August 20, 2018 – Gradual cooling with dry conditions expected through the week. Areas of smoke and haze will continue, especially near wildfires.
Discussion
Mainly clear skies, except for a few high clouds, across the area early this morning. Current temperatures are similar to 24 hours ago and range from the mid 40s in the colder mountain valleys to the lower 70s across the milder portions of the Central Valley. Upper trough settles over the region early this week resulting in gradual cooling into mid-week.
It appears precipitation chances will remain north of the forecast area, though some smoke improvement will be possible early this week with increased southwesterly winds and a little better mixing. Trough weakens later in the week allowing temperatures to warm slightly.
Extended discussion (Friday through Monday)
Weak upper troughing along the west coast will keep daytime temperatures around to slightly below normal Friday through the weekend. Stable southwest to west flow aloft will keep any afternoon mountain thunderstorm threat out of the forecast during this time. GFS and ECMWF now both show an upper low digging in over the Pacific Northwest on Monday. This upper low digs deep enough into NorCal to warrant some slight shower possibility over the northern mountains. If this forecast scenario holds, most areas will see a significant cooling on Monday with daytime highs dropping to as much as 10 degrees below normal.