This phenomenon is NOT unusual, but it doesn’t always happen. Today, the dry line and the resulting squall-line were perfectly aligned. The data presented a teaching moment that I couldn’t pass up. At the end of the animation, I zoom in so you can see the wind barbs pointing toward the dry line. The air is converging and being forced upwards (it can’t go downward).
The upward motion leads to clouds and thunderstorms (if there is sufficient atmospheric moisture and instability). This is a rare opportunity to show how the low-level convergence along a boundary, such as a dry line or a cold front, can lead to precipitation.