A major storm system threatens the town of Limon, CO. The rain and hail dropped down like a curtain just behind the storm front. The curtain hit within a minute of taking this shot. This type of storm is known as a bow echo. The thunderstorms tend to spread out into long comma-shaped lines as they roll out from the Mountains over the plains. This one formed a funnel cloud over Denver around 3 PM and set off the tornado warning sirens.