When air temperatures drop below freezing during winter months, we deal with freeze-thaw conditions. The freeze produces frozen dirt, "ice grass" (as seen in the first three images), ice, and then eventually mud.
Any moisture existing in the soil or clay at the time of freezing squeezes out of the earth in the form of what we call ice grass.
The more recent the rain or snow, the taller the ice grass. As the day time temperatures begin to warm back up to thirty plus degrees, the ice and or ice grass begins to thaw and melt.
This freeze-thaw cycle happens multiple times during the week when air temps drop below 32 overnight and then rise again during the day. The radiant heat on a sunny day intensifies this process. The radiant heat during park operations can change ride and road conditions very quickly. As the ice melts, it's as if the park experiences a fresh rain from the ankles down. The air temps can be warm enough to melt the ice but still cold enough to keep the mud thick, like peanut butter, which sticks to everything. Sometimes the mud re-freezes onto the bikes.
We work very hard to predict when these conditions will make park operations difficult at which point we may choose to cancel riding, preferably the day before. Unfortunately the science related to predicting constantly changing mountain weather is not always dependable. Should we need to turn off operations, we will contact riders by email. If you've come to the cart to purchase your online pass and discover that operations have been turned off for the day, this is likely why.
We offer this information to help riders make a choice about riding during winter. It is NOT our choice or intention to ride on a day when freeze-thaw conditions are as severe as these images represent. Winter riding will almost always involve some mud. Occasionally, it's necessary to close a trail or trails due to poor conditions developing after we begin operation. This includes the "easier" blue trails which can mean advanced riding skills are necessary.