More than 15 million Americans are facing a potentially dangerous week of severe rainfall as forecasters warn that three separate weather systems are combining to produce an unusually widespread flood threat.
Flood watches have been issued across 10 states, with the most significant impacts expected initially across the Southwest and southern Plains before the system spreads farther east.
Three weather systems are combining
Meteorologists say moisture associated with Hurricane Polo is combining with remnants of Hurricane Odalys and a dip in the jet stream over the United States.
The interaction is expected to create a broad area of heavy rainfall capable of producing rapid flooding in vulnerable communities.
The heaviest rainfall on Tuesday is forecast across Arizona, Colorado, New Mexico, Kansas, Oklahoma and Texas, although the threat is expected to persist and shift across the country throughout the week.
Rainfall could become dangerously intense
AccuWeather meteorologist Brandon Buckingham warned that the most intense periods could produce rainfall rates of 2 to 3 inches per hour.
Such rainfall can overwhelm drainage systems and cause normally manageable waterways to rise rapidly, creating dangerous conditions for motorists and residents in flood-prone areas.
AccuWeather forecasts that some locations could receive as much as eight inches of rain during the week, while isolated areas could face a worst-case scenario of up to 18 inches.
Flood watches stretch beyond the Southwest
The initial flood threat is not limited to the states expected to receive the heaviest rainfall.
Flood watches have also been issued for Utah, Nebraska, Missouri and Iowa, while the broader storm system is expected to push moisture into additional parts of the Midwest.
AccuWeather forecasts that more than two inches of rainfall could reach Arkansas, Illinois, Indiana, Michigan and Wisconsin by Friday.
The developing pattern means communities far from the initial storm zone could still face flooding later in the week.
Arizona and New Mexico face immediate flash-flood danger
The National Weather Service has already issued flash flood warnings in parts of Arizona and New Mexico, highlighting the immediate danger posed by intense rainfall.
Officials have issued a particular warning to motorists, urging drivers never to attempt to cross roads covered by floodwater.
The NWS has stressed that driving into flooded roadways is among the most common causes of flood-related deaths.
Several states could see extreme rainfall totals
The combination of prolonged rainfall and periods of exceptionally heavy precipitation has raised concerns about significant flooding across a large section of the country.
Parts of Colorado, Iowa, Kansas, Missouri, Nebraska, New Mexico, Oklahoma and Texas are among the areas facing the possibility of several inches of rain.
The most extreme scenarios could result in substantially higher totals in isolated locations, particularly where repeated thunderstorms move over the same areas.
The threat will continue through the week
Although Tuesday is expected to bring some of the most significant rainfall across the Southwest and Plains, forecasters say the broader threat is likely to continue as the weather system moves eastward.
The rainfall could eventually extend from the desert Southwest towards the Great Lakes, bringing additional flooding concerns to communities that may not initially be affected.
Residents in areas under flood watches are being urged to monitor updated forecasts, prepare for rapidly changing conditions and avoid unnecessary travel during periods of intense rainfall.
Officials urge motorists to take no chances
The greatest immediate concern is the potential for rapidly rising water on roads and in low-lying areas.
Even relatively shallow floodwater can conceal damaged road surfaces or sweep vehicles away, making an apparently passable road extremely dangerous.
With rainfall rates potentially reaching several inches per hour, authorities are urging residents to take warnings seriously and seek safer routes rather than attempting to drive through flooded areas.
