An active weather pattern continues through Monday with periods of rain, high-elevation snow and gusty wind. Heaviest rainfall and snowfall rates expected tonight into Monday morning.

Excessive rainfall rates possible

Discussion

The long anticipated final wave of this weekend weather system will begin to impact the region later this afternoon, bringing the heaviest precipitation tonight into Monday morning. As seen from satellite and radar, the beginnings of this wave are beginning to move into the CA coast. Time of arrival of this wave in the Sacramento area is between 6-7pm PST, with heaviest rain expected after 9-10pm PST. Storm total rain for the Valley locations hasn't changed much since the previous forecast, with the 36 hour totals of 1-2 inches with up to 3-4 inches in the foothills and mountains. Hires models indicate a fairly broad swath of moderate rainfall (0.25″-0.50″/hr rates) this evening potentially lasting for several hours, which may warrant short-fused flood products to highlight the flooding threats.

Flooding potential

Even so, if you encounter flooded roadways, turn around - don't drown. It only takes 6 inches of fast- moving water to sweep a car away.

Snow impacts Sunday-Monday

Snow levels briefly went down to around 5,000 feet this morning, allowing for a few inches of snow to accumulate, but snow levels have since increased to around 6,000-6,500 feet per CCTV cameras and observations, where they should remain through much of tonight. Total snowfall forecast also had minimal changes since the previous forecast, with around 8-16 inches above 6,500 feet and up to 2 feet along mountain peaks.

The Winter Storm Warning remains through 10 pm Monday.

Wind gusts Sunday night

Outside of precipitation, winds have remained breezy across the region, and will peak this evening-tonight with gusts across the Valley reaching around 30-35 mph, with localized locations potentially seeing gusts as high as 40 mph. Hires guidance is only highlighting about a 20-40% of seeing gusts greater than 40 mph this evening, and latest HRRR runs have generally trended downward. If winds do reach marginal advisory criteria they are expected to be brief, only lasting 1-3 hours. Given the short duration and localized nature of marginal Wind Advisory level winds and continued communication about the wind potential over the last several days, decided to forego a wind headline, given the main impacts are still expected to be those related to precipitation.

Rain forecast this afternoon through Monday

Widespread precipitation and gusty winds will diminish through Monday morning-afternoon across the region, with lingering precipitation across the foothills and mountains through Monday evening.

With diminishing cloud cover Monday afternoon across much of the Valley, hires guidance is indicating enough instability may develop for some isolated thunderstorms to develop, potentially bringing brief, heavy rain, gusty winds, and small hail.

Thunderstorms possible

As the upper-level lift quickly shifts eastward, the support for thunderstorm develop will be limited to only a few hours late tomorrow afternoon-early evening. Given this, shear will be limited too, not anticipating the organization of any thunderstorms, if they do develop.

By Tuesday morning, much of the precipitation chances will diminish, leaving behind light winds and a very saturated ground. If clouds move out quickly Monday night, fog development will be likely across the Valley. Confidence is marginal on the extent and density of the potential fog development Tuesday morning, given the uncertainty in cloud cover that morning.

Otherwise, much of Tuesday is expected to be mostly dry, before another weak system moves into the region late Tuesday night-Wednesday bringing renewed rain chances.

Rain on Wednesday is not expected to be impactful, with storm total amounts of 0.10″-0.25″ for much of the Sacramento Valley. Higher rainfall totals are possible across portions of the northern Sacramento Valley, where 0.50-0.75″ are possible, with locally higher amounts in the Shasta County mountains.

Snow levels will yet again be somewhat high, falling in the 5,000-6,500 foot range. With limited precipitation, this will only result in a couple of inches of snowfall (1-4″).

Extended Discussion (Thursday through Sunday)

Ensembles depict upper-level ridging is expected to move over Northern CA as a shortwave slides into the Great Basin area on Thursday. This will help moderate rainfall conditions, however an AR stretching into the Northwest Pacific glances over northwestern CA.

This will keep persistent precipitation chances over the mountains and Northern Sacramento Valley through Saturday night (25-50% chances). Confidence on amounts and timing is low, albeit trending higher that aforementioned areas will receive some precipitation late next week. Current probabilities show a 35-55% chance of exceeding 0.50 over the mountains and Northern Sacramento Valley Thursday through Saturday night.

Temperatures trend warmer with the rising heights, particularly next weekend but will depend on cloud cover and developing precipitation.