Alert archive / Colorado / Mesoscale Discussions in 2021

Mesoscale Discussion 1731

September 12, 20219 counties in Colorado; 4 counties in Kansas

The Storm Prediction Center issued this mesoscale discussion at Sep 12, 2021, 3:44 PM MDT for 9 counties in Colorado; 4 counties in Kansas. It was in force for 91 min.

The area

The outline as issued.

The facts

Issued: Sep 12, 2021, 3:44 PM MDT (21:44 UTC)
Expired: Sep 12, 2021, 5:15 PM MDT
In force: 91 min
Issued by: the Storm Prediction Center
Concerning: Severe potential...watch unlikely
Chance of a watch: 20%

Counties Bent County, CO, Cheyenne County, CO, Crowley County, CO, Kiowa County, CO, Kit Carson County, CO, Lincoln County, CO, Prowers County, CO, Washington County, CO, Yuma County, CO, Cheyenne County, KS, Greeley County, KS, Sherman County, KS, Wallace County, KS

The radar

The Goodland radar (KGLD), 106 km from the middle of the area, began a volume at 21:45 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, 9.7 hours before the alert went out and 91 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: 9 J/kg
Mixed-layer CIN: -377 J/kg
Mixed-layer LCL: 2276 m above ground
0-6 km bulk shear: 40 kt
0-1 km storm-relative helicity: 25 m²/s²
0-3 km storm-relative helicity: 41 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

367 
ACUS11 KWNS 122144
SWOMCD
SPC MCD 122144 
NEZ000-KSZ000-COZ000-122315-

Mesoscale Discussion 1731
NWS Storm Prediction Center Norman OK
0444 PM CDT Sun Sep 12 2021

Areas affected...Portions of eastern Colorado...far western
Kansas...and far southwest Nebraska

Concerning...Severe potential...Watch unlikely 

Valid 122144Z - 122315Z

Probability of Watch Issuance...20 percent

SUMMARY...There will be an isolated threat of severe wind gusts into
the evening across portions of the central High Plains.

DISCUSSION...Storms have developed along the Colorado Front Range in
an area of weak upslope flow. Moisture is somewhat limited with
surface dewpoints in the 40s, but temperatures have warmed into the
upper 80s to low 90s which has generated sufficient instability for
occasional strong updrafts with some organization given around 35
knots of effective shear per KFTG VWP. Given the hot boundary layer
and steep lapse rates, severe wind gusts will be possible with any
of this activity. The best chance for these stronger gusts will
likely be farther away from the terrain where dewpoints are in the
low 50s which yields slightly higher instability around 500 J/kg.
Any threat is expected to remain isolated, therefore, no severe
thunderstorm watch is anticipated.

..Bentley/Grams.. 09/12/2021

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

ATTN...WFO...LBF...DDC...GLD...PUB...BOU...

LAT...LON   39660409 40190352 40570230 40190174 38770163 37540190
            37450295 37860367 39660409

Nearby

Mesoscale Discussions in Colorado, 2021 Mesoscale Discussions in Kansas, 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.