by Doc Deason
(KYTX) - The ice storm that East Texas experienced Sunday was one of the more intense episodes in my recent memory, reminiscent of the New Year's Eve storm of 1978.
Even as a 5-year-old, I remember leaving a late-night service at church that night and making the trip to Dallas for the infamous Cotton Bowl game featuring Joe Montana and Notre Dame vs. the University of Houston (my dad's alma matter).
The fallout from that storm's massive power outages led to the practice of trimming trees near power lines that we still see today.
A lot of people have asked just what happened to bring Sunday's winter storm together, especially since there was not a whole lot of fanfare or concern for significant winter weather leading up to the event.
Leading up to Sunday, we knew it would be a wet day. By the middle of the week, it had become apparent that colder air would accompany the rain. However, the speed of the cold air's arrival and the intensity of the cold was (as is usually the case across East Texas) somewhat in question.
Arctic air masses are usually very shallow by the time they get down to our latitude
For example, it may be 25 degrees at the surface, while being much warmer at 2,000 to 3,000 feet aloft.
And, due to that weakness, the computer models that help in forecasting temperature have a very hard time handling these outbreaks.
They usually understate the amount of cold air that we will see. The shallow nature of the air mass also makes it susceptible to being "Dammed-Up" by the Ouachita Mountains, in Southeast Oklahoma, which is where the issue of timing its arrival into East Texas becomes anyone's guess.
Arctic fronts are notoriously late in arriving due to the effects of these mountains, and this is a constant concern for those of us forecasting. This has led to many "busted" forecasts for winter weather in the past since the necessary cold air was delayed, even though the moisture was right on time.
There were some hints in the model data on Saturday night that this, in fact, could be a more significant winter weather event.
The concern was primarily for elevated objects, since rain and sub-freezing temps were expected during the evening. With most areas having seen temps in the upper 70s on Saturday, and the expected winter weather mode being freezing rain, there wasn't much concern about the major thoroughfares icing up.
The problems were:
1.) The trajectory of the incoming air was such that it was able to sneak around the western edge of the mountains in Southeast Oklahoma.
2.) The cold air arrived several hours ahead of schedule, creating a favorable environment for sub-freezing temps quicker than expected.
3.) The cold air was deeper than anticipated, and this led to the rampant development of sleet.
The intensity of the sleet and the cold already in place was enough to overwhelm even the warm ground temps that were already in place.
This led to the rapid accumulation of ice, which was further assisted by the presence of freezing rain.
Sleet has always been a "wild card" in forecasting winter weather since enough of it can lay a foundation for further ice accumulation on top of whatever does not initially melt.
This was the mechanism that caused all the havoc Sunday.
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