Dry weather through the weekend. Temperatures warming back into the mid 70s to lower 80s across the Central Valley over the weekend. Travel impacts across the mountain passes Tuesday – Wednesday due to snow and gusty winds. Widespread rain showers in lower elevations Tuesday-Wednesday. Coolest temperatures of the season expected by mid-week.
Discussion
Clear skies cover interior NorCal as ridging has moved in. Surface pressure gradient has relaxed and winds are lighter compared to 24 hours ago, though local easterly gusts of 15-25 mph linger across the west slopes of the northern Sierra. Current temps in the valley are considerably cooler compared to 24 hours ago in the locales that were breezy yesterday – Redding and Red Bluff are running 10-15 degrees cooler and currently in the mid to upper 40s. Elsewhere, readings are mostly a bit milder with temps in the upper 40s to mid 50s across the Central Valley.
Dry and milder weather will linger through the weekend with occasional high clouds as systems pass to our north into the PacNW and BC. Ridging and light northerly surface flow will result in high temperatures reaching the mid 70s to lower 80s across most of the Central Valley on Sunday, perhaps the last 80+ highs we’ll see this year.
Ensembles in good agreement that the ridge will flatten and shift east beginning Monday as the more significant trough next week approaches. Dry weather will persist for another day, but temps will begin to cool.
Extended Discussion (Tuesday through Friday)
Ensembles are in good agreement for upper level trough to approach the west coast early next week. Confidence is high for cooler temperatures returning to interior NorCal over the extended forecast period. However, with regards to precipitation, there is still uncertainty in exact timing and amounts, as there are some differences in the models during that mid-week timeframe. As of right now, precipitation chances start late Monday night, with the bulk of it falling Tuesday-Wednesday, and some lingering chances early Thursday.
The National Blend of Models has a 30-40 percent chance of Valley locations observing a quarter of an inch of rain or higher Tuesday evening to Wednesday evening, with higher probabilities in the foothills and mountains for the same amount.
Snow levels over the Sierra Nevada look around 7000 ft at the onset of precipitation, however as the colder air moves into the area, snow levels will continue to drop through Thursday morning.
In addition to the cooler temperatures and precipitation chances, locally gusty winds are also looking more likely both ahead of, and following the passage of this trough. Gusty onshore winds will be possible over the ridgetops on Tuesday, and depending on when the trough shifts eastward, breezy northerly winds may bring additional impacts to the area later in the week.