dpSouthwest facing flash flood threat from Hurricane Polo’s moisture
A combination of historic moisture from Hurricane Polo and a plunging jet stream will bring a widespread flood threat to the Desert Southwest that will spread into the Plains and Midwest over the next few days.
What makes this situation impressive
The amount of moisture in the atmosphere is expected to be near or above record levels for late September over parts of the Southwest, Texas and Oklahoma.
And tropical rain is unusual for some.
The amount of moisture being lofted over southern Arizona, New Mexico and far west Texas is near or slightly surpassing that in the historical records. And it won’t stop as the remnants of Polo fizzle out.
“Looking back through history, heavy rains from the remnants of tropical systems are very rare across western Kansas,” wrote Jonathan Finch, meteorologist at the National Weather Service office in Dodge City, Kansas, in a forecast discussion Tuesday morning.
Happening Now
A historic plume of moisture is moving northward through northern Mexico, Arizona and New Mexico, with rainfall rates up to two inches per hour. Dry washes, slot canyons, burn scars and flooded areas should be avoided.
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You can see where the rain is falling now, in the radar image below. Any watches or warnings issued are also shown on that map.
This morning, a box truck was swept away by floodwaters north of Phoenix. The driver was able to make it out safely. At least one other water rescue was performed in the metro area for somebody who thought they could drive through the water, but failed.
Several washes and even Interstate 10 saw flooding earlier today between Tucson and Phoenix.
Flooding has also overwhelmed some roads in New Mexico where creeks and arroyos are running high already.
(MORE: Why flash floods hit harder in mountainous terrain)
How much rain could fall
Polo is now moving through northwestern mainland Mexico, producing as much as a foot of rainfall and triggering flash flooding and mudslides in those areas of Mexico.
Here are the rainfall forecasts for parts of the U.S.
- Southwest: Up to an additional 2 to 4 inches of rain, with rainfall rates of 1 to 3 inches per hour possible. Some could see over a month’s worth of rain from this event alone.
- Southern Plains: 3 to 5 inches of rain, with locally higher amounts, is possible from parts of Texas into Oklahoma, including Dallas, Austin and San Antonio. This would be the heaviest rain event in eastern Oklahoma since June and in the Dallas-Ft. Worth Metroplex since early July.
- Central Plains/Midwest: A stripe of 3 inches of rain or more is expected from parts of Kansas to southern Nebraska, northern Missouri, southern Iowa and northern Illinois.
(MORE: Flooding is one of deadliest weather events)
Flood threat timeline
The deep tropical moisture that Polo carries won’t be quick-moving, and will bring the threat for showers and thunderstorms in the Southwest, Southern Plains and into the South.
Here’s when you can expect an uptick in rainfall over the coming days.
Through early Wednesday morning: Southeast Arizona (including Tucson) and much of New Mexico are at particular risk for flooding into this evening as the core of Polo collides with another system dropping through the Four Corners region.
The elevated flood threat expands north and east to include parts of the Plains. Nearly a dozen states are at risk for flash flooding, with Arizona, New Mexico, Colorado, Kansas and the Oklahoma and Texas panhandles are under the greatest risk.
Tropical moisture, however, will reach as far north as Minnesota, where the flash flood risk extends.
(MORE: Why danger from hurricanes doesn’t end at the coast)
Wednesday’s threat: The threat of flooding shifts a bit eastward, with more of the threat expanding into Texas, Oklahoma and Colorado. Parts of the Dallas Metroplex is under the greatest threat of flooding on Wednesday.
But tropical moisture will extend all the way into Wisconsin and Michigan, where there is a risk of flash flooding.
You can see the areas most at risk for flash flooding in the map below.
Thursday’s threat: The threat of flooding extends eastward to The Southern Plains and the Great Lakes, from Texas to Michigan. The heaviest threat of rainfall is again in place for a swath of Texas that includes Dallas and the Hill Country.
How to stay safe during flash floods
When heavy rain threatens, never try to drive through a flooded road.
It may be tough to tell how deep the water is when you approach a flooded section of road, especially at night, so never try to proceed — instead, “Turn around. Don’t drown,” as the National Weather Service says.
Driving into a flooded area can allow water to stall or submerge your vehicle in a matter of minutes or even seconds.
Take warnings seriously. Your local National Weather Service office issues a flash flood warning when flash flooding is either already happening or expected to develop based on rainfall rates and radar trends.
You should make sure you are aware of possible flooding in your area when one is issued and avoid travel if possible, especially at night.
If a flash flood emergency is issued, that’s your signal that the situation is dire, and you should avoid travel and head to higher ground if in a flood-prone location.
(MORE: What to do before, during and after a flood)
Flooding Recap
On Monday, flooding swamped Casino Drive and the Laughlin River Walk beneath the Edgewater Casino in Laughlin, Nevada. One vehicle was also stuck in mud in the city about 75 miles south-southeast of Las Vegas.
Vehicles were flooded and stuck in Bullhead City, Arizona, Needles and Indio Hills, California.
A yard and basement was flooded in Hurricane, Utah, while a large cargo container was swept down the East Fork of the Virgin River and struck the U.S. 89 bridge in Mt. Carmel, Utah.
