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Show . I - . .. , aw N The Sampler, Dec. 20, 1984 Winter weather woes of Western Utah Of greater importance to tion, the winds blowing across "blizzard flats be- Dugway commuters is the fact that Tooele is beautifully located to receive both lake effect and orographic tween Fries Park and 5 mile hill will be considerably stronger than at either Ditto or English Village. If snow is falling or has recently fallen, substantial blowing and drifting snow can result, severely degrading road and driving conditions. A similar situation can exist in Skull Valley between Dugway and Terra, and, snows in copious amounts. During a lake effect situation, a zone of heavy snow will extend from the northern limits of Tooele through Rush Valley into the Clover area. Ironically, conditions over Johnsons Pass proper may be quite good. As the winds in the backside of a strong winter storm vary in direction, the zone of heavy lake most notably, in Rush Valley around Clover. In fact, conditions in Clover can become so severe as to render the roads in the area totally impassable. Since these conditions may not be reflected in By S. W. Bleda, Jr. The old adage that the four, seasons of Utah are June, July, August and Winter may, at times, be an overstatement of the truth. But at other times it comes distressingly close to fact. Winter often comes early and stays late in the high desert country of the Intermountain West. Persistent cold, snow, and fog plague all who venture forth in this area. Astronomically, Winter officially begins this year at 9:23 AM on December 21st. . Here at Dugway with its mixed bag of desert flatland and upslope terrain, we experience sharp variations in weather conditions at Closely adjacent locations. In general, there is an increase in the amount of precipitation received from the Salt Flats eastward towards English Village. In addition, our "East Bench location at English Village receives sig- nificantly more snowfall than does the Ditto Weather Station because of its higher elevation and terrain effects. Although not as pronounced as in the summer, English Village can receive as much as twice the amount of preci- and can be expected to Weather Station in any tinue through March. In fact, a final fling of winter weather is not even out of the question in May! All of us here in Northern Utah share in this grim fact of life which is complicated by a mix of topography and bodies of water peculiar to this particular area. This mixture results in significant minor and major scale effects superimposed upon major weather systems as they pass through the region. The impact of these effects will be discussed in shift. Under strong north to north northeast windflow, the lake effect can even the conditions existing at this article. But for all practical intents and purposes, one can consider that, meteorologivally, Winter has already begun con- effect snow will tend to pitation as does the Ditto gi- ven weather situation. Wind exposure is another situation where terrain effects become important. As a general rule, northwest winds will blow stronger at Ditto and the salt flats than elsewhere. On the other hand, southerly and due north winds are strongest in English Village and Fries Park. Northerly winds generated by a large winter storm are capable of major impacts on the daily Dugway commute. During such a situa either Ditto or English Village, the motorist can easily be caught by surprise. reach into the Dugway area. This is when conditions in "blizzard flats are. at their The Dreaded Lake worst. During strong lake effect situations, snowfall amounts in Tooele and favored areas of the Salt Lake Valley can easily exceed 12 inches. Effect (DLE) Another situation that can cause sudden changes in weather conditions over short distances is the Dreaded Lake Effect (DLE). The Great Salt Lake like any other large body of water heats up and cools down very slowly. In addi- Although average winds at Dugway during the winter are light, this can be misleading since the usual situation is for the wind not to ' blow at all or to blow very strongly. Strong winds are tion, although greatly reduced at present, the salt content of the water pre- usually associated with storms or frontal systems and generally occur prior to and after their passages vents the lake from freezing over completely during the winter. Add to this the currently swollen size of "Ole Salty, and one has a perfect heat source for modifying cold air streams that pass over the lake. As cold air is heated from below by the warmer lake, it becomes unstable resulting through the area. Strong pre frontal winds are usually warmer and dry and blow from a southerly direction. Whats a HATU wind? frontal winds are common combination of mountains and valleys surrounding the Great Salt Lake greatly complicates the situation. throughout the U.S., here in Utah they have been given a distinctive popular name the "HATU. Strongest in the western valleys and deserts of Utah, the HATU characteristically 5 blows in gusts up to mph which, though strong, are not usually severe enough to do damage. In English Village, the HATU can reach speeds up to 5 mph one to three times a month during the year. Such winds can cause problems for drivers of light -- When the lake effect is operating, a common occurrence is to have a narrow but literally solid wall of near snow burying 35-4- 1-- 80 . 45-5- and high profile vehicles. In areas where wind tunneling due to terrain occurs, winds during such a situation can reach up to 70 mph or more. When an intense storm develops in Nevada, HATU winds can gust up to 70 mph or more in the Dugway area which can pose a serious hazard to personnel and property. In these ex. treme situations, intense wind between ' Tooele funnelling and Stockton can ea- sily result in hurricane force wind gusts which can be quite dangerous. Behind the front, comparable wind speeds can occur. If these post frontal winds are northwesterly, then they will be strongest in the Ditto area. North winds funnelling Youll fi the best bargains in your own backyard Local merchants need your continuing support so they make it to your advantage to shop locally. No matter what you need, from groceries to clothing, to hardware supplies, youll find the best buys at the local stores. Good customers keep the merchants in business, and quality service ancTmerchandise keep the customer coming back so its a bargain for both ofyou! When you shop locally, everyone benefits. it's more convenient so you save gas and time. You get friend- knowledgeable service because local merchants know you and appreciate your business. They depend on you to keep their stores going strong. And some of what you spend goes back into the community in the form of taxes and charitable contributions paid by the merchants. ly, leys. Here at Dugway, since we are further away from any moisture or pollution source, the fog will not form until the temperature falls low enough for the moisture in the air to condense or until it drifts in from an outside source. Unfortunately, this usually gives us only a day or two of grace. Frequently, the temperature may be cold enough for the fog to coat all exposed surfaces with ice or frost. occur. If it tracks south of Dug- Although such strong pre in heavy snow showers. The At the same time, fog will begin to form in the vicinity of the lakes and will soon involve the whole of the val- Wave is a secondary low pressure system that develops rapidly on the trailing portion of a cold front in an area encompassing central Nevada and western Utah. Because of the rapidity and proximity of this development, weather conditions in this situation can become very poor very fast. The track of the storm as it develops is important. If it tracks north of Dugway, windy conditions with rain later changing to snow will down Skull Valley will be strongest in English Village. Northerly winds will be strongest and persist longer in Rush Valley near Clover also because of funnelling ef--. fects. During the winter, this can cause severe ground blizzard conditions around Clover that persist long after conditions have improved elsewhere. The wild Williams Wave most dangerous storm situation that can The develop during the winter in Utah is referred to as the Williams Wave. A. Williams way through central Utah, then heavy snow will be the result. Once the system moves east of Dugway, the intensity of the northerly flow behind it and, consequently, the intensity of the lake effect snows and ground blizzard conditions will depend upon what the system does after it leaves Utah. Unfortunately, this type of storm often, intensifies into major proportions. It can also get cold enough for the fog to freeze a light snow with the result that Dugway can experience brief clear periods during an extended fog episode. During an intense inversion, temperatures can be as 0 mfich as degrees warmer at the top of Johnson's Pass than they are down here in Dugway. Skies will also be beautifully clear above the inversion. It's ideal skiing weather, but down here its the pits! Such situations normally last about a week, but it can last from one to two MONTHS if the high pressure system aloft is very strong and gets locked into place as happened last 30-4- Finally. . . the fog The final condition that can create problems for Dugway in the winter is ra- diation fog. Common throughout the U.S. in winter, it is especially prevalent in the valleys of the western states. Fog at Dugway. results when warm dry air from a high pressure system aloft overlies colder air at the surface creating a temperature inversion. High pressure will also build up at the surface in this situation resulting in very light winds. Under the clear skies that initially occur, heat will radiate very rapidly from the surface at night. Because of the shorter hours of daylight and the low solar elevation angle, winter. It usually takes a cold frontal passage to clear the fog out. Ironically this will result in warmer temperatures at Dugway as the front destroys the inversion and scours the cold air out until anotherhigh builds in and we start all over again. The most obvious hazard in this situation is, of course, the poor visibility for drivers due to the fog. This is especially true at night in unlit rural valleys. In addition, the ice deposited by daytime heating fails to break up the inversion cold fog can make roadways and bridges very slick. There you have it. . . winter wonderland. I wonder when well see land again, but that's our springtime feature. Happy holidays which slowly gets stronger. This is especially true if the ground is snow covered. Dug-way- 's In the Salt Lake, Utah, and Tooele valleys, air pollution will become trapped in the colder air and soon from all of us at the . reach uncomfortable levels. ASL Met Team, Dugway. Winter climatology for. Dugway MONTH December 38 9F Average High Average Low Extreme High Extreme Low 19 IF 64 F 23 F -- PRECIPITATION .61 Average (In.) 2.331983 Extremeyear Snowfall (In.) 36 15.61968 Extremeyear January 38 OF 17 OF 66 F 25 F -- .53 1.541980 3.9 10.0 1980 upon weather records main Weather Station by ASL Met Team, Dugway) the Ditto .This year 'why notjm'siEfe it Mome for .the 'road'ii! - J S, |