It's hard not to get excited about the first major cold surge of the season after the blistering heat we've suffered through the last several weeks. Mother Nature is going to make us suffer this weekend, but MAJOR change is coming by Tuesday.
The loop below shows the GFS forecast 500-mb heights (black lines) and 925-mb temperatures (colored lines) from 1200 UTC (0600 MDT) this morning through 1200 UTC (0600 MDT) Tuesday. There are two major large-scale circulation changes that occur at upper levels. First, the ridge from hell that has dominated our weather for so long weakens and shifts upstream. Second, the upper-level pattern becomes much more strongly amplified, meaning that the ridges and troughs get stronger, resulting in a more wave like pattern, which by Tuesday morning features a high-amplitude ridge over the northeast Pacific and a deep trough digging into the Rocky Mountain region.