I found this along the trail a few days after a windstorm. It made me think about the different times I have seen branches break due to mycellial growth, such us whenever there is snowmelt and then a freeze; when there is several days of rain and when the is a day or two of rain followed by a windstorm. I notice that the branches that come down are more often covered in fungus and lichen and when I pick them up (as was the case with this one) they are heavier and feel denser than branches without fungus. I suspect that the mycellium has filled the branch with even more water than a branch without mycellium and that the amount of water in combination with the rotting of the wood cells helps the breaking process along.