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The Mojave Desert is facing a triple whammy of hazards this week as the National Weather Service warns of flash flooding, extreme heat and elevated wildfire risk.
The overlapping hazards are the result of monsoonal storms combining with tropical moisture linked to Hurricane Lorena, which is helping sustain unstable conditions across the region. Forecasters say the interaction of these systems will keep the risk of heavy rain elevated through the week.
What’s in the forecast?
A low-pressure system off the Central California coast is bringing enough moisture and atmospheric lift to generate fast-moving thunderstorms across the region. These storms could produce heavy bursts of rain on the desert’s hardened ground, where water runs off quickly instead of soaking in, creating a potential for flash flooding this week.
Even brief downpours may trigger flash floods in canyons and dry washes. The risk is expected to persist through the week, though chances for showers and thunderstorms will gradually decrease each day, according to the area forecast discussion from the San Joaquin Valley.
Moisture is expected to gradually retreat southeast through the end of the week and into the weekend. That shift has slowed due to Hurricane Lorena’s track toward Baja California, and with daytime heating and lingering upper-level energy, scattered showers and thunderstorms remain possible in eastern areas into the weekend.
Meanwhile, temperatures are expected to remain above 100 degrees during the day, with nighttime lows holding in the upper 70s. This extends an already dangerous heat wave and, combined with lightning from passing storms, could spark new wildfires.
Regional highlights
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Increased chances for thunderstorms exist today and tomorrow, Sept. 3-4, along the Sierra Nevada and into the Kern County mountains, with a 15% to 30% probability of development this afternoon and a 15% to 25% chance on Wednesday, Sept. 3. These storms are likely to produce little rainfall but may result in dry lightning strikes.
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There is at least a 5% chance of excessive rainfall in the Sierra Nevada, Kern County mountains and Mojave Desert today and tomorrow, Sept. 3-4, prompting a flood watch in those regions.
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Moderate Heat Risk continues for the Valley and Mojave Desert through Wednesday, Sept. 3, with a 40% to 80% chance of triple-digit temperatures. Some areas in higher elevations approach a Major Heat Risk.
What is dry lightning?
Dry lightning occurs during “dry thunderstorms,” which produce little to no rainfall. According to the National Weather Service, the drier the storm and the drier the vegetation, the more likely lightning strikes are to spark wildfires. That’s because cloud-to-ground lightning can easily ignite parched fuel without rain to help dampen it.
Is lightning without thunder still dangerous?
Lightning is always dangerous, even if unaccompanied by thunder or rain.
Thunder is simply the sound produced by the rapid expansion of air heated by lightning, according to the National Weather Service. If a lightning strike is far enough away, the sound may not reach you, but the electrical discharge can still travel for miles and ignite fires or injure people.
How often does lightning cause wildfires?
Lightning-caused wildfires are much larger and consume more land (53% of the average acreage burned from 2018 to 2022) than human-caused fires.
However, the majority of wildfires are caused by humans (89% of the average number of wildfires from 2018 to 2022).
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Brandi D. Addison covers weather across the United States as the Weather Connect Reporter for the USA TODAY Network. She can be reached at baddison@gannett.com.
This article originally appeared on Palm Springs Desert Sun: Mojave Desert faces triple weather threat. See forecast
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