The still infant Winter of 2012-2013 appears to be much more active, cold, and wet than the previous Winter. Albeit, last Winter was historically dry and warm, so beating it in terms of precipitation and cold shouldn't be all that hard. Nonetheless, the second powerful storm in a week is set to slam into the West Coast before tracking across the Rockies and into the Plains into Christmas. Seeing as this storm will cause a variety of weather conditions to many parts of the country over several days, I want to take this day-by-day starting with Sunday.
Models are in good agreement that a powerful Pacific storm will slam into the California coast beginning Sunday afternoon. This storm will actually be in the heels of another storm that already dumped over a foot of snow in the Sierra Nevadas. Winter Storm Warnings for the same area of the Sierra Nevadas warn of an additional snowfall accumulation of 2 to 3 feet is possible above 7,000 feet, while 3 to 5 feet is possible at the highest elevations. In addition, southwest winds are expected to gust to 50 mph in the lower elevations, while gusts along the ridge could be as high as 100 mph.
Above is the HPC precipitation forecast for Sunday and Monday during the heart of the storm as it pounds California. Note the bull's eye of precipitation along the Sierra Nevadas, but also significant rain expected for much of Northern California. Areas in and around the San Francisco Bay Area could experience upwards of 1-2 inches of rain, while areas to the north of San Francisco could receive over 2 inches of rain.
We have put together a page that you can use to track this storm and its various components. On it you can find snowfall totals and measured wind gusts, along with valid webcams that will show you exactly what it looks like outside.
Good News and Bad News
Let's start with the good news regarding this storm. Last Winter, ski resorts throughout the West struggled through a very dry season that saw sales plummet due to lack of snow. So far this December, snowfall has been above normal and ski resorts are reporting healthy snowfall amounts. Mammoth Mountain Ski Area is already reporting a base of 84 inches before this next storm even hits. This will translate to a healthy beginning to the ski season and allow the region's ski resorts to get back on their feet.
Now, the bad news. Christmas is two days away. Thus, many, many people will be on the road trying to get to their Holiday destinations. The main thruway into and out of California in the Sierra Nevadas is Interstate 80, which goes up and over Donner Summit. Below is the webcam from Donner Summit that you can use to track what Interstate 80 looks like.
It gets worse. As of this writing, tire chains were required on all vehicles without 4-wheel drive over Donner Summit. With the excess moisture hanging around, bringing leftover snow before this storm even hits, it is not impossible to think that tire chains will continue to be required before this next storm even hits. With the addition of several more feet of snow, it is possible that I-80 could close because it could become too dangerous. This usually happens several times per year, but it just so happens that this is two days before Christmas. The bottom line is that you should plan ahead and count on extra travel time in and around California over the next several days.
Storm's Next Phase
As this powerful storm exits California, it will move into the Great Basin and the Rockies before strengthening in the Plains. I will discuss the effects of the storm as it moves into the eastern half of the country in my next blog, but you can get an idea of what is currently expected by looking at the HPC precipitation forecast for Christmas. Needless to say, it could be a cold Christmas for the Plains, while the Southeast could be greeted by a wet Holiday.
Year End Review
For a beautiful recap of the year's top 10 weather events, you can watch the following video. This animation combines over 8,000 satellite images into one stunning video.