Weather and Sky Gallery :: Winter Line of small cumulus along the Denver Convergence-Vorticity Zone (DCVZ) in winter. Freezing fog seen from the summit of Flagstaff Mtn in Boulder, Colorado. Freezing fog seen from the summit of Flagstaff Mtn in Boulder, Colorado. Heavy rime on grasses after a freezing fog event in Boulder, Colorado. Heavy rime on trees after a freezing fog event in Boulder, Colorado. --- --- Return to The Weather Gallery index page.