Alert archive / Colorado / Mesoscale Discussions in 2026
Mesoscale Discussion 2321
The Storm Prediction Center issued this mesoscale discussion at Sep 20, 2026, 10:52 PM MDT for 16 counties in Colorado; Greeley County, Hamilton County, Kansas. It was in force for 83 min.
The area
The outline as issued.
The facts
- Issued
- Sep 20, 2026, 10:52 PM MDT (04:52 UTC)
- Expired
- Sep 21, 2026, 12:15 AM MDT
- In force
- 83 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe thunderstorm watch 674
Counties Adams County, CO, Arapahoe County, CO, Bent County, CO, Cheyenne County, CO, Crowley County, CO, Denver County, CO, Douglas County, CO, El Paso County, CO, Elbert County, CO, Kiowa County, CO, Kit Carson County, CO, Lincoln County, CO, Otero County, CO, Prowers County, CO, Pueblo County, CO, Washington County, CO, Greeley County, KS, Hamilton County, KS
The radar
The Pueblo radar (KPUX), 72 km from the middle of the area, began a volume at 04:53 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
Dodge City, (KDDC), launched 00:00Z, 4.9 hours before the alert went out and 340 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
- 278 J/kg
- Mixed-layer CIN
- -222 J/kg
- Mixed-layer LCL
- 838 m above ground
- 0-6 km bulk shear
- 31 kt
- 0-1 km storm-relative helicity
- 21 m²/s²
- 0-3 km storm-relative helicity
- 103 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.1
The text
As transmitted.
606
ACUS11 KWNS 210452
SWOMCD
SPC MCD 210452
KSZ000-COZ000-210615-
Mesoscale Discussion 2321
NWS Storm Prediction Center Norman OK
1152 PM CDT Sun Sep 20 2026
Areas affected...portions of eastern Colorado and extreme western
Kansas
Concerning...Severe Thunderstorm Watch 674...
Valid 210452Z - 210615Z
The severe weather threat for Severe Thunderstorm Watch 674
continues.
SUMMARY...Strong-to-severe thunderstorms will continue this evening
into the early morning hours. Large hail and strong damaging
thunderstorm winds will be possible.
DISCUSSION...Scattered strong-to-severe thunderstorms, including
severe supercells, are ongoing this evening across eastern Colorado.
These supercells are capable of producing large-to-very-large hail,
with MRMS MESH episodically exceeding 2 inches across many of these
storms. Additionally, the supercell across Crowley County, Colorado,
is exhibiting signs of strong, perhaps damaging, convective outflow
winds. Overall, these storms will continue to move southeast, with
the storms having the strongest mesocyclones favoring a more
southerly direction.
The background environment remains conducive for severe
thunderstorms. MUCAPE is in excess of 1000 J/kg with effective layer
shear exceeding 40 knots is more than sufficient to sustain ongoing
supercells and an attendant large-hail threat into the early morning
hours. With time, however, increasing precipitation coverage should
weaken the overall instability and lead to a decrease in the overall
severe threat. Until that happens, large hail and damaging
thunderstorm winds will continue as individual storms move southeast
across the area.
..Marsh.. 09/21/2026
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...DDC...GLD...PUB...BOU...
LAT...LON 37840462 38010503 38840504 39840504 40130505 40420458
40170364 39840281 39440213 39060183 38470171 37970165
37590191 37620347 37840462
MOST PROBABLE PEAK TORNADO INTENSITY...UP TO 90 MPH
MOST PROBABLE PEAK WIND GUST...65-80 MPH
MOST PROBABLE PEAK HAIL SIZE...2.00-3.50 INSPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Sep 20, 8:01 PM MDT | Mesoscale Discussion | SPC | Adams, Arapahoe, Bent, Broomfield, Cheyenne, Denver and 10 more | 119 min |
| Sep 20, 9:01 PM MDT | Severe Thunderstorm Watch | SPC | Adams, Arapahoe, Bent, Cheyenne, Crowley, Denver and 9 more | 5 hr |
| Sep 21, 1:24 AM MDT | Mesoscale Discussion | SPC | Bent, Crowley, Kiowa, Otero, Prowers | 66 min |
Nearby
Mesoscale Discussions in Colorado, 2026Mesoscale Discussions in Kansas, 2026Every mesoscale discussion in 2026
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.