Alert archive / Colorado / Severe Thunderstorm Warnings in 2020

Severe Thunderstorm Warning 21, NWS Denver/Boulder, CO

May 15, 2020Boulder County, Weld County, Colorado

NWS Denver/Boulder, CO issued this severe thunderstorm warning at May 15, 2020, 6:12 PM MDT for Boulder County, Weld County, Colorado. It was in force for 33 min. 4 reports 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 15, 2020, 6:12 PM MDT (00:12 UTC)
Expired
May 15, 2020, 6:45 PM MDT
In force
33 min
Issued by
NWS Denver/Boulder, CO
Area
Storm-based polygon
Hail
1.25 in
Wind
50.0 mph

Counties Boulder County, CO, Weld County, CO

The radar

The Denver radar (KFTG), 42 km from the middle of the area, began a volume at 00:11 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
May 15, 6:25 PM MDTHAIL 0.751 E Frederick, CO
May 15, 6:26 PM MDTHAIL 0.752 N Erie, CO
May 15, 6:38 PM MDTHAIL 12 Sw Fort Lupton, CO
May 15, 6:41 PM MDTHAIL 11 Sw Fort Lupton, 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, 0.2 hours before the alert went out and 142 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 00:00Z on 2020-05-16Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 3 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 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 00:00Z on 2020-05-16The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 3 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
3 J/kg
Mixed-layer CIN
-146 J/kg
Mixed-layer LCL
2005 m above ground
0-6 km bulk shear
51 kt
0-1 km storm-relative helicity
3 m²/s²
0-3 km storm-relative helicity
108 m²/s²
Significant tornado parameter
0.0
Supercell composite
-0.1

Open this sounding in Storm Lab

The text

As transmitted.

651 
WUUS55 KBOU 160012
SVRBOU
COC013-123-160045-
/O.NEW.KBOU.SV.W.0021.200516T0012Z-200516T0045Z/

BULLETIN - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Warning
National Weather Service Denver CO
612 PM MDT Fri May 15 2020

The National Weather Service in Denver Colorado has issued a

* Severe Thunderstorm Warning for...
  Southwestern Weld County in northeastern Colorado...
  East central Boulder County in northeastern Colorado...

* Until 645 PM MDT.

* At 612 PM MDT, a severe thunderstorm was located 4 miles north of
  Erie, or 26 miles north of Denver, moving east at 30 mph.

  HAZARD...Half dollar size hail.

  SOURCE...Radar indicated.

  IMPACT...Damage to vehicles is expected. Hail may accumulate on 
           roadways causing hazardous travel.

* Locations impacted include...
  Brighton, Lafayette, Erie, Firestone, Frederick, Fort Lupton,
  Lochbuie, Dacono and Hudson.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 4018 10456 4000 10456 4000 10481 4001 10496
      4004 10496 4004 10498 4003 10498 4003 10499
      4002 10500 4003 10511 4013 10511
TIME...MOT...LOC 0012Z 273DEG 24KT 4009 10507 

HAIL...1.25IN
WIND...<50MPH
 
$$

GIMMESTAD
2 follow-up statements
941 
WWUS55 KBOU 160033
SVSBOU

Severe Weather Statement
National Weather Service Denver CO
633 PM MDT Fri May 15 2020

COC013-160042-
/O.CAN.KBOU.SV.W.0021.000000T0000Z-200516T0045Z/
Boulder CO-
633 PM MDT Fri May 15 2020

...THE SEVERE THUNDERSTORM WARNING FOR EAST CENTRAL BOULDER COUNTY IS
CANCELLED...
    
The severe thunderstorm which prompted the warning has moved out of 
the warned area. Therefore, the warning has been cancelled.

LAT...LON 4018 10456 4000 10456 4000 10481 4001 10496
      4004 10496 4004 10498 4003 10498 4003 10499
      4002 10500 4003 10506 4014 10505
TIME...MOT...LOC 0032Z 273DEG 24KT 4008 10489 

$$

COC123-160045-
/O.CON.KBOU.SV.W.0021.000000T0000Z-200516T0045Z/
Weld CO-
633 PM MDT Fri May 15 2020

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 645 PM MDT
FOR SOUTHWESTERN WELD COUNTY...

At 632 PM MDT, a severe thunderstorm was located near Dacono, or 24
miles south of Greeley, moving east at 30 mph.

HAZARD...Quarter size hail.

SOURCE...Radar indicated.

IMPACT...Damage to vehicles is expected.

Locations impacted include...
Brighton, Erie, Firestone, Frederick, Fort Lupton, Lochbuie, Dacono
and Hudson.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 4018 10456 4000 10456 4000 10481 4001 10496
      4004 10496 4004 10498 4003 10498 4003 10499
      4002 10500 4003 10506 4014 10505
TIME...MOT...LOC 0032Z 273DEG 24KT 4008 10489 

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

GIMMESTAD
370 
WWUS55 KBOU 160046
SVSBOU

Severe Weather Statement
National Weather Service Denver CO
646 PM MDT Fri May 15 2020

COC123-160055-
/O.EXP.KBOU.SV.W.0021.000000T0000Z-200516T0045Z/
Weld CO-
646 PM MDT Fri May 15 2020

...THE SEVERE THUNDERSTORM WARNING FOR SOUTHWESTERN WELD COUNTY HAS
EXPIRED...
                
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 has been allowed to expire.  However small
hail, gusty winds and heavy rain are still possible with this 
thunderstorm as it moves east from Fort Lupton towards Hudson and 
Keenesburg through 730 PM.

LAT...LON 4018 10456 4000 10456 4000 10481 4001 10496
      4004 10496 4004 10498 4003 10498 4003 10499
      4002 10500 4003 10506 4014 10505
TIME...MOT...LOC 0045Z 273DEG 24KT 4008 10479 

$$

GIMMESTAD

The office that day

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

IssuedProductOfficeCountiesLasted
May 15, 6:44 PM MDTSpecial Weather StatementBOUAdams46 min
May 15, 7:13 PM MDTSevere Thunderstorm WarningBOUElbert47 min
May 15, 7:25 PM MDTSevere Thunderstorm WarningBOUMorgan, Weld38 min
May 15, 8:01 PM MDTSevere Thunderstorm WarningBOUElbert, Lincoln44 min
May 15, 8:46 PM MDTSevere Thunderstorm WarningBOUElbert, Lincoln44 min
May 16, 3:00 PM MDTFire Weather WatchBOUPark38 hr

Nearby

Severe Thunderstorm Warnings in Colorado, 2020Every severe thunderstorm warning in 2020

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.