When we discussed the role of weather yesterday, we mentioned the historic, sweltering temperatures, the state-wide drought, low humidity, and gusty winds. But we neglected perhaps the key environmental contributor: the profound lack of spring snowpack across the state.
Climate Central’s Andrew Freedman wrote an insightful piece demonstrating the critical role a lack of snowpack plays in wildfire prevalence. He highlights one particular chart revealing that “2012 winter season delivered anemic snow cover to Colorado.” But just how anemic?
The image above - from the Natural Resources Conservation Service - tells the story: as of May 1, the average state-wide snowpack was more than 80 percent below average, and just 14 percent of 2011’s snowpack.
In 45 years of snowpack records, this (2012) snowpack tied 2002 for the lowest on record. For its part, the 2002 wildfire season was also extremely active in Colorado. 1,994 fires consumed more than 500,000 acres and destroyed 384 homes (source: Slideshow of 2002 Colorado Fire Season). These included the largest wildfire in state history which burned 137,000 acres and destroyed 133 homes (source: USA Today).
Freedman points out that not only is the lack of snow cover a key contributor to wildfires, but also the timing of the “meltout” (when the snow is gone). This year, he said, the snow meltout was June 4 compared to the median date three weeks later on June 25.
He added that the relatively deep snowpack the year before (see the chart above which shows May 1 snowpack was 135 percent of average) contributed to spring plant growth - making more “fuel” available for this year’s flames.
The lack of snow this spring was linked to the combination of very warm and dry conditions. According to the National Climatic Data Center, the March through May period was second warmest on record in Colorado. The western part of the state experienced its driest spring on record.
The warm, dry pattern was connected to an unusually far north displacement of the jet stream keeping the storm track north of the southern Rockies while allowing mild air to surge into the region.
Climate warming from greenhouse gases is likely to have somewhat increased the warmth and intensified the dry condtions.