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Black Hills Region Winter Weather



Huge piles of snow lined the streets of Deadwood after a late winter storm dropped 3 to 4 feet of snow on the town. Photo courtesy of KEVN/Fox 7 news.
Winter in the Black Hills is a season of extremes. Weather can go from sunshine with mild temperatures in the mid 40s to mid 50s, to raging blizzard in just a few hours. Nearly every type of winter weather scenario is possible in western South Dakota.

From heavy snow, freezing rain and bitter wind chills to dense fog, screaming winds and pollution inducing inversions, just about anything can happen. This is one reason why weather forecasting around the Black Hills from November to March is such an incredible challenge to meteorologists. The amount of snow in any given winter varies so much year to year that anything called an "average" may be a bit misleading. Nonetheless, the statistical average snowfall in a given winter for Rapid City is around 3 feet. The amount of snow will also vary greatly throughout the region, with the "snow capital" of the Black Hills being the area around Terry Peak in Lawrence County. Snowfall in this area will easily be two to three times what it is Rapid City. That is one reason why the northern Hills is a hub of winter recreation activity.

There is a reason why the northern part of the Black Hills gets so much snow. The storms that produce the heaviest snowfall in the region tend to originate south of the Black Hills, especially in Colorado. As areas of low pressure that form a storm's center cross the Rockies, they have to be closely watched. If the storm moves northeast, toward central or eastern South Dakota, then there is the potential for it to be a big snow producer in the Black Hills area. This is because the "heavy snow band" associated with winter storms in the northern plains tends to be between 50 and 150 miles north to northwest of the storm center. Other key factors that determine the intensity of snowfall associated with a given storm include the amount of moisture the system has to work with, the amount of cold air feeding into the northwest quadrant of the storm, and the speed of the system's movement.

As the storm passes east of the Black Hills, winds swing around and blow from a northerly direction. The speed of the wind is often an indication of the depth of the cold Canadian air feeding the system. As these northerly winds blowing across the plains reach the Black Hills, the air is sometimes forced upward. This upward forcing of air by higher terrain is called "upslope flow". The upslope flow takes the moist air near the surface and cools it as it rises, resulting in condensation and precipitation in the zone of upslope influence. Since Colorado lows" tend to be the strongest and slowest moving of the storms that influence the Black Hills area in the winter, these are the storms that often will present the northern Black Hills with the longest and strongest periods of upslope induced snowfall. The portion of the Black Hills contained by a triangle running from just west of Spearfish to just south of Sturgis to Rochford and back gets the most snow.
Winter Weather, Black Hills
An early winter storm hit Lawrence County in the northern Black Hills on October 4-5, 1998. This Spearfish Canyon shot shows heavy snow bending trees across powerlines. One to three foot snowfall totals, enhanced by upslope flow, were common. Many residents were without electric power for several hours. Photo by Randee Peterson from the www.spearfish.com/canyon website.
In the heart of this area lies Terry Peak, the second highest mountain in the Black Hills, and the communities of Lead and Deadwood. The exact direction of the upsloping winds, however, can alter where the heaviest snow will fall. A more northeast component to the surface winds, for instance, will shift the area of heaviest snow more toward Sturgis and the high country south and west toward Galena.

A more easterly component to the upslope would favor the Piedmont to Hermosa area and high country to the west from Nemo to Hill City. Keeping an eye on the forecast surface wind direction when a winter storm watch is in effect can give you a clue as to where to look for the heaviest snow.

The "Colorado low" is not the only kind of winter storm system to affect weather in the Black Hills. The "Alberta clipper" is another system to be respected. These are fast moving winter storm systems that dive southeast out of Canada into the northern plains. They are named for a kind of sailing ship noted for its speed. Because the clippers are fast moving, they usually don't hang around an area long enough to produce large amounts of snow, but they do have a reputation for leaving strong northerly winds and bitter cold temperatures in their wake. This is because the clippers are steered southeast by a northwest to southeast orientation to the jet stream, and behind the clipper usually follows "Yukon Jack" or the "Siberian Express"…names given to areas of strong and very cold high pressure originating in the Arctic. Even a few inches of fresh snow can be whipped up by winds in the wake of a clipper type system to create reduced visibility near the ground and dangerous wind chill factors. These "ground blizzards" are deceptive in that skies may have cleared as the clipper raced southeast, but in spite of clear skies overhead, the horizontal visibility could be near zero at times. Those foolish enough to venture out onto the plains in such conditions may find themselves drifted in on a remote roadway and at the mercy of the bitter cold temperatures and wind chill factors.

Wind chill is a concept that originated in the military as a means of measuring the added heat loss caused by the wind against a soldier's body in a winter combat situation. As a person stands in air colder than their body temperature, heat is lost from their body to the air that surrounds it. The colder the air a person stands in, the greater the heat lost to that air. As wind blows against our standing person, a "fresh" supply of cold air is in contact with their body at all times and the process of robbing the person's body heat is accelerated. Perhaps thinking of this process in reverse will help illustrate how it works.
Suppose you have a frozen chicken that you want to thaw for dinner. You place the bird in a kettle of warm water to enhance the thawing process. An exchange takes place over time in which heat from the water is transmitted to the chicken, but as this happens the water becomes cooler and loses its thawing ability. Though wasteful of water resources, everyone knows the chicken will thaw faster if you place it under running warm water. Heat from the water is more quickly transferred to the chicken by constant contact with the running water. Cold winter winds work on warm blooded animals in the same fashion, but in reverse.

Underestimating the danger of wind chill is a leading cause of frostbite. Military studies have concluded that any exposed human skin in a wind chill factor of -70 degrees or colder will begin to develop frostbite in as little as 60 seconds. Unless medical attention is sought as soon as possible, there is a real danger that the affected area will have to be amputated. First aid for frostbite consists of removing the victim from the cold environment, wrapping the affected area in clean and dry cloth, and transporting the victim to a medical facility. Under no circumstances should the frostbite area be vigorously rubbed or placed in hot water. Doing so will only make the wound worse and could result in further permanent tissue damage. Few weather terms command more respect from long time residents of the Black Hills area than "blizzard". This, the most severe of winter storms, is arguably the deadliest, costliest and most economically devastating of the weather dangers faced by the region. By definition, a blizzard is a winter storm that brings a combination of wind, falling or blowing snow, and bitter cold wind chills or temperatures to the warned area over a period of several hours. Visibility in a blizzard situation is less than ¼ mile, and "white out" conditions are common in open areas. Anyone who has had the misfortune of encountering a Dakota blizzard from the driver's seat of a motor vehicle will tell you it's not something they would want to repeat. Rural areas can be isolated for days at a time, drifts of snow can reach many feet in height, electric power can be cut off for long periods of time, and roads could be closed or blocked by drifts.


Reminders of the great blizzards across western South Dakota in the spring of 1997. A dead sheep frozen solid where it lay, and a barrier closing Interstate 90 on Rapid City's east side. Photos courtesy of KEVN/Fox7 Television in Rapid City.
The economic impact of a major blizzard can easily reach into the millions of dollars when the cost of lost business, cleaning up roads, dead and/or injured animals, the emergency search and rescue operations, and structural damage from snow, wind and ice are all taken into account. The winter and spring of 1997 were especially hard for area ranchers when a series of winter storms prevented them from getting food, water, and supplies to their herds. Livestock losses were in the tens of thousands of animals, and several ranchers were forced out of business.

Fortunately, blizzards of such severity are not all that common. In a typical winter season, there might be two or three blizzard warnings issued for some portion of the Black Hills region, and a severe blizzard may strike Rapid City only once every 2-3 years. Nonetheless, serious attention should be paid to weather reports whenever the term "blizzard" is mentioned.

A final winter hazard that should be mentioned in any discussion of Black Hills winters is the ice storm. Freezing rain and drizzle result when a temperature inversion spreads a layer of warmer air just above a layer of air with a temperature below freezing at the surface and precipitation is taking place. The precipitation usually begins above the surface as snow, which then melts as it falls into the layer of warmer air above the surface. The resulting drops remain in liquid form until they come in contact with surfaces that are below freezing in the cold air at ground level. The drops then freeze on contact and envelope the surface in a layer of ice. This ice accumulates on roads, trees powerlines, buildings and vehicles. When accumulations are significant, nightmarish scenarios that can include impossible driving conditions, broken tree limbs, snapped power lines and difficult walking conditions are the result. When the accumulations are light, as in the case of a light mist or precipitating fog, a beautiful frosted landscape creates the appearance of a winter wonderland. Fortunately, severe ice storms are rare in the Black Hills.

Freezing mist created these frosty looking pine trees along Rapid City's Skyline Drive.
Photo by Dan Carlson.

When discussing the various winter weather hazards that face the Black Hills region, one must be cautious not to overstate the dangers. The area provides some of the most excellent outdoor winter recreation anywhere with miles of snowmobile and cross country ski trails, excellent downhill skiing, ice fishing and breathtaking scenery. Fear of dangerous winter weather should not keep a person from enjoying all that the Black Hills have to offer during the winter months, but respect for the turns that nature can take, and a watchful eye on changing conditions, will ensure that participation in outdoor winter activities remains safe and enjoyable.


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