Cold weather system moves in Saturday with widespread light Valley rain, heavy mountain snow, and hazardous travel impacts. Drier weather returns Sunday and Monday, then unsettled weather conditions mid-week.

Impacts from Saturday snow storm

Discussion

One last day of mild weather is expected today as northwesterly flow continues over Northern California. A weak shortwave makes a glancing blow over the Sierra but no significant precipitation is expected outside of light sprinkles here and there.

Breezy north to west winds do increase through the morning with the strongest winds developing late morning and early afternoon before dying down in the evening. These winds will be marginal with only 15 to 25 MPH gusts along and west of I-5 and up to 30 MPH along the Sierra.

The next round of impactful weather begins Saturday through Sunday morning with a cold system moving in from the Gulf of Alaska that will bring moderate to heavy mountain snowfall, gusty mountain winds, and light rainfall in the Valley.

Showers will return Saturday with the heaviest precipitation over the mountains and foothills.

The weather system moves in from the northwest and spreads southward across the forecast area early Saturday morning and will continue through the duration of the day.

Valley impacts will be minimal with NBM probabilities only showing a 10-20% of seeing greater than 0.50″ of rain, outside of 30-55% chance for the broader Redding area. However, hazardous travel is expected with heavy mountain snow expected.

Another cold storm system will bring potentially heavy snow and hazardous mountain driving conditions this weekend.

Snow levels of 2500 to 3500 feet Saturday morning, lowering to 2000 to 3000 feet Saturday late afternoon and as low as 1500 feet Sunday morning.

Total snow accumulations of 1 to 2 feet are forecasted with snow rates as high as 2 inches a hour possible. As a result, a winter storm warning has been issued for Western Plumas County/Lassen Park and West Slope Northern Sierra Nevada Counties including Interstate 80 over Donner Pass, Highway 50 over Echo Summit and Highway 88 over Carson Pass from 4 AM Saturday through 6 AM Sunday.

Winter Storm Warning for Saturday through Sunday morning at elevations above 3000 ft over the Sierra and a Winter Weather Advisory for portions of Shasta County for elevations greater than 2,500 feet. Hazardous driving conditions are expected.

Heavy snow in combination with gusty winds as high as 55 MPH could make travel difficult to impossible with travel delays, chain controls, snow covered roads and poor visibility with near white conditions at times. If you must travel, keep an extra flashlight, food, and water in your vehicle in case of an emergency.

Storm totals

Snowfall will begin to taper off Saturday night with lingering showers into Sunday morning. Probabilities remain relatively unchanged, still exhibiting a 45-90% of snow totals greater than 12 inches and 30-60% of 18 inches or more of areas along and south of I-80, including Highway. 50. Moderate to heavy snowfall chances do extend as for north as Highway 49 but the highest totals will be from I-80 southward.

Winter travel - best advice: Don't drive up the mountain

Today's models runs should help increase confidence with more detailed timing but currently, the highest snow rates are forecasted to be between the 10 AM to 4 PM time frame with 2 inches a hour still a possibility given the cold nature of the weather system.

Additionally, a Winter Weather Advisory has been issued for the Shasta Lake Area and Northern Shasta County for elevations greater than 2500 feet, including parts of I-5 from 4 AM to 10 PM Saturday with total snow accumulations of 2 to 9 inches. Similarly, heaviest snowfall is expected Saturday afternoon and will taper off late Saturday night.

Probabilities for greater than 6 inches of accumulations are 15-65% chance, increasing as you move northward across Shasta County. Overall conditions will improve by late Sunday morning as the trough continues to slide eastward with ridging overtaking Northern California into the beginning of next week.

Forecast pattern remains unsettled with another system looking to impact the area midweek.

Extended Discussion (Tuesday through Friday)

Ensembles and clusters indicate an active weather pattern next week, as several cold weather systems drop south from western Canada into NorCal. This will bring periods of light to moderate snow for the mountains Tuesday through Friday with the heaviest period likely Wednesday.

Mountain travel may be difficult through much of the week with Thursday being the best travel day in the current forecast.

Cold Weather safety, protect people, pets, plants and pipes!

Rainfall amounts in the Valley should remain rather light, as the northwest flow pattern will mean much of the Valley will remain rain shadowed. Cold temperatures can also be expected for the Valley with highs in the upper 40's to low 50's and lows in the 30's.