Alert archive / Colorado / Severe Thunderstorm Warnings in 2021

Severe Thunderstorm Warning 90, NWS Denver/Boulder, CO

June 25, 2021Boulder County, Jefferson County, Colorado

NWS Denver/Boulder, CO issued this severe thunderstorm warning at Jun 25, 2021, 1:59 PM MDT for Boulder County, Jefferson County, Colorado. It was in force for 46 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: Jun 25, 2021, 1:59 PM MDT (19:59 UTC)
Expired: Jun 25, 2021, 2:45 PM MDT
In force: 46 min
Issued by: NWS Denver/Boulder, CO
Area: Storm-based polygon
Hail: 1.0 in
Wind: 50.0 mph

Counties Boulder County, CO, Jefferson County, CO

The radar

The Denver radar (KFTG), 56 km from the middle of the area, began a volume at 20:02 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
Jun 25, 2:00 PM MDT	HAIL 1	4 Wnw Boulder, 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 12:00Z, 8.0 hours before the alert went out and 164 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: 50 J/kg
Mixed-layer CIN: -128 J/kg
Mixed-layer LCL: 1292 m above ground
0-6 km bulk shear: 14 kt
0-1 km storm-relative helicity: -9 m²/s²
0-3 km storm-relative helicity: 34 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

051 
WUUS55 KBOU 251959
SVRBOU
COC013-059-252045-
/O.NEW.KBOU.SV.W.0090.210625T1959Z-210625T2045Z/

BULLETIN - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Warning
National Weather Service Denver CO
159 PM MDT Fri Jun 25 2021

The National Weather Service in Denver Colorado has issued a

* Severe Thunderstorm Warning for...
  North central Jefferson County in central Colorado...
  Southeastern Boulder County in northeastern Colorado...

* Until 245 PM MDT.

* At 159 PM MDT, a severe thunderstorm was located near Boulder, or
  29 miles northwest of Denver, moving southeast at 15 mph.

  HAZARD...Quarter size hail.

  SOURCE...Radar indicated.

  IMPACT...Damage to vehicles is expected.

* Locations impacted include...
  Arvada, Boulder, southwestern Longmont, western Broomfield,
  Lafayette, Louisville, Erie, Superior, Rocky Flats, Eldorado
  Springs and Niwot.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

For your protection move to an interior room on the lowest floor of a
building.

&&

LAT...LON 4015 10506 3999 10505 3993 10512 3995 10511
      3996 10512 3993 10515 3991 10514 3990 10514
      3991 10515 3991 10517 3989 10516 3983 10522
      4002 10536 4016 10528
TIME...MOT...LOC 1959Z 320DEG 15KT 4007 10528 

HAIL...1.00IN
WIND...<50MPH
 
$$

ENTREKIN

1 follow-up statement

837 
WWUS55 KBOU 252037
SVSBOU

Severe Weather Statement
National Weather Service Denver CO
237 PM MDT Fri Jun 25 2021

COC013-059-252047-
/O.EXP.KBOU.SV.W.0090.000000T0000Z-210625T2045Z/
Jefferson CO-Boulder CO-
237 PM MDT Fri Jun 25 2021

...THE SEVERE THUNDERSTORM WARNING FOR NORTH CENTRAL JEFFERSON AND
SOUTHEASTERN BOULDER COUNTIES WILL EXPIRE AT 245 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.  However small hail and heavy rain are still
possible with this thunderstorm.

LAT...LON 4015 10506 3999 10505 3993 10512 3995 10511
      3996 10512 3993 10515 3991 10514 3990 10514
      3991 10515 3991 10517 3989 10516 3983 10522
      4002 10536 4016 10528
TIME...MOT...LOC 2037Z 320DEG 15KT 3907 10400 

$$

ENTREKIN

The office that day

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

Issued	Product	Office	Counties	Lasted
Jun 24, 6:08 PM MDT	Severe Thunderstorm Warning	BOU	Lincoln	19 min
Jun 24, 6:19 PM MDT	Areal Flood Advisory	BOU	Larimer	86 min
Jun 24, 6:33 PM MDT	Special Weather Statement	BOU	Lincoln	42 min
Jun 24, 7:56 PM MDT	Special Weather Statement	BOU	Lincoln	49 min
Jun 25, 12:30 PM MDT	Special Weather Statement	BOU	Weld	45 min
Jun 25, 1:10 PM MDT	Special Weather Statement	BOU	Morgan	35 min
Jun 25, 1:25 PM MDT	Areal Flood Advisory	BOU	Larimer	70 min
Jun 25, 1:32 PM MDT	Areal Flood Advisory	BOU	Boulder	88 min
Jun 25, 1:52 PM MDT	Special Weather Statement	BOU	Logan	23 min
Jun 25, 2:04 PM MDT	Flash Flood Warning	BOU	Larimer	116 min
Jun 25, 2:16 PM MDT	Special Weather Statement	BOU	Douglas	44 min
Jun 25, 2:26 PM MDT	Special Weather Statement	BOU	Logan	49 min
Jun 25, 2:35 PM MDT	Special Weather Statement	BOU	Elbert	40 min
Jun 25, 2:50 PM MDT	Special Weather Statement	BOU	Broomfield	40 min
Jun 25, 2:57 PM MDT	Special Weather Statement	BOU	Weld	48 min
Jun 25, 3:10 PM MDT	Special Weather Statement	BOU	Phillips	50 min
Jun 25, 3:24 PM MDT	Special Weather Statement	BOU	Lincoln	51 min
Jun 25, 4:12 PM MDT	Areal Flood Advisory	BOU	Arapahoe	93 min
Jun 25, 4:42 PM MDT	Areal Flood Advisory	BOU	Arapahoe, Douglas	93 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.