Freezing rain and snow caused slippery roadways in upper elevations Sunday, contributing to a series of non-injury spinouts on icy stretches of Interstate 5.

Freezing rain and snow caused slippery roadways in upper elevations Sunday, contributing to a series of non-injury spinouts on icy stretches of Interstate 5.

Northbound I-5 travelers over the Siskiyous experienced brief delays as those lanes near milepost 7 were temporarily blocked late Sunday afternoon due to a jack-knifed commercial semitrailer. No injuries were reported.

A winter weather advisory will go in effect this afternoon and on through the evening, according to reports from the National Weather Service.

Snow showers and a low of around 34 degrees were expected in Ashland Sunday evening, with a total night-time snow accumulation of 1 to 2 inches possible. The chance of snow showers mixed with rain continues throughout today with snow levels predicted to rise to 2,200 feet and highs near 41 degrees, said Mike O'Brien, meteorologist with the Medford office of the National Weather Service.

Rain continued to fall with snow levels dropping to 1,700 feet in Medford on Sunday with nighttime lows predicted for around 34 degrees, and little or no snow accumulation expected, he said.

O'Brien said this week's forecast is tricky due to unpredictable changes in cloud cover.

"It's all dependent on the cloud cover," he said. "There is liable to be a large error factor with the temperatures."

Forecast lows are in the 20s for Medford. But clearing skies combined with the cold air mass may cause temperatures to plummet into the teens in several areas of the Rogue Valley Tuesday night and early Wednesday morning, he said.

"If the skies clear, we can expect quite cold temperatures by Wednesday morning," he said.

Residents and businesses should begin preparations for cold weather now by protecting pipes and draining irrigation systems. Plants in protected areas such as porches and barns will be endangered by the extreme cold, so additional protection may be necessary, the advisory states.

If the cloud cover remains, expect possible rain and fog on the valley floor, and snow in the higher elevations, during the morning and evening hours through Wednesday, he said.

"Basically it's winter. It's November," he said.

Reach reporter Sanne Specht at 541-776-4497 or e-mail sspecht@mailtribune.com.