More clouds on Seattle horizon?

SEATTLE – Cloudy springs, hot summers and much less snow in the mountains may be in Washington state’s future, according to a detailed computer simulation of global warming done by the University of Washington.

Previous studies of global warming in the Pacific Northwest have predicted a decline in snowpack in the Cascade Range as well as warmer temperatures. The new study adds a new wrinkle: cloud cover in March, April and May actually could increase.

“The spring is going to be gunkier if you believe this under global warming,” meteorologist Cliff Mass said.

The computer simulation relied on global climate data models, which give a planetary view to show how temperatures will rise. But the study also used a high-resolution regional model that can distinguish topographical features down to a scale of a few miles – thus allowing details about mountains and inland waters that play an important role in local weather to be included.

The surprising jump in springtime clouds apparently would be caused by warmer inland temperatures, which cause air to rise and draw in cooler, moist air from the ocean.

The model also predicts that the number of summer days when temperatures soar into the 90s would more than triple before the end of the century if greenhouse-gas emissions from cars and industry continue unabated.

Total precipitation wouldn’t change much across the region, according to the model. But the region could be facing catastrophic loss of winter snowpack and no increase in offsetting summer thunderstorms, which could result in pronounced dry spells.

The study also suggests Western Washington may not warm as rapidly or as much as the east side of the state. By 2050, average temperatures in the Puget Sound region would rise about 2 degrees, while some parts of the Columbia Basin could be as much as 5 degrees hotter. In 2090, much of the basin would be as much as 8 degrees warmer, according to the model. “This is not good for Eastern Washington farms,” Mass said.