Alert archive / Colorado / Severe Thunderstorm Warnings in 2023

Severe Thunderstorm Warning 239, NWS Denver/Boulder, CO

July 4, 2023Weld County, Colorado

NWS Denver/Boulder, CO issued this severe thunderstorm warning at Jul 4, 2023, 2:00 PM MDT for Weld County, Colorado. It was in force for 30 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 4, 2023, 2:00 PM MDT (20:00 UTC)
Expired: Jul 4, 2023, 2:30 PM MDT
In force: 30 min
Issued by: NWS Denver/Boulder, CO
Area: Storm-based polygon
Hail: 0.75 in
Wind: 60.0 mph

County Weld County, CO

The radar

The Cheyenne radar (KCYS), 75 km from the middle of the area, began a volume at 20:00 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, 8.0 hours before the alert went out and 325 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: 1345 J/kg
Mixed-layer CIN: -204 J/kg
Mixed-layer LCL: 1953 m above ground
0-6 km bulk shear: 23 kt
0-1 km storm-relative helicity: 117 m²/s²
0-3 km storm-relative helicity: 206 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 1.6

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 4, 10:22 AM MDT, 3 hours 38 minutes earlier.

Area forecast discussion, Jul 4, 10:22 AM MDT, 3 hours 38 minutes before

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Hazardous weather outlook, Jul 4, 9:47 AM MDT, 4 hours 13 minutes before

Hazardous Weather Outlook
National Weather Service Denver/Boulder CO
947 AM MDT Tue Jul 4 2023

COZ030>051-051600-
Jackson County Below 9000 Feet-
West Jackson and West Grand Counties Above 9000 Feet-
Grand and Summit Counties Below 9000 Feet-
South and East Jackson/Larimer/North and Northeast Grand/
Northwest Boulder Counties Above 9000 Feet-
South and Southeast Grand/West Central and Southwest Boulder/
Gilpin/Clear Creek/Summit/North and West Park Counties Above
9000 Feet-Larimer and Boulder Counties Between 6000 and 9000 Feet-
Jefferson and West Douglas Counties Above 6000 Feet/Gilpin/Clear
Creek/Northeast Park Counties Below 9000 Feet-
Central and Southeast Park County-
Larimer County Below 6000 Feet/Northwest Weld County-
Boulder And Jefferson Counties Below 6000 Feet/West Broomfield
County-
North Douglas County Below 6000 Feet/Denver/West Adams and
Arapahoe Counties/East Broomfield County-
Elbert/Central and East Douglas Counties Above 6000 Feet-
Northeast Weld County-Central and South Weld County-Morgan County-
Central and East Adams and Arapahoe Counties-
North and Northeast Elbert County Below 6000 Feet/North Lincoln
County-
Southeast Elbert County Below 6000 Feet/South Lincoln County-
Logan County-Washington County-Sedgwick County-Phillips County-
947 AM MDT Tue Jul 4 2023

...Severe storms possible this afternoon and evening...

This hazardous weather outlook is for northeast and north central
Colorado.

.DAY ONE...Today and Tonight

Numerous showers and thunderstorms are expected this afternoon and
tonight over the foothills and plains. Some of the storms could
be severe with large hail, damaging winds and heavy rain. Heavy
rainfall could also cause flash flooding problems, most notably
over the burn areas. There could be severe rounds of storms today,
with the second round coinciding with fire work displays and
picnics this evening. Holiday enthusiasts are urged to have
adequate ways to take cover during their outside festivities.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday

Showers and thunderstorms are likely over the mountains on
Wednesday with mainly scattered showers over the plains. There
will be a threat of flash flooding over the alpine burnt areas.

Scattered late day showers and thunderstorms are forecast for
Thursday through Saturday with hail and heavy rainfall possible.
Chances for thunderstorms decrease Sunday and into early next
week.

.SPOTTER INFORMATION STATEMENT...

Spotter activation will be needed after 1 pm this afternoon.
Reports of hail, heavy rain and flooding will be appreciated.

In the hours before

Special weather statement, Jul 4, 12:44 PM MDT, 1 hour 16 minutes before

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Special weather statement, Jul 4, 12:47 PM MDT, 1 hour 13 minutes before

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Special weather statement, Jul 4, 1:11 PM MDT, 49 minutes before

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Special weather statement, Jul 4, 1:36 PM MDT, 24 minutes before

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Special weather statement, Jul 4, 1:43 PM MDT, 17 minutes before

Special Weather Statement
National Weather Service Denver CO
143 PM MDT Tue Jul 4 2023

COZ032>036-042015-
South and Southeast Grand/West Central and Southwest
Boulder/Gilpin/Clear Creek/Summit/North and West Park Counties Above
9000 Feet CO-Grand and Summit Counties Below 9000 Feet CO-
Larimer and Boulder Counties Between 6000 and 9000 Feet CO-
Jefferson and West Douglas Counties Above  6000 Feet/Gilpin/Clear
Creek/Northeast Park Counties Below 9000 Feet CO-
South and East Jackson/Larimer/North and Northeast Grand/Northwest
Boulder Counties Above 9000 Feet CO-
143 PM MDT Tue Jul 4 2023

...Strong thunderstorms will impact portions of south central
Larimer, Gilpin, eastern Grand, northwestern Clear Creek and western
Boulder Counties through 215 PM MDT...

At 142 PM MDT, Doppler radar was tracking strong thunderstorms along
a line extending from 4 miles northwest of Bear Lake to near Berthoud
Pass, or along a line extending from 36 miles west of Fort Collins to
42 miles west of Denver. Movement was east at 40 mph.

HAZARD...Wind gusts up to 50 mph and half inch 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...
Estes Park, Nederland, Fraser, Bear Lake, Winter Park, Central City,
Grand Lake, Jamestown, Ward, Black Hawk, Raymond, Berthoud Pass,
Brainard Lake, Tolland, Gold Hill, Tabernash, Meeker Park, Rollins
Pass, Eldora and Rollinsville.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Prepare for sudden gusty winds. Secure loose objects and move to a
safe shelter inside a building or vehicle.

If outdoors, consider seeking shelter inside a building.

Frequent cloud to ground lightning is occurring with these storms.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

&&

LAT...LON 4042 10537 3981 10542 3979 10586 4039 10584
TIME...MOT...LOC 1942Z 262DEG 36KT 4035 10571 3982 10575

MAX HAIL SIZE...0.50 IN
MAX WIND GUST...50 MPH

RPK

The office that day

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

Issued	Product	Office	Counties	Lasted
Jul 3, 7:00 PM MDT	Special Weather Statement	BOU	Weld	45 min
Jul 4, 12:44 PM MDT	Special Weather Statement	BOU	Larimer	31 min
Jul 4, 12:47 PM MDT	Special Weather Statement	BOU	Douglas	28 min
Jul 4, 1:00 PM MDT	Severe Thunderstorm Warning	BOU	Grand	30 min
Jul 4, 1:11 PM MDT	Special Weather Statement	BOU	Larimer	34 min
Jul 4, 1:17 PM MDT	Severe Thunderstorm Warning	BOU	Grand	28 min
Jul 4, 1:36 PM MDT	Special Weather Statement	BOU	Larimer	24 min
Jul 4, 1:43 PM MDT	Special Weather Statement	BOU	Boulder, Gilpin	32 min
Jul 4, 2:13 PM MDT	Severe Thunderstorm Warning Considerable damage threat	BOU	Weld	47 min
Jul 4, 2:21 PM MDT	Special Weather Statement	BOU	Boulder, Broomfield, Gilpin	24 min
Jul 4, 2:38 PM MDT	Areal Flood Advisory	BOU	Larimer	3 hr
Jul 4, 2:42 PM MDT	Severe Thunderstorm Warning	BOU	Weld	33 min
Jul 4, 3:40 PM MDT	Special Weather Statement	BOU	Logan	35 min
Jul 4, 4:05 PM MDT	Special Weather Statement	BOU	Grand	25 min
Jul 4, 4:31 PM MDT	Special Weather Statement	BOU	Jackson	29 min
Jul 4, 4:52 PM MDT	Severe Thunderstorm Warning	BOU	Jackson	23 min
Jul 4, 5:14 PM MDT	Severe Thunderstorm Warning	BOU	Jackson, Larimer	31 min
Jul 4, 5:19 PM MDT	Special Weather Statement	BOU	Boulder	26 min
Jul 4, 5:36 PM MDT	Severe Thunderstorm Warning Considerable damage threat	BOU	Larimer	24 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.