The fatal collision occurred when four tractor-trailers and a pick-up truck collided on eastbound I-90 around 5 AM near milepost 62, on the eastern side of the pass. As a result, the eastbound lanes were closed for 13 hours!
The westbound accidents involved three semis and three cars near milepost 61 and closed the pass for 6 hours.
The location of the accidents are shown in the map below (red marker at Milepost 62) Note that the accident site is about 10 miles east of Snoqualmie Pass in a relatively low area of the Yakima river drainage. Keep this in mind...it will be important.
Roadway icing conditions were reported in the area. Let's explore why.
The meteorology of the situation is no mystery. Cool, near freezing and subfreezing air over eastern Washington pushed up the Yakima Valley/ I-90 corridor to near Snoqualmie pass, while warmer air was aloft.
A plot of the surface air temperatures (typically 2-meters above the surface) at the time of the accidents (around 5 AM), shows 31F in the area of the accident. And temperatures at the surface could have been a few degrees cooler than that. And near freezing temperatures were found down the valley towards Cle Elum.
Temperatures were actually warmer above the valley, since cold air was trapped at lower elevations.
What about precipitation? To get some insight into this, let's check out the nearby (but higher) Stampede Pass weather station, located at roughly 4000 ft (I-90 near the accident site was at about 2400 ft). It was dry at Stampede Pass until 10:48 PM (0634 UTC), followed by a wintry mix of rain, snow and ice pellets. Precipitation was over by 2:49 AM. Note that the air temperatures were a few degrees warmer at Stampede Pass than at I-90.
Local weather radar is consistent with the Stampede Pass record and showed a band of precipitation moving through late the previous evening and during the early morning hours (see radar imagery below for 9:01 PM and 11:43 PM the night before).
Importantly, this band of precipitation was forecast skillfully the day before, as indicated by the UW WRF model (the 21h forecast for the 3-h precipitation amount ending 1 AM Friday)
So we had freezing temperatures at the surface and precipitation falling into it, with an icy mixture of cold rain, snow, and ice pellets falling into the cool air near the surface. An obvious threat.
Now, I would not be surprised that the drivers involved in these accidents were driving too fast for the conditions. But there is SO MUCH WSDOT could do that could help prevent such accidents, but to do so WSDOT needs to use weather data in a much more proactive way.
For example, with temperatures below freezing on that roadway section and precipitation moving in, WSDOT could reduce the speed limit on that section (perhaps 35-40 mph). That can easily be done with the electronic signage installed along the freeway. Push people to slow down.
Time and time again there are similar incidents with extensive accidents, loss of life, and extended periods of closing the pass when sudden inclement weather comes in. Weather conditions THAT ARE ENTIRELY FORESEEABLE with modern weather observations and modeling.
Another example is the situation on the western side of the Snoqualmie pass April 2nd of this year in which the pass was not only closed, but a pregnant woman and her unborn child were killed. This heavy snow event was caused by a predictable convergence zone and its evolution was clearly evident on weather radar. The speed limit could have been greatly reduced BEFORE the accident occurred, hopefully preventing it.
And such predictable highway weather disasters are found all over the State, like the freezing rain that caused a Husky Band bus to overturn on the way to the Apple Cup.
Pre-emptive actions to slow traffic and prevent accidents is critical, because once accidents start to occur, plowing becomes nearly impossible and the pass or roadway has to be closed for hours to clear up the mess, before the plows can go to work.
WSDOT Needs to Build the Capacity to Use Weather Data Better
In 1970, there were only a few dozen real-time weather observation locations in our state. Today, there are thousands. In 1970, weather forecast models had no ability to predict local weather. Today, we have extremely skillful high-resolution forecasts, some updated every hour. Today we have excellent weather satellite coverage, where there was nearly nothing available in 1970. Same with radar coverage. In 1970 it was difficult to communicate to folks on the road. Today, with electronic signage and smartphone apps, information can be transmitted in real time.
Weather information and forecasts are now so skillful that WSDOT needs to change the way it does business: not reacting to weather situations but acting proactively. With a modest investment, WSDOT could build the capacity to access state-of-the-art weather information and forecasts to build warning systems that would save lives and radically reduce the number of pass closures. Speed limits could be reduced as a matter of course when inclement weather is imminent. And keep in mind that such a proactive system would not only save lives, but have major economic benefits, since pass/freeway closures are extraordinarily costly for our state, with losses of many millions of dollars per day when Snoqualmie pass is shuttered.
Unfortunately, WSDOT management is not only NOT investing in such systems, it has been going in the wrong direction. When offered such capabilities, they expressed little interest in using weather data in this new way, and recently dropped funding for the state-of-science weather communication tools they were supporting, like the I-90 and Ferry Weather pages shown below.
Building a modern weather warning system for Washington State roadways would pay for itself in one event.
Perhaps if Washington citizens let their elected officials and WSDOT management know that the current situation is not acceptable, better use of weather information on our roadway will occur.
from Cliff Mass Weather and Climate Blog http://bit.ly/2QHm2WQ
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