From the National Weather Service Offices in Des Moines & Valley, NE:

For Cass, Audubon, Crawford, Carroll and Guthrie Counties….Winds will increase out of the south today from 20-30 mph with gusts to near 45 at times. Thunderstorms will move into the area late this afternoon and tonight. Heavy rainfall is possible with some storms, which may also be severe. Large hail and damaging winds are the primary threat from these storms. An isolated tornado cannot be ruled out initially.

For Monona, Harrison, Shelby, Pottawattamie, Mills, Montgomery, Fremont & Page Counties…Thunderstorms are expected to develop after 3-p.mn. generally north of I-80, however the most likely area they will initially develop will be in northeast Nebraska. Throughout the evening, additional thunderstorm development is expected over much of eastern Nebraska and Southwest Iowa. These storms could persist into the overnight hours. Any storms that do develop are capable of producing large hail and damaging winds, mainly during the late afternoon and evening hours. Later in the evening and overnight, the storms may produce locally heavy rain.

Spotter activation may be needed after 3-p.m. across the affected counties.