Alert archive / Montana / Severe Thunderstorm Watches in 2007

Severe Thunderstorm Watch 281

May 20, 200719 counties in Montana; 10 counties in South Dakota; 5 counties in Wyoming

The Storm Prediction Center issued this severe thunderstorm watch at May 20, 2007, 2:33 PM MDT for 19 counties in Montana; 10 counties in South Dakota; 5 counties in Wyoming. It was in force for 9 hr.

The area

The outline as issued.

The facts

Issued
May 20, 2007, 2:33 PM MDT (20:33 UTC)
Expired
May 21, 2007, 12:00 AM MDT
In force
9 hr
Issued by
the Storm Prediction Center
All 34 counties

Big Horn County, MT, Carbon County, MT, Carter County, MT, Custer County, MT, Dawson County, MT, Fallon County, MT, Garfield County, MT, Golden Valley County, MT, McCone County, MT, Musselshell County, MT, Petroleum County, MT, Powder River County, MT, Prairie County, MT, Richland County, MT, Rosebud County, MT, Stillwater County, MT, Treasure County, MT, Wibaux County, MT, Yellowstone County, MT, Bennett County, SD, Butte County, SD, Custer County, SD, Haakon County, SD, Harding County, SD, Jackson County, SD, Lawrence County, SD, Meade County, SD, Pennington County, SD, Perkins County, SD, Campbell County, WY, Crook County, WY, Johnson County, WY, Sheridan County, WY, Weston County, WY

The radar

The Billings radar (KBLX), 239 km from the middle of the area, began a volume at 20:32 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.

Warnings issued inside it

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

IssuedProductOfficeCountiesLasted
May 20, 3:01 PM MDTSevere Thunderstorm WarningUNRPennington59 min
May 20, 4:00 PM MDTSevere Thunderstorm WarningUNRPennington60 min
May 20, 4:51 PM MDTSevere Thunderstorm WarningBYZGolden Valley, Wheatland37 min
May 20, 5:33 PM MDTSevere Thunderstorm WarningUNRJackson57 min
May 20, 5:44 PM MDTSevere Thunderstorm WarningRIWJohnson31 min
May 20, 5:46 PM MDTSevere Thunderstorm WarningUNRWeston51 min
May 20, 6:44 PM MDTSevere Thunderstorm WarningUNRCampbell61 min
May 20, 6:50 PM MDTSevere Thunderstorm WarningBYZGolden Valley25 min
May 20, 7:14 PM MDTTornado WarningUNRCampbell46 min
May 20, 7:17 PM MDTSevere Thunderstorm WarningBYZGolden Valley, Musselshell58 min
May 20, 7:54 PM MDTSevere Thunderstorm WarningGGWGarfield, Petroleum66 min
May 20, 8:09 PM MDTSevere Thunderstorm WarningBYZMusselshell36 min
May 20, 8:32 PM MDTSevere Thunderstorm WarningBYZMusselshell, Rosebud, Treasure, Yellowstone73 min
May 20, 8:57 PM MDTSevere Thunderstorm WarningGGWGarfield63 min
May 20, 9:58 PM MDTSevere Thunderstorm WarningGGWGarfield, McCone, Prairie62 min
May 20, 11:00 PM MDTSevere Thunderstorm WarningGGWDawson, McCone, Prairie60 min
May 20, 11:57 PM MDTSevere Thunderstorm WarningGGWDawson, Prairie63 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 (KUNR), launched 12:00Z, 8.6 hours before the alert went out and 255 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, Rapid City, SD at 12:00Z on 2007-05-20Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 101 joules per kilogram.LCLLFCEL10008507005003002001001 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, Rapid City, SD at 12:00Z on 2007-05-20The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 107 square meters per square second.1939Sfc1 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
101 J/kg
Mixed-layer CIN
-403 J/kg
Mixed-layer LCL
1152 m above ground
0-6 km bulk shear
19 kt
0-1 km storm-relative helicity
107 m²/s²
0-3 km storm-relative helicity
124 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 19, 9:04 PM MDTMesoscale DiscussionSPCCarter, Custer, Fergus, Garfield, Musselshell, Petroleum and 4 more56 min
May 20, 1:45 PM MDTMesoscale DiscussionSPCBig Horn, Carbon, Carter, Custer, Golden Valley, Musselshell and 7 more60 min
May 20, 5:17 PM MDTMesoscale DiscussionSPCBrule, Buffalo, Hughes, Jones, Lyman, Mellette and 1 more88 min

Nearby

Severe Thunderstorm Watches in Montana, 2007Severe Thunderstorm Watches in South Dakota, 2007Severe Thunderstorm Watches in Wyoming, 2007Every severe thunderstorm watch in 2007

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.