June 11, 2020 – Above average temperatures with moderate heat risk today. Cooler temperatures, breezy winds, and shower/thunderstorm chances return Friday and Saturday. Dry weather Sunday with a modest warming trend.
Quiet weather is seen overnight with high clouds beginning to make their way over far northern California as the upper ridge continues to shift eastward today. Another day of very warm temperatures is expected as highs reach back into the 90s in the Valley. High clouds may mitigate temperatures slightly with some locations remaining a few degrees cooler than seen on Wednesday. Moderate heat risk will be seen in the afternoon in portions of the Sacramento and northern San Joaquin Valleys. Groups sensitive to heat should take extra precautions today, including outdoor workers.
Onshore flow picks up in the evening ahead of a trough with cooler and breezier conditions expected Friday and Saturday. Highs on Friday will be anywhere from 10-20 degrees cooler than today, with the coolest day on Saturday where Valley highs may only reach into the 70s. Although humidity values will be increasing with this system, breezy winds may create some fire weather concerns by increasing the risk of any fires spreads, especially for grasses and other fine fuels.
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Chances for showers and isolated storms also begin on Friday beginning in the northern mountains and spreading southeast Friday night. The best chances for scattered precipitation remain in the northern Sacramento Valley, foothills, and mountains. On Saturday, precipitation chances shift north of the Oroville area in the N Sac Valley and surrounding foothills/mountains. This system moves out of the area Saturday night with drier and warmer weather expected on Sunday.
Extended Discussion (Monday through Thursday)
Dry and warmer weather is expected next week.
High temperatures trend about 7 to 10 degrees higher on Monday versus Sunday as upper trough exits eastward, with Valley and Delta highs in the 90s. Ensemble means show nearly zonal flow setting up over Northern California Tuesday as a trough pushing through over the Pacific Northwest flattens the pattern. This should cool temperatures a little, though uncertainty remains with the depth of the trough into NorCal. Will go with NBM, which projects just a few degree drop. Trough axis shifts inland Wednesday. Precipitation is forecast to stay north of the area, with dry airmass over NorCal. Little change is expected Thursday.