Days 6-10/11-15 commentary: Intense cold across the Midwest to the Northeast U.S. in the 6-10 day period and a colder trend since late last week. In the 11-15 day period models vary widely. Milder Pacific influence is forecast. The outlook is a consensus between the GFS and ECM ensemble. Macro-scale (climate) support favors a colder solution in the extended-range.
Days 16-20 commentary: Low confidence forecast as models disagree. Warm shift into the East is expected while regenerating cold appears in the Northwest.
Climate factors commentary: Stratospheric warming over northwest North America coupled with a shift of MJO to phase 3 favors re-emerging cold across western North America and warming for eastern North America.
Snow commentary: Snow cover has expanded in recent days and will provide a cold carpet for incoming arctic air this week. The ECM 10-day snowfall forecast indicates more snow for the Northwest and Northeast.