A pair of back-to-back storms were forecast to dump heavy snow and rain over parts of the Pacific Northwest, northern California and the Rockies this week, triggering winter storm and flood warnings.
The storms pushing off the Pacific are the result of an atmospheric river , a corridor of air heavy with moisture that forms when warmer air from the tropics moves toward the poles.
As the first of the two storms pushes inland on Monday, it will bring heavy coastal rain and snow to the highlands across the Pacific Northwest and northern California, according to the National Weather Service . By the evening and into Tuesday, the wintry mix is expected to spread across the northern Rockies and Great Basin, bringing as much as 8 to 12 inches of snow to the Cascades.
The next storm is expected to approach the Pacific Northwest Tuesday night, unleashing showers and thunderstorms along the coast and portions of the Coastal Ranges that have the potential to trigger flooding. As the storm moves east, it could bring more snow to the Cascades.