August 26, 2020 – Smoke and haze from wildfires will continue to impact air quality and temperatures over interior Northern California for the next several days. Overall dry weather this week but a few late day storms will be possible over the mountains into mid-week. Slightly above average high temperatures.


Clear skies cover the region early this morning under short-wave ridging. IR difference imagery shows a narrow area of stratus continuing along the coast, but profiler data indicate the marine layer is a little more shallow compared to yesterday (around 1k ft). A moderately strong Delta Breeze continues at Travis AFB. Current temperatures are a little cooler across most of the region compared to 24 hours ago, while RH’s continue to rise in the Delta Breeze influenced areas and are little changed elsewhere.

Another short-wave moves into NorCal today. TPW is forecast to be a little lower than Tuesday afternoon, but still enough for a few late day storms over the higher elevations around the north and east periphery of the forecast area. Temperatures are forecast to be similar to Tuesday as the Delta Breeze continues and areas of smoke and haze affect insolation.

Quieter weather settles in for the rest of the week as weak closed low develops to the southwest of the Bay Area. Initially, this low is expected to entrain drier mid and upper level air from the south which will limit overall deep convection. Temperatures are forecast to trend upward a bit with slight synoptic warming and a decreasing Delta Breeze. Warmest valley temperatures are expected to return to around the century mark, or slightly above.

Extended Discussion (Sunday through Wednesday)

Minor model variations exist with handling of closed upper low off the CA coast over the weekend, and more significantly with short wave trough digging through the PacNW into the Great Basin early next week.

Model consensus exists though with dry weather and above normal temperatures through the extended forecast period. High temperatures in the Delta expected in the low to mid 90s with 90s to around 100 for the Central Valley, hottest in the Northern Sacramento Valley. 80s to low 90s forecast for the mountains and foothills.