June 21 Severe

Overview: After an early round of severe thunderstorms this morning in eastern Iowa, the skies lit up once again in the afternoon. Storms began moving into northwestern Iowa in the early afternoon hours, with new development just ahead of this line in northcentral Iowa and another newly developed line in west-central Iowa. Both of these clusters of thunderstorms were quickly able to become severe and even tornadic in some cases as they moved across the state. Continued development of storms occurred to fill in all of the gaps in the cells, essentially blanketing the state in severe thunderstorms by this evening. To go over a few of the reports today, tornadoes were reported near Eagle Grove (Wright county), Shell Rock (Butler county), Ames (Story county) and Waterloo (Black Hawk county). Several dozen reports came in with large hail and damaging winds, most of the hail reports were an inch or less and many of the wind reports were not greater than 65 mph. Besides the tornadoes, the worst report of the day came in at 3 miles north of Renwick in Humboldt county, where 2.50" diameter hail fell around 3:20 this afternoon.

11:25 AM Update: New SPC outlook for today has now upgraded to Moderate for portions of SD/NE/MN and Iowa. Storms continue to develop in southeast SD, these should continue to move east/southeast this afternoon and eventually make their way into northwest Iowa early this afternoon. If these storms as well as others that develop remain discrete during the afternoon hours, potential for very large and damaging hail is there along with the chance of a few tornadoes. However, the possibility exists for thunderstorms to congeal into more of a linear line and thus the wind threat would become higher, with some large hail being possible.

10:15 AM Update: Severe weather already occurring this morning across the northern plains, including parts of eastern Iowa where warnings were posted for large hail earlier near the Iowa City area. Those thunderstorms continue to move out of the state while new storms are expected to move in this afternoon. One severe/tornadic thunderstorm is already occurring in southeast South Dakota, this storm is expected to continue and allow other storms to develop near it during the rest of the morning hours. For this reason, Severe Thunderstorm Watch #433 has been issued for areas of SD, MN and Iowa. The northwest 9 counties of Iowa are included in this watch that serves for mainly large hail and damaging winds, it is valid until 4 PM this afternoon.