December 27, 2017 – Dry weather this week with above normal temperatures. Next chance of precipitation early next week.
High pressure ridging over the west coast will bring dry conditions through the short term period. Daytime highs today through Saturday are forecast to range from 5 to 10 degrees above normal. A series of shortwave troughs are forecast to ride over the ridge through the Pacific Northwest over the next several days. This will bring variable high cloudiness but any precipitation should remain well north of the forecast area. This cloudiness will not be thick enough to preclude night and morning fog completely so expect patchy valley fog each night mainly from about Marysville southward. Light north winds should reduce the threat of overnight fog farther north.
Light northerly winds will be predominant most areas during the daytime but lack of upper level support will allow decoupling many areas during the nighttime hours. Light overnight winds will allow for cool overnight lows with minimum temperature readings expected to come in a little below normal.
Extended discussion (Sunday through Wednesday)
Latest model guidance maintains an upper level ridge anchored overhead through at least early next week. This will bring generally dry conditions across interior NorCal through Tuesday. Models continue to struggle by the middle of next week regarding an upper wave that might break down the ridge. The latest 00z ECMWF output, which arrived late this morning, is similar to the somewhat consistent GFS, and keeps the forecast area dry until early Wednesday. Meanwhile, the GFS brings precipitation generally over the mountains on Thursday, but coverage is not as widespread as the ECMWF. Thus, significant model differences are leading to a rather low confidence and the morning package remains largely unchanged. Stay tuned for updates.