August 3, 2018 – Cooling trend into Sunday then warming well above normal next week, with widespread triple digit highs in the Valley by mid week. Widespread smoke from wildfires will continue.
Red Flag Warning from 11 AM this morning to 11 PM PDT Saturday
Discussion
Upper level ridging over the region has flattened with a shortwave passing through the Pacific Northwest. Current temperatures are generally a few degrees cooler than this time yesterday. Satellite infrared imagery shows the Ranch Fire portion of the Mendocino Complex has been very active overnight, with gusty north west winds. Heat signatures were most intense in the late evening and have gradually decreased through the early morning hours. The Carr Fire has also shown hot spot overnight, with gusty northwesterly winds. A Red Flag Warning continues in that area through Saturday evening.
Weak disturbances move through today with a stronger shortwave on Saturday. No precipitation is expected, but winds over higher terrain and through canyons are expected to increase further, especially afternoons and evenings.
Due to this, low humidity and dry fuels Red Flag Warnings take effect across the northern Coastal Range, portions of Shasta County and the Sierra.
The Delta breeze has been bringing come cooler air into influenced areas. The breeze is beginning to weaken this morning, though. High temperatures in the Delta and nearby areas may warm a little over yesterday, while the rest of the forecast area should see a little cooling. Slightly above normal high temperatures are expected this afternoon. Saturday will be a little cooler, with Sunday 5 degrees below normal by Sunday.
Wildfire smoke will continue to be an issue, though the Delta breeze may bring some clearer air at times to locations near the Delta.
Extended discussion (Tuesday through Friday)
Dry weather with a warming trend will continue into the middle of next week as the upper ridge amplifies into the Great Basin. Current model guidance puts temperatures within a few degrees of the century mark on Tuesday across the Valley, and above 100 degrees Wednesday through next Friday.