Alert archive / Colorado / Special Weather Statements in 2023

Special Weather Statement, NWS Denver/Boulder, CO

July 4, 2023Boulder County, Broomfield County, Gilpin County, Colorado

NWS Denver/Boulder, CO issued this special weather statement at Jul 4, 2023, 2:21 PM MDT for Boulder County, Broomfield County, Gilpin 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 outline as issued.

The facts

Issued
Jul 4, 2023, 2:21 PM MDT (20:21 UTC)
Expired
Jul 4, 2023, 2:45 PM MDT
In force
24 min
Issued by
NWS Denver/Boulder, CO
Hail
0.50 in
Wind
40

Counties Boulder County, CO, Broomfield County, CO, Gilpin County, CO

The radar

The Denver radar (KFTG), 75 km from the middle of the area, began a volume at 20:23 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, 8.4 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 2023-07-04Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 7 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 2023-07-04The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 35 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
7 J/kg
Mixed-layer CIN
-527 J/kg
Mixed-layer LCL
2975 m above ground
0-6 km bulk shear
45 kt
0-1 km storm-relative helicity
35 m²/s²
0-3 km storm-relative helicity
225 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

The text

As transmitted.

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What forecasters said that day

The local office's own words before this special weather statement 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 special weather statement went out at Jul 4, 10:22 AM MDT, 3 hours 59 minutes earlier.

Area forecast discussion, Jul 4, 10:22 AM MDT, 3 hours 59 minutes before
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Hazardous weather outlook, Jul 4, 9:47 AM MDT, 4 hours 34 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 37 minutes before
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Special weather statement, Jul 4, 12:47 PM MDT, 1 hour 34 minutes before
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Special weather statement, Jul 4, 1:11 PM MDT, 1 hour 10 minutes before
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Special weather statement, Jul 4, 1:36 PM MDT, 45 minutes before
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Special weather statement, Jul 4, 1:43 PM MDT, 38 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
Special weather statement, Jul 4, 2:21 PM MDT, 0 minutes before
Special Weather Statement
National Weather Service Denver CO
221 PM MDT Tue Jul 4 2023

COZ033>036-038>040-043-042045-
South and Southeast Grand/West Central and Southwest
Boulder/Gilpin/Clear Creek/Summit/North and West Park Counties Above
9000 Feet CO-Central and South Weld County CO-
Boulder And Jefferson Counties Below 6000 Feet/West Broomfield County
CO-Larimer and Boulder Counties Between 6000 and 9000 Feet CO-
North Douglas County Below 6000 Feet/Denver/West Adams and Arapahoe
Counties/East Broomfield County CO-
Jefferson and West Douglas Counties Above  6000 Feet/Gilpin/Clear
Creek/Northeast Park Counties Below 9000 Feet CO-
Larimer County Below 6000 Feet/Northwest Weld County CO-
South and East Jackson/Larimer/North and Northeast Grand/Northwest
Boulder Counties Above 9000 Feet CO-
221 PM MDT Tue Jul 4 2023

...Strong thunderstorms will impact portions of southwestern Weld,
Broomfield, southeastern Larimer, Gilpin, northern Jefferson,
northwestern Adams and Boulder Counties through 245 PM MDT...

At 221 PM MDT, Doppler radar was tracking strong thunderstorms along
a line extending from 3 miles southeast of Buckhorn Mountain to near
Idledale, or along a line extending from 10 miles west of Fort
Collins to 16 miles west of Denver. Movement was east at 35 mph.

HAZARD...Winds in excess of 40 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...
Southern Fort Collins, Thornton, Arvada, Westminster, Boulder,
Longmont, Loveland, Broomfield, northwestern Commerce City,
Northglenn, Lafayette, Windsor, Louisville, Erie, Superior, Federal
Heights, Firestone, Johnstown, Frederick and Estes Park.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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.

A Severe Thunderstorm Watch remains in effect until 1100 PM MDT for
central, north central and northeastern Colorado.

&&

LAT...LON 4054 10486 3981 10487 3981 10565 4055 10567
TIME...MOT...LOC 2021Z 257DEG 31KT 4059 10527 3969 10526

MAX HAIL SIZE...0.50 IN
MAX WIND GUST...40 MPH

RPK

The office that day

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

IssuedProductOfficeCountiesLasted
Jul 3, 7:00 PM MDTSpecial Weather StatementBOUWeld45 min
Jul 4, 12:44 PM MDTSpecial Weather StatementBOULarimer31 min
Jul 4, 12:47 PM MDTSpecial Weather StatementBOUDouglas28 min
Jul 4, 1:00 PM MDTSevere Thunderstorm WarningBOUGrand30 min
Jul 4, 1:11 PM MDTSpecial Weather StatementBOULarimer34 min
Jul 4, 1:17 PM MDTSevere Thunderstorm WarningBOUGrand28 min
Jul 4, 1:36 PM MDTSpecial Weather StatementBOULarimer24 min
Jul 4, 1:43 PM MDTSpecial Weather StatementBOUBoulder, Gilpin32 min
Jul 4, 2:00 PM MDTSevere Thunderstorm WarningBOUWeld30 min
Jul 4, 2:13 PM MDTSevere Thunderstorm Warning Considerable damage threatBOUWeld47 min
Jul 4, 2:38 PM MDTAreal Flood AdvisoryBOULarimer3 hr
Jul 4, 2:42 PM MDTSevere Thunderstorm WarningBOUWeld33 min
Jul 4, 3:40 PM MDTSpecial Weather StatementBOULogan35 min
Jul 4, 4:05 PM MDTSpecial Weather StatementBOUGrand25 min
Jul 4, 4:31 PM MDTSpecial Weather StatementBOUJackson29 min
Jul 4, 4:52 PM MDTSevere Thunderstorm WarningBOUJackson23 min
Jul 4, 5:14 PM MDTSevere Thunderstorm WarningBOUJackson, Larimer31 min
Jul 4, 5:19 PM MDTSpecial Weather StatementBOUBoulder26 min
Jul 4, 5:36 PM MDTSevere Thunderstorm Warning Considerable damage threatBOULarimer24 min

Nearby

Special Weather Statements in Colorado, 2023Every special weather statement 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.