December 2006 brought one of the most historic winter weather events in the state's history. Back-to-back blizzards struck the foothills and eastern plains of Colorado during one of the busiest 10 days of the year.

It all started with a strong storm system slamming into Washington and Oregon with torrential rain and hurricane-force wind. Once onshore, the storm split into two pieces. One moved into southwestern Canada and the other slid down the Great Basin and settled into Arizona.

Forecasters in Denver had their eye on this storm as it hit the Pacific Northwest, and computer forecast models showed the potential for a major winter storm across eastern Colorado just before Christmas. But would it really happen?

Computer models sometimes become aggressive and forecast too much. In addition, simple climatology states that a major winter storm in the middle of December just isn't that common. In fact, it had been more than two decades since a snowstorm big enough to paralyze eastern Colorado and a major city like Denver hit during the Christmas holiday.

By Saturday, Dec. 16, the area of low pressure continued to sit and spin over Arizona, orphaned from the main flow of jet stream winds aloft. It was a prediction predicament because all signs pointed to it slowly moving east-northeast, tapping into plenty of moisture from the Gulf of Mexico and gaining strength. The million-dollar question was would it really happen and if so, when?

With the peak of Christmas travel underway, thousands watched each forecast with anticipation of what was going to happen. By Tuesday, Dec. 19, the details became clearer with each new set of weather data: eastern Colorado faced a major winter storm that had the potential to paralyze holiday travel.

While heavy December snowfalls are not that common, they can happen. One of the most noted events was in December 1982, as 2 to 4 feet of snow blanketed Denver and the Front Range on Christmas Eve. That storm stopped all travel and stranded thousands. Many retail workers were stuck in their stores on Christmas Eve and were forced to make the most of the situation until the snow tapered off on Christmas Day.

Soon the watches and advisories were posted, and by noon on Wednesday, Dec. 20, snow began to fly in the Denver area. It began falling as early as 8 a.m. in the foothills west of town. Snow fell along with gusty north winds for the next 24 to 36 hours, leaving much of the Front Range under 1 to 3 feet of snow.

Heavy snow even fell across the eastern plains during the event, with as much as a foot in Washington, Logan, and Phillips Counties. Southeastern Colorado saw amounts generally between 6 and 12 inches. Gusty winds in excess of 30 mph drifted the snow between 4 and 8 feet deep in exposed areas just to the east and south of Denver.

The storm made national headlines as it closed Denver International Airport for two days, canceling some 2,000 flights and ruining the holiday travel plans for thousands of travelers connecting through, flying to, or flying from the Mile High City.

As the storm exited Colorado and the recovery process began, forecasters were busy tracking a second storm system following almost the same path as the first. Historically, two snowstorms, each having the capability to paralyze and stop a major city like Denver, were virtually absent from the weather record. The only documented event that could compare was the great storm in December 1913.

Although through the years, the 1913 storm has been characterized as one single event, it really came in two distinct waves of heavy snowfall. In that year, a storm moved through eastern Colorado, dropping 1 to 2 feet of snow on Dec. 1 and 2. On Dec. 4, a second system moved through, dropping 3 to 5 feet of additional snowfall on the region. Denver's total snowfall from that historical event was 45.7 inches, which remains the largest five-day snowfall in history. In the mountains and foothills west of Denver, over 80 inches of snow fell. Georgetown recorded 63 inches of snow alone on Dec. 4. Transportation came to a standstill as gusty winds drifted the snow several feet deep.

By Dec. 27, 2006, a new round of winter storm watches was in effect for places still digging out from the first storm. By noon on Thursday, Dec. 28, the snow was flying across eastern Colorado, Denver, and the foothills.

At first the snow rates were light, with rain mixed in across parts of the northern Denver Metro area, from Longmont to Firestone and extending into northeastern Colorado around Greeley. But in time, the snow filled in and the intensity picked up. By 7 p.m. on Dec. 28, numerous phone calls and e-mails flooded 7NEWS with reports of thunder and lightning in the northwest Denver Metro area and northern foothills. One caller from Arvada was outside shoveling when the thunder and lightning began, and she ran inside fearing for her life.

Thunder-snow is simply a thunderstorm that drops snow instead of rain. It is a sign of a very unstable atmosphere and usually indicates heavy rates of snowfall, on the order of 2 to 4 inches per hour in many cases. That is exactly what happened with the second of the twin holiday blizzards.

Communities from Lakewood to Golden and Evergreen to Estes Park picked up 2–4 inches of snow per hour for several hours.

By Friday morning, the snow tapered off to showers in the foothills and the Denver Metro area as the energy shifted onto the southeastern plains, but not before dropping another 1 to 3 inches on the area. There was still a distinct possibility that the storm could fling more snow on Denver and the Front Range area later in the day and possibly through New Year's Eve. Everything depended upon the movement of the low pressure system centered on southwestern Kansas.

If that low tracked due north, the snow would likely wrap around the system all the way back to Denver. The local terrain effects of the foothills and the Palmer Divide would serve to focus very heavy snowfall on the western and southern sides of the metro area, perhaps bringing several more feet of snow along with extreme blowing and drifting. If the low pressure center of the storm moved to the northeast, the brunt of the storm's fury would shift to the eastern plains and western Kansas. The outcome of the storm's path was not obvious until late in the day Friday, when weather warnings were lifted for the Denver area and the eastern plains braced for a terrible winter storm.

While Denver and the foothills began the recovery process, it was only beginning for residents of eastern and southeastern Colorado. Moderate to heavy snow fell, while winds sustained at 30 mph gusted to over 50 mph at times. This continued for 36 hours as the area of low pressure slowly moved to the northeast over Kansas. By New Year's Eve the low was far enough east of Colorado that conditions improved for the eastern plains. However, the damage had been done. Residents found themselves buried alive in their homes.

Drifts as high as the rooftops blanketed homes and farm buildings; 12 to 36 inches of snow had fallen during the storm, heaviest across the southeast counties. Drifts were measured at 10to 15 feet deep, and up to 18 feet deep east of Sheridan Lake in Kiowa County. Thousands of head of cattle were stranded in the deep snow, and ranchers lost many of their herds, right in the midst of calving season. Despite valiant efforts by ranchers and the Colorado National Guard, hay dropping from military helicopters was not sufficient to save many of the lost cattle. Many longtime ranchers and farmers said that the late December storms of 2006 were worse than the October 1997 blizzard and as bad as any storm in memory.

In the mountains and foothills of southern Colorado, 30 to 48 inches of snow were measured from the storm. The storm closed all major roads for days, and smaller secondary roads for weeks. Food supplies ran low at stores once citizens could get out of their homes, and merchants were quite distressed at the timing of the storms, right in the heart of the big retail season.

The twin blizzards of 2006 did bring good news to the water supply, though. Before the storms, Denver was on track to tie the driest year ever recorded, 7.48 inches in 2002. Though 2006 stayed still in the top 10 driest, ranking seventh, the storm brought a widespread 1 to 4 inches of liquid-equivalent moisture to the foothills and eastern plains. It also made for one of the snowiest Decembers on record, ranking just behind 1913 and 1973.