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A snowy December in Las Vegas, Nevada.

After one of the warmest autumns on record in the Mojave Desert, a drastic shift in the upper air pattern took place in mid-December 2008 as a deep, upper-level trough established itself across the western United States. A series of upper-level disturbances and storm systems moving through the base of the trough resulted in unusual low elevation snow in the Mojave Desert during a roughly two week period.

On December 14th, an upper-level disturbance moving across southern portions of California and Nevada spread moisture into a chilly air mass that was in place across the Mojave Desert. Precipitation began in the lower elevations of the Mojave Desert on the morning of the 15th with snow levels around 3000 feet, however, as precipitation continued and the atmosphere was able to cool, snow levels began to lower to around 2500 feet by the late morning hours. In Las Vegas, a mix of rain and snow occurred at McCarran International Airport, making it the first time snow had been officially observed here since December 22, 2006. Although snow only mixed with rain for about an hour at the airport and never did accumulate here, higher elevations on the west and northwest side of the city (generally above 2600 feet) saw accumulating snowfall for several hours. Between 2 and 5 inches of snow fell in these areas, with even some less traveled roads and bridges in these areas seeing snow stick to them. Over 20 inches of snow fell in the Spring Mountains just west of Las Vegas above 7600 feet in elevation.

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Just two days later, an upper-level low moving through the base of the trough tracked inland from southern California bringing another round of precipitation to the Mojave Desert on December 17th. Moisture associated with the low moved into a low-level cold air mass, resulting in snow falling once again in the lower elevations of the Mojave Desert, with snow levels around 2000 feet. This storm finally moved east allowing precipitation to end on the morning of the 18th. As the air mass slowly warmed, precipitation in areas below 3000 feet ended as rain or a rain/snow mix. This storm produced a swath of accumulating snow from the Interstate 15 corridor southward in just about all areas above 2000 feet in elevation with over a foot of snow in the highest elevations. In the Las Vegas Valley, snow fell in all areas, however, the heaviest accumulations were in the southern portion of the Valley, particularly in Henderson, where as much as 10 inches of snow was measured at just under 2400 feet in elevation. At the National Weather Service Office just 2 miles southwest of McCarran International Airport, 3.6 inches of snow fell, establishing an all-time record for a single December snowstorm and also making December 2008 the snowiest December in official weather records for Las Vegas which date back to 1937. Snow accumulations were greatest on the south end of the Las Vegas Strip, where 1.7 inches of snow fell at the "Welcome to Fabulous Las Vegas, Nevada" sign. Further north in areas closer to downtown, warmer ground temperatures and a portion of the precipitation falling as rain resulted in little to no snow accumulating.

Las Vegans were not done seeing snow as snowflakes fell briefly on two more instances in the month. On December 23rd, an upper-level disturbance produced a brief snow shower. Finally on December 25th, a strong cold front passed through the region dropping snow levels to around 2000 feet. Lingering moisture behind the front resulted in showers that fell as snow or a snow/rain mix in the late evening in parts of the Las Vegas Valley. McCarran International Airport reported a brief rain and snow shower mix around 10:00 PM PST, making it only the third time snow as ever fallen on Christmas Day officially in Las Vegas since 1937. The four instances of snow observed at McCarran International Airport in the month of December tied 1967 for the most calendar days ever in the month of December where at least a trace of snow had fallen.

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Title Annotation:OUTSTANDING STORMS OF THE MONTH
Publication:Storm Data
Article Type:Report
Date:Dec 1, 2008
Words:691
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