Alert archive / Colorado / Severe Thunderstorm Warnings in 2021

Severe Thunderstorm Warning 102, NWS Denver/Boulder, CO

July 9, 2021Weld County, Colorado

NWS Denver/Boulder, CO issued this severe thunderstorm warning at Jul 9, 2021, 2:34 PM MDT for Weld County, Colorado. It was in force for 41 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
Jul 9, 2021, 2:34 PM MDT (20:34 UTC)
Expired
Jul 9, 2021, 3:15 PM MDT
In force
41 min
Issued by
NWS Denver/Boulder, CO
Area
Storm-based polygon
Hail
1.0 in
Wind
60.0 mph

County Weld County, CO

The radar

The Cheyenne radar (KCYS), 57 km from the middle of the area, began a volume at 20:33 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

TimeReportWhereRemark
Jul 9, 2:51 PM MDTHAIL 14 Nw Grover, CO

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

The watch it was issued in

The SPC watch in force over the same counties when this warning went out.

IssuedProductOfficeLasted
Jul 9, 2:16 PM MDTSevere Thunderstorm WatchSPC9 hr

The nearest sounding before it

Denver, CO (KDNR), launched 12:00Z, 8.6 hours before the alert went out and 139 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-pSkew-T log-p diagram, Denver, CO at 12:00Z on 2021-07-09Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 5 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Denver, CO at 12:00Z on 2021-07-09The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 70 square meters per square second.193958Sfc1 km3 km6 km9 kmRMLM
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
5 J/kg
Mixed-layer CIN
-346 J/kg
Mixed-layer LCL
3383 m above ground
0-6 km bulk shear
29 kt
0-1 km storm-relative helicity
70 m²/s²
0-3 km storm-relative helicity
50 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

The text

As transmitted.

623 
WUUS55 KBOU 092034
SVRBOU
COC123-092115-
/O.NEW.KBOU.SV.W.0102.210709T2034Z-210709T2115Z/

BULLETIN - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Warning
National Weather Service Denver CO
234 PM MDT Fri Jul 9 2021

The National Weather Service in Denver Colorado has issued a

* Severe Thunderstorm Warning for...
  North central Weld County in northeastern Colorado...

* Until 315 PM MDT.

* At 233 PM MDT, a severe thunderstorm was located 5 miles west of
  Hereford, or 24 miles southeast of Cheyenne, moving southeast at 30
  mph.

  HAZARD...60 mph wind gusts and quarter size hail.

  SOURCE...Radar indicated.

  IMPACT...Expect damage to roofs, siding, and trees. Hail damage to 
           vehicles is expected.

* Locations impacted include...
  Grover, Pawnee Buttes and Hereford. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

Heavy rainfall is occurring with this storm, and may lead to flash 
flooding. Do not drive your vehicle through flooded roadways.

&&

LAT...LON 4083 10448 4100 10452 4099 10393 4074 10392
      4070 10420
TIME...MOT...LOC 2033Z 312DEG 26KT 4095 10440 

HAIL...1.00IN
WIND...60MPH
 
$$

RJK
3 follow-up statements
177 
WWUS55 KBOU 092049
SVSBOU

Severe Weather Statement
National Weather Service Denver CO
249 PM MDT Fri Jul 9 2021

COC123-092115-
/O.CON.KBOU.SV.W.0102.000000T0000Z-210709T2115Z/
Weld CO-
249 PM MDT Fri Jul 9 2021

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 315 PM MDT
FOR NORTH CENTRAL WELD COUNTY...

At 249 PM MDT, a severe thunderstorm was located 4 miles northwest of
Grover, or 30 miles southeast of Cheyenne, moving southeast at 25
mph.

HAZARD...60 mph wind gusts and quarter size hail.

SOURCE...Radar indicated.

IMPACT...Expect damage to roofs, siding, and trees. Hail damage to 
         vehicles is expected.

Locations impacted include...
Grover, Pawnee Buttes and Hereford. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

Very heavy rain rainfall is occurring with this storm, and may lead 
to flash flooding. Do not drive your vehicle through flooded 
roadways.

&&

LAT...LON 4083 10440 4100 10442 4099 10393 4074 10392
      4070 10420
TIME...MOT...LOC 2049Z 307DEG 23KT 4090 10430 

HAIL...1.00IN
WIND...60MPH
 
$$

RJK
973 
WWUS55 KBOU 092107
SVSBOU

Severe Weather Statement
National Weather Service Denver CO
307 PM MDT Fri Jul 9 2021

COC123-092115-
/O.CON.KBOU.SV.W.0102.000000T0000Z-210709T2115Z/
Weld CO-
307 PM MDT Fri Jul 9 2021

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 315 PM MDT
FOR NORTH CENTRAL WELD COUNTY...

At 306 PM MDT, a severe thunderstorm was located 6 miles southeast of
Grover, or 36 miles southwest of Kimball, moving southeast at 35 mph.

HAZARD...60 mph wind gusts and quarter size hail.  A spotter 3 miles 
         northwest of Grover in north central Weld County reported 
         quarter sized hail at 2:51 PM MDT

SOURCE...Radar indicated.

IMPACT...Expect damage to roofs, siding, and trees. Hail damage to 
         vehicles is expected.

Locations impacted include...
Pawnee Buttes.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 4084 10421 4099 10419 4099 10393 4074 10392
      4071 10415
TIME...MOT...LOC 2106Z 301DEG 29KT 4083 10411 

HAIL...1.00IN
WIND...60MPH
 
$$

RJK
119 
WWUS55 KBOU 092116
SVSBOU

Severe Weather Statement
National Weather Service Denver CO
316 PM MDT Fri Jul 9 2021

COC123-092124-
/O.EXP.KBOU.SV.W.0102.000000T0000Z-210709T2115Z/
Weld CO-
316 PM MDT Fri Jul 9 2021

...THE SEVERE THUNDERSTORM WARNING FOR NORTH CENTRAL WELD COUNTY WILL
EXPIRE AT 315 PM MDT...
                
The storm which prompted the warning has weakened below severe
limits, and no longer poses an immediate threat to life or property.
Therefore, the warning will be allowed to expire.

A spotter 3 miles northwest of Grover in north central Weld County 
reported quarter sized hail at 2:51 PM MDT.

A Severe Thunderstorm Watch remains in effect until 900 PM MDT for
northeastern Colorado.

LAT...LON 4084 10421 4099 10419 4099 10393 4074 10392
      4071 10415
TIME...MOT...LOC 2114Z 312DEG 26KT 4079 10405 

$$

RJK

The office that day

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

IssuedProductOfficeCountiesLasted
Jul 8, 6:02 PM MDTSpecial Weather StatementBOUPhillips43 min
Jul 9, 3:00 PM MDTAreal Flood AdvisoryBOUGrand2 hr
Jul 9, 3:25 PM MDTSevere Thunderstorm WarningBOUWeld38 min
Jul 9, 3:58 PM MDTSevere Thunderstorm WarningBOULogan47 min
Jul 9, 4:44 PM MDTSevere Thunderstorm WarningBOULogan36 min
Jul 9, 5:22 PM MDTSpecial Weather StatementBOUPhillips38 min
Jul 9, 5:40 PM MDTSpecial Weather StatementBOUMorgan35 min

Nearby

Severe Thunderstorm Warnings in Colorado, 2021Every 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.