Alert archive / Colorado / Severe Thunderstorm Warnings in 2023

Severe Thunderstorm Warning 309, NWS Denver/Boulder, CO

July 20, 2023Washington County, Colorado

NWS Denver/Boulder, CO issued this severe thunderstorm warning at Jul 20, 2023, 8:09 AM MDT for Washington County, Colorado. It was in force for 51 min. No storm report in the archive falls inside the area while it was in force.

The area

The counties it named.

The facts

Issued: Jul 20, 2023, 8:09 AM MDT (14:09 UTC)
Expired: Jul 20, 2023, 9:00 AM MDT
In force: 51 min
Issued by: NWS Denver/Boulder, CO
Area: Storm-based polygon
Damage threat: Considerable
Hail: 0.75 in
Wind: 70.0 mph

County Washington County, CO

The radar

The Denver radar (KFTG), 117 km from the middle of the area, began a volume at 14:11 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.

The nearest sounding before it

N. Platte/Lee Bi, NE (KLBF), launched 12:00Z, 2.2 hours before the alert went out and 255 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: 265 J/kg
Mixed-layer CIN: -168 J/kg
Mixed-layer LCL: 986 m above ground
0-6 km bulk shear: 31 kt
0-1 km storm-relative helicity: -42 m²/s²
0-3 km storm-relative helicity: 79 m²/s²
Significant tornado parameter: -0.0
Supercell composite: -0.0

Open this sounding in Storm Lab

What forecasters said that day

The local office's own words before this severe thunderstorm warning went out, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS Denver/Boulder, CO wrote its last area forecast discussion before this severe thunderstorm warning went out at Jul 20, 5:38 AM MDT, 2 hours 31 minutes earlier.

Area forecast discussion, Jul 20, 5:38 AM MDT, 2 hours 31 minutes before

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Hazardous weather outlook, Jul 20, 3:43 AM MDT, 4 hours 26 minutes before

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In the hours before

Special weather statement, Jul 20, 7:38 AM MDT, 31 minutes before

Special Weather Statement
National Weather Service Denver CO
738 AM MDT Thu Jul 20 2023

COZ044-049-201430-
Washington County CO-Morgan County CO-
738 AM MDT Thu Jul 20 2023

...Strong thunderstorms will impact portions of southeastern Morgan
and Washington Counties through 830 AM MDT...

At 738 AM MDT, Doppler radar was tracking strong thunderstorms along
a line extending from near Midway to 4 miles north of Elba to 6 miles
southwest of Arickaree School, or along a line extending from 18
miles east of Fort Morgan to 10 miles south of Akron to 26 miles
north of Flagler. Movement was northeast at 30 mph.

HAZARD...Wind gusts up to 50 mph and penny size hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor damage to outdoor objects is
         possible.

Locations impacted include...
Akron, Otis, Thurman, Arickaree School, Cope, Anton, Elba, Platner,
Burdett, Midway and Lone Star.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

&&

LAT...LON 3957 10324 4019 10364 4043 10314 4043 10280
      3957 10280
TIME...MOT...LOC 1338Z 251DEG 26KT 4023 10345 4001 10319 3967 10311

MAX HAIL SIZE...0.75 IN
MAX WIND GUST...50 MPH

ENTREKIN

The office that day

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

Issued	Product	Office	Counties	Lasted
Jul 20, 3:02 AM MDT	Flood Watch	BOU	Elbert, Lincoln, Washington	21 hr
Jul 20, 7:38 AM MDT	Special Weather Statement	BOU	Washington	52 min
Jul 20, 9:28 AM MDT	Severe Thunderstorm Warning	BOU	Logan, Weld	47 min
Jul 20, 9:47 AM MDT	Areal Flood Advisory	BOU	Logan, Weld	3 hr
Jul 20, 10:10 AM MDT	Severe Thunderstorm Warning	BOU	Logan	50 min
Jul 20, 10:49 AM MDT	Special Weather Statement	BOU	Logan	41 min
Jul 20, 12:23 PM MDT	Flash Flood Warning	BOU	Larimer	3 hr
Jul 20, 1:13 PM MDT	Flash Flood Warning	BOU	Larimer	3 hr
Jul 20, 1:34 PM MDT	Special Weather Statement	BOU	Arapahoe	41 min
Jul 20, 1:58 PM MDT	Severe Thunderstorm Warning	BOU	Adams, Arapahoe	32 min
Jul 20, 2:05 PM MDT	Severe Thunderstorm Warning	BOU	Douglas, Elbert	40 min
Jul 20, 2:17 PM MDT	Areal Flood Advisory	BOU	Douglas, Elbert	3 hr
Jul 20, 2:35 PM MDT	Severe Thunderstorm Warning	BOU	Adams, Arapahoe, Morgan	25 min
Jul 20, 2:40 PM MDT	Severe Thunderstorm Warning Considerable damage threat	BOU	Elbert	50 min
Jul 20, 2:56 PM MDT	Severe Thunderstorm Warning	BOU	Adams, Morgan, Washington	49 min
Jul 20, 3:23 PM MDT	Severe Thunderstorm Warning Considerable damage threat	BOU	Elbert	52 min
Jul 20, 3:38 PM MDT	Areal Flood Advisory	BOU	Elbert	3 hr
Jul 20, 3:50 PM MDT	Special Weather Statement	BOU	Jefferson	25 min
Jul 20, 3:54 PM MDT	Severe Thunderstorm Warning	BOU	Lincoln	51 min
Jul 20, 3:59 PM MDT	Flash Flood Warning	BOU	Grand	117 min
Jul 20, 4:01 PM MDT	Severe Thunderstorm Warning	BOU	Arapahoe, Denver, Douglas, Jefferson	44 min
Jul 20, 4:07 PM MDT	Severe Thunderstorm Warning	BOU	Elbert, Lincoln	38 min
Jul 20, 4:16 PM MDT	Severe Thunderstorm Warning	BOU	Morgan, Washington	32 min
Jul 20, 4:25 PM MDT	Severe Thunderstorm Warning Destructive damage threat	BOU	Lincoln	50 min
Jul 20, 4:38 PM MDT	Severe Thunderstorm Warning	BOU	Adams	52 min
Jul 20, 4:43 PM MDT	Severe Thunderstorm Warning	BOU	Elbert, Lincoln	47 min
Jul 20, 4:59 PM MDT	Areal Flood Advisory	BOU	Elbert, Lincoln	3 hr
Jul 20, 4:59 PM MDT	Special Weather Statement	BOU	Washington	46 min
Jul 20, 5:05 PM MDT	Areal Flood Advisory	BOU	Morgan, Washington	3 hr
Jul 20, 5:10 PM MDT	Severe Thunderstorm Warning	BOU	Adams, Arapahoe, Washington	50 min
Jul 20, 5:15 PM MDT	Severe Thunderstorm Warning	BOU	Lincoln	15 min
Jul 20, 5:27 PM MDT	Areal Flood Advisory	BOU	Adams, Morgan	3 hr
Jul 20, 5:28 PM MDT	Severe Thunderstorm Warning	BOU	Washington	47 min
Jul 20, 5:43 PM MDT	Severe Thunderstorm Warning	BOU	Arapahoe, Elbert, Lincoln, Washington	47 min

Nearby

Severe Thunderstorm Warnings in Colorado, 2023 Every severe thunderstorm warning in 2023

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.