Per MDA met this morning:
"1-5 and 11-15 Day Similarities/Differences
After a warm 6-10 Day period, the forecast reverts back to a colder regime in the 11-15 Day. The overall pattern themes echo some similar themes to that of the near-term, particularly in the eastern Pacific as the EPO heads back into its negative phase after a brief sojourn to the positive side in the 6-10 Day, resulting in a strong upper-level ridge building over western Canada and Alaska while troughing deepens downstream across the eastern half. While the general pattern shape is very similar, there are some notable differences in the details that preclude the period from resembling a carbon copy of the 1-5 Day. The western ridge is shifted further west in the 11-15 Day than the 1-5 Day, which results in a colder outcome across the Rockies compared to the very warm 1-5 Day. However, it is worth noting that the Euro and especially the GFS had the ridge being too far west ten days ago when today’s 1-5 Day period was 11-15 Days out, and as a result, the GFS in particular was far too cold in the West and Plains. Meanwhile, both ensembles (but especially the GFS) show some ridging over the Southwestern Atlantic during the 11-15 Day, which aims to prevent cold from reaching as far south as in the 1-5 Day period."
For those fearing the dreaded SE ridge, this observation by this MDA met is encouraging in that it suggests an eastward shift of the western US ridge/eastern US trough couplet will verify vs what the recent GEFS runs have been showing for the 11-15. If this E shift for the current 11-15 were to verify similarly to what is happening in the current 1-5, that would mean that the GEFS SE ridge is a fake.