Could winters in the Pacific Northwest become drier? New climate report offers projections

(NEXSTAR) — While a strong El Niño will likely bring more snow and precipitation to part of the U.S. this winter, and an atmospheric river has already battered our area, a new federal climate report suggests dependably snowy and wet winters may be in jeopardy.

The Fifth National Climate Assessment, released in November, shows the planet will likely heat up by an average of between 4.5 and 7.2 degrees Fahrenheit compared to pre-industrial times — outpacing goals of both the U.S. and international community, The Hill reports. The average U.S. temperature is likely to rise between 4.4 and 5.6 degrees, with northern and western parts of the country likely to experience the warming at disproportionate levels, according to the report. 

It isn’t just the temperature that has a dire outlook. Projections show precipitation is on track to take a hit, too. 

We’ve already seen some of climate change’s impacts on it. The report points to Hurricane Harvey, a Category 4 storm that hit Texas and Louisiana in 2017. Researchers say “climate change very likely…increased both precipitation and flooding” during the storm. 

In the coming years, “precipitation from extreme events is projected to increase with warming,” the report explains. But, they also note that while extreme events with greater precipitation may become more common, overall precipitation totals could still decrease. That means you may experience more events that cause flooding over a day or two, but fewer normal rainy or snowy days, where the overall accumulation is smaller. 

So what about your wet winter days and white Christmases?

According to the report, as temperatures rise due to climate change, we may see more precipitation that falls as rain than snow. Rising temperatures could also mean the snowpack sticks around for a shorter period of time, which can, of course, impact runoff for the communities like California and Nevada that rely on it. Projections show that in areas in the West where snow is the dominant source of runoff, total seasonal snow water volume could decrease by 24% by 2050. 

The climate report includes the below maps that show how the snow water equivalent across the U.S. could change between 2036 and 2065 compared to the time between 1991 and 2020. The larger map shows the average of all available projections while the maps on the right show projections with more precipitation (on top) and less precipitation (bottom). 

The largest snowpack declines are expected in the Northwest, New England, the upper Midwest, and into the South, according to the report. That’s especially true along the Cascade Mountain Range, stretching from northwest Washington south through Oregon and into California.

In those areas, the maximum annual snowpack could decrease by as much as three to five inches. Across other portions of the Pacific Northwest, the decrease could range between 0.2 and two inches. Should the wetter projections ring true, the decline in the snow water equivalent would be less sharp, with portions of the cascades still seeing the largest decrease. However, portions in the very northwest corner of Washington could actually see an increase in annual precipitation. The alternative could be seen if we experience drier years, which could cut the average precipitation by more than five inches in some parts.

Projections seen below show the Northeast, Midwest, much of the East Coast, and portions of Washington state could see the average annual precipitation increase. The Southwest, stretching from southern California to Texas, could see a decrease in the annual precipitation. Hawaii may be the hardest hit, especially on the eastern sides of its islands. 

As with the above snow map, this figure includes projections for wetter and drier outlooks. Should the U.S. experience wetter years, the Northeast and Iowa could see the largest increase in rain — as much as 5 inches, if not more — with only the northwestern corner of Oregon, a portion of northern California, and the southern tip of Florida seeing a decrease in annual precipitation. Should we experience drier years, Southern states — primarily Texas, Oklahoma, and Louisiana, as well as Nebraska and Missouri — would be especially dry. In fact, most states would see a decrease in precipitation, with the exception of Washington, Oregon, and much of New England. 

On average, most of the Pacific Northwest could see an increase in annual precipitation, albeit small. Under wetter conditions, Washington's portions of the Cascades could see annual precipitation rise by three to five inches, if not more. Meanwhile, Oregon's northwest corner could see a decrease in annual precipitation. Under drier projections, the Pacific Northwest could still experience more precipitation while much of the country would see less.

The changes in snow especially could disrupt water infrastructure and hydropower in the Southwest. Declines in water availability wouldn’t be limited to Arizona, New Mexico, Utah, Colorado, Nevada, or California either, according to Dave White, lead author of the report’s Southwest regional chapter. 

“You just need to think about the benefits that water from this region provides,” White told The Hill. “It affects your ability to have affordable and healthy foods year-round.”

The Hill’s Rachel Frazin contributed to this report.