Fairfax County school officials announced late Wednesday that they would delay the start of schools by two hours on Thursday due to weather, as did the school systems in Alexandria and Manassas. The Prince William County school system is canceling Thursday classes altogether.

Prince George’s County school officials said via the system’s twitter account that they would make decisions about a possible delay or closure early Thursday morning.

Fairfax County school officials made the call for a delay after police were called to more than 50 car accidents across the county because of a surprising snowfall that snarled rush-hour traffic, with cars skidding and colliding while navigating untreated roads that quickly became slick with ice. More snow and low temperatures were forecast for Wednesday night into Thursday, and in a message to parents, the school system said it would evaluate whether classes should be canceled for the day early Thursday. The late start means that morning field trips and morning preschool will be canceled.

[See the weather-related closures and delays across the region.]

The decisions to cancel and delay classes come in advance of what is predicted to be a historic snowstorm that is expected to throttle the D.C. area late Friday and into Saturday, with possibly close to two feet of snow in some areas.

[Severe, long-duration snowstorm begins Friday, blizzard watch in effect]

As of Wednesday night, only the University of Maryland in College Park had announced it would cancel classes Friday. Arlington Public Schools had not decided whether to close schools but encouraged families to make arrangements for childcare on Friday should the system shut down ahead of the storm’s arrival.