Cold Canadian air more typical of mid-winter than mid-spring surge deep into the Plains and Midwest to start this week. Models spread this unseasonably cold airmass (~20° below average) to the East Coast Tuesday limiting high temperatures across the majority of the Great Lakes and Northeast to winter-like 30s for about 2-days (40s in NYC), which will feel even colder in high winds. Light snow recently observed as far south as southern New Mexico and portions of West Texas is considered indication light snow coverage across low elevations of the Northeast early-md this week will also exceed model forecasts, albeit significant accumulation (3-6 inches) will likely be confined to higher elevations. Winter-like conditions are near certain to noticeably moderate by Thursday, Apr 10 but longer range model forecasts changed the greatest by aligning several degrees cooler (and wetter) across the Midwest and East through the latter half of the week into the 3^rd week of March. Cooler Eastern U.S. model shifts are direct response to stronger Southwestern ridge forecasts peaking temperatures at record levels for multiple days late this week (Apr 10-12) including triple digit highs in Phoenix , followed by only limited moderation maintaining well above average temperatures (mainly 90s). Broadening Southwestern ridging extending into the central U.S. teleconnects to lower downstream heights prolonging periodic seasonably cool air outbreaks into the Great Lakes and Northeast the longest into late April, followed by seasonal level warming at best into early May according to well aligned CFSv2 model and 30-day MWA ensemble forecasts.