How The Omega Block Helped Bring Days Of Rain To Southeast

Time to pull out your Greek alphabet for the ongoing weather.

The pattern that is in place, dubbed an "Omega block," continues to make for slow-moving weather systems and unexpected temperatures.

So, what exactly is it?

An Omega Block, Explained

Meteorologists aren’t the most creative when it comes to naming things, and this blocking pattern is a prime example.

It gets the name "Omega block" because when you trace the jet stream from west to east while this pattern is in place, you will see the Greek letter omega (Ω). 

This setup blocks the typical east-west flow of the jet stream, like a large rock in a small stream that forces the flow of water around it, as senior meteorologist Jonathan Erdman describes it.

As a result, weather systems will move more slowly for several days, leading to day after day of similar conditions across the country.

The two things we typically watch out for during this pattern are potential flooding and an upside-down temperature pattern. 

Let’s break down who is seeing what.

Flood Threat

To the west and east of the Omega block, we typically see low-pressure systems get stuck, causing days of unsettled, rainy weather.

This is the case across the South this week, where several days of rain and storms continue to lead to flash flooding, especially in areas hard-hit by drought.

By the end of the weekend, some spots in the region could see another 1-2 inches of rain on top of what they've already seen.

Cities like Birmingham, Atlanta, Tampa, Orlando and Tallahassee should be on alert.

Upside-Down Temperatures

The other signature impact of an Omega block on weather is the upside-down temperature pattern.

The northern half of the block typically sees dry conditions and above-average warmth.

This pattern continues to play out nicely with parts of the Northern Plains and upper Midwest forecast to see temperatures stay warm, while the Southwest and East stay cooler.

This pattern will untangle itself over the weekend.

Caitlin Kaiser graduated from the Georgia Institute of Technology with both an undergraduate and graduate degree in Earth and Atmospheric Sciences before starting her career as a digital meteorologist with weather.com.