Alert archive / Idaho / Areal Flood Advisories in 2021

Areal Flood Advisory 13, NWS Pocatello, ID

July 31, 2021Bannock County, Idaho

NWS Pocatello, ID issued this areal flood advisory at Jul 31, 2021, 1:08 PM MDT for Bannock County, Idaho. It was in force for 112 min.

The area

The counties it named.

The facts

Issued: Jul 31, 2021, 1:08 PM MDT (19:08 UTC)
Expired: Jul 31, 2021, 3:00 PM MDT
In force: 112 min
Issued by: NWS Pocatello, ID
Area: Storm-based polygon

County Bannock County, ID

The radar

The Pocatello radar (KSFX), 61 km from the middle of the area, began a volume at 19:09 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

Salt Lake City I, UT (KSLC), launched 12:00Z, 7.1 hours before the alert went out and 212 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: 149 J/kg
Mixed-layer CIN: -128 J/kg
Mixed-layer LCL: 1716 m above ground
0-6 km bulk shear: 5 kt
0-1 km storm-relative helicity: 44 m²/s²
0-3 km storm-relative helicity: 76 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 Pocatello, ID wrote its last area forecast discussion before this areal flood advisory went out at Jul 31, 1:03 PM MDT, 5 minutes earlier.

Area forecast discussion, Jul 31, 1:03 PM MDT, 5 minutes before

Area Forecast Discussion
National Weather Service Pocatello ID
103 PM MDT Sat Jul 31 2021

.SHORT TERM...A band of showers and thunderstorms from last
night's activity is moving northward. We saw some impressive
rainfall amounts even with that band early this morning. Some
areas around Idaho Falls received close to an inch of rain this
morning.

A low pressure system over southeast Oregon is moving northward.
This low is interacting with the extremely high amount of moisture
across the region to produce scattered thunderstorms once again this
afternoon. Precipitable water values are roughly around 1.25", maybe
higher, which is 2 to 3 times above normal. So, heavy rain and
localized flooding will remain a threat through the weekend.
Greatest risk is across the high country and areas of the Snake
Plain/Magic Valley that are close to the hills/mountains. Flash
flood watches continue through Monday for the high country as the
low pressure system slowly works northward. Eventually departing the
region late Monday.

13

.LONG TERM...Tuesday through Saturday. High pressure begins to
slowly rebuild by the middle of next week. We should see deeper
monsoon moisture being pushed east, but lingering moisture will
likely produce some showers and thunderstorms. With moisture
starting to wane somewhat, we should go back to a mix of wet and dry
storms. A couple of storms pass to our north, trying to produce
showers and storms especially closer to the Montana border for the
latter half of next week. Farther south, a drying trend should
continue...but we may see strong winds developing. Keyes

&&

.AVIATION...Off and on showers and thunderstorms are forecast
through tomorrow. MVFR/IFR weather is possible due to heavy rain
reducing visibility. Gusty winds over 30kts are possible and even
small hail. TAFs will carry VCSH/VCTS and will be amended as short
trends develop in real-time. Keyes

&&

.FIRE WEATHER...Continued moist/humid sub-tropical pattern remains
for East Idaho through the weekend into the early part of the week.
Showers and thunderstorms are expected to remain a continued threat,
and heavy rain is the main concern with potential for flash
flooding/debris flows in steeper terrain/burn scars. Outflow winds
around 35 mph will be possible, but the main threat and concern is
the heavy rain. Flash flood watch remains in effect for most terrain-
based areas in East Idaho through Monday. Upper ridge builds through
the Great Basin Tuesday and Wednesday, which should shunt the deep
monsoonal flow to the east. Lingering showers and storms are still
possible, but likely being a mix of wet and dry storms. DMH/Keyes

&&

.PIH WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch through Monday evening for IDZ056>064-069-
071>074.

&&

In the hours before

Local storm report, Jul 31, 9:11 AM MDT, 3 hours 57 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, Jul 31, 10:47 AM MDT, 2 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>

Special weather statement, Jul 31, 12:20 PM MDT, 48 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 Pocatello, ID issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jul 31, 8:46 AM MDT	Areal Flood Advisory	PIH	Bingham, Bonneville, Jefferson	119 min
Jul 31, 12:20 PM MDT	Special Weather Statement	PIH	Power	40 min
Jul 31, 1:08 PM MDT	Areal Flood Advisory	PIH	Power	29 min
Jul 31, 1:37 PM MDT	Flash Flood Warning	PIH	Power	2 hr
Jul 31, 1:46 PM MDT	Areal Flood Advisory	PIH	Bannock, Power	119 min
Jul 31, 1:55 PM MDT	Areal Flood Advisory	PIH	Bear Lake	2 hr
Jul 31, 2:04 PM MDT	Areal Flood Advisory	PIH	Caribou	3 hr
Jul 31, 2:16 PM MDT	Areal Flood Advisory	PIH	Bear Lake, Franklin	3 hr
Jul 31, 2:28 PM MDT	Areal Flood Advisory	PIH	Bannock, Oneida, Power	3 hr
Jul 31, 2:38 PM MDT	Special Weather Statement	PIH	Bear Lake	37 min
Jul 31, 3:01 PM MDT	Areal Flood Advisory	PIH	Caribou	6 min
Jul 31, 3:07 PM MDT	Flash Flood Warning	PIH	Caribou	113 min
Jul 31, 3:10 PM MDT	Areal Flood Advisory	PIH	Bingham	3 hr
Jul 31, 3:20 PM MDT	Special Weather Statement	PIH	Bonneville	25 min
Jul 31, 3:32 PM MDT	Areal Flood Advisory	PIH	Bannock	3 hr
Jul 31, 3:50 PM MDT	Flash Flood Warning	PIH	Power	77 min
Jul 31, 4:02 PM MDT	Areal Flood Advisory	PIH	Cassia	118 min
Jul 31, 4:06 PM MDT	Areal Flood Advisory	PIH	Bannock, Franklin, Oneida	3 hr
Jul 31, 4:42 PM MDT	Flash Flood Warning	PIH	Bannock, Franklin, Oneida	2 hr
Jul 31, 5:14 PM MDT	Areal Flood Advisory	PIH	Franklin	2 hr
Jul 31, 5:45 PM MDT	Areal Flood Advisory	PIH	Cassia	64 min

Nearby

Areal Flood Advisories in Idaho, 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.