Seasonably cold air and late season snow contracted into the Northeast this past weekend but unseasonably warm air in place across the rest of the Eastern half of the U.S. at the same time is flooding the Northeast today  producing the warmest temperatures yet this year (15° -20° above average). The warmest day of the week in the Northeast is certain to be Tuesday ahead of seasonal level cooling Wednesday.  Despite sharp temperature swings typical of spring across the Midwest, South, and East along with frequently wet conditions (mainly rain), above average temperatures are forecast to predominate this week. However the Western U.S. (and Canada) remain significantly cold and snowy, and by early next weekend (Mar 15) all extended range models begin to spread winter-like cold air east of the Rockies along with potential blizzard conditions across the northern Plains and Upper Midwest. Similar to all significant cold air outbreaks observed east of the Rockies through the preceding winter extended range models appear to be underestimating rate, intensity, and areal extent of additional cold air expansion. However, greatly improved government model consensus exhibiting progressive Eastern U.S. cooling during the 3^rd week of March (while the Western U.S. warms), adds confidence to 30-day MWA ensemble forecasts which establish near sustained winter-like cold (30s) air reinforcement and snow across the northeastern quadrant of the U.S. early in the final week of March through the end of the latest run at the end of the initial week of April. While the seasonal transition underway virtually ensures Eastern U.S. below average temperatures will not reach the same extreme levels observed in winter, prolonged interruption to spring-like warmth is likely to persist even longer across the Northeast into mid or late April, before more sustained warming finally manifests through May.