December starts with quiet weather pattern in Northern California; valley fog, air quality issues linger
After a busy November, the start of December has been the complete opposite. Foggy mornings, sunny skies, and seasonable temperatures have dominated the forecast and will continue to do so until we see a pattern change.
Afternoon highs reach for the 60s on Tuesday with a few San Joaquin Valley spots in the upper 60s. Temperatures are slightly above average and will stay similar for the rest of the week.
Will it rain again soon in California?
A large area of high pressure has built in, keeping Northern California out of a storm track for the next week.
High pressure is known for creating stable, warm, and dry conditions. With little to no wind to move around the air above, expect more mornings with patchy to dense fog across the Valley as it traps moisture near the ground.
Dense Fog Advisories return
We have already seen several mornings of fog in the Sacramento and San Joaquin Valleys. A Dense Fog Advisory was issued for the Central Valley on Tuesday as visibility lowered.
Fog typically develops late in the evening between 9 p.m. and midnight and lingers through the early afternoon.
Expect fog to reduce visibility during your morning commutes through the rest of the week. Some areas could see visibility lowered to a 1/4 of a mile or less.
If you encounter fog, be sure to slow down and use low-beam headlights on your car.
Cold weather air quality issues
This high-pressure system is also known for trapping air near the surface, which can lead to poor air quality.
Most of the Valley was placed in the "moderate" category for air quality on Tuesday, thanks to our quiet pattern and lack of any wind.
With this pattern, what develops is something called an inversion or a layer of warm air above cooler air near the ground. This is common in the winter in the Valley because the air near the ground cools more quickly than air above.
Calm winds, clear skies, and long nights prevent air at higher altitudes from mixing with air closer to the ground acting as a "lid" and keeping pollutants trapped in the valley for longer periods of time.
Many do like to use their wood-burning fireplaces and furnaces this time of the year to stay warm, but those pollutants can get trapped in the air underneath patterns like the one we are under.
Sacramento Metropolitan Air Quality Management District has issued no burn restrictions for county residents through Wednesday to help make an improvement. They say it's important to check before you burn.
If you're sensitive to the air quality it's important to check before you go outside and limit your time outdoors during the evening and early morning hours. Once the sun comes up, the air rises and lifts some of the pollution away from the ground.
Is this typical weather for the season?
With no big changes on the horizon through this week and early next week, highs will continue to stay comfortable.
The Valley and Delta will manage to stay in the 60s through the rest of the week. Foothill locations will remain in the 50s and 60s through the weekend.
Temperatures above 60 are considered above average and seasonable for December.
It is likely this quiet and seasonable trend will continue through the first two weeks of the month. The long-range forecast is looking mild and quiet, too, for most of the West Coast.
Our next chance of rain is not to arrive until after Dec. 13.
Make sure to stay with the CBS Sacramento First Alert Weather team as we keep an eye on any incoming storm systems this month.
