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Clear the air: 'It's fogging hard' instead of raining

The last day of November felt like a month's worth of fog settled over the Medford airport.

At the end of one of the foggiest Novembers in recent memory, Horizon Air had to cancel nine flights into or out of Medford. Air traffic returned to normal by mid-day Monday as a weak weather system approached Southern Oregon. Forecasters were predicting rain Monday night and showers early today, but fog was expected to roll back into the valley later in the day and persist through the weekend.

The culprit? Uncooperative high-altitude winds that are carrying the rain we expect in November into the Midwest. Without the winds to scour the valley, cold air collects and fog accumulates.

"If it's not raining hard in November and December, it's fogging hard," said Ryan Sandler, a meteorologist at the National Weather Service office in Medford.

Sandler said the weather service extended its air stagnation advisory in Southern Oregon through the remainder of the week because no major storm systems are approaching the region.

Above the fog, sunshine made for a delightful day to end the Thanksgiving holiday. Crater Lake National Park had a sunny 56 degrees, while the temperature climbed only to 41 degrees in foggy Medford.

Airport director Bern Case said flights into and out of Medford are susceptible to weather-induced delays and cancellations because the nearby mountains require pilots to have more visibility than they need in flat terrain. The Federal Aviation Administration's regulations require aircraft to have 1,300 feet of visibility here, but in Eugene and other areas where the terrain is more accommodating, aircraft can land with as little as 600 feet of visibility.

Case said it would be difficult to say whether fog later in the week would create problems for air travelers. Temperatures have to be in the upper 20-degree range to use cloud seeding to clear the fog.

November started cool and wet, but turned foggy and dry after Veterans Day. The 2.29 inches of rain that fell during the month was .64 inches below the November average of 2.93 inches, and nearly all the rain fell within the first 11 days of the month — there was just .17 inches of rain after Veterans Day.

The below-average rain for November increased Medford's rain deficit for the year. By the end of the month, Medford's total precipitation since Jan. 1, 2008 was just 10.88 inches, 4.59 inches below the normal average.

Sandler said it's still to early to talk about drought in Southern Oregon, but the region will need ample rainfall in December, and snow in the mountains, to provide water for irrigation and to maintain stream flows next summer. Historically, November and December are the region's wettest months, and once they're gone, there's relatively little time to build snowpack.

The scarcity of snow is obvious to anyone traveling south on Interstate 5 between Grants Pass and Medford — when the fog lifts enough to see that Mount McLoughlin is brown instead of white. Even Crater Lake National Park had just 3 inches of snow on the ground at park headquarters Monday, a mere 9 percent of the average Dec. 1 snowpack of 33 inches. The Mount Ashland ski area, where the average opening day has been Dec. 10 over 40-plus years, has no snow.

Sandler said it's impossible to predict when the jet stream will return to its normal winter path, bringing rain and snow to Southern Oregon.

"Who knows why the jet stream is where it is?" he said, but that could change as suddenly as the shift after Veterans Day turned November foggy and gray.

"We could go right to a wet pattern and get a fresh storm every three or four days," he said.

Reach reporter Bill Kettler at 776-4492 or e-mail:bkettler@mailtribune.com