Light rain showers fell on parts of the Columbia Basin Monday evening. These brought an insignificant amount of rain, with the Tri-Cities Airport only recording a trace (meaning it wasn’t enough to measure). What made it stand out, however, was the amount of dust it left behind. Dust mixing in with rain happens from time to time, but it always brings the question – where did it come from? For Monday evening’s event, the answer looks to be Summer Lake to the southeast of Bend, Oregon.
Satellite imagery captured a dust plume coming from the Summer Lake area around noon Monday and heading toward the north. The wind was being lifted off the dry portion of the lake bed by strong winds. A weather station on the lake’s western shore recorded a peak gust of 49 mph during the day, with some stations in southeastern Oregon peaking around 65 mph.
Southeastern Oregon is pretty arid, limiting plant growth. The PRISM Climate Group at Oregon State estimates that the area averages just over ten inches of rain a year. Adding to this, Summer Lake is the remnant of a much larger lake named Lake Chewaucan that existed in the region around 13,000 years ago. As the lake shrunk, the water became increasingly salty, and depositing salty and alkali sediment as it shrunk. This soil further limits plant growth on the dry lake bed surrounding the waters of Summer Lake.
Without plant life, there is plenty of dust to be picked up and carried away on windy days. As noted and shown in the satellite image above, Monday’s strong winds in southeast Oregon carried the dust toward the north. Around 7 pm, I observed rain falling while enjoying time with my wife and daughter in Richland’s Howard Amon Park.
Using NOAA’s HYSPLIT model, I was able to look backwards in time from 7 pm to see possible source regions for the dust. Reviewing the model output on the right (above on mobile), it appears that the source region for the dust likely was from the Summer Lake area.
Further evidence for this can be seen in the dust itself, which is a sort of off white color. This is common for the sediment lying on dry lake beds of the Great Basin and can be seen at Summer Lake itself but also on the several dry lake beds along Interstate 80 in northern Nevada. Interestingly, this isn’t the first time the Tri-Cities has experienced a milky rain from Summer Lake’s dust. Jason Tomlinson, meteorologist at PNNL, pointed out to me that a similar event occurred in the Columbia Basin in February 2015 when a milky rain dropped Summer Lake dust on the Tri-Cities, Spokane, and parts of Idaho.
3 Comments
Hi my name is Harrison Roosevelt. February 2nd many days afterwards I’m not sure but that dust / rain entered into my storage unit and Rexburg, Idaho. The dust settled in my Alpine storage unit and covered the floor of the walls the ceilings of that unit my clothing, bedding, household appliances, equipment, you name it. The storage facility has nearby farms possibly potatoes, corn etc. My question is what’s in the dust? Are there any chemicals in the dust in other words that could harm me from the use of my clothing my carpets bedding etc?
Hello Harrison, and sorry for the late reply. I would not expect there to be anything so harmful in your dust that you would not be able to use the things it got into. We have similar cases here in Eastern Washington but I have never heard of anyone having a medical issue from chemicals in dust blowing from agricultural fields. You should probably wash it before use if the dust was blown in within a day of herbicide or pesticide being used, but I suspect you probably would have washed it anyway. Thank you for reading!
Awesome post Mark! I remember the “milky rain” back in 2015 – very cool that you could trace the origins of the dust in this rain.