Driving up Highway 93 toward the Montana-Idaho border feels like entering a different world. One minute you're in the valley, and the next, you're staring at a wall of white. Honestly, lost trail pass weather is kind of a legend around here, and not always for the reasons you’d think. People assume it’s just "mountain cold," but it’s way more localized than that.
It's 28°F right now at the pass. The sun is down, and the sky is partly cloudy. You’ve got a light breeze coming from the south at about 3 mph, which doesn't sound like much until you're standing at 7,012 feet. Humidity is sitting heavy at 80%. That’s that "damp cold" that gets right into your bones if you aren't wearing the right layers.
Why the Bitterroot Crest is a Weather Magnet
The geography here is basically a giant trap for moisture. When storms roll in from the Pacific, they hit the Bitterroot Mountains and just... dump. This is why the ski area often has snow when Missoula or Salmon are bone dry.
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Today, Sunday, January 18, we’re seeing a high of 38°F. That’s actually pretty warm for mid-January. The low tonight will dip to 20°F under clear skies. If you're driving the pass tonight, watch for "black ice" in the shadows. The transition from a 38-degree sunny day to a 20-degree clear night is the perfect recipe for melt-refreeze on the asphalt.
Tomorrow looks a bit different. Monday, January 19, brings a high of 42°F. It’ll be partly sunny, but the clouds start rolling in thick by evening. We’re looking at a 10% chance of snow tomorrow night. That’s just a dusting, really, but in the mountains, a "dusting" can turn into a localized squall in about ten minutes.
Breaking Down the Week: Snow is Coming
If you're looking for the real powder, you have to wait until the end of the week. Most people check the valley forecast and think they’re good. Huge mistake.
- Tuesday (Jan 20): Sunny, high of 39°F, low of 22°F. Very similar to today. Great for visibility if you're hauling a trailer over the summit.
- Wednesday (Jan 21): Partly sunny with a high of 40°F. The southwest wind picks back up, though only at 2 mph.
- Thursday (Jan 22): Mostly cloudy all day. High of 41°F. This is the "calm before the storm" day.
The pattern shifts hard on Friday, January 23. We’re expecting snow showers to start in the morning and continue through the night. The high will stay around 40°F, but that 25% chance of nighttime snow is when the accumulation starts getting real.
By Saturday, January 24, the wind kicks up to 7 mph from the west. Snow showers are much more likely (35% chance). This is when the lost trail pass weather really shows its teeth. Visibility usually drops significantly during these Saturday afternoon transitions.
The "Powder Thursday" Myth vs. Reality
Locals talk about "Powder Thursday" because the ski hill is closed Monday through Wednesday. This allows the snow to stack up untouched. But looking at the current data, the best conditions for the upcoming week are actually looking like next Sunday or Monday.
On Sunday, January 25, we’re looking at a 25% chance of snow showers with a high of 43°F. It’s a bit warm, so the snow might be that "Sierra Cement" style—heavy and wet.
Monday, January 26, actually looks warmer with a high of 46°F. That’s high for the pass. You might see some rain-snow mix at the base while it stays pure snow at the summit. If you’re skiing, that means your wax choice is going to be a nightmare.
Driving the Pass: What You Need to Know
Driving over Lost Trail isn't like a cruise on the interstate. The Northwest wind can whip across the road near the summit even when it’s only 2 mph in the trees.
Keep an eye on the northwest winds predicted for today and Tuesday. Even a 5 mph wind at the summit can create "ground blizzard" conditions where the snow on the ground starts swirling and cuts your visibility to zero.
Survival Tips for the Summit
- Check the South Wind: Currently, it’s coming from the south at 3 mph. South winds often bring in that slightly warmer, moisture-heavy air.
- Watch the UV: Even though it’s only 1 today, the reflection off the snow can fry your eyes. Wear polarized glasses.
- Tire Pressure: The jump from 46°F yesterday to 20°F tonight will make your tire pressure light pop on. Don't panic, it’s just the physics of cold air contracting.
Basically, the next few days are going to be "bluebird" days—lots of sun, clear roads, and easy travel. But starting Friday, you better have your winter gear in the trunk. The humidity is going to stay high (70-80% range), meaning any snow that falls is going to be sticky.
Actionable Advice for Your Trip
If you are planning to cross the pass or hit the slopes, Tuesday is your best "safe" travel window with clear skies and a 39-degree high. If you want the fresh stuff, aim for the Saturday/Sunday window, but make sure your defrost is working perfectly.
Keep a close eye on the Friday night transition. The jump from 10% precipitation on Thursday to 25% on Friday night is usually when the road surface gets unpredictable. Pack an extra layer for that 20°F low tonight. Stay safe out there.