Alert archive / Montana / Severe Thunderstorm Watches in 2011
Severe Thunderstorm Watch 637
The Storm Prediction Center issued this severe thunderstorm watch at Jul 12, 2011, 1:38 PM MDT for Lemhi County, Idaho; 26 counties in Montana. It was in force for 7 hr.
The area
The outline as issued.
The facts
- Issued
- Jul 12, 2011, 1:38 PM MDT (19:38 UTC)
- Expired
- Jul 12, 2011, 9:00 PM MDT
- In force
- 7 hr
- Issued by
- the Storm Prediction Center
- Largest hail expected
- 2 in
- Strongest gust expected
- 60 kt
All 27 counties
Lemhi County, ID, Beaverhead County, MT, Blaine County, MT, Broadwater County, MT, Cascade County, MT, Chouteau County, MT, Deer Lodge County, MT, Fergus County, MT, Gallatin County, MT, Granite County, MT, Hill County, MT, Jefferson County, MT, Judith Basin County, MT, Lewis and Clark County, MT, Liberty County, MT, Madison County, MT, Meagher County, MT, Missoula County, MT, Park County, MT, Pondera County, MT, Powell County, MT, Ravalli County, MT, Silver Bow County, MT, Sweet Grass County, MT, Teton County, MT, Toole County, MT, Wheatland County, MT
The radar
The Great Falls radar (KTFX), 110 km from the middle of the area, began a volume at 19:40 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
- 10%
- One or more EF2 to EF5 tornadoes
- 5%
- Ten or more severe wind reports
- 40%
- One or more gusts of 65 knots or more
- 10%
- Ten or more severe hail reports
- 50%
- One or more hailstones of 2 inches or more
- 10%
- Six or more combined severe hail and wind reports
- 70%
Warnings issued inside it
5 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jul 12, 1:46 PM MDT | Flash Flood Warning | MSO | Lemhi | 59 min |
| Jul 12, 2:25 PM MDT | Severe Thunderstorm Warning | MSO | Powell | 35 min |
| Jul 12, 2:47 PM MDT | Severe Thunderstorm Warning | TFX | Broadwater, Jefferson, Lewis and Clark | 58 min |
| Jul 12, 3:16 PM MDT | Severe Thunderstorm Warning | TFX | Lewis and Clark | 44 min |
| Jul 12, 4:27 PM MDT | Severe Thunderstorm Warning | MSO | Granite, Missoula | 48 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
Great_falls, MT (KTFX), launched 12:00Z, 7.6 hours before the alert went out and 147 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
- 0 J/kg
- Mixed-layer CIN
- No buoyant parcel
- Mixed-layer LCL
- 1763 m above ground
- 0-6 km bulk shear
- 20 kt
- 0-1 km storm-relative helicity
- 105 m²/s²
- 0-3 km storm-relative helicity
- 107 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 |
|---|---|---|---|---|
| Jul 12, 5:30 PM MDT | Mesoscale Discussion | SPC | Clark, Lemhi | 60 min |
| Jul 12, 12:56 PM MDT | Mesoscale Discussion | SPC | Beaverhead, Broadwater, Cascade, Deer Lodge, Flathead, Gallatin and 16 more | 64 min |
Nearby
Severe Thunderstorm Watches in Montana, 2011Severe Thunderstorm Watches in Idaho, 2011Every severe thunderstorm watch in 2011
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.