Dry and warm weather will continue until Friday. Widespread rain, high elevation snow, breezy winds, and cooler weather return as we move into the weekend with the arrival of our next impactful weather system.
Discussion
The strong ridge from earlier this week has broken down and shifted east allowing occasional bands of high clouds to move across the region. Currently skies are mostly clear with temperatures mainly in the 30s and 40s over the mountains, and upper 40s and 50s across the Central Valley. Onshore surface pressure gradient has picked up a little compared to 24 hours ago and southerly winds of 5-10 mph prevail through the Sacramento Valley with a few gusts of 20-25 mph over the mountains.
Enough ridging remains overhead for another day of dry weather and mild temperatures. Highs today will be mostly in the lower to mid 70s across the Central Valley with 50s and 60s over the mountains.
The upstreamclosed low off the coast of the PacNW is forecast to drift closer to NorCal on Friday before moving in over the weekend. Precipitation is forecast to begin over the Coast Range and Shasta County by late Friday morning, then spread southeast with a cold front reaching the I-80 corridor from the Sacramento area up into the northern Sierra by Friday evening.
Showery and cooler weather is expected Saturday, then shower chances mostly retreat to the mountains on Sunday. Minor to moderate impacts are expected as the system moves through bringing rain, mountain snow, gusty wind and thunderstorm chances.
QPF of 0.50″ to 1″ is forecast through the valley with 1.50″ to 3″ over the foothills and mountains.
Snowfall accumulations of 8-18 inches are expected above 6k ft with lighter accumulations down to around 4k ft. Amounts up to 3 ft will be possible over the higher peaks.
Heaviest snow is expected Friday night and Saturday resulting in travel delays over the higher northern Sierra passes.
A few thunderstorms will be possible with the front as it moves through Friday afternoon and evening, but a better chance of thunderstorms is expected Saturday afternoon as the upper trough moves overhead.
Brief heavy rain and small hail may accompany stronger cells. Southerly breezes of 25-35 mph will be possible in the Sacramento Valley Friday afternoon and evening, and again Saturday afternoon. Southwesterly gusts of 30-50 mph will be possible over exposed ridges in the mountains.
Extended Discussion (Monday through Thursday)
Upper ridging flattens Monday as short wave trough drops into the CWA from the NW. Wave brings a threat of showers over the northern and eastern foothills/mountains. Ridging amplifies Tuesday in wake of exiting wave.
Deeper/stronger system progged to follow Wednesday into Thursday bringing more widespread light to moderate rain, mountain snow, and gusty wind.