May 31, 2019 – Afternoon and evening mountain showers and thunderstorms through the weekend them showers remaining mainly over the Sierra early next week. Dry conditions for the end of the week. Above normal temperatures through the extended period.
Skies have cleared out again this morning as more stable nighttime conditions have taken over. Mountain showers and thunderstorms will return this afternoon, however, and this cycle will continue through the weekend at least. Current Water vapor imagery shows an upper low over NorCal with its center currently locations somewhere between Sacramento and Tahoe. This low will be the primary controller of the weather over the next several days. MU cape proggs showing plenty of instability for afternoon shower and thunderstorms with PW proggs still showing 1 inch or more of TPW lingering over the region. Instability, moisture and orographic lift of the mountains, foothills and northern Sacramento valley convergence will bring scattered thunderstorms again today as afternoon heating develops. Generally light winds, high atmospheric moisture content and instability will mean some of these storms may contain heavy rain and accumulating hail. The upper low will be dropping slightly southward today allowing for a slight warming over Thursday. Daytime highs are forecast to come in several degrees above normal for this time of year.
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Although the low center is forecast to move into SoCal on Saturday there will still be plenty of instability and moisture for a return of mountain showers and thunderstorms Saturday afternoon. Daytime highs will jump up another notch reaching about 10 degrees above normal. The upper low only moves slightly between Saturday and Sunday so overall weather Sunday should be fairly similar to Saturday. The upper low starts to open and move to the southeast n Monday as high pressure begins to push in off the eastern Pacific but Sierra will remain under cyclonic flow so some afternoon thunderstorm threat will remain there. Warming airmass will notch up daytime highs a bit more going into next week.
Extended Discussion (Tuesday through Friday)
Upper ridging over NorCal Tuesday will result in high temperatures upwards of 10 to 15 degrees above normal. Temperatures will gradually trend down through the remainder of the week as the upper ridge weakens and shifts east and upper troughing deepens. Afternoon instability will keep a slight chance of showers and thunderstorms over the higher elevations of the Sierra Nevada Tuesday and Wednesday.