Alert archive / Montana / Severe Thunderstorm Warnings in 2021

Severe Thunderstorm Warning 42, NWS Great Falls, MT

July 11, 2021Blaine County, Chouteau County, Hill County, Montana

NWS Great Falls, MT issued this severe thunderstorm warning at Jul 11, 2021, 5:55 PM MDT for Blaine County, Chouteau County, Hill County, Montana. It was in force for 65 min. 2 reports 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: Jul 11, 2021, 5:55 PM MDT (23:55 UTC)
Expired: Jul 11, 2021, 7:00 PM MDT
In force: 65 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, Hill County, MT

The radar

The Glasgow radar (KGGW), 160 km from the middle of the area, began a volume at 23:57 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
Jul 11, 6:00 PM MDT	TSTM WND GST 62	7 Wsw Havre, MT	MEASURED BY SITE MTM06.
Jul 11, 6:01 PM MDT	TSTM WND GST 55	5 Ssw Hays, MT

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

The nearest sounding before it

Glasgow Intl Airport, MT (KGGW), launched 12:00Z, 11.9 hours before the alert went out and 162 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: 2707 m above ground
0-6 km bulk shear: 34 kt
0-1 km storm-relative helicity: 199 m²/s²
0-3 km storm-relative helicity: 235 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

327 
WUUS55 KTFX 112355
SVRTFX
MTC005-015-041-120100-
/O.NEW.KTFX.SV.W.0042.210711T2355Z-210712T0100Z/

BULLETIN - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Warning
National Weather Service Great Falls MT
555 PM MDT Sun Jul 11 2021

The National Weather Service in Great Falls has issued a

* Severe Thunderstorm Warning for...
  Blaine County in north central Montana...
  Eastern Hill County in north central Montana...
  Northeastern Chouteau County in north central Montana...

* Until 700 PM MDT.

* At 554 PM MDT, severe thunderstorms were located along a line
  extending from 25 miles north of Chinook to 15 miles southeast of
  Parker School, moving east at 50 mph.

  HAZARD...60 mph wind gusts. Much of the severe wind gusts are 
           occurring with only light to moderate rainfall.

  SOURCE...Radar indicated.

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

* Locations impacted include...
  Havre, Chinook, Big Sandy, Harlem, Azure, Parker School, Beaver
  Creek, Agency, St. Pierre, Hays, Sangrey, Boneau, Fort Belknap,
  Turner, Box Elder, Rocky Boy, Lohman, Lodge Pole, Cleveland and
  Zurich.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

Wind damage with these storms may occur with only light rain 
present. Do not wait for the sound of thunder before taking cover.
Seek shelter inside a sturdy structure and stay away from windows.

&&

LAT...LON 4900 10823 4875 10826 4874 10832 4844 10835
      4844 10842 4797 10844 4799 10860 4792 10864
      4792 10889 4773 10890 4781 10898 4779 10911
      4811 11029 4900 11001
TIME...MOT...LOC 2354Z 289DEG 41KT 4896 10927 4804 10957 

HAIL...<.75IN
WIND...60MPH
 
$$

HART

2 follow-up statements

775 
WWUS55 KTFX 120026
SVSTFX

Severe Weather Statement
National Weather Service Great Falls MT
626 PM MDT Sun Jul 11 2021

MTC005-015-041-120100-
/O.CON.KTFX.SV.W.0042.000000T0000Z-210712T0100Z/
Blaine MT-Hill MT-Chouteau MT-
626 PM MDT Sun Jul 11 2021

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 700 PM MDT
FOR BLAINE...EASTERN HILL AND EAST CENTRAL CHOUTEAU COUNTIES...

At 625 PM MDT, severe thunderstorms were located along a line
extending from 16 miles west of Turner to 20 miles west of Hays,
moving east at 45 mph.

HAZARD...60 mph wind gusts. The severe wind gusts are occurring with 
         only light to moderate rainfall.

SOURCE...Radar indicated.

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

Locations impacted include...
Chinook, Harlem, Hays, Fort Belknap, Turner, Lohman, Lodge Pole,
Lloyd, Hogeland, Cleveland and Zurich.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 4900 10823 4875 10826 4874 10832 4844 10835
      4844 10842 4797 10844 4799 10860 4792 10864
      4792 10889 4773 10890 4781 10898 4779 10911
      4796 10971 4900 10954
TIME...MOT...LOC 0025Z 289DEG 41KT 4885 10878 4793 10908 

HAIL...<.75IN
WIND...60MPH
 
$$

HART

993 
WWUS55 KTFX 120051
SVSTFX

Severe Weather Statement
National Weather Service Great Falls MT
651 PM MDT Sun Jul 11 2021

MTC005-015-041-120100-
/O.EXP.KTFX.SV.W.0042.000000T0000Z-210712T0100Z/
Blaine MT-Hill MT-Chouteau MT-
651 PM MDT Sun Jul 11 2021

...THE SEVERE THUNDERSTORM WARNING FOR BLAINE...EASTERN HILL AND EAST
CENTRAL CHOUTEAU COUNTIES WILL EXPIRE AT 700 PM MDT...

Wind speeds have weakened. Therefore, the warning will be allowed to 
expire. However, gusty winds of 40 to 50 mph are still possible over 
the next 30 to 60 minutes.

LAT...LON 4900 10823 4875 10826 4874 10832 4844 10835
      4844 10842 4797 10844 4799 10860 4792 10864
      4792 10889 4773 10890 4781 10898 4779 10911
      4796 10971 4900 10954
TIME...MOT...LOC 0050Z 289DEG 41KT 4876 10839 4784 10869 

$$

HART

The office that day

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

Issued	Product	Office	Counties	Lasted
Jul 11, 12:33 AM MDT	Red Flag Warning	TFX	Blaine, Broadwater, Cascade, Chouteau, Fergus, Gallatin and 12 more	20 hr
Jul 11, 2:18 PM MDT	Special Weather Statement	TFX	Glacier	42 min
Jul 11, 2:28 PM MDT	Severe Thunderstorm Warning	TFX	Glacier	50 min
Jul 11, 2:58 PM MDT	Special Weather Statement	TFX	Glacier	32 min
Jul 11, 3:03 PM MDT	Severe Thunderstorm Warning	TFX	Glacier, Toole	42 min
Jul 11, 3:40 PM MDT	Severe Thunderstorm Warning	TFX	Toole	50 min
Jul 11, 4:18 PM MDT	Severe Thunderstorm Warning	TFX	Liberty, Toole	27 min
Jul 11, 4:36 PM MDT	Special Weather Statement	TFX	Pondera	24 min
Jul 11, 4:47 PM MDT	Special Weather Statement	TFX	Chouteau	28 min
Jul 11, 5:05 PM MDT	Special Weather Statement	TFX	Pondera	25 min
Jul 11, 5:11 PM MDT	Severe Thunderstorm Warning	TFX	Chouteau, Hill	49 min

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.