Flash flooding in Utah leaves car and storage unit floating
An atmospheric river called the “Pineapple Express” could bring heavy rain to parts of the desert Southwest and southern California during Halloween weekend, a little more than a week after destructive flooding hit parts of Arizona, Nevada, New Mexico and Utah.
This latest round of rain will be powered by a low-end pineapple express, a type of atmospheric river that often fuels heavy rain in the West, especially during a stronger El Niño winter.
(FULL COVERAGE: Super El Niño of 2026-27)
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We’ll discuss this trend further after laying out important forecast details this weekend.
When and where will these soaks arrive?
There are two rounds of torrential rain coming:
- Thursday and Friday: West Texas, parts of New Mexico and Arizona
- This weekend: In Southern California primarily, it will increase starting Saturday, peaking early Sunday. In the southwest, rain and some snow in high mountains will increase late Saturday, continue into Sunday, and persist in some areas into Monday.
What are the potential impacts?
Local flash flooding is possible with the first round of rain in parts of West Texas, including Lubbock and Midland.
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A more serious flash flood threat is at play in the desert southwest.
That’s because the ground is still saturated from the 2 to 5 inches of rain that soaked the region last week, triggering significant flash flooding in northern Arizona, New Mexico, southern Colorado and southern Utah.
This is also because some of these areas will experience both spells of rain in just three days.
The map below shows precipitation totals from both systems in the southwest. Areas shaded darker green and yellow may experience more dangerous and widespread flash flooding.
Areas of greatest concern are the north and east sides of metro Phoenix, the Four Corners and the foothills and uplands of San Diego County. Additionally, any ground ravaged by recent wildfires is particularly likely to produce fast-moving debris flows, even with modest rainfall.
If you were planning to go on weekend hikes in parks in southern Utah, southern Colorado, and Arizona, you should consider canceling. Rapid, life-threatening flash floods can sweep through slot canyons quickly.
At higher elevations, this precipitation may fall as snow in the Sierra. This could make travel slippery primarily Sunday through Monday over mountain passes.
A humidity record for the Halloween weekend?
What’s fueling this dip is a southward dive of the jet stream off the West Coast.
This jet stream will carry a ribbon of deep tropical moisture called an atmospheric river toward the southwest.
This atmospheric river tap comes from near Hawaii, which meteorologists call “the pineapple express.”
This is the weather forecast for Halloween weekend, showing an atmospheric river heading toward California and the Southwest.
It’s not a strong version of an atmospheric river or pineapple express, but the humidity fueling these heavy rains could break a record for this time of year.
Total atmospheric humidity in parts of Arizona, Colorado, Nevada and Utah could be 2 to 3 times the late October average, near record levels for Halloween weekend, according to the National Weather Service.
This could be a warning sign, given the trend toward a wetter southwest during the strongest El Niño events, from fall to spring.
Jonathan Erdman is a senior meteorologist at Weather.com and has covered national and international weather since 1996. Extreme and bizarre weather are his favorite topics. Contact him on Blue sky, X (formerly Twitter) And Facebook.
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