Discussion: Southeast Idaho experienced a rare tornado warning tonight. Even more interesting is that this occurred synonymously with winter weather advisory. This is unusual as tornado warnings typically are issued in areas that are under severe thunderstorm or tornado watches. Bannock, Bingham, Bonneville, Caribou, and Teton counties were under a winter weather advisory when a severe thunderstorm became capable of producing a tornado, thus prompting the tornado warning for the previously mentioned counties. Luckily, there have been no reports of a tornado for those areas. In addition, the storm has weakened below severe limits and was thus no longer capable of producing a tornado, allowing the warning to expire. However, the storm is still capable of producing half-inch hail, up to 40 mph winds, and heavy rain, prompting a special weather statement.
Although this storm ultimately failed to produce a reported tornado, this warning is noteworthy because Idaho does not experience many tornadoes annually, since 1954 Idaho has only had 203 reported tornadoes (an average of about 3 to 4 per year). The storm occurring during a winter weather advisory may be unusual, but there is an explanation for this occurrence. That is because a warm front moved through the area during the morning hours, with the southeastern part of Idaho being in the warm sector ahead of a strong cold front projected to arrive during the evening hours. Showers and thunderstorms developed ahead of this cold front during the afternoon when instability was present, allowing these storms to become severe. After these storms dissipate, the threat will then shift to a low pressure system which will move into the area early Monday morning which will bring colder air and measurable snowfall (3 to 6 inches) to areas above 7000 feet with locally heavier amounts possible. Thus, replacing the severe weather threat with the threat of winter weather conditions. These storms will make travel difficult, so people in the affected areas should be prepared to proceed with caution tomorrow.
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~Meteorologist Noah Hardy