Omega Block Setting Up

So what is this "Omega Block" that is being discussed among meteorologists this week? Well, in its simplest terms, it is a pattern that features an upper-level pattern that looks like the Greek letter omega: Ω. If you look at the map to the left, you can see that overall shape setting up with two dips in the jet stream surrounding the ridge of high pressure that is developing over the Great Lakes, Midwest, and Plains. The reason why it is referred to as a block is because the high pressure system is going to anchor itself over the Great Lakes and not move much for the next week or so. That set up is "blocking" those low pressure systems -- or dips in the jet stream -- from moving.

In other words, with this pattern, the areas under the influence of the dome of high pressure see sunny skies and warmer temperatures for a longer duration of time. Meanwhile, the locations contained within those jet stream dips tend to see cooler-than-average temperatures and an increased risk for precipitation. You can see these patterns clearly on the GFS temperature forecast for this weekend -- the blue shades representing colder air and the yellow shades representing warmer temperatures.

So the next time a meteorologist mentions an "Omega Block" pattern, you will know that wherever the omega/high pressure is located is where warmer temperatures can be expected.