As spring gives way to summer, the weather along Colorado's Front Range enters a predictable pattern. Daytime heating on the Piedmont causes warm air to rise along the mountain slopes and, by late morning, clouds boil up above the Continental Divide. Some of these will become thunderstorms and, as their tops enter the upper atmosphere, high level westerlies push them to the east. Dropping isolated sheets of rain along the way, they merge into monstrous thunderheads on the eastern plains of Colorado, often producing large hail and tornados.
As they move across the urban corridor, the thundershowers reward some neighborhoods with heavy downpours while leaving most high and dry. When showers are light, the thin, dry air of the Piedmont often causes the rain to evaporate before it hits the ground; called virga, such aborted showers are a common sight during the summer months. By evening, the skies are clearing along the foot of the mountains and Front Range residents are treated to dramatic lightening shows to the east. As the sun sets behind the mountains, the thin air and clear skies cause rapid "radiant cooling" and, reinforced by the drainage of cool air from the highlands, overnight temperatures usually fall into the fifties.
This pattern of hot, sunny days, hit and miss showers and cool, dry evenings will continue until the monsoons of August bring in clouds and moisture from the Southwest. Not a bad place to spend the summer!
