You are looking at charts of the seasonal weather history at select locations. These are areas frequented by recreational backcountry users. Use the charts to create a ‘mental image’ of the snowpack for each area. They were initially created for avalanche awareness and educational purposes. The geographical focus was originally on my former home in northern Colorado but is slowly expanding, especially into western Montana.
The graphs are refreshed daily by about 12:15 pm MST. All fields are collected via automated weather sites from the SNOTEL and MesoWest networks. They are retrieved from the MesoWest website. Whenever possible, I take snow depth/SWE from SNOTEL sites, and I take wind and temperature from the other networks. This is because I can get both depth and SWE from SNOTEL. Also, it is sometimes best to measure snow and wind/temperature at different locations. We want ridge-top winds to get an idea of how much snow is being transported. We want to measure snow in more sheltered areas to get a good idea of how much snow any given storm is producing. Please contact me with questions. If there are other areas you’d like to see added, please let me know!
So, here’s what you’re looking at:
The site name and elevation used for each of the snow, wind, and temperature fields are noted at the top left of each plot. All data displayed on this site is provisional!
The first chart is SNOW:
HN24: Snowfall total for the past 24 hours in inches. Computed as of 7:00 am local time. It is the blue bar graph. The axis is on the left side of the graph. It is usually measured with a sonic snow depth sensor.
HN24W: Snow-water equivalent (SWE) for the past 24 hrs, also as of 7:00 am local time. This field appears as text above the HN24 bars. Units are inches of liquid water. It is typically measured with a snow pillow. Non-SNOTEL sites will not feature this field.
HS: The total snow depth on the ground in inches. It is the red line. The axis for HS is on the right side of the graph. It can decrease with settlement or melting. It is also measured with a sonic depth sensor.
Note that HN24 is from a sonic depth sensor, while HN24W is from a snow pillow. The two don’t always agree, so you might get some snow without SWE and vice-versa.
At the bottom of the SNOW plot is the ‘official’ agency-issued avalanche hazard rating for that day, if available. This website is NOT an alternative to visiting your local avalanche center’s website for the most updated information.
The second chart is WIND:
Somewhat self-explanatory. The thin orange line is the lower bound for ‘moderate’ winds, 17 mph. This is typically the lower threshold for snow transport to take place. Please bear in mind that the location of the measuring device and any potential avalanche start zones might not be the same, and ridge top winds can far exceed what is measured at these sites. Average wind speed, average gust, and average direction are depicted on the graph. Averages are calculated over the day, or 00:00 to 23:59 local time.
The third chart is TEMPERATURE:
Very self-explanatory. The blue horizontal line is freezing, 32*F. Average, maximum, and minimum are calculated over the day, or 00:00 to 23:59 local time.
Notes on individual sites. For the purposes of this website,
Lolo Pass is in the Mountain Time Zone
Colorado users: As of the 2022-23 season, CAIC has moved to using variable hazard forecast zones. For the purposes of this site, the hazard rating shown on the graph corresponds to the location of the snow measuring site.