Alert archive / Colorado / Severe Thunderstorm Warnings in 2023

Severe Thunderstorm Warning 464, NWS Denver/Boulder, CO

August 27, 2023Larimer County, Colorado

NWS Denver/Boulder, CO issued this severe thunderstorm warning at Aug 27, 2023, 1:43 PM MDT for Larimer County, Colorado. It was in force for 47 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
Aug 27, 2023, 1:43 PM MDT (19:43 UTC)
Expired
Aug 27, 2023, 2:30 PM MDT
In force
47 min
Issued by
NWS Denver/Boulder, CO
Area
Storm-based polygon
Hail
1.25 in
Wind
50.0 mph

County Larimer County, CO

The radar

The Cheyenne radar (KCYS), 77 km from the middle of the area, began a volume at 19:45 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, 7.7 hours before the alert went out and 310 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 2023-08-27Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 21 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 2023-08-27The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 43 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
21 J/kg
Mixed-layer CIN
-241 J/kg
Mixed-layer LCL
1815 m above ground
0-6 km bulk shear
16 kt
0-1 km storm-relative helicity
43 m²/s²
0-3 km storm-relative helicity
62 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 Aug 27, 11:45 AM MDT, 1 hour 58 minutes earlier.

Area forecast discussion, Aug 27, 11:45 AM MDT, 1 hour 58 minutes before
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Hazardous weather outlook, Aug 27, 10:57 AM MDT, 2 hours 46 minutes before
Hazardous Weather Outlook
National Weather Service Denver/Boulder CO
1057 AM MDT Sun Aug 27 2023

COZ030>051-281700-
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-
1057 AM MDT Sun Aug 27 2023

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

.DAY ONE...Today and Tonight

Showers and thunderstorms will form over the higher terrain early
this afternoon and then spread eastward across the Urban Corridor
and eastern plains through rest of the afternoon and evening.
Small hail, wind gusts to 50 mph, and heavy rain will accompany
the stronger storms. A severe storm or two will be possible with
winds to 60 mph.

.DAYS TWO THROUGH SEVEN...Monday through Saturday

There will be a good chance of showers and storms on Monday, with
locally heavy rainfall, especially over the higher terrain. A
warmer and drier period is expected to develop for Tuesday,
Wednesday, and Thursday.

.SPOTTER INFORMATION STATEMENT...

Spotter activation will not be needed today or tonight.

In the hours before

Special weather statement, Aug 27, 1:20 PM MDT, 23 minutes before
Special Weather Statement
National Weather Service Denver CO
120 PM MDT Sun Aug 27 2023

COZ038-272000-
Larimer County Below 6000 Feet/Northwest Weld County CO-
120 PM MDT Sun Aug 27 2023

...A strong thunderstorm will impact portions of northwestern Weld
and northeastern Larimer Counties through 200 PM MDT...

At 119 PM MDT, Doppler radar was tracking a strong thunderstorm 7
miles west of Carr, or 21 miles north of Fort Collins, moving
southeast at 15 mph.

HAZARD...Winds in excess of 40 mph, penny size hail and brief heavy
         rainfall.

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...
Wellington, Nunn, and Carr.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

Brief heavy rainfall is also occurring with this storm and may lead
to localized street flooding. Do not drive your vehicle through
flooded roadways.

&&

LAT...LON 4071 10458 4070 10506 4092 10511 4093 10510
      4093 10504 4092 10502 4094 10500 4094 10493
TIME...MOT...LOC 1919Z 318DEG 15KT 4087 10501

MAX HAIL SIZE...0.75 IN
MAX WIND GUST...40 MPH

COOPER

The office that day

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

IssuedProductOfficeCountiesLasted
Aug 27, 1:20 PM MDTSpecial Weather StatementBOUWeld40 min
Aug 27, 2:33 PM MDTAreal Flood AdvisoryBOULarimer92 min
Aug 27, 2:46 PM MDTSpecial Weather StatementBOULarimer44 min
Aug 27, 2:56 PM MDTFlash Flood WarningBOULarimer2 hr
Aug 27, 3:33 PM MDTSpecial Weather StatementBOUBoulder42 min
Aug 27, 4:18 PM MDTSpecial Weather StatementBOULarimer42 min
Aug 27, 5:17 PM MDTSpecial Weather StatementBOUDouglas43 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.