Alert archive / Montana / Severe Thunderstorm Watches in 2009
Severe Thunderstorm Watch 539
The Storm Prediction Center issued this severe thunderstorm watch at Jul 2, 2009, 4:12 PM MDT for 10 counties in Montana. It was in force for 4 hr.
The area
The outline as issued.
The facts
- Issued
- Jul 2, 2009, 4:12 PM MDT (22:12 UTC)
- Expired
- Jul 2, 2009, 7:57 PM MDT
- In force
- 4 hr
- Issued by
- the Storm Prediction Center
- Largest hail expected
- 2 in
- Strongest gust expected
- 60 kt
Counties Big Horn County, MT, Carbon County, MT, Golden Valley County, MT, Musselshell County, MT, Park County, MT, Stillwater County, MT, Sweet Grass County, MT, Treasure County, MT, Wheatland County, MT, Yellowstone County, MT
The radar
The Billings radar (KBLX), 49 km from the middle of the area, began a volume at 22:15 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
- 30%
- Ten or more severe hail reports
- 30%
- One or more hailstones of 2 inches or more
- 20%
- Six or more combined severe hail and wind reports
- 70%
Warnings issued inside it
3 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jul 2, 4:16 PM MDT | Severe Thunderstorm Warning | BYZ | Musselshell | 59 min |
| Jul 2, 5:14 PM MDT | Severe Thunderstorm Warning | BYZ | Musselshell | 30 min |
| Jul 2, 6:40 PM MDT | Flash Flood Warning | BYZ | Golden Valley, Wheatland | 3 hr |
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, 10.2 hours before the alert went out and 313 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
- 313 J/kg
- Mixed-layer CIN
- -89 J/kg
- Mixed-layer LCL
- 1066 m above ground
- 0-6 km bulk shear
- 46 kt
- 0-1 km storm-relative helicity
- 148 m²/s²
- 0-3 km storm-relative helicity
- 190 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- -0.1
SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jul 2, 11:25 AM MDT | Mesoscale Discussion | SPC | Carter, Custer, Fallon, Powder River, Prairie, Rosebud and 1 more | 65 min |
| Jul 2, 11:41 AM MDT | Severe Thunderstorm Watch | SPC | Big Horn, Carter, Custer, Dawson, Fallon, Garfield and 5 more | 7 hr |
| Jul 2, 2:17 PM MDT | Mesoscale Discussion | SPC | Big Horn, Carter, Custer, Fallon, Garfield, Powder River and 4 more | 88 min |
| Jul 2, 3:41 PM MDT | Mesoscale Discussion | SPC | Blaine, Broadwater, Carbon, Cascade, Chouteau, Fergus and 16 more | 34 min |
Nearby
Severe Thunderstorm Watches in Montana, 2009Every severe thunderstorm watch in 2009
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.