California-Nevada and Pacific Northwest Special Edition Drought Early Warning Update

Current Conditions

Over the past 6 weeks a high pressure ridge near the western U.S. coast has largely diverted precipitation away from the states of California, Nevada, Oregon, Washington, and Idaho. Well above-normal snow water equivalent (SWE) at the start of 2022 has provided the buffer needed to mitigate the extreme dry spell over the past month and avoid drought degradation, including snow drought. But without additional precipitation, SWE and the chances of recharge to the reservoir systems will continue to drop. 

Pacific Northwest

• While the Cascade Range in central and northern Oregon and Washington has received near-normal winter precipitation, many other areas in Oregon and central Washington have not. This is especially notable in areas east of the Cascades and in southern Oregon that have received 50%–70% of normal water year to date (WYTD) precipitation and continue to experience severe to exceptional (D2–D4) drought. This area includes seven Oregon counties and one Washington county which experienced their lowest total precipitation over the last two water years combined on record. Reservoir levels in these areas are already extremely low, and lower than they were at this time in 2021. Streamflows are well below normal despite some recent melting of the little snow that has fallen during this water year. 
• Watersheds across Idaho are currently reporting 91%–102% of normal SWE (based on the 1991–2020 median). But with little snow in the forecast and poor reservoir carryover from last year, recharge could be affected, especially in southern Idaho. 
• In Washington State, some watersheds, including the Olympia Mountains and portions of the eastern slope of the Cascades (e.g., Yakima and Okanogan) will reach April 1 with below-normal snowpack even if accumulation resumes at the normal pace (50th percentile) or even exceeds the normal pace (70th percentile). The current median forecasted runoff for rivers monitored by the Northwest River Forecast Center is now below 88% of normal.
• The NOAA Drought Termination tool indicates that the areas of central Washington and Oregon currently in extreme (D3) and exceptional drought (D4) would require more than 200% of normal rainfall to fully recover within the next three months. The probability of this occurring in Oregon, based on the historical record, is less than 1%.
• Excessive evaporative demand throughout much of the Pacific Northwest has also contributed significantly to drought severity.

California-Nevada

• December through February are California and Nevada’s wettest months, and the extended dryness over the past 4–6 weeks has resulted in California’s statewide SWE now being quite similar to SWE at this time last year. SWE has also plateaued in most Nevada basins.
• Current California Department of Water Resources Sierra Nevada measurements indicate that SWE is 71% of normal for this date and 55% of April 1 normals. Most of California’s major water supply reservoirs remain below historical average. 
• The combined volume of water stored in reservoirs and snowpack has plateaued in all parts of the Sierra Nevada, and seasonal snowpack has begun to decline. This situation will reduce the amount of water expected to be available later in the spring and summer. 
• Runoff to date has been bolstered by October and December’s abundant precipitation, but runoff is beginning to decline as conditions remain dry. Soil moisture deficits have also grown, and some areas are seeing early greenup. 
• Recent warm temperatures, including a heat wave in southern California, have exacerbated drought conditions and fuel dryness and contributed to recent wildfires.
• Between January 1 and February 1, the odds of reaching normal water year precipitation, based on historical water year totals, dropped drastically in northwestern California and southern California-Nevada. If no precipitation falls in February, these regions’ odds decrease to less than 10% and expand in area, leaving only the eastern Sierra and parts of western and northern Nevada with a chance of reaching historical normal precipitation. 
• A recent ‘slider’ system brought some snowfall to the Sierra crest (2–5 inches), Tahoe Basin (1–3 inches), and Carson Range (5–9 inches). This same system brought 0.1–0.5 inches of precipitation to much of southern California. 
• Read the latest California Drought Update here and Nevada Drought Update here. 
• A megadrought has enveloped southwestern North America for the past 22 years. Evidence suggests that this period is the region’s driest megadrought—defined as a drought lasting two decades or longer—since at least the year 800, according to a new UCLA-led study. 
  • A dry water year 2022 will likely result in the third 3+ year drought in the last 15 years (2007–2009, 2012–2016, and 2020 to present). 
  • The evaporative demand, the atmospheric drying of the landscape, contributes to making the current megadrought more extreme than other droughts in the record. 

Percent of Normal Precipitation: Water Year & Last 30 Days

SNOTEL Snow Water Equivalent (SWE)

0–100 cm Soil Moisture Percentile

Odds of Reaching Water Year Normal Precipitation

12-Month Evaporative Demand Drought Index (EDDI)

Drought and Climate Outlook

• The National Weather Service Climate Prediction Center's (CPC) short-term forecasts through the remainder of February into March extend below-normal precipitation along the West Coast. Compared to typical La Niña patterns, the odds of below-normal precipitation from central California to Washington are higher. 
• The Center for Western Weather and Water Extremes (CW3E) subseasonal to seasonal outlook (updated February 23) indicates varying confidence that a high pressure ridge will remain in the coming weeks. Models generally agree on below-normal West Coast atmospheric river activity in early March. 
• CPC seasonal forecasts (March through May) continue to reflect canonical La Niña patterns as La Niña is forecasted to continue through spring, with below-normal precipitation in southern California-Nevada and above-normal precipitation in the northern Pacific Northwest. 
• Given this information, the seasonal drought outlook forecasts drought persisting in California, Nevada, most of Oregon, and Idaho, with drought improvement and/or removal in Washington. 

6–10 Day Temperature and Precipitation Outlooks

8–14 Day Temperature and Precipitation Outlooks

Seasonal Drought Outlook: February 17–May 31, 2022

What Drought Impacts Are Likely If Below-Normal Precipitation Continues?

• Continued dryness will likely lead to drought development and intensification across the region.
• Impacts have continued through winter in these regions. A Condition Monitoring Observer Report on Drought from Coos County, Oregon noted, “It has been dry here the last three years but this year it is much drier. All of the ponds are dry or close to it…where we run some cows there is no water where even the last couple years water showed up by this time. Our spring that feeds the cistern on our home…didn't get high enough to fill the cistern until mid December. It is still going but I think it shows how depleted the groundwater was from the last two years.”
• Many areas have low odds (based on the historical record) of reaching normal precipitation this water year, and combined with the past 1–2 years of drought, the odds of reaching a two-year normal are less than 5%–10% for much of California, Nevada, Oregon, Washington, and Idaho. For example in California, if no more precipitation falls this water year (currently 9 inches needed through September 30, 2022 to reach normal), 2020–2022 would be the driest three-year period on record, followed by 2013–2015.
• Drought intensification or development on top of a multi-year drought hampers water supply replenishment and perpetuates dry soils and vegetation, all of which continue to stress water storage and water supply management. As a result, the need for water use conservation is increasing, agricultural (including rangeland) planning is becoming more challenging, and the wildfire season may begin earlier.
• At this point, additional precipitation and snow can potentially help offset drought development and impacts. However, the chances of achieving widespread and substantial precipitation through the remainder of February and beyond into March are modest. These trends suggest that drought mitigation actions should continue, especially given the long-term drought.

Drought Early Warning Resources

Washington

Oregon

Idaho

Pacific Northwest DEWS

California

Nevada

California-Nevada DEWS

Prepared By

Amanda Sheffield
California-Nevada DEWS Regional Drought Information Coordinator, NOAA/NIDIS, CIRES

Britt Parker
Pacific Northwest DEWS Regional Drought Information Coordinator, NOAA/NIDIS, CIRES

Adam Lang
Communications Coordinator, NOAA/NIDIS, CIRES

David Hoekema
Idaho Department of Water Resources

David Simeral
Western Regional Climate Center, Desert Research Institute

Erica Fleishman
Oregon Climate Change Research Institute (OSU)

Holly Prendeville
USDA Northwest Climate Hub

Jeff Marti
Washington Department of Ecology

John Abatzoglou
UC Merced

Julie Kalansky & Michael Dettinger
California Nevada Applications Program (CNAP), Scripps Institution of Oceanography

Larry O’Neill
Oregon State Climatologist, Oregon State University

Karin Bumbaco & Nicholas Bond
Office of the Washington State Climatologist

Michael Anderson
California State Climatologist, California Department of Water Resources

Russell Qualls
University of Idaho

Ryan Andrews
Oregon Department of Water Resources

Steph McAfee
Nevada State Climatologist, University of Nevada – Reno