Pacific tropical rainstorms to cause major flash flooding in southwest US
Combined moisture from Priscilla and Tropical Storm Raymond will bring torrential downpours to parts of Mexico and the U.S. Southwest, with a risk of 4-8 inches of rain and life-threatening flash flooding.
An influx of moisture from Tropical Storms Priscilla and Raymond is leading to widespread heavy downpours across the Southwest, causing flooding in the Desert Southwest.
Leftover tropical moisture from Priscilla combined with Tropical Storm Raymond will send rounds of heavy rain over parts of northern Mexico and the southwestern United States into early next week. AccuWeather meteorologists warn that dangerous flash flooding is likely to unfold in the region.
Priscilla has lost the majority of its wind energy and is now effectively a blob of tropical moisture that is gradually combining with another tropical system.
This image shows the amount of water vapor in the atmosphere over northwestern Mexico and the southwestern United States. Red areas show dry air. Grey and pink zones reveal moisture. (AccuWeather Satellite)
Some downpours will fall on terrain in parts of northern Mexico, Arizona, southern Utah, western Colorado and western New Mexico. The arid landscape, steep elevations and rocky, hardpan soil prevent quick water absorption, which will cause flash floods and debris flows.
Persistent and heavy rainfall will increase the risk of flash flooding through canyons, river valleys and dry streambeds (arroyos).
Rainfall associated with Priscilla will generally range from 1-2 inches over the multi-state region in the Southwest. Since some of that may fall in a matter of a few hours, it can lead to flash flooding.
As if the rainfall from one tropical rainstorm wasn't enough, another dose may follow, spanning Sunday and Monday, from Tropical Storm Raymond. This second tropical system is the one likely to cause most of the trouble in parts of the Southweset.
Raymond is likely to track into Mexico farther south than Priscilla, but its rain will still extend into part of the U.S.
Rain from Raymond will overlap the area drenched by Priscilla in northern Mexico and the southwestern U.S. This next round of rain may reach farther to the southeast as well. In either case, too much rain will fall too fast and lead to a new surge of flash flooding.
Similar to Priscilla, rainfall totals of 4-8 inches are expected in some areas, with an AccuWeather Local StormMax™ of 10 inches.
Cities that could face the greatest risk of flash flooding include Tucson, Arizona; El Paso, Texas; and Las Cruces, New Mexico.
In areas affected by both tropical rainstorms, rainfall totals may reach 4-8 inches over five days. This magnitude of rainfall could lead to significant river flooding, along with flash flooding of small streams, urban areas and arroyos.
Where soaking rain falls that does not lead to flash flooding, it may ease drought conditions by providing a surge through area streams and slightly boosting some reservoir levels.
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