October 12, 2018 – Dry through next week under strong high pressure over the west coast. Warming trend today into Saturday, then continued near to slightly above normal temperatures next week. Locally breezy north to east wind through the weekend with lowering humidity and increasing fire weather concerns.
Northern California under northeast flow aloft between high pressure over the eastern Pacific and Pacific Northwest and a low now off the southern California coast. Upper low will continue southward today as high pressure amplifies and shifts inland. This high pressure ridging will bring dry conditions over the forecast area into early next week. Overall airmass warms today bringing daytime highs from a little below normal Thursday to a few to several degrees above normal today.
Warming temperatures and light northerly winds will bring lowering RH values this afternoon. Surface high pressure pushes into the Pacific Northwest tonight establishing a northerly surface gradient. Light northerly winds and warming airmass will bring more drying Saturday afternoon. Northerly surface gradient increases Saturday night and combined with upper north flow will bring still breezier north winds.
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The strongest winds will be over the Sierra Cascade range, coast range and west side of the Sacramento valley where only poor to fair humidity recovery is expected. Combination of breezy north winds and low humidity Sunday will bring increased fire danger. Although daytime temperatures may cool slightly Sunday, they should still come in a little above normal. Warm and dry conditions continue on Monday under upper high pressure ridging. Winds should be on the decrease by afternoon as surface gradients relax.
Extended Discussion (Tuesday through Friday)
Interior NorCal will remain under the influence of an upper ridge, resulting in dry conditions and daytime highs 3-7 degrees above seasonal normals. Little change expected in high temperatures, with Valley highs in the 80s, and 60s to 70s over the foothills/mountains. Locally gusty north to east wind possible at times with lowering humidity.