Cold Pockets

I’m guessing most of you know what I mean by the term “cold pocket”. There’s just some locations that nearly always seem to be colder than the surrounding areas. While this tends to happen more in areas of varied terrain, it can happen just about anywhere.

So why do cold pockets exist?  Mainly it has to do with those locations where the wind goes calm at night.  This allows the atmosphere to cool without the wind mixing in warmer air from above.  And it’s usually not obvious why a location likes to go calm at night. Additionally, the direction of the wind plays a role. Some locations go calm except if this wind is from a certain direction.

The Inland Northwest has a lot of these cold pockets. And our recent June cold snap showed a number of them.

When I started with the Weather Service in Spokane 30 years ago, we had very few weather observations.  Mainly just the airports. But that included the Deer Park airport.  And so we knew that Deer Park was a cold pocket. But what we didn’t know is how representative was that measurement for the surrounding areas?

Since then, a multitude of various agencies have fielded their own network of weather observations. A couple of websites gather all of these observations together to give a more complete picture. Take the low temperature on the morning of 8 June:

The Deer Park airport sensor measured a low temperature of 28 degrees.  But how representative was that?  Turns out, it’s probably a very localized cold pocket.  You can see another observation just south of the airport only dropped to 34F. That’s quite a temperature gradient over such a short distance.  Other nearby measurements confirm that the 28F at the airport wasn’t what most areas experienced.

Another cold pocket is south of Oldtown, Idaho. 

A Union Pacific Railroad sensor measured 26F that same morning. While a few nearby sites were also cold, none matched the 26F reading.

Springdale, WA also has a cold pocket. A sensor has been there for quite awhile, so we knew about this cold pocket. But recent additional sensors have help confirm the size of the cold pocket.

The 29F just south of Springdale was the coldest measured temperature in the area.  But a new sensor at Ford shows that the cold pocket is possibly bigger than we thought.  

One last cold pocket I’ll mention is south of Pullman, along Highway 195.

Uniontown and Colton are a good 10-15 degrees colder than surrounding towns on this morning. If you’ve driven 195 through those towns, it’s hard to explain why they would be cold pockets.

You probably know of several other cold pockets and may live in one. If so, enjoy the cooler weather.