California in a state of chronic drought

California entered the winter full of hope that this season would repeat the amazing feat of the 1982/83 winter. In that strong El Nino season, California’s snowpack increased to a record 230 percent of average.

California is in a state of chronic drought – this time last year the snowpack was a miserly 5 percent of its average amount.

During the past one month, most pacific storms directed towards the US northwest, as they have all season. Seattle has seen 1,100mm of precipitation since last October, some 156 percent of normal.

The storm track drifted far enough south in March to affect central California but not far enough to help the southern part of the state. Los Angeles has seen only 167mm of rain since October 1, only 49 percent of average.

An atmospheric river

The heavy precipitation that affected the northern two thirds of California during the first two weeks of March was a river of hope after the dry February. Seasonal averages were revived to around normal for the central part of the state, and a bit above normal in the northern locations.

The mountain areas fared especially well as the 483mm of rain and melted snow that accumulated in Blue Canyon (central Sierra) attest.

Northern California has enjoyed an abnormally wet winter and the state’s two largest reservoirs, Lake Shasta and Lake Oroville, are for the first time in almost four years at or above their historical levels for March 31. Folsom Lake was forced to release water during the month owing to over-capacity.

Snowpack

Heavy snowfall blanketed the central and northern Sierra during March. Sugar Bowl Ski Resort, near Lake Tahoe, reported an astonishing 3.2 metres of snowfall between March 5 and 14. However, despite the big snows, the snowpack remains below normal as of the end of March at 87 percent of average.

Although this is a bit discouraging, it is a huge improvement over where we stood at this time last year.

April can sometimes bring heavy rain and snow to the state. The water season is, for the most part, over and the snowpack in the mountains will now begin to melt. Unfortunately, it is now obvious that this winter’s powerful El Nino has come up short for California as far as precipitation is concerned.

In the long term, the situation is still as grave as ever with ground aquifers almost depleted. A single normal rainy season is not going to mitigate this issue and more than half of California is still officially in extreme or exceptional drought.

Christopher C Burt, Weather Historian, contributed to this report