December 16, 2023 – Quiet and seasonable weather prevails through much of the weekend. Increasing chances for rain and high elevation snow then arrive late Sunday lasting through Wednesday.
Discussion
As of early this morning, latest GOES-West imagery shows high cloud cover over much of the region. This is working to keep overnight temperatures a couple of degrees warmer than last night. Early morning lows are still expected to dip down into the mid to upper 30s throughout the Valley though. After another chilly start, skies are generally expected to clear throughout the day, resulting in high temperatures by this afternoon in the low to mid 60s throughout the Valley and foothills and 50s in the mountains.
As upper level ridging prevail over the Great Basin into Sunday, mostly quiet weather looks to persist as well. Despite this, with troughing off the coast gradually inching eastward, cloud cover is expected to increase on Sunday, resulting in slightly cooler high temperatures.
As the aforementioned trough meanders eastward late Sunday into the early week ahead, precipitation chances will begin to increase as well. Generally light precipitation is anticipated late Sunday into early Monday, with periods of moderate to heavy precipitation then expected Monday and Tuesday.
As this is a relatively warm system, rain will be the primary precipitation type for much of the region. That being said, snow levels look to remain around 7000 to 8000 feet through the early week period, likely confining much of the accumulating snowfall to high elevation/peak levels.
Best chances for heaviest snowfall will be at these high elevation areas near Lassen Peak and south of the Highway 50 corridor.
At this time, probabilities of exceeding 1″ of QPF through the early week period are in the 60 to 90% range, with probabilities remaining the same over the mountains, but lowering to the 30 to 60% range in the Valley for probabilities of exceeding 2″ of QPF.
As for snowfall, probabilities of exceeding 4″ are in the 60 to 90% range for elevations generally greater than 8000 feet, with probabilities of exceeding 8″ in the 40 to 80% range for the same areas.
Furthermore, increasing south to southeast winds are also anticipated Monday into Tuesday with occasional gusts of 35 to 35 mph possible, strongest across the Sierra.
Extended Discussion (Wednesday through Saturday)
Rain and high elevation snow will continue into Wednesday, but will be beginning to taper off. This is highlighted by probabilities of exceeding 0.5″ of rainfall on Wednesday only in the 20 to 40% range across the Valley.
High elevation snowfall is still anticipated as well with snow levels expected to dip down into the 6500 to 7500 feet range on Wednesday. Probabilities of exceeding 1″ of additional snowfall on Wednesday are in the 50 to 70% range, with highest chances remaining near Lassen Peak and south of the Highway 50 corridor.
Isolated showers may continue into Thursday, primarily over the Sierra, but overall a drying trend is anticipated across the late week period.
As the aforementioned trough dips down across southern California, a period of ridging aloft looks to build in across late week, facilitating this quieter weather trend and keeping temperatures more or less stagnant and seasonable.