WeatherReady Nation Summer Safety Campaign

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WeatherReady Nation Summer Safety Campaign
Summer Safety in the Sierra: Lightning and Flash Floods

Now that Memorial Day is past, schools are letting out for the summer and vacation season has begun. Soon the beautiful Sierra Mountains will become a become an outdoor playground.

In the Sierra, the main summer hazards are Lightning and Flash Floods

Lightning

Across the US, lightning is, on a annual basis, as much a personal threat as tornadoes. The large number of campers, hikers, and boaters in the Sierra, combined with frequent thunderstorms, mean that summer thunderstorm lightning risk occurs on an almost daily basis here. Know the safety rules: check the weather forecast for the day, watch the sky for signs of thunderstorm development, and know how to stay safe. Safe places include indoors, as long as you are staying away from electrical, plumbing, and landline phones. Inside a metal topped car or SUV is safer than being outside. In short, when thunder roars, go indoors! There is no completely safe location outdoors in a thunderstorm! See https://www.youtube.com/watch?v=rMOFxrAWquk for National Weather Service (NWS) safety tips on lightning.

Flash Floods

Another summer hazard in the Sierra are flash floods. Flash floods may develop as little as 10 to 15 minutes after heavy rain begins to fall. The rain may fall on a ridge or mountain top and may quickly move downstream to your location. Dry creek beds or dry washes, and narrow valleys or canyons may be particularly risky. In areas downstream of recent wildfires, rain may mix with mud, ash, and debris from the fire, creating a debris flow. The US Geological Survey (USGS) estimates that as little as a 1/4 inch of rain in 15 minutes in a fresh burn area may be enough to initiate a debris flow.

The safety rule for floods for hikers is climb to higher ground. For motorists, remember Turn around, don’t drown! See https://www.youtube.com/watch?v=eI6mIlHKrVY#action=share for an NWS safety video on driving across a flooded roadway. As little as a foot of moving water can lift and carry a car downstream in a flood.

Jim Purpura
Certified Consulting Meteorologist