Wunderground.com - Lee Grenci, 1/23/12
Before I went to bed last evening (January 22), I was checking obs across the country when I startled my wife with a fairly loud "Good grief!" My outburst was prompted by the 00Z temperature and dew-point soundings at Denver's Stapleton Airport (see the 00Z skew-T below). No excuses... I simply lost it when I saw that dew points were literally "off the charts" from roughly 650 mb to 250 mb. As a side note, I confess that it's probably better to use frost points instead of dew points in this context, but old habits are hard to break.
The 00Z temperature (red) and dew-point (green) soundings at Denver's Stapleton Airport on January 23, 2013 (the late afternoon of January 22). note that dew points (frost points) were "off the charts" between roughly 650 mb and 250 mb. Courtesy of UCAR.
With my interest piqued, I started to look more closely at weather observations in the region and found these data at Broomfield, Colorado, which lies just to the north of Denver (map). Scroll down to the 2:47 P.M. observation on January 22. Good grief! A frost point of minus 42 degrees and a temperature of 63 degrees. That's a dew-point depression of 105 degrees! Yep, the relative humidity was a desiccating 1%. Note that the wind was sustained at 33 mph (gusts to 41 mph). No doubt that the westerly wind was downsloping into Broomfield. And the visibility was 70 miles (on a clear, pristine day in the Rockies, you can't see forever). For reference, I include the meteogram from 12Z on the 22nd to 12Z on the 23rd (below) so you can see the trace of relative humidity (focus your attention on the bottom plot of the topmost graph; you can read percentages off the vertical axis on your right).
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