News•January 25, 2013

Low Snowfall Raises Concerns About Drought Recovery

The total extent of the persistent national drought receded slightly during the past week, but in many places, conditions look no better now than they did when winter began. In particular, thin snow cover in some Western states is raising concerns that the drought’s impacts in some of the hardest-hit regions will only worsen when temperatures increase and evaporation rates rise in the spring.

Between January 15-22, the amount of land in the lower 48 states experiencing drought conditions shrank slightly, from 58.87 percent to 57.64 percent, thanks largely to precipitation that brought relief to parts of the Mid-Atlantic, Midwest and Southeast. Some of that fell in the form of snow, particularly in parts of Virginia. This marked the 31st straight week in which more than half of the continental U.S. was considered under “moderate” drought conditions or worse by the U.S. Drought Monitor.

Rainfall percentage of average during the past 180 days across the Western U.S., showing widespread below-average precipitation in most areas.
Credit: NOAA/NWS.

The drought became even more entrenched in some of the longest suffering areas, as impacts intensified slightly in Kansas, Oklahoma, and northern Texas, where thousands of square miles remain bone dry.

In the West, parts of which have seen milder-than-average temperatures and below-average snowfall since the start of the year, the low snowpack in the mountains is beginning to concern experts about whether this spring will bring enough sustained snowmelt to restore soil moisture and vegetation, and prevent a repeat of 2012’s severe wildfire season.

“The lack of snow continues to heighten concern across the West,” said Mark Svoboda of the National Drought Mitigation Center, in a news release accompanying the Drought Monitor. “While there is plenty of time to make up ground, last year’s low snowpack across the central and southern Rockies, in particular, has several interests watching closely to see if a strong finish to winter can bring about more promising streamflow forecasts for the dry season come summer,” he said.

A series of storms are forecast to roll into the Pacific Northwest in the coming week, but it’s unclear how much beneficial snow they will bring to the driest areas.

Mountain snowpack as of January 1, showing below-average snowpack in the Intermountain West and the eastern Rockies.
Credit: USDA/NRSC.

Currently, the snow cover in Colorado is sparser, and thinner than it is in an average year. Parts of the Rocky Mountains have less than half of the snow cover than they usually do at this time of year. The snow-water-equivalent in parts of the state, a measurement of how much water would be released if the snow melted, is estimated to be as low as 3.7 inches, where the median amount is 9.6 inches. The statewide average snow-water-equivalent is less than 60 percent of normal, as estimated by the SNOTEL network from the National Resources Conservation Service.

“In terms of our normal snow accumulation season, we are way behind the average,” said Nolan Doesken, a Colorado State climatologist in an interview. “We’re just a little past the midpoint of our normal snow accumulation season and there is a substantial and sufficient shortfall of snow. It would take about 150 percent of the average snow, or more, for the remainder of the winter to catch up.”

“The chances of that occurring based on the past 30 to 35 years are about 1-in-10, at best,” he said.

In a normal year, winter snow in the Rocky Mountains takes weeks to melt in the spring, and replenishes reservoirs that last the rest of the year. When that snowmelt is coupled with heavy rains in March and April, it produces an abundance of soil moisture and growth of vegetation. Part of what makes this current drought so severe was an unusual heat wave in March of 2012 that prevented that replenishing process from happening. The early warmth melted an already thin snow cover, allowed vegetation to grow too rapidly early on, and that extra demand for water helped leave the water table dry going into the summer, which is normally the time when water is scarcest.

The hot, dry weather and abundant vegetation helped set the stage for the Waldo Canyon fire, which was the largest wildfire in Colorado state history, and destroyed hundreds of homes in Colorado Springs.

Manmade global warming combined with changes in land-use practices have caused large wildfires in the West to more than double in the last few decades. Climate Central research found that in Colorado, wildfires more than 1,000 acres in size have more than quadrupled since the 1970s.

Across the West and Plains states, the drought outlook for the coming months looks grim. Last week, the National Oceanic and Atmospheric Administration released a seasonal drought outlook that forecasted the drought to persist or intensify across the West, including in Colorado.

In parts of southern Colorado, northern Texas, and Oklahoma, which have been engulfed in drought since 2011, Doesken is hoping for at least an average amount of rain, just to get them through the year.

“Anything resembling the middle of the distribution will feel wet. It won’t restore reservoirs, and it won’t restore soil moisture, but it will buy us some time and it will raise our spirits,” Doesken said, “We need a wet spring.”

Climate Central's Andrew Freedman (@afreedma) contributed to this report.