The storm that most likely will form the base of this season’s snowpack in the San Juan Mountains will move into the region Tuesday and is expected to linger throughout the Four Corners into Friday.

Chris Cuoco, meteorologist with the National Weather Service in Grand Junction, said the pattern’s movement is complex: One low pressure system from the Pacific Northwest and one from off the coast of Baja California will merge.

“The first wave of the storm should hit Southwest Colorado late Tuesday and early Wednesday. It will be mostly rain in Cortez, Durango and Pagosa Springs. You won’t see snow until you climb into the hills above 8,500 feet. The U.S. 160 corridor will mostly see rain,” he said.

Cuoco said above 9,000 feet, the storm is expected to drop 3 to 8 inches of snow with accumulations increasing with the elevation.

“It starts Tuesday late, and early Wednesday with a few breaks, and then Thursday the low pressure system will be over the area. Cold air finally comes in Thursday night and Friday morning,” he said.

River valleys could see a rain-snow mix with little to no accumulation early Wednesday. Periods of rain in lower elevations with snow in the San Juans and other ranges in the Four Corners are expected Wednesday.

Late Thursday and early Friday, lower elevations along the U.S. Highway 160 can expect some snow accumulations, Cuoco said.

The week will see a gradual cooling trend. In Cortez, Tuesday’s high is expected to be 61 but is expected to drop to 46 on Friday. Tuesday night’s low is expected to drop to 17 Friday night.

The weather is expected to clear up Friday.

The next chance for a storm with precipitation moving into the region looks like it will be Nov. 25, Cuoco said, but he expects the storm will have moved out of the area by Thanksgiving Day, Nov. 28.

For November, the Climate Prediction Center is calling for the month to be warmer than normal with lower-than-normal precipitation.

parmijo@durangherald.com