Another train of cold fronts is headed to Colorado this week which will keep the below average temperature trend rolling - other than on Friday - right through the weekend. The good news: they're not as bitterly cold as last week's. The other difference: the next front to bring the chill to southern Colorado, won't bring any snow. If you've lived here for a long time, you're likely used to this, but this is actually unusual compared to how cold fronts work in most of the country. As with almost every weather oddity in Colorado...you can blame the mountains. WHAT IS A COLD FRONT?First lets talk about what a cold front is. You probably already know that it divides warm air and cold air. I like to think of them like snowplows- because cold air is heavy and dense - and because if you could actually see one from the side, that'd be how it would look. When a cold front moves through town, it shoves warmer air in front of it up and over it, just like if you were shoveling snow. In many parts of the world and in most of the United States, moving warmer (and typically wetter) air upward is all you need to produce storms. But not here. Cold fronts come into southern Colorado from many directions. The direction largely determines what the front does - to the point that, if you know the direction a cold front is arriving from, you can reasonably predict the weather that will follow without looking at a weather model or knowing any additional information. Useful if you're out in the wilderness. WHICH COLD FRONTS CAUSE SNOW IN COLORADO?While cold fronts are typically very steeply sloped like a shovel and typically push air up, Colorado's mountains throw a wrench into things. In Colorado, cold fronts produce snow when they result in upslope flow. Cold air itself is dense and tends to sink. On flat ground, that fact means it pushes air in front of it up (and out of the way). But here, if a front comes in from the mountains, the air actually falls. Sinking air is bad for storms. When a cold front in Colorado moves from the plains to the mountains, we get snow. Remember the front we saw last Friday?That front moved a bit from the plains toward the mountainscausing air to move upward and that produced snow.WHY ARE SOME COLD FRONTS IN COLORADO DRYColorado gets dry cold fronts when the front moves from the mountains to the plains - typically from the northwest. In this setup, the western slope, and central mountains, can get snow on their northern and western faces, but as the cold air falls and rolls down the eastern flanks of the mountains - the air dries out, and we instead tend to get downslope winds. In fact, sometimes a cold front coming in from the west temporarily warms us up, because of the downslope winds it produces! It typically isn't until a northerly wind shift after the boundary crosses the area that we actually see a cooldown. That's the front type arriving in Colorado Wednesday. The northwest direction of the front means air is sinking - and therefore, no storms - at least for southern Colorado. The mountains get some upslope flow - particularly the northern mountains - so they get a bit of snow from a set up like this. WHAT WEATHER SET UP GIVES THE PALMER DIVIDE AND WOODLAND PARK SNOW?When a cold front comes in from the north, the picture is more complicated. In that case, it depends on whats going on behind the front. Sometimes we get some upper-level energy or another weather feature that combines to give us some wind into the mountains behind the front. In that case, storms develop over the plains. Other times we only get wind from the north. This is good for snow over the Palmer Divide and parts of Teller County - but not much for the rest of us. The main takeaway from this is that cold fronts work a bit differently in Colorado than other places. Cold air is dense. In most places that means air rises when a cold front passes and that leads to storms. But because of the Rocky Mountains - some of our cold fronts actually sink. So even though were getting another cold frontdont expect the same kind of snow we saw last week. The mountains are making sure this one stays dry. ____Have a question or story idea you would like the First Alert 5 Weather team to consider? Email: [email protected] KOAA News5 on your time, anytime with our free streaming app available for your Roku, FireTV, AppleTV and Android TV. Just search KOAA News5, download and start watching.