Similar temperature trend today with below normal temperatures this week. Chance of afternoon showers and thunderstorms over the mountains through Thursday. Periods of gusty winds Wednesday and Thursday.
Discussion
Lingering showers from last evening have tapered off and conditions have quieted now for this morning. The low off the SoCal has begun to shift eastward towards the coast and models move it along the coast by this afternoon. As a result, another round of isolated showers and thunderstorms is expected for this afternoon and evening, primarily south of Hwy. 50. Isolated showers and thunderstorms continue for Wednesday across the Sierra and portions of the foothills (10-20% probability).
Thursday should be the more active of the two days as the low from the Pacific NW moves towards northeastern CA, giving more instability for rain to develop along the Sierra (20-40% probability).
The low begins to shift eastward Friday causing chances to taper off and be drier for the weekend as weak riding moves over Northern CA. Gusty winds look to develop with the passage of the low over the forecast area. Onshore flow will induce locally elevated winds across the Delta and higher terrain at time through the week.
Notably, winds turn northerly-northeasterly across the Northern Sacramento Valley, along I-5 Wednesday evening into Thursday evening, with strongest gusts on Thursday up to 30-35 mph. Models have trended upwards in confidence in wind gusts exceeding 25 mph from yesterday as we get closer to the event. EC Extreme Forecast Index (EFI) contours also support this showing a signature in a similar area for the Wednesday into Thursday time frame.
Similar to the precipitation chances, once the upper-level low begins to shift east Friday, conditions taper off outside of breezy southwest winds across the Delta.
Relative humidity values also lower Thursday leading to some enhanced fire weather concerns for portions of the Sacramento Valley. Temperatures will be relatively similar today and tomorrow, albeit a few degrees warmer today across the Northern Sacramento Valley. Temperatures cool again for Thursday and Friday, dropping down to low to mid 80s across the Valley.
Extended Discussion (Saturday through Tuesday)
Ensembles indicate a transition to a more amplified pattern over the weekend and into next week as this week’s low shifts east. Over the weekend, NorCal forecast to be in between the ridge centered over the Rockies and a deeper trough over the eastern Pacific.
Temperatures will be around 5-10 degrees below average with locally breezy southwest winds.
Prospects for widespread light precipitation appear to be increasing early next week as a majority of clusters have the ridge shifting further east into the central US allowing the trough to edge closer to the coast. By Tuesday, about 70% of clusters are indicating at least some light precipitation for the northern half of the forecast area.