Alert archive / Colorado / Severe Thunderstorm Watches in 2021

Severe Thunderstorm Watch 174

May 15, 202115 counties in Colorado

The Storm Prediction Center issued this severe thunderstorm watch at May 15, 2021, 4:06 PM MDT for 15 counties in Colorado. It was in force for 6 hr.

The area

The outline as issued.

The facts

Issued: May 15, 2021, 4:06 PM MDT (22:06 UTC)
Expired: May 15, 2021, 9:47 PM MDT
In force: 6 hr
Issued by: the Storm Prediction Center
Largest hail expected: 2 in
Strongest gust expected: 55 kt

Counties Baca County, CO, Bent County, CO, Cheyenne County, CO, Crowley County, CO, Douglas County, CO, El Paso County, CO, Elbert County, CO, Huerfano County, CO, Kiowa County, CO, Kit Carson County, CO, Las Animas County, CO, Lincoln County, CO, Otero County, CO, Prowers County, CO, Pueblo County, CO

The radar

The Pueblo radar (KPUX), 74 km from the middle of the area, began a volume at 22:08 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.

What SPC expected

The probabilities SPC published with the watch, for the watch area over its life.

Two or more tornadoes: 20%
One or more EF2 to EF5 tornadoes: 5%
Ten or more severe wind reports: 30%
One or more gusts of 65 knots or more: 10%
Ten or more severe hail reports: 40%
One or more hailstones of 2 inches or more: 40%
Six or more combined severe hail and wind reports: 70%

Warnings issued inside it

11 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.

Issued	Product	Office	Counties	Lasted
May 15, 5:22 PM MDT	Severe Thunderstorm Warning	PUB	Baca	38 min
May 15, 5:27 PM MDT	Severe Thunderstorm Warning	PUB	Custer, Fremont, Pueblo	63 min
May 15, 5:46 PM MDT	Severe Thunderstorm Warning	PUB	Bent, Otero	59 min
May 15, 5:57 PM MDT	Severe Thunderstorm Warning	PUB	Pueblo	63 min
May 15, 6:22 PM MDT	Severe Thunderstorm Warning	PUB	Baca	23 min
May 15, 6:26 PM MDT	Severe Thunderstorm Warning	PUB	Bent, Crowley, Kiowa, Otero	64 min
May 15, 6:56 PM MDT	Severe Thunderstorm Warning	PUB	Prowers	64 min
May 15, 6:58 PM MDT	Severe Thunderstorm Warning	PUB	Baca	32 min
May 15, 7:01 PM MDT	Tornado Warning	PUB	Bent	17 min
May 15, 8:30 PM MDT	Severe Thunderstorm Warning	PUB	Kiowa	45 min
May 15, 9:28 PM MDT	Severe Thunderstorm Warning	GLD	Cheyenne	12 min

Discussions around it

SPC mesoscale discussions over the same counties from four hours before the watch to its end.

The nearest sounding before it

Denver, CO (KDNR), launched 12:00Z, 10.1 hours before the alert went out and 150 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: 21 J/kg
Mixed-layer CIN: -326 J/kg
Mixed-layer LCL: 769 m above ground
0-6 km bulk shear: 24 kt
0-1 km storm-relative helicity: 48 m²/s²
0-3 km storm-relative helicity: 74 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

165 
WWUS20 KWNS 152204
SEL4  
SPC WW 152204
COZ000-160400-

URGENT - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Watch Number 174
NWS Storm Prediction Center Norman OK
405 PM MDT Sat May 15 2021

The NWS Storm Prediction Center has issued a

* Severe Thunderstorm Watch for portions of 
  East-central and southeast Colorado

* Effective this Saturday afternoon and evening from 405 PM until
  1000 PM MDT.

* Primary threats include...
  Scattered large hail and isolated very large hail events to 2
    inches in diameter possible
  Isolated damaging wind gusts to 65 mph possible
  A tornado or two possible

SUMMARY...Multiple cells should gradually intensify along the I-25
corridor and spread east towards east-central and southeast
Colorado. While convective mode will most likely evolve into a
loosely organized cluster, strengthening low-level flow towards
sunset renders concern for a brief tornado or two as well.

The severe thunderstorm watch area is approximately along and 70
statute miles east and west of a line from 20 miles north of Limon
CO to 50 miles east southeast of Trinidad CO. For a complete
depiction of the watch see the associated watch outline update
(WOUS64 KWNS WOU4).

PRECAUTIONARY/PREPAREDNESS ACTIONS...

REMEMBER...A Severe Thunderstorm Watch means conditions are
favorable for severe thunderstorms in and close to the watch area.
Persons in these areas should be on the lookout for threatening
weather conditions and listen for later statements and possible
warnings. Severe thunderstorms can and occasionally do produce
tornadoes.

&&

OTHER WATCH INFORMATION...CONTINUE...WW 172...WW 173...

AVIATION...A few severe thunderstorms with hail surface and aloft to
2 inches. Extreme turbulence and surface wind gusts to 55 knots. A
few cumulonimbi with maximum tops to 450. Mean storm motion vector
25025.

...Grams

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
May 15, 1:57 PM MDT	Mesoscale Discussion	SPC	Adams, Arapahoe, Baca, Bent, Cheyenne, Crowley and 15 more	2 hr
May 15, 5:07 PM MDT	Tornado Watch	SPC	Baca, Bent, Crowley, Kiowa, Otero, Prowers	5 hr
May 15, 5:17 PM MDT	Mesoscale Discussion	SPC	Bent, Prowers	58 min

Nearby

Severe Thunderstorm Watches in Colorado, 2021 Every severe thunderstorm watch 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.