Alert archive / Montana / Special Weather Statements in 2021

Special Weather Statement, NWS Great Falls, MT

July 1, 2021

NWS Great Falls, MT issued this special weather statement at Jul 1, 2021, 3:37 PM MDT. It was in force for 23 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 1, 2021, 3:37 PM MDT (21:37 UTC)
Expired: Jul 1, 2021, 4:00 PM MDT
In force: 23 min
Issued by: NWS Great Falls, MT

The radar

The Pocatello radar (KSFX), 220 km from the middle of the area, began a volume at 21:38 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

Riverton, WY (KRIW), launched 12:00Z, 9.6 hours before the alert went out and 291 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: 2 J/kg
Mixed-layer CIN: -177 J/kg
Mixed-layer LCL: 2345 m above ground
0-6 km bulk shear: 10 kt
0-1 km storm-relative helicity: 2 m²/s²
0-3 km storm-relative helicity: 10 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

<!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>

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 Great Falls, MT wrote its last area forecast discussion before this special weather statement went out at Jul 1, 3:35 PM MDT, 2 minutes earlier.

Area forecast discussion, Jul 1, 3:35 PM MDT, 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>

In the hours before

Special weather statement, Jul 1, 2:54 PM MDT, 43 minutes before

Special Weather Statement
National Weather Service Great Falls MT
254 PM MDT Thu Jul 1 2021

MTZ052-012145-
Jefferson-
254 PM MDT Thu Jul 1 2021

...A STRONG THUNDERSTORM WILL AFFECT SOUTHWESTERN JEFFERSON COUNTY...

At 253 PM MDT, a strong thunderstorm was located 7 miles northeast of
Walkerville, or 9 miles northeast of Butte, moving northwest at 15
mph.

Winds in excess of 30 mph and pea size hail are possible with this
storm.

Locations impacted include...
Elk Park.

This includes Interstate 15 between mile markers 134 and 152.

Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

Torrential rainfall is also occurring with this storm, and may cause
localized flooding. Do not drive your vehicle through flooded
roadways.

This storm may intensify, so be certain to monitor local radio
stations and available television stations for additional information
and possible warnings from the National Weather Service.

To report severe weather, contact your nearest law enforcement
agency. They can relay your report to the National Weather Service
office in Great Falls.

LAT...LON 4633 11254 4635 11249 4633 11246 4639 11240
      4597 11217 4590 11233 4596 11244 4602 11244
      4605 11248 4608 11246 4613 11252 4618 11251
      4617 11256 4623 11260
TIME...MOT...LOC 2053Z 146DEG 14KT 4609 11240

TPP

Special weather statement, Jul 1, 3:37 PM MDT, 0 minutes before

Special Weather Statement
National Weather Service Great Falls MT
337 PM MDT Thu Jul 1 2021

MTZ055-012200-
Gallatin-
337 PM MDT Thu Jul 1 2021

...A STRONG THUNDERSTORM WILL AFFECT SOUTH CENTRAL GALLATIN COUNTY...

At 336 PM MDT, a strong thunderstorm was located 7 miles northwest of
West Yellowstone. The storm is nearly stationary.

Winds in excess of 30 mph are possible with this storm.

Locations impacted include...
Yellowstone Village.

This includes the following highways...
 Highway 191 between mile markers 2 and 11.
 Highway 287 between mile markers 15 and 22.

If outdoors, consider seeking shelter inside a building.

If you are on or near Hebgen Lake, get out of the water and move
indoors or inside a vehicle. Remember, lightning can strike out to
10 miles from the parent thunderstorm. If you can hear thunder, you
are close enough to be struck by lightning. Move to safe shelter
now! Do not be caught on the water in a thunderstorm.

LAT...LON 4481 11128 4487 11110 4475 11109 4470 11110
      4469 11110 4468 11126
TIME...MOT...LOC 2136Z 090DEG 4KT 4475 11119

CMC

The office that day

Everything else NWS Great Falls, MT issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jul 1, 2:54 PM MDT	Special Weather Statement	TFX	Jefferson	51 min

Nearby

Special Weather Statements in Montana, 2021 Every 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.