Cooler temps, a cold front, icy clouds up high, and ideal conditions for contrails.
Someone was headed almost due west, past the sun and off over the Pacific. Dallas to Honolulu? Who knows. Something like that.
Upon closer examination, there’s a bit of iridescence in the high clouds of ice, a bit of rainbow coloring just above the center of the photo.
And just to the right of the tree, no doubt headed into BUR Rwy 8, is a Southwest 737.
That’s a really sweet shade of blue, isn’t it?