Why are they stopping before dark??
I don't understand this "plan" at all.
They are stopping contra-flow soon enough to assure that incoming roads are clear for when rescue crews have to get IN.
It'll take several hours to stop contra-flow and clear the roads. IF they get it done in time then the weather will be too bad to do it later.
After they get the roads clear then IF they can stay, they'll have to maintain the roads' navigability.