Mountain snow and significantly cooler temperatures this weekend into early next week

September 28, 2019 – Much cooler weather along with a chance of showers and high elevation snow over the weekend into early next week. Below normal temperatures continue through next week.

Discussion

Low stratus continues to build into the Sacramento vicinity with ceilings generally around 1kt. A weak wave ahead of the main upper low has allowed showers to develop mainly over Shasta county early this morning, with additional low ceilings seen in the vicinity foothill and mountain regions.

Showers and a few storms will continue today mainly in the southern Cascade/northern Sierra mountains and foothills. HREF probabilities (and model soundings) indicate the possible best chances for isolated thunderstorms this afternoon may be just north of I-80, with the main impact with any storm being small accumulating hail.

Snow levels will begin to drop this afternoon with levels just below 6000 feet expected by this evening. Travelers should expect snow at pass levels which may lead to difficult driving conditions.

The upper low stalls out over the PacNW before lifting out of the area early Tuesday. Continued precipitation will be seen through this period with rain amounts generally between 0.25-0.50 inches in the foothills, and locally up to an inch over the high terrain. A few showers may be seen in the Valley which may bring a few hundredths of an inch of rainfall. Snow showers will also continue through Monday with amounts around 2 to 6 inches at pass levels, and locally up to a foot possible at the highest peaks. The Winter Weather Advisory begins this afternoon and continues through Monday.

Temperatures will continue to fall each day through Monday, with Valley highs on Monday topping out in the upper 60s, and mountain temperatures in the 40s. Overnight lows in the mountains may reach below freezing each night through Tuesday as this system moves across the area. Valley lows will be in the 40s.

Extended Discussion (Wednesday through Saturday)

Extended period starts out Wednesday under high pressure with dry and warmer conditions although daytime highs will remain below normal for this time of year. Models show a northern Pacific trough moving through the Pacific northwest around Thursday. This system will bring a slight threat of showers to the northern mountains in the afternoon and evening hours but otherwise have very little effect. Friday will see a little cooling as cooler air filters into the region with a little warming on Saturday as high pressure slides across the north state. Even with this warming, daytime highs are forecast to remain several degrees below normal through the extended period.