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Heavy Rain Targets Plains, Southwest

September 22, 2019
UPDATED By WeatherBug Meteorologist, Andrew Rosenthal
Multiple tropical systems are teaming up to produce significant flood potential from the Plains to the Desert Southwest over the next few days.
 
This amalgam of tropical trouble includes moisture from former Tropical Storm Imelda on the Atlantic side, and Tropical Storms Lorena and Mario in the Eastern Pacific. With a cold front acting to focus all of the moisture from Texas to Wisconsin, the result will be very heavy rainfall.
 
The first ingredient is the remnants of Tropical Storm Imelda, which came ashore earlier this week and brought very heavy rainfall to Texas and Louisiana. Although the low-pressure center has dissipated, its moisture drifted into the Plains and toward an approaching cold front.
 
Meanwhile, two tropical systems are flirting with Baja California this weekend. As Tropical Depression Lorena closes in on the U.S./Mexico border today, Tropical Depression Mario will follow behind it through Baja California as it continues to weaken through midweek.
 
The cold front over the central U.S. is pulling tropical moisture from both storms toward the U.S., with all of that moisture being squeezed out as heavy rain and thunderstorms. Flash flooding is the primary threat over the next few days, with 2 to 4 inches of rain possible in the next couple of days from the Texas Panhandle to southern Wisconsin. Flash Flood Watches have been issued for this area, including Oklahoma City, Kansas City, the Quad Cities region, Chicago and Milwaukee.
 
In addition to the drenching downpours, isolated severe thunderstorms are possible across the central Plains and Lower Midwest today. Warm and humid air ahead of the front is battling cooler and drier air shifting southward across Nebraska and Iowa, leading to some powerful boomers. These storms will bring gusty winds of 60 to 70 mph, hail to the size of golf balls and possibly even a few tornadoes.
 
Not to be missed in this cavalcade of storms is Lorena’s final push into the Desert Southwest. The dying tropical system is poised to make a rare Pacific storm appearance across the U.S. border by Monday morning, bringing heavy rainfall and thunderstorms to Arizona. One to three inches of rain is expected to start the new work week across the Phoenix area, likely turning typically dry washes into raging rivers.
 
If you come across water in the road, do not attempt to cross it, as it is likely deeper and running much faster than it appears. Remember, “Turn Around, Don’t Drown!”
 
Pacific tropical systems delivering moisture into the Plains isn’t that unusual, nor is tropical moisture moving into the Southwest following hurricane landfall; however, actual storm remnants usually only affect Arizona about once every four to five years. Those survivor storms can be drenchers – Hurricane Nora in 1997 brought 3 to 5 inches to metro Phoenix, and locally as much as 10 inches.