Alert archive / Iowa / Flash Flood Warnings in 2024

Flash Flood Warning 10, NWS Omaha, NE

May 20, 2024Shelby County, Iowa

NWS Omaha, NE issued this flash flood warning at May 20, 2024, 9:51 PM CDT for Shelby County, Iowa. It was in force for 5 hr. No storm report in the archive falls inside the area while it was in force.

The area

The counties it named.

The facts

Issued: May 20, 2024, 9:51 PM CDT (02:51 UTC)
Expired: May 21, 2024, 3:00 AM CDT
In force: 5 hr
Issued by: NWS Omaha, NE
Area: Storm-based polygon
Flood severity: None

County Shelby County, IA

The radar

The Omaha radar (KOAX), 97 km from the middle of the area, began a volume at 02:52 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

Omaha, NE (KOAX), launched 00:00Z, 2.9 hours before the alert went out and 97 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: 1458 J/kg
Mixed-layer CIN: -29 J/kg
Mixed-layer LCL: 1666 m above ground
0-6 km bulk shear: 34 kt
0-1 km storm-relative helicity: 18 m²/s²
0-3 km storm-relative helicity: 55 m²/s²
Significant tornado parameter: 0.1
Supercell composite: 2.3

Open this sounding in Storm Lab

What forecasters said that day

The local office's own words before this flash flood warning went out, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS Omaha, NE wrote its last area forecast discussion before this flash flood warning went out at May 20, 6:30 PM CDT, 3 hours 21 minutes earlier.

Area forecast discussion, May 20, 6:30 PM CDT, 3 hours 21 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, May 20, 3:46 PM CDT, 6 hours 5 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, May 20, 8:13 PM CDT, 1 hour 38 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>

Local storm report, May 20, 9:11 PM CDT, 40 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>

Local storm report, May 20, 9:39 PM CDT, 12 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>

Local storm report, May 20, 9:40 PM CDT, 11 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>

Local storm report, May 20, 9:43 PM CDT, 8 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>

Local storm report, May 20, 9:49 PM CDT, 2 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 Omaha, NE issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
May 20, 7:35 PM CDT	Severe Thunderstorm Warning	OAX	Butler, Lancaster, Saunders, Seward	40 min
May 20, 7:56 PM CDT	Severe Thunderstorm Warning	OAX	Lancaster, Saunders	45 min
May 20, 8:14 PM CDT	Severe Thunderstorm Warning	OAX	Knox	46 min
May 20, 8:51 PM CDT	Severe Thunderstorm Warning	OAX	Cedar, Knox	39 min
May 20, 8:57 PM CDT	Severe Thunderstorm Warning	OAX	Butler, Saunders	63 min
May 20, 9:08 PM CDT	Severe Thunderstorm Warning	OAX	Burt, Washington	52 min
May 20, 9:24 PM CDT	Severe Thunderstorm Warning	OAX	Cedar	51 min
May 20, 9:53 PM CDT	Severe Thunderstorm Warning	OAX	Butler, Saunders, Seward	67 min
May 20, 10:06 PM CDT	Severe Thunderstorm Warning	OAX	Burt, Cuming, Thurston	39 min
May 20, 10:17 PM CDT	Areal Flood Advisory	OAX	Butler, Saunders	9 hr
May 20, 10:28 PM CDT	Areal Flood Advisory	OAX	Butler, Lancaster, Saunders, Seward	2 hr
May 20, 10:54 PM CDT	Severe Thunderstorm Warning	OAX	Douglas, Sarpy, Saunders	66 min
May 20, 11:09 PM CDT	Severe Thunderstorm Warning	OAX	Cedar	36 min
May 20, 11:12 PM CDT	Flash Flood Warning	OAX	Douglas, Sarpy	3 hr
May 20, 11:14 PM CDT	Tornado Warning	OAX	Washington	28 min
May 20, 11:23 PM CDT	Severe Thunderstorm Warning Considerable damage threat	OAX	Douglas, Sarpy, Washington	67 min
May 20, 11:49 PM CDT	Areal Flood Advisory	OAX	Washington	93 min
May 21, 12:45 AM CDT	Severe Thunderstorm Warning	OAX	Butler, Colfax, Dodge, Saunders	22 min
May 21, 1:35 AM CDT	Severe Thunderstorm Warning	OAX	Burt, Dodge, Washington	24 min
May 21, 2:38 AM CDT	Flash Flood Warning	OAX	Burt, Washington	5 hr
May 21, 2:54 AM CDT	Flash Flood Warning	OAX	Dodge	4 hr
May 21, 4:19 AM CDT	Areal Flood Advisory	OAX	Butler, Colfax, Dodge, Saunders	3 hr
May 21, 4:31 AM CDT	Severe Thunderstorm Warning	OAX	Boone, Butler, Madison, Platte, Stanton	44 min
May 21, 4:39 AM CDT	River Flood Warning	OAX	Saunders	40 hr
May 21, 4:42 AM CDT	Severe Thunderstorm Warning	OAX	Saunders	48 min
May 21, 4:43 AM CDT	Flash Flood Warning	OAX	Butler, Saunders	5 hr
May 21, 4:47 AM CDT	Severe Thunderstorm Warning	OAX	Antelope, Boone, Madison, Pierce, Platte	28 min
May 21, 5:00 AM CDT	Severe Thunderstorm Warning Considerable damage threat	OAX	Butler, Colfax, Cuming, Dodge, Platte, Saunders	45 min
May 21, 5:02 AM CDT	River Flood Warning	OAX	Saunders	37 hr
May 21, 5:03 AM CDT	Severe Thunderstorm Warning Considerable damage threat	OAX	Butler, Lancaster, Saline, Saunders, Seward	42 min
May 21, 5:10 AM CDT	Severe Thunderstorm Warning	OAX	Colfax, Cuming, Madison, Platte, Stanton, Wayne	50 min
May 21, 5:12 AM CDT	Severe Thunderstorm Warning	OAX	Dodge, Douglas, Saunders, Washington	48 min
May 21, 5:12 AM CDT	Tornado Warning	OAX	Colfax, Dodge, Platte	33 min
May 21, 5:21 AM CDT	Flash Flood Warning	OAX	Dodge, Douglas, Sarpy, Washington	4 hr
May 21, 5:27 AM CDT	Tornado Warning	OAX	Butler, Colfax, Dodge, Saunders	33 min
May 21, 5:29 AM CDT	Areal Flood Advisory	OAX	Dodge, Douglas, Saunders, Washington	2 hr
May 21, 5:29 AM CDT	Tornado Warning	OAX	Butler, Saunders	31 min
May 21, 5:39 AM CDT	Tornado Warning	OAX	Burt, Cuming, Dodge, Washington	36 min
May 21, 5:41 AM CDT	Severe Thunderstorm Warning Destructive damage threat	OAX	Burt, Cuming, Dodge, Thurston, Washington	49 min
May 21, 5:44 AM CDT	Tornado Warning	OAX	Saunders	7 min
May 21, 5:45 AM CDT	Severe Thunderstorm Warning Considerable damage threat	OAX	Dodge, Douglas, Sarpy, Saunders, Washington	45 min
May 21, 5:46 AM CDT	Areal Flood Advisory	OAX	Burt, Dodge, Douglas, Saunders, Washington	113 min
May 21, 5:49 AM CDT	Severe Thunderstorm Warning Considerable damage threat	OAX	Cuming, Thurston, Wayne	41 min
May 21, 5:53 AM CDT	Severe Thunderstorm Warning	OAX	Douglas, Washington	52 min
May 21, 5:53 AM CDT	Tornado Warning	OAX	Dodge, Douglas, Saunders, Washington	37 min
May 21, 6:15 AM CDT	Severe Thunderstorm Warning Considerable damage threat	OAX	Cass, Douglas, Sarpy, Washington	45 min
May 21, 6:50 AM CDT	Severe Thunderstorm Warning	OAX	Nemaha, Otoe	14 min
May 21, 6:56 AM CDT	Areal Flood Warning	OAX	Dodge	5 hr
May 21, 7:11 AM CDT	Flash Flood Warning	OAX	Washington	4 hr
May 21, 7:33 AM CDT	Areal Flood Warning	OAX	Burt, Butler, Colfax, Dodge, Douglas, Saunders and 1 more	10 hr
May 21, 8:29 AM CDT	River Flood Warning	OAX	Dodge	6 hr
May 21, 9:20 AM CDT	Areal Flood Warning	OAX	Douglas, Sarpy, Washington	8 hr
May 21, 10:03 AM CDT	River Flood Warning	OAX	Cass	55 hr
May 21, 10:03 AM CDT	River Flood Warning	OAX	Otoe	57 hr
May 21, 10:03 AM CDT	River Flood Warning	OAX	Nemaha	4 days
May 21, 10:03 AM CDT	River Flood Warning	OAX	Seward	33 hr
May 21, 11:20 AM CDT	Severe Thunderstorm Warning	OAX	Butler, Lancaster, Seward	40 min
May 21, 11:48 AM CDT	Severe Thunderstorm Warning Considerable damage threat	OAX	Butler, Lancaster, Saunders, Seward	42 min
May 21, 12:16 PM CDT	Severe Thunderstorm Warning Considerable damage threat	OAX	Burt, Dodge, Douglas, Saunders, Washington	44 min
May 21, 12:38 PM CDT	Severe Thunderstorm Warning	OAX	Dodge, Douglas, Saunders, Washington	52 min
May 21, 12:44 PM CDT	Tornado Warning	OAX	Douglas, Saunders	31 min
May 21, 12:45 PM CDT	Severe Thunderstorm Warning	OAX	Gage, Johnson, Otoe	45 min
May 21, 12:50 PM CDT	Tornado Warning	OAX	Dodge, Washington	19 min
May 21, 12:59 PM CDT	Severe Thunderstorm Warning Considerable damage threat	OAX	Burt, Washington	61 min
May 21, 1:01 PM CDT	Severe Thunderstorm Warning	OAX	Cass, Douglas, Sarpy	59 min
May 21, 1:15 PM CDT	Tornado Warning	OAX	Cass, Otoe	45 min
May 21, 1:16 PM CDT	Severe Thunderstorm Warning	OAX	Douglas, Washington	59 min
May 21, 1:34 PM CDT	Severe Thunderstorm Warning	OAX	Cass, Douglas, Sarpy	26 min
May 21, 1:43 PM CDT	Tornado Warning	OAX	Cass, Otoe	47 min
May 21, 5:37 PM CDT	Areal Flood Warning	OAX	Butler, Dodge, Douglas, Saunders, Washington	15 hr
May 20, 8:37 PM CDT	Severe Thunderstorm Warning	OAX	Shelby	68 min
May 20, 9:42 PM CDT	Severe Thunderstorm Warning	OAX	Shelby	48 min
May 20, 11:35 PM CDT	Severe Thunderstorm Warning Considerable damage threat	OAX	Harrison, Pottawattamie, Shelby	40 min
May 21, 12:02 AM CDT	Tornado Warning	OAX	Harrison, Pottawattamie	43 min
May 21, 12:14 AM CDT	Severe Thunderstorm Warning	OAX	Harrison, Pottawattamie, Shelby	46 min
May 21, 12:42 AM CDT	Severe Thunderstorm Warning	OAX	Pottawattamie, Shelby	63 min
May 21, 12:53 AM CDT	Tornado Warning	OAX	Shelby	39 min
May 21, 1:10 AM CDT	Tornado Warning	OAX	Shelby	25 min
May 21, 1:44 AM CDT	Severe Thunderstorm Warning	OAX	Pottawattamie, Shelby	61 min
May 21, 6:11 AM CDT	Severe Thunderstorm Warning Considerable damage threat	OAX	Harrison, Monona, Shelby	49 min

Nearby

Flash Flood Warnings in Iowa, 2024 Every flash flood warning in 2024

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.