The obvious answer to that question is, above the clouds. This weekend, high pressure will settle over Central Texas at the surface. That means the sun should be shinning right? Well, yes for most of North Texas, this will be a bright and sunny weekend, but from the Brazos Valley to the south, its going to be cloudy.
Lets show you the set up. The following image displays the wind direction at the surface, or the ground:
Albeit light, but the wind is flowing from the north at the surface. Therefore, the air close to the ground will be cold. In the last blog, we indicated that colder air is denser and heavier than its counterpart, warm air. Due to this difference in density, any warm air that tries to come in will not have the ability to push away the denser cold air. The only way around the cold air is to flow above it.
In the mid-levels of the atmosphere, (850-700mb level, for the weather savvy), the wind its actually coming from a different direction.
The wind about 5,000ft above the surface is coming from the southwest. One, the air coming from this direction is warmer. Plus, the origin is from the Pacific Ocean. Therefore, the air is warmer and has more moisture than the colder, drier air at the surface.
During a set up like this, the warm, moist air will rise above the colder air. When air lifts, it tends to get cooler and the water vapor will condense into liquid droplets. In other words, clouds will form. This process is called overrunning.
Since the air is not being lifted at a rapid rate, there will not be any rainfall in our scenario. However, there are overrunning events that occur quite frequently ahead of a warm front. In the winter, overrunning can cause major ice storms and even significant snowfall.
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