You've heard it before: Do your Christmas shopping early.

But now it's the weatherman who is saying it - predicting the fourth snowstorm this week late Saturday.Meanwhile, snowstorms on Friday closed Big Cottonwood Canyon and one lane of the highway in Provo Canyon. An avalanche in Little Cottonwood Canyon trapped two cars and a UTA bus, and snow clogged traffic all along the Wasatch Front.

Ed Carle, a forecaster at the National Weather Service's Salt Lake Forecast Office at the International Airport, said there is a 30 percent chance of snow again Saturday afternoon and an 80 percent chance of snow Christmas Eve and Christmas throughout the state. He said there has been a winter storm watch on since Friday.

"There is every reason to believe we'll have 4 to 6 inches of snow in the valley and a foot of snow in the mountains by Sunday. I suggest that people who still have some Christmas shopping to do - do it Saturday morning or early in the afternoon Saturday and get ready to bundle up by evening."

Carle said temperatures Saturday and Sunday are expected to be in the 30s with lows Christmas Eve in the upper 20s and lows Christmas night near 20.

Weather forecasters have been right on target the past two weeks, predicting high winds in Salt Lake and Davis counties and snowstorms along the Wasatch Front.

Forecasters predicted at least two days in advance 80-mph winds Wednesday night, Dec. 14, and the following day. Sure enough, by 9 p.m. Wednesday, high winds were beginning to cause damage in Davis and Salt Lake counties, and the problems increased through the night and into Thursday, Dec. 15.

This past week, forecasters have predicted without error nearly the exact time of day when the snowstorms were to begin.

Carle said he and other forecasters are not always able to be precise when predicting the weather. "But when everything points to a particular storm, when all our indicators fall along the same direction, then we can be pretty sure of what the weather is going to be.

"And everything points to another major winter storm Saturday night and Sunday."