Red Flag Warning until Saturday night

August 9, 2018 – Near to slightly above normal temperatures through the forecast period. Onshore flow increases Friday into the weekend with locally breezy wind at times. Smoke from wildfires will continue to impact air quality.

Red Flag Warning from 2 PM this afternoon to 11 PM Saturday.

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Discussion

Strong upper high centered over NV extends westward over NorCal. Moderate Delta breeze overnight has decreased this morning and expected to remain below 15 mph today.

Smoke from wildfires will continue to impact air quality and high temperatures. Max readings this afternoon forecast to be upwards of 5 degrees above normal, highest in the Northern Sacramento Valley where triple digit heat is expected.

Upper low off the PacNW coast will approach tonight and Friday resulting in increased onshore flow and some minor synoptic cooling. Delta breeze strengthens tomorrow afternoon along with wind through the Coastal mountains, impacting wildfires in that area.

Gusty southwest wind can also be expected over the higher elevations of Western Plumas and the Sierra Nevada with local gusts up to 30 mph Friday afternoon into evening. Upper low tracks inland over the PacNW this weekend helping to moderate temperatures and continue increased onshore flow. High temperatures remain near to slightly above normal through Sunday.

Monsoonal moisture may spread into extreme southern portions of our Sierra Nevada zone Sunday leading to a slight chance of an afternoon thunderstorm over higher terrain, south of Highway 50.

Extended discussion (Monday through Thursday)

Ridge of high pressure will gradually build into NorCal through the forecast period. Daytime temperatures expected to be near or slightly above seasonal normals, with Valley highs in the 90s and 70s to mid 90s over the foothills and mountains. Onshore flow will keep overnight lows generally in the low to mid 60s across the Valley.

Slight chance of an isolated afternoon thunderstorm over extreme southern portions of our Sierra Nevada forecast area Monday into Wednesday as moisture surges from the south. However, best chances look to remain south and east of the CWA. Otherwise, dry conditions expected across the region.