January 31, 2024 – The next weather system arrives today bringing gusty southerly wind, periods of moderate to heavy rain and mountain snow, and isolated thunderstorms. Unsettled weather pattern remains in place as we move into the weekend as another system moves through interior NorCal. FloodWatch from this afternoon through late Thursday night. Winter Storm Warning from 10 AM this morning to 4 AM Saturday. Wind Advisory from 10 AM this morning to 6 AM Thursday.
Discussion
Increasing warm advection ahead of the approaching system is beginning to result in some sprinkles or light showers across much of the region early this morning. Southerly surface pressure gradient is also tightening leading to some local gusts in the teens to around 30 mph.
Surface gradient will continue to tighten today and southeasterly wind gusts will pick up this morning and persist into tonight when the front moves through, though the peak gusts are expected this evening before gradient slackens behind the front. Gusts of 40-55 mph will be possible in the valley with gusts over 60 mph possible across exposed higher terrain. A wind advisory remains in effect.
While some light precipitation will be possible today, heavier rain will develop late this afternoon and move through overnight. Around 1 to 2 inches of rain will be possible in the valley with 1.5 to 4 inches in the mountains through Thursday morning.
Local upslope enhancement will be possible along the western edge of the Sacramento Valley, over the mountains north of Redding, and over eastern Butte and western Plumas counties.
The onset of the floodwatch has been pushed back until 4 PM.
In the mountains, heavy snow will be possible late this afternoon and overnight tonight as the front moves through. Snow levels will be above 6k ft initially, but will lower on Thursday.
More intermittent snow is expected by later Thursday morning. 1-2 feet of accumulation will be possible over the higher elevations where a winter storm warning remains in effect.
Showers and a few thunderstorms will be possible in the post-front environment Thursday and Friday along with modestly lower snow levels over the mountains, and even a few showers may linger into Saturday as additional short-wave trough energy slides across the region.
Extended Discussion (Sunday through Wednesday)
539 DM upper low continues off the CA coast Sunday with another AR progged to push into the CWA from the SW. This will result in another round of moderate to heavy precip depicted by models Sunday into Monday.
Given trajectory of storm and associated sub- tropical jet, current NBM snow levels may be too low and will need to be monitored with additional runs.
Secondary upper low then drops into the long wave Tuesday with vortices rotating around each other and merging in a Fujiwara fashion.
Cyclonic flow with persistent upper low offshore will continue showery weather over the CWA Tuesday into Wednesday.