A La Nina weather pattern has developed in the Eastern Pacific Ocean. Strong trade winds across the equatorial region push warm surface waters to the west; this leads to upwelling of colder water off the west coast of the Americas.
In a typical La Nina year, precipitation increases in the Pacific Northwest (including the northern half of California) and mountain snowpacks are generally deeper across the West (excluding the Desert Southwest). Evidence of this pattern is currently unfolding as soaking rains fall from San Francisco to Seattle and heavy snows coat the Cascades, Sierra Nevada and Great Basin Ranges.
The La Nina precipitation will likely bring an end to the Western Fire Season but will offer only modest relief from the prolonged drought that grips most of the American West. Our warming climate will surely exacerbate the drought and might even prevent the formation of future La Ninas.
