Blizzard Warning now in effect as Atmospheric River brings feet of snow to the Sierra

SOUTH LAKE TAHOE, Calif. - The warnings have been coming for over a week, and now the day weather experts have been warning us about is here. For snow that has been measured in inches so far this winter, a big change hits Lake Tahoe and the Sierra starting Tuesday night when it will be measured in feet.

The National Weather Service (NWS) in Reno has now upgraded the storm warnings to blizzard level.

An atmospheric river (AR) is heading to the west coast this morning, spreading from Canada to Southern California. The extra moisture with a cold air mass will bring several feet of snow to upper elevations, over two feet to four feet of snow at lake level, depending on location.

"All the main ingredients are there for a blockbuster storm" said NWS Reno meteorologist Mark Deutschendorf. He said this is a vigorous storm that will bring whiteout conditions, possible road closures, and snowfall of up to four or five inches per hour for a long period of time on Wednesday morning.

"This atmospheric river is the big one," he added.

On January 26, NWS Reno upgraded the Winter Storm Warning in the Tahoe and Mono County area to a Blizzard Warning, in effect from 10:00 p.m. Tuesday to 4:00 a.m. Friday. The first part of the storm will have the strongest winds and heaviest rates. There could even be thundersnow along the first bands of snow in the Sierra and Lake Tahoe. That could be early morning Wednesday.

There is also a Backcountry Avalanche Watch in effect Tuesday evening through Friday morning for the Sierra including the Tahoe Basin, for EXTREME Avalanche danger. Avoid all backcountry activity during the upcoming major winter storm this week.

The NWS forecast for South Lake Tahoe through Friday:

Today - Snow likely after 4pm. Mostly sunny, with a high near 28. Southwest wind 5 to 10 mph increasing to 10 to 15 mph in the afternoon. Winds could gust as high as 25 mph. Chance of precipitation is 60%. Total daytime snow accumulation of less than a half inch possible.

Tonight - Snow. The snow could be heavy at times. Low around 20. Breezy, with a south wind 15 to 20 mph, with gusts as high as 35 mph. Chance of precipitation is 100%. New snow accumulation of 5 to 9 inches possible.

Wednesday - Snow. The snow could be heavy at times. High near 32. Breezy, with a south wind 15 to 25 mph, with gusts as high as 40 mph. Chance of precipitation is 100%. New snow accumulation of 6 to 10 inches possible.

Wednesday Night - Snow. The snow could be heavy at times. Low around 26. South wind around 10 mph. Chance of precipitation is 100%. New snow accumulation of 7 to 11 inches possible.

Thursday - Snow. The snow could be heavy at times. High near 37. South wind around 5 mph. Chance of precipitation is 100%. New snow accumulation of 7 to 11 inches possible.

Thursday Night - Snow. The snow could be heavy at times. Low around 21. Southwest wind around 5 mph. Chance of precipitation is 90%. New snow accumulation of 3 to 7 inches possible.

Friday - A 50 percent chance of snow, mainly before 4pm. Partly sunny, with a high near 34. New snow accumulation of less than one inch possible.

Friday Night - A chance of snow, mainly after 10pm. Mostly cloudy, with a low around 19.