Two storms are on track to slam into the West Coast this week with flooding rain, gusty wind and multiple feet of snow. The first, arriving Tuesday, is only an appetizer to the second, stronger storm quick on its heels.
You know a storm is throwing its weight around when the Weather Service is using phrases such as “potent low,” “plumes of moisture” and “tightening pressure gradient” in its forecasts. They sound dull to a layman’s ears but are enough to make a meteorologist sit up straight and pay attention. That is the kind of language being used this week.
The first storm arrives Tuesday evening, a relatively small one that will strengthen as it approaches the coast. Winds will become gusty and rainfall of up to a half-inch is expected on the Central Coast, with isolated totals of up to four inches in the highest elevations. Flooding seems possible, and the National Weather Service issued a flash flood watch for these regions with particular emphasis on areas that have experienced recent wildfires:
Heavy rain totaling 2 to as much as 4 inches may lead to excessive runoff, rising water levels on area rivers and streams and a threat of flash flooding. Additionally, mud slides, rock slides and debris flows are possible in some locations, especially in the vicinity of the Ferguson, Railroad and Pier burn scars. Some roads may become closed, impassable, or washed out.
National Weather Service office in Hanford, Calif.
[It’s worth noting that National Weather Service forecasters are working without pay during the partial government shutdown. They worked through the Mid-Atlantic winter storm over the weekend, will work through these storms in California and will continue to work without paychecks through storms to come until the government reopens or a bill is passed to pay them now.]
The first storm should bring five to 10 inches of snow in Central Sierra Nevada, and as many as 18 inches in the highest elevations. A winter weather advisory is in effect through late Wednesday afternoon for this round of snow.
That storm is only the prequel to the major trough of low pressure over the Pacific Ocean, scheduled to reach California on Wednesday.
Along the Central Coast near places such as San Francisco, Oakland and Napa, heavy rain will start Wednesday afternoon into Wednesday night. It’s going to be torrential, by San Francisco standards — one inch per hour at times. Winds will be gusty, and lightning will be possible. In the Bay Area; the rain should wrap up by Thursday afternoon.
In the three-day period from Tuesday through Thursday, San Francisco will get up to two inches of rain, and high elevations north of San Francisco could get five inches of rain. The highest elevations south of the Bay Area, particularly Big Sur, could get more than five inches of rain between Tuesday and Thursday.
In Central Sierra Nevada, the second storm will produce three to seven inches of rain in the foothills east of Sacramento over the course of just 36 hours. The National Weather Service issued a flood watch for the foothill region, noting that mudslides or debris flows are possible over recent wildfire burn scars.
The second storm will unload multiple feet of snow in the higher elevations of the Central Sierra — much more than the first. Mountains above 7,000 feet can expect two to four feet of snow, according to the Weather Service in Reno. Below that, 18 to 30 inches are possible. Driving will be difficult, and whiteout conditions are possible on the passes above 7,000 feet, including Donner Pass, Spooner Summit, Carson Pass and Echo Pass.
Correction: An earlier version of this story mistakenly referred to the Hanford office of the National Weather Service as the Monterey office of the National Weather Service.