Alert archive / Colorado / Flash Flood Watches in 2018

Flash Flood Watch 5, NWS Denver/Boulder, CO

July 25, 201813 counties in Colorado

NWS Denver/Boulder, CO issued this flash flood watch at Jul 25, 2018, 10:41 AM MDT for 13 counties in Colorado. It took effect at Jul 25, 2018, 2:00 PM MDT. It was in force for 7 hr.

The area

The counties it named.

The facts

Issued: Jul 25, 2018, 10:41 AM MDT (16:41 UTC)
In effect from: Jul 25, 2018, 2:00 PM MDT
Expired: Jul 25, 2018, 9:16 PM MDT
In force: 7 hr
Issued by: NWS Denver/Boulder, CO
Flood severity: None

Counties Adams County, CO, Arapahoe County, CO, Boulder County, CO, Broomfield County, CO, Denver County, CO, Douglas County, CO, Elbert County, CO, Jefferson County, CO, Larimer County, CO, Logan County, CO, Morgan County, CO, Washington County, CO, Weld County, CO

The radar

The Denver radar (KFTG), 22 km from the middle of the area, began a volume at 16:44 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

Denver, CO (KDEN), launched 12:00Z, 4.7 hours before the alert went out and 107 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: 20 J/kg
Mixed-layer CIN: -431 J/kg
Mixed-layer LCL: 2245 m above ground
0-6 km bulk shear: 24 kt
0-1 km storm-relative helicity: 87 m²/s²
0-3 km storm-relative helicity: 74 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 flash flood watch 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 flash flood watch went out at Jul 25, 10:28 AM MDT, 13 minutes earlier.

Area forecast discussion, Jul 25, 10:28 AM MDT, 13 minutes before

<!doctype html>
<html lang="en">
<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.
      </p>
      <p class="small" id="detail">
        If you are an administrator, restore upstream service and remove the redirect/fallback rule when normal operations resume.
      </p>
    </section>
  </main>
  <script src="index.js"></script>
</body>
</html>

Hazardous weather outlook, Jul 25, 6:04 AM MDT, 4 hours 37 minutes before

<!doctype html>
<html lang="en">
<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.
      </p>
      <p class="small" id="detail">
        If you are an administrator, restore upstream service and remove the redirect/fallback rule when normal operations resume.
      </p>
    </section>
  </main>
  <script src="index.js"></script>
</body>
</html>

In the hours before

Local storm report, Jul 25, 9:42 AM MDT, 59 minutes before

<!doctype html>
<html lang="en">
<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.
      </p>
      <p class="small" id="detail">
        If you are an administrator, restore upstream service and remove the redirect/fallback rule when normal operations resume.
      </p>
    </section>
  </main>
  <script src="index.js"></script>
</body>
</html>

The office that day

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

Issued	Product	Office	Counties	Lasted
Jul 24, 6:13 PM MDT	Areal Flood Advisory	BOU	Arapahoe, Denver, Douglas, Jefferson	32 min
Jul 24, 6:28 PM MDT	Severe Thunderstorm Warning	BOU	Adams, Arapahoe, Denver, Douglas	46 min
Jul 24, 6:41 PM MDT	Flash Flood Warning	BOU	Adams, Arapahoe, Denver	2 hr
Jul 24, 7:22 PM MDT	Severe Thunderstorm Warning	BOU	Weld	38 min
Jul 24, 7:35 PM MDT	Severe Thunderstorm Warning	BOU	Morgan	40 min
Jul 24, 7:55 PM MDT	Severe Thunderstorm Warning	BOU	Logan, Morgan, Weld	50 min
Jul 24, 8:12 PM MDT	Severe Thunderstorm Warning	BOU	Logan, Morgan, Washington	48 min
Jul 24, 8:15 PM MDT	Severe Thunderstorm Warning	BOU	Morgan	45 min
Jul 24, 8:41 PM MDT	Severe Thunderstorm Warning	BOU	Logan, Washington	49 min
Jul 24, 8:47 PM MDT	Areal Flood Advisory	BOU	Logan, Morgan, Washington, Weld	2 hr
Jul 24, 9:10 PM MDT	Severe Thunderstorm Warning	BOU	Morgan	50 min
Jul 24, 9:27 PM MDT	Flash Flood Warning	BOU	Morgan	3 hr
Jul 25, 3:10 PM MDT	Special Weather Statement	BOU	Larimer	50 min
Jul 25, 3:43 PM MDT	Special Weather Statement	BOU	Jefferson	47 min
Jul 25, 3:49 PM MDT	Special Weather Statement	BOU	Weld	41 min
Jul 25, 4:04 PM MDT	Areal Flood Advisory	BOU	Larimer, Weld	102 min
Jul 25, 4:31 PM MDT	Severe Thunderstorm Warning	BOU	Weld	44 min
Jul 25, 5:16 PM MDT	Severe Thunderstorm Warning	BOU	Logan, Morgan, Weld	17 min

Nearby

Flash Flood Watches in Colorado, 2018 Every flash flood watch in 2018

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.