Alert archive / Colorado / Severe Thunderstorm Warnings in 2021

Severe Thunderstorm Warning 32, NWS Denver/Boulder, CO

May 20, 2021Logan County, Colorado

NWS Denver/Boulder, CO issued this severe thunderstorm warning at May 20, 2021, 8:15 PM MDT for Logan County, Colorado. It was in force for 30 min. 1 report came from inside the area while it was in force.

The area

The outline as issued, with what was reported inside it.

The facts

Issued: May 20, 2021, 8:15 PM MDT (02:15 UTC)
Expired: May 20, 2021, 8:45 PM MDT
In force: 30 min
Issued by: NWS Denver/Boulder, CO
Area: Storm-based polygon
Hail: 2.0 in
Wind: 60.0 mph

County Logan County, CO

The radar

The Cheyenne radar (KCYS), 119 km from the middle of the area, began a volume at 02:17 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 was reported inside it

Time	Report	Where	Remark
May 20, 8:35 PM MDT	HAIL 2.75	5 N Westplains, CO

Local storm reports filed while the alert was in force, from inside its polygon or its counties.

The nearest sounding before it

Denver, CO (KDNR), launched 00:00Z, 2.3 hours before the alert went out and 117 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: 66 J/kg
Mixed-layer CIN: -60 J/kg
Mixed-layer LCL: 3320 m above ground
0-6 km bulk shear: 37 kt
0-1 km storm-relative helicity: 41 m²/s²
0-3 km storm-relative helicity: 120 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

732 
WUUS55 KBOU 210215
SVRBOU
COC075-210245-
/O.NEW.KBOU.SV.W.0032.210521T0215Z-210521T0245Z/

BULLETIN - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Warning
National Weather Service Denver CO
815 PM MDT Thu May 20 2021

The National Weather Service in Denver Colorado has issued a

* Severe Thunderstorm Warning for...
  Northwestern Logan County in northeastern Colorado...

* Until 845 PM MDT.

* At 814 PM MDT, a severe thunderstorm was located near Westplains,
  or 23 miles northwest of Sterling, moving northeast at 25 mph.

  HAZARD...Two inch hail and 60 mph wind gusts.

  SOURCE...Trained weather spotters.

  IMPACT...Expect damage to roofs, siding, and trees. People and 
           animals outdoors will be injured. Expect hail damage to 
           roofs, siding, windows, and vehicles.

* Locations impacted include...
  Westplains.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

This storm is producing large hail. SEEK SHELTER NOW inside a sturdy
structure and stay away from windows!

&&

LAT...LON 4083 10345 4089 10355 4100 10351 4100 10316
TIME...MOT...LOC 0214Z 210DEG 20KT 4090 10346 

HAIL...2.00IN
WIND...60MPH
 
$$

DIRENZO

2 follow-up statements

261 
WWUS55 KBOU 210230
SVSBOU

Severe Weather Statement
National Weather Service Denver CO
830 PM MDT Thu May 20 2021

COC075-210245-
/O.CON.KBOU.SV.W.0032.000000T0000Z-210521T0245Z/
Logan CO-
830 PM MDT Thu May 20 2021

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 845 PM MDT
FOR NORTHWESTERN LOGAN COUNTY...

At 830 PM MDT, a severe thunderstorm was located 8 miles northeast of
Westplains, or 21 miles southeast of Kimball, moving northeast at 25
mph.

HAZARD...Golf ball size hail and 60 mph wind gusts.

SOURCE...Trained weather spotters.

IMPACT...Expect damage to roofs, siding, and trees. People and 
         animals outdoors will be injured. Expect hail damage to 
         roofs, siding, windows, and vehicles.

This severe thunderstorm will remain over mainly rural areas of
northwestern Logan County.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

This storm is producing large hail. SEEK SHELTER NOW inside a sturdy
structure and stay away from windows.

&&

LAT...LON 4090 10340 4093 10351 4100 10351 4100 10332
TIME...MOT...LOC 0230Z 208DEG 20KT 4098 10342 

HAIL...1.75IN
WIND...60MPH
 
$$

DIRENZO

640 
WWUS55 KBOU 210240
SVSBOU

Severe Weather Statement
National Weather Service Denver CO
840 PM MDT Thu May 20 2021

COC075-210250-
/O.EXP.KBOU.SV.W.0032.000000T0000Z-210521T0245Z/
Logan CO-
840 PM MDT Thu May 20 2021

...THE SEVERE THUNDERSTORM WARNING FOR NORTHWESTERN LOGAN COUNTY WILL
EXPIRE AT 845 PM MDT...
        
The storm which prompted the warning has weakened below severe
limits, and has exited the warned area. Therefore, the warning will
be allowed to expire.

LAT...LON 4090 10340 4093 10351 4100 10351 4100 10332
TIME...MOT...LOC 0240Z 210DEG 20KT 4102 10339 

$$

DIRENZO

The office that day

Everything else NWS Denver/Boulder, CO issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
May 20, 7:14 PM MDT	Special Weather Statement	BOU	Logan	31 min
May 20, 7:27 PM MDT	Severe Thunderstorm Warning	BOU	Logan, Weld	48 min
May 21, 3:51 PM MDT	Severe Thunderstorm Warning	BOU	Morgan, Washington	24 min
May 21, 5:30 PM MDT	Special Weather Statement	BOU	Lincoln	30 min

Nearby

Severe Thunderstorm Warnings in Colorado, 2021 Every severe thunderstorm warning 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; local storm reports from the same archive; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.