August 25, 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.
Short-wave moving into NorCal early this morning continues to generate lift out ahead of it resulting in an arc of mid and high clouds that extend from east of Sacramento up into northeast California. Thunderstorms are well to the north and east of the region.
IR difference imagery shows stratus along the coast of the Bay Area, and coastal profiler data indicate the marine layer has deepened to around 1-1.5k ft. The coast to valley surface pressure gradient has tightened slightly resulting in a stronger Delta Breeze, but its effects are mainly limited to areas to the southwest of Sacramento.
Isolated late day thunderstorms will be possible today and Wednesday across the northern Coast Range, southern Cascade Range, and along the crest of the northern Sierra. Any thunderstorms that do develop are expected to produce little to no rain and potentially gusty winds.
Drier airmass forecast to settle over the region after mid-week despite weak trough lingering off the coast. This will diminish the threat for thunderstorms.
Smoke from wildfires will continue to have a major impact on air quality across the region and you can expect this to continue for at least the next several days. It will also have some impacts on high temperature forecasts and will make it a challenge. Overall we will see above average highs, but where smoke it dense you can expect temperatures to be held down a few degrees.
Extended Discussion (Saturday through Tuesday)
Model variations exist with handling of closed upper low off the CA coast over the weekend, and short wave trough digging through the PacNW into the Great Basin early next week. Model consensus though with dry weather and above normal temperatures expected through the extended forecast period. High temperatures in the Delta expected in the low to mid 90s with 90s to around 102 for the Central Valley, hottest in the Northern Sacramento Valley. 80s to low 90s forecast for the mountains and foothills.