Snow levels are expected to plunge to as low as 1,500 feet above sea level today as a mix of cold air and precipitation hits the Rogue Valley in the latest December-like storm headed this way.
The National Weather Service has issued a winter storm warning for areas above 2,000 feet and a winter storm watch for lower elevations through today as the front comes in wetter than originally expected.
East Medford developments up the side of Roxy Ann Peak could see an inch of snow today, with about 4 to 7 inches above 2,000 feet, weather service meteorologist Sven Nelaimischkies says.
Future fronts are predicted to be warmer and raise snow levels to as high as 6,000 feet, triggering runoff levels that will swell — but likely not flood — area streams parched by what so far has been a very dry winter.
"With the rain falling on the snow, I'd expect you to see a good amount of runoff," Nelaimischkies says.
The heftier runoff means inflows into a very low Lost Creek Lake will peak Sunday at about 3,600 cubic feet per second, which is about 25 percent higher than Wednesday's forecast.
That has the U.S. Army Corps of Engineers upping its expectation that the lake will rise 4 feet higher next week than originally forecast, says Jim Buck, the Corps' operations manager at Lost Creek Lake. That will put the lake next week at about 16 feet lower than normal for mid-February, Buck says.
The impacts won't be as significant at Applegate Lake, which is 5 feet lower now than it was during the 2001 drought year, Buck says. The peak inflows there are set to climb from 320 cfs to 380 cfs, Buck says.
With the Corps playing catch-up by holding back all but 900 cfs of water flowing into Lost Creek Lake, the upper Rogue River will triple in volume but stay well within its banks, according to National Resources Conservation Service forecasts.
The Rogue at Dodge Bridge, where Highway 234 bisects the river, is forecast to peak at about 3,500 cfs Monday, then taper off but rise to 5,000 cfs by the middle of next week.
Similarly, the flows at Grants Pass are forecast to balloon to 3,650 cfs Monday and then rise again to 6,000 cfs Thursday.
These flows will be the result of a series of fronts moving into the Rogue Valley following a high-pressure wall in the Pacific that has blocked most storms from hitting the region, diverting them north and east, weather experts say.
That wall moved north this past week, allowing storm systems generating in the tropics to move toward Southern Oregon.
These types of storms, which often start with low snow elevations and then see warm rain falling onto the snow, are more common here in December, Nelaimischkies says.
Up to 2 feet of snow has been forecast for mountain areas during this series of storms, which are the first significant ones to reach Southern Oregon this winter. Most of that snow is forecast for above the 5,000-foot elevation level.
Systems that moved further north Thursday were colder and wetter, dumping as much as 7 inches of snow on the Willamette Valley floor, triggering pileups on Interstate 5, shutting down state offices in Eugene and canceling afternoon meetings at the Oregon Legislature.
As many as 25 vehicles collided in clusters in southbound lanes near Albany, the Oregon Department of Transportation said. A detour was then blocked by another crash.
No injuries were immediately reported. National Weather Service forecasters said the storm will be the most widespread snow event in the northern and central Willamette Valley since December 2009.