The GFS Ensembles above show the development of intense troughing in the western US, along with high pressure in the East SU US as a byproduct. This comes as the overall pattern in the Pacific also appears to be in line for changes, including the troughing pattern being replaced by a more persistent ridging pattern. Longer range model guidance indicates that this ridging in the pacific will strengthen, but it is possible we see the West US troughing evolve in the waters west of the coast of California. This would be good news for those in the Central and East US who want the cooler fall weather, as offshore troughing could incite ridging in a portion of the Rockies, which could then lead to some cooler weather in the Central and East US. The Central US would be more likely to see this cold weather, as it is possible some slight ridging would appear in the East US. This trend is partially shown in the GFS ensemble temperature departure forecast for 9 days out:
Andrew
