Colorado's Terrain: Where Is That?

Descriptions of geographic features in Colorado and how they influence our weather

Palmer Divide: It doesn't seem like much when you drive over it on I-25, but at the summit of 7350' on Monument Hill versus the 5280' or so in downtown Denver and the 6000' or so in downtown Colorado Springs, its enough of a hill that plays havoc on observed weather and on forecasting the weather in Colorado. Often in strong northerly wind flow downtown Denver as an example may have a couple inches of snow, while southern Douglas County and northern El Paso County have a foot more and downtown Colorado Springs has a trace. This is due to the fact that as cold air moves in from the north, it is being lifted from the South Platte River in downtown Denver to the crest of the Palmer Divide (creating clouds and precipitation) and sinking on the journey from Monument to the Arkansas River in Pueblo. Anytime air sinks, it eats away at clouds and precipitation and is responsible for the "doughnut hole" that you frequently hear us talk about. This is why the downtown Colorado Springs to downtown Pueblo area usually gets a lot less snowfall than surrounding areas. As a higher point, it helps to provide instability and often acts as an area of thunderstorm initiation from the late Spring to the early Fall. Geologically it is the "divide" between the Arkansas River Basin in southeast Colorado and the South Platte River Basin of northeast Colorado.

Raton Mesa: Its very similar in geologic purpose to the Palmer Divide, as it divides the Arkansas River Basin from the Canadian River Basin in eastern New Mexico. As northerly flow heads from the Arkansas River toward the crest of the Raton Mesa on the Colorado and New Mexico state line, it again gets lifted, rising some 2000' plus in elevation and helping to make this an area of heavier snowfall in most winter snow storms and an area of thunderstorm initiation in the warmer months.

Lower Arkansas River Valley:In contrast to the two divides that funnel water into the Arkansas River, this is the "lower" elevations of the plains of Southern Colorado. Its a population center with many towns along highway 50 and is also an area of air transport during both the warm and cold season. During thunderstorm months, low level moisture from the Gulf of Mexico will draw westward into Colorado along the river valley and can be an area of stronger thunderstorms versus the higher terrain due to the additional fuel for thunderstorm updrafts that the moisture provides. During the cold months, the coldest air is usually found along the river valley. This is due to its density being higher than relatively warmer air and because of gravity's influence on it, acts "heavier" than this warmer air. A lot like water in a bowl, it collects in the lowest spot and this is right along the river itself.

Upper Arkansas River Valley:This is typically meant to be the valley created by the Arkansas River where it opens up just outside of Salida to the river's headwaters north of Buena Vista. One of the more beautiful spots in Colorado, we find it one of the more difficult areas to forecast snowfall amounts in the winter. As you might expect, it usually gets less precipitation than the surrounding mountains due to mountain shadow effects of wind flow. It is world renown for its whitewater rafting with the peak season coinciding with maximum snowmelt from late April through mid June.

Wet Mountains:A small mountain range just southwest of Pueblo. The most intersting thing about this mountain range is that the communities of Rye and Beulah at its base occasionally get 3 to 4 feet of snow while downtown Pueblo gets nothing! This is also an area prone to downslope windstorms along the eastern slope when large scale windflow is perpendicular to the orientation of the range.

Sangre de Cristo Mountains:Similar in orientation to the Wet Mountains (SE-NW), this range is a little farther to the west and is about 4 times longer than the Wet Mountains. Containing several 14ers, this range is interesting because of its noticeable elevation gain given a short "base". La Veta Pass along highway 160 can be particularly difficult travel in the winter during storms as it typically has quite a bit of wind, making for noticable ice on the road and reducded visibilities.

San Luis Valley:One of the four major mountain valleys in Colorado, this flat floor is ringed by large mountains to the west, north and east. Cold air gets trapped on the valley floor during the winter and will become trapped there for up to several weeks at a time. Occasionally the coldest spot in the nation during the winter months, Alamosa can have high temperatures slightly above zero when the dense cold air is entrenched on the valley floor and can quickly drop to more than 20 below immediately after sunset in extreme cases. One of the drier areas in southern Colorad due to a mountain "rain shadow" effect caused by the surrounding higher terrain.

Central Mountains:The Sawatch and Collegiate ranges including Monarch Pass, Mt. Yale and Princeton is generally considered as the mountains west of highway 24, north of highway 50 and south of Interstate 70. Some of the ski resorts included here are Monarch ski area, Ski Cooper, Vail and Beaver Creek.

Northern Mountains:Primarily encompassing the mountains north of Interstate 70 in Colorado, this area does extremely well in terms of snowfall during storms that have northwest flow. This wind direction is most perpendicular to the upwind face of the mountains and tends to provide the most notable terrain enhanced lift. Steamboat and Winter Park are the major ski resorts in this region, but the argument can be made that the Interstate 70 corridor itself resides in this region.

Front Range and Foothills:The Front Range of Colorado is the notable east face of the Rocky Mountains that stretches from the Colorado/Wyoming state line southward to the east face of the Rampart Range in El Paso County. This area is also interchangeably used with "the foothills" and is encompassed by the orange shaded area on the state wide map. This is an area the expereinces some noticeable weather specifially due to the significant elevation change that occurs within it. Downslope wind storms on the order of 100+mph, heavy upslope snow and thunderstorm formation all occur here.

Cheyenne Ridge:Similar to the Palmer Divide or the Raton Mesa, this is simply the high point that separates the South Platter River Basin in northeast Colorado from the North Platter River basin of southeast Wyoming. Like the Palmer Divide, the crest of this feature and its northern slope can get enhanced snowfall in northerly windflow snow storms. It is also an area for enhanced thunderstorm development during the summer months.

Northeast Plains:In general this is meant to include the areas between the crests of the Cheyenne Ridge and the Palmer Divide, including many of the major cities along Interstate 76 to the northeast of Denver. This also includes the South Platte River channel, which parallels I-76. Greeley, Akron, Sterling and Fort Morgan all lie in this area. Similar to the lower Arkansas River valley in our neck of the woods, this is an area where cold air and moisture funnel toward the mountains, depending on the time of year.

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