Breezy winds and isolated, light showers continue through today. Mild and dry weather then arrives mid to late week, with a period of strong, gusty north to east winds from Wednesday afternoon through Friday (strongest Wednesday evening through midday Thursday). The warming trend then continues through the weekend and into early next week.
As of early this morning, isolated to scattered light showers are ongoing across interior NorCal. This activity looks to become more isolated through the morning, with only a few spotty showers possible through this afternoon. Additional precipitation through today will be minor impact at most, with up to a few hundredths possible throughout the Valley and foothills and up to 0.25″ possible over the Sierra. Snow levels remain fairly steady, around 4500` to 6000`, keeping additional accumulations confined to around 5000` and above. Heaviest snowfall is expected to occur early this morning, but despite this, snowfall totals will remain rather light. At this time, additional snowfall accumulations of 2 to 6″ will be possible, with locally higher totals at highest peaks.
A breezy south-southwesterly wind will also persist into the afternoon, with gusts to 25 mph across the northern Sacramento Valley and adjacent foothills, and gusts to 35 mph over the Sierra.
Otherwise, by the afternoon, aside from a stray shower here or there, quieter weather is expected for most, with winds trending downward throughout the day. Mostly cloudy skies should begin to clear by late afternoon/early evening as the system exits the region and heights aloft begin to rise. While cloud cover will keep high temperatures today similar to yesterday, the overnight clearing will work to bring Wednesday morning low temperatures about 5 degrees cooler than previous nights (Upper 30s to low 40s in the Valley/foothills and teens to low 30s at higher elevations).
Moving into Wednesday, a bit of a pattern shift looks to build into the region. A progressive upper trough moving through the Pacific Northwest is expected to become sandwiched between building ridging aloft over the southeastern CONUS and Pacific Northwest alike. This will allow for the trough to deepen into a closed low and retrograde through the Great Basin toward the Desert Southwest following an “Inside Slider” pattern.
While the immediate center of the system will be more in the vicinity of NorCal, a strong, attendant mid level jet streak on the western periphery of this system, will bring strong wind impacts to interior NorCal. Surface winds are expected to shift to a north to east direction (northerly in the Valley, east-northeasterly over the Sierra/adjacent foothills) overnight Tuesday into Wednesday morning, increasing Wednesday afternoon and evening, peaking Thursday morning, and gradually decreasing from Thursday afternoon through Friday. Strongest gusts are expected over the Sierra, where widespread gusts 55 to 65 mph (locally to 70 mph in strong wind prone passes) will be possible overnight Wednesday through midday Thursday.
Additionally, gusts 40 to 50 mph will be possible at elevations above 4000` along the Sierra. At Valley locations, more northerly gusts of 30 to 40 mph are expected through the Sacramento Valley from the I-5 corridor eastward, with gusts 40 to 50 mph possible west of the I-5 corridor and into the Delta. All in all, probabilities of wind gusts exceeding 40 mph are in the 50 to 90% range from I-5 westward, with similar probabilities above 4000` along the Sierra.
With strong winds in the forecast, take time to prepare now for difficult driving conditions, downed tree branches, and possible localized power outages, and be sure to secure any loose outdoor items.
Moving into Friday, there is still some uncertainty in the forecast, primarily regarding the evolution of the closed low. As it stands now, still gusty (but much lesser) north to east winds are expected through Friday, but their exact magnitude will be dependent on the progression of the closed low. Regardless, with the upper levelridge continuing to build in over the Pacific Northwest, heights aloft look to increase over interior NorCal. This will lead to warming surface temperatures into the weekend, with Valley high temperatures in the low to mid 70s and upper 50s to mid 60s across the foothills and mountains by Friday afternoon.
EXTENDED DISCUSSION (Saturday THROUGH Tuesday)
Interior NorCal becomes sandwiched between upper high to the north and upper low SE through the extended forecast period. Locally gusty offshore wind lingers through early Saturday in portions of the foothills/mountains then lighter wind expected. Dry weather forecast through the weekend into early next week with high temperatures around 10 degrees above normal.