Remember its all about whats going on in the upper atmosphere in the jet stream. The jet stream drives our weather patterns and separates warm and cold air. Many things can influence the jet stream pattern including typhoon activity over east Asia. It's widely discussed that a typhoon that skirts by Japan and recurves out to sea has a big impact on the jet stream pattern in the 6-10 day period. Basically because a strong storm like a typhoon amplifies the wavelengths in the pattern having a down stream effect on our area.
Let take a look at whats going on..
Two areas of focus on the image above. First notice the first green area of low pressure on the bottom left. That is a typhoon that is forecasted to recurve along the arrow I drew by the end of this week. This COULD have an impact on our areas weather (or a little more to the west) 6-10 days later which is around the 20th of the month. In fact the jet is not as strong this time of year so if the colder weather was centered more to our west that is not necessarily a bad thing if you want hints of a cold stormy winter.
Now also take a look at the big storm just south of the Bering Sea on the upper right of the image. That also can have a significant impact on our pattern but not until the last few days of Oct. Bottom line: there is evidence in the pacific by two very significant systems that the pattern over the eastern part of the country could lock into a more consistent stormy pattern by the end of this month.
What do the models say. In short the GFS and Canadian do not show the trough over the east around the 20th, but the European is the outlier and does based on its run last night..
Notice the big trough south of Alaska, which causes a downstream ridge over the west which has a trough over our area. This is what those two storms systems could do in the longer term. Again this would mean a chilly end to October relative to averages and the potential for a storm or two (no not snow).
Lets see how this evolves. Don't forget the Winter 2015 outlook is out on October 15th. Spread the word!