November 24, 2020 – Light showers possible over the mountains tonight and Wednesday, otherwise dry weather expected into next week. Mild days and cool nights will continue with breezy north to east winds today and again Thursday.
IR difference imagery shows clear skies across interior NorCal early this morning. North and east surface pressure gradients have tightened overnight, and light northerly flow has developed through much of the Sacramento Valley resulting in lower RH’s. Further south, winds are generally light and surface conditions are nearing saturation, so some patchy fog will be possible once again around sunrise for areas to the south of Sacramento.
Upper level ridging quickly transits the region today. Locally breezy north to east winds will peak this morning before subsiding during the afternoon. Strongest winds will be along the western edge of the Sacramento Valley and across some of the wind prone locales over the foothills. 20-30 mph breezes will be possible with locally higher gusts. Highs today will be unseasonably mild, around 5-10 degrees above average.
Another weather system is slated to move through NorCal late tonight through Wednesday. The mountains and foothills will see some light precipitation (generally under a quarter inch), but a few sprinkles cannot be ruled out elsewhere. An inch or two of snowfall accumulation will be possible across the peaks of the northern Sierra and southern Cascade Range. Highs on Wednesday will be around 10-15 degrees cooler in the mountains, and about 5 degrees cooler across the Central Valley, compared to today.
As the upper trough moves southeast through Nevada and southern California, ridging begins to build over the area Thursday. Surface pressure gradients are expected to tighten once again, this time a bit more than today. This will cause another round of breezy north to east winds with gusts up to 25-35 mph, locally higher. Temperatures will rebound a few degrees. Less wind returns Friday as gradients weaken, and milder temperatures are expected across most of the area.
Extended discussion (Saturday through Tuesday)
Upper ridging progged over NorCal this weekend resulting in dry weather with above normal high temperatures. Frontal system moves into the PacNW Monday, but enough ridging remains over NorCal to keep the associated precipitation north of the CWA. EPAC upper ridging rebuilds and shifts inland Tuesday.