A year ago, storms in December and January turned Portland into nothing less than an apocalyptic scene: Abandoned cars lined snow-clogged streets. Traffic backed up for miles. The city shut down and again turned Portland into a winter punchline.

So when the forecast of a late-season dump of snow arrived for last week, many envisioned another round of chaos.

But when the storms came, with snow falling in spurts from Sunday through Friday, Portland largely shrugged them off.

With salt getting widespread use, some fortunate timing and a more experienced region, mayhem on the roads was limited to a few slippery spots. TriMet bus and train riders mostly got where they needed to be. And kids weren't stranded in school gymnasiums late into the night, like they were last year.

Sure, some buses and trains suffered delays, and some roads were closed or backed up. But by and large, the city made it through like, well, like maybe it knew what it was doing.

Some was experience, some was good fortune. But the combination of factors turned the February 2018 snowstorm into something less than the Snowpocalypse experiences area residents have come to know so well.

Here's what made the difference:

Roads got a hefty dose of salt

The city of Portland and the Oregon Department of Transportation used salt on the roads essentially for the first time.

In years past, the agencies rejected road salt, saying it's an ecological nightmare waiting to happen. Drivers didn't want it anyway, they said, because it would corrode cars.

Never mind that their preferred deicing chemical, liquid magnesium chloride, is a salt whose own ecological impact is not fully understood and which has been shown to weaken concrete bridges from the inside.

In any case, after an outcry from drivers in a December 2016 storm who wondered why Portland couldn't deal with an inch of snow, officials said they would add salt to their bag of tricks.

So last week, it went down. The state Transportation Department spread about 17.5 tons of salt in the Portland area through Wednesday. It applied on Interstate 5 from Oregon 217 to the Fremont Bridge, on U.S. 26 from Oregon 217 to the Vista Ridge Tunnels, and on Interstate 405.

The Portland Bureau of Transportation laid the salt on even thicker. It used 140 tons on some 20 routes over the course of the storm.

The city used salt because it proved to be an effective tool early in the week during its first real test, bureau spokesman John Brady said. He credited salt with the city having just a couple of road closures, and most were brief.

This year's test was a departure from last year, when Portland spread a few truckloads, borrowed from the city of Seattle, on roads already encased in packed snow and ice. Then, officials said it was little more effective than their magnesium chloride.

But this year, when using salt early, they say it clearly made a difference.

"The fact that none of the usual suspects -- Germantown, Skyline, Burnside, Terwilliger, Sam Jackson -- were closed down for a major period of time, I think it's an indication that it turned out to be effective," Brady said.

The timing was right

Unlike last season, Portland had a run of fortunate timing.

The first measureable snowfall of 2018 fell on the Sunday of an extended Presidents Day weekend. The snow didn't last into Monday's commute, and fewer drivers were on the road for the ice that did stick around.

But Tuesday had officials fearing the worst. A snowstorm was brewing, and it appeared posed to strike the metro area in the middle of the workday. There were flashbacks to Dec. 14, 2016, a Wednesday, when snow began to fall at 11 a.m.

Though that storm was expected well in advance, schools were still open, and most people were at work. When the snow started to stick, at once workers began a mass exodus from jobs. Roads jammed, trapping plows in traffic along with everyone else. Stuck cars were abandoned, some smack dab in the middle of travel lanes.

Commutes that would normally take minutes stretched as long as five, six or seven hours. Children were stranded at schools or in school buses for hours.

This year, officials hoped to avoid a repeat. They urged workers to get home early. Experienced school officials scheduled an early release.

In the end, Tuesday's storm didn't materialize until well into the evening, when people were home. Then another round of snow came late Wednesday and ended early Thursday, again giving schools, employers and transportation officials plenty of time to make decisions.

"Any time a storm comes in at night, it makes sure the public is off the road, and it gives businesses the chance to evaluate overnight whether they'll be open," said Don Hamilton, spokesman for the Oregon Department of Transportation.

Hamilton said more drivers -- perhaps learning some lessons from a year ago -- seemed to heed officials' advice to stay home or delay travel. Traffic volumes appeared far lighter than normal and more diffuse through the day.

Buses chained up overnight

The snow's timing helped TriMet as well. As in last year's storms, TriMet fitted all of its buses with tire chains to keep them moving through the storm.

The difference was, unlike last year, they didn't need to pull buses off routes or cancel trips going into rush hour. Instead they were chained up late in the evening or, for the bulk of the fleet, overnight in a garage.

"The challenge this week was the uncertainty with the forecast," spokeswoman Roberta Altstadt said. "You start scrambling one way, and then the snow held off."

Chaining up buses midday is a logistical nightmare. Only a quarter of the fleet of buses on the street on weekdays come back to a garage before the end of service.

The rest have to meet up with mechanics in the field to be fitted with chains. That causes a delay, and then the slower-moving bus falls even more behind.

All that havoc was avoided this year. In the end, buses were chained all day Wednesday and early Thursday.

That proved enough to keep most buses moving, even if more slowly. More than 20 lines were canceled at the height of last year's storm -- mostly because of piles of snow on especially steep and icy routes, which were shut down the longest -- only five were shut down in this one.

And yes, the storm wasn't as punishing

Portland's roughest storm of the 2016-2017 season, which hit in mid-January, started with up to a foot of snow, paralyzing the city from the start. A deep freeze followed, with temperatures that stayed at or below freezing for more than a week.

The result was that snow left on city streets turned into hard-pack, then into layers of ice several inches thick in places. A full week later, drivers still navigated deep ice ruts that had become impervious to plow blades or any amount of de-icing fluid.

This week, by comparison, each bout of snow was short-lived.

Sunday's dusting didn't last through the night, while snow that fell Tuesday and Wednesday gave way to temperatures that climbed above freezing during the day.

"The snow we've had is so much different than what we experienced last year, with the bitter temperatures, the freezing rain and the major amount of snow," Altstadt said. "It's a very different winter."

But this year's freeze-thaw cycle didn't always help. An unexpected drop in temperatures Thursday morning sent cars sliding on bridges and overpasses, where slush had thawed and re-frozen into a sheet of ice. That effectively closed the flyover ramp from northbound Interstate 205 to westbound Interstate 84 for more than an hour before state deicer trucks could treat the roadway, allowing traffic to pass safely.

But at least this year it was treated quickly.

"Mother nature can be fickle," Brady said. "You never know. It can be a friend or foe."

-- Elliot Njus

enjus@oregonian.com

503-294-5034

@enjus