Alert archive / Colorado / Special Weather Statements in 2021

Special Weather Statement, NWS Denver/Boulder, CO

August 14, 2021Summit County, Colorado

NWS Denver/Boulder, CO issued this special weather statement at Aug 14, 2021, 7:15 PM MDT for Summit 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 outline as issued.

The facts

Issued
Aug 14, 2021, 7:15 PM MDT (01:15 UTC)
Expired
Aug 14, 2021, 7:45 PM MDT
In force
30 min
Issued by
NWS Denver/Boulder, CO
Hail
0.50 in
Wind
40

County Summit County, CO

The radar

The Denver radar (KFTG), 129 km from the middle of the area, began a volume at 01:15 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 00:00Z, 1.3 hours before the alert went out and 218 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 00:00Z on 2021-08-15Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 291 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 00:00Z on 2021-08-15The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 0 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
291 J/kg
Mixed-layer CIN
-63 J/kg
Mixed-layer LCL
3744 m above ground
0-6 km bulk shear
4 kt
0-1 km storm-relative helicity
0 m²/s²
0-3 km storm-relative helicity
-6 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 Aug 14, 3:12 PM MDT, 4 hours 3 minutes earlier.

Area forecast discussion, Aug 14, 3:12 PM MDT, 4 hours 3 minutes before
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<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>Service Notice</title>
  <link rel="stylesheet" href="index.css">
</head>
<body>
  <main class="wrap">
    <section class="card" role="status" aria-live="polite">
      <div class="status" id="status">Temporary Notice</div>
      <h1 id="headline">This service is currently unavailable.</h1>
      <p id="message1">
        The site you requested is temporarily down for maintenance or an unexpected outage.
      </p>
      <p id="message2">
        Please try again in a few minutes.
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        If you are an administrator, restore upstream service and remove the redirect/fallback rule when normal operations resume.
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Hazardous weather outlook, Aug 14, 10:51 AM MDT, 8 hours 24 minutes before
Hazardous Weather Outlook
National Weather Service Denver/Boulder CO
1051 AM MDT Sat Aug 14 2021

COZ030>051-151700-
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-
1051 AM MDT Sat Aug 14 2021

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

.DAY ONE...Today and Tonight

Isolated showers and thunderstorms will be possible during the
late afternoon and evening hours today. Over the far northeast
plains, it is possible that one or two of these storms becomes
severe this evening with large hail being the primary threat.
Storms over the higher terrain will not be terribly strong but
will be slow moving which poses a limited threat of flash
flooding over the burn areas.

.DAYS TWO THROUGH SEVEN...Sunday through Friday

Scattered afternoon and evening showers and thunderstorms are
expected Sunday. Brief heavy rain, small hail, and wind gusts to
50 mph will be possible with the stronger thunderstorms.

Thunderstorms Monday and Tuesday are expected to be isolated and
mainly over the higher terrain. An increase in thunderstorms
should occur Wednesday and Thursday as a storm system moves
across the region.

.SPOTTER INFORMATION STATEMENT...

Spotter activation will not be needed today or tonight.

In the hours before

Special weather statement, Aug 14, 7:15 PM MDT, 0 minutes before
Special Weather Statement
National Weather Service Denver CO
715 PM MDT Sat Aug 14 2021

COZ034-150145-
South and Southeast Grand/West Central and Southwest
Boulder/Gilpin/Clear Creek/Summit/North and West Park Counties Above
9000 Feet CO-
715 PM MDT Sat Aug 14 2021

...A strong thunderstorm will impact portions of east central Summit
County through 745 PM MDT...

At 714 PM MDT, Doppler radar was tracking a strong thunderstorm over
Dillon, or 57 miles west of Denver, moving southeast at 10 mph.

HAZARD...Winds in excess of 40 mph, half inch hail, and very heavy
         rain.

SOURCE...Radar indicated.

IMPACT...Travel on I-70 will be hazardous with very heavy rain and
         small hail. Gusty winds could blow around unsecured
         objects. Minor damage to outdoor objects is possible.

Locations impacted include...
Dillon and Keystone.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

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

&&

LAT...LON 3963 10608 3962 10608 3962 10607 3960 10606
      3961 10605 3962 10606 3963 10606 3965 10607
      3969 10601 3961 10586 3951 10598 3962 10610
TIME...MOT...LOC 0114Z 313DEG 10KT 3963 10601

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

BARJENBRUCH

The office that day

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

IssuedProductOfficeCountiesLasted
Aug 14, 6:48 PM MDTFlash Flood WarningBOULarimer115 min
Aug 14, 7:38 PM MDTSevere Thunderstorm Warning Considerable damage threatBOUWeld52 min
Aug 14, 8:01 PM MDTSevere Thunderstorm Warning Considerable damage threatBOULogan44 min
Aug 14, 8:28 PM MDTSevere Thunderstorm WarningBOUWeld47 min
Aug 14, 8:29 PM MDTSevere Thunderstorm WarningBOUSedgwick46 min
Aug 14, 8:43 PM MDTSevere Thunderstorm Warning Considerable damage threatBOULogan, Washington47 min
Aug 14, 9:15 PM MDTSevere Thunderstorm WarningBOUPhillips, Sedgwick14 min
Aug 14, 9:28 PM MDTSevere Thunderstorm WarningBOULogan, Washington47 min
Aug 14, 9:31 PM MDTSpecial Weather StatementBOUWeld44 min
Aug 15, 2:32 PM MDTAreal Flood AdvisoryBOUGrand88 min
Aug 15, 5:19 PM MDTSpecial Weather StatementBOULincoln41 min
Aug 15, 5:25 PM MDTSpecial Weather StatementBOUTeller65 min

Nearby

Special Weather Statements in Colorado, 2021Every special weather statement 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.