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Photo of weather conditions in Okarche, OK during the winter storm on February 1, 2011. Photo taken by and provided courtesy of Dave Ewoldt.

The Winter Storm of January 31-February 1, 2011

Brief Summary:

After a relatively quiet early winter, a dose of reality, in the form of a major, record-setting winter storm, affected all of Oklahoma and western north Texas on January 31-February 1, 2011. Periods of heavy sleet and snow, combined with winds that gusted over 40 mph, disrupted travel and closed hundreds of schools and businesses. Snowfall totals reached over a foot in some places, with snow drifts reaching three to five foot depths. Temperatures plummeted into the single digits and lower teens, and wind chills fell well below zero. In fact, wind chill values fell below -25 degrees over parts of northwestern Oklahoma! Note: this was a wide ranging winter storm, with even higher totals reported in northeastern Oklahoma and continuing northeastward through Missouri, Illinois, and parts of the northeastern United States.

Leading Up the Event:

Looking at the weather several days before the event, one would have thought that these were the final days of winter and that spring would soon begin. Record high temperatures were common over a large area on the 28th and 29th of January, with readings well into the 70s.

Unfortunately, these warm, mild days came to an abrupt end as a strong cold front moved southward over the southern Great Plains on January 30th, reducing high temperatures to 30 to 40 degrees cooler than the previous day. Max temperatures only reached the 20s across northern Oklahoma, with highs in the 30s prevailing across the southern two-thirds of Oklahoma and into north Texas. However, this was a relative heat wave considering what was to occur just two days later.

Late on January 29th, a strong storm system finally moved onshore over southern California. At the same time, an arctic cold front began its trek south through the northern Great Plains, with a 1052 mb surface high pressure building in behind it. Although confidence had increased to a point where forecasters had concluded that a winter event was going to occur over the southern Plains, the timing and strength were still somewhat in question.

With the system now onshore, most of the numerical models had converged onto a solution that a significant winter storm would affect parts of Oklahoma and north Texas. The models indicated that several inches of snow were likely, and would be accompanied by strong northerly winds gusting over 40 mph. Forecaster confidence was high enough now that by a Winter Storm Watch was issued for portions of central, northern, and eastern Oklahoma at 4 AM on the January 30th.

As more data poured in over the next 12 to 18 hours, the Winter Storm Watch was expanded to include all of the WFO Norman, OK county warning area except for two counties in southeastern Oklahoma (Atoka and Bryan were in a Winter Weather Advisory). Counties in central and northern Oklahoma were upgraded to a Blizzard Warning, with the anticipation of 8 or more inches of snow, frequent wind gusts of 40 to 50 mph, and visibilities falling to less than ¼ of a mile.

The Event Begins:

The freezing line at the surface slowly moved south during the day on the January 31st, lying across the northwest half of Oklahoma by sunset and then advancing quickly southeast. At the same time, the storm system was moving through New Mexico with increasing lift out ahead of it.

 Regional Weather Conditions at 6:37 pm CST on January 31, 2011

Thunderstorms, some containing heavy sleet, developed over parts of west Texas and moved northeast over northern Texas. By this time, some of precipitation was developing and moving over sub-freezing surface temperatures. The precipitation coverage expanded through the evening hours toward Lawton and Oklahoma City. Periods of heavy thunder-sleet, occasionally mixed with freezing rain and heavy snow, were reported up and down I-44 toward OKC by 10 pm, with a light glaze of ice developing on elevated surfaces, and sleet accumulations of 1 to 2 inches over some areas of central Oklahoma. By 1 AM, temperatures were at or below freezing over all but far southeast Oklahoma.

With the cold air deepening above the surface, the precipitation was falling as snow across western and northwest Oklahoma, with a mixture of sleet and snow over southwest and central Oklahoma, and northern Texas, and freezing rain and sleet over southern Oklahoma. By 4 AM, all but southeast Oklahoma was reporting snow, with moderate to heavy snow bands setting up over western and central Oklahoma. The temperatures also continued to fall, with temperatures ranging from near 10 degrees over northern Oklahoma, to the lower to middle 20s over southeast Oklahoma, and the teens in between.

The Event Continues:

The snowfall was moderate to heavy at times, with some areas from central into northeast Oklahoma reporting snowfall rates of 2-3 inches per hour. By sunrise, around 6 inches of snow had fallen from Norman and Oklahoma City northeast toward Shawnee and Chandler, and the heavy snow continued to fall in parts of central Oklahoma.

Regional Weather Conditions at 8:30 am CST on February 1, 2011

In addition to the snow, the winds gusted at 35 to 45 mph, and temperatures fell into the single digits and lower teens. Rush hour traffic, at least what traffic there was with most schools and businesses closed, was very slow going. Visibilities with the heavy snow and strong winds were falling below ¼ mile, resulting in numerous accidents and stalled automobiles. The wind chills became just as big an issue by this time, with wind chill values falling below -15 degrees.

By mid morning, the heaviest snow bands had pivoted into eastern Oklahoma, but areas of moderate snowfall were still moving east through western and central Oklahoma. These bands still produced snowfall rates of 1 inch per hour over central Oklahoma. The snow finally ended from west to east by early afternoon, but the wind speeds remained strong with frequent gusts over 40 mph still occurring. Even after the snowfall had ended, near blizzard conditions continued through the afternoon, which hindered snow removal on roadways, and slowed rescues from stalled cars and accidents.

After the Event:

By the evening, the temperatures had dropped into the lower single digits over northern Oklahoma and into the lower teens over southeastern Oklahoma. Although the winds had calmed somewhat, wind chill values were still well below zero. In addition to a Wind Chill Advisory, the Oklahoma Department of Emergency Management requested the issuance of a Civil Emergency Message highlighting the dangerous weather conditions for those that had become stranded in their cars and hadn’t been rescued yet. Very little recovery occurred on the February 2nd, as daytime temperatures only rose into the teens. The winds continued to slowly decrease, but wind gusts near 30 mph were still common.

Impacts:

Unfortunately, four deaths were reported as a result of the winter storm, with one death occurring in Moore, and three in Miami, OK. The Oklahoma Highway Patrol reported over 150 automobile accidents statewide, ten of which resulted in injuries. There were also over 460 motorist-related calls, mainly from people that had become stranded in their vehicles. The situation could have been worse, but schools and businesses had closed prior to the beginning of the winter storm, which kept traffic at a minimum for much of the day on February 1st. In addition, the winter storm mainly produced snow and sleet, and freezing rain was less widespread and fell in shorter durations. As a result, ice accumulations were kept at a minimum, reducing the number of power outages across Oklahoma.

Historical Perspective:

Much of the southern Plains had enjoyed a quiet winter up to this point, which made this seem even more significant. There had been a few intrusions of arctic air, but the events were generally short lived and moved off toward the east after a day or two. Precipitation had been almost non-existent, and drought conditions had begun to take hold over parts of central Oklahoma. The liquid equivalent amounts generated by the snowfall totaled between 0.50 inches and 1 inch, and amounted to roughly half of the average February precipitation totals for the region. These precipitation totals should help somewhat to alleviate the D2 drought over central Oklahoma.

The official snowfall observation at Will Rogers World Airport in Oklahoma City was 12.1 inches. Most of the snow fell on the February 1st with when 11.8 inches was recorded, with the other 0.3 inches falling during the late hours of January 31st. The 11.8-inch total broke the calendar day record, which was previously 5.5 inches set in 1913. The total also broke the all-time February daily snowfall record, which was previously 6.5 inches set in 1987.

Looking at the bigger picture, 12.1-inch total tied February 5-7, 1988 for the 2nd highest storm total snowfall. It wasn’t that long ago when Oklahoma City had recorded its greatest storm total snowfall. Just 13 months ago, last minute Christmas shoppers were greeted with a record-setting blizzard that accumulated 13.5 inches of snow. More information regarding this event can be found here. A 3.0-inch total reported at Sheppard Air Force Base in Wichita Falls, TX also tied a record set in 1905 for the most snowfall to occur on February 1st.

Preliminary Storm Total Snowfall Amount Map for the January 31-February 1, 2011 Winter Storm


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