Chilly curtains of Rogue Valley fog could loiter in the area until early next week, the National Weather Service says.
With that comes visibility of a quarter-mile or less, stagnant air and some light ice slicks on the roads. Exactly when the ground clouds will start to push on is anyone's best guess.
"That's the question of the month," says meteorologist Brian Nieuwenhuis.
The weather service extended its freezing fog advisory through 10 a.m. Tuesday. A low-pressure system is expected to come through the area Wednesday, which could result in some thinning, but not enough to push out the stagnant air completely.
"Most likely (it) will not be strong enough to clear us out. That will not happen," Nieuwenhuis said, adding the diluted fog will likely thicken back up after the system passes. "It's very uncertain as to when and where (the system) will go, but if it tracks over us, we might break out for a day or two."
The lingering inversion will limit mixing of the air, trapping pollutants. Medford has endured a six-day streak of "moderate" pollution levels, according to Oregon Department of Environmental Quality data. Weather officials encouraged anyone with sensitive respiratory conditions like asthma to limit outdoor activity.
But the gray won't last forever. The air could see a permanent shift back to normal starting next week.
"The long term models, and we're talking like the end of the month, do show a pattern shift," Nieuwenhuis said, adding that shift could bring some much-needed precipitation to the area. "They change a lot, so that remains to be seen, but there is hope."
— Ryan Pfeil