Weather temperatures rise on Wednesday
Similar trend for today’s temperatures with below normal temperatures this week. Chance of afternoon rain and thunderstorms in the mountains until Thursday. Periods of gusty winds Wednesday and Thursday.
The rain that has persisted since last night has diminished and conditions have now calmed into this morning. The low off SoCal has begun to shift eastward toward the coast and is being moved by models along the coast this afternoon. As a result, scattered showers and thunderstorms are expected this afternoon and evening, especially south of the interstate. 50. Scattered showers and thunderstorms will continue Wednesday across the Sierra Mountains and parts of the Foothills (10-20% chance).
Thursday should be the more active of the two days as the low moves from the Pacific Northwest toward Northeastern California, giving more instability to rain development along the Sierra (20-40% probability).
The low begins to shift east on Friday causing opportunities to decline and become drier for the weekend as weak riding moves over Northern California. Stormy winds are expected to develop as the low passes over the forecast area. Onshore flow will stimulate localized high winds across the delta and high terrain at some point during the week.
Notably, winds are moving toward the north-northeast across the northern Sacramento Valley, along I-5 Wednesday evening into Thursday evening, with the strongest gusts on Thursday reaching 30-35 mph. Models have trended upward in confidence in wind gusts exceeding 25 mph from yesterday as we approach the event. The contours of the European Commission’s Extreme Expectations Index (EFI) also support this view which shows a signature in a similar area for the Wednesday to Thursday time frame.
Similar to rain chances, once the low begins to shift eastward on Friday, conditions diminish outside of breezy southwesterly winds across the Delta.
Relative humidity values also dropped Thursday enhancing some fire weather concerns in parts of the Sacramento Valley. Temperatures will be relatively similar today and tomorrow, albeit a few degrees warmer today across the northern Sacramento Valley. Temperatures will drop again Thursday and Friday, dipping into the low to mid 80s across the valley.
Extended discussion (Saturday to Tuesday)
The sets indicate a move into a more exaggerated pattern over the weekend and into next week as this week’s low turns east. Over the weekend, NorCal is expected to be between a ridge centered over the Rocky Mountains and a deeper trough over the eastern Pacific Ocean.
Temperatures will be 5-10 degrees lower than normal, and winds will be southwesterly brisk.
The potential for widespread light rain appears to be increasing early next week as the ridge for the majority of groups moves east into the central United States allowing the trough to move closer to the coast. By Tuesday, about 70% of ensembles indicate at least some light rain in the northern half of the forecast area.