In this week’s post I will talk a little bit about how to prepare yourself each day to avoid being surprised by thunderstorms. And if for some reason you do get caught out during a thunderstorm, some tips on what to do.
Your first order of business each day, should be to check the weather forecast. That will to give you some idea about what to expect. In particular, check the probability of precipitation, and also if any thunderstorms are mentioned in that forecast.
On the Jackson Hole Forecast page of mountainweather.com you will see daily weather icons, as well as in the textual description for each day, showing the percent chance of precipitation. Below that text, “Precipitation Probability” is also listed for the mountains, which often times will be a little higher than for the valley.
A “Lightning Activity” forecast is given each day, listed as: None, Low, Moderate, or High. The activity rating will depend on the likelihood of thunderstorms and how strong those thunderstorms are expected to be. Further down the page this info for the mountains is displayed in a graph format.
A high probability of precipitation, greater than 60-percent, in combination with moderate or high lightning activity, should perk-up your interest and be cause for concern that day.
That said, even a low chance of thunderstorms or lightning activity warrants some vigilance of your surroundings. That is, keep an eye on the sky for building cumulus clouds.
The next thing you should do, whenever there is any mention of thunderstorms in the forecast, is to assess the activity you plan on engaging in. Will you be hiking or biking up to a ridgetop, going over a pass or saddle? Will you be travelling across large areas of open terrain? Will you be on a lake or river? All of the above put you in areas of high exposure to lightning.
Fishing and boating are high exposure activities in a medium that is a really good conductor of electricity, water. Of all the outdoor activities, fishing accounts for the highest percentage of lightning fatalities in the United States.
Are you going to be on a baseball or soccer field? These are wide expanses of open terrain that leave you highly vulnerable to lightning strikes.
Also, assess how much time and what time of day you expect to be in any of these vulnerable positions?
A thunderstorm does NOT have to be directly over you to throw a bolt of lightning your way. It does NOT have to be raining first, before you should seek shelter. Although, most people never think about seeking shelter until either one or the other of these is happening.
Another Trivia bit: The most dangerous time for a fatal lightning strike, is before the thunderstorm is directly overhead.
When you do seek shelter, buildings or vehicles are the safest places to be. A picnic shelter, baseball dugout, or under a rock overhang are NOT safe places. Why? Because:
1) The picnic shelter is an un-grounded structure that will not fully disperse the electrical charge.
2) Same with the dugout, which may also have a chain-link fence that can conduct the electricity, so at least don’t hang onto the fence!
3) Under the rock overhang, your body is filling in the space between the roof of the overhang and the ground, making it easier for electrical currents running through the rock to close that gap, directly through you!
Postpone or Go Home
No matter what the weather forecast, or how you interpreted it, as your mom used to say, “better to be safe than sorry”. In this case, better to turn around, cancel your plans, of just go home early than to be fried by lightning.
In the mountains at least, I have learned to not let my goals interfere with my decision making. I keep re-assessing the weather, but when clouds are building and as soon as I can hear thunder, I don’t want to be in a vulnerable location to wait it out, I am looking to retreat.
Lightning can be marvelous to watch, but it can also be quite frightening, kind of like being too close to the fireworks. I will write more about thunderstorms and lightning safety in future columns this summer. Have a happy and safe Fourth of July.
Posted by meteorologist Jim Woodmencey
Some of the content of this post first appeared in the Mountain Weather column in the Jackson Hole News & Guide on July 4th, 2018