Well that got unpleasant fast.

The National Weather Service updated today's earlier report -- widespread rain, snow, thunderstorms with small hail -- to a winter storm warning for central and southern Wyoming beginning at midnight today to midnight Tuesday.

"A winter storm warning for heavy snow means severe winter weather conditions are expected or occurring," according to the NWS office in Riverton.

"Significant amounts of snow are forecast that will make travel dangerous. Only travel in an emergency. If you must travel ... keep an extra flashlight ... food ... and water in your vehicle in case of an emergency," according to the NWS.

The winter storm warning affects Dubois in the west through Converse County to the east, with large areas in Sweetwater, Albany and the western edge of Laramie counties.

The snow is expected to become heavy over the mountains, with total accumulations of 12 inches to 18 inches, with locally higher amounts.

Winds will generally be light and variable, from 10 mph to 20 mph Tuesday. However, heavy snow may reduce visibility to under a half-mile at times.

The National Weather Service also has issued a winter storm watch for Campbell County east to the state line, and a winter weather advisory for the length of the Bighorn Mountain Range.

For travel information, visit the Wyoming Department of Transportation's wyoroad.info.