While extreme heat shifts northward, another major issue is potential for excessive flooding rainfall across the Interior West and Southwest U.S. including California. An upper trough entraining a tropical cyclone early in the 6-10-day period causes a long duration period of wet weather covering much of the West. Flash flood risk is highest in Southern California, the Southwest Desert, and the Great Basin!

Possibly due to seasonality, a transition toward a climate pattern with greater influence from the tropics, the far Southern U.S. including the Gulf States and particularly Texas are forecast to lose their tendency for extreme heat or produce a choppy not pattern as indicated with the SERC 15-day outlook.

While oceanic El Nino onset was announced by NOAA in June, the atmosphere is lagging with a lingering memory of the 2020-23 lengthy La Nina keeping atmospheric ENSO in neutral phase.

Regions of drier change during the past 3 months outnumber the wetter change by 14-4. One possible explanation is the increased mid-atmospheric high pressure related to large regions of anomalous warm SSTA and causing dry climate.