After first measurable snowfall of the season, get ready for our first inversion


It wasn't much...but it still counts.

Boise picked up its first measurable snowfall on Sunday.

The story was even better in the mountains, where many ski areas picked up several inches of fresh snow. For them, this storm was just what the doctor ordered. Check out the totals:

But for skiers and boarders (and maybe the rest of us), the good news ends there.

Up Next: A Big Pattern Change

Even though the foothills are dusted in a fresh coat of white, we're done with the snow (and any sort of precipitation) for awhile. Why? Because a big shift is happening with our weather pattern that is going to block any storms from coming anywhere close to our area. Like, anywhere close!

Here's what's happening: A strong ridge of high pressure is building into the Pacific Northwest region (notice how the black lines on the above graphic form an upside down 'U' that push all the way into Canada). This hints that a stagnant air mass coming into that's likely planning an extended stay based on long-range forecast data. Because the ridge will become so amplified, cold air will be streaming in from the north/northwest in the coming days. When an inversion sets up, cold air gets trapped in the valleys while warmer than average temperatures settle into the higher elevations.

How this translates to the forecast

For now, plan on sunshine and chilly temperatures! It will be bone dry this week, but as time wears on, I wouldn't be surprised to see patchy fog developing in the valleys overnight and early in the mornings. When inversions become prolonged and/or get stronger, low clouds and stratus are possible through the day, too. *Not to say this is a guarantee this week*, but often, that low cloud deck will stay in place for several days, and will prevent daytime heating, resulting in even colder temperatures. Highs are expected to start in the upper 30's this week, but could cool off into the low 30's by Thursday as inversion conditions get worse. Inversions can also lead to poor air quality in the Treasure Valley and other low-lying valleys.

How long will this last?

Usually, it takes a storm system or strong winds to scour out an inversion, especially a strong one. It's impossible to tell exactly when this pattern will break down, but I think there's the potential for this to carry on for the next 10-14 days. I'm somewhat confident that nothing big is coming in the next seven days, and long-range computer model data suggests that it may be the same story heading int part of next week. It's hard to tell at this point, as confidence is always going to be low beyond the five to seven day mark. But, if this holds true, it would mean little chance for snow in the mountains over the next two weeks.

Stay tuned, and maybe cross your fingers that the long-range models are wrong!

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