Alert archive / Montana / Severe Thunderstorm Watches in 2016

Severe Thunderstorm Watch 188

May 21, 201619 counties in Montana

The Storm Prediction Center issued this severe thunderstorm watch at May 21, 2016, 2:26 PM MDT for 19 counties in Montana. It was in force for 7 hr.

The area

The outline as issued.

The facts

Issued
May 21, 2016, 2:26 PM MDT (20:26 UTC)
Expired
May 21, 2016, 9:00 PM MDT
In force
7 hr
Issued by
the Storm Prediction Center
Largest hail expected
2 in
Strongest gust expected
60 kt

Counties Big Horn County, MT, Daniels County, MT, Dawson County, MT, Fergus County, MT, Garfield County, MT, Golden Valley County, MT, McCone County, MT, Musselshell County, MT, Petroleum County, MT, Phillips County, MT, Prairie County, MT, Richland County, MT, Roosevelt County, MT, Rosebud County, MT, Sheridan County, MT, Treasure County, MT, Valley County, MT, Wibaux County, MT, Yellowstone County, MT

The radar

The Glasgow radar (KGGW), 135 km from the middle of the area, began a volume at 20:25 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 SPC expected

The probabilities SPC published with the watch, for the watch area over its life.

Two or more tornadoes
20%
One or more EF2 to EF5 tornadoes
5%
Ten or more severe wind reports
60%
One or more gusts of 65 knots or more
10%
Ten or more severe hail reports
60%
One or more hailstones of 2 inches or more
30%
Six or more combined severe hail and wind reports
80%

Warnings issued inside it

18 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.

IssuedProductOfficeCountiesLasted
May 21, 2:40 PM MDTSevere Thunderstorm WarningBYZBig Horn, Carbon, Golden Valley, Musselshell, Stillwater, Wheatland and 1 more65 min
May 21, 3:29 PM MDTSevere Thunderstorm WarningBYZMusselshell, Yellowstone61 min
May 21, 3:50 PM MDTTornado WarningBYZMusselshell, Yellowstone25 min
May 21, 4:16 PM MDTSevere Thunderstorm WarningBYZMusselshell, Rosebud, Treasure, Yellowstone59 min
May 21, 4:49 PM MDTSevere Thunderstorm WarningGGWGarfield56 min
May 21, 5:41 PM MDTSevere Thunderstorm WarningBYZRosebud45 min
May 21, 5:42 PM MDTSevere Thunderstorm WarningGGWGarfield, Valley63 min
May 21, 5:53 PM MDTSevere Thunderstorm WarningGGWPhillips, Valley67 min
May 21, 5:57 PM MDTSevere Thunderstorm WarningBYZBig Horn, Powder River, Rosebud63 min
May 21, 6:04 PM MDTSevere Thunderstorm WarningGGWPhillips, Valley26 min
May 21, 6:10 PM MDTSevere Thunderstorm WarningGGWValley48 min
May 21, 6:18 PM MDTSevere Thunderstorm WarningGGWGarfield, McCone, Valley57 min
May 21, 6:26 PM MDTSevere Thunderstorm WarningGGWPhillips, Valley64 min
May 21, 6:53 PM MDTSevere Thunderstorm WarningGGWGarfield, McCone, Prairie45 min
May 21, 7:06 PM MDTSevere Thunderstorm WarningGGWDaniels, McCone, Roosevelt, Valley54 min
May 21, 7:18 PM MDTSevere Thunderstorm WarningGGWValley27 min
May 21, 7:45 PM MDTSevere Thunderstorm WarningGGWGarfield, Valley30 min
May 21, 7:49 PM MDTSevere Thunderstorm WarningGGWDaniels, Roosevelt, Valley14 min

Discussions around it

SPC mesoscale discussions over the same counties from four hours before the watch to its end.

The nearest sounding before it

Glasgow Intl Airport, MT (KGGW), launched 12:00Z, 8.4 hours before the alert went out and 137 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, Glasgow Intl Airport, MT at 12:00Z on 2016-05-21Temperature 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 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Glasgow Intl Airport, MT at 12:00Z on 2016-05-21The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 98 square meters per square second.193958Sfc1 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
1132 m above ground
0-6 km bulk shear
21 kt
0-1 km storm-relative helicity
98 m²/s²
0-3 km storm-relative helicity
48 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
May 21, 2:10 PM MDTMesoscale DiscussionSPCBlaine, Carbon, Fergus, Golden Valley, Musselshell, Petroleum and 2 more65 min
May 21, 2:54 PM MDTMesoscale DiscussionSPCCarter, Custer, Dawson, Fallon, Powder River, Prairie and 2 more2 hr
May 21, 4:37 PM MDTMesoscale DiscussionSPCBig Horn, Garfield, Musselshell, Petroleum, Phillips, Rosebud and 3 more53 min
May 21, 5:03 PM MDTSevere Thunderstorm WatchSPCCarter, Custer, Fallon, Powder River5 hr

Nearby

Severe Thunderstorm Watches in Montana, 2016Every severe thunderstorm watch in 2016

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.