Fundamental pattern change early this 1^st week of April fully replaces last week’s record heat observed across most of the Western U.S. with well below average temperatures and substantial mountain snow measured in feet. Most of the Eastern half of the U.S. remains predominated by well above average temperatures, with exception of an increasing expanse across the northern tier including the Great Lakes and Northeast where periodic cold Canadian air reinforcement persists prompting NWS Winter Storm Warnings and Advisories in place this past weekend to be extended into this week.  Improved extended range model alignment increases confidence next weekend (Apr 5-6) marks onset of prolonged winter-like cold (and snow) spreading progressively deeper into the Eastern half of the U.S. through midmonth, including double-digit below average temperatures deep into the Southeastern quadrant of the U.S. Since extended range model forecasts only recently latched onto return of winter-like conditions east of the Rockies during the 2^nd week of April, subsequent runs are likely to increase intensity, coverage, and duration of well below average temperatures and very late season snow. Latest 30-day MWA ensemble forecasts prolong winter-level cold air reinforcement deep into the Eastern U.S. into the start of the 3^rd week of April (Apr 13-16) before the next milder pattern shift begins aloft. However late month temperature moderation at the surface is likely to be very slow, especially if snowcover extends deep into the Ohio Valley and mid Atlantic region. All of this ensures April will verify markedly colder than March, potentially within the top-10 coldest on record east of the Rockies.