Tag Archives: lewiston grade

TWSB: And This is Why I Couldn’t Fly Out To Seattle Today

Lewiston’s under there, somewhere.

These pictures, taken yesterday around 3 PM, show the result of an inversion, or “a deviation from the normal atmospheric property with altitude” (thanks, Wiki). In the case of Lewiston here, the inversion involved temperature: Lewiston was uncharacteristically colder than the surrounding higher elevations (it was 21 degrees in Lewiston, according to my dad’s car, whereas it was about 32/33 in Moscow).

For those readers (like none of you, but whatever) who aren’t familiar with the surrounding geography of Northern Idaho, it’s like this: Moscow and the majority of the surrounding towns sit at about 2,500 feet above sea level. Lewiston, on the other hand, is situated at the confluence of the Snake and Clearwater rivers and is thus at about 745 feet above sea level. To get to Lewiston from Moscow you have to drive down the Lewiston Grade, a 10-mile winding spiral of highway that wraps in and out of the surrounding hills and drops you a total of 2,000 vertical feet.

It sounds a lot more fun than it actually is.

Anyway, on any given day Lewiston is usually about 9,000 degrees hotter than Moscow, so to experience below freezing temperatures (and snow! Break out the panicked drivers) down there is weird.

There are several causes of inversions so I don’t know if I picked the right one to explain here, but it seems most likely given the conditions and surrounding geography. An inversion can occur when warmer, less dense air moves over a cooler and denser mass of air. This usually occurs around warm fronts (or areas of oceanic upwelling, but that’s not happening in Lewiston, haha). If the lower dense area is sufficiently humid, then a layer of thick fog can often be found at the inversion cap.

Other consequences of thermal inversions I learned about when researching this on Wiki include:

  • Still, murky air
  • Mirages
  • a green flash (no, not the love child of the Green Lantern and The Flash, sorry)
  • the total reflection of sound waves off the cap of the inversion, which causes major problems in the case of explosions.

Cool, huh?

But now I can’t fly out until Monday morning, at best.

Oh, also this:

Master’s degree, bitches!