It’s been very dry this winter is Southern California as a drought continues to impact much of the region. The winter season is supposed to be their wet season, but the wet weather has been scarce so far. A pattern change will likely allow for rain to fall as we look ahead to next week, however.
The models the past several days have now been hinting at the development of a very potent, upper-level low that will position itself just off the California coast. This low will draw in tons of moisture off from the Pacific Ocean and into Southern California starting mid-next week, and will possibly continue all the way through next weekend as the upper-low drifts toward the Southwest US.
Low pressure spins counter-clockwise, so that strong flow will allow for very anomalous moisture to stream into the Southwest, as shown by the European model below. This is a big indicator of the risk for heavy rain across the region, including cities like Los Angeles, San Diego, and even Phoenix. Based on what the model guidance has been forecasting as of late, there is the potential for a widespread one to two inches of rain to fall next week.
Since October 1st, which is the start of the rainy season, only 1.89 inches of rain as fallen through February 9th in Downtown Los Angeles. On average to date, 8.28 inches of rain should have fallen, making for a 6.39 inch deficit. Based on our current forecast, that deficit will likely not be wiped out within the next ten days, but about half of it could be.
Looking even further out in time to the end of February, as that upper-level low departs the region, a trough of low pressure may swing into the Western U.S. the following week, allowing for a widespread rain for the West Coast in addition to much-needed mountain snow in the Sierras. Of course this is very far out in time and the forecast is uncertain, but the long-range outlook definitely paints some hope for this drought-stricken state.