Key messages
- Scattered showers, thunderstorm chances, and high elevation snow showers through this evening. Lingering mountain showers Friday morning.
- Breezy north to east winds develop Friday afternoon into Saturday AM, followed by weaker downsloping winds Sat PM-Sun AM.
- Dry weather continues through most of next week, with potential for unsettled weather Halloween Weekend.
Discussion
...Today through Friday AM... Cloudy skies and scattered showers are actively being observed across interior Northern California. Some isolated moderate to heavy rain will be possible at times, but precipitation will largely be light to moderate. Shower activity will gradually trend down through the afternoon hours, but a few scattered light showers may linger over the Sierra. Given the cloud cover and lack of instability as this weather system treks through Southern California, the threat for thunderstorms has largely trended down, but an isolated thunderstorm (10-15% chance) is still possible over the Sierra and Motherlode this afternoon/early evening. Forecast precipitation amounts for the remainder of the day are around 0.10 to 0.20 inches in the Valley, with higher amounts just over 0.50 inches along the Sierra.
Snow levels continue to be around 8000-9000 feet in the Sierra today, with additional snowfall amounts of 1-3 inches at the highest peaks. Best chance for snow will be toward Mono county and into the Yosemite area. Minor impacts are possible at the highest elevations in Tuolumne county and toward Alpine due to the snow.
Low clouds and potential for fog development in the Valley are possible tomorrow morning as well and may make the morning commute difficult at times.
...Friday (rest of the day) through Monday... Dry conditions are expected by Friday afternoon/evening, with RH values dropping to the 20 to upper teens for portions of the northern Sacramento Valley. As the trough digs into the southwestern United States and ridging develops off the NorCal coast, winds will shift out of the north in the Valley and north to east along the slopes of the Sierra. We will see gusty winds during the afternoon/evening on Friday with gust up to 35 mph within the northern Sacramento Valley for areas along and west of I-5. Areas within the mountains may see gusts up to 40 mph especially through gaps and canyons. A weaker period of downsloping winds is expected Saturday evening into Sunday morning, with gusts 20 to 30 mph. No broad/large scale fire weather concerns are anticipated given recent rainfall, but isolated fire weather concerns will be possible in places in the Sierra and Valley where little rainfall occurred.
Temperatures begin to trend higher as we head into next week as ridging builds, but will remain a few degrees below normal. A few isolated showers are possible over Shasta County Sunday and Monday, but any amounts will be very light as a trough passes through the Pacific Northwest.
...Tuesday and Beyond... Dry weather continues through the rest of the work week, but there is the potential for unsettled weather as we close out October and head into November. Details are fairly uncertain since we're so far out, but this week will be an ideal time to clear gutters and secure loose outdoor decorations and items in preparation for any additional precipitation that comes our way.
Aviation
Showers and isolated thunderstorms continue through the afternoon and evening hours, with localized areas of MVFR to IFR ceilings. Best timeframe for thunderstorms will be 2000z through 0400z for all sites with a 10-15% chance of occurrence. Winds will remain light throughout the day outside of erratic winds near thunderstorms. After 06z Friday, showers linger over the Sierra into Friday 18z and fog and stratus in the Valley overnight after 09z Friday with lowered ceilings as low as IFR to LIFR ceilings. Snow levels 7500-8500 feet until lowering after 12z Friday to around 6000-8000 feet.
Sto Watches/Warnings/Advisories
None.