Based upon early eyewitness accounts, today’s tragedy on I-75 started with drivers suddenly encountering what’s called a whiteout, with very heavy snow almost instantly dropping visibility to near zero. Take a look at this radar snapshot from the time of the crash. The little circle shows you I-75 where the Rouge River Bridge is. Notice the narrow dark blue band…that’s the whiteout. This blue band is less than a mile wide. You can see how quickly you transition from the light blue (which is light snow) to the dark blue (heavy snow). Drivers moving along at typical freeway speeds would have very quickly found themselves driving from typical light snow into blinding, wind-driven heavy snow in an instant.
--Radar captured at the exact time the I-75 crash happened Thursday morning
The snow bands like this one that developed over Michigan today are caused by strong wind blowing very cold Artic air across the open Great Lakes. In our case, that lake is Lake Michigan. The cold air warms and picks up moisture over the lake, but then has to drop that extra moisture after it hits land again and cools, and snow bands are the mechanism to do just that. Sometimes, these lake effect snow bands don’t make it all the way across the state to Metro Detroit, but due west winds blowing across the southern, “fat” part of Lake Michigan form what we call the I-94 / I-96 Convergence Band…an area of lake effect snow that stretches eastward along or between I-94 and I-96. Today, narrow ribbons of intense snow developed and, while many areas had hardly any snow at all, other areas had whiteout conditions. Since the bands were oriented east-west, people driving north-south – such as those on I-75 – would have driven in and out of these bands.
Whiteout talked about on social media
Word of the I-75 crash and whiteout conditions quickly spread on Twitter Thursday: