It is September and we are heading into the months of transition from summer to winter. Of course fall (autumnal equinox) doesn’t arrive until September 22, 2020, but we are going to start seeing the cold air machine start up in Canada very soon.
With the production of cold air comes the periodic blasts of cooler temperatures that punch southward into the lower 48.
The leading edge of these chunks of cold air are called cold fronts. This edition of Weather 101 will focus on what they are and how they affect us here in Northwest Arkansas and the River Valley.
What is a Cold Front?
A front is simply the leading edge of an air mass. In this case, a cold front is the leading edge of a cold air mass. They are often depicted on a weather chart as a line with blue triangles pointing towards the relatively “warmer” air mass.
What Weather Can You Expect When a Cold Front Moves in?
The skies often turn stormy when a cold front approaches, but do you know why?
Cold fronts typically form storms by creating lift. Cold air is much more dense than warm air, and acts as a shovel that scoops the warmer, less dense, air up over the wedge of cold air.
As the warmer air is lifted, it cools to the dew point forming clouds and rain. If the lift is strong enough, and the atmosphere is unstable storms can be possible.
Behind the cold front temperatures are much cooler as the dense air mass oozes into our region through the higher terrain of the Boston and Ouachita Mountians. Most of the time, the cold air is very shallow by the time it reaches the Ozark Plateau, and struggles to push across out area. This can lead to drastic changes in the forecast based on where the front stalls out.
Through the spring and summer months, we often see severe weather initiate along these cold fronts. The line of storms then march into our area, often overnight, bringing heavy rain, damaging wind, hail, and even isolated tornadoes.
In the winter, higher elevations such as Boone and Newton counties can see snow while Fayetteville or Rogers sees a cold rain or ice.
As we progress through the next few months, be on the lookout for these cold fronts to headline our weather as the hours of daylight dwindle!