Weak weather system brings precipitation chances this evening and into Friday. Warming trend expected this weekend with above normal temperatures by Sunday. Light precipitation possible for far northern California early next week.
Discussion
GOES-West nighttime microphysics imagery reveals scattered to broken mid/high clouds traversing overheard this early Thursday morning. These clouds are streaming ahead of the next system that is approaching the Pacific Northwest and northern California. For now, largely thanks to the increasing mid/high clouds, temperatures are running several degrees warmer compared to this same time 24 hour ago. This trend will similarly translate over to the morning lows throughout the region.
General trend for today will be increasing clouds through the day. Precipitation is expected to hold off until the late afternoon or evening for northern reaches of the area, then expanding south/east overnight and into Friday.
Precipitation amounts will remain on the light side: upwards of 0.25 to 0.75 inches for the central/northern Sacramento Valley, and less than 0.25 inches for points south in the Valley. Locally higher precipitation totals will be possible in the Shasta County mountains, possibly upwards of 1.00 to 1.50 inches. On the other hand, some areas south of Sacramento may see little/no rain.
Snow levels will be roughly 5000 to 6500 feet. Latest operational National Blend of Models probabilities advertise around a 15-20% chance of exceeding 4″ at Donner Pass and less than 10% chance of exceedance at Echo.
Areas of breezy south/west winds will be possible this afternoon and into Friday with gusts up to 30 mph for parts of the central/northern Sacramento Valley. Overall weather-related impacts are expected to remain on the low side with periods of slick roadways from rain and some minor winter travel-related issues in the mountains.
System exits on Friday afternoon with some lingering showers possible into the afternoon hours. Recent model runs have largely erased precipitation chances over the weekend with the NBM keeping PoPs at/below 10 percent through Sunday afternoon. Broad, low- amplitude synoptic ridging over the Western US will allow for day-to-day warming through Sunday with the potential for low/mid 70s for the Valley.
Both Redding and Downtown Sacramento have a 70-80% chance of exceeding 75 deg F for Sunday, or a few/several degrees above normal. In case you’re wondering, the last time Downtown Sacramento experienced a high that was above normal was on March 13: observed high was 70 deg F vs normal of 67 deg F.
Extended Discussion (Monday through Thursday)
Pacific frontal system progged into NW portions of CA Monday. Front appears to weaken as it moves inland with main threat of light precip over the northern Coastal range and Shasta county. Mainly dry weather expected Tuesday, then upper low digs along the CA coast Wednesday into Thursday. Available moisture appears to be limited, and best threat for showers at this time looks to be over the northern and eastern foothills and mountains. Cooling trend expected through the extended forecast period with below normal high temperatures Wednesday and Thursday.