|ECMWF 8-10 500mb height anomaly forecast|
If these forecasts of a horseshoe-style high pressure arrangement actually happen, there is only one option for the polar vortex (a semi-permanent low pressure system over the Arctic, the base of the Arctic Oscillation): It must be forced south into North America. If the polar vortex is forced south into North America, severe cold could flood the region.
The 12z GFS ensembles show their variance as well in the long range, suggesting that the AO will remain negative, but at a moderate negative stance and not as strongly negative as we have seen in recent weeks.
If the polar vortex does indeed come into North America, the US and Canada will be visited by many more instances of cold and snow, especially if that horseshoe blocking pattern does not dissipate for an extended period of time.