June 29, 2018 – Warmer today with hot, dry, and breezy conditions over the weekend. Cooling trend returns early next week.
Red Flag Warning from 11 AM this morning to 5 AM 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.
Discussion (Today through Monday)
Water vapor imagery and model height analysis showed a broad ridge of high pressure over the eastern Pacific with upper level jet flow pushing through northern California. Aside from some high level cloud cover pushing through the Great Basin, quiet weather persisted overnight across the region. Temperatures ranged from the upper 60s to lower 70s for the valley and the low 40s in the Mountains. Ridge of high pressure is expected to shift eastward today, and temperatures will increase as a result to the warm side of average.
Temperatures will continue to increase into the weekend with many locations in the north and central Sacramento valley reaching 100+ degrees, which translates to 5 to 15 degrees above average in the valley. Those that are sensitive to heat should hydrate adequately this weekend, avoid long exposures in the afternoon sun, and dress appropriately while using sunscreen.
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As surface high pressure moves closer to the forecast area, pressure gradient will increase across the Sacramento valley Friday night into Saturday. This will increase wind speeds across the valley and some ridgetops to 35 mph and isolated gusts up to 40 mph. Fire weather concerns will result, and burning is not recommended this weekend.
Temperatures are expected to decrease slightly for the beginning of next week, although afternoon highs will still be on the warm side of normal.
Extended discussion (Tuesday through Friday)
Upper ridge retrogrades westward as an upper trough moves into the Pacific NW. Temperatures on Monday will be still be a few degrees above normal with Valley highs generally in the 90s to lower 100s. A cooling trend will continue throughout the extended period as the upper level trough drops south over NorCal and onshore flow continues. Temperatures look very pleasant for the 4th of July with mid to upper 80s in the valley, 70s and 80s in the foothills and 60s and 70s in the mountains. A strong ridge will start to build in from the east towards the end of the week and that will start to warm temperatures back up.