Flooding downpours, locally severe storms to threaten parched southwestern US this week
By
Renee Duff, AccuWeather senior meteorologist
Published Sep 22, 2019 10:05 AM EDT
Ongoing downpours over parts of the southwestern United States will be beneficial for the ongoing drought but could pose the risk for flash flooding through Wednesday night.
Drought conditions have grown considerably across the Southwest over the past few months due to a lackluster monsoon season. While Arizona was free of drought during the middle of June, over 85 percent of the state has succumbed to moderate to severe drought, according to the latest outlook by the U.S. Drought Monitor.
While the rainfall will go a long way in helping to ease the dry conditions, it has cause and will continue to trigger incidents of flash flooding over the arid terrain.
Arizona is likely to remain the main target for widespread showers and thunderstorms, as well as flash flooding concerns, through Tuesday, with lesser impacts in surrounding areas, according to AccuWeather Senior Meteorologist and western U.S. blogger Brian Thompson.
On Monday morning, the Storm Prediction Center (SPC) issued a severe thunderstorm watch for parts of central and western Arizona. This is the first time a severe thunderstorm watch has been issued in northwestern Arizona since July 18, 2015.
A potent storm system in the upper levels of the atmosphere will dive southward across the West into midweek. At the same time, tropical moisture will surge northward from the eastern Pacific Ocean.
These two factors will combine to generate the widespread downpours.
An AccuWeather Local StormMax™ of 6 inches is forecast in Arizona during this event.
"While the rainfall is needed, if the rain comes in bursts from heavier thunderstorms, flash flooding will be a big concern, especially in mountainous and urban areas like Phoenix and Tucson, Arizona," Thompson said.
People should avoid dry stream beds, known as arroyos, which may suddenly fill with a torrent of water.
The excessive rainfall can also trigger mudslides and other debris flows over the hilly and mountainous terrain.
The Arizona Department of Transportation was alerting motorists of the heavy rain threat on Twitter, reminding them to inspect windshield wipers and slow down when the rain starts.
Motorists will also need to be on the lookout for flooded roadways. Remember to turn around and find a safer, alternate route when high water is encountered.
"Aside from the heavy rain, flooding and mudslide threats, strong thunderstorms will be a possibility as well," Thompson said.
The strongest thunderstorms can contain large hail and damaging winds, with the period into Tuesday likely posing the highest threat for these hazards.
"The threat for at least spotty showers and thunderstorms will probably linger into Wednesday and Thursday and may spread into some desert regions of southeastern California," Thompson said.
The rainfall should douse active blazes across the region and substantially lower the risk of new wildfire ignition.
However, it will be a different story on the northwestern side of the storm system, where warm, dry winds will heighten the fire danger in Northern California into Wednesday.
"We're now heading into prime wildfire season across California, so staying on guard is important," Thompson said.
By the end of the week, the fire danger will likely decrease in Northern California as a significant, winterlike storm is expected to target the West.
This new storm has the potential to bring a significant reduction in temperatures and unleash a large amount of early-season snow in the northern Rockies.
Download the free AccuWeather app to stay aware of the latest forecast for your area. Keep checking back for updates on AccuWeather.com and stay tuned to the AccuWeather Network on DirecTV, Frontier and Verizon Fios.
Report a Typo
News / Weather News
Flooding downpours, locally severe storms to threaten parched southwestern US this week
By Renee Duff, AccuWeather senior meteorologist
Published Sep 22, 2019 10:05 AM EDT
Ongoing downpours over parts of the southwestern United States will be beneficial for the ongoing drought but could pose the risk for flash flooding through Wednesday night.
Drought conditions have grown considerably across the Southwest over the past few months due to a lackluster monsoon season. While Arizona was free of drought during the middle of June, over 85 percent of the state has succumbed to moderate to severe drought, according to the latest outlook by the U.S. Drought Monitor.
While the rainfall will go a long way in helping to ease the dry conditions, it has cause and will continue to trigger incidents of flash flooding over the arid terrain.
Arizona is likely to remain the main target for widespread showers and thunderstorms, as well as flash flooding concerns, through Tuesday, with lesser impacts in surrounding areas, according to AccuWeather Senior Meteorologist and western U.S. blogger Brian Thompson.
On Monday morning, the Storm Prediction Center (SPC) issued a severe thunderstorm watch for parts of central and western Arizona. This is the first time a severe thunderstorm watch has been issued in northwestern Arizona since July 18, 2015.
A potent storm system in the upper levels of the atmosphere will dive southward across the West into midweek. At the same time, tropical moisture will surge northward from the eastern Pacific Ocean.
These two factors will combine to generate the widespread downpours.
An AccuWeather Local StormMax™ of 6 inches is forecast in Arizona during this event.
Related:
"While the rainfall is needed, if the rain comes in bursts from heavier thunderstorms, flash flooding will be a big concern, especially in mountainous and urban areas like Phoenix and Tucson, Arizona," Thompson said.
People should avoid dry stream beds, known as arroyos, which may suddenly fill with a torrent of water.
The excessive rainfall can also trigger mudslides and other debris flows over the hilly and mountainous terrain.
The Arizona Department of Transportation was alerting motorists of the heavy rain threat on Twitter, reminding them to inspect windshield wipers and slow down when the rain starts.
Motorists will also need to be on the lookout for flooded roadways. Remember to turn around and find a safer, alternate route when high water is encountered.
"Aside from the heavy rain, flooding and mudslide threats, strong thunderstorms will be a possibility as well," Thompson said.
The strongest thunderstorms can contain large hail and damaging winds, with the period into Tuesday likely posing the highest threat for these hazards.
"The threat for at least spotty showers and thunderstorms will probably linger into Wednesday and Thursday and may spread into some desert regions of southeastern California," Thompson said.
The rainfall should douse active blazes across the region and substantially lower the risk of new wildfire ignition.
However, it will be a different story on the northwestern side of the storm system, where warm, dry winds will heighten the fire danger in Northern California into Wednesday.
"We're now heading into prime wildfire season across California, so staying on guard is important," Thompson said.
By the end of the week, the fire danger will likely decrease in Northern California as a significant, winterlike storm is expected to target the West.
This new storm has the potential to bring a significant reduction in temperatures and unleash a large amount of early-season snow in the northern Rockies.
Download the free AccuWeather app to stay aware of the latest forecast for your area. Keep checking back for updates on AccuWeather.com and stay tuned to the AccuWeather Network on DirecTV, Frontier and Verizon Fios.
Report a Typo