Here is the METAR that was taken just after the incident:
"SPECI KDEN 210134Z 29024G32KT 10SM FEW040 SCT100 M04/M18 A2998 RMK AO2 PK WND 28036/0123"
Decoded that means it was a SPECIal observation taken on the 21st at 0134zulu (210134z), keeping in mind that in UTC time it was already the 21st, at that time the wind was blowing from 290 degrees (a little north of west) at 24 knots gusting to 32 knots. Other things of note (M04/M18) meaning the air temp was 25 (M04), and, importantly, the dew point was 0 (M18), so the likelihood of icing was minimal in air that dry. And the final factor for the weather is this:
PK WND 28036/0123
That means there was a 36 knot wind gust from 280 degrees, just 10 degrees off of due west, recorded at 0123z or 6:23PM local time, almost the exact time of the incident. That is a 41mph gust. A passenger reported that they felt the right wing dip first. The gust would have hit at almost a right angle from the left of the plane.
But I'm just a sales guy, I have stayed at a Holiday Inn Express, and I have a meteorologist as a son. He briefs Air Force pilots. His finger is pointing at this as a possible cause.
Updates.
Crosswinds and steering:
http://hosted.ap.org/dynamic/stories/A/AIRPORT_ACCIDENT?SITE=COBOU&SECTION=HOME&TEMPLATE=DEFAULT