NASA Data Feeds River Forecasts as Snow Drought Effects Linger

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This map, derived from NASA’s GEOS (Goddard Earth Observing System), shows an atmospheric river reaching Washington state in December 2025, during a winter marked by extreme rainfall and too little mountain snow.NASA’s Scientific Visualization Studio

As the effects of the 2026 snow drought in the western United States carry into summer, NASA Earth data is feeding machine-learning forecasts that inform decisions about water, power, and public safety in Washington state.  

Tacoma Power, a Washington public utility, is using a U.S. technology company’s river-flow forecasts during a year of water extremes on the Cowlitz River. The utility’s largest hydroelectric project uses water stored behind Mayfield and Mossyrock dams to generate enough electricity to serve more than 151,000 homes each year.

Upstream Tech’s HydroForecast combines weather forecasts and river measurements with NASA-produced satellite data on snow cover and vegetation conditions to predict river flow from hours to days ahead. Updated every two hours, the forecasts are used by reservoir managers, hydropower producers, water utilities, and government agencies to prepare for storms, plan reservoir water releases, and navigate dry periods.

“Part of NASA’s mission is to make the view from space useful on the ground,” said Erin Urquhart, manager for NASA’s Water Resources program at the agency’s headquarters in Washington, D.C. “When an American company incorporates NASA’s freely available data into forecasts that help water managers prepare for floods, generate power, and steward water supplies, that’s NASA delivering practical value to the nation.”

Year of water extremes

During the winter of 2025-26, unusual warmth meant a larger share of precipitation fell as rain instead of snow across much of the West, while below-normal precipitation deepened deficits in some areas. January, February, and March each had the lowest Western snow cover for that month in the NASA MODIS (Moderate Resolution Imaging Spectroradiometer) satellite record since 2001.

On the Cowlitz, those conditions produced a season of extremes. In December 2025, a powerful atmospheric river brought a long, narrow band of Pacific moisture into the region, causing one of the largest one-day inflow surges ever recorded at Tacoma Power’s hydroelectric project. Across the season, that rain-heavy pattern sent water downstream quickly instead of building mountain snowpack that would melt and release water steadily into summer. Snowpack remained at just 20% to 50% of normal levels.

As winter became spring, the rain tapered off, and on April 8, Washington state placed every watershed, including the Cowlitz, under a drought emergency. From April through June, peak daily inflow into the project was among the lowest on record, leaving Tacoma Power with less incoming water to replenish its reservoirs ahead of summer demand, said Saul Villarreal, Tacoma Power’s senior hydro operations manager.

Tacoma Power’s Mayfield Dam and powerhouse sit on the Cowlitz River in southwest Washington, where forecasts using NASA data support reservoir operations and hydropower generation.Tacoma Power, used with permission

Turning satellite data into river forecasts

NASA turns observations collected by the VIIRS (Visible Infrared Imaging Radiometer Suite) instrument on the Suomi-NPP (Suomi National Polar-orbiting Partnership) satellite into data products that provide information about snow cover and vegetation greenness across entire watersheds, including where ground monitors are sparse.

To train HydroForecast, Upstream Tech collects and archives years of those NASA products alongside weather forecast data and actual river-flow measurements. Using records from hundreds of watersheds, the models learn common patterns in how water moves through the landscape and apply them in new locations.

Tests across multiple basins found that including snow and vegetation observations increased forecast skill, said Dr. Laura Read, director of technical and federal partnerships for HydroForecast at Upstream Tech. “NASA’s data gives us the reliability, global coverage, and consistency we need,” said Read. “Our short-term models run every two hours, so those inputs have to show up when we need them. Though we have stopgaps in place, any interruption to our operational pipeline is a huge deal.”

Tacoma Power uses HydroForecast alongside stream gauges, snow stations, and operator judgment. During the December storm, the NASA-informed, short-term forecast helped the utility anticipate how much water would reach the project and prepare for dynamic river conditions, while meeting operating requirements and keeping public s