The storm which blanketed the Front Range Foothills with over a 12 inches of snow in some places on Friday was the second largest January snowfall I have measured during the past 9 winters we have lived here. The ranking of January snowfalls according to my records is as follows:
- January 4-5, 2017 18.1 inches
- January 12, 2019 9.5 inches
- January 4-5, 2014 9.4 inches
- January 21, 2018 8.4 inches
- January 20-21, 2015 8.0 inches
- January 30-31, 2014 8.0 inches
- January 27, 2014 6.8 inches
- January 11-12, 2012 6.3 inches
- January 9, 2011 6.0 inches
As you can see, January is not normally a month of big snowfalls. There are many reasons for this:
- One of our primary moisture sources, the Gulf of Mexico, is normally cut off from Colorado as cold air masses plunge into the central United States. In general, January is one of our coldest months and moisture is more scarce than the warmer months.
- Often a warm ridge builds across the Western United States in January. This forces the storm track, on average, north of the Central Rockies resulting in drier weather along the Front Range.
- The large southern tracking storms which tend to bring the Front Range its biggest snow storms are more frequent in the fall and spring and less frequent in the middle of winter
The storm last week was also notable in that the snow had a decent amount of water in it for this time of year. I measured 9.5 inches of snow and 0.79 inches of liquid equivalent. If you do the math, this works out to be 12:1 ratio which is quite “wet” for January. Normally, the snow-liquid ratio is between 15:1 and 20:1 in January.
As expected the heaviest snow fell to the east of the Peak to Peak Highway, in the foothills between Boulder and Nederland. This is common in January with colder storms. As we get into the late winter and spring, the heaviest snow associated with upslope storms extends further up towards the Continental Divide.