Raymond to raise flash flood risk in southwest U.S., northern Mexico
As tropical moisture from Raymond fluxes into the Southwest U.S. and northern Mexico, there will be heavy rain and an increased flood threat through the early week.
Raymond continues to lose wind intensity and has become a Tropical Rainstorm while moving onshore in western Mexico. Despite the National Hurricane Center discontinuing advisories, dangerous and damaging flash flooding will occur in northern Mexico and parts of Arizona and New Mexico into Tuesday.
"The heaviest rain looks to stay just south of the United States-Mexico border as the moisture that remains of Raymond interacts with the terrain," AccuWeather Meteorologist Haley Taylor said. "However, some significant moisture from Raymond will be pulled north into the southwestern United States, particularly in the southern parts of Arizona and New Mexico."
"While the flood risk remains high across the Four Corners states of Arizona, New Mexico, Utah and Colorado, into Monday, we're somewhat fortunate that Priscilla's moisture came up a bit farther west than Raymond's will," AccuWeather Senior Meteorologist John Feerick said. "If there had been a greater overlap, there likely would have been more widespread flooding problems."
Moisture from Priscilla caused downpours and thunderstorms over portions of the Southwest into Saturday.
The AccuWeather RealImpact™ Scale for Hurricanes and Tropical Storms for Raymond is one for Mexico and the United States. The RealImpact Scale takes into account many parameters ranging from rainfall and flooding to mudslides, travel disruptions, damage to property and risk to lives. The Saffir-Simpson Hurricane Scale only accounts for wind intensity. Long after a storm loses its strong winds, it can continue to cause significant risk to lives and property.
"For example, Phoenix received just over a third of an inch of rain from Thursday into Friday, putting them at 64% of their month's historical average rainfall," Taylor said. Flagstaff, Arizona, picked up 2.06 inches of rain from Priscilla, with just under an inch falling on Las Vegas.
Raymond's rounds of downpours look to stay largely just south of where the heaviest rain has already fallen from Priscilla.
"This will limit flash flooding concerns for some, but there will still be some overlap across Arizona," Taylor said, "Any rain that falls from this past weekend through the early week could lead to flash flooding, mudslides and other debris flows."
U.S. cities at greatest risk for flash flooding from Raymond, as a tropical rainstorm, include Tucson, Arizona, Las Cruces, New Mexico, and El Paso, Texas. The flash flood risk in these areas will ramp up Saturday night and continue into Monday.
There is some risk of flash flooding in Phoenix and Albuquerque, New Mexico, as well as Durango and Montrose, Colorado, as the moisture from Raymond extends farther north for a time. However, downpours in these areas will be sporadic and not widespread.
The mountains northeast of Phoenix are expect to pick up a general 2-4 inches of rain from Sunday to Tuesday. Locally higher amounts are possible with an AccuWeather Local StormMax™ rainfall of 10 inches in Mexico.
Farther to the north, a non-tropical storm will play a role in rainfall in the West.
"Salt Lake City is in the running for the 8th wettest October on record with 2.88" of rainfall so far," AccuWeather Senior Meteorologist Chad Merrill. "Priscilla's moisture teaming up with a non-tropical storm will bring more rain into Saturday night with the potential for flooding. Fortunately, Raymond's rain will stay well to the south on Sunday and Monday; otherwise, the flooding risk would continue into the early week."
Those on camping or hiking trips in the region, or traveling along secondary roads, should be prepared for sudden changes in conditions. Downpours that occur miles away can set off a flash flood even if the weather is dry overhead. There will also be locally severe thunderstorm activity associated with Raymond and the non-tropical storm farther to the north.
There is no question that rain is needed in the region, and the pattern in recent days and moving forward into upcoming week will provide some assistance.
AccuWeather meteorologists are monitoring the progress of a new storm for the western United States for upcoming week. That storm is forecast to bring the most significant single rainfall and Sierra Nevada snowfall for much of California since early in the spring.
"Since there are no signs of additional tropical systems to swing into the Southwest from the Pacific, the storm rolling into California should bring an end to any North American monsoon activity," AccuWeather Senior Meteorologist Dave Houk said.
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