WeatherWhys: Slick roads, a sunny Saturday and light at the end of the inversion tunnel
If you’re waiting for a nice blue sky in the Boise area, there’s light at the end of the tunnel.
But we’re not there just yet.
In this week’s WeatherWhys, Idaho News 6 Chief Meteorologist Scott Dorval walks through the small storm system that’s briefly breaking up the inversion that set in last week, what that means for the upcoming week and when the Treasure Valley will finally say goodbye to the current inversion conditions.
Slick roads and a sunny Saturday
For the first time in over a week, snow returned to the Treasure Valley on Thursday afternoon. That led to slick roads in some spots throughout Friday morning. But it could have been a lot worse.
Friday morning’s slick roads came as a result of what could be considered a “flash freeze.” Any moisture in the form of snow and rain that came through the area late Thursday was followed by a cold front around 3 a.m.
The cold front brought a quick temperature drop that froze any precipitation on the ground, creating dangerous driving conditions Friday morning.
“It’s not a freezing rain situation. But some call it a flash freeze,” Dorval said. “You get that when you have snow and slush, and all of a sudden, the temperature drops like a rock and then everything just freezes.”
Freezing rain would have been a lot worse.
Freezing rain, which the Treasure Valley doesn’t get often, occurs when a snowflake forms and passes through a warm layer of air before hitting cold surfaces and immediately freezing. This happens much more often in the Midwest or Portland area and can result in thick layers of ice on walkways, power lines and trees.
The Treasure Valley often has a thick enough cold layer near the surface where rain will re-freeze into pellets and bounce on contact with the ground.
What Thursday’s snowstorm has done, though, is clear out inversion conditions in the Valley — at least for the time being.
“This is cold air coming down from the north, which will stir up the inversion a little bit and hopefully clean it out a little bit more,” Dorval said.
That’ll result in a sunny Saturday, before low-level clouds and fog move back into the area next week and inversion conditions settle back in the Valley.
The return of the inversion
An inversion is when warm air sweeps over the region, and cold air that was already permeating the area drains into the valleys. (The Idaho Statesman published a more in-depth explanation last week, when the current inversion settled into the area.)
Once an inversion does settle in, the Boise area sees very little variety for weather.
That’s what we’re going to get next week, with high temperatures between 34 to 38 degrees and low temperatures between 20 and 26 degrees.
But there is reason to check back in for next week’s WeatherWhys. Three storm systems will sweep through the area as we head into February, with all three potentially bringing snow to the Valley.
“The inversion should be gone,” Dorval said. “As we get towards the end of the month, we finally change the weather pattern and it looks like snow is going to return to the Treasure Valley.”
