Looks like two different questions Mike. For historical climatic patterns the National Weather Service and NOAA maintain a tremendous amount of data going back to recorded time (weatherwise anyway). I don't have a site marked but search for NWS or NOAA weather data.
For jet stream information, if I read your question right, I'd stick with Weather.com or Intellicast where the pro meteorologists have used the jet stream info along with everything else to do the local forecasts. I doubt any of us can do as well as them, in spite of what we may say about their forecast reliability /forums/images/graemlins/smile.gif