Alert archive / Montana / Severe Thunderstorm Warnings in 2021

Severe Thunderstorm Warning 62, NWS Glasgow, MT

July 6, 2021Garfield County, Montana

NWS Glasgow, MT issued this severe thunderstorm warning at Jul 6, 2021, 9:26 PM MDT for Garfield County, Montana. It was in force for 34 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: Jul 6, 2021, 9:26 PM MDT (03:26 UTC)
Expired: Jul 6, 2021, 10:00 PM MDT
In force: 34 min
Issued by: NWS Glasgow, MT
Area: Storm-based polygon
Tornado: Possible
Hail: 1.25 in
Wind: 70.0 mph

County Garfield County, MT

The radar

The Billings radar (KBLX), 151 km from the middle of the area, began a volume at 03:28 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 6, 9:36 PM MDT	HAIL 1	14 Sse Sand Springs, MT	ONE INCH HAIL LASTED FOR ABOUT 20 MINUTES AND BROKE THE RAIN GAUGE. REPORT FROM FB.

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

Did it verify

Verified. The Iowa Environmental Mesonet's Cow matched one storm report to this severe thunderstorm warning; the first came 10 minutes after it went out.

Cow counts a report within 15 km of the polygon while the warning was in force: a tornado for a tornado warning; hail of 1 inch or more, a gust of 58 mph or more or wind damage for a severe thunderstorm warning; a flash flood report for a flash flood warning.

The nearest sounding before it

Glasgow Intl Airport, MT (KGGW), launched 00:00Z, 3.4 hours before the alert went out and 156 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: 20 J/kg
Mixed-layer CIN: -155 J/kg
Mixed-layer LCL: 1401 m above ground
0-6 km bulk shear: 54 kt
0-1 km storm-relative helicity: -5 m²/s²
0-3 km storm-relative helicity: 134 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.1

Open this sounding in Storm Lab

The text

As transmitted.

450 
WUUS55 KGGW 070326
SVRGGW
MTC033-070400-
/O.NEW.KGGW.SV.W.0062.210707T0326Z-210707T0400Z/

BULLETIN - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Warning
National Weather Service Glasgow MT
926 PM MDT Tue Jul 6 2021

The National Weather Service in Glasgow has issued a

* Severe Thunderstorm Warning for...
  South central Garfield County in northeastern Montana...

* Until 1000 PM MDT.

* At 926 PM MDT, a severe thunderstorm was located 10 miles southeast
  of Sand Springs, or 32 miles southwest of Jordan, moving southeast
  at 35 mph.

  HAZARD...70 mph wind gusts and half dollar size hail.

  SOURCE...Radar indicated.

  IMPACT...Hail damage to vehicles is expected. Expect considerable 
           tree damage. Wind damage is also likely to mobile homes, 
           roofs, and outbuildings.

* This severe thunderstorm will remain over mainly rural areas of
  south central Garfield County.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

Torrential rainfall is occurring with this storm, and may lead to
flash flooding. Do not drive your vehicle through flooded roadways.

&&

LAT...LON 4699 10754 4707 10730 4686 10705 4686 10746
      4685 10747 4685 10748
TIME...MOT...LOC 0326Z 326DEG 30KT 4697 10736 

TORNADO...POSSIBLE
HAIL...1.25IN
WIND...70MPH
 
$$

Mottice

2 follow-up statements

907 
WWUS55 KGGW 070341
SVSGGW

Severe Weather Statement
National Weather Service Glasgow MT
941 PM MDT Tue Jul 6 2021

MTC033-070400-
/O.CON.KGGW.SV.W.0062.000000T0000Z-210707T0400Z/
Garfield MT-
941 PM MDT Tue Jul 6 2021

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 1000 PM MDT
FOR SOUTH CENTRAL GARFIELD COUNTY...

At 940 PM MDT, a severe thunderstorm was located 19 miles south of
Edwards, or 35 miles southwest of Jordan, moving southeast at 35 mph.

HAZARD...60 mph wind gusts and half dollar size hail.

SOURCE...Radar indicated.

IMPACT...Hail damage to vehicles is expected. Expect wind damage to 
         roofs, siding, and trees.

This severe thunderstorm will remain over mainly rural areas of south
central Garfield County.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

Torrential rainfall is occurring with this storm, and may lead to
flash flooding. Do not drive your vehicle through flooded roadways.

&&

LAT...LON 4689 10742 4695 10722 4686 10708 4686 10740
TIME...MOT...LOC 0340Z 326DEG 30KT 4687 10726 

TORNADO...POSSIBLE
HAIL...1.25IN
WIND...60MPH
 
$$

Mottice

097 
WWUS55 KGGW 070359
SVSGGW

Severe Weather Statement
National Weather Service Glasgow MT
959 PM MDT Tue Jul 6 2021

MTC033-070409-
/O.EXP.KGGW.SV.W.0062.000000T0000Z-210707T0400Z/
Garfield MT-
959 PM MDT Tue Jul 6 2021

...THE SEVERE THUNDERSTORM WARNING FOR SOUTH CENTRAL GARFIELD COUNTY
WILL EXPIRE AT 1000 PM MDT...
                
The storm which prompted the warning has weakened below severe
limits, and no longer poses an immediate threat to life or property.
Therefore, the warning will be allowed to expire.

LAT...LON 4689 10742 4695 10722 4686 10708 4686 10740
TIME...MOT...LOC 0359Z 326DEG 30KT 4676 10715 

$$

NWS Glasgow

What forecasters said that day

The local office's own words before this severe thunderstorm warning went out, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS Glasgow, MT wrote its last area forecast discussion before this severe thunderstorm warning went out at Jul 6, 1:35 PM MDT, 7 hours 51 minutes earlier.

Area forecast discussion, Jul 6, 1:35 PM MDT, 7 hours 51 minutes before

Area Forecast Discussion
National Weather Service Glasgow MT
135 PM MDT Tue Jul 6 2021

.DISCUSSION...
Morning thunderstorms moved through portions of Phillips, northern
Petroleum, and Garfield Counties. These storms produced around a
half inch of rain for many locations in their path. These storms
have since died off and a clearly defined outflow/differential
heating boundary has been left behind. Locations south of the
boundary are denoted by upslope southeasterly winds and dewpoints
in the mid-50s. Areas north have easterly winds and dewpoints
around 60 degrees.

This boundary runs from northeastern Fergus County southeastward
through northern Petroleum and southern Garfield Counties. A CU
field has started to develop and thunderstorm development is
possible later this afternoon.

The latest RAP analysis suggests there is around 800-1000 J/Kg of
MLCAPE in the area as of 1 PM with 1500-2000 J/Kg of MLCAPE. This
combined with effective bulk shear around 40-45 knots suggests any
storm that is able to form has a good chance of becoming severe
with a large hail and damaging wind threat. The primary
limitation is the amount of forcing.

Additional storms will move in from the north this evening into
early tonight as they move off the Alberta Front Range. These are
less likely to be severe, however, a strong to severe storm still
cannot be ruled out.

Scattered thunderstorm chances will continue for the rest of the
week with additional severe storms possible on Wednesday (southern
Phillips, Petroleum, and Garfield Counties) and Thursday (far
Northeast Montana). Thunderstorm chances decrease as we head into
next weekend and early next week.

After near normal temperatures today, look for warmer
temperatures for Wednesday and Thursday with highs in the low to
mid 90s. Temperatures in the 70s and 80s are expected Friday with
a warmup expected as we head into the weekend. Widespread 80s are
likely Saturday with upper 80s to upper 90s on Sunday.

-Mottice

&&

.AVIATION...
CATEGORY: VFR-MVFR.

DISCUSSION: Low clouds will continue to break up near the
ND border through the evening hours. Scattered thunderstorms will
develop later this afternoon into this evening with strong winds
and hail possible, mainly southwest of KGGW. More general
thunderstorms are possible elsewhere through tonight. MVFR
conditions are possible in any thunderstorm.

WINDS: Easterly winds of 15 to 20 knots this afternoon will die
down overnight and become southeasterly around 10 knots through
Wednesday afternoon.

&&

.GLASGOW WATCHES/WARNINGS/ADVISORIES...NONE.

&&

weather.gov/glasgow

In the hours before

Special weather statement, Jul 6, 7:50 PM MDT, 1 hour 36 minutes before

Special Weather Statement
National Weather Service Glasgow MT
750 PM MDT Tue Jul 6 2021

MTZ016-059-070230-
Central and Southeast Phillips MT-Northern Phillips MT-
750 PM MDT Tue Jul 6 2021

...SIGNIFICANT WEATHER ADVISORY FOR NORTH CENTRAL PHILLIPS COUNTY
UNTIL 830 PM MDT...

At 750 PM MDT, Doppler radar was tracking a strong thunderstorm near
Turner, or 33 miles west of Whitewater, moving southeast at 20 mph.

Nickel size hail and wind gusts of 50 to 55 mph will be possible with
this storm.

Locations impacted include...
Loring and Chapman.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 4900 10815 4885 10776 4856 10824 4867 10832
      4874 10832 4874 10826 4891 10826 4891 10823
      4900 10824
TIME...MOT...LOC 0150Z 318DEG 19KT 4892 10833

Mottice

Special weather statement, Jul 6, 8:00 PM MDT, 1 hour 26 minutes before

Special Weather Statement
National Weather Service Glasgow MT
800 PM MDT Tue Jul 6 2021

MTZ016-021-022-070300-
Petroleum MT-Garfield MT-Central and Southeast Phillips MT-
800 PM MDT Tue Jul 6 2021

...SIGNIFICANT WEATHER ADVISORY FOR SOUTH CENTRAL PHILLIPS...WEST
CENTRAL GARFIELD AND NORTHEASTERN PETROLEUM COUNTIES UNTIL 900 PM
MDT...

At 800 PM MDT, Doppler radar was tracking a strong thunderstorm near
U L Bend Rec Area, or 37 miles southeast of Zortman, moving southeast
at 35 mph.

Nickel size hail and wind gusts of 50 to 55 mph will be possible with
this storm.

Locations impacted include...
Devils Creek Rec Area, Crooked Creek Rec Area and U L Bend Rec Area.

LAT...LON 4757 10816 4773 10794 4749 10718 4721 10761
TIME...MOT...LOC 0200Z 306DEG 30KT 4758 10791

NWS Glasgow

Special weather statement, Jul 6, 8:43 PM MDT, 43 minutes before

Special Weather Statement
National Weather Service Glasgow MT
843 PM MDT Tue Jul 6 2021

MTZ022-070330-
Garfield MT-
843 PM MDT Tue Jul 6 2021

...SIGNIFICANT WEATHER ADVISORY FOR SOUTHWESTERN GARFIELD COUNTY
UNTIL 930 PM MDT...

At 843 PM MDT, Doppler radar was tracking a strong thunderstorm 14
miles northwest of Sand Springs, or 33 miles west of Jordan, moving
southeast at 35 mph.

Nickel size hail and wind gusts of 50 to 55 mph will be possible with
this storm.

Locations impacted include...
Edwards, Sand Springs and Steve Fork.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 4729 10789 4748 10751 4708 10707 4690 10753
TIME...MOT...LOC 0243Z 328DEG 30KT 4729 10762

NWS Glasgow

The office that day

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

Issued	Product	Office	Counties	Lasted
Jul 6, 6:24 PM MDT	Severe Thunderstorm Warning	GGW	Phillips	66 min
Jul 6, 7:06 PM MDT	Severe Thunderstorm Warning	GGW	Petroleum, Phillips	54 min
Jul 6, 7:50 PM MDT	Special Weather Statement	GGW		40 min
Jul 6, 8:00 PM MDT	Special Weather Statement	GGW	Garfield	60 min
Jul 6, 8:23 PM MDT	Severe Thunderstorm Warning	GGW	Phillips	52 min
Jul 6, 8:43 PM MDT	Special Weather Statement	GGW	Garfield	47 min
Jul 6, 8:45 PM MDT	Severe Thunderstorm Warning	GGW	Garfield	45 min
Jul 6, 9:06 PM MDT	Tornado Warning	GGW	Garfield	24 min
Jul 6, 9:09 PM MDT	Severe Thunderstorm Warning	GGW	Phillips	66 min
Jul 6, 10:17 PM MDT	Severe Thunderstorm Warning	GGW	Garfield, Phillips, Valley	58 min
Jul 6, 11:16 PM MDT	Special Weather Statement	GGW	Garfield	44 min
Jul 6, 11:40 PM MDT	Special Weather Statement	GGW	Roosevelt	50 min
Jul 6, 11:57 PM MDT	Special Weather Statement	GGW	Garfield	48 min
Jul 7, 3:58 PM MDT	Special Weather Statement	GGW	Petroleum	47 min
Jul 7, 4:42 PM MDT	Special Weather Statement	GGW	Petroleum	48 min
Jul 7, 5:30 PM MDT	Special Weather Statement	GGW	Garfield	45 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.