Alert archive / Kansas / Mesoscale Discussions in 2021
Mesoscale Discussion 438
The Storm Prediction Center issued this mesoscale discussion at Apr 27, 2021, 4:24 PM MDT for 6 counties in Colorado; 8 counties in Kansas; 8 counties in Nebraska. It was in force for 2 hr.
The area
The outline as issued.
The facts
- Issued
- Apr 27, 2021, 4:24 PM MDT (22:24 UTC)
- Expired
- Apr 27, 2021, 6:30 PM MDT
- In force
- 2 hr
- Issued by
- the Storm Prediction Center
- Concerning
- Severe thunderstorm watch 112
All 22 counties
Cheyenne County, CO, Kit Carson County, CO, Lincoln County, CO, Phillips County, CO, Washington County, CO, Yuma County, CO, Cheyenne County, KS, Decatur County, KS, Graham County, KS, Norton County, KS, Rawlins County, KS, Sheridan County, KS, Sherman County, KS, Thomas County, KS, Chase County, NE, Dundy County, NE, Frontier County, NE, Furnas County, NE, Hayes County, NE, Hitchcock County, NE, Perkins County, NE, Red Willow County, NE
The radar
The Goodland radar (KGLD), 42 km from the middle of the area, began a volume at 22:26 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, 10.4 hours before the alert went out and 125 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
- 3214 m above ground
- 0-6 km bulk shear
- 67 kt
- 0-1 km storm-relative helicity
- 51 m²/s²
- 0-3 km storm-relative helicity
- 72 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
289
ACUS11 KWNS 272224
SWOMCD
SPC MCD 272224
KSZ000-NEZ000-COZ000-280030-
Mesoscale Discussion 0438
NWS Storm Prediction Center Norman OK
0524 PM CDT Tue Apr 27 2021
Areas affected...Northeast Colorado...Northwest Kansas...and
Southwest Nebraska
Concerning...Severe Thunderstorm Watch 112...
Valid 272224Z - 280030Z
The severe weather threat for Severe Thunderstorm Watch 112
continues.
SUMMARY...A severe hail and wind risk will continue for the next few
hours and may extend into portions of northwest KS and southwest NE.
While hail/wind will be the primary threat, a tornado or two will
remain possible in the near term.
DISCUSSION...Convection continues to mature across northeast CO as
storms slowly move eastward towards the KS/NE border. Clearing skies
and richer boundary-layer moisture across northwest KS have allowed
instability to increase across this region to nearly 1500 J/kg
SBCAPE, which may support an increase in intensity of the ongoing
convection (especially within the Limon, CO to northwest KS
corridor). East/northeasterly low-level winds are supporting
elongated hodographs and 50-60 knots of effective bulk shear across
this region, which should further support organized convection.
Additionally, this backed flow along and north of a warm
front/dryline boundary is supporting 100-200 m2/s2 of effective SRH
(around 150 m2s2 0-1 km SRH per the KGLD VWP). This has been
sufficient for a couple of brief tornadoes across the CO Plains.
This will continue to support a tornado threat with any discrete
convection in the near term before deeper boundary-layer mixing
reduces low-level directional shear. Discrete storms are expected to
gradually grow upscale via storm interactions as they move closer to
the NE/KS border, but given the relatively limited spatial extent of
favorable instability (possibly confined to east CO/northwest KS per
satellite trends), the coverage of the severe threat is somewhat
uncertain after 01 UTC. Trends will be monitored and a new watch may
be needed in the coming hours.
..Moore.. 04/27/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...GID...LBF...GLD...PUB...BOU...
LAT...LON 38500339 39070372 39970401 40590316 41030182 41110095
40820023 40329969 39599949 39199975 39180096 38760254
38500339SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Apr 27, 11:15 AM MDT | Mesoscale Discussion | SPC | Adams, Arapahoe, Elbert, Kit Carson, Lincoln, Logan and 5 more | 3 hr |
| Apr 27, 11:45 AM MDT | Severe Thunderstorm Watch | SPC | Adams, Arapahoe, Cheyenne, Douglas, Elbert, Kit Carson and 8 more | 7 hr |
| Apr 27, 2:32 PM MDT | Mesoscale Discussion | SPC | Adams, Arapahoe, Elbert, Kit Carson, Lincoln, Logan and 6 more | 118 min |
| Apr 27, 5:36 PM MDT | Severe Thunderstorm Watch | SPC | Cheyenne, Decatur, Rawlins, Sheridan, Sherman, Thomas and 1 more | 5 hr |
Nearby
Mesoscale Discussions in Kansas, 2021Mesoscale Discussions in Nebraska, 2021Mesoscale Discussions in Colorado, 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.