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Nevada's Weather and Climate

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Nevada's Weather and Climate Fact Sheet-17-04 Nevada’s Weather and Climate Kerri Jean Ormerod, Assistant Professor/Extension Program Leader Stephanie McAfee, Assistant Professor/Deputy State Climatologist Introduction different seasons. Every place has its own normal Weather and climate are related, but they are climate. For example, Las Vegas typically gets not the same. The difference between weather thunderstorms in the summer. Much of Nevada and climate is time. Practically speaking, weather gets winter rain or snow when large storms that determines which clothes you decide to put on form over the Pacific head eastward. today, but climate determines the type of clothes Weather and climate are influenced and defined that are in your closet. by a number of factors, including atmospheric pressure, winds, ocean currents, temperature and Weather and Climate Basics topography. Atmospheric pressure (the weight Weather describes the variation of the atmo- of the atmosphere, also known as barometric sphere in a particular place over a short period of pressure) is an important driver of weather and time. Weather conditions include changes in air climate. Weather maps indicate areas of similar pressure, temperature, humidity, clouds, wind and atmospheric pressure with lines called isobars precipitation – rain, hail and snow. Weather can (see Figure 1). Areas with high pressure are change over the course of minutes, hours, days marked H and are typically associated with sun- or weeks. Climate is the usual or expected weather for a particular place or region, which is typically evalu- ated over a 30-year time period referred to as a normal. The timescale for climate is months, sea- sons, years, decades, centuries and even mil- lenia. Climate is often thought of as just the long-term average tem- perature and precipitation, but it also includes vari- ability and the likelihood of extreme events. Cli- mate is an assessment of the types of weather that Figure 1. Surface weather analysis map for the U.S., Oct. 27, 2016. The isobars (brown are expected – or may- lines marked with numbers) distinguish constant pressure areas. The lines with symbols depict frontal boundaries. (Source: National Weather Service (NWS) Weather Prediction be not unexpected – in Center, http://www.wpc.ncep.noaa.gov/html/sfc2.shtml.) A partnership of Nevada counties; University of Nevada, Reno; and U.S. Department of Agriculture 1 ny weather. Areas of low pressure are marked L Nevada Weather and Climate and are more likely to receive precipitation. At the Although Nevada is the driest state in the nation, surface, air moves from areas of higher pressure it is also a mountainous state. In the mountains toward areas of lower pressure, producing wind. the climate tends to be colder and wetter. In Larger differences in pressure generate stron- fact, Nevada means “snow-capped” in Spanish, ger winds. Therefore, closer isobar lines indicate and much like other Westerners, Nevadans rely windy conditions. heavily on mountain snow for their water supplies Fronts develop when air masses of different den- (Green, 2015). sity and temperature come in contact. You may Differences in climate from one place to another be familiar with this in the form of cold and warm reflect Nevada’s size and rugged topography, fronts. Fronts, whether cold or warm, typically which ranges from over 13,000 feet in the White mean increased wind, rapid changes in tempera- Mountains to just 500 feet above sea level at the ture, and often precipitation for the local area. Colorado River (Green, 2015). The fact that ele- vation is a particularly important driver of weather Meteorology and Climatology and climate is no surprise to high-country travel- Meteorology is the scientific study of the atmo- ers familiar with the increased likelihood of high sphere. A meteorologist describes the current winds and wet or snowy weather on mountain weather conditions and makes short-term fore- passes. casts (typically no more than seven to 10 days). To produce forecasts, meteorologists rely on real-time observations and computer models of the atmosphere. In addition to weather station and rain gauge observations, satellite and radar technologies and weather-balloon-based mea- surements are used to track storm systems and air masses across the U.S. Climatology evaluates the large-scale and long- term drivers of weather. It includes the study of past climate and projected future climate. Clima- tologists use a variety of instruments, technolo- gies and observations to document aspects of past and current climates and to model past and future conditions. Climate information is im- mensely useful for mid-term and long-term plan- ning and is frequently used by farmers, ranchers, the military, land and water managers, and the shipping and construction trades, among others. Climate conditions are mapped in many different ways by numerous local, regional and national entities. For example, gardeners who utilize the United States Department of Agriculture (USDA) plant hardiness zones (see Figure 2) to select plants from a nursery are already acquainted with Figure 2. The U.S. Department of Agriculture climate. These growing zones are based on aver- (USDA) Plant Hardiness Zones are based on extreme minimum temperatures, 1976–2005. The aging 30 years of minimum winter temperatures. color variation indicates the broad range of climate conditions in Nevada. (Source: USDA, http://planthardiness.ars.usda.gov.) 2 Climographs provide a snapshot of “normal” When wind pushes moist air up steep hills or weather conditions by representing average mountains, such as the Sierra Nevada Range, temperature and precipitation in a specific loca- precipitation occurs. The steep rise in the to- tion over a 30-year time frame. Figure 3 shows pography blocks air flow and forces air mass- climographs for Ely and Boulder City that quickly es upward; this is known as orographic lifting. illustrate how two basic climate parameters differ Orographic lifting wrings moisture out of the air in these locations. The blue lines indicate the on the windward slope of the mountain, leaving average monthly temperatures, and green bars dry air to descend along the leeward side of the indicate average monthly precipitation. As the mountain range. The area in the lee of a moun- climographs illustrate, Ely experiences more pre- tain range, where precipitation is blocked, is cipitation and lower temperatures than Boulder known as the rain shadow. City. Ely is a mountain community that sits at over 6000 feet above sea level. Boulder City is located El Niño and La Niña roughly 225 miles to the south at an elevation of The El Niño Southern Oscillation (ENSO for 2500 feet. short) refers to large-scale changes in the winds and sea surface temperatures in the tropical 100 1.4 Pacific Ocean. El Niño, referred to as the warm Ely, 1971 - 2000 phase, and La Nina, also called the cool phase, 90 1.2 are ENSO’s two extremes. During El Niño, a 80 large expanse of unusually warm water in the (in) 70 1.0 eastern tropical Pacific Ocean can drive changes on 60 in the wintertime storm track into North Ameri- 0.8 ipitati ca. During a typical El Niño winter, more storms 50 ec cross southern California, Arizona, and southern 0.6 40 Nevada, while fewer storms than usual hit the Pa- rageTemperature(°F) 30 cific Northwest. El Niño has little relationship with 0.4 ragePr ve ve wintertime precipitation in the Sierra and northern A 20 0.2 A Nevada. Since the 1930s, northern Nevada has 10 had dry El Niño winters and wet ones. La Niña, 0 0.0 when the ocean is colder than normal in the east- ay ug Jul ep Apr Oct Jun Jan Feb Mar Nov Dec ern tropical Pacific, also impacts the winter storm A S M 100 1.4 track. While there have been both wet and dry La Boulder City, 1971- 2000 Niña winters in northern Nevada and the northern 90 1.2 Sierra, southern Nevada is usually dry during La 80 Niña years (see Figure 4). 70 1.0 (in) on 60 0.8 Atmospheric Rivers ipitati Atmospheric rivers are narrow bands of concen- 50 0.6 ec trated water vapor in the atmosphere associated 40 with strong winds and heavy precipitation. Atmo- 30 ragePr rageTemperature(°F) 0.4 spheric rivers can contain more water than seven ve ve to 15 Mississippi Rivers combined (Ralph and A A 20 0.2 Dettinger, 2011). In the western U.S., atmospher- 10 ic rivers are responsible for extreme precipitation 0 0.0 events as well as destructive flooding and mud- Jul Apr Oct Jun Jan Feb Mar Nov Dec Aug Sep May slides. Although they can be destructive, atmo- Figure 3. Climographs for Ely (top) and Boulder City spheric rivers are particularly important drivers of (bottom), 1971–2000. (Source: Data from Western precipitation in the Sierra and western Nevada. Regional Climate Center (WRCC), http://www.wrcc. dri.edu/.) 3 100% Elko 50% 0% -50% El Nino Neutral La Nina -100% 1950 1960 1970 1980 1990 2000 2010 100% 100% 100% Reno Elko 50% 50% 50% 0% 0% 0% -50% -50% -50% -100% El Nino Neutral La Nina -100% -100% 1950 1960 1970 1980 1990 2000 2010 1950 1960 1970 1980 1990 2000 2010 1950 1960 1970 1980 1990 2000 2010 300% 300% Las Vegas Figure100% 4. Percent of normal October – March precipitation Las Vegas for Elko, RenoReno and Las Vegas (1950–2016). El Niño years are orange, and La Niña years are turquoise. In Las Vegas, 200% essentially50% all La Niña years have below normal precipita- tion, and all El Niño years have above normal precipitation. 100% 100% The 0%pattern is not as clear in Elko or Reno, which have had wet and dry El Niño and La Niña years.
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