Alert archive / Colorado / Areal Flood Advisories in 2021

Areal Flood Advisory 28, NWS Denver/Boulder, CO

June 25, 20214 counties in Colorado

NWS Denver/Boulder, CO issued this areal flood advisory at Jun 25, 2021, 7:16 PM MDT for 4 counties in Colorado. It was in force for 89 min.

The area

The counties it named.

The facts

Issued
Jun 25, 2021, 7:16 PM MDT (01:16 UTC)
Expired
Jun 25, 2021, 8:45 PM MDT
In force
89 min
Issued by
NWS Denver/Boulder, CO
Area
Storm-based polygon

Counties Arapahoe County, CO, Denver County, CO, Douglas County, CO, Jefferson County, CO

The radar

The Denver radar (KFTG), 34 km from the middle of the area, began a volume at 01:16 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 00:00Z, 1.3 hours before the alert went out and 399 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, N. Platte/Lee Bi, NE at 00:00Z on 2021-06-26Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 494 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, N. Platte/Lee Bi, NE at 00:00Z on 2021-06-26The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 6 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
494 J/kg
Mixed-layer CIN
-6 J/kg
Mixed-layer LCL
914 m above ground
0-6 km bulk shear
36 kt
0-1 km storm-relative helicity
6 m²/s²
0-3 km storm-relative helicity
65 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.3

Open this sounding in Storm Lab

What forecasters said that day

The local office's own words before this areal flood advisory 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 areal flood advisory went out at Jun 25, 3:12 PM MDT, 4 hours 4 minutes earlier.

Area forecast discussion, Jun 25, 3:12 PM MDT, 4 hours 4 minutes before
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Hazardous weather outlook, Jun 25, 10:56 AM MDT, 8 hours 20 minutes before
Hazardous Weather Outlook
National Weather Service Denver/Boulder CO
1056 AM MDT Fri Jun 25 2021

COZ030>051-261700-
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-
1056 AM MDT Fri Jun 25 2021

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

.DAY ONE...Today and Tonight

Scattered thunderstorms have already developed over northern
Larimer and Weld counties this morning. They are also just
beginning to develop over the higher terrain. Showers and
thunderstorms are likely across most of the forecast area from
mid afternoon well into the evening hours. Some of the storms
could produce wind gusts up to 60 mph and one inch hail east of a
line from Fort Morgan to Monument Hill. Multiple rounds of showers
and thunderstorms are expected over the burn areas. They could
produce flash flooding, but major flash flood is not expected at
this time. Some showers and thunderstorms will linger across the
plains overnight.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday

Saturday will remain cool with a good chance of showers and a few
storms, mainly over the higher terrain. There will be a limited
threat for flash flooding, mainly in the East Troublesome and
Williams Fork burn areas.

For Sunday and Monday, scattered showers and a few storms are
expected with cloudy and cool conditions. The threat of flash
flooding in the burn areas will be low both days.

.SPOTTER INFORMATION STATEMENT...

Spotter activation will not be needed.

In the hours before

Special weather statement, Jun 25, 2:35 PM MDT, 4 hours 41 minutes before
Special Weather Statement
National Weather Service Denver CO
235 PM MDT Fri Jun 25 2021

COZ041-047-252115-
Elbert/Central and East Douglas Counties Above 6000 Feet CO-
Southeast Elbert County Below 6000 Feet/South Lincoln County CO-
235 PM MDT Fri Jun 25 2021

...SPECIAL WEATHER STATEMENT...

At 235 PM MDT, Doppler radar was tracking a strong thunderstorm 6
miles southeast of Simla, or 21 miles southwest of Limon, moving east
at 10 mph.

Half inch hail and winds in excess of 30 mph will be possible with
this storm.

This storm will remain over mainly rural areas of southeastern Elbert
County.

LAT...LON 3914 10405 3915 10400 3914 10400 3913 10395
      3915 10393 3915 10391 3916 10390 3916 10389
      3914 10390 3913 10389 3910 10389 3910 10384
      3898 10385 3898 10405
TIME...MOT...LOC 2035Z 275DEG 9KT 3907 10399

ENTREKIN
Special weather statement, Jun 25, 2:50 PM MDT, 4 hours 26 minutes before
Special Weather Statement
National Weather Service Denver CO
250 PM MDT Fri Jun 25 2021

COZ036-039-040-043-252130-
Central and South Weld County CO-
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-
Jefferson and West Douglas Counties Above  6000 Feet/Gilpin/Clear
Creek/Northeast Park Counties Below 9000 Feet CO-
250 PM MDT Fri Jun 25 2021

...SIGNIFICANT WEATHER ADVISORY FOR SOUTHWESTERN WELD...BROOMFIELD...
NORTHERN JEFFERSON...NORTHWESTERN ADAMS AND SOUTHEASTERN BOULDER
COUNTIES UNTIL 330 PM MDT...

At 250 PM MDT, Doppler radar was tracking a strong thunderstorm near
Rocky Flats, or 20 miles northwest of Denver, moving east at 15 mph.

Half inch hail, heavy rain, and winds in excess of 40 mph will be
possible with this storm.

Locations impacted include...
Northwestern Denver, Thornton, Arvada, Westminster, southeastern
Boulder, Broomfield, northwestern Commerce City, Northglenn,
Brighton, northeastern Wheat Ridge, Lafayette, Louisville, Erie,
Superior, Federal Heights, Frederick, Fort Lupton, Dacono, Rocky
Flats and Eldorado Springs.

LAT...LON 4008 10470 3976 10501 3984 10538 3992 10532
      3992 10523 3993 10524 3993 10528 3994 10527
      3997 10527 4010 10516
TIME...MOT...LOC 2050Z 275DEG 15KT 3989 10527

ENTREKIN
Special weather statement, Jun 25, 2:57 PM MDT, 4 hours 19 minutes before
Special Weather Statement
National Weather Service Denver CO
257 PM MDT Fri Jun 25 2021

COZ043-252145-
Central and South Weld County CO-
257 PM MDT Fri Jun 25 2021

...SIGNIFICANT WEATHER ADVISORY FOR SOUTHWESTERN WELD COUNTY UNTIL
345 PM MDT...

At 257 PM MDT, Doppler radar was tracking a strong thunderstorm near
Johnstown, or 11 miles southwest of Greeley, moving southeast at 20
mph.

Penny size hail, heavy rain, and winds in excess of 30 mph will be
possible with this storm.

Locations impacted include...
Greeley, Windsor, Evans, Johnstown, Fort Lupton, Milliken, Berthoud,
Mead, Platteville, LaSalle, Kersey, Gilcrest and Milton Reservoir.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 4036 10441 4009 10476 4029 10503 4035 10500
      4035 10495 4046 10495 4046 10494
TIME...MOT...LOC 2057Z 302DEG 19KT 4031 10491

ENTREKIN
Local storm report, Jun 25, 3:04 PM MDT, 4 hours 12 minutes before
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DENVER CO
304 PM MDT FRI JUN 25 2021

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0239 PM     FLASH FLOOD      5 WNW MASONVILLE        40.51N 105.29W
06/25/2021                   LARIMER            CO   911 CALL CENTER

            BUCKHORN ROAD SOUTH OF BIG BEAR ROAD CITIZEN REPORTED
            WATER RUNNING 5 TO 6 INCHES DEEP AND GROWING RAPIDLY.

0200 PM     HAIL             4 WNW BOULDER           40.04N 105.32W
06/25/2021  M1.00 INCH       BOULDER            CO   TRAINED SPOTTER

&&
Special weather statement, Jun 25, 3:10 PM MDT, 4 hours 6 minutes before
Special Weather Statement
National Weather Service Denver CO
310 PM MDT Fri Jun 25 2021

COZ048-049-051-252200-
Phillips County CO-Washington County CO-Logan County CO-
310 PM MDT Fri Jun 25 2021

...SPECIAL WEATHER STATEMENT...

At 309 PM MDT, Doppler radar was tracking a strong thunderstorm 4
miles northwest of St Petersburg, or 16 miles east of Sterling,
moving east at 10 mph.

Half inch hail and winds in excess of 30 mph will be possible with
this storm.

Locations impacted include...
Akron, Haxtun, Otis, Fleming, Paoli, St Petersburg, Highland Center,
Burdett, Platner and Lone Star.

A Severe Thunderstorm Watch remains in effect until 800 PM MDT for
northeastern Colorado.

LAT...LON 4045 10215 4046 10279 3996 10281 3999 10333
      4081 10274
TIME...MOT...LOC 2109Z 260DEG 9KT 4058 10289

ENTREKIN
Special weather statement, Jun 25, 3:24 PM MDT, 3 hours 52 minutes before
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The office that day

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

IssuedProductOfficeCountiesLasted
Jun 26, 1:06 PM MDTAreal Flood AdvisoryBOUBoulder84 min

Nearby

Areal Flood Advisories in Colorado, 2021Every areal flood advisory in 2021

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.