June 2, 2020 – Slight chance of late-day showers and thunderstorms over the Sierra Nevada south of Lake Tahoe this week. Hot with high temperatures 10 to 15 degrees above average, then cooling with an increased chance of showers by the weekend.
Discussion
Cutoff low, nearly stationary south-southwest of NorCal, continues to send some mid and high clouds northward into the southeastern corner of the forecast area. The remainder of the region is under clear skies early this morning. Winds are generally light and current temperatures range from the upper 30s and lower 40s in the colder mountain valleys, to the 60s to lower 70s across the Central Valley and foothill and Sierra thermal belts.
Hot weather settles in across the region the next several days as high pressure strengthens. Highs will be around 10-15 degrees above average through Thursday with warmest valley highs peaking in the 100 to 105 range on Wednesday. Overnight lows will also be quite mild the next few days. The combo will lead to a moderate to high heat risk across the valley and foothills.
Late-day shower and thunderstorm chances will mainly be limited to areas of the Sierra Nevada to the south of Lake Tahoe the next few days.
Cooler and more unsettled weather forecast to return by the end of the week as the longwave trough over the Gulf of Alaska moves closer to the West Coast.
Extended Discussion (Saturday through Tuesday)
Pacific front moves through Saturday followed by associated upper low Sunday. As a result, wet weather expected for much of interior NorCal this weekend. Overall QPF is light with highest amounts over the mountains and north of I-80. Breezy to windy conditions accompany the frontal passage. Below normal temperatures expected with highs in the 70s for the Central Valley and mostly 40s to 60s for the mountains and foothills.
Drier weather expected Monday into Tuesday as trough axis shifts east, and upstream Pacific ridging begins to build over interior NorCal. Warming forecast with highs slightly above normal by Tuesday. Some gusty north to east wind possible early next week.