Dry weather persists today. Rain chances return Wednesday with a wetter pattern developing this weekend with rain, high-elevation snow and gusty wind expected.
Discussion
The strong ridge along the west coast is beginning to get undercut as the main block lifts north toward southeast Alaska and the Yukon. A weak short-wave is approaching northwest California this morning and will drift by today with little impact other than bringing another batch of cloudiness to the region. Some patches of fog will be possible again this morning in the Central Valley from about the Sacramento area southward as current temperatures and RH‘s are similar to readings from 24 hours ago, but high clouds will be increasing before sunrise which may limit the extent of fog development similar to Monday morning.
A stronger short-wave trough will move through on Wednesday into Thursday bringing more widespread precipitation to the region along with breezy conditions (gusts 30-40 mph possible in the northern Sacramento Valley and across higher terrain).
Some light precipitation will be possible late tonight and Wednesday morning as a warm front lifts north, then more substantial precipitation is expected to spread south and east Wednesday afternoon and night as the cold front moves through.
Moderate travel impacts are expected in the Sierra later Wednesday into Thursday morning with about 8-12 inches (greater than 80% chance for 8″, and greater than 50% chance for 12″) of snowfall possible above 5500 feet leading to chain controls and travel delays over the higher passes.
As far as QPFgoes, 0.25″ to 0.50″ will be possible through most of the Central Valley except for around an inch up by Redding. In the mountains, 1.50″ to 3″ are forecast with the highest amounts over the mountains north of Redding and across the Feather River basin where southerly flow will lead to orographic enhancement.
A relative break in precipitation is expected later Thursday through much of Friday as short-wave ridging moves overhead before more substantial precipitation returns Friday night heading into the weekend’s systems.
Extended Discussion (Saturday through Tuesday)
Heading into the weekend, ensemble guidance and cluster analysis favor a continued active weather pattern with two additional waves of precipitation through the extended period. Periods of moderate to heavy precipitation, high-elevation mountain snow, and occasionally gusty winds are expected with these two systems. These winds are currently on track to be weaker compared to the February 4th wind storm.
For storm 2:
The NBM is advertising a 50 to 80% chance of 1.00″ or more of rainfall in the Valley, with the majority of precipitation expected north of I-80. In addition, there is a 40 to 60% chance of 12″ of snow over the Sierra and southern Cascades with snow levels initially at 6000 to 7000 feet on Saturday before lowering to 5000 to 6000 ft on Sunday.
Beginning Sunday afternoon, we’ll enter a transitional period between storm 2 and storm 3, with storm 3 peaking overnight Sunday into Monday. Light precipitation is expected throughout the day on Sunday prior to periods of moderate to heavy rainfall Sunday night into Monday.
Once again, the heaviest precipitation is expected north of I-80. The NBM is indicating a 40 to 60% chance of 1.00″ or more of rainfall in the Valley with a 60 to 80% chance over the mountains/foothills.
In regards to snow amounts, there is a 50 to 70% chance of 12″ or more over a 48 hour period ending Tuesday at 4pm. Snow levels will generally be between 5000 and 6000 feet through Tuesday.
As we approach the holiday weekend, make sure to check road conditions and the forecast before traveling or making any holiday plans.
There continues to be a high degree of uncertainty with these storms in regards to timing and amounts. As always continue to check back for updates over the next few days as we learn more and our confidence increases.