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Midsummer-level temperatures across the Southern U.S. this past weekend featured more expansive triple digit heat across the southwest quadrant of the U.S. than models forecast (including central and West Texas). Not only is this early season heat currently expanding north and east to produce multiple days of the hottest temperatures of the year across the Great Lakes and Northeast starting by Tuesday (15°-20° above average), but latest model consensus is significantly slower to spread an unseasonably cold Western airmass east of the Rockies prolonging near record heat (90s) across most of the Northeast though Thursday. Even after a lead weakening cold front passes off the New England by Friday recent modeling indicates brief cooling will fail to reach seasonal levels across the Northeast (still 3°-6° above average) through next weekend (May 25-26). Another less extreme Eastern warm-up  (7°-10° above average) early in the final week of May, while unseasonably cold air of Gulf of Alaska continues to drain through western Canada into the Western U.S. ensures the next week to 10-days will continue to feature severe thunderstorms focusing across the central U.S. along the boundary of sharp west-east temperature contrast. However, all extended range models have latched onto onset of lower amplitude pattern change before May is over, ejecting the final cold Western airmass of the extended series across the central and Eastern U.S. in a progressively weakening form.  As such the 11-15 day period is forecast to be a transitional period of modest Eastern cooling (slightly below average at best) and early stages of progressive warming west of the Rockies. In this more summerlike low amplitude pattern warm air advancing back into the East before the end of the 1^st week of June (16-20 day period) represents start of near coast to coast slightly-moderately above average temperatures and drier conditions on track to predominate June.