November 20, 2020 – Dry weather thru the weekend. Mild days and cool nights expected with areas of morning frost across the Central Valley.
Discussion
Other than some high clouds spilling into mainly the southern portion of the forecast area, skies are clear early this morning. Light north to northeast flow has persisted overnight through much of the Sacramento and northern San Joaquin Valleys leading to considerably lower RH’s compared to 24 hours ago, so no fog expected this morning. May see some areas of patchy frost in wind- sheltered areas along the eastern edge of the valley.
Weak ridging builds over the area through the weekend resulting in dry weather with mild days, cool nights and persistent light to moderate north to northeast surface winds. Patchy morning frost will be possible each morning, especially for wind-sheltered areas along the east side of the valley.
A weak system moves through the ridge Sunday night into Monday and may bring some light precipitation to the northern mountains and northern Sierra Nevada, and the increased cloud cover will lead to slightly milder overnight temperatures.
Extended discussion (Tuesday through Friday)
Upper level ridge will quickly build over the West Coast on Tuesday, promoting dry conditions across northern California. By Tuesday night/Wednesday, a trough will approach the Pacific Northwest and clip far northern California with slight precipitation chances. The 00Z ECMWF brings this light precipitation to the far northern Sacramento Valley as well as the northern Sierra Nevada. The GFS is the drier solution, confining the rain/snow to Oregon and far northwest California.
The ECMWF keeps light precipitation chances over northern and central California on Thanksgiving day while the GFS keeps us dry. Either way you look at it, impactful precipitation amounts do not appear likely around the holiday based on the present guidance.