The above image shows probability forecasts for temperatures in the Day 6-Day 10 range. As the legend at the bottom of the image shows, reds define above normal temperatures, while blues indicate below normal temperatures. The darkness of the blues in the Great Lakes show just how intense this season's first real Arctic blast may be, with the probability of below normal temperatures now well above 90%. Considering this forecast is for a 6-10 day period, that's high confidence.
Temperature anomalies can also help decipher height anomalies, like high and low pressure. In the areas we see reds, above normal temperatures are found, meaning high pressure should also be found. This is reasonable, considering we need high pressure in the West in order to create low pressure and cold conditions in the East.