As many as 25 centimetres of snow could fall in the Ottawa region by Friday evening, as Environment Canada has issued a winter storm warning for the region.

The weather agency upgraded its warning for Ottawa-Gatineau as a low-pressure system from Colorado makes its way northeast, becoming stronger as it moves towards Canada.

"Motorists should be prepared for hazardous winter driving conditions... and adjust travel plans accordingly," Environment Canada said in a warning posted on its website.

"Snowfall rates of two to five centimetres per hour will be quite possible during the height of this snowstorm."

Risk of freezing rain

Brisk east winds and blowing snow will also reduce visibility.

The snow is expected to start falling Thursday evening and it will become heavy late in the night.

CBC Ottawa climatologist Ian Black said he expects the leading edge of the storm to hit Ottawa by about 11 p.m.

There is also the risk of freezing rain Thursday evening and overnight as the temperature holds steady just below the freezing mark.

About 10 to 15 centimetres of precipitation is expected to fall.

The storm will continue Friday with more risk of freezing rain in the morning — about 10 centimetres is expected. The snow will taper off Saturday as the storm moves away across eastern Quebec, the weather agency said.