Showers and mountain snow today, lingering into Wednesday, Widespread freezing low temperatures Wednesday through Friday. Temperatures trend warmer by this weekend. Another round of unsettled weather possible early next week.
Winter Weather Advisory until 10 PM PST this evening for Motherlode-Northeast Foothills/Sacramento Valley-Western Plumas County/Lassen Park.
Winter Storm Warning until 10 PM PST this evening for West Slope Northern Sierra Nevada.
Freeze Warning from 2 AM Wednesday to 9 AM PST Friday for Carquinez Strait and Delta-Central Sacramento Valley-Motherlode- Northeast Foothills/Sacramento Valley-Northern Sacramento Valley- Northern San Joaquin Valley-Southern Sacramento Valley.
Discussion
3:00 am radar indicates snow showers continuing over the Sierra Nevada at this time. We have also received a few reports of light precip reaching some lower elevations. Temperatures are generally 10 degrees cooler than this time yesterday, in the 30s to 40s across the valley and teens and 20s over the mountains.
Some areas are also seeing breezy winds with gusts around 20 to 30 mph along the Western edge of the Sacramento Valley, Delta and over the high Sierra. Locally higher gusts have also been reported over the Sierra Crest reaching in excess of 100 mph in the late night and early morning hours. HRRR and NAM high resolution model guidance indicate more widespread chances for snow and rain showers developing this afternoon across Northern California with best chances over the higher terrain.
With the cold airmass in place, snow levels will be low enough that if showers develop in the foothills some of that precip may fall in the form of snow. Elevations above around 2,000 to 3,000 feet could see a few inches of snow.
NBM WSUP viewer has about a 70% chance for the Motherlode town of Twain Harte at an elevation of around 3,500 feet to see at least 2 inches of snow by Wednesday morning and about a 90% chance for Arnold at an elevation of around 4,000 ft.
There is also some indication for the potential for showers to have some convection associated with them. Best chances for showers with more of a convective nature will likely be just outside our forecast region, in the bay area and southward in the Central Valley. Although SPC has included the Sacramento Metro region and northern San Joaquin and Delta in their convective outlook.
Cold air left in the wake of the departing system midweek will lead to subfreezing temperatures in the early morning hours Wednesday through Friday. Some locations could dip into the mid 20s in the Valley, particularly on Thursday when the coldest temperatures are anticipated. Lows may also approach daily record minimums.
Extended Discussion (Saturday through Tuesday)
Upper level ridging builds over NorCal Saturday bringing a warming trend along with dry weather. The ridge will shift east on Sunday allowing a short wave trough to approach. Ensembles are in disagreement with the strength of this wave and right now it looks like light precipitation will be possible mainly over the northern mountains. Upper level ridging builds back in on Monday with precipitation chances retreating northward.