In the wake of cold Canadian air diving deep into the Eastern U.S. during the past weekend (16°- 20° below average in the Northeast), along with several inches of snow observed as far south as northern New Jersey and Pennsylvania , slightly above average temperatures peaking across the Northeast Monday (mid 60s) are certain to remain brief.  The next surge of unseasonably cold air 10°-15° below average (and northern snow) is certain to flood the Midwest Tuesday and the East by early Wednesday. In volatile spring fashion noticeable warming is forecast across the Eastern U.S. late workweek, which all extended range models follow with another multiday period of well below average temperatures focusing into the Great Lakes and Northeast next weekend (Apr 19-20). Recent model forecasts limit southern penetration of this latter unseasonably cold airmass sparing the Southeast from significant cooling. This is part of milder model shifts across the Eastern U.S. in late month forecasts directly related to colder pattern change across the West; abruptly reversing well above average heat persisting across the Southwest through midweek (mid 90s in Phoenix), with 10°-15° below average temperatures by early next weekend (Apr 19). Because colder Western conditions are driven by difficult to resolve cutoff low development, subsequent runs are likely to change. However, the general pattern shift to moderate Western trough / Eastern ridge flow by next weekend (Apr 19-20) is also quite wet across much of the central and Eastern U.S. including Midwestern areas still saturated from several consecutive days heavy rainfall earlier this month. Soil saturation limits magnitude of otherwise warming Eastern temperatures not only through May, but also into the start of summer potentially precluding significant or prolonged well above average heat. In contrast Western precipitation is unlikely to reverse expansive drought in place from Southern California to central Texas where greatest magnitude and most sustained above average temperatures are forecast.