Isolated showers remain possible throughout the day today, with increasing chances for more widespread precipitation Friday into Saturday. A brief reprieve late weekend into early next week then leads into another round of increasing precipitation chances by mid next week.
Discussion
As of early this morning, mostly cloudy skies are being observed across the region with a few light radar returns indicating some lingering rain showers as well. As a result, temperatures across interior NorCal remain somewhat mild at this time and look to remain in the upper 40s to low 50s in the Valley and foothills with 30s to 40s at higher elevations. Isolated showers will remain possible throughout the day today as a weak shortwave moves through the southwesterly flow pattern aloft. Additional rainfall looks to remain light though, with only a 15 to 40% chance of exceeding 0.25″ of QPF across the far northern coastal range.
Moving toward the end of the week and early weekend period, another upper trough looks to impact the region late Friday into Saturday. This trough looks to follow a further southward trajectory, which will introduce higher chances for more widespread moderate precipitation at times.
This system looks to be wetter compared to the midweek system. As a result, probabilities of exceeding 1″ of QPF are in the 70 to 90% range over the higher elevations, with still a 40 to 60% chance across the Valley and foothills.
Furthermore, snow levels in the 5500 to 7000 foot range will see some accumulations possible at pass level. At this time, latest probabilities of exceeding 4″ of snowfall are in the 60 to 80% range along the Sierra, with still 40 to 60% probabilities of exceeding 8″ of snow as well.
The latter portions of the weekend may still see a few isolated showers lingering across the region, but a quieter period of weather should begin to usher in. High temperatures look to fall back a couple of degrees, but will still remain generally seasonable for much of the area. New Years Eve may be a little chilly as well with low temperatures dropping into the upper 30s to low 40s in the Valley and upper 20s to 30s at higher elevations.
Extended Discussion (Monday through Thursday)
The early week period will feature mostly quiet weather as a transient period of upper level ridging builds in. Despite this, temperatures look to remain more or less stagnant and seasonable for the region during this time frame.
A pattern change then arrives late Tuesday into midweek as the next upper trough within the wave train begins to impact the region. Details remain limited at this time, but increasing precipitation chances look possible across mid to late next week with this system.