How snow is made in Missouri when the weather just won’t make it for us

Did you know you could go skiing in Missouri this winter? At Hidden Valley Ski Resort in Eureka, Missouri just outside of St. Louis, crews work to make that winter dream a reality.

General Manager, Jesse Kimes, says one of the struggles of running a ski resort in Missouri is getting folks to remember that they are open, even if it doesn’t actually snow in their back yard.

“One of the coolest things for me is when I go home and there’s nothing there, and I come back in the morning and we’ve got a winter wonderland here," he said.

Pumped from this pond, through several industrial pumps, this water is what will soon become fresh powder, falling from these towers, later this winter. It’s more complicated than just freezing the water. That would blanket the hills in ice pellets or sheets of ice, as would happen with sleet or freezing rain, depending on how and when you freeze it.

For that soft powder, we want tiny ice crystals to form and grow into snowflakes. For that you need even tinier water droplets that are really cold. In fact, they need to be well below freezing. We call these super cooled water droplets, and with no help, these drops can cool to 40° below without freezing! That is, if they are without impurities.

They need what we called a ‘nuclei’ to start the freezing process. These are foreign particles like dust that help begin the freezing process of these super cooled droplets at a warmer temperature. 

Manager of Mountain operations, Dylan Vorbeck, says this is the easy part.

“Do you have enough impurities in that pond?" I asked.

“We do,” he replied.

Snow guns turn liquid droplets into tiny crystals by spraying pressurized water and air through what is called a nucleator, which Vorbeck says is the key to it all.

“It forces the ice crystal by letting the air expand, creating turbulence in the air, and whenever air expands it cools down," said Vorbeck.

The cooling process of expansion makes the spray cold enough for the nuclei (or impurities) to start freezing the droplets. Once an ice crystal forms, these droplets can freeze to them when they collide through turbulence, and the process repeats. 

This can take some time, so you’ll notice most of the snow guns on towers far from the ground. This gives crystals time to freeze before hitting the ground, which is extra beneficial on those more mild days.

Some days are better for snow making than others, but Kimes says keep an eye out as soon as temperatures get near freezing. 

“In that November-December area is when you really want to start looking and we’ll look to be open as soon as it gets cold," he said.

We want it to be cold and dry to make snow, but it's been a little too warm and humid lately. It won't be for much longer, though. Snow making becomes increasingly possible at certain wet bulb temperatures. The wet bulb temperature is the coldest you can cool an air parcel through evaporation alone. Hidden Valley keeps the wet bulb temperature that they consider to be the magic mark a secret, but my research suggests that snow creation is possible at 29°F and below. You can achieve a wet bulb of 29°F multiple ways, as it's a function of temperature and humidity. For example, you can achieve this at a temperature of 35°F and relative humidity (RH) of 56%, but you can also achieve it at 32°F with an RH of 80%. So, it can be warmer than freezing, but your air must be dry. Generally, though, sub freezing temperatures are best to keep the snow frozen on the ground. Additionally, crew may have to account for other factors like sun strength and ground temperatures.

While we can't always count on snow in Missouri during the winter months, we can usually count on enough of these cold and dry days to make hitting the slopes possible, even here in Missouri.