March 8-9 Winter Storm, including Thundersnow
Pagosa Springs, CO

by John Farley

As low pressure approached the Four Corners region from southern California, I was hopeful that the combination of a strong moisture surge and cold upper air would generate an opportunity to observe thundersnow. Indeed, thundersnow was in the forecast for much of nothern Arizona and New Mexico and Colorado, and in many areas, that forecast verified. On Friday, March 8, a few snow showers began to occur around Pagosa Springs around noon. But they were too light to generate any accumulation, especially with the temperature around 40, and at that time most of the lightning strikes were well to the southwest in Arizona. But by a couple hours later, thunderstorms - with a wide variety of precipitation types - were becoming more widespread over New Mexico, with some moving through the Gallup area in the general direction of Pagosa Springs, and other strong thunderstorms near Albuquerque and Santa Fe. By 2:30, thunderstorms were in the area of Navajo Lake, about 35 miles southwest of Pagosa Springs. When I heard the first rumble of thunder around 2:50 p.m., I knew it was time to head out.

The temperature was still around 40, so I was not entirely sure whether the precipitation type would be rain or snow. After a brief foray to the west to study the sky, I decided my best option was to head toward the higher ground a few miles northwest on North Pagosa Blvd., where it looked like snow was already starting to fall. In the meantime, I heard a couple more rumbles of thunder, so I knew it was game on. Quickly I encountered a light rain-snow mix, which quickly turned to all snow. By the time I reached the place where the divided stretch of North Pagosa Blvd. ends, maybe 4 miles northwest of route 160, the snowflakes were getting bigger and I knew I was in the right spot. This was around 3 p.m. I got out the video camera and quickly got some long, low rumbles of thunder with the snow. I repositioned a couple of times in the general area, once to get away from traffic and road noise then a couple more times to keep snow from coming into the car as minor wind shifts occurred. The snow rapidly intensified, eventually bringing visibility down to a quarter mile or less, and the thunder rumbled frequently for about 20 minutes. Although the lightning detection system indicated lots of CG to the west and southwest, it seemed to be all in-cloud lightning at my location - I could not see any lightning in the heavy snow, and all of the thunder was long rumbles - a couple fairly loud, but most of them just low rumbles. I got probably 15 or more minutes of video, which I edited down into this clip lasting approximately 3 minutes:

As you can see in the later parts of the video, the snow fell very heavily in big, wet flakes. Around 3:20 or so, the thunder abruptly stopped, but the snow continued to fall heavily for another 20-25 minutes, eventually mixing briefly at times with graupel after around 3:30. By around 3:45, when I decided to head home because the thunder seemed to be over, a little more than an inch had accumulated - more than an inch in just 45 minutes. When I got home, it turned out that, despite the slightly lower elevation (around 7500 feet, compared to maybe 8000 where I filmed), the precipitation type had also been mainly snow, so a decent thundersnow event there, too - but only a little better than a half inch had accumulated. Soon the snow lightned considerably, but around 4:30 another intense burst began. With this one I heard just one rumble of thunder, but the intensity of the snow was greater, and at times the outflow winds became quite intense, reducing visibility to about 1/8 of a mile. By the time this burst of snow passed over around 5:45, there was 3 inches on the ground at my house, meaning that nearly 2 and a half inches of snow fell during the time of about an hour and fifteen minutes. The pictures below show the snow and blowing snow that occurred with this burst of snow:

The snow ended entirely by 6 p.m., and even some partial clearing occurred. But additional areas of snow were approaching from the southwest, and overnight another 3 inches or so fell, bringing the storm total to around 6 inches by 9 the next morning. The snow accumulated spectacularly on trees and any other above-ground surface. This was the perfect snow for that because 1) it was very heavy, wet, sticky snow, high in moisture content and 2) the snowstorm was convective in nature. Both of these conditions make the snow stick to trees, fences, wires, etc., and the result was a winter wonderland. Here is one picture showing how the snow stuck to just about everything:

I have posted several more pictures of winter wonderland the morning of March 9 to a Facebook album, which I have made accessible to anyone whether or not we are Facebook friends. You can access that photo album here.

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