PDX says it's ready for the potential storm on Thursday. The airport has already de-iced its runways and taxiways. And crews are on standby.
The big cause of delays during snowy weather: de-icing the planes. Each plane has to be meticulously sprayed with de-icing fluid, to clean its wings and control surfaces. So if it does snow, expect an extra 15 to 30 minutes per plane to get it done.
PDX has travel tips on its website at http://www.flypdx.com/Travel_InclementWthr.aspx.
So far... none of the airlines that serve PDX are offering to allow changes to tickets. That likely won't happen until snow starts falling. I'll post updates if the airlines change their policies.
As always, it's likely the hardest part of flying out of PDX in snow, will be getting there.