Heavy Rain and Flash Flooding Threat in Montana; Severe Thunderstorms in the Middle Missouri Valley

A low pressure system will bring heavy to excessive rainfall and high winds across Montana this afternoon. Heavy rainfall totals may lead to scattered flash flooding concerns. A line of showers and strong to severe thunderstorms will move into the mid Missouri Valley region this afternoon producing severe winds and isolated large hail with stronger storms. Read More >

May 11, 2011

Severe Weather Event

Two Confirmed Tornadoes

Damaging Winds & Large Hail

National Weather Service Radar (KUEX) loop
from 1130 am CDT to 420 pm CDT on the left. NWS Hastings coverage area located within orange outlined area labeled "GID".

(Click Radar Loop To Enlarge)

Thunderstorms entered north central Kansas midday on Wednesday, May 11, 2011, and rapidly lifted north across south central Nebraska. These storms developed to the east of a strong upper level low pressure system centered over Colorado, and in the vicinity of a nearly stationary surface front stretched from southeast Colorado to east-central Nebraska. The thunderstorms initially produced large hail the size of quarters, and as the line of storms became more organized, damaging winds of 60 to 70 mph were common for locations in south central Nebraska mainly east of Highway 281.

Hamilton County: As the line of storms intersected the nearly-stationary frontal boundary in south central Nebraska, a few tornadoes were reported and at least one tornado was confirmed. The confirmed tornado touched down approximately 6 miles north of Hampton in Hamilton County Nebraska, and tracked northward to approximately 5 miles south and 2 miles east of Hordville, where it then lifted. In total, this tornado overturned 3 irrigation pivots, destroyed 2 grain bins and downed 7 power poles. This tornado was rated a weak EF-1, with an estimated top wind speed of 95 mph and maximum width of 200 yards along an approximately 3.5 mile path.

Polk County: This line of storms continued to the north and resulted in another tornado, this time affecting the central Polk County town of Osceola. This tornado was witnessed by a number of spotters, including the Emergency Manager and Fire Chief. The initial touchdown was approximately 3/4 of a mile south of Osceola, but lifted as it approached the town. It then touched down once again on the northeast edge of town, before lifting for the final time approximately 3/4 of a mile to the north. This tornado was rated a weak EF-1, with an estimated top wind speed of 90 mph and a maximum width of 75 yards along an approximately 2.5 mile path.

Adams County: There may have had a brief tornado touchdown in the vicinity of Ayr, but no damage has been reported in this area to survey.

Tornado Damage Survey Maps and Preliminary Storm Reports
are shown on the graphics below. (Click on images for more information.)


Map from tornado in Hamilton County.	Map from tornado in Polk County.


*Preliminary Storm Reports.*	*24 Hour Rainfall Totals.*

Radar Images, Surface Chart, Storm Damage Photographs (Click on any image to enlarge)


KUEX Radar 0.5 Degree Storm Relative Velocity at 1837 UTC of possible tornado southwest of Ayr, NE.	KUEX Radar 0.5 Degree Storm Relative Velocity at 1952 UTC of tornado north of Hampton, NE.

KUEX Radar 0.5 Degree Storm Relative Velocity at 2006 UTC of tornado north of Osceola, NE	Surface plot and analysis at 18 UTC.

Power poles snapped from possible tornado 6.5 miles north and 0.5 mile east of Hampton on County Road 20 in Hamilton County.	2 grain bins destroyed at farm north of Hampton

Grain bin carried from farm north of Hampton	Snapped power pole north of Hampton

Damage to the porch at residence on the far northeast corner of Osceola.	Shed damage at residence on the far northeast corner of Osceola.