Alert archive / Montana / Severe Thunderstorm Warnings in 2021

Severe Thunderstorm Warning 65, NWS Great Falls, MT

December 23, 20214 counties in Montana

NWS Great Falls, MT issued this severe thunderstorm warning at Dec 23, 2021, 7:30 PM MST for 4 counties in Montana. It was in force for 60 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
Dec 23, 2021, 7:30 PM MST (02:30 UTC)
Expired
Dec 23, 2021, 8:30 PM MST
In force
60 min
Issued by
NWS Great Falls, MT
Area
Storm-based polygon
Hail
0.75 in
Wind
60.0 mph

Counties Blaine County, MT, Chouteau County, MT, Fergus County, MT, Judith Basin County, MT

The radar

The Glasgow radar (KGGW), 176 km from the middle of the area, began a volume at 02:31 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

Great_falls, MT (KTFX), launched 00:00Z, 2.5 hours before the alert went out and 133 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, Great_falls, MT at 00:00Z on 2021-12-24Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 0 joules per kilogram.LCL10008507005003002001001 km2 km3 km6 km9 km12 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Great_falls, MT at 00:00Z on 2021-12-24The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 194 square meters per square second.1939587897117Sfc1 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
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.

414 
WUUS55 KTFX 240230
SVRTFX
MTC005-015-027-045-240330-
/O.NEW.KTFX.SV.W.0065.211224T0230Z-211224T0330Z/

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

The National Weather Service in Great Falls has issued a

* Severe Thunderstorm Warning for...
  Northeastern Judith Basin County in central Montana...
  Fergus County in central Montana...
  Southern Blaine County in north central Montana...
  Southeastern Chouteau County in north central Montana...

* Until 830 PM MST.

* At 728 PM MST, severe thunderstorms were located along a line
  extending from 24 miles north of Winifred to 9 miles south of
  Stanford, moving east at 55 mph.

  HAZARD...60 mph wind gusts.

  SOURCE...Radar indicated.

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

* Locations impacted include...
  Lewistown, Stanford, Denton, Hobson, Winifred, Moore, Hays, Roy,
  Fergus, Windham, Forestgrove, Moccasin, Glengarry, Danvers, Coffee
  Creek, Suffolk, Giltedge, Judith Landing, Hilger and Heath.

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 4799 10860 4792 10864 4792 10889 4774 10890
      4771 10882 4765 10877 4762 10868 4762 10851
      4760 10849 4689 10899 4703 11054 4799 10971
      4801 10843 4797 10844
TIME...MOT...LOC 0228Z 267DEG 50KT 4791 10946 4702 11020 

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

$$

CMC

The office that day

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

IssuedProductOfficeCountiesLasted
Dec 23, 6:11 PM MSTSevere Thunderstorm WarningTFXCascade, Chouteau34 min
Dec 23, 6:34 PM MSTSnow Squall WarningTFXCascade, Chouteau, Hill, Judith Basin56 min
Dec 23, 6:50 PM MSTSevere Thunderstorm WarningTFXCascade, Chouteau, Fergus, Hill, Judith Basin40 min
Dec 24, 1:58 AM MSTWinter Storm WatchTFX12 hr

Nearby

Severe Thunderstorm Warnings in Montana, 2021Every 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; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.