Will a Wetter Pattern Change Help the California, Southwest Drought?

Linda Lam
Published: April 9,2016
A pattern change will continue to bring rain and some mountain snow to parts of the drought-stricken West and Southwest the next several days, providing some additional relief from the multi-year drought.
Record daily rainfall amounts were reported in southern Nevada on Saturday, including 1.55 inches for the day as of 5 p.m. at North Las Vegas. Parts of the area were under a flash flood warning for a time Saturday afternoon, as a result of locally heavy rain.
Parts of the San Joaquin Valley and Mojave Desert picked up heavy rain Friday into early Saturday. Over 2 inches of rain was measured in Merced, California. Flooding was reported in Clovis Saturday morning, and some roads were flooded Friday near Victorville and Barstow, California.

Current Radar

This is all thanks to an overall gyre of low-pressure in the upper atmosphere with several embedded disturbances that will only slowly pivot through California and the Desert Southwest through Tuesday.

Enhanced Satellite, Pressure, Winds

(MORE: 11 Photos That Show California's Drought Situation Is Improving)
Below we break down the chance for wet weather over the next few days.

Wet Forecast

Scattered showers and thunderstorms will persist into Sunday across parts of California, the Great Basin and parts of the Southwest. By Sunday night snow will also fall in portions of the Rockies in Colorado and Wyoming.
(FORECASTS: Fresno, California | Phoenix | Denver)

Sunday's Forecast

Another round of wet weather will be found across central and southern California as well as into Nevada, Arizona, Utah, New Mexico and western Colorado Monday into Tuesday.
After that gyre is kicked out, a colder Pacific frontal system will sweep into the West Coast around the middle of the week, bringing another round of wet conditions to the region, with the possible exception of Southern California. This is good news for the region, especially California, due to the ongoing drought.
(MAPS: 7-Day Rain/Snow Forecasts)

Drought Relief?

This pattern change is good news for California, where drought remains a concern and any precipitation is beneficial.

California drought monitor analysis from April 5, 2016. The darkest red shading corresponds to the area of most exceptional drought. (NOAA/USDA/NDMC)

As of April 5, 32 percent of the state is in exceptional drought, the highest category, according to the United States Drought Monitor.
This is an improvement from April 2015, when 44 percent of the state was in the exceptional drought category.
This rainfall is also coming at a time of year when the chance for rain really begins to decrease. The wet season, which is when most of the rain and snow in California occurs, typically runs from October through February. Beginning in March and continuing through the spring there is a significant decrease is rainfall.

Downtown Los Angeles is a good example. Los Angeles receives 73 percent of its average annual rainfall during the October through February time period. An average April only sees 0.91 inches of rain, compared to the average of 3.8 inches that is measured in February.
We did see some drought relief this past fall and winter, but not the relief that many were hoping for given the strong El Niño. This early April rainfall will not be a drought-buster but it will be welcome.
(MORE: California's Time Is Running Out For Drought Relief)
Rainfall totals are not expected to be substantial, with most locations likely receiving under an inch through Monday. However, there will be pockets of heavier rainfall.
The National Weather Service has issued flood watches for recent areas burned by wildfires in L.A. and Ventura Counties. It doesn't take heavy rain to trigger debris flows in these areas, given the lack of living vegetation anchoring the soil in place.
Having said all that, it's mountain snowpack, specifically in the Sierra, that is most crucial for reservoir replenishment as spring snowmelt.
(MORE: Shasta Lake Now Above Capacity)
Snow levels will remain high through Tuesday, with snow falling mainly above 7,000 feet. However, the highest elevations of the Sierra Nevada may see more than a foot of snow through Monday, which is very beneficial to the region as approximately one-third of California's drinking water comes from the Sierra snowpack.
Snow levels may lower to around 5,000 feet by midweek with the Pacific front, which may dump heavier snow in the Sierra.

Rainfall Forecast Through Monday

MORE: El Niño's Effect on California, Winter 2016 (PHOTOS)