Alert archive / Montana / Severe Thunderstorm Watches in 2016
Severe Thunderstorm Watch 189
The Storm Prediction Center issued this severe thunderstorm watch at May 21, 2016, 5:03 PM MDT for 4 counties in Montana; 4 counties in Wyoming. It was in force for 5 hr.
The area
The outline as issued.
The facts
- Issued
- May 21, 2016, 5:03 PM MDT (23:03 UTC)
- Expired
- May 21, 2016, 10:30 PM MDT
- In force
- 5 hr
- Issued by
- the Storm Prediction Center
- Largest hail expected
- 2 in
- Strongest gust expected
- 60 kt
Counties Carter County, MT, Custer County, MT, Fallon County, MT, Powder River County, MT, Campbell County, WY, Crook County, WY, Johnson County, WY, Weston County, WY
The radar
The Billings radar (KBLX), 243 km from the middle of the area, began a volume at 23:02 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
- 30%
- One or more gusts of 65 knots or more
- 10%
- Ten or more severe hail reports
- 40%
- One or more hailstones of 2 inches or more
- 30%
- Six or more combined severe hail and wind reports
- 60%
Warnings issued inside it
6 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| May 21, 5:57 PM MDT | Severe Thunderstorm Warning | BYZ | Big Horn, Powder River, Rosebud | 63 min |
| May 21, 6:37 PM MDT | Severe Thunderstorm Warning | RIW | Johnson | 53 min |
| May 21, 6:44 PM MDT | Severe Thunderstorm Warning | UNR | Campbell | 61 min |
| May 21, 6:56 PM MDT | Severe Thunderstorm Warning | UNR | Campbell | 64 min |
| May 21, 7:43 PM MDT | Severe Thunderstorm Warning | UNR | Campbell | 62 min |
| May 21, 7:57 PM MDT | Severe Thunderstorm Warning | UNR | Campbell, Weston | 63 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
Rapid City, SD (KRAP), launched 12:00Z, 11.1 hours before the alert went out and 252 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.
- Mixed-layer CAPE
- 13 J/kg
- Mixed-layer CIN
- -492 J/kg
- Mixed-layer LCL
- 762 m above ground
- 0-6 km bulk shear
- 26 kt
- 0-1 km storm-relative helicity
- 9 m²/s²
- 0-3 km storm-relative helicity
- 148 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| May 21, 2:10 PM MDT | Mesoscale Discussion | SPC | Blaine, Carbon, Fergus, Golden Valley, Musselshell, Petroleum and 2 more | 65 min |
| May 21, 2:26 PM MDT | Severe Thunderstorm Watch | SPC | Big Horn, Daniels, Dawson, Fergus, Garfield, Golden Valley and 13 more | 7 hr |
| May 21, 2:54 PM MDT | Mesoscale Discussion | SPC | Carter, Custer, Dawson, Fallon, Powder River, Prairie and 2 more | 2 hr |
| May 21, 4:37 PM MDT | Mesoscale Discussion | SPC | Big Horn, Garfield, Musselshell, Petroleum, Phillips, Rosebud and 3 more | 53 min |
Nearby
Severe Thunderstorm Watches in Montana, 2016Severe Thunderstorm Watches in Wyoming, 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.