Las Vegas, the gambler's paradise in the desert whose average high sits at or above 100°F for three months of the year, is getting ready to see a rare and potentially dangerous snowfall on Tuesday and Wednesday. The city could see up to three inches of snow on the ground by New Year's Day.

Snow in Las Vegas is rare, but they've seen bigger and more photogenic snows than the one predicted this week. Since the airport began keeping records in the early 20th Century, the city has recorded measurable snow (≥ 0.1 inches) 29 times, with the most recent snowfall occurring on December 17, 2008 (3.6 inches). The greatest snowfall recorded at the city's airport was a whopping 7.4 inches, seen on January 31, 1979.

Sitting a little over 2,000 feet above sea level, Las Vegas' relatively low latitude, dry atmosphere (it is the desert, after all) and prevailing weather patterns prevent the city from seeing as much snow as it could. When storm systems bring precipitation to the area, the tropical moisture that feeds the storm from the south often prevents atmospheric temperatures from dipping low enough to cause a changeover from rain to snow.

What's different this time? A very sharp trough over the Intermountain West will help to develop an upper-level low that will usher colder-than-normal temperatures into the area. Lows in Las Vegas will dip down to or below freezing during the event, allowing any precipitation that falls to reach the ground as snow instead of a cold, wet rain.

According to the National Weather Service office in Las Vegas, forecasters are confident that a storm will form and temperatures will drop to or below freezing, but they have low confidence in how much moisture will accompany the storm. The solid majority of busted snowfall predictions fall through because of a lack of precipitation. Often when we see a promising snowstorm form on the models, the precipitation will have to work through some pretty dry air before it starts to fall. The rain and snow has to moisten the lower levels of the atmosphere before it reaches the ground. Sometimes this takes much longer than predicted and sometimes the atmosphere never moistens, preventing any snow at all.

Assuming that enough moisture is in place to allow precipitation, and it falls as snow over Las Vegas, meteorologists predict that the city could see up to three inches of the white stuff by Thursday morning. In anticipation of even a light dusting on surfaces in the heavily-populated tourist town, the local National Weather Service issued a blunt message to residents and tourists, advising them of what to expect if the forecasts come to fruition:

MANY TOURISTS WHO COME TO LAS VEGAS MAY BE UNPREPARED FOR THE TRUE WINTER-LIKE CONDITIONS THIS STORM COULD BRING WITH IT. TRAVEL CONDITIONS COULD BE DIFFICULT - IF NOT IMPOSSIBLE - ON AREA ROADS STARTING TUESDAY NIGHT INTO NEW YEAR`S DAY. SNOW REMOVAL EQUIPMENT IS VERY LIMITED IN THE LAS VEGAS VALLEY ITSELF. PARKING ON ROADS PUTS YOUR VEHICLE AT RISK FOR BEING SLID INTO AND ALSO MAKES ACCESS ONTO STREETS HARDER FOR VEHICLES THAT NEED TO GET THROUGH. IN ADDITION...ANY SNOW...EVEN IF IT DOES NOT AMOUNT TO MUCH ACCUMULATION...WILL MAKE WALKWAYS AND SIDEWALKS VERY SLIPPERY. WEARING SHOES WITH GOOD TRACTION IS RECOMMENDED TO AVOID SLIP AND FALLS.

EVEN IF SNOW IS LIMITED IN THE AMOUNT THAT FALLS...VERY COLD TEMPERATURES ARE EXPECTED IN LAS VEGAS WITH HIGH TEMPERATURES EXPECTED TO BE IN THE 30S ON NEW YEAR`S EVE DAY AND ON NEW YEAR`S DAY. ANYONE WHO PLANS TO BE OUTSIDE SHOULD TAKE PRECAUTIONS TO PREPARE FOR BEING EXPOSED TO NEAR FREEZING OR SUBFREEZING TEMPERATURES FOR SEVERAL HOURS. BRING LAYERS AND DRESS WARMLY.

Much like some parts of the Deep South, this part of the country rarely sees accumulating snowfall outside of the mountains. Neither people nor municipalities are equipped to handle icy roads. If you live in Las Vegas or you're visiting this week, use common sense if you're out and about when roads and sidewalks are slick.

[Images: Dec. 17, 2008 snowfall by Ian Lloyd via Flickr, model image via WeatherBELL]

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