From the US National Weather Service
Why the heat?
High pressure ridges cause air to sink. Sinking air compresses and warms. You may see this referred to as a “heat dome.” Warm air aloft also “caps” the atmosphere, helping to suppress thunderstorms.
Pattern Change Late Week:
As the ridge of high pressure shifts east and begins to break down, the “cap” of warm air breaks. All the heat and moisture that have been trapped under the ridge is suddenly available for thunderstorm development.
Severe Weather Potential Friday or Saturday:
“Ridge Rider” thunderstorms can often produce damaging winds. In fact, many warm season derechos form this way. Unfortunately, this pattern is notoriously difficult for weather models to pick up on, so “Ridge Rider” thunderstorms are typically low certainty until the day of. We want to give a heads up now, since we’re heading into a busy holiday weekend. Details to come later this week!
