Alert archive / Nebraska / Special Weather Statements in 2021

Special Weather Statement, NWS Cheyenne, WY

July 17, 2021Sioux County, Nebraska

NWS Cheyenne, WY issued this special weather statement at Jul 17, 2021, 4:20 PM MDT for Sioux County, Nebraska. It was in force for 40 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
Jul 17, 2021, 4:20 PM MDT (22:20 UTC)
Expired
Jul 17, 2021, 5:00 PM MDT
In force
40 min
Issued by
NWS Cheyenne, WY

County Sioux County, NE

The radar

The Cheyenne radar (KCYS), 151 km from the middle of the area, began a volume at 22:21 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

Rapid City, SD (KUNR), launched 12:00Z, 10.3 hours before the alert went out and 210 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, Rapid City, SD at 12:00Z on 2021-07-17Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 16 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, Rapid City, SD at 12:00Z on 2021-07-17The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity -64 square meters per square second.193958Sfc1 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
16 J/kg
Mixed-layer CIN
-381 J/kg
Mixed-layer LCL
2689 m above ground
0-6 km bulk shear
30 kt
0-1 km storm-relative helicity
-64 m²/s²
0-3 km storm-relative helicity
-37 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 Cheyenne, WY wrote its last area forecast discussion before this special weather statement went out at Jul 17, 3:03 PM MDT, 1 hour 17 minutes earlier.

Area forecast discussion, Jul 17, 3:03 PM MDT, 1 hour 17 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.
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Hazardous weather outlook, Jul 17, 3:07 PM MDT, 1 hour 13 minutes before
Hazardous Weather Outlook
National Weather Service Cheyenne WY
307 PM MDT Sat Jul 17 2021

NEZ002-003-019>021-054-055-095-096-WYZ101-102-107-108-118-119-
181300-
Dawes County-Box Butte County-Scotts Bluff County-Banner County-
Morrill County-Kimball County-Cheyenne County-
Northern Sioux County-Southern Sioux County-
Converse County Lower Elevations-Niobrara County-
East Platte County-Goshen County-Central Laramie County-
East Laramie County-
307 PM MDT Sat Jul 17 2021

This hazardous weather outlook is for portions of panhandle
Nebraska...east central Wyoming and southeast Wyoming.

.DAY ONE...THIS AFTERNOON AND TONIGHT

Scattered showers and thunderstorms are expected to develop along
the Laramie Range this afternoon, spreading eastward across the
western Nebraska Panhandle through this evening. A few strong to
severe thunderstorms are possible, with large hail and damaging
winds the primary hazard.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY

An isolated shower or thunderstorm will be possible each afternoon
over the next week. Widespread severe weather is not expected.

.Spotter information statement...

Spotter activation is not anticipated.

WYZ103>106-109>117-181300-
North Laramie Range-Ferris/Seminoe/Shirley Mountains-
Shirley Basin-Central Laramie Range and Southwest Platte County-
Central Carbon County-North Snowy Range Foothills-
Southwest Carbon County-Sierra Madre Range-
Upper North Platte River Basin-Snowy Range-Laramie Valley-
South Laramie Range-South Laramie Range Foothills-
307 PM MDT Sat Jul 17 2021

This hazardous weather outlook is for portions of south central
Wyoming and southeast Wyoming.

.DAY ONE...THIS AFTERNOON AND TONIGHT

Isolated showers and thunderstorms are expected this afternoon and
evening. Severe weather is not expected.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY

An isolated shower or thunderstorm will be possible each afternoon
over the next week. Widespread severe weather is not expected.

.Spotter information statement...

Spotter activation will not be needed.

In the hours before

Special weather statement, Jul 17, 4:20 PM MDT, 0 minutes before
Special Weather Statement
National Weather Service Cheyenne WY
420 PM MDT Sat Jul 17 2021

NEZ095-096-WYZ108-172300-
North Sioux NE-South Sioux NE-Goshen County WY-
420 PM MDT Sat Jul 17 2021

...SIGNIFICANT WEATHER ADVISORY FOR SOUTHERN SIOUX AND NORTHEASTERN
GOSHEN COUNTIES UNTIL 500 PM MDT...

At 419 PM MDT, Doppler radar was tracking a strong thunderstorm 8
miles southeast of Prairie Center, or 25 miles north of Torrington,
moving southeast at 50 mph.

Half inch hail and winds in excess of 40 mph will be possible with
this storm.

Locations impacted include...
Agate Bed National Monument.

LAT...LON 4238 10423 4254 10411 4232 10345 4208 10360
TIME...MOT...LOC 2219Z 297DEG 45KT 4243 10408

Mokry

The office that day

Everything else NWS Cheyenne, WY issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Jul 17, 5:25 PM MDTSpecial Weather StatementCYSNiobrara35 min
Jul 16, 6:59 PM MDTSpecial Weather StatementCYSDawes31 min
Jul 16, 7:10 PM MDTSevere Thunderstorm WarningCYSDawes35 min
Jul 16, 7:33 PM MDTSevere Thunderstorm WarningCYSBox Butte, Dawes42 min
Jul 16, 9:31 PM MDTSpecial Weather StatementCYSBox Butte44 min
Jul 17, 4:59 PM MDTSpecial Weather StatementCYSSioux31 min
Jul 17, 5:03 PM MDTSpecial Weather StatementCYSKimball27 min
Jul 17, 5:29 PM MDTSpecial Weather StatementCYSKimball31 min

Nearby

Special Weather Statements in Nebraska, 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.