Recently, I was asked why local meteorologists often create different forecasts than national meteorologists. While there are several possible reasons, one I know from personal experience is that the local guys have a better understanding of the lay of the land – literally.
Every region has its own unique variables that play into the weather, and some are more obvious than others. The Great Lakes, the Atlantic Ocean, the Rocky Mountains, and the deserts in the Southwest are all example of geographic features that affect the weather in big ways for the people living near them.
In North Carolina, our most obvious features are the Appalachian Mountains and the Atlantic Ocean. However, there is a smaller feature that can play a big role during our spring and summer months: it’s called the “Piedmont trough,” and it was first named and described in a research article by Steve Koch and Charles Ray published in 1997.
The Piedmont trough is such a player in our weather that when it is present in combination with moisture and other storm ingredients, the likelihood of showers and storms in the vicinity increases greatly. It occurs roughly along the I-95 corridor where the Piedmont meets the coastal plain. In that region, the soil is sandier and heats more quickly on sunny days than nearby soil, resulting in a very localized low pressure zone as the warmed surface air rises.
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This week, the Piedmont trough is affecting our forecast as we’ll have a chance for storms every day, even after the stationary front draped across the state moves away.
By the way, I was asked earlier today why the showers and storms that are popping are not really going anywhere fast, and there is a simple explanation: no mechanism is in place to steer them. The stationary front is by definition not moving, and the wind speed is minimal.