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- Salt Lake City reached 67 degrees on Wednesday, breaking a 1939 record by 9 degrees.
- Strong downslope winds from the Oquirrh Mountains contributed to the temperature spike.
- Gusts reached 51 mph at the airport and 65 mph at the University of Utah.
SALT LAKE CITY — This month figures to be one of Salt Lake City's warmest on record as its running average temperature on Wednesday is just a tick below a record set over a century ago.
A meteorological phenomenon is partly behind the newest addition to the city's record book: a new daily record that soared well above forecast.
The city's official thermometer near Salt Lake City International Airport surged to 67 degrees Fahrenheit on Wednesday, breaking the city's previous record by 9 degrees, as "localized" downsloping winds from the Oquirrh Mountains reached the city, National Weather Service meteorologists said.
Basically, the cold front strengthened as it approached the Salt Lake Valley, picking up warm air from the south that caused warm temperatures, KSL meteorologist Devan Masciulli explains. She adds that warmer air from above the temperature inversion that had set up in the valley may have also factored into this.
"I imagine some of the downslope that came off the Oquirrhs also helped temperatures soar even further in that short amount of time because, in an inversion, the upper atmosphere is warmer than we were here in the valley floor," she said.
At the same time, the system appeared to be stronger than models had initially expected. The weather service had already issued wind advisories and high wind warnings ahead of the cold front's arrival, but wind gusts were stronger than forecast, bringing more of the warmer air.
Gusts peaked at 51 mph at the airport, but gusts reached 65 mph at the University of Utah. Gusts ranged from 70 mph to 90 mph in the mountains, too, according to weather reports.
Salt Lake City had already broken its daily record before the event, surpassing a 58-degree day reported on Dec. 17, 1939, by 10 a.m., according to airport station weather data. But the temperature jumped from 59 degrees at noon to 67 degrees at 12:54 p.m. as the winds picked up ahead of the cold front.
"I think it was a little bit of the right ingredients coming together at the right time," Masciulli said. "Were we really expecting to go that high? No, but we weren't expecting the winds to be so strong with this cold front. And, the stronger the winds, the stronger the temperature difference."
Salt Lake City's temperature plummeted back down to 48 degrees by 1:35 p.m. as the cold front swept through. It also brought valley rain and mountain snow as expected. Radar picked up instances of lightning, too, indicating thundersnow within parts of the Wasatch Mountains.
Wednesday's high was also 29 degrees above the daily normal and 15 degrees above Tuesday's high, falling 2 degrees short of the city's all-time December high of 69 degrees, set on Dec. 1, 1995.
Salt Lake City entered Wednesday with an average monthly temperature of 41.8 degrees, 0.1 degrees below its December record set in 1917. Its record book was established in 1874.
