May 21, 2019
Summary: Scattered showers are widespread over northern and central California, especially from Fresno County northward. The weather will become more active as the afternoon and evening wear on as very cold air for the time of year moves overhead in association with a strong upper low now over northern California. Isolated thunderstorms would not be a surprise later this afternoon as convection begins due to strong daytime heating. Rainfall amounts from this event will range from a few hundredths to possibly more than .33 if and when thunderstorms occur.
Showers will continue tonight then end Wednesday morning, but will continue over the Sierra Nevada and Kern County mountains. Wednesday and Wednesday night will largely be dry on the valley floor then an interesting twist is projected to develop for Thursday and Friday. The low currently moving through will move into the interior west Wednesday then actually back up towards California, ensuring more showers and thunderstorms over the mountains with a small threat of widely scattered showers over the valley floor. Many locations will remain dry Thursday and Friday, however that small chance of measurable rain is certainly feasible.
Over the weekend, models continue to show a new low moving in from the Pacific Northwest, either moving overhead or skirting the coast as it moves southward. In either case, there will be a reasonably good chance of scattered showers and isolated thunderstorms Saturday, possibly lasting into early Monday morning. Tuesday still appears to be a possible turn around day for the beginning of a dry weather pattern, at least on the valley floor. Some models, though, continue to show a weak trough over the western states which would allow for a warming trend but readings would likely remain somewhat below average for late May. Keep in mind, average temperatures for this time of year are mid to upper 80s, depending on location.
Forecast: Periods of showers for the remainder of the afternoon through the night. a chance of isolated thunderstorms, mainly later this afternoon and evening. Mostly to partly cloudy Wednesday and Wednesday night. variable cloudiness Thursday through Friday with a small chance of scattered showers. Variable cloudiness Friday night through Saturday night with periods of showers and isolated thunderstorms likely. A slight chance of showers Monday morning. Partly cloudy Monday afternoon through Tuesday.
Temperatures: Lows tonight will chill into the mid 40s to near 50. Highs Wednesday will warm into the mid to upper 60s with overnight lows cooling into the upper 40s to the lower 50s. Highs Thursday will rise into the mid 70s.