Alert archive / Montana / Severe Thunderstorm Warnings in 2021

Severe Thunderstorm Warning 64, NWS Great Falls, MT

December 23, 20215 counties in Montana

NWS Great Falls, MT issued this severe thunderstorm warning at Dec 23, 2021, 6:50 PM MST for 5 counties in Montana. It was in force for 40 min. 1 report came from inside the area while it was in force.

The area

The outline as issued, with what was reported inside it.

The facts

Issued: Dec 23, 2021, 6:50 PM MST (01:50 UTC)
Expired: Dec 23, 2021, 7:30 PM MST
In force: 40 min
Issued by: NWS Great Falls, MT
Area: Storm-based polygon
Hail: 0.75 in
Wind: 60.0 mph

Counties Cascade County, MT, Chouteau County, MT, Fergus County, MT, Hill County, MT, Judith Basin County, MT

The radar

The Great Falls radar (KTFX), 94 km from the middle of the area, began a volume at 01:51 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.

What was reported inside it

Time	Report	Where	Remark
Dec 23, 6:58 PM MST	TSTM WND GST 58	3 Wnw Raynesford, MT	AWOS STATION K1AM ALPHA.

Local storm reports filed while the alert was in force, from inside its polygon or its counties.

The nearest sounding before it

Great_falls, MT (KTFX), launched 00:00Z, 1.8 hours before the alert went out and 39 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: 0 J/kg
Mixed-layer CIN: No buoyant parcel
Mixed-layer LCL: 1573 m above ground
0-6 km bulk shear: 60 kt
0-1 km storm-relative helicity: 194 m²/s²
0-3 km storm-relative helicity: 275 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

571 
WUUS55 KTFX 240150
SVRTFX
MTC013-015-027-041-045-240230-
/O.NEW.KTFX.SV.W.0064.211224T0150Z-211224T0230Z/

BULLETIN - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Warning
National Weather Service Great Falls MT
650 PM MST Thu Dec 23 2021

The National Weather Service in Great Falls has issued a

* Severe Thunderstorm Warning for...
  Northern Judith Basin County in central Montana...
  Northwestern Fergus County in central Montana...
  Southeastern Hill County in north central Montana...
  Central Chouteau County in north central Montana...
  Northeastern Cascade County in central Montana...

* Until 730 PM MST.

* At 648 PM MST, severe thunderstorms were located along a line
  extending from near Big Sandy to 9 miles southwest of Fort Benton
  to 9 miles south of Belt, moving east at 60 mph.

  HAZARD...60 mph wind gusts.

  SOURCE...Radar indicated.

  IMPACT...Expect damage to roofs, siding, and trees.

* Locations impacted include...
  Fort Benton, Big Sandy, Stanford, Belt, Geraldine, Denton, Parker
  School, Agency, St. Pierre, Geyser, Highwood, Raynesford, Rocky
  Boy, Sluice Boxes State Park, Shonkin, Loma, Coffee Creek,
  Armington, Square Butte and Iliad.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

For your protection move to an interior room on the lowest floor of a
building.

Wind damage with these storms will occur before any rain or
lightning. Do not wait for the sound of thunder before taking cover.
SEEK SHELTER IMMEDIATELY inside a sturdy structure and stay away from
windows.

&&

LAT...LON 4714 10982 4716 11101 4765 11096 4822 11022
      4828 10956 4784 10969
TIME...MOT...LOC 0148Z 255DEG 52KT 4817 11022 4774 11080 4725 11090 

HAIL THREAT...RADAR INDICATED
MAX HAIL SIZE...<.75 IN
WIND THREAT...RADAR INDICATED
MAX WIND GUST...60 MPH

$$

CMC

The office that day

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

Issued	Product	Office	Counties	Lasted
Dec 23, 6:11 PM MST	Severe Thunderstorm Warning	TFX	Cascade, Chouteau	34 min
Dec 23, 6:34 PM MST	Snow Squall Warning	TFX	Cascade, Chouteau, Hill, Judith Basin	56 min
Dec 23, 7:30 PM MST	Severe Thunderstorm Warning	TFX	Blaine, Chouteau, Fergus, Judith Basin	60 min
Dec 24, 1:58 AM MST	Winter Storm Watch	TFX		12 hr

Nearby

Severe Thunderstorm Warnings in Montana, 2021 Every severe thunderstorm warning 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; local storm reports from the same archive; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.