Around 6:15 I noticed on radar that a pretty healthy thunderstorm was moving from the SSW to the NNE, directly toward Wolf Creek Pass. Since it had been visually evident with other showers and thunderstorms earlier in the day that the precipitation type was snow down to 9 or 10K feet, I figured that if I drove up into the pass, I would have a good chance of getting some thundersnow. It was a pretty sure bet I could intecept the cell, so if it was still producing lightning I would get thundersnow.
As I drove toward the pass from Pagosa Springs, the storm looked pretty heavy with occasional cloud-to-ground (CG) lightning bolts visible. In fact, the NWS issued a significant weather advisory at 6:25 for a strong thunderstorm over eastern Archuleta County, although I did not realize it at the time. By the time I reached Treasure Falls, where the road begins to climb seriously, some partially melted snow or graupel was mixing in with the rain, with occasional flashes of lightning. I continued driving most of the way to the top until I was in all frozen precipitation - mostly graupel (snow pellets) at first, then gradually changing to all ordinary snow. Over the course of 15 minutes or so I observed three lightning-thunder sequences, but messed up the video on the first two. But not on the third one, as can be seen in the video above!
I remained there for another fifteen or twenty minutes after the lightning-thunder sequence in the video, as the snow increased somewhat and around a quarter inch accumulated on my car. This, of course, was in addition to the light coating of fresh snow that had already fallen when I got there. But no more lightning after that, so I decided to call it a night and head down to town before dark.
Unfortunately the Wolf Creek weather station is down at present, so I do not know how much snow they got. Snowtel data from nearby indicate a few tenths of an inch water equivalent, so perhaps 2-4 inches total from this weather system, which continued to produce snow off and on in the mountains (and rain in the valleys) through the night. Interestingly, the Wolf Creek snowtel indicates 14.5 inches of moisture still present in snow on the ground near the top of the pass, quite a bit for this late in the season. However, this storm was just the latest of a series over the past ten days or so - with the result that the snow cover and especially the snow water content has actually increased in the highest levels of the San Juans since the first of May.
This thundersnow storm was not quite as impressive as the one I witnessed at Ski Santa Fe on March 19 (see previous post in this section), but this time I had a better camera so the video that I did get is better.