A Wednesday evening snowfall surprised motorists and created traffic gridlock on untreated roads across the Washington region.

While the city prepares for the arrival of a potentially historic storm on Friday, motorists were caught off-guard during a storm system that dropped about an inch of snow Wednesday. Many roads were untreated, creating lengthy, slow-moving commutes.

Here’s a look at the road conditions across the D.C. area on Wednesday. Roads were expected to be covered in many more inches of snow to end the week.