Alert archive / Colorado / Severe Thunderstorm Warnings in 2023

Severe Thunderstorm Warning 236, NWS Denver/Boulder, CO

June 30, 2023Jefferson County, Colorado

NWS Denver/Boulder, CO issued this severe thunderstorm warning at Jun 30, 2023, 2:36 PM MDT for Jefferson County, Colorado. It was in force for 24 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
Jun 30, 2023, 2:36 PM MDT (20:36 UTC)
Expired
Jun 30, 2023, 3:00 PM MDT
In force
24 min
Issued by
NWS Denver/Boulder, CO
Area
Storm-based polygon
Hail
1.0 in
Wind
50.0 mph

County Jefferson County, CO

The radar

The Denver radar (KFTG), 64 km from the middle of the area, began a volume at 20:39 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

Grand Junction, CO (KGJT), launched 12:00Z, 8.6 hours before the alert went out and 284 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, Grand Junction, CO at 12:00Z on 2023-06-30Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 1 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, Grand Junction, CO at 12:00Z on 2023-06-30The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity -19 square meters per square second.1939Sfc1 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
1 J/kg
Mixed-layer CIN
No buoyant parcel
Mixed-layer LCL
2344 m above ground
0-6 km bulk shear
25 kt
0-1 km storm-relative helicity
-19 m²/s²
0-3 km storm-relative helicity
26 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 Jun 30, 12:41 PM MDT, 1 hour 55 minutes earlier.

Area forecast discussion, Jun 30, 12:41 PM MDT, 1 hour 55 minutes before
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Hazardous weather outlook, Jun 30, 5:43 AM MDT, 8 hours 53 minutes before
Hazardous Weather Outlook
National Weather Service Denver/Boulder CO
543 AM MDT Fri Jun 30 2023

COZ030>051-011145-
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-
543 AM MDT Fri Jun 30 2023

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

.DAY ONE...Today and Tonight

Thunderstorms will develop over the mountains by midday, and move
east across the Front Range cities this afternoon and across the
plains through the evening. Some of the stronger storms could be
severe with hail around an inch in diameter and wind gusts up to
60 mph. The greatest threat of severe weather is on the plains
south of Interstate 70 where larger hail is possible. Locally
heavy rain and minor flooding is also possible with some of the
storms. The greatest flood threat is in the Cameron Peak burn area
this afternoon.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday

Saturday will be drier with only a few weak showers and storms
expected. Thunderstorm activity temporarily increases Sunday as a
weak system pushes across the region. After a lull in
thunderstorm activity on Monday, scattered afternoon and evening
thunderstorms are expected to resume Tuesday and for most of next
week.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not anticipated today or tonight.

Gimmestad/Meier

In the hours before

Special weather statement, Jun 30, 10:03 AM MDT, 4 hours 33 minutes before
Special Weather Statement
National Weather Service Denver CO
1003 AM MDT Fri Jun 30 2023

COZ039-040-301645-
Boulder And Jefferson Counties Below 6000 Feet/West Broomfield County
CO-
North Douglas County Below 6000 Feet/Denver/West Adams and Arapahoe
Counties/East Broomfield County CO-
1003 AM MDT Fri Jun 30 2023

...A strong thunderstorm will impact portions of northwestern
Arapahoe, Denver, northeastern Jefferson and western Adams Counties
through 1045 AM MDT...

At 1001 AM MDT, Doppler radar was tracking a strong thunderstorm over
western Denver, moving northeast at 30 mph.

HAZARD...Half inch hail, and brief light to moderate rainfall.

SOURCE...Radar indicated.

IMPACT...Minor damage to outdoor objects is possible.

Locations impacted include...
Denver, Aurora, northeastern Lakewood, Thornton, southeastern Arvada,
Westminster, southern Broomfield, Commerce City, Northglenn,
Brighton, northern Englewood, Wheat Ridge, Federal Heights, Denver
International Airport, D.I.A Terminal and Concourses, Watkins,
Buckley SFB and Barr Lake.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

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

&&

LAT...LON 3966 10511 3990 10512 3997 10464 3966 10457
TIME...MOT...LOC 1601Z 235DEG 36KT 3973 10504

MAX HAIL SIZE...0.50 IN
MAX WIND GUST...<30 MPH

COOPER
Special weather statement, Jun 30, 10:25 AM MDT, 4 hours 11 minutes before
Special Weather Statement
National Weather Service Denver CO
1025 AM MDT Fri Jun 30 2023

COZ036-041-301715-
Elbert/Central and East Douglas Counties Above 6000 Feet CO-
Jefferson and West Douglas Counties Above  6000 Feet/Gilpin/Clear
Creek/Northeast Park Counties Below 9000 Feet CO-
1025 AM MDT Fri Jun 30 2023

...A strong thunderstorm will impact portions of Douglas and south
central Jefferson Counties through 1115 AM MDT...

At 1024 AM MDT, Doppler radar was tracking a strong thunderstorm near
Devil's Head, or 34 miles south of Denver, moving east at 35 mph.

HAZARD...Nickel size hail, brief moderate to heavy rainfall, up to
         one half inch possible in 30 minutes.

SOURCE...Radar indicated.

IMPACT...Minor damage to outdoor objects is possible.

Locations impacted include...
Castle Rock, Larkspur, Westcreek, Perry Park, Devil's Head,
Sprucewood, Cheesman Reservoir, Deckers, Franktown and Greenland.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

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

This storm may intensify, so be certain to monitor local radio
stations and available television stations for additional information
and possible warnings from the National Weather Service.

&&

LAT...LON 3914 10532 3937 10528 3944 10467 3913 10467
TIME...MOT...LOC 1624Z 258DEG 31KT 3926 10516

MAX HAIL SIZE...0.88 IN
MAX WIND GUST...<30 MPH

COOPER
Local storm report, Jun 30, 11:07 AM MDT, 3 hours 29 minutes before
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Local storm report, Jun 30, 12:42 PM MDT, 1 hour 54 minutes before
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Local storm report, Jun 30, 1:20 PM MDT, 1 hour 16 minutes before
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Local storm report, Jun 30, 1:43 PM MDT, 53 minutes before
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The office that day

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

IssuedProductOfficeCountiesLasted
Jun 29, 6:00 PM MDTSevere Thunderstorm WarningBOUAdams, Morgan45 min
Jun 29, 6:18 PM MDTSevere Thunderstorm Warning Considerable damage threatBOUAdams42 min
Jun 29, 6:58 PM MDTSevere Thunderstorm Warning Considerable damage threatBOUAdams, Morgan, Washington47 min
Jun 29, 7:38 PM MDTSevere Thunderstorm WarningBOUMorgan, Washington37 min
Jun 29, 7:46 PM MDTSevere Thunderstorm WarningBOUAdams, Morgan44 min
Jun 29, 8:36 PM MDTAreal Flood AdvisoryBOUAdams, Morgan, Weld6 hr
Jun 29, 9:08 PM MDTAreal Flood AdvisoryBOULarimer3 hr
Jun 30, 1:08 AM MDTSpecial Weather StatementBOUWashington52 min
Jun 30, 2:29 AM MDTAreal Flood AdvisoryBOUAdams, Morgan, Weld6 hr
Jun 30, 9:17 AM MDTAreal Flood AdvisoryBOUAdams, Morgan, Weld27 hr
Jun 30, 9:35 AM MDTSpecial Weather StatementBOUPark25 min
Jun 30, 10:03 AM MDTSpecial Weather StatementBOUDenver42 min
Jun 30, 10:25 AM MDTSpecial Weather StatementBOUDouglas50 min
Jun 30, 10:31 AM MDTAreal Flood WarningBOUWeld25 hr
Jun 30, 10:55 AM MDTAreal Flood WarningBOUWeld25 hr
Jun 30, 11:03 AM MDTAreal Flood AdvisoryBOULarimer50 min
Jun 30, 11:28 AM MDTFlash Flood WarningBOULarimer3 hr
Jun 30, 1:01 PM MDTAreal Flood AdvisoryBOULarimer2 hr
Jun 30, 1:07 PM MDTSevere Thunderstorm WarningBOULincoln15 min
Jun 30, 2:11 PM MDTSevere Thunderstorm WarningBOULincoln28 min
Jun 30, 2:55 PM MDTAreal Flood AdvisoryBOUGrand119 min

Nearby

Severe Thunderstorm Warnings in Colorado, 2023Every 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.