What is an omega block and how does it impact our weather?

Upper air pressure patterns are the driving force of our weather here at the surface
Published: May. 1, 2023 at 3:45 PM CDT
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NEW ORLEANS (WVUE) - When it comes to forecasting the weather, we always have to keep an eye on the upper atmospheric patterns. They directly impact what can happen to us here on the ground level.

Our upper air pattern this week will become a pattern that nearly stalls which causes the northern polar jet stream to take the shape of the Greek letter omega. This lends to the name, omega blocking pattern. The bottom line, you could experience the same weather for several days in a row due to this stalled out pattern.

This pattern will stall across the country this week.
This pattern will stall across the country this week. (WVUE Fox 8)

In the omega blocking pattern, the low-pressure counterclockwise spin works like an interlocking gear with the high-pressure clockwise spin. Since the pattern stalls, anywhere inside the troughs of low pressure are prone to cool and wet conditions. Places inside the ridge of high pressure will mainly be dry and warm.

The pattern under an omega block
The pattern under an omega block(WVUE Fox 8)

Since high pressure is sandwiched between the jet stream troughs, it promotes slow movement and can sometimes grow the high-pressure ridge northward. This can lead to even warmer air getting brought to higher latitudes as well as well above normal temperatures brought into the southern states.

During this pattern, significant severe weather outbreaks aren’t as likely since the dynamics don’t support low pressure development in the central United States. In fact, these areas are typically dominated by stable air under this particular pattern. However, this week, the subtropical jet stream will lift north and provide enough instability for a severe weather chance by Thursday. This ridge will also bring humidity back to Louisiana.

Severe potential Thursday.
Severe potential Thursday.(WVUE Fox 8)

Spring is on hold for many under the jet stream dips along both coasts. Cold enough air will bring snow to the northeast as well as the higher elevations of California and along the spine of the Rockies.

Snow for the first week of May 2023.
Snow for the first week of May 2023.(WVUE Fox 8)

The omega blocking pattern looks to break down and begin to move on by the second weekend of May.

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