Many are sick of hearing me talk about the Mexican bubble heat ridge, which is an important feature in setting up surges of hot air into Texas, and warmer values east of the Rocky Mountains. If I had top point toward one system, or at least a favored location for same, it would be the Gulf of Alaska Low. The subtropical low organizing over the Bahamas will not alter the 500MB flow, and its importance will be as a heavy rainmaker for much of the Interstate 95 corridor during the next 4 to 5 days.
A succession of cold disturbances from the northeastern Pacific Basin will dig through the Intermountain Region, ultimately flattening the persistent subtropical high. But the process takes time, and likely will not be complete until the second week of October. The impact of so many impulses with energy and cooler height profiles will blast out the ridging. Some thunderstorms may develop and move southeastward from the High Plains. But the character of the semizonal flow is mostly dry, and better chances for rainfall will not occur without a southern branch jet stream, which is what the CFS and ECMWF series suggest will take shape in two or three weeks.
To reiterate, we are still a long way from seeing any truly cold air in either Canada or the lower 48 states.