Drought Status Update for California-Nevada

Drought forecasted to continue as wettest months come to a close

Key Points

Moderate-to-Exceptional drought remains across California and Nevada as the region’s wettest months come to a close. Notably, conditions deteriorated in central Nevada over the past few weeks.
The storms through February have not significantly improved drought conditions throughout much of the region. Precipitation totals and snowpack remain below normal.
Dry conditions are expected to close out February throughout the region with similar dry seasonal (monthly through spring) forecasts.
Preparation for continued drought impacts (e.g., pasture conditions, water supply, fire risk) should be considered, especially in the driest areas.

U.S. Drought Monitor Conditions: California-Nevada | February 23, 2021

U.S. Drought Monitor

The U.S. Drought Monitor (USDM) is updated each Thursday to show the location and intensity of drought across the country. Drought categories show experts’ assessments of conditions related to dryness and drought including observations of how much water is available in streams, lakes, and soils compared to usual for the same time of year.

California/Nevada conditions as of February 23, 2021:

85% of California is experiencing Moderate to Exceptional Drought (D1-D4), with 26% in Extreme Drought (D3) and 3.75% in Exceptional Drought (D4)
California population in drought: 26,960,767
100% of Nevada is experiencing Moderate to Exceptional Drought (D1-D4), with 36% in Extreme Drought (D3) and 40% in Exceptional Drought (D4)
Nevada population in drought: 2,700,553

Source(s): NDMC, NOAA, USDA

U.S. Drought Monitor Categories

Last Updated: 02/23/21

85%

of California is experiencing Moderate to Exceptional Drought (D1-D4)

26.96 Million

people in California are in Moderate to Exceptional (D1 - D4) Drought

100%

of Nevada is experiencing Moderate to Exceptional Drought (D1-D4)

2.7 Million

people in Nevada are in Moderate to Exceptional (D1 - D4) Drought

Current Conditions

According to the U.S. Drought Monitor, drought conditions have slightly improved over the last few weeks in pockets of northern coastal California and northern Nevada. Conditions have deteriorated in central Nevada with expansion of D4 (Exceptional Drought).
Northern Nevada received substantial precipitation in the last 14 days, as did parts of far northern California. The Northern Sierra 8 station precipitation index stands at only 36% of its normal water year total precipitation. Southern California and Nevada remained dry over the last two weeks, with 2021 water year precipitation for Los Angeles standing at 26% and that for Clark County, Nevada mired at 11% of normal water year totals.
A summary of Atmospheric Rivers through February is available here.
According to the California Department of Water Resources, the statewide average snow water equivalent (SWE) of the Sierra Nevada snowpack is 66% of normal for this date (54% of April 1st average). SWE values in the Upper Colorado River Basin have improved over the last couple of weeks and are ~90% of normal for this date.
Most reservoir levels are below normal in the northern, central, and southern Sierras, and Lake Tahoe is at near-normal levels for this time of year.
The evaporative demand (the thirst of atmosphere) is above normal throughout the West, further drying the landscape. The odds of above-normal evaporative demand for the region over the entire water year are high after only 4 months, between 70%-100% odds.

Percent of Normal Precipitation: Last 14 Days vs. Water Year to Date

Percent of normal precipitation for California and Nevada through February 23, 2021.For the past 14 days (left image), CA-NV shows a divide between the northern half of NV and far northern CA, which received 100%+ normal precipitation, while southern CA-NV and central CA received <50-70%. Since the start of the water year (right image), the percent since the start of the water year shows most of CA-NV below 50%-70% or less of normal with small areas between 80%-90% or greater. — Percent of normal precipitation for the last 14 days (*left*) and since the start of water year (*right*). Valid through February 23, 2021. Source: High Plains Regional Climate Center.

Snow Water Equivalent Percent of Median: February 23, 2021

Snow water equivalent for the Western U.S. as a percent of the NRCS 1981-2020 median, valid February 23, 2021. SWE in the Sierras is primarily between 50% and 75%. — Snow water equivalent percent of 1980-2010 median as of February 23, 2021. For an interactive version of this map, please visit the Natural Resources Conservation Service.

Evaporative Demand (ETo) for Water Year 2021

October 2020 to February 1, 2021 evaporative demand (ETo) anomalies map. Much of the western U.S. (especially the southwestern U.S.) is 1-4 standard deviations above normal.

Odds of exceeding 100% of normal evaporative demand (ETo) for the western U.S. Much of the western U.S. (especially the southwestern U.S.) has high odds of surpassing normal ETo for the water year. — Evaporative demand (or ETo, the atmospheric thirst driving evapotranspiration) anomalies throughout the West for the first four months of the 2021 water year (October, November, December, January) shown in (top) standard deviations from normal and (bottom) odds of exceeding normal for the water year. California and Nevada are currently between 1-4 standard deviations higher than normal, and the odds of exceeding normal evaporative demand through the rest of the water year is between 70%-100%. See the most recent data on the Climate Toolbox.

California/Nevada Soil Moisture Drought Intensity: February 22, 2021

California-Nevada shows soil moisture drought intensity as of February 22, 2021. 3-D4 is present predominantly over parts of the Sierra and southern NV and near the CA-AZ and CA-OR borders. D0-D2 is present over much of the remaining area with the exception of pockets of central CA and northern NV. — Soil moisture drought intensity for California and Nevada. Valid February 22, 2021. Source: UCLA Drought Monitor.

Water Storage in the Western Sierra Nevada and Lake Tahoe

Two time series graphics showing water storage tracking (reservoirs + snow pack) for October 1, 2020 through October 1, 2021 (X-axis) for the 28 Western Sierra reservoirs as well as (above rim) Lake Tahoe. In the Western Sierra, reservoir normals are below normal and reservoir+snowpack are well below normal while Lake Tahoe is near normal. — Water Storage compared to 1981-2010 is below normal in the Western Sierra Nevada and in Lake Tahoe through February 22, 2021. Source: CNAP Water Storage Tracking.

Drought Impacts

The USDA Farm Service Agency in California reports that ranchers are reporting, most recently in Solano and Sonoma counties, significant losses in cattle feed, and many have been supplemental feeding for months.
Recent CMOR reported severely dry conditions in Esmeralda County, Nevada, providing on the ground observational support to U.S. Drought Monitor degradations in the area this week.
Marin County, California, water suppliers are considering drought restrictions.
The U.S. Bureau of Reclamation announced the initial Central Valley Project (CVP) water supply allocation for contractors. Shasta Reservoir, which represents the majority of CVP storage, is below the historic average for this time of the year, and runoff forecasts predict that overall storage might be limited if typical spring precipitation does not materialize.

Report Your Drought Impacts

Drought and Climate Outlook

ENSO

NOAA’s ENSO alert system status is currently a La Niña advisory with moderate La Niña conditions over the equatorial Pacific. There is a ~60% chance of a transition from La Niña to ENSO-neutral during the Northern Hemisphere spring 2021 (April-June). Historically, southern and central California and southern Nevada remain at increased risk for dryness into spring during La Niña conditions. For more information, please check out the NOAA ENSO blog and the Western Regional Climate Center handout about the La Niña impacts for the west.

February - April La Niña Precipitation: Increased Risk of Wet or Dry Extremes

A map of the United States shows the composite precipitation during La Nina by climate division for February through April. Based on history, dry extremes are expected in the southwestern US, the south central US, and the southeastern U.S. — Risk of wet or dry extremes from historical composite of February through April La Niñas from NOAA's Earth System Research Laboratories/Physical Sciences Laboratory.

Seasonal Drought Outlook

A slow decline in La Niña intensity is likely to result in ENSO-neutral conditions later this year, but for the forecast period through May 2021 it will continue to influence conditions across the nation. As a result, the U.S. seasonal drought outlook shows drought persistence over California and Nevada.

Temperature and Precipitation

According to the NOAA National Weather Service Climate Prediction Center's short-term to seasonal forecasts, odds favor a return of dry conditions with a continuing “typical” La Niña pattern and a dry southwest. A return to dryness continues to build drought impacts as February ends, climatologically one of the wettest months for the region.

Climate Prediction Center 3-month precipitation outlook, valid for March to May 2021. Odds favor below-normal precipitation across all but northern California and Nevada.

Climate Prediction Center 3-month temperature outlook, valid for March to May 2021. Odds favor above-normal temperatures across all but the northern tips of California and Nevada. — March through May 2021 precipitation outlook (*top*) and temperature outlook (*bottom*). A = chances of above-normal; EC = equal chances of above, below, normal; B = chances of below-normal. Source: NOAA Climate Prediction Center. How do I interpret these graphics?

Drought Early Warning Resources

California Nevada California-Nevada DEWS

Prepared By

Amanda Sheffield
NOAA/NIDIS California-Nevada DEWS Regional Drought Information Coordinator
Email: amanda.sheffield@noaa.gov

Julie Kalansky
Program Manager, California-Nevada Applications Program (NOAA RISA team)
Email: jkalansky@ucsd.edu

Special Thanks

This Drought Status Update is issued in partnership between the National Oceanic and Atmospheric Administration (NOAA) and the California-Nevada Applications Program, a NOAA RISA team, to communicate the current state of drought conditions in California-Nevada based on recent conditions and the upcoming forecast. NIDIS and its partners will issue future drought updates as conditions evolve.

Register here for the next California-Nevada Drought & Climate Outlook webinar on March 22, 2021 at 11 am PDT.