In the Northern Hemisphere the reason that cold fronts are often
preceded by rain and cloudy weather
which quickly clears to reveal bright,
clear skies and sunshine, accompanied
by colder temperatures is primarily
due to the fact that-
A low pressure systems that push
cold air south often accumulate
unstable moisture in front of them.
B high pressure systems that push
cold air south often accumulate
unstable moisture in front of them.
C water cannot evaporate in very
cold air, so rain storms cannot
develop behind cold fronts.
D winds only blow on higher
temperature days.