Even In Drought, Thunderstorm Season Is Here

Chris Smallcomb is a DPMR member and a Meteorologist at the National Weather Service – Reno.

Hey everyone! Well, welcome to summer. We’ve already had a couple rounds in the furnace and even though we’re in a serious drought, summer thunderstorms can still be an issue for us out in the mountains. To that point, back during the peak of the last severe drought in 2013-15, our forecasters were kept busy with fairly big thunderstorm seasons and the resultant flash flooding, severe winds, and new fire starts.

Even as a National Weather Service meteorologist of 21 years, whose job is literally to help everyone including public safety first responders make good weather-based decisions, I find myself making the occasional questionable weather decision out on the trail. We’ve all been there… “I’m so close. I want to finish.” or the always popular excuse, “I’ve planned this adventure run out for weeks. I have to keep going” – so I get that emotion!

So let’s talk about running and thunderstorms, with hopes of keeping you from running into a thunderstorm, but you know sometimes it’s just not your day and that storm cell comes up from behind to take the lead. Let’s talk “What would I do?” scenarios. Remember when it comes to running on days where t-storms are possible, it’s about making choices that REDUCE THE RISK, not entirely ELIMINATE THE RISK from thunderstorms. Lightning is typically the star of the thunderstorm show but there’s also hail, cold rain, hypothermia, strong winds, and new fire starts.

1) Does it matter how I spell lightening?

First up, please if you take one thing away from my missive today:

Just kidding, do read on…

2) In light of the recent trail race tragedy in China, what is your trail run/race worst case scenario in our area when it comes to thunderstorms?

One of the most common factors when it comes to weather-related incidents is low predictability hazards catching people off-guard. Weather prediction in the US has gotten really good in the last 10-20 years so these scenarios are less frequent but still happen with t-storms, tornadoes, and even winter weather events.

So with that in mind, we’re looking at a scenario where t-storms are not in the forecast but a couple of isolated storm cells form rapidly and unexpectedly in the vicinity of a mountain race. Again as amazing as our forecast models are, there are still days where this exact scenario happens with one or two storms forming over the mountains on an otherwise dry forecast day.

One of the cells forms directly over an exposed aid station along a ridgeline, such that it’s tough to discern if this is a storm cloud or just regular Sierra afternoon buildups. The storm quickly produces lightning which strikes in the vicinity of the aid station where runners are congregated, near and under a canopy. Since runners and volunteers are crowded together, they are all hit by the discharge and incapacitated (or worse).

In this scenario nobody can render aid and communicate with 911 or race management the need for help, delaying those critical moments until another runner or volunteer comes by. A secondary but still important impact is cold rain/hail falling leading to hypothermia on top of everything else. If the storm is slow to move off or dissipate, that will also delay the use of air evacuation for the injured which ups the odds of a more catastrophic outcome.

3) What can I look for to prepare ahead of time to avoid getting into a pickle when it comes to thunderstorms?

When you’re looking at a forecast to help plan your run, I’ve got a couple rules of thumb when it comes to thunderstorms. Let’s say you’re looking at the forecast for today or tomorrow:

• A 20% chance generally means isolated storms, but you should still keep an eye on the sky. Honestly anytime it gets hot enough for Reno to hit 100+, we’re probably going to have something bubble up over the mountains that afternoon. Heat is food for storms.
• A 40% chance or higher is actually pretty good odds of storms in our region. Rethink it as a 2 in 5 chance – sounds more possible now doesn’t it? That might be a day to break out that headlamp and get started super early or consider another day when the probabilities are lower.

Now, if you’re looking at a forecast more in advance, say 5-7 days out, often the ingredients for t-storms forming are much much less predictable at those lead times. Therefore the forecast may not show t-storms due to super low confidence. Yet another reason to check the weather daily!

• Good National Weather Service forecast resources to check daily for summer mountain runs:
• Backcountry Forecast – summary of conditions for Truckee-Tahoe and Mono County for the next 36 hours.
• 7-Day Point Forecast for anywhere – always check the elevation to make sure it’s representative of where you’re going (example this one is for Mt Rose but the 2.5km grid box is only at 9,700 feet so factor that into what temps & winds will be like on the summit – cooler and breezier!)
• Forecast Discussion – treat your inner weather geek to some extra nuggets on expected scenarios, confidence levels, and things that may not otherwise show up in a standard forecast.
• Current Weather Observations and Radar – you can tweak what’s shown and the locations and re-bookmark it. Reasonably mobile friendly.
• Social Media – @NWSReno (Tahoe and Sierra east side) and @NWSSacramento (west side of the Sierra)

The morning of your adventure, definitely check the forecast and also check the radar. There are days like Silver State 50/50 this year where storms were already fired up at 7 AM!

Another thing to look for is early morning altocumulus castellanus (or ACCAS in weather nerd speak). These building bubbly clouds indicate plentiful energy and moisture for storms, and likely starting earlier in the day than normal. If you see these it’s going to be a busy day storm-wise and might be good 1) to get out early, or 2) shorten your journey, or 3) stay at a lower elevation, or 4) try another day. Note that ACCAS are not a necessary deal for storms, as we have plenty of storm days where it starts out perfectly sunny. It’s just that ACCAS indicates a much higher risk of storms later in the day.

4) What would I do if caught in a thunderstorm unexpectedly? Yes, that even happens to meteorologists.

So here is where we borrow a phrase from the movie Argo about the Iranian hostage rescue, “This is the best bad idea we have, sir, by far.”

I’ve been in situations, thankfully just a few, where thunderstorms got close enough for me to be nervous. Most recently we all know the weather for Silver State 50/50 was quite volatile that afternoon with thunderstorms, lightning, and cold wind driven rain and hail especially up at the Peavine and Dog Valley aid stations. I was on my way down the mountain toward the finish of the 50k and admittedly the storms nearby and loud cracks of thunder did get me to pick up my pace…

So what would I do in a situation where storms were right in my face with lightning and all the other hazards. Run, and run down off the mountain or ridge line as quickly as I could. Keep moving with the goal 1) get to a safe shelter such as a sturdy building or vehicle, or 2) at least get to a place off the ridge line away from large trees where I can hunker down. Caves or hiding under rock overhangs may keep you dry but you still are at risk of a lightning strike there. Remember, it’s about doing things to REDUCE your risk when you’re in a situation such as this.

Another nugget to remember in this scenario: space out if you’re in a group. It’s morbid but that way only one runner gets struck by lightning instead of ALL of us with nobody to help. I know we like to run these hard routes with our friends closeby, but not in a t-storm situation. CPR First Aid training would be a good thing here too!

Oh, and I often get asked about the “crouch position”. You’re still in contact with the ground, but if it’s a last resort situation and if it makes me feel better – then by all means I’d do it.

Regarding “the other hazards” such as hypothermia from cold rain/hail, hopefully you looked at the forecast and brought along a jacket or an emergency blanket. I don’t have any other pearls of wisdom on that note. Temperatures can easily drop 40+ degrees in 10 minutes in our dry climate as rain evaporatively cools the air around it. Remember that t-storms can also produce strong outflow winds several miles from the storm, and that’s where you need to be mindful of the trees around you. This is especially true in burned areas with large, dead trees – those topple much more readily than healthy live trees. This along with increased flooding hazards are big reasons forest trails are closed for extended periods after a large fire.

5) So, when is it safe to get back out on the trail or outside after a thunderstorm?

Well, the conventional wisdom on that one is waiting 30 minutes from the last thunder roar or flash of lightning. That may seem onerous and stupidly long, but it really helps to account for new storm formation nearby and the caveat that decaying t-storms can produce a decent amount of lightning. Lightning can strike up to 10 miles away from the parent cell. That “bolt from the blue” is actually lightning from the anvil of a t-storm – a real deal.

Canopies, tents, and sheds offer ZERO protection from lightning. I can’t stress this enough – while they can keep us dry and warmer, the shelters we are fond of using during races or on the beach offer ZERO lightning protection.

6) Hey Chris, what weather app do you use? If I can’t use my app, what should I look for to anticipate thunderstorms out on the trail?

Well… Many of our trails have cell data access of some flavor so using a radar or weather alerting app is a powerful tool to stay safe. The NWS does not have it’s own app. Don’t get me started. However you can bookmark our forecast pages to create a “fake app” button on your homescreen. Most NWS pages are sort-of “mobile friendly”.

In terms of “real apps” what I personally use is Radarscope. It’s a paid app that gives your access to real-time high definition NWS radar data along with your position. There’s also an option to get lightning data as an extra add-on. One thing you may not know is that ground-based lightning data in the US is all privately owned, so often you have to pay for access.

Those Wireless Emergency Alerts you get on your phone that you didn’t sign up for are only for certain hazards, NOT ALL THUNDERSTORMS. Those only trigger for Flash Flood, Tornado, and high-end Severe Thunderstorm warnings. Many apps out there offer alerting services, often paid, for t-storms and lightning. NOAA Weather Radio can be an option but it’s another device to carry along and there’s no specific geolocation feature.

If you’re out of cell data range, then it’s up to your eyes and ears. If you start seeing clouds that are bubbly, growing taller, and getting darker – that’s an indication of storms possibly developing. Yep, it’s that simple. If a cloud looks dark and menacing, then it probably is. That’s the point where you should look at your options and make a risk assessment for continuing or deciding to turn back or head to a lower and less exposed elevation.

So that’s what I’ve got. Hopefully you took away some tidbits to help keep you more informed and safe when it comes to summer thunderstorms. Please, feel free to email me at chris.smallcomb@noaa.gov with any followup questions. I’m always up for a conversation about running and weather!