Dry weather returns today with cold lows this morning and Friday morning. Another storm system will develop Friday afternoon and continue into early Sunday morning, bringing heavy snow and impacting mountain travel.
discussion
Dry weather returns today as the storm system exits to the southeast with a dry northwest flow and an upper level ridge. Temperatures will be cold this morning, with lows in the valley near freezing. Northerly winds of around 5 to 12 miles per hour can help keep temperatures from dropping, with the coldest temperatures occurring in areas where the wind is blocked.
Skies in the Valley and Delta will be mostly clear, but clouds will remain over the mountains into the afternoon. Low temperatures in the valley are expected to remain below freezing Friday morning as well. Winds will weaken, but increased cloud cover ahead of the next system should limit radiative cooling to some extent.
The next storm will begin to spread into Shasta County Friday morning and spread south through the afternoon and evening. Snow levels packed with cold air over Shasta County will be fairly low at 1,500 to 2,500 feet Friday, but will rise to 3,000 to 4,000 feet Saturday and 4,500 to 5,500 feet by Saturday night. . About 6 to 12 inches of snow is expected in areas above 3,000 feet, with locally higher amounts on mountain peaks and 1 to 3 inches along I-5. Winter weather warnings may be required.
Heavy snow is expected in the northern Sierra and southern Cascades from Friday afternoon into early Sunday morning, with 6 to 18 inches of snow possible along the Sierra above 4,500 feet and up to 2 feet in the higher mountains. The chance of more than 12 inches of snow across the I-80 and Highway 50 corridors has increased from Friday afternoon into Sunday morning and now ranges from 60 to 90 percent.
This system will be different from the previous one, with snowfall starting at about 3,500 feet on Friday, increasing to 4,000-5,000 feet by Saturday morning, and 5,000-6,000 feet by Saturday night.
Confidence continues to grow that travel will be affected by heavy snow, reduced visibility and winds of 40 to 50 mph in high elevation areas above the Sierra crests. As a result, a Winter Storm Warning has been issued for the West Slope of Western Pluma/Lassen Park and the Northern Sierra Nevada region from 4 p.m. Friday to 4 a.m. Sunday for heavy snow and wind gusts as high as 50 mph. .
Delays, possible chain restrictions, reduced visibility due to snow-covered roads, and possible road closures can make travel very difficult. Snow showers are expected to end by Sunday morning. Anyone planning a weekend trip to the mountains is advised to check the weather forecast and adjust their schedule accordingly.
Rain impacts will be more pronounced with a weekend system with occasional moderate rain, with precipitation totals expected in the valleys of 0.33 inches to 1.25 inches and in the foothills of 1.25 inches to 2.50 inches. Localized ponds may form along roads and low-lying areas.
Extended discussion (Monday to Thursday)
Dry weather is expected from Monday into Tuesday as a strong upper ridge of EPAC forms inland. Valley fog is possible in the morning, and high temperatures are expected to be near normal.
The model solution diverges on Wednesday, introducing prediction uncertainty. The NBM/EC will bring further precipitation to the CWA on Wednesday/Wednesday night, while the GFS will maintain an upper bulge into the middle of the week. The ensemble/cluster leans towards a drier upper ridge solution.
