November 14, 2019 – Dry weather pattern continues the remainder of the week with a cooling trend. Warmer this weekend with well above average high temperatures.
Partly to mostly cloudy skies cover the region early this morning as the offshore trough approaches. The marine layer is also deepening ahead of the trough (indicated over 3k ft in depth on the Ft Ord profiler), so may see a bit of stratus make its way inland into the Sacramento area early this morning as surface gradients trend onshore. Current temperatures are mild compared to 24 hours ago (up 5-10 degrees most areas) and range from the mid 30s in the mountain valleys to the 50s across the Central Valley and foothill and mountain thermal belts.
Cooler temperatures (though still around 5-10 degrees above average) along with partly to mostly cloudy skies are expected today and Friday as the trough moves through. May see a better chance of more widespread stratus moving into the Central Valley later tonight into Friday morning as the trough axis nears the coast (HREF probabilities of MVFR ceilings are greater than 90% from about Chico southward in the Sacramento Valley).
Northerly surface gradients will increase following trough passage later Friday into Saturday as the upper ridge quickly rebuilds and the Rex Block redevelops. We`ll likely see some gusts of 20-30 mph by Saturday in the Sacramento Valley and surrounding terrain before winds subside Sunday.
Highs will also warm back into the 70s to lower 80s over the weekend across the Central Valley (10-20 degrees above average) with some daily records in jeopardy.
Extended discussion (Monday through Thursday)
To start the week, the broad upper ridge which had been a fixture over the region for the weekend will exit toward the Intermountain West. A seasonably strong upper low/trough is forecast to approach the Pacific Northwest by early Tuesday which encourages a notable cool off.
Uncertainty remains regarding the evolution of this feature which ultimately dictates the impacts across northern California. The 00Z ECMWF as well as many of its ensemble members attempt to close off an upper low around the California/Nevada border by late Tuesday. Meanwhile, the 06Z GFS/GEFS mean amplify the trough to the east with a solution that is 12 hours quicker. A number of scenarios are possible, some of which could even produce some scattered showers.
At this point the dry forecast appears more likely given how the ensembles are currently shaping up. Given the strength of this amplified trough, a decent north to northeasterly flow event may unfold during the middle of next week. With fuels running historically dry for mid- November, this would prompt a fire weather concern. Details will likely change in the upcoming days so stay tuned to the latest forecasts.
While the week begins warm with Valley high temperatures in the mid/upper 70s, the trough will cool things off by around 5 to 10 degrees. Widespread upper 60s become more commonplace although this actually still runs about 4 to 8 degrees above climatology. Such temperatures are likely to continue throughout much of next week.