First, the hottest storm system will extend from Wednesday to Thursday, holding snow at very high altitudes. Later, very cold and significant weekend storms in places like Washington and Oregon could bring snow closer to sea level.
This will bring the opportunity for a white Christmas to cities like Seattle and Portland where only 1% to 3% of such romantic – or annoying – holiday weather will be.
Meanwhile, in the Sierra Nevada mountains, isolated snow can reach the second floor of a building – up to 10 feet, according to meteorologists at the Sacramento National Weather Service’s office. Most people in Sierra Nevada will see 5 to 8 feet of snow, making road conditions throughout the region dangerous.
“Traveling across the Sierra can be difficult on holiday weekends,” the Reno Meteorological Office said Wednesday morning.
Areas west of the Intermountain will also measure snow beneath, which will delight ski enthusiasts.
At low altitudes approximately 1 to 3 inches of rain, sometimes heavy, can affect road conditions and cause flight delays. Sudden flooding is also possible, and there will always be mudslides when this amount of rain wets the area.
While this will hamper travel and reduce Christmas plans, rain and snow are a welcome development, with more than 97% of western areas still dry after recent atmospheric rivers provided inches of rain and foot snow.
Atmospheric rivers are important for the water supply of the West Coast, accounting for almost half of the West Coast’s annual rainfall.
As the name implies, atmospheric rivers are streams of thousands of feet of moisture in the sky. They are 250 to 375 miles wide and are said to carry 7.5 to 15 times more steam than the average water flow at the mouth of the Mississippi River.
On a scale of 1 to 5, this week’s Atmospheric River is forecast to be the highest Type 3 in California and 5 in parts of Baja California.
Vacationing to the rest of the United States seems to be less bad
The weather for the country, overall, will be good for the millions who travel during the holidays.
Beyond the West, the Great Lakes and New England may be in trouble because a pair of systems can slightly affect travel with some typical winter weather.
The rest of the United States is quiet and warm during the holidays.
Cities in the south reach 20 degrees above average at this time of year, peaking in the 70s and 80s – and close to 90 on the Texan-Mexican border – on Saturday.
“On Christmas Day, more than 30 records could be set for Southeast Texas,” said CNN meteorologist Dave Hennan.
Conversely, the high temperature of the day on the US-Canadian border will be close to zero.