This week's drought monitor update increased the coverage of exceptional drought (D4-highest severity rating) in the Bay Area for all of Napa and Contra Costa counties. Exceptional drought levels also expanded across much of interior Northern California, including the Sacramento Valley.
According to Dan McEvoy, applied climatologist with the Desert Research Institute and Western Region Climate Center, it is very likely the state shifts completely into exceptional drought before the next rain season arrives.
"I do think we will see pretty much the entire state likely to be in D4 (exceptional drought) as we head into the middle of summer," McEvoy said.
So, what has led to such a rapid acceleration of Bay Area drought severity?
"To give some context, it has been drier than those 2012-2015 years," McEvoy said. "Some different regions like the San Francisco Bay Area hydrologic region, it has been the fourth driest water year since 1895, so 126 years worth of data, and the year before last year was very dry, so this water year October to April and last year were drier than any of the 2012-2015 years individually."
What it also likely means is increased demand on water resources will continue especially as the Sierra snowpack dropped to 0% of average as of May 27 -- about three weeks ahead of schedule in a more typical precipitation year. Near-record dry vegetation once again sets the stage for a prolonged and more intense fire season as well.
Given the expected intensity of drought conditions by the end of this summer, McEvoy explained it will take an above average rain/snow year to try to reverse drought statewide and there have been recent examples of this taking place, as seen before from 2015 into 2016.
"Reservoirs were really low and they can fill up in one big year," McEvoy said. "It's hard to say where we go from here if we have one more dry year considering how bad things are right now."