Sunday’s snowfall took the Treasure Valley by surprise. Here’s what to expect next.

We knew the Treasure Valley would wake up Sunday covered in a blanket of snow, the first flurry of the season. But even forecasters were blindsided by just how much fell overnight.

Stephen Parker, a meteorologist with the National Weather Service in Boise, said early predictions called for an inch or so of snow in Downtown Boise. By noon Sunday, about 3 or 4 inches had fallen Downtown, Parker said, and the official measure at the NWS’s office near the Boise airport was 3.3 inches — and growing.

“Since about 9 o’clock this morning, (our models have) been saying it will stop around 1 p.m., and it’s still coming down,” Parker told the Statesman in a phone interview. “Each little bit extra is like salt in the wound.”

Parker said the NWS uses between 12 and 15 modeling tools to forecast weather. None of them showed this amount of snowfall, a discrepancy that Parker estimated happens only once every two or three years. What’s more, he said, is that models predicted only 1 to 2 inches of snow in Mountain Home, which was walloped by 8 to 10 inches Sunday.

“That (level of forecast inaccuracy) only happens about once every five years,” Parker said.

NWS meteorologists are still working to figure out exactly what caused the predictions to go so awry.

“It’s as frustrating to us as it is to everyone else,” Parker said.

For the coming week, though, Parker said cold temperatures should help the snow stick around. Monday’s high will hover around freezing, and temperatures may not rise above 32 degrees until next weekend.

He cautioned that afternoon highs could cause a bit of snowmelt on Sunday, which might create black ice on sidewalks and roadways for the Monday commute.

And while the inches of snow may have given some Boiseans flashbacks to the “Snowpocalypse” of 2017, Parker said there’s no reason to start stockpiling emergency rations.

“This is not an indication of what the rest of winter will be like,” he said. “It’s just one storm that overachieved.”

This story was originally published December 2, 2018 at 2:23 PM.