Thunderstorm Wind — Bremer, Butler and Black Hawk, Iowa

1994-05-30 · near Finchford To, Bremer, Butler and Black Hawk, Iowa

Event narrative

A cold front moved southeast into Iowa during the afternoon and early evening hours. Most of the dynamics with the front were well to the north of Iowa and moisture was quite limited. Surface dew point temperatures were in the upper 50s to middle 60s, with 850 mb dew point temperatures only around +10° C. The airmass was also capped during the day. Even so, it was quite unstable with CAPE values in the 3000-4000 J-Kg-1 range. Strong convection developed over Minnesota and Wisconsin. During the evening hours it developed southwest into Iowa. Strong thunderstorms moved across north-central and northeast Iowa during the evening, producing large hail. The first hail reports came from Worth County. Hail about the size of ping pong balls fell in Northwood. Mitchell, Floyd, and Butler Counties received the most significant hail, ranging from dime-size to golf ball-size. The storms produced gusty winds, but most of the wind gusts were below severe levels. One cell produced a wind gust of 60 mph on the Bremer, Butler, Black Hawk County lines between Finchford and Janesville.

Source: NOAA Storm Events Database, event_id 10321975. Narrative written by the NWS forecast office that issued the report.