Euro drops in a deep trough and closes it off over the 4 corners, thus the extreme change in temperature. A bit extreme even for there in early Sept. though. I will go out on a limb- it won't go from mid 90s to 30s for highs in one day lol. Definitely looks like a major shift in the h5 pattern, but probably more like highs in the 50s, maybe 40s for a few days in Denver itself.