As the #CaldorFire moves further east towards the high country, it will begin to hit areas affected by the large blowdown event this last winter. This is what we often describe as interacting forest disturbances, and it can result in unexpected fire behavior. 1/8 
A very strong east wind event hammered much of the Sierra on January 18-19th, knocking down thousands of large, otherwise healthy green trees. While east wind events are not uncommon in the Sierra (and can fuel fires in the autumn), this was particularly bad timing. 2/8
After a hot, dry summer and prolonged fall drought stressed the trees (and their root systems), the Sierra finally needed some much needed precipitation. At higher elevations, this fell as heavy snow across much of December and early January. So the tree crowns were loaded. 3/8
When the winds hit, the giants (holding the most snow) were particularly vulnerable. Most of the media attention was on Yosemite NP, where hundreds of trees and several giant sequoias fell, and a substantial amount of damage closed key sections of the park. 4/8
But trees fell up and down the high Sierra, including on the Eldorado NF, and the Caples/Silver Fork area just east of the current #CaldorFire perimeter was particularly hard hit. 5/8 fs.usda.gov/Internet/FSE_D…
After a very dry and hot spring and summer, these downed trees have cured out and are ready to burn. They will produce substantial heat as they combust, and in areas where many fell across each other like pick-up-sticks, they will create a problematic "jackpot" of fuel. 6/8
The challenges here are many: they are dangerous for firefighters (hung up limbs and trees are called "widow-makers" for a reason), spots start easily bc there is thick slash around them, and the logs are so big, water and retardant are less effective. 7/8
As the #CaldorFire hits such areas, you may see more energy in the smoke plume, and there may be some difficult spot fires. It's a great example of an extra degree of difficulty in trying to fight these fires, due to interacting ecological disturbances. 8/8 Photos: CJ Hampton
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