What You Need to Know About the Impacts of the Rex Blocking Pattern

It has been a largely docile week of weather thus far across most of the U.S. Other than a coastal storm that churned up the seas along parts of the Carolinas and into the mid-Atlantic, conditions have been mostly quiet for the bulk of the country. The volatile weather pattern in the Southeast when compared to the rest of the U.S. is the result of what meteorologists refer to as a Rex blocking pattern. What is this feature and how does it impact the overall weather? Read on for a detailed explanation.

What is a Rex Blocking Pattern?

A Rex blocking pattern is defined as a weather phenomenon when upper-level weather features work to create roadblocks in the atmosphere. More specifically, a "Rex block" is the term used to describe a weather pattern distinguished by an upper-level high-pressure system hovering to the north of a closed low.

It is common for systems packing extratropical moisture to follow behind upper-level wind patterns. These systems generally move to the east throughout much of Canada and into the U.S. However, the upper-level high-pressure systems can also serve as roadblocks to the west-to-east movement.

A Rex block pattern takes on a squiggly shape within the jet stream. The odd shape then stops a large part of the usual forward movement of the low, trapping it over one area for days at a time. The halting pattern can often last longer than a week, impacting the weather for an extended period.

How does the presence of a Rex blocking pattern translate to the actual weather? The answer depends on how much moisture is circulating in the area near the block. For example, the upper-level low-pressure weather systems generate upward vertical motion. This motion will produce significant cloud cover, rain, snow, and thunderstorms when the systems pair with sufficient moisture in the atmosphere. Thus, a low that is stuck will deliver consecutive days of precipitation.

Likewise, upper-level lows that come along with pockets of cold air contribute to long periods of time with atypically cool air that will not budge. This can result in unseasonably cool temperatures and dreary conditions.

How the Rex Blocking Pattern is Impacting the Weather This Week