Pictured above is the 500 millibar height anomalies from forecast Day 6 to Day 10. Cold colors show low pressure anomalies, while warm colors portray high pressure. In the forecast image above, we see strong low pressure building over the Arctic to allow for a strengthening polar vortex. As a result of this strengthening, warm weather is typically favored. However, high pressure building south of Greenland and in the Northeast Pacific will coerce the low pressure further south and allow cold air to make itself available in all the areas shown in blue. Again, usually, warm air would be favored as the cold air would be kept up north in the presence of such strong low pressure over the Arctic. However, the angling of those two previously mentioned high pressure systems will let the polar vortex squeeze some of that unseasonably colder air further south.