The prevailing winds are to the south from the Lava Fire generally speaking

Even though it winds are going to go all sorts of directions during the days and nights like up mountain canyons during the days and down mountain canyons and valleys during the night still the prevailing winds in the Mt. Shasta and Weed area are blowing towards the south so this means the fire will tend to head south. 

I have looked at this fire on a fire map and it is presently to the East of Weed on Highway 97 and possibly now to the South of Weed a little. So, if it came to Mt. Shasta area it would likely burn between the mountain of Mt. Shasta and Black Butte which is a cinder cone that stands alone to the west and a little north of Mt. Shasta that you can see driving north or south on Interstate 5.

So, the likelihood is that if the fire burns on the prevailing winds it would enter the Mt. Shasta area between Black Butte and Mt. Shasta which also means the fire could also head up the mountain to tree line which also would be very hard to fight because the mountain makes it's own wind currents and would be very dangerous for planes especially and in some situations helicopters as well. Planes usually give Mt. Shasta a lot of distance because local pilots know about all the unexpected wind currents around a mountain that big so giving a mountain like that distance is how pilots survive it. 

So, if you have property anywhere between Black Butte and Mt. Shasta you might want to check to see if you are in the way of the fire and either remove anything you don't want to lose (like your bodies and prize possessions or other things like that before it gets too dangerous to do that safely.