AUSTIN (KXAN) — Overnight, Austin received nearly three times the amount of precipitation it took to shut down the entire city during an icing event last January. But only elevated roadways, mainly north and west of town, saw problems. So what went wrong with the ice predictions?
The answer has to do with the timing of the temperature drop behind the arctic cold front versus the timing of the precipitation that fell.
During the January 28, 2014 ice storm, Austin only received 0.05″ of precipitation–but it fell while the temperature was 27 degrees. This quickly created a coating of black ice on area roadways, stranding school buses and commuters alike.
This morning, the temperature drop came after the 0.13″ of rain had already fallen. Light rain was observed at Camp Mabry (Austin) from 11 p.m. until 2 a.m., but the rain shut off for the day from 3 a.m. onward.
The temperature didn’t drop to–then eventually below–32 degrees in town until 4 a.m. Dry north winds quickly evaporated roadway moisture and most areas were left ice-free.
Forecasting ice on the Hill Country Escarpment is always a game of inches, as one degree can make the difference between a hazardous commute and simply wet roadways.
The Balcones Escarpment is a geologic fault zone along the edge of the Hill Country. Mount Bonnell and much of Austin lies on this fault. Forecasting borderline temperature situations in this area is especially difficult because it’s exactly where cold, Arctic air filtering in from the north is often moderated by warmer, more moist air that flows from the Gulf of Mexico up the plains east of I-35.