The next in a series of storms will move in today bringing Valley rain and significant mountain travel impacts that will continue through the weekend. Heavy rain and thunderstorms may bring renewed flooding Saturday. Additional storms expected early next week.
Discussion
Clouds, and perhaps a few sprinkles, are spreading back across the region early this morning while radar shows more substantial precipitation beginning to move onshore over northwest California. The clouds along with a light southerly breeze are keeping temperatures rather mild early this morning with current temperatures only in the upper 50s to around 60 in Sacramento. Elsewhere, readings are in the 30s and 40s in the mountains with mainly 50s across the lower elevations. The amplified trough off the coast is finally beginning to lift out as the upstream kicker (Saturday’s system) nears 40N/145W.
A line of showers with perhaps some embedded thunder will move in with the front this morning, reaching much of the valley by mid- late morning and over the northern Sierra by early afternoon. It’ll be a pretty sudden shift back to the wet and unsettled weather after yesterday’s brief break with travel conditions likely to deteriorate quickly over the northern Sierra during the afternoon.
Precipitation will turn more showery over the valley in the afternoon behind the front with a few thunderstorms possible into the early evening. Snow will continue overnight tonight over the mountains while the valley will see a bit of break as we’ll be in-between systems.
It’s still looking like Saturday’s storm will likely be the most impactful with heavier precipitation, strong winds and thunderstorms. Increasing warm-advection and strong lift ahead of the approaching storm will result in widespread moderate rain ahead of the front on Saturday morning into the afternoon.
Gusty southerly winds will also be increasing through the day as surface gradient tightens, and gusts of 35-55 mph will be possible in the Central Valley (strongest likely over the northern half of the Sacramento Valley) and a Wind Advisory has been posted.
Forecast soundings have been showing quite a bit of instability over the Central Valley behind the front later Saturday afternoon and into the evening with hail likely to accompany stronger storms, and maybe some funnel clouds. Shear will be the bigger question as to whether more organized and longer-lived storms will be able to develop. Currently, it’s looking like stronger shear will be to our southwest near the track of the mid-level speed max, but this may change and warrants keeping a close eye on for a potential window of severe weather.
In the Sierra, heavy snow will result in several feet of snow accumulation, and along with gusty winds will result in treacherous travel conditions.
A third system moves in later Sunday into Monday and has potential to bring another round of gusty winds. Heavy snow will continue in the mountains, but rainfall will likely be less over the valley compared to Saturday.
Extended Discussion (Tuesday through Friday)
Cluster analysis and ensemble guidance generally in good agreement for troughing and unsettled weather to remain over the region Tuesday and Wednesday.
However, Tuesday is looking mostly dry, with the exception of some showery activity over the northern mountains. There is still uncertainty with the Wednesday system, but at this point looks like additional light to moderate precipitation, mainly in the foothills and mountains. However confidence is still low for exact timing and amounts.
By Thursday, ensemble guidance suggests ridging to build back in, indicating a break in the unsettled weather pattern. The return of Valley fog will be possible as we shift away from the wet weather late next week.