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June 30, 2018 – Hot, dry, and breezy conditions over the weekend. Cooling trend returns early next week.
Mainly clear skies prevail across interior Northern California as a strong upper ridge over the east-central Pacific builds into the region. Northerly winds are bringing subsidence across the forecast area, and much of the northern and central CA coast is stratus-free as a result. Northerly pressure gradients have been increasing during these overnight hours, and local gusts of 30-35 mph have been reported along some of the more wind-prone areas of the Coastal Range and Sierra. Temperatures across the forecast area are generally running much warmer than 24 hours ago.
Hot, dry, and breezy weather is expected across the forecast area today under a weather pattern not dissimilar to what we saw last weekend. Valley high temperatures of 100-108 degrees are expected today, with 80s and 90s over the mountains. 925mb winds suggest that we could see wind gusts in the 25-35 mph range in the Sacramento Valley, strongest along the north and west side.
A few gusts to 40 mph will be possible over Lake County and favorably- oriented Sierra canyons this morning, and again Sunday morning.
The combination of hot temperatures, gusty north winds, and low humidity will lead to critical fire weather conditions this weekend. Any activity that could spark a fire is strongly discouraged.
The aforementioned upper ridge will begin to retrograde westward on Sunday, and continue to do so Monday into Tuesday as a trough pattern develops over the Pacific Northwest. This will promote a strengthening Delta Breeze and eventually some synoptic cooling. Only areas adjacent to the Delta will see this cooling initially on Sunday, where the northern Sacramento Valley likely will remain hot. Temperatures will likely remain a bit above normal into Monday, then cool to near normal levels on Tuesday.
Extended discussion (Wednesday through Saturday)
Dry southwest flow aloft is expected through the latter half of next week as NorCal will be between a trough over the eastern Pacific and strong high pressure across the Desert Southwest. Temperatures will be below average at mid-week warming to around average next weekend. Locally breezy southwest winds expected at times, especially over the mountains and near the Delta.
Red Flag Warning until 5 AM PDT Sunday for Carquinez Strait and Delta-Central Sacramento Valley in Glenn, Colusa, Yuba, Northern Sutter, and Butte County Below 1000 Ft-Eastern Mendocino NF-Lake County Portion of Lake-Napa-Sonoma Unit-Northern Motherlode From 1000 to 3000 Ft. Includes portions of Nevada-Yuba-Placer-Amador and ElDorado Units-Northern Sacramento Valley to Southern Tehama County Line Below 1000 Ft-Northern Sierra Foothills from 1000 to 3000 Ft. Includes portions of Shasta-Trinity and Butte Units- Southeast Edge Shasta-Trinity NF and Western Portions of Tehama- Glenn Unit-Southern Motherlode From 1000 to 3000 Ft. Includes portions of Calaveras-Tuolumne Unit-Southern Sacramento Valley in Yolo-Sacramento Far Western Placer, southern Sutter and Solano County Below 1000 Ft.