A powerful snowstorm will wallop a wide swath of Alberta sooner and harder than expected, according to an expanded weather advisory issued Tuesday by Environment Canada.

A snowfall warning is now in effect for Grande Prairie, Yellowhead County and the Municipal District of Greenview, including Hinton and Sturgeon Lake.

A cold rain is expected to turn to snow by Tuesday afternoon.

Image | winter storm

(Environment Canada)

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Between 10 and 15 centimetres of snow is expected to fall before the storm tapers off on Wednesday night.

"A cold front is slumping into Alberta, bringing cold temperatures and precipitation," the snowfall warning says. "Rain will develop later today then change to snow tonight as the temperature cools."

While western Alberta is expected to get the worst of it, a special weather statement has been issued for many other parts of the province.

From Jasper to Cold Lake and from Slave Lake to Fort Saskatchewan, between five and 15 cm of wet snow is expected to fall.

"A cool air mass will invade much of Alberta this week," the special weather statement says.

"A cold front is forecast to drop southward out of the Northwest Territories, bringing with it weather that is decidedly more like winter than summer."

In the higher terrain of western Alberta, particularly between Grande Prairie and Jasper, snow is expected to begin falling Tuesday evening and continue on Wednesday.

The storm will move slowly southward along the foothills and spread east throughout the day and into Wednesday evening. It is expected to track over the Edmonton region on Wednesday night and may reach as far south as Banff by Thursday morning.

Only a few flurries are expected in the capital region. According to the forecast, Edmonton will be mainly cloudy with periods of rain and snow on Wednesday and Thursday.