Sacramento, California – A prolonged stretch of warm, dry weather is settling in across much of the western United States, and while the sunshine may feel welcome for mid-January, forecasters warn it could come with a downside: worsening air quality and persistent fog, especially in valley locations.
Meteorologists say a strong northward bulge in the jet stream is locking the West into a stagnant pattern that limits storm activity and suppresses wind. With little movement in the atmosphere, pollutants can accumulate near the surface, creating unhealthy conditions for sensitive groups.
Why the Pattern Is Stuck in Place
The current setup is driven by a jet stream positioned far north into southwestern Canada. When this happens, storm systems are forced to take a wide detour well away from the West Coast.
“When storms are diverted this far north, the atmosphere becomes stagnant,” forecasters explained. “That leads to light winds, clear skies, and very little mixing of the air.”
This stagnant setup allows daytime warmth and nighttime cooling to repeat over and over again, reinforcing the pattern rather than breaking it.
Temperatures Running Well Above Normal
Under this configuration, temperatures are expected to climb well above historical averages across much of the region.
Cities such as Seattle, San Francisco, and Salt Lake City are forecast to see highs 5 to 10 degrees above mid-January norms.
Farther south, the warmth becomes even more noticeable:
- Southern California may see highs in the 70s to low 80s,
- Phoenix is expected to reach the upper 70s to near 80 through midweek,
- Las Vegas will hover from the mid-60s into the low 70s.
These readings place some locations 10 to 20 degrees above average, a significant departure for this time of year.
Fog Becomes a Persistent Problem
The same calm, clear conditions that allow temperatures to spike also create ideal circumstances for fog formation, especially in low-lying areas.
In California’s Central Valley, dense Tule fog has already appeared multiple times this winter. One stretch lasted three to four consecutive weeks, severely limiting visibility and keeping daytime temperatures suppressed.
“When fog becomes trapped under high pressure, it can linger well into midday or fail to clear entirely,” meteorologists said.
When that happens, some communities may remain gray and cold all day while surrounding higher elevations bask in sunshine and warmth.
Air Quality Concerns Begin to Build
Perhaps the biggest concern with prolonged stagnation is air quality degradation. With little wind to disperse pollutants, emissions from vehicles, industry, and residential heating can accumulate near the ground.
Important health concern: People with asthma, heart disease, or other respiratory conditions may experience worsening symptoms during stagnant air episodes.
Officials say air quality alerts become more likely when these patterns persist for several days in a row, particularly in urban corridors and agricultural valleys.
When Might Relief Arrive?
Forecast models suggest a possible pattern change by the middle to latter part of next week, when the jet stream may finally dip south again. This would allow storms to approach the West, increasing wind and atmospheric mixing.
While any incoming systems may be weaker than the powerful storms seen in December, even modest changes could help:
- Break up fog layers
- Improve air circulation
- Reduce pollution buildup
Until then, conditions may remain locked in place.
Looking Ahead to February
Longer-range outlooks suggest that February could begin with a similar setup, featuring continued warmth west of the Rockies and limited storm activity.
“If this pattern persists, the West may continue to see dry weather, periodic fog, and recurring air quality concerns into early February,” forecasters noted.
Residents are encouraged to monitor local air quality reports, limit outdoor exertion during poor air days, and use caution when driving in fog-prone areas.
Are you already noticing hazy skies, fog, or warmer-than-normal temperatures where you live? Share what conditions look like in your area in the comments.
