I'm no expert, but I think with gable vents that big and all the snow they've been having this year, you may need to temporarily board the vents up each winter. That one just above the lower roof looks especially susceptible to it.

A couple of eye hooks on each side to hold the board in place, or maybe some short pieces of 1x2 with a screw through the middle that you can rotate to horizontal. Paint the 'out' side to prevent water damage from the melting snow, and make sure it fits snugly. Of course, you need to be sure to remove them at the end of winter and replace them before the start of the next one.

Closing the vents in the winter is the best idea but if that is not practical you could permanently close off the lower half of the louver panel since they appear to be greatly oversized. Adding insect screening to the upper half might help too. You could also add a pan over the insulation to catch the snow and allow it to eventually evaporate. You might even try a periscope type sloping baffle/plenum that is open to the attic at the top and drains to the outside at the bottom. That's the way it's done for louvers in large commercial structures; some are large enough to walk in.

The purpose of the vent is to allow excess moisture to escape from the attic space in the summer and is not for the purpose of cooling the attic which would require a rather large fan. In Aurora it shouldn't take much of a vent to allow moisture to escape to the outside. In fact, the vents aren't of much value unless the roof leaks.

The vents are not constructed properly.
At the very least there should be overlap of the baffles when viewed straight on for about 30% to 50% of the width of each baffle.
This normally stops most wind driven rain and snow.

Snow in Colorado will go anywhere the wind can go. I'm surprised that this kind of decorative louver would even be used there. A "storm proof" louver is made of aluminum and has a vertical lip hanging down at the outside face and standing up at the inside face. The lip edges are often bent to form a return to trap wind and water.

A finer mesh, like a geotextile filter fabric, instead of the rodent proof hardware cloth would block more of the snow from entering. Of course it will also decrease the effectiveness of the vent. Cheap way to address the problem in the short term.

However, as others have recommended, I'd shop for new vents with different louver profiles.

For the past posters that said that the vents are not constructed properly I don't think you fully understand the circumstances such as high winds, size of the snow particles and direction that the vents are facing.. In a windy location such as Wisconsin near lake Michigan the fine snow that rests on the roof can get whipped up and blow about like a mini blizzard. This snow can blow into the vents and settle I solved this issue very easily and quickly. as you can see in the pictures the vent is constructed correctly with screen and mesh but this fine snow can still make it's way into your attic. The product below is a big upgrade on the cheap fiberglass filters that some have suggested and still maintains air circulation that is important.
I purchased the product you see in the second picture at home depot for about $8 it's a 24 in. x 36 in. x 1 in. Cut-To-Fit made by Natural Aire. You can cut this material with heavy shears or a razor knife to create any size. It is springy, almost rigid and needs no frame for support. Just cut a bit larger that the framed opening and push it in to install. Took me less than 5 minutes.

Great idea will do it where i can access vent inside but have a few accessible from outside only so i'll build a frame and secure this to it and secure frame with eye hooks...thanks