Active pattern returns late week into next weekend bringing widespread precipitation, extremely heavy mountain snow with blizzard conditions, strong winds, and low elevation (1500-3000) snow accumulations. Following this system, expect near freezing Valley temps and AM frost.
Discussion – today through Friday
Key points of late week-weekend storm:
- Extremely heavy snow with BLIZZARD CONDITIONS expected in the Sierra late this week, heaviest Friday and Friday night. Storm total snowfall from Thursday into early Sunday is currently projected at 5 to 10+ feet for elevations above 5,000 feet, with significant disruptions to daily life likely.
- Mountain travel will be extremely dangerous to impossible, especially Friday.
- Significant snow accumulations are expected above 3,000 feet. Cold air will drop snow levels down to 1,500-2,000 by the weekend, with light accumulations possible at those levels.
- Wind gusts to 50 to 65 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.
- Strong winds are in the forecast Thursday through Friday in the Valley, gusting from 35 to 55 mph from Marysville northward.
Skies are clear across the region early this morning, and other than some lingering north wind over the northern Sacramento Valley, and winds are generally light. Current temperatures are mainly in the upper 30s to upper 40s across the Central Valley, and in the 20s and 30s over the mountains. Dry weather will continue today.
A strong, cold storm system will drop down from the Pacific Northwest, beginning to bring some precipitation chances mainly for the Southern Cascades, northern Coast Range, and Shasta County tonight. As the trough continues to quickly dig into the area Thursday, winds and precipitation will continue increase and spread southward.
Extremely dangerous to impossible mountain travel is expected Thursday and into the weekend. The Winter Storm Watch has been upgraded to a Blizzard Warning for the Northeast Foothills, Motherlode, Sierra, and Western Plumas/Lassen area above 2000 ft, and the Watch for the Coast Range, Shasta County Mountains, and Burney Basin has been upgraded to a Winter Storm Warning.
Snow rates of 2-4 inches per hour are expected, with road closures, white-out conditions and near zero visibility at times.
Very strong winds, combined with heavy snow could cause extensive tree damage and extended power outages.
The Blizzard conditions in the Sierra are expected Friday and Friday night, when snowfall is heaviest. Snow levels initially around 5000 to 6000 feet, lowering to 3000 to 5000 feet Friday, and down to around 1500 to 2000 feet by Saturday (with the lower end in Shasta County).
Gusty winds will also bring impacts on Thursday and Friday. The National Blend of Models (NBM) suggests a 60 to 95 percent probability of wind gusts greater than 47 mph in the Sacramento Valley north of Marysville, and a Wind Advisory has been issued for much of the north/central Sacramento Valley on Thursday. Gusty southerly winds are also expected on Friday.
The NBM also suggests a 10 to 20 percent probability of thunderstorm development on Friday afternoon and evening that could bring additional gusty conditions, as well as small hail, brief heavy rain and lightning.
Slick roads from rain are expected elsewhere in the Valley.
The time is NOW to prepare for this *significantly* impactful winter storm. Mountain travel is HIGHLY discouraged while the warnings are in effect!
Extended Discussion (Sunday through Wednesday)
Decreasing showers Sunday as main upper trough finally shifts east of the CWA. NBM snow levels Sunday morning are down around 1000-1500 feet as precip winding down. Additional short wave troughs progged through early next week keeping precip in the forecast. Precip expected mainly over the northern third of the forecast area Monday, then more widespread light to moderate precip possible Tuesday into Wednesday.