Alert archive / Montana / Severe Thunderstorm Warnings in 2020

Severe Thunderstorm Warning 3, NWS Glasgow, MT

May 20, 2020Prairie County, Montana

NWS Glasgow, MT issued this severe thunderstorm warning at May 20, 2020, 6:55 PM MDT for Prairie County, Montana. It was in force for 30 min. No storm report in the archive falls inside the area while it was in force.

The area

The counties it named.

The facts

Issued: May 20, 2020, 6:55 PM MDT (00:55 UTC)
Expired: May 20, 2020, 7:25 PM MDT
In force: 30 min
Issued by: NWS Glasgow, MT
Area: Storm-based polygon
Hail: 1.25 in
Wind: 60.0 mph

County Prairie County, MT

The radar

The Glasgow radar (KGGW), 176 km from the middle of the area, began a volume at 00:54 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 watch it was issued in

The SPC watch in force over the same counties when this warning went out.

Issued	Product	Office	Lasted
May 20, 3:11 PM MDT	Severe Thunderstorm Watch	SPC	8 hr

The nearest sounding before it

Glasgow Intl Airport, MT (KGGW), launched 00:00Z, 0.9 hours before the alert went out and 177 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: 975 J/kg
Mixed-layer CIN: -43 J/kg
Mixed-layer LCL: 1692 m above ground
0-6 km bulk shear: 30 kt
0-1 km storm-relative helicity: 2 m²/s²
0-3 km storm-relative helicity: 35 m²/s²
Significant tornado parameter: -0.0
Supercell composite: -0.4

Open this sounding in Storm Lab

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 May 20, 3:22 PM MDT, 3 hours 33 minutes earlier.

Area forecast discussion, May 20, 3:22 PM MDT, 3 hours 33 minutes before

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In the hours before

Special weather statement, May 20, 5:54 PM MDT, 1 hour 1 minute before

Special Weather Statement
National Weather Service Glasgow MT
554 PM MDT Wed May 20 2020

MTZ021-210100-
Petroleum MT-
554 PM MDT Wed May 20 2020

...SIGNIFICANT WEATHER ADVISORY FOR SOUTHERN PETROLEUM COUNTY UNTIL
700 PM MDT...

At 553 PM MDT, Doppler radar was tracking a strong thunderstorm 10
miles southwest of Flatwillow, or 18 miles north of Roundup, moving
north at 30 mph.

Penny size hail and wind gusts up to 50 mph will be possible with
this storm.

Locations impacted include...
Winnett, Flatwillow, Petrolia Lake and Tiegen.

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.

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.

&&

A Severe Thunderstorm Watch remains in effect until 1100 PM MDT for
northeastern Montana.

LAT...LON 4684 10863 4684 10862 4690 10861 4710 10861
      4710 10862 4716 10855 4707 10802 4675 10831
      4675 10863
TIME...MOT...LOC 2353Z 201DEG 27KT 4672 10853

NWS Glasgow

The office that day

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

Issued	Product	Office	Counties	Lasted
May 20, 7:28 PM MDT	Severe Thunderstorm Warning	GGW	Dawson, Garfield, McCone, Prairie	62 min
May 20, 7:35 PM MDT	Severe Thunderstorm Warning	GGW	Garfield, Petroleum, Phillips	55 min
May 20, 8:18 PM MDT	Severe Thunderstorm Warning	GGW	Garfield, McCone, Prairie, Valley	57 min
May 20, 8:36 PM MDT	Severe Thunderstorm Warning	GGW	Dawson, McCone, Richland, Roosevelt, Wibaux	39 min
May 20, 8:44 PM MDT	Severe Thunderstorm Warning	GGW	Dawson, Garfield, McCone, Phillips, Richland, Roosevelt and 1 more	76 min
May 20, 9:17 PM MDT	Tornado Warning	GGW	Valley	13 min
May 20, 9:33 PM MDT	Severe Thunderstorm Warning	GGW	Daniels, Phillips, Roosevelt, Valley	57 min
May 20, 9:35 PM MDT	Severe Thunderstorm Warning	GGW	Daniels, Roosevelt, Sheridan	55 min
May 20, 10:02 PM MDT	Areal Flood Advisory	GGW	Garfield, Valley	3 hr
May 20, 10:21 PM MDT	Special Weather Statement	GGW	Roosevelt	54 min
May 20, 10:33 PM MDT	Special Weather Statement	GGW		57 min
May 20, 10:54 PM MDT	Special Weather Statement	GGW	Daniels	66 min
May 20, 11:09 PM MDT	Special Weather Statement	GGW	Phillips, Valley	81 min
May 21, 3:04 PM MDT	Special Weather Statement	GGW	Valley	26 min
May 21, 3:36 PM MDT	Special Weather Statement	GGW	Valley	39 min
May 21, 3:51 PM MDT	Special Weather Statement	GGW	Daniels	39 min

Nearby

Severe Thunderstorm Warnings in Montana, 2020 Every severe thunderstorm warning in 2020

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.