Alert archive / Colorado / Areal Flood Advisories in 2021

Areal Flood Advisory 97, NWS Denver/Boulder, CO

July 20, 2021Larimer County, Colorado

NWS Denver/Boulder, CO issued this areal flood advisory at Jul 20, 2021, 4:29 PM MDT for Larimer County, Colorado. It was in force for 91 min.

The area

The counties it named.

The facts

Issued: Jul 20, 2021, 4:29 PM MDT (22:29 UTC)
Expired: Jul 20, 2021, 6:00 PM MDT
In force: 91 min
Issued by: NWS Denver/Boulder, CO
Area: Storm-based polygon

County Larimer County, CO

The radar

The Cheyenne radar (KCYS), 77 km from the middle of the area, began a volume at 22:31 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, 10.5 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-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

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: 2685 m above ground
0-6 km bulk shear: 15 kt
0-1 km storm-relative helicity: -7 m²/s²
0-3 km storm-relative helicity: 31 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 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 Jul 20, 2:59 PM MDT, 1 hour 30 minutes earlier.

Area forecast discussion, Jul 20, 2:59 PM MDT, 1 hour 30 minutes before

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Hazardous weather outlook, Jul 20, 10:34 AM MDT, 5 hours 55 minutes before

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<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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The office that day

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

Issued	Product	Office	Counties	Lasted
Jul 20, 3:27 PM MDT	Areal Flood Advisory	BOU	Grand	78 min
Jul 20, 4:53 PM MDT	Flash Flood Warning	BOU	Larimer	82 min
Jul 20, 5:24 PM MDT	Flash Flood Warning	BOU	Larimer	51 min

Nearby

Areal Flood Advisories in Colorado, 2021 Every 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.