Weekend Weather Blog: The infamous ‘Omega Block’

TWIN FALLS, Idaho (KMVT/KSVT) — This summer is off to a very different start compared to last summer. In fact, on this day a year ago, temperatures soared into the middle 90s here in Twin Falls. Lower elevations saw the upper 90s. Today, we’re sitting comfortably in the upper 60s and lower 70s as I’m writing this.

Why are we seeing this? A special type of pattern overhead is the main culprit - the Omega Block. Like a lot of things in weather and meteorology as a whole, this has to do with the jet stream setup.

The above picture is a hand analysis of the higher-up portion of the atmosphere. This shows us where the jet stream is. Notice the two distinct dips in the jet stream - one to the east and another just to our west. There’s also something you should notice in the center of the country: the big crest in the jet stream.

What does this all mean? Where the jet stream dips, cooler air sits. Where the jet stream crests, warm air is your bet. With southern Idaho in a transition zone, we’re experiencing some mild conditions for our area.

Why is this called a block though? This is a type of pattern that doesn’t like to move. Notice how long the wave is - the crest takes up areas from the eastern Rockies all the way to portions of the Ozarks and Mississippi River. When waves are this long, they don’t like to move.

Without going into too much detail, the movement of these waves is driven by differences in rotation in the atmosphere. When these waves cover a lot of area, their movement of them is more so driven by rotation caused by the earth’s curvature than spin from other effects, like an area of low pressure.

The spin from the earth’s curvature is stronger where the earth curves more - near the poles. With that, crests in the jet stream will move toward weaker spin, whereas dips in the jet stream will move toward areas of stronger spin.

This creates a situation where the pattern itself will begin to move to the west, as opposed to the east. What does this mean? Heat is (eventually) going to make its way to southern Idaho. Tune into my forecast tonight to find out when.