Dry and seasonable weather persists through Tuesday afternoon, ahead of our next winter storm bringing heavy snow, gusty winds, rain w/ isolated t-storms Wednesday and Thursday. Active weather will continue through the weekend with the potential for another major winter storm into early next week.
Discussion
As we are in the literal quiet before the storm, we will see another warm and dry day with scattered cloud cover as the main forecast highlights today.
Looking to tomorrow, we will see the pattern shift, first with increasing winds across much of the CWA (County Warning Area) Tuesday afternoon and evening with gusts of 20-35 MPH throughout the Valley, up to 45 MPH over portions of the northeastern foothills and Northern Sac. Valley. Wind are expected to increase into Wednesday with peak gusts expected 30-45 MPH in the Central Valley and up to 55-65 MPH over the foothills and mountains. Strongest winds are forecasted to be late morning Wednesday across much of the Central and Northern Sac. Valley and northeastern foothills.
On Thursday, winds taper down with lingering strong gusts up to 35-40 MPH over the Sierra. NBM probabilities have a 40-70% chance of gusts above 40 MPH across the Central and northern Sac. Valley and the adjacent foothills. With an elevated wind signal showing on the EC Extreme Forecast Index and the persistent forecast signal the winds have shown over the last several days, a Wind Advisory will be in effect from 8 PM Tuesday to 11 PM Wednesday for gusts 45-55 MPH across the Northern and Central Sac. Valley and Northeastern Foothills. Strongest area of winds will be the northeastern foothills with the windiest period being Wednesday late morning to early afternoon.
In regards to snow, Winter Storm Warnings are in effect from 10 PM Tuesday to 10 PM Thursday for the Shasta County Mtns/Coast Range, Southern Cascades, Lassen NP areas, and Sierra for heavy snow and gusty wind causing moderate to major travel impacts expected.
For Shasta County/Coast Range/Burney Basin Abv 3000 feet: 4-12 inches, up to 1-2 feet expected with winds 30-45 MPH, up to 50-60 MPH. Difficult travel with travel delays, chain controls, and possible road closures are expected with low visibility from the combination of wind and snow. Heaviest snow expected Wednesday morning and afternoon.
For S. Cascades/Lassen NP/W. Slope Northern Sierra Nevada: 1-3 feet expected, up to 4 feet over the highest peaks and winds up to 65 MPH from 10 PM Tuesday to 10 PM Thursday. Travel is highly discouraged as it will be very difficult to impossible from snow-covered roads, chain controls, road closures, and significant travel delays all expected. Heaviest snow is expected Wednesday through the evening hours.
With both systems, please check the latest road conditions at quickmap.dot.ca.gov or dial 5 1 1 before making any travel attempts. Although rates will slow on Thursday, please continue to monitor the forecast as subsequent waves will follow and there may not be a clean break in the weather and/or resulting travel conditions.
Lastly, we can expected minor to moderate impacts from rain as periods of moderate rain moves through the Valley. Most of the Central Valley will see 0.50-1.00″ with 1 to 3 inches across the adjacent foothills and Northern Sac. Valley. The thunderstorm threat has reduced for Wednesday to below 15% now with Thursday (15-25% chance) now looking to be the better day to see isolated thunderstorms with best chances across the Eastern Valley and adjacent foothills.
Overall, we can expect several days of impactful weather with snow being the biggest driver of inclement weather this week. Please check weather.gov and find the latest forecast for you and your loved ones!
Extended Discussion (Friday through Monday)
Despite the expectation for the midweek trough to remain relatively progressive as it ejects toward the Plains late week into the weekend, very little reprieve from active weather is expected for interior NorCal. As the trough translates eastward, predominantly northwesterly flow aloft looks to remain in place from Friday into the weekend. A subtle shortwave traveling through the flow pattern Friday will pull a weak atmospheric river plume along with it and introduce additional precipitation impacts throughout the day on Friday. Given the southeasterly trajectory, most accumulating precipitation is expected across the northern Sacramento Valley and along the Shasta County mountains toward the Sierra/southern Cascades. As a result, mountain snow, primarily above 4000 feet, looks to be the main impact from this progressive system, with isolated light showers possible for Valley locations. While exact details remain a bit uncertain, there is some potential for light snowfall accumulations into the upper foothills as temperature and snow level recovery from the midweek system will likely remain limited. With snow amounts trending upward for this period, continued moderate impacts look likely with major impacts still remaining a possibility, if from nothing else than several days of snow with no clear break.
Furthermore, ensemble guidance in indicating another stronger trough building into the region by the weekend. There are notable differences between ensemble suites regarding the magnitude and trajectory of this trough, but most solutions are trending toward potential for additional travel impacts from precipitation into the weekend. With a prolonged period of active weather expected to encapsulated much of the next 7 days ahead, be sure to take time to prepare for adverse weather impacts, monitor the forecast for additional updates, and be sure to have a reliable way to receive weather and travel alerts.