Suspended particles in the air can absorb VHF energy, will affect UHF
signals, and will absolutely swallow gigahertz and light wave energy
(which is why you can't see through haze) - now whether ash
particulates from a forest fire will bother VHF is something I'm not
ready to take a position on... But, if there are boron molecules in
that haze from the firefighting chemicals that raises the probability
that it is affecting VHF, and up in frequency...
If the erratic VOR signals that day were due to the forest fire, what
is also likely is that the rising heat from the fires is causing
temperature layering and air turbulence which definitely bends VHF
signals, the same as it distorts light waves when looking down a
highway on a hot day, or looking through a bonfire...

denny