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Monsoon Flood Threat in the Southwest; Hot in the South and Northwest

Monsoonal heavy rain will continue flash flood potential across the Southwest and Intermountain West to the central and southern Rockies through this weekend, especially in complex terrain, burn scars, and urban areas. Excessive heat and humidity with heat indices over 110 degrees will be common over much of the Deep South and interior Northwest this weekend. Read More >

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On December 24, 2009, the ingredients for a powerful winter storm converged on the Southern Plains. Cold air deepened from the north, Gulf moisture increased from the south, and low pressure intensified rapidly, leading to severe, blustery winds. With the storm developing so quickly, the atmosphere responded with very strong lifting and heavy precipitation. Rain changed to sleet and then snow, resulting in the most widespread blizzard conditions to affect Oklahoma and Western North Texas in decades.

The record setting storm produced 4 to 8 inches of snow across Wichita Falls up through Oklahoma City and Stillwater as seen in Figure 1. Local snow totals exceeded ten inches, including the most snow ever recorded in a single day at both Oklahoma City and Wichita Falls. For several hours, winds sustained at 40 mph and gusting to 60 mph created whiteout conditions with visibility of less than 100 feet. The winds built snow drifts at least three feet deep, and many vehicles had to be abandoned after becoming stuck in the snow. The number of stalled cars littering the roads and highways made travel impossible even for vehicles better equipped for travel in the snow.

Figure 1: Storm Total Snowfall Amounts for the December 24, 2009 Christmas Eve Blizzard
Figure 1: Storm Total Snowfall Amounts for the December 24, 2009 Christmas Eve Blizzard

While some winter storms are predictable days ahead of time, the full brunt of the Christmas Eve Blizzard was not recognizable until the hours leading up to and during its onset. The evolution and intensity of most storms is sensitive to the timing and strength of key features. This storm appeared to be even more sensitive than most, as was reflected in the wide range of plausible outcomes forecast by numerical models and human forecasters in the days leading up to the event. It was first thought that there would be much wind and cold, but only a few hours of precipitation, some of which would not be snow.

By the morning of the 23rd, it appeared the storm would last a bit longer and produce more snow, and the National Weather Service in Norman issued a Winter Storm Watch for central and northern Oklahoma. Later that day, however, satellite loops and observations provided evidence that the storm was tracking even slower and farther south. The NWS Norman upgraded the watch to a Winter Storm Warning for 4 to 6 inches of snow and strong winds. The Warning was soon expanded to include the rest of the NWS Norman forecast area, some 12 to 18 hours before the worst of the storm arrived. Expectations continued to increase early the morning of the 24th when the NWS Norman raised forecast snowfall amounts, predicting widespread 4 to 8 inches from southwest to northeast, and a sizeable swath of 8 to 11 inches embedded in parts of central and southern Oklahoma.

Forecasters then watched as the storm system moved out of the Southwestern United States and a pronounced low pressure center formed in north Texas. Just north of the low, in western north Texas and southwest Oklahoma, rain transitioned to freezing rain, sleet, and then snow. In the pre-dawn hours, the low pressure alone caused winds to increase above 35 mph with gusts above 50 mph. Then after sunrise a strong arctic front dove in from the northwest, carrying with it rapidly falling temperatures and severe winds.

Recognizing the life threatening conditions that were about to occur, the NWS Norman upgraded its Winter Storm Warning to a Blizzard Warning - a rare occurrence - to highlight the fact that an unusual life-threatening event was unfolding. A blizzard represents some of the most dangerous weather conditions that can occur anywhere on earth. Winds gusted up to 60 mph from midday through the afternoon, and wind chill temperatures dropped to between zero and ten degrees above zero. Blizzard conditions affected the vast majority of northern, central, and southwest Oklahoma, and all of western north Texas, for at least 5 to 7 hours. Commerce was shut down, and nearly all forms of travel were brought to a standstill.

Gusty winds and blowing snow continued to reduce visibility well into the evening, but precipitation finally diminished from west to east as the mature storm exited into Arkansas and Missouri. In fact, clear skies were observed in Oklahoma and western north Texas only hours after precipitation had ended. More work is needed in order to place the Christmas Eve Blizzard in historical perspective, but events such as this are rare in the Southern Plains, and even rarer outside of northwest Oklahoma. This storm produced some of its heaviest snowfall near Oklahoma City and Wichita Falls.

The impacts of the storm were significant. There were at least nine fatalities in Oklahoma related to the blizzard, and hundreds of injuries. Interstates 35, 40 and 44, as well as the turnpikes, numerous roads and highways were shut down during the height of the storm. The National Guard was called in to rescue stranded motorists, and hundreds of people spent Christmas Eve night in one of the numerous emergency shelters set up across the area. Hundreds of abandoned vehicles littered interstates, highways and even local streets for days after the blizzard. Airports closed, leaving many holiday travelers stranded. Numerous power outages were reported. You can see more details on the storm's impacts at  the Oklahoma Department of Emergency Management's website.

Many people who ventured out in the storm escaped with their lives, but some were not so fortunate. It is important to note that even after becoming stuck during a blizzard, it is still safest to remain with your vehicle until a rescue vehicle is able to drive you to shelter. Your car offers protection from bitter cold wind chill temperatures, and someone wandering, even in familiar territory, can become disoriented during blizzard conditions. In the Northern Plains, where people are more accustomed to blizzards, most people carry a survival kit that includes, among other things, blankets, non-perishable and high energy food such as granola bars, and a brightly colored flag to tie to the car’s radio antenna as a distress signal. Of course the best way to stay safe is to stay home until the storm has passed. But for more information on surviving dangerous winter weather, visit