Alert archive / North Dakota / Severe Thunderstorm Watches in 2011

Severe Thunderstorm Watch 702

July 29, 20118 counties in Montana; 11 counties in North Dakota

The Storm Prediction Center issued this severe thunderstorm watch at Jul 29, 2011, 5:02 PM MDT for 8 counties in Montana; 11 counties in North Dakota. It was in force for 6 hr.

The area

The outline as issued.

The facts

Issued
Jul 29, 2011, 5:02 PM MDT (23:02 UTC)
Expired
Jul 29, 2011, 11:00 PM MDT
In force
6 hr
Issued by
the Storm Prediction Center
Largest hail expected
2 in
Strongest gust expected
60 kt

Counties Daniels County, MT, Dawson County, MT, McCone County, MT, Prairie County, MT, Richland County, MT, Roosevelt County, MT, Sheridan County, MT, Wibaux County, MT, Adams County, ND, Billings County, ND, Bowman County, ND, Divide County, ND, Dunn County, ND, Golden Valley County, ND, Hettinger County, ND, McKenzie County, ND, Slope County, ND, Stark County, ND, Williams County, ND

The radar

The Glasgow radar (KGGW), 165 km from the middle of the area, began a volume at 23:04 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
30%
Six or more combined severe hail and wind reports
70%

Warnings issued inside it

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

IssuedProductOfficeCountiesLasted
Jul 29, 5:29 PM MDTSevere Thunderstorm WarningGGWMcCone, Richland61 min
Jul 29, 5:48 PM MDTSevere Thunderstorm WarningBISBowman42 min
Jul 29, 6:07 PM MDTSevere Thunderstorm WarningGGWRoosevelt, Sheridan53 min
Jul 29, 6:26 PM MDTSevere Thunderstorm WarningGGWMcCone, Richland34 min
Jul 29, 6:30 PM MDTSevere Thunderstorm WarningBISBowman, Slope60 min
Jul 29, 6:51 PM MDTSevere Thunderstorm WarningGGWRoosevelt, Sheridan54 min
Jul 29, 6:57 PM MDTSevere Thunderstorm WarningGGWMcCone, Richland33 min
Jul 29, 7:17 PM MDTTornado WarningGGWRoosevelt, Sheridan28 min
Jul 29, 7:29 PM MDTSevere Thunderstorm WarningGGWDawson, Richland31 min
Jul 29, 7:33 PM MDTTornado WarningGGWDawson, Richland27 min
Jul 29, 7:38 PM MDTTornado WarningGGWRoosevelt, Sheridan22 min
Jul 29, 7:39 PM MDTSevere Thunderstorm WarningBISMcKenzie, Williams51 min
Jul 29, 7:54 PM MDTSevere Thunderstorm WarningGGWDawson, Richland, Wibaux66 min
Jul 29, 7:56 PM MDTSevere Thunderstorm WarningGGWRoosevelt, Sheridan19 min
Jul 29, 8:11 PM MDTTornado WarningGGWRichland34 min
Jul 29, 8:41 PM MDTTornado WarningGGWRichland, Wibaux34 min
Jul 29, 8:58 PM MDTSevere Thunderstorm WarningGGWRichland, Wibaux52 min
Jul 29, 8:58 PM MDTSevere Thunderstorm WarningBISBillings, Golden Valley, McKenzie62 min
Jul 29, 9:41 PM MDTSevere Thunderstorm WarningBISMcKenzie, Mountrail, Ward64 min
Jul 29, 9:47 PM MDTSevere Thunderstorm WarningBISBillings, Golden Valley58 min
Jul 29, 10:43 PM MDTSevere Thunderstorm WarningBISBillings, Dunn, Stark29 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, 11.0 hours before the alert went out and 457 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 2011-07-29Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 1117 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 2011-07-29The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 40 square meters per square second.19395878Sfc1 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
1117 J/kg
Mixed-layer CIN
-137 J/kg
Mixed-layer LCL
1219 m above ground
0-6 km bulk shear
23 kt
0-1 km storm-relative helicity
40 m²/s²
0-3 km storm-relative helicity
72 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.3

Open this sounding in Storm Lab

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Jul 29, 12:59 PM MDTMesoscale DiscussionSPCCarter91 min
Jul 29, 1:54 PM MDTSevere Thunderstorm WatchSPCCarter, Custer, Fallon, Powder River7 hr
Jul 29, 4:46 PM MDTMesoscale DiscussionSPCCarter, Custer, Daniels, Dawson, Fallon, McCone and 5 more59 min

Nearby

Severe Thunderstorm Watches in North Dakota, 2011Severe Thunderstorm Watches in Montana, 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.