Linn County Emergency Management met with the NWS on Friday afternoon to discuss the storm damage early Friday morning near Pleasanton and the overturned semi near the La Cygne exit on US 69. After reviewing the photos of the damage west of Pleasanton the NWS felt we had a unidirectional microburst or gustnado type event.
We typically think of a microburst as an event that radiates strong, damaging winds out in all directions from its center. This is true for single cell thunderstorms, however, when this occurs in a multicell squall line thunderstorm the winds can be directed in a single direction as occurred on Friday morning.
The other possibility is a gustnado which is a strong whirlwind at the leading edge of a storm front or squall line. Gustnado's are usually very short-lived.
In either case the wind speeds were likely above 80 MPH.