Periods of moderate to heavy rain, high elevation snow, and isolated thunderstorm chances continue through Wednesday. Quieter and more seasonable weather is then anticipated late week into the weekend.

A warm system will bring periods of moderate to heavy precipitation today through Wednesday, with the heaviest precipitation expected late today into early Wednesday. This could lead to ponding of water on roadways. Slow down on wet roads & allow extra time to reach your destination.

Discussion

Scattered showers are evident across much of interior NorCal via latest radar imagery early this morning. Observed 24-hour rainfall totals so far range from around a half inch to an inch across the Valley, up to 1.5 to 2.5 inches over the mountains. This scattered activity looks to persist throughout much of the day today, before another round of more widespread precipitation arrives late Tuesday into Wednesday.

Moderate to heavy rain possible in these areas

Latest probabilities of exceeding an additional 1″ of QPF through the remainder of the event are in the 70 to 90% range, with highest probabilities over the mountains. Additionally, there is a 60 to 80% probability of exceeding 3″ of QPF over the mountains as well.

High elevation snow continues today-Wednesday, with the highest snow totals expected near Lassen Park and the Sierra south of Highway 50. Expect periods of travel delays and slick roads. Check road conditions before you go: quickmap.dot.ca.gov/

Snow levels look to remain high today, in the 7000 to 8000 foot range, before falling into the 6500 to 7500 foot range late today into Wednesday. Probabilities of snowfall exceeding 8″ above 7000 feet are in the 50 to 80% range for near Lassen Peak and for areas south of the Highway 50 corridor. With snow levels falling into Wednesday, some light accumulations may be possible at pass level as well.

Today, December 19, 2023. Most likely timeframe: Afternoon - Evening. Impacts: lightning, small hail, brief heavy rain, gusty winds.

Furthermore, isolated thunderstorm activity will also be possible this afternoon into the evening across portions of the Delta, Valley, and adjacent foothills locations. Current probabilities of thunderstorm development are in the 15 to 25% range. Any thunderstorms that do develop will be capable of brief heavy rainfall, gusty winds, and dangerous lightning.

A Wind Advisory is in effect until 10 AM Today for portions of the northern/central Sacramento Valley and northeast foothills for southerly winds 15-25 mph with gusts 35-45 mph. Be sure to secure any loose outdoor objects!

Gusty winds will also continue through Tuesday, with gusts up to 35 to 45 mph possible across the northern Sacramento Valley and over the Sierra.

Otherwise, moving toward the late week period, precipitation chances look to taper off early Thursday morning, with drier weather then anticipated.

A brief period of ridging aloft will see high temperatures warm into the low to mid 60s in the Valley on Thursday before a quick moving shortwave moves through late Friday. This wave will introduce some light precipitation to the region late Friday into Saturday, but accumulations look to remain light and generally confined to the mountains.

Extended Discussion (Saturday through Tuesday)

Moving into the weekend, precipitation chances may linger into the day on Saturday as the aforementioned wave moves through. This activity should generally begin to taper off though. This will then result in quieter weather for the bulk of the weekend with seasonable temperatures prevailing.

Cluster analysis then hints at some potential for west-southwesterly flow to setup, introducing the possibility for increasing precipitation chances once again moving into early next week.