Winter is usually the wet season in California as storms roll in off of the Pacific and produce rain along the coast and snow in the Sierra Nevada. The snow is particularly important for California and the west. Snowmelt in the spring and through the early part of summer is counted on to fill reservoirs that supply water to communities and irrigation for agriculture. The winter snowpack in the northern and central Sierra provides about a third of California's water supply.
|Satellite images of the Sierra Nevada range |
in January 2013 (left) and January 2014 (right).
Credit: NOAA Environmental Visualization Laboratory
This series of charts shows the water content of the snowpack as a percent of of the April 1 average. Note that this season to date (pink line) is at or below the driest season on record (1976-1977)
|Source: California Department of Water Resources|
Here is the climatological normal 500 millibar level (about 18,000 feet) pattern for the period from December 1 to January 15. The upper level winds flow parallel to the contours on the map Note how in the contours are fairly flat in the western U.S., which means winds tend to steer Pacific storms into the region.
Here is the mean 500 millibar pattern for the last 45 days. Notice the ridging of the contours in the eastern Pacific. Winds steer Pacific storms northeastward over the ridge into Alaska and western Canada, deflecting them away from the west coast.
It is still early in the snow season, and a few large, wet storms in through March could help the situation. However, the U.S. Drought Outlook indicates that drought conditions will persist through the end of April. In addition to water supply problems the extreme drought conditions will mean a volatile wildfire season.