Differences in the upstream pattern over Alaska is resulting in differences in how cold the U.S. gets during the latter half of January*.

GEFS is stronger with the ridge over Alaska compared to ECMWF, forcing more of a classic -NAO (colder) pattern over North America. pic.twitter.com/oKmp6Gy90f

— Mike Ventrice (@MJVentrice) January 9, 2021