Freezing rain will likely start falling in the Medford-Ashland area at 8 p.m., according to the National Weather Service in Medford.
A freezing rain advisory was issued at 2:48 p.m. by the weather service with "moderate confidence," it said.
"The cold air will be in place, but the question is how much precipitation will be produced by the front," the advisory said.
"There is a weak cold front coming through from the west, northwest. It's going to be weak enough that it is not going to scour out the cold air, but just strong enough to produce some drizzle or light freezing rain," said Dan Weygand, meteorologist at the weather service office in Medford. "Even with this very light amount of rain, the fact that it is freezing it will not take much to cause very hazardous conditions."
The Medford weather station is calling for the possibility of about a tenth of an inch of ice to accumulate on exposed surfaces.
The Illinois Valley should get the first dose of freezing rain at 6 p.m., then Grants Pass at 7 p.m., with the Rogue Valley getting hit at 8 p.m., according to the advisory.
Snowfall likely will stay above 4,500 feet, Weygand said, adding "the conditions are likely to be more treacherous in the valley than on Siskiyou Summit."
But a short break in frigid weather is on the way, he said.
"With this front going through we will see some better mixing of air ... we'll finally get some melting of the snow on Friday and Saturday," he said.
Following that lull, cold air will again settle back into Southern Oregon valleys, leaving conditions similar to the last several days, he said. Morning valley fog is expected to persist into Tuesday.
— Sam Wheeler