Denver hit 83 degrees on Wednesday afternoon. Eight hours later, it was snowing.What do you wear when you encounter every season within a 12-hour window?
10 October, 2019
Residents of Denver enjoyed a beautiful Wednesday afternoon with temperatures in the lower to middle 80s. During the evening commute, a cold front swung through, bringing strong northerly winds and plummeting temperatures to freezing. Just eight hours after setting the record high for the day, it was snowing. Denver also set a record by midnight.
“That’s our largest one-day temperature change in October on record,” said Russell Danielson, a meteorologist at the National Weather Service in Boulder. “We tell people around here to dress in layers, because sometimes you get summer and winter in the same day.”
That chalks up to a 54-degree temperature drop within one day. It also marks a 40-degree plummet in four hours, the mercury diving from 81 degrees to 41 between 4 and 8 p.m. As the winds switched around from the north, gusts up to 55 miles per hour heralded the bone-chilling front’s arrival.
Temperatures were continuing to fall on Thursday, the National Weather Service forecasting a low of 14 degrees into Friday morning. “The record low is 22 degrees, set back in 1946. We should shatter that record.”
How strong can these cold fronts be?
Cold fronts on the High Plains are notorious for their dramatic and capricious shifts. The dry climate makes it easier for enormous fluctuations to occur, while the lack of water bodies or obstacles means that air masses of the opposite extreme can battle it out over relatively short distances. It’s not unusual for the temperature to fall 30 degrees or more behind a fall or winter cold front.
“Our biggest temperature difference in a singled day was 66 degrees on Jan. 25, 1872,” Danielson said. “We had a high of 46 and a low of minus-20.”
On occasion, it’s possible to get both a drop a leap, sometimes with multiple iterations, in the same day. That’s most common if a stationary front stalls, wobbling back and forth. These stationary fronts can also develop a very sharp gradient.
On Jan. 20, 1943, a stationary front got hung up in the of South Dakota. The thermometer registered minus-4 at 7:32 a.m. Two minutes later, it had spiked nearly 50 degrees to a comfortable 45. Temperatures continued rising during until the midmorning, hitting 54 degrees before a drop to minus-4 27 minutes later. The temperature swings were reportedly so dramatic that motorists’ windshields cracked, the temperature fluctuations stressing the glass driving from a warm pocket to a cold one.