Wyoming -- draped southeastward across
southeastern Wyoming and far northeastern Colorado into northwestern
Kansas. As cirrus has thinned across eastern Wyoming, heating of
the modestly moist boundary layer has resulted in 500 to 1000 J/kg
mixed-layer CAPE development along the boundary.
As the upper circulation indicated by WV imagery near the
northwestern corner of Wyoming continues eastward, increasing ascent
-- focused near the surface low and associated warm front -- to
permit storm development to occur. The increase in ascent is
evident across the higher terrain of southeastern Wyoming within a
visible satellite loop, where cumulus has begun to grow/increase.
This trend should continue, and coupled with continued
heating/modest destabilization with time, storm development is
expected to occur.
With southeasterly low-level flow in the vicinity of the front
beneath mid-level west-southwesterlies that should gradually
strengthen with time, shear will favor rotating storms initially.
Large hail, and locally damaging winds, would be the primary severe
risks. With time, linear/upscale growth is expected, as storms move
into the Nebraska Panhandle late this afternoon/this evening --
suggesting increasingly widespread potential for damaging winds.
..Goss/Hart.. 05/26/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...LBF...UNR...GLD...BOU...CYS...
LAT...LON 43520502 42970353 42320224 41520161 40190176 39970278
39970495 41420515 42920601 43520502SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| May 26, 3:42 PM MDT | Tornado Watch | SPC | Cheyenne, Kit Carson, Logan, Morgan, Phillips, Sedgwick and 2 more | 8 hr |
| May 26, 4:44 PM MDT | Mesoscale Discussion | SPC | Phillips, Sedgwick | 2 hr |
| May 26, 9:14 AM MDT | Mesoscale Discussion | SPC | Dundy, Hitchcock, Red Willow | 61 min |
| May 26, 1:27 PM MDT | Severe Thunderstorm Watch | SPC | Arthur, Banner, Box Butte, Cherry, Cheyenne, Dawes and 11 more | 8 hr |
| May 26, 5:07 PM MDT | Severe Thunderstorm Watch | SPC | Adams, Blaine, Buffalo, Butler, Clay, Custer and 28 more | 8 hr |
| May 26, 5:48 PM MDT | Mesoscale Discussion | SPC | Box Butte, Dawes, Morrill, Scotts Bluff, Sheridan, Sioux | 87 min |
Nearby
Mesoscale Discussions in Nebraska, 2021Mesoscale Discussions in Colorado, 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.