A flash flood alert was issued by the National Weather Service in Flagstaff on Saturday, September 27. This alert covers Coconino County.
The National Weather Service advises: “Camping and hiking individuals should quickly move to elevated areas right away! Avoid creeks and washes! Foot bridges in Supai Campground could be destroyed. Certain campgrounds might experience flooding. Visitors could become trapped in parts of the campground.”
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What are meteorologists from the weather service stating?
At 5:30 PM, the National Weather Service released a statement:
The National Weather Service in Flagstaff has issued a Flash Flood Warning for the Antelope Creek basin located in Coconino County, northern Arizona, until 7:30 p.m. MST /8:30 p.m. MDT. At 5:27 p.m. MST /6:27 p.m. MDT, Doppler radar detected thunderstorms bringing heavy rain to the Antelope Creek basin. Rainfall between 0.25 and 0.5 inches has already been recorded. Additional rainfall of 0.25 to 0.5 inches is expected in the affected area. Flash flooding is currently happening or is anticipated to start soon.
Hazard: Potentially deadly flash flooding. Thunderstorms causing flash flooding in and near the Antelope Creek area.
SOURCE: Radar indicated.
IMPACT: Severe flash flooding posing a serious threat to areas near and within the Antelope Creek region. Certain locations that will face flash flooding are: Page, Antelope Canyon, LeChee, Trapeze Cove, Glen Canyon National Recreation Area, and Lake Powell. This encompasses the following slot canyons: Upper Antelope Canyon, Lower Antelope Canyon, Owl Canyon, Rattlesnake Canyon, Ramshead Canyon, and Porcupine Canyon. This also includes the following streams, washes, and rivers: Antelope Creek.
Previously, at 3:06 p.m., the National Weather Service released a statement:
The National Weather Service in Flagstaff has issued a Flash Flood Warning for: the Havasu Creek watershed in Coconino County, located in north central Arizona. This covers the Colorado River between river miles 156 and 158. The warning is in effect until 6 p.m. MST. At 3:06 p.m. MST, local authorities reported flash flooding near Supai due to heavy rain in the Havasu Creek area. Up to 0.5 inches of precipitation has already been recorded. Additional rainfall of up to 0.25 inches could occur in the affected region. Flash flooding is currently taking place.
Hazard: Life-threatening sudden flooding. Thunderstorms causing sudden flooding in and near the Havasu Creek area.
SOURCE: Law enforcement reported.
IMPACT: Severe flash flooding that poses a serious threat to life in regions surrounding and within the Havasu Creek basin. Certain areas expected to face flash flooding are: Grand Canyon National Park, Little Navajo Falls, Mooney Falls, Beaver Falls, Hualapai Hilltop, Supai, and the Havasupai Reservation. This covers the Colorado River from river miles 156 to 158. It also includes all swimming areas on Havasu Creek near Supai. The affected waterways include: Heather Wash, Colorado River, Pasture Wash, Havasu Creek, Black Tank Wash, and Little Coyote Canyon.
What is a sudden flood?
The arid terrain of Arizona is very susceptible to sudden flooding. A flash flood occurs due to intense or excessive rain over a brief period, typically less than six hours, as stated by the weather service.
A sudden and intense flood can occur within minutes. Even when the sky is clear, rain falling upstream may flow into dry river channels, leading to hazardous conditions far downstream.
What volume of water is required to trigger a sudden flood?
A small amount of water can lead to a flood in the desert: an inch of rain or less within an hour is typically sufficient to create flooding. The speed and location of rainfall have a greater impact on flooding than the total amount of rain.
Desert soils have difficulty absorbing water, particularly following long periods without rain. The surface may turn nearly impermeable, leading to water flowing over the top.
Topography also contributes, as steep canyons, mountains, and dry washes are prone to flooding. Regions affected by wildfires face greater danger, since the fire can scorch the surface layer of soil, reducing its ability to absorb water and leading to higher runoff.
What distinguishes a flash flood watch from a flash flood warning?
A warning for potential flash flooding indicates that circumstances are suitable for such an event to occur, although it has not yet taken place. In Arizona, this frequently occurs when monsoon storms or significant rain upstream may cause rapid flows of water through washes, canyons, or city areas.
During a flood warning, it’s crucial to keep track of local weather updates and alerts, prepare escape paths in case of rising waters, relocate cars from vulnerable spots, and steer clear of activities in regions that may flood rapidly.
A flash flood warning indicates a more immediate threat, suggesting that flooding is about to happen or is already taking place. These warnings are usually issued when rain falls at levels that can quickly saturate desert drainage systems or when flooding has already been detected.
Safety tips during a flood alert in Arizona
- If instructed to leave, do so right away.
- Avoid traversing flooded areas. Even 6 inches of fast-moving water can knock you off your feet.
- Make a U-turn, don’t get stuck: Avoid trying to drive through areas with standing water; instead, reverse course and take a different path. Even 12 inches of water can sweep away smaller cars, while two feet of water can move SUVs and larger vehicles. The majority of fatalities from flooding occur when individuals attempt to drive through water.
- Be cautious of fire risks and head to a higher elevation.
- Be mindful of weather alerts and highway closures.
- Avoid letting children play in moving water. Such water may conceal rocks, trees, and other objects.
This weather update was created automatically by utilizing data from the National Weather Service along with a piece authored and approved by an editor.
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This piece first was published on Arizona Republic:Flash flood alerts have been issued for northern Arizona, including the Grand Canyon.
