Bob Henson ·

Above: Frank Gehrke (California Department of Water Resources) crosses a snow-covered meadow as he conducts the second snow survey of the season Thursday, Feb. 1, 2018, near Echo Summit, Calif. Accompanying Gehrke are Michelle Mead, left, and Courtney Obergfell, both of the National Weather Service. Image credit: AP Photo/Rich Pedroncelli.

As day after sunny day goes by, Californians are having uncomfortable flashbacks to a drought that seemed to be well in the past. One of the driest five-year periods in California history (2011-16) was promptly followed by one of the wettest (2016-17). Many reservoirs are still flush from the hydrologic bounty of last winter, but they could be hurting again later this year. The state is wrapping up one of its driest October-to-January periods on record, and there’s little hope of moisture through at least mid-February.

The situation was brought home Thursday as the California Department of Water Resources carried out its monthly high-profile check on snowpack at the benchmark Phillips Station in the central Sierra Nevada. The survey found snowpack at just 14 percent of the historical average, or just 13.6”.

The five weather stations that make up the Central Sierra precipitation index ended January at their third-driest wet season on record. “No seasons that have been this dry or drier have ended the full season with at least normal rainfall,” reported Jan Null (Golden Gate Weather Services). The same holds true for the Northern Sierra (29th driest) and Southern Central Sierra (31st driest), according to Null. He stresses that there’s still time to recover from this dismal start to the water year if rains kick in soon. Moreover, the water stored in California’s reservoirs last year will go a long way toward blunting drought-related water scarcity.

Even so, the outlook for the first half of February is harrowing. Both the European and GFS models insist on steering Pacific storms to the north of California, which would leave most of the state bone-dry for at least the next 10 days.

Figure 1. U.S. Drought Monitor released on Thursday, February 1, 2018. Image credit: National Drought Mitigation Center.

Figure 2. Water held in snowpack (snow water equivalent) as a percentage of the long-term average (1981-2010) as of Jan. 31, 2018. Image credit: USDA/NCRS and National Water and Climate Center.

In the weekly U.S. Drought Monitor valid January 30 and released on Thursday, more than two-thirds (67.10%) of the contiguous U.S. was abnormally dry—the largest fraction in five years. The area covered by severe to exceptional drought more than doubled in January alone. “Mountain snowpack was abysmally low, reaching record low levels for this time of year in parts of New Mexico and Colorado,” the report said.

Unusually warm conditions across the West are making things worse by hastening snowmelt and evaporation. Record highs were set three days in a row this week (Sunday through Tuesday, Jan. 28-30) at the University of California, Los Angeles, where records go back to 1933.

La Niña winters (such as the one we’re in now) tend to produce wetter-than-usual conditions across the Northwest U.S., with increasing odds of dryness as you head south. This year, the classic La Niña moisture pattern is roughly holding, except that very strong upper-level ridging across the North Pacific into western North America has shunted moisture further north than usual across the U.S. West—a worrisome echo of the northward displacement of moisture away from the Southwest during El Niño in 2015-16.

As reported by InsideClimate News, several recent studies have shown how rising temperatures are pushing snowfall toward higher altitudes across the U.S. West; for example, one study found that on the western flank of the Sierra, the snowpack shrinks by 10 percent for every 1 degree Celsius of warming. “Long-term climate warming is strongly correlated with declining snow water equivalent,” notes the Climate Signals website.



Figure 3. Percentage of average precipitation for January 2018 through 12Z (7 am EST) Wed., Jan 31. Image credit: NOAA/NWS Advanced Hydrologic Prediction Service.

At weather.com, Jon Erdman takes a detailed look at the situation in California. Here are a few glimpses at how dry conditions are affecting U.S. states beyond California.

Texas

Moderate to severe drought now covers more than 40 percent of Texas, compared to just 4 percent right after Hurricane Harvey struck. In the Texas Panhandle, Amarillo finished an unprecedented third calendar month in a row without any measurable precipitation at all. The last time Amarillo saw more than a trace of rain or snow was on October 13. The city’s current dry streak—110 days as of Jan. 31—is more than a month longer than anything observed even in the infamous Dust Bowl of the 1930s. The previous record of 75 days occurred in 1957.

The ground is “so dry it’s like concrete,” C.E. Williams, general manager of the Panhandle Groundwater Conservation District, told the Texas Tribune. No rain or snow is in sight for Amarillo through at least the first week of February.

New Mexico

Albuquerque is in the midst of its driest water year (Oct. 1-present) in records going all the way back to 1892. The city has picked up just 0.07” of moisture, compared to the previous record of 0.20” from 1904. “It seems like ‘driest start to a water year in more than a century of records’ reaches beyond journalistic cherry-picking to a really substantive ‘wow’,” said John Fleck, a longtime water journalist who now directs the Water Resources Program at the University of New Mexico.

Much like California, the water supply in New Mexico is in decent shape for now, according to Fleck, thanks to reservoir storage from a relatively wet 2017 as well as the presence of an aquifer below Albuquerque. “The humans will do fine even in an extreme year like this. But we're very worried about fire season,” he said. “There’s a lot of fine fuel build-up because last year was wet, and the forests right now are so dry.” A large fraction of the state’s piñon pine (the official tree of New Mexico) were lost to drought and bark beetles in the early 2000s. Millions more piñon pine died under similar circumstances in 2013.

Figure 4. Precipitation in Albuquerque, NM, for the period Oct. 1 through Jan. 30, going back to 1895. This winter’s value of 0.07” is the least on record. Image credit: NOAA Regional Climate Centers.

Arizona

The region’s two massive reservoirs along the Colorado River, Lake Mead and Lake Powell, got a boost from the wet winter of 2016–17, but inflows to the lakes from the Southern Rockies could be far less this spring and summer. The amount of water held in snowpack across the Upper Colorado River basin, which sends water into the two lakes, is less than half of what it was at this point in 2017 (see Figure 5 below). Water levels at Lake Mead have dropped more than 140 feet since 2000, with only fitful recoveries during wet periods.

Here's a precipitation update to our abnormally dry September to January time frame. As you can see even with a couple storms under our belt not much has changed. Dry weather looks to continue. #azwx pic.twitter.com/ImoZ6CGLON — NWS Flagstaff (@NWSFlagstaff) January 27, 2018

Figure 5. The amount of water in snowpack across the Upper Colorado River Basin as of Jan. 28, 2018, was less than half the amount at this point in 2017 and about 65% of the long-term (30-year) average. Image credit: U.S. Bureau of Reclamation.

Oregon

The lack of mountain snow across California extends north into the Oregon Cascades, where snow water equivalents were running only around 50 percent of average as of January 19. The state’s mountains got some respectable autumn storms—Oregon precipitation was near average for October through December—but it was much warmer than average at higher elevations in December, even as lower-elevation readings were below average, said the Office of the Oregon State Climatologist in its December climate summary. "This sort of temperature anomaly pattern is a bit unusual to see on the monthly time scale," the report said.



