December 27, 2018 – Mainly dry through end of the week except very isolated mountain showers Today. Chance of light showers northern mountains Sunday. Breezy north wind Today and early next week.
Northern California under northwest flow aloft between high pressure over the eastern Pacific and a low pressure system over the northern Great Basin. Most locations under fair skies this morning but shortwaves dropping down the back side of the low will bring a slight threat of isolated showers over the Sierra Cascade crest. Light northerly wind this morning has kept valley fog to a minimum. Surface high pressure pushing into the Pacific Northwest will bring an increasing northerly gradient today so northerly winds will be on the increase.
As usual, the strongest winds will be along the western side of the Sacramento valley and should see a period of winds this afternoon and early evening just reaching wind advisory criteria there. Lighter but still breezy winds will continue through Friday. Daytime highs under fair skies today and Friday should come in a little above normal for this time of year.
High pressure pushing in over the state will bring warming on Saturday under fair skies. Upper ridge breaks down a bit on Sunday as a Pacific frontal band moves into the Pacific Northwest. Tail end of this system will bring a threat of light showers to the northern mountains Sunday. Precipitation with this system will be light so no major impacts expected but cloud cover will bring a little cooling most locations.
Extended Discussion (Monday through Thursday)
The extended forecast continues to look mainly dry, with forecast high temperatures a little above normal and low temperatures a near to slightly below normal.
Models are in good agreement with the return of upper level ridging with northerly flow on Monday. Breezy northerly winds are expected, especially over the western side of the Sacramento Valley in the afternoon, and a little lighter on Tuesday. This should inhibit cooler morning temperatures and fog. Lighter winds and slightly cooler overnight temperatures are forecast for Wednesday and early Thursday.
A cold front begins to move onto the Pacific Northwest and northwestern California coast late Thursday, bringing slight chances of precipitation there and possibly into the southern Cascades.