December 8, 2017 – Little change with dry weather into next week with chilly nights and mild days.
High pressure continues to dominate, bringing dry weather and just some high, thin clouds. The main difference this morning compared to yesterday is winds. Light easterly downslope winds on the east side of the Valley have kept conditions in places like Chico, Oroville, Marysville, and Stockton about 4 to 8 degrees warmer than this time yesterday. The northern Sacramento Valley in contrast is cooler, 18 degrees cooler at Redding. This is due to calm conditions replacing the northerly winds that were there.
The warmest conditions are in the foothills and lower mountains, with 3 am temperatures there in the 50s and even lower 60s. This is due to a strong inversion created by the high pressure system, with a mild ‘thermal belt’ around 2000 to 5000 feet elevation. This inversion layer is also reducing air quality, acting like a lid and preventing mixing. Check Airnow.gov for the latest air quality forecast for your area.
Some mist is again possible this morning, but dense fog is not expected.
Little change in temperatures is expected today into the weekend, with highs around 70 for the northern and central Sacramento Valley and adjacent foothills, mid to upper 60s elsewhere. Slight cooling is possible early next week, as the upper ridge shifts eastward. The potential for precipitation remains near zero.
Extended discussion (Tuesday through Friday)
Models similar in maintaining blocking ridge through late next week. This will continue dry weather with above average daytime temps and cool nights. Some patchy valley fog will continue to be possible nights and mornings. EC brings a short-wave through the ridge next Friday and generates some light precip over the PacNW leaving NorCal dry. GFS maintains ridging through this period. Forecast for now follows persistence with dry weather continuing through the extended forecast period.