In my experience flash freeze occurs more often when antecedent ground conditions are primed. Meaning some deep cold in the ground before the rain allows for quicker refreeze. Last year we had a flash freeze when 33 degree rain ended as low 20 degree air took over, the dewpoint crashed but winds lagged. I was driving Tues night with temps in the 20s after our rain , roads were just wet, I kept tapping my breaks to see if the sheen was ice, it wasnt, the antecedent ground conditions kept the water from freezing despite what I would think were ideal conditions. Despite low temps low dews and wet roads nothing froze, on my return trip the road was dry. Lots to consider