Widespread monsoon thunderstorms developed across the greater Phoenix metropolitan area during the evening hours on August 23rd; the storms brought typical weather hazards to the area including urban flooding and flash flooding, gusty and damaging outflow winds and one inch diameter hail. Storms affected areas from Apache Junction westward through central Phoenix and north into the Carefree and Cave Creek areas. Wind gusts were measured to be as high as 73 mph with the stronger storms. Gusty outflow winds downed a number of trees, such as mesquite trees, and downed a large highway sign onto the Loop 101 freeway near 56th street. There were numerous instances of flooding, from urban street flooding to flash flooding that necessitated water rescues. A large number of Flash Flood Warnings, Flood Advisories, Severe Thunderstorm Warnings and Significant Weather Advisories were issued during this monsoon event.

Flash Flood in MARICOPA, ARIZONA
From 23-AUG-18 18:00:00 to 23-AUG-18 20:40:00 (MST-7)
Location: PHOENIX TURF ARPT
Flood cause: Heavy Rain
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Public

Thunderstorms with very heavy rain moved across the northern portions of the greater Phoenix area during the evening hours on August 23rd; some of the stronger storms produced intense rain with peak rain rates well in excess of one inch per hour; the heavy rain was sufficient to lead to some flash flooding in north Phoenix. According to a report from the general public, at 1836MST flash flooding was observed 5 miles southeast of Deer Valley; there was significant neighborhood flooding in the area near Sunset Hills, just northeast of Lookout Mountain. The report was relayed via Twitter. A Flash Flood Warning was in effect at the time; it was issued at 1800MST and it remained in effect through 2040MST.

Heavy Rain in MARICOPA, ARIZONA
From 23-AUG-18 18:00:00 to 23-AUG-18 20:00:00 (MST-7)
Location: PHOENIX
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorms with heavy rain developed and moved across the central portions of the greater Phoenix area, including area around downtown Phoenix, during the early evening hours on August 23rd. The heavy rain, with peak rain rates above one inch per hour, led to some significant street flooding in the areas northwest of Phoenix Sky Harbor Airport. According to a trained weather spotter, at 1844MST street flooding was ongoing along 16th Street, just to the south of Interstate 10. Despite hazardous driving conditions, the street flooding did not result in any accidents.

Thunderstorm Wind in MARICOPA, ARIZONA
From 23-AUG-18 17:45:00 to 23-AUG-18 18:15:00 (MST-7)
Location: PHOENIX TURF ARPT
Magnitude: 61.00 EG
Property damage: 3.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorms with strong, damaging outflow winds moved across the northern portions of the greater Phoenix metropolitan area during the early evening hours on August 23rd. Some of the storms affected communities such as Deer Valley and north Phoenix. According to a trained weather spotter 5 miles southeast of Deer Valley, at 1745MST gusty wind estimated to be as high as 70 mph toppled a mature Mesquite tree with a trunk diameter of nearly 20 inches. The downed tree was on the west side of Lookout Mountain. About one half hour later, another trained spotter 4 miles southeast of Deer Valley reported a smaller Mesquite tree blown down with a diameter of about 6 inches. The second tree was downed near the intersection of Bell Road and 9th Street. No injuries were reported.

Thunderstorm Wind in MARICOPA, ARIZONA
From 23-AUG-18 18:09:00 to 23-AUG-18 18:09:00 (MST-7)
Location: CACTUS
Magnitude: 63.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Thunderstorms with very strong outflow winds moved through the central and northern portion of the greater Phoenix metropolitan area during the early evening hours on August 23rd. One of the stronger storms affected portions of north Phoenix. At 1809MST a mesonet weather station labeled DW6996 measured a wind gust to 73 mph. The station was located about 7 miles northwest of Paradise Valley, or just west of the intersection of Highway 51 and Northern Avenue in north Phoenix. No damage was reported in the location of the strong downburst.

Flash Flood in MARICOPA, ARIZONA
From 23-AUG-18 17:00:00 to 23-AUG-18 19:45:00 (MST-7)
Location: CAVE CREEK
Flood cause: Heavy Rain
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Broadcast Media

Thunderstorms with very heavy rain developed and moved higher terrain locations to the northeast of Phoenix during the evening hours on August 23rd. Some of the stronger storms affected the communities of Carefree and Cave Creek. The intense rain with peak rain rates well in excess of one inch per hour was sufficient to cause episodes of flash flooding.  According to a report from local broadcast media, at 1750MST area washes 1 mile south of Cave Creek were running with water; significant water was flowing across the road near the intersection of the Carefree Highway and Cave Creek Road. At 1802MST, another report from local media indicated flash flooding 1 miles northeast of Cave Creek; the flash flooding was observed across Spur Cross Road and there was significant water across the roadway. A Flash Flood Warning was issued for the area at 1652MST and it remained in effect through 1945MST.

Flash Flood in MARICOPA, ARIZONA
From 23-AUG-18 18:00:00 to 23-AUG-18 20:40:00 (MST-7)
Location: CLEARWATER HILLS
Flood cause: Heavy Rain
Property damage: 20.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorms with very heavy rain developed and moved across central and northern portions of the greater Phoenix metropolitan area during the evening hours on August 23rd. Some of the stronger storms generated intense rain with peak rain rates well in excess of one inch per hour; the heavy rain was sufficient to cause episodes of flash flooding across north Phoenix. According to a trained weather spotter located 7 miles northwest of Paradise Valley, at 1835MST flash flooding was occurring; streets were flooding and washes were running near the intersection of 12th Street and Northern Avenue. Shortly after that a broadcast media report was received indicating flash flooding 6 miles northeast of Glendale; there was a water rescue reported near 13th Avenue and Hatcher Road. This report was relayed by Fox 10 news. A Flash Flood Warning was in effect at the time; it was issued at 1800MST and remained in effect through 2040MST. There were no reports of injury due to the flash flooding.

Thunderstorm Wind in MARICOPA, ARIZONA
From 23-AUG-18 19:36:00 to 23-AUG-18 19:36:00 (MST-7)
Location: CHANDLER ARPT
Magnitude: 57.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: AWOS

Thunderstorms with strong gusty outflow winds moved across the southeast portion of the greater Phoenix metropolitan area during the evening hours and one of the stronger storms affected the community of Chandler. At 1936MST the official AWOS weather station at the Chandler Municipal Airport measured a wind gust of 66 mph. No damage was reported at the airport.

Thunderstorm Wind in MARICOPA, ARIZONA
From 23-AUG-18 17:35:00 to 23-AUG-18 17:35:00 (MST-7)
Location: SCOTTSDALE MUNI
Magnitude: 61.00 EG
Property damage: 30.00K
Crop damage: 0.00K
Reported by: Department of Highways

Thunderstorms with strong damaging outflow winds moved across the northern portion of the greater Phoenix area during the evening hours on August 23rd; one of the stronger storms affected north Scottsdale.  According to the Department of Highways, at 1735MST gusty winds estimated to be as high as 70 mph blew down a large highway sign onto the Loop 101 Freeway near 56th Street. The downed sign was slightly to the northwest of the TPC Scottsdale Golf Course. The downed sign was blocking the lane and creating hazardous driving conditions; fortunately no reports of accident were received.

Flash Flood in MARICOPA, ARIZONA
From 23-AUG-18 18:00:00 to 23-AUG-18 20:40:00 (MST-7)
Location: CLEARWATER HILLS
Flood cause: Heavy Rain
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Newspaper

Thunderstorms with very heavy rain moved across central and northern portions of the greater Phoenix metropolitan area during the evening hours on August 23rd. The stronger storms produced peak rain rates well in excess of one inch per hour and this was sufficient to produce episodes of flash flooding. As reported by a local newspaper along with social media, at 1825MST flash flooding resulted in significant flooding throughout a neighborhood near the intersection of Shea Boulevard and State Route 51. The report was relayed by AZ Central via Twitter. No injuries were reported. A Flash Flood Warning was in effect at the time; it was issued at 1800MST and remained in effect through 2040MST.

Hail in MARICOPA, ARIZONA
From 23-AUG-18 18:06:00 to 23-AUG-18 18:16:00 (MST-7)
Location: CACTUS
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Thunderstorms developed across the northern portion of the greater Phoenix area during the early evening hours on August 23rd; one of the stronger storms affected the communities of Paradise Valley and north Phoenix. At 1816MST, the public reported nickel to quarter sized hailstones falling near the intersection of 17th Street and Mountain View Road, not far to the northwest of the intersection of Highway 51 and Northern Avenue in north Phoenix. The diameter of the largest stones was about one inch. No damage was reported due to the large hail.

Flash Flood in PINAL, ARIZONA
From 23-AUG-18 20:30:00 to 23-AUG-18 23:30:00 (MST-7)
Location: PALM SPGS
Flood cause: Heavy Rain
Property damage: 25.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorms with very heavy rain developed across the eastern portion of the greater Phoenix metropolitan area during the evening hours on August 23rd; some of the stronger storms generated peak rain rates approaching 2 inches per hour which led to episodes of flash flooding in the community of Apache Junction. According to a trained spotter located 2 miles south of Apache Junction, at 2100MST washes were running along Baseline Road east of Ironwood Drive. Baseline Road was completely underwater in places between Ironwood Drive and Tomahawk Drive due to the flash flooding. Further to the north, and a bit later, the Arizona Department of Highways reported flash flooding across Apache Junction with many roads closed due to the flooding. The report, from the official city Twitter account, was received at about 2200MST. A number of roads were mentioned, including Tomahawk Road, Ironwood Drive and Southern Avenue. A Flash Flood Warning for the area was issued at 2028MST and it was in effect until 2330MST.