August 21, 2018 – Gradual cooling with dry conditions expected through the week. Areas of smoke and haze will continue, especially near wildfires.


Some stratus did develop early this morning and banked up on the E side of the Sac Vly. The marine layer deepened to 3+ kft which is usually a good indicator of at least having some stratus advect or develop in the Vly, especially if onshore momentum continues during the night as it did in this case. The low of 56 this morning at DTS was the coolest overnite low since July 5th (and yes, some may consider that an “unimpressive stat of the day”). Main wx message will be an extended cooler wx pattern, even through the 6-10 day period, as upper level troughing prevails over the region. The wx pattern looks dry for interior NorCal as precip remains outside of our CWA.

Even with today’s trof, the air mass is too dry for convection in our CWA, and the higher resolution models this morning eliminate precip chances in our area. Some locally gusty winds expected with the trof passage today, and again Fri and into the weekend with successive trof passages. Mainly clear skies across interior NorCal early this morning. A few high clouds are arcing across central California as the upper trough slowly drops southward. Satellite imagery shows a more extensive marine layer extending further inland, and with profiler data indicating a depth around 2500 ft and stronger onshore gradients, there will be potential for morning stratus across the Sacramento region.

The cooling trend will continue through mid-week with the passing trough before temperatures level off late in the week. Dry weather is expected to continue, however, some of the higher resolution models continue to suggest a slight chance of thunderstorms late this afternoon near Mt Lassen as the upper trough swings through.

Some improvement in smoky conditions away from the fires is expected over NorCal (given current status of wildfires) this week as upper level troughing over the region suppresses stagnant high pressure over the Southwest.

Extended Discussion (Saturday through Tuesday)

Weak troughiness remains along the West Coast through the weekend and into early next week keeping temperatures slightly below average.