Will the fog leave Sacramento before Christmas? Here’s what meteorologists say
The Sacramento area may get a white Christmas this year, but not the kind Bing Crosby sang about.
Area meteorologists are unsure if this year’s thick radiation fog — known regionally as tule fog — will disperse in time for the holidays, thanks to persistent weather patterns keeping the cloud layer firmly over the region.
How did the tule fog form in Sacramento?
Jan Null, a former National Weather Service forecaster in Northern California and current professor of meteorology at San Jose State University, said Sacramento’s early fall weather patterns caused a perfect storm for a particularly heavy fog year.
“The perfect recipe for radiation fog ... is for there to be low-level moisture, clear skies and light winds,” Null said. “Right after it quit raining (in late November), we had high pressure build over us and that’s when we got all three of those ingredients.”
Between September and November, Sacramento had 5.08 inches of rain, according to National Weather Service data. More than 3 inches of that rain fell in November alone. That’s the city’s rainiest month since November 2012, when the Sacramento saw nearly 4 inches of precipitation in November.
Once the rain ended on Nov. 21, temperatures began to sharply drop — reaching highs of 40s and 50s after the first half of the month lingered in the 60s and 70s, National Weather Service data shows.
As temperatures in the foothills remained in the mid-50s and low 60s at the close of November, the resulting weather inversion locked in the moisture and chilly low-altitude air, resulting in the characteristic fog.
When will Sacramento get clear skies again?
According to Null, a weather system with significant temperature mixing to cool down higher elevations and warm up lower elevations is necessary to “break the inversion.”
Dakari Anderson, a meteorologist with the Sacramento National Weather Service office, said there may be a weather system arriving around Dec. 17, but it is unclear whether it will bring enough precipitation to clear the fog.
Anderson said temperatures around the Sacramento area will remain in the upper 40s and low 50s while the fog layer is still in place, as the cold temperatures swirl between the freezing clouds and the ground.
Areas above the fog in the Sierra Nevada foothills and higher elevations are forecast to experience higher temperatures, with the possibility of seasonal record highs, ranging from the mid-50s to upper 60s, according to NWS forecasts.
“It could go through Christmas right now,” Null said. “We’ll have to keep on watching it.”
