As I mentioned earlier this week, the Arctic Oscillation (AO) will start a transition from its current strong negative phase to a positive phase by the end of next week. During these transitions, precipitation patterns are enhanced.
I mentioned that the upper flow would likely split, with both northerly and southerly branches. It now looks like the flow will be more of a “sloppy” west-to-east pattern than a true split flow. The image below shows the jet stream towards the end of the weekend. Note how the flow is from west to east.
Areas in yellow indicate pockets of upper atmospheric energy. Initially, these pockets were being transported along the southerly branch of the jet stream. Now, models are forecasting them to be ejected northeast into the Midwest rather than moving further eastward.
This will impact precipitation patterns. Without a strong southerly branch, and with energy ejecting northeast, precipitation chances over (eastern portions) of the Southeast U.S. will be significantly reduced. On the other hand, precipitation chances over the Midwest will be enhanced.
I will cover this transition in more detail in my Sunday briefing.