Headline

From California to Virginia, Winter Storminess Will Gird the U.S. This Weekend

 United States

Winds at the jet-stream level (250 mb, or roughly 33,000 feet) were howling across the southern U.S. at speeds topping 120 mph in spots on Friday, January 6, 2017. The energy was undercutting a massive ridge of high pressure extending north into Alaska and eastern Siberia, with a weaker jet arcing above the ridge (top left). Image: Climate Reanalyzer/University of Maine

The atmospheric river predicted for days to strike the U.S. West Coast is still on track to arrive within about 100 miles of San Francisco Bay and proceed headlong into the Sierra Nevada over the weekend. Carrying vast amounts of moisture--more than four standard deviations above the mean--this onslaught of strong southwest flow should deliver widespread rains on the order of 4” or more from late Saturday into Monday across much of central California, including the cities of San Francisco and Sacramento. Single-day rainfall records include 5.59” for San Francisco International Airport (January 4, 1982; records go back to 1945) and 3.77” at Sacramento Executive Airport (October 13, 1962; records go back to 1941).