The school calendar says it's spring break, but an unusually cold storm system for late March could bring snow to Southern Oregon today.

The school calendar says it's spring break, but an unusually cold storm system for late March could bring snow to Southern Oregon today.

The National Weather Service has issued a snow advisory that will be in effect from 2 a.m. until 11 p.m.

The advisory, along with a hazardous weather outlook and a special weather statement, warn that waves of cold air from the Gulf of Alaska are headed toward Oregon.

The first batch of low pressure and freezing temperatures was expected to hit Jackson County Tuesday night, the weather forecast said.

Snow levels were predicted to drop to between 2,000 and 2,500 feet overnight, with mountain locations above 2,500 feet waking up to as much as 2 inches of snow this morning. Higher terrain, such as the Kalmiopsis Wilderness, was predicted to get up to 5 inches.

Spring has warmed the ground at lower elevations, so an inch or less of snow was expected down to about 2,000 feet.

"The ground is warming, so it won't stick," said Mike O'Brien, meteorologist at the weather service's Medford office.

After a brief break late this morning, another icy blast is expected to hit this afternoon and evening, possibly pushing the snow level as low as 1,000 feet briefly, the forecast said. A slushy accumulation is possible down to about 1,500 feet. Significant accumulation will be above 2,500 feet, where 1 to 4 inches could stack up, the snow advisory said.

The Siskiyous could get 3 to 5 inches of snow and the Cascades could see 5 to 10 inches.

O'Brien doesn't expect to see much snow on the ground in the Rogue Valley, but some flakes will fall.

"The temperature dips to near freezing every night, so it doesn't take much more," he said.

He noted that the gray, rainy weather of the past week has brought new snow daily to Crater Lake, which is expected to get light snow this morning and up to 8 inches tonight.

The weather service warned that the cold front could cause road conditions to deteriorate rapidly in the mountains, so drivers should stay informed and be ready for changing conditions.

For travelers headed north, the Cascades could get up to 8 inches in Lane County and other northern Oregon locations, where snow is expected to continue through Thursday morning, the weather service advisories for that region said.

To the south, a snow advisory will be in effect this afternoon and evening in Etna and Fort Jones, Calif., where up to 7 inches of snow is expected.

Oregon Department of Transportation spokesman Gary Leaming said that spring break travelers often have warm-weather pursuits on their minds and aren't prepared for sudden wintry weather, even when they should be. He advised people to keep winter gear in their vehicles, but said the department won't extend the deadline for studded tires. They must be removed after Monday, March 31.

Showers, mostly rain, will continue Thursday, the forecast said. Another cold front will approach Friday morning, bringing rain to the valley, snow to the mountain and winds. Snow levels will fall quickly behind the front, dipping to 2,500 feet by Friday evening, but the fast-moving system isn't expected to deliver significant amounts of precipitation.

Reach reporter Anita Burke at 776-4485 or at aburke@mailtribune.com