Snow forecasts didn’t measure up in Philadelphia. So what happened?

In a region that has some acquaintance with underperforming snow forecasts — not to mention sports teams — the absence of wintry trauma Monday wouldn’t qualify as shocking.

But by any measure, for Philadelphia and nearby communities on both sides of the river, this would qualify as the first snow bust of the 2019-20 season, further evidence that the atmosphere remains capable of outsmarting computer models and their human interpreters.

Officially, a “trace” of snow was detected at Philadelphia International Airport, and that took some detecting. For the day, a mere 0.02 inches of precipitation was measured officially.

What happened to those unsettling winter storm warnings and advisories calling for perhaps several inches?

Areas to the north and east of the city did see more snow, and Bucks County remained under a winter weather advisory Monday night. Some schools, mostly north of the city, closed for the day or announced early dismissals. In New Jersey, where some areas in the north did get several inches, state government offices closed at noon.

At Philadelphia International Airport, inbound flights were delayed Monday for an average of an hour and 43 minutes, according to FlightAware.com, and the airport advised passengers to check with their airlines.

But the delays were due to low cloud cover rather than snow, and for homebound commuters, roads were wet for the most part and no significant mass transit problems were reported.

Still, it was a messy back-to-work Monday — particularly for meteorologists. The atmosphere appeared to approach new heights of peculiarity, brewing a complex coastal cyclone that delivered snow in tropical-storm-like narrow bands not far from Philadelphia, but didn’t deliver much of anything to the city or its neighbors.

It was a rough day for those beloved computer models. Ironically, the models, said Jake Sojda, a meteorologist with AccuWeather Inc., had performed quite well in capturing the career of a storm that had impacts from coast to coast and was blamed for at least three deaths in Arizona.

But “as it moved into the East, things got complex really fast,” he said. Models correctly saw that the storm would redevelop in the Atlantic and gain a second wind. They also foresaw that it would be quite a complex system that would throw back rain and snow from north to south, the opposite of the usual.

Even the shorter-term, higher-resolution models still had Philadelphia in the snowy cross hairs on Monday morning, and the National Weather Service office in Mount Holly had the entire region under an advisory for 2 to 5 inches of snow, with even more to the north.

However, it was a “tricky forecast,” said Jonathan O’Brien, a weather service meteorologist. And it turned out to be an elusive one.

As predicted, the storm intensified Monday over the Atlantic — generating colder backlash winds from the north — but not as rapidly as expected. That had an effect on temperatures around Philadelphia, where the temperature never got below 35, said Sojda’s colleague Tom Kine.

What’s more, Kine said, the region was in the heart of a “dry slot” that lasted much of the day, with the sun competing with the clouds at times.

“You have a lot of chaos theory at work,” said Sojda. And yes, he said, he did anticipate that meteorologists would be taking some heat for the absence of snow: “That comes with the territory.”

Chaos theory shouldn’t be a big problem around here for at least the next several days.

No precipitation is in the forecast until at least Sunday. Daytime temperatures will crest the rest of the week in the 40s, about what one would expect for the first week in December, chaos notwithstanding.