Airport seeding covers a smaller land area

Could Jackson County be held liable for vehicle accidents as a result of seeding the fog at the airport?

— Gary E., Medford

The land-based fog seeding program presently in use at the Medford airport has a much smaller footprint than the original airplane-deployed system used for a century.

Still it deposits some really slippery stuff on surrounding roadways. But before you start blaming the airport for the recent "snowfall" that dusted the valley, consider that for most of the week, the airport was not doing any cloud seeding.

Airport Director Bern Case says the Oregon Department of Transportation and the Federal Aviation Administration have both given their clearance to the program and are notified when airport seeding is used.

"The liability for not seeding is much higher than for seeding when you are talking about a safety issue for aircraft," Case said.

Although use of the cable attached system providing effective release, commonly known as CASPER, was put on hold because of unrelated radar difficulties late last week, seeding did take place early Thursday, Case said.

While it has a technical description, in simple terms CASPER is a large balloon that is towed around the airport dispersing the ice pellets.

That in turn freezes the fog, causing it to fall to the ground and opening a hole in the fog to allow planes to land.

Because the pellets are now dispersed only 500 feet above the ground and fog occurs only at times when there is little to no wind, airport officials say not much of the "snow" falls outside the boundary of the airport.

"It really only falls along Vilas Road and little bit of Table Rock Road," Case said. "There is a little drift onto Biddle Road."

On Thursday the roads were icy and surrounding lawns, and trees had a snow-like covering. Most of that at any distance from the airport should be attributed to Mother Nature, rather than CASPER.

Mike Petrucelli, a meteorologist with the National Weather Service said really dense fog can create rime which typically collects on vegetation.

"It's more frequent around river valleys where the cold air flows over the warmer water," he said. "It evaporates and then frozen mist can form. You will see a build up on the tree branches even around here."

While the airport might produce a micro-climate of its own during seeding, there are times when weather happens, surprising forecasters.

Sometime in the past month Case got a call from the Weather Service asking if there was seeding.

"I told them no," Case said. "They hadn't called for snow and got some and they were looking to use us an excuse."

Send questions to "Since You Asked," Mail Tribune Newsroom, P.O. Box 1108, Medford, OR 97501; by fax to 541-776-4376; or by e-mail to youasked@mailtribune.com. We're sorry, but the volume of questions received prevents us from answering all of them.


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