When rain or snow is heading our way, the first clue we get often comes from weather radar, the big one down in Pocatello operated by the National Weather Service. That amazing machine can not only detect storms but tell many things about them, like which way they’re moving, how tall they are, and whether they contain hail and how big it might be. But without all the bells and whistles, basically, what is radar and how does it work? When doesn’t it work?


Spotter's Guide

Weather Spotter Guides from the National Weather Service.


The word radar was created as an acronym for Radio Detection And Ranging, and it’s development goes back to the late 1800s and early 1900s with the first contributions from Germany, Russia, and the UK.


Think of radar as a kind of flashlight. When you flip on a flashlight at night in your favorite campsite, if the beam doesn’t hit anything, the light just keeps going and you see nothing because there’s nothing to see. But if the beam hits something, maybe the eyes of a critter waiting for you to go to bed without hanging your sandwich from a tree, the light bounces back to you and you see that old familiar eye shine. At its simplest, that’s how radar works. A transmitter sends out a beam of radio energy, very much like light from your flashlight only you can’t see what it hits with your eyes. If it hits nothing, it just keeps going, but if something is in the way, maybe a storm cloud or an aircraft or my car when I’m going just a little over the speed limit, the invisible radio beam bounces off that something and comes back at ya. Since you can’t see a radio beam, a radar unit includes a detector which can “see” the reflected beam and turn it into a picture on a screen for you. With a regular flashlight, your eyes are the detector.


As with a flashlight, though, a radar beam can’t help you see through mountains. Teton Valley is surrounded with mountains, and between us and the weather radar in Pocatello are the Big Hole Mountains and the rest of the Snake River Range. This makes trying to see what’s going on in Teton Valley with radar about as futile as standing in Swan Valley with a very large flashlight and trying to use it to see what’s happening in downtown Driggs. The best you can do is point the beam up and look at the clouds floating high over Driggs and make your best guess about what’s happening below them. This works when the storms are big and the clouds reach high into the sky like our summer thunderstorms. But so often, especially our winter snow clouds are too low to see that way, down in the radar shadow of the Big Holes. If precipitation falls from those low clouds, or if it falls from higher ones but evaporates on the way down, radar won’t give an accurate picture at all of what’s really happening on the valley floor.


So what’s the answer to this problem? One of the best is weather spotters, people in the valley reporting to the National Weather Service when things get interesting. (When aren’t they here?) Because of the limitations of radar, they are eager to hear about things like hail damage, heavy rain over ¼ inch an hour, heavy snow over one inch an hour, or wind over 40 MPH. Without people reporting these things, the NWS may be unaware that they are happening and the appropriate warnings may go unissued. The few trained weather spotters in the valley know to report these conditions when they can, but anyone can report hazardous or threatening weather. Teton Valley Weather is a partner and passes such reports along to NWS ASAP, but you can report them directly too, either online at the National Weather Service Pocatello web site or Facebook page, the Riverton office if you are in Wyoming, or by calling 208 233-0834. They will want to know just where you are and just what you are seeing as precisely as you can.


Better yet, attend a weather spotter training, offered at various places by both the Pocatello and Riverton offices of the National Weather Service.




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