Though last week's forecast for October 16-22 was for above normal temperatures for most of the Lower 48 states, and that appears to be verifying, one thing I noted was that the jet stream pattern still featured a broad trough that would support cooler conditions, but there was no deep cool air available. Looking out to the final full week of October, there still is little change in the jet stream pattern over the contiguous U.S., but a deep storm moving through Alaska is refilling the pool of cold air available, and new cold will surge into Western Canada and the Northern Plains of the United States in response. The farther east one is - including here in New England - the more removed from this shot of cold air, and therefore, the less confidence that the cold will arrive. With a favorable jet stream pattern, however, chances are good a warmer-than-normal start to the period in the Northeast will be offset by a cold frontal passage by mid-week, and cooler than normal air that follows.
As for precipitation, the pattern favors a large anticyclone (high pressure) in the Northern United States to lock in cool and dry air, but probably not until the aforementioned cold frontal passage, which is likely to come with a wave of low pressure attendant to height falls aloft, and enhanced precipitation at the start of the period.
