Phoenix, AZ hail storm history

What the National Weather Service wrote

A slow-moving low pressure system brought several rounds of showers and thunderstorms over multiple days through much of the region. Activity on the 25th was mostly concentrated across higher terrain areas of eastern AZ, fueled by MLCAPE values approaching 2000 J/kg. Strong to severe thunderstorms developed during the afternoon hours, producing rainfall accumulations of over 2 inches in less than one hour across the Miami area leading to significant flash flooding. Multiple streets became rushing currents of water, floodwaters escaped Bloody Tanks Wash in several locations and flooded businesses, there was a lot of muddy and rocky debris, and there were several minor landslides. Severe hail was observed with the thunderstorm activity as well.

Read the full description

The most impactful day of this multi-day episode occurred on the 26th when widespread thunderstorm activity developed across much of south-central AZ as strong upper-level divergence from the low pressure system moved overhead. Fueled by MLCAPE values near 2000 J/kg and near 30 kts of 0-6 km shear, scattered thunderstorms developed in the Phoenix area during the mid-morning hours with increasing coverage through the afternoon hours. Initially, most of the storm reports received were large hail, however, as activity became more widespread the hazard quickly turned to flash flooding with numerous reports of water rescues. A fatality due to drowning was reported in Indian Bend Wash in Scottsdale when the individual's vehicle became submerged by significant floodwaters. A few hours after the rainfall dissipated in the Phoenix area, a new area of strong to severe thunderstorms, with very heavy rainfall, moved eastward into southern Gila County, affecting the Globe/Miami area for a second time in just over 24 hours. Gauge reports and doppler radar estimates out of the Globe area measured approximately 2 of rain, with most of the rain occurring in less than 30 minutes. A stream gauge along Pinal Creek, just south of downtown Globe, reported a 6 foot water rise in 30 minutes. Subsequently, videos and images emerged from downtown Globe depicting catastrophic flooding as the flood wave in Pinal Creek overtopped bridges, inundated businesses, and flooded or swept away numerous vehicles. Around 800 propane tanks were also swept into the floodwaters from a nearby distribution center. Around 66 vehicles were recovered and approximately 288 tons of trash and debris, as well as 8000 cubic yards of dirt, were cleared. The flooding claimed three lives.

Additional shower and thunderstorm activity materialized on the 27th as the low pressure system was still over southern CA. The more widespread activity was concentrated across portions of southwest AZ during the morning and early afternoon hours with instances of flash flooding reported. Additional activity did develop across south-central AZ as well, including across portions of the Phoenix area, during the afternoon hours. Coverage was more isolated compared to the 26th, but the storms still produced additional flash flooding and severe winds gusts. A thunderstorm cell once again moved through the already flood ravaged area of Globe/Miami in the afternoon. Despite rainfall amounts remaining under an inch with this storm, due to quick storm motion, flash flooding occurred once again in the area, exacerbated by the very saturated soils from the rainfall the previous two days.

Following this three-day episode, local, state, and federal disaster declarations were made for the Globe area, a disaster assistance center was opened, and approximately 600 initial and preliminary damage assessments were conducted by AZ Department of Emergency and Military Affairs, finding around 200 private and public properties were destroyed, with the rest experiencing some scale of damage. Not all events are captured in detail in this episode due to the large scale and number of the impacts. Damage cost estimates were in the millions.