October 26, 2018 – Warm and dry conditions for the remainder of the week, then cooler early next week with breezy north winds.
Discussion
Clear skies cover interior NorCal early this morning other than a few high clouds spilling over the eastern Pacific ridge. Current temperatures are a little milder across most of the area and range from the upper 20s in the colder mountain valleys to the 50s to lower 60s across the Central Valley. Strong ridging will continue dry weather with warm days and cool nights across the region today and Saturday. The ridge will weaken Sunday as a trough pushes across the PacNW dragging a cold front into far northern California. The system will bring a few showers to the far northern portion of the forecast area, but cooler temperatures and locally breezy conditions are expected to be the main effect from the system. Tightening northerly surface pressure gradients on the backside of the exiting trough will lead to breezy north winds across the region on Monday.
Extended Discussion (Tuesday through Friday)
Upper level ridge will begin amplifying over the eastern Pacific and west coast on Tuesday pushing any precipitation chances north of the forecast area. The breezy northerly winds which were forecast to begin on Monday will continue through the day on Tuesday thanks to surface and supporting upper level pressure gradients.
These north winds will bring lowering RH values on Tuesday both morning and afternoon hours bringing elevated fire weather conditions. A warming airmass will bring daytime highs back up to above normal for this time of year.
High pressure pushes inland on Wednesday bringing still warmer temperatures and slightly lower RH. Winds should be on a slow decline however as pressure gradients over NorCal relax.
Upper ridge axis forecast to center over the west coast by Friday so should see a little more warming both Thursday and Friday. Relatively low daytime RH values will continue with breezy but lighter winds under the increased ridging.