Winter alerts have already been issued for the Sierra Nevada as a large digging trough disrupts the warm ridge that's been residing in the west. The west can expect widespread rain chances, mountain snow and cooler temperatures for the rest of the work week.

SET-UP

A digging mid to upper level trough will bring in widespread vertical lift to the western U.S. As the trough helps draw in tropical moisture, it will meet a cool low pressure system at the surface. As a cold front crashes east and south, precipitation chances will spread from border to border, into the Cascades, Rockies, and eventually across the country.

Onshore flow will begin Wednesday allowing for a few pre-frontal showers. As the cold front moves inland Wednesday night, storms will become more wide spread, especially through Oregon and northern California. Dropping overnight temperatures will ensure snowfall in the mountainous regions, that will carry into Thursday. As the front pushes south, southern California will see a good chance at rain by Thursday evening. We may even see some snow at the highest elevation peaks in SoCal. As the surface low wraps up within itself, scattered showers and mountain snow will continue across the Pacific northwest Thursday.

The first wave will move into the Rockies and Four Corners states on Friday, as another trough comes ashore. This will mean another round of precipitation from Northern California to the Canadian border, moving into the northern Rockies for the weekend.

CALIFORNIA IMPACTS

Winter alerts have already been issued for the Sierra Nevada, beginning Wednesday evening and lasting through the end of the day on Thursday. One to two feet of snow is expected at and above pass level, and 4-12" possible above 5000 feet.

NWS Reno is also highlighting the danger of the winds. Gusts will easily reach 40 mph, but could exceed 100 mph along ridge tops. With snow falling, whiteout conditions will make driving impossible.

Rainfall totals will be heaviest along the northern California coastline where the brunt of the moisture is focused from the atmospheric river. We will have to watch out for totals in southern California to reach 1-2" at lower elevations and 2-4" in the mountains and hills.

NORTHWEST IMPACTS

Coastal areas will see the highest rain totals, especially in southwest Oregon.

No winter alerts have been issued for the Cascades yet, but they will likely be needed as totals reach the 1-2 foot range.