Above normal temperatures and dry weather today. A pattern change this week will bring much cooler weather, breezy winds, and precipitation chances mainly Tuesday through Thursday.
Discussion
Mostly clear skies are being observed on infrared satellite imagery across interior northern California early this morning. Dry weather, sunny skies, and above normal temperatures are in the forecast for Sunday, as a brief period of weak ridging will bring increasing heights over the area. Warmest temperatures will be in the northern Sacramento Valley, where low to mid 80s are forecast for the daytime high temperature today.
After Sunday, ensemble guidance is in solid agreement for an approaching upper level trough to bring a significant cooling trend to the area. Temperatures will be well below average by the middle of the week, as highlighted by the ECMWF Extreme Forecast Index (EFI).
In addition to the cooler temperatures, breezy onshore winds are expected ahead of the passage of this trough, particularly impacting the ridgetops of the Sierra Nevada south of Interstate-80 where gusts 45 to 55 mph are possible Monday night through Tuesday evening.
Widespread rain and mountain snow chances return with this system starting late Monday night in the northern Sacramento Valley and surrounding terrain, spreading southeastward across NorCal through Wednesday. Snow levels on Tuesday will be around 6500 ft, and will continue to lower through the day down to 3500 to 4500 ft as colder air moves into the area. Travel impacts could still be possible over the mountain passes Tuesday into Wednesday.
Extended Discussion (Thursday through Sunday)
Clusters and ensembles indicate NorCal likely to be on the backside of the trough as it moves through the southwest late in the week, then ridging builds in for next weekend (though deeper moisture moving over the ridge may bring some light precipitation to far northern California Sunday).
A few showers may linger over the northern Sierra Thursday, otherwise breezy north to east wind will be possible as surface pressure gradient tightens.
Cold temperatures (in the 30s) will be possible for wind-sheltered portions of the Central Valley Thursday and Friday mornings. Temperatures will moderate next weekend with less wind.