Dry and slightly breezy start to the week

November 22, 2021 – Dry weather is expected for the upcoming week. Expect patchy Valley fog over the next few mornings. A weak weather system will bring a cooling trend and renewed chance of northerly winds by Tuesday or Wednesday.

Discussion

GOES-West nighttime fog product shows areas of fog beginning to develop in portions of the Central Valley this early Monday morning. As of midnight, visibilities had already dropped to a quarter-mile or less in the northern San Joaquin Valley at Stockton and Modesto. As a result, have issued a Dense Fog Advisory for the northern San Joaquin Valley through 10 AM PST. Think the main short-term forecast challenge will be how far north the dense fog will extend; can’t rule out the potential for patchy dense fog into the Sacramento Metro Area. Will keep a close eye on satellite fog product and surface visibility observations, and — if necessary — extend the areal coverage of the Dense Fog Advisory.

Expect another afternoon with quiet weather across interior NorCal today as high pressure maintains its influence over the region. Highs will generally be a degree or two cooler compared to Sunday as the ridge axis shifts southeast. Still, look for highs to be in the middle 60s to near 70 for Valley communities, or about 2 to 7 deg F above late November normals.

Upper level trough will approach the Pacific Northwest on Tuesday, and will introduce precipitation chances to far northwestern California. Unfortunately it appears most of — if not all — the Sacramento Valley, southern Cascades, and northern Sierra will remain dry. The best precipitation potential that the National Blend of Models is presently advertising in our area is a 10 to 15% chance for far northern Shasta County. In the wake of this trough, expect winds to return offshore with locally gusty winds Tuesday night and Wednesday for portions of the Sacramento Valley, southern Cascades, and northern Sierra.

Upper level ridge in the eastern Pacific will build east toward the Golden State for Thanksgiving Day, resulting in continued dry conditions for NorCal. As with any upper level ridge this time of year, will have to monitor for the potential for morning fog development.

Extended Discussion (Friday through Monday)

Ensemble guidance maintains the upper level ridge over the northern half of California from Friday through the weekend. This would promote near to slightly above normal temperatures for interior NorCal with reoccurring fog morning fog potential in the fog-prone areas of the Valley. Probability of Sacramento receiving measurable rain (>= 0.01″) for the weekend and into early next week remains at/below 5 percent each day.