February 29, 2024 – Major Winter Storm impacting area today through the weekend, bringing widespread precipitation, extremely heavy mountain snow with blizzard conditions, strong winds, and low elevation (1500-3000) snow accumulations.
Discussion – today through Sunday
Key points of late week-weekend storm:
- Extremely heavy snow with BLIZZARD CONDITIONS expected in the Sierra, heaviest this afternoon through Saturday. Storm total snowfall into early Sunday is currently projected at 5 to 10+ feet for elevations above 5,000 feet, locally higher amounts of 12+ feet are possible at peaks, with significant disruptions to daily life likely.
- Mountain travel will be extremely dangerous to impossible, especially this afternoon through Saturday.
- Significant snow accumulations are expected above 3000 feet. Cold air will drop snow levels down to 1000-2000 by the weekend, with light accumulations possible at those levels.
- Wind gusts to 55 to 75 mph are expected over the mountains. Expect snow rates of 2-4+” per hour. These will combine to bring whiteout conditions with near zero visibility at times beginning today, but especially Friday and Saturday.
- Strong winds are forecast in the Central Valley with gusts of 40 to 55 mph from Yuba City northward today, and from Modesto northward on Friday.
Active weather prevails across interior NorCal this afternoon. At 1203 PM, a strong line of showers and thunderstorms was observed near Redding into Red Bluff, with several observed lightning strikes recorded and gusty winds around 50 mph.
Snowfall in the Sierra began early this morning, with several roadways requiring chain controls this afternoon, as snowfall has continued and is covering roadways. Conditions are expected to continue to deteriorate as we move through the afternoon and evening. Extremely dangerous to impossible mountain travel is expected into the weekend.
A Blizzard Warning has been issued for the Northeast Foothills, Motherlode, Sierra, and Western Plumas/Lassen area above 2000 feet and a Winter Storm Warning has been issued for the Coastal Range, Shasta County Mountains, and Burney Basin. Snow rates of 2-4+” inches are expected, with road closures, white-out conditions and near zero visibilities at times.
Very strong winds, combined with very heavy snowfall could cause extensive tree damage and extended power outages.
Blizzard conditions are expected through Saturday. Snow levels will start out around 5000 to 6000 feet today, lowering to 3000 to 4500 feet Friday, then down to 1000 to 2000 feet Saturday. Total snowfall will be measured in feet from this event, with the National Blend of Models (NBM) suggesting 12 feet or more of accumulating snowfall or more in the Sierra.
Afternoon model runs continue to increase snowfall totals along the Sierra. Areas along I-5 in Shasta County will likely see up to a foot of snow or more, so significant travel delays and road closures are possible.
Gusty winds will also bring moderate impacts to the region through Friday.
Strongest winds will be north of Sacramento today, but will likely spread south on Friday as the next wave moves through. A Wind Advisory remains in effect for the central and northern Sacramento Valley through 4AM PST Saturday morning. The Wind Advisory will expand to include the northern San Joaquin Valley and southern Sacramento Valley at 10 AM PST Friday through 4 AM Saturday.
Thunderstorms have been observed with a strong line of storms from Redding to Orland this afternoon, and will remain possible today as the initial front moves south this afternoon and evening.
The EC Extreme Forecast Index (EFI) highlights areas in interior NorCal for potential thunderstorm development tomorrow and Saturday, and the NBM supports a slight chance (10-25%) for T-storm development mainly in the Valley and Foothills in the afternoon and evening. Hazards from any T-storms that develop will include additional gusty winds, small hail, brief heavy rain and lightning.
Rainfall for the Valley still looks to remain below 1.50″ inches, with higher amounts of 2.00 to 4.00″ inches in the Foothills and the mountains around 4.00 to 8.00″ inches with locally heavier amounts, through Saturday night.
Additional snowfall is likely after the warnings have ended Sunday morning. We remain in west-northwesterly flow which will allow moisture and cold air to continue to move into the area. Most of the impacts will be felt in the Sierra, Southern Cascades, Coastal Range, and the Foothills, with limited Valley rainfall thanks to shadowing.
Snow levels on Sunday could be as low as 1500 feet in the Sierra, and around 1000 feet in Shasta County. Additional snowfall may hamper blizzard recoveries.
Mountain travel is HIGHLY discouraged while the warnings are in effect!
Extended Discussion (Monday through Thursday)
The start of next week is looking at the passage of a secondary storm system as a shortwavetrough moves over the area. This storm will be less impactful than the weekend storm, though moderate snow is still expected above 3500 ft through Wednesday, and may cause additional travel delays early next week.
Currently the NBM is projecting a 30 to 55% probability of at least 12 inches of snow between 3500 and 5000 ft, and a 55 to 65% probability of at least 12 inches above 5000 ft between Monday and Wednesday.
Additionally, there is a 40 to 55% probability of at least 18 inches of snow above 5000 ft during the course of the storm. Valley precipitation will be more limited, with most rain occurring in the northern Sacramento Valley and northern foothills.
NBM is currently projecting a 35 to 50% probability of 0.25 inches of rain or more in the northern San Joaquin Valley and majority of the Sacramento Valley, with a 40-70% probability of at least a half inch in the northern Sacramento Valley. Most rain in the Valley will occur Tuesday and Wednesday.
Thursday and beyond there is still quite a bit of uncertainty in the ensembles, with some solutions showing a trough remaining over the area and others showing ridging. Be sure to check back in for updates to the forecast!