"Why did the pass close?" Common triggers behind winter pass closures and what we do to get the roads back open

 By: Scott Klepach and Lauren Loebsack

You can count on three things to happen every winter in Washington: Long nights, short days and closed passes.

Some mountain passes – like SR 20 North Cascades Highway, SR 410 Chinook and SR 123 Cayuse – close for the season. Others, like I-90 Snoqualmie Pass and US 2 Stevens Pass require year-round work to remain open for winter travelers.

Clear roads ahead on Christmas morning on Stevens Pass.

During the warmer months, Snoqualmie and Stevens crews repair roads, prepare equipment and make improvements from last winter’s wrecks. Once winter arrives, their focus turns to snow and ice operations.

But even with all this preparation, sometimes the weather, avalanche control or crashes cause a pass to close. Let’s look at what causes closures and how crews work to get roads open again.

What triggers a pass closure?

Pass closures happen every winter. In most cases, closures happen because drivers aren’t prepared for the conditions.

“It’s the (drivers) failing to follow traction requirements and speed limits,” said maintenance superintendent Jason Pratt, who has worked 17 winters in WSDOT’s maintenance area 1 in South Central Region, which oversees Snoqualmie Pass. “That’s what causes most of the closures. Our team is the best in the business. We know how to handle a storm.”

Pratt adds that safety risks and traffic issues come from drivers who don’t have good tires, drive too fast or don’t know how to drive safely in snow and ice. Some people ignore the chain-up rules or simply don’t know how to use chains.

In this scene from December 2020, multiple semi-trucks failed to chain up, got stuck and closed Snoqualmie Pass for more than an hour. Closures of this nature happen every winter.

This is also true on Stevens Pass, where weather-related closures are rare. Only three closures in the last five years were due to weather conditions. But that doesn’t mean the pass is always bare. During and directly after snowstorms, roads may have snow or compact snow and ice on the road, which is why it’s important for drivers to be prepared before they head out.

“Usually, we have to close because someone didn’t check the forecast, or thought they could get across the pass on bad tires,” said Aaron Byrd, maintenance supervisor for Stevens Pass. “My advice is check the pass report. We update at 7 (a.m. and p.m.), 11, and 3, day and night. That’s our crew out on the pass, reporting conditions in real time.”

Working quickly – and safely – to reopen

One spin out can close an entire pass for hours. During that time, Incident Response, Highway Maintenance and other first responders and tow truck operators work together to clear vehicles or debris. If there’s a big crash or if material is spilled onto the roadway or waterways, the cleanup can take even longer.

“Our crews work as quickly and safely as possible to reopen a highway,” Pratt said.

We work closely with Washington State Patrol to safely close the roads. Our crews use special trucks called “push pickups” to push vehicles out of the way and to the shoulder. When we need to move a large vehicle like a semi-truck, we need to call in big tow trucks that come from further away, which adds more time.

Crews work from the top of the summit to clear snow, but plows can’t get through if there are vehicles blocking the road. All of this takes time and resources to shift crews to the greatest needed area for storm response.

“This is what crews try to do with vehicles – move blocking vehicles to just try and get traffic flowing again,” said Scott Montgomery, maintenance supervisor at Snoqualmie Pass.

When weather-related closures are necessary, it isn’t a quick process. Our crew “sweeps” the road, traveling the area between the closure points to clear traffic.

On Stevens Passs, we coordinate with the ski resort to assist skiers down the mountain. Depending on the severity of conditions, skiers have had to travel east toward Leavenworth and double back around on US 97 Blewett Pass to get home.

Closure points are staffed, unless it’s expected to be a longer closure – for example longer than 24 hours – in which case, the crew will build a snow berm at the closure points to prevent drivers from trying to sneak through the closure.

Working with the weather

Before a snowstorm, crews might close a pass to conduct avalanche control – which can take from 30 minutes to two hours to complete depending on how much debris comes down.

“Avalanche missions are a delicate balance,” said Harlan Sheppard, North Central Region avalanche supervisor. “(Do them) too often and you don’t get results that are worth the cost, not often enough and it could be tipping over into avalanche danger.”

During avalanche control missions, traffic is held on either side of the summit while crews use explosives to trigger avalanches. The maintenance team follows the avalanche control team, using loaders, blowers and plows to clear the road. Even though the closures can be short, the team typically schedules missions for early in the morning – when there’s usually the least amount of traffic.

Snowplows clear snow from Stevens Pass following an avalanche control mission.

We’ve also installed defensive strategies to keep falling snow off the roads. Across the summit of US 2 Stevens Pass, structures referred to as “passive protection” are designed to lessen the potential for snow slides to reach the highway.

Deflection berms, like the one constructed in 2019 at Tunnel Creek, and gabion baskets such as those installed at East Portal and Tunnel Point are defensive strategies to collect and redirect snow. They also work to catch debris such as rocks that come down year-round.

Once snow begins to fall, crews build snow trenches in areas know to have smaller slides, shaping the piled-up snow on the side of the road into a basin that can then be cleaned out.

Defensive measures have also been implemented at Snoqualmie Pass. As part of the I-90 Snoqualmie Pass East project to enhance the highway between Hyak and Easton, crews constructed avalanche bridges east of the summit, positioned over sections of the road prone to avalanche risk. Instead of allowing snow and debris to fall directly onto the road, the bridges allow the snow to pass underneath, essentially diverting the avalanche away from the highway. This prevents road closures and reduces the risk to motorists. However, avalanche control work is still needed west of the summit.

How can I prepare for winter driving across the passes?

Winter preparation messaging can seem excessive until drivers are in a serious winter storm.

“It’s why you really need to understand and be prepared for winter travel,” Byrd said.

Here’s how you can do your part to be prepared for whatever you encounter during a winter drive across the passes:

1. Be prepared for possible delays and ensure you carry appropriate winter travel gear.
2. Stay informed . Check weather and conditions before you leave and during travel – if you are driving, never check from behind the wheel, pull over to a safe spot or ask a passenger to check. Use WSDOT’s tools to stay informed of conditions and possible closures.
3. Drive for the conditions : Slowing down and leaving plenty of following distance for other drivers and plows help reduce the potential for collisions and spin outs that are the primary reason the pass closes.
4. Carry chains. Requiring chains be installed in certain conditions allows travelers to continue moving during storms rather than closing a pass or roadway. If you haven’t before, look into getting chains or traction alternatives recommended for your vehicle. Practice installing chains at home or driveway. You do not want to install chains for your first time along the side of a highway during a winter storm.
5. Always expect winter travel conditions. Drive knowing and expecting that snow and ice conditions could be present. Roads that appear wet could be black ice.
6. Even if you don’t see them, our crews are out there. Plows must travel slow and often are plowing other roads or sections of highway if you don’t see them while driving. Our crews take great pride in their work. Many live in the areas that they work.

Know before you go

• Download the WSDOT mobile app.: https://wsdot.wa.gov/travel/travel-information-phone
• Sign up for email and/or text updates about road conditions – or sign up to receive text message alerts about significant delays on Snoqualmie Pass by texting "START" to the number 85107.
• Follow WSDOT across a variety of social media platforms including Facebook, Threads, X/Twitter, Instagram and TikTok.
• Check current traction and chain requirements for mountain passes, which are also available on highway-advisory signs and highway-advisory radio.