Flash Flooding and Damaging Winds in Arizona, August 8 to 9, 2018

Thunderstorms with gusty and damaging outflow winds moved across the eastern portion of the greater Phoenix area, including the community of Mesa, during the early evening hours on August 8th. Some of the storms generated outflow winds well in excess of 50 mph. According to a a trained weather spotter located about 1 mile northwest of Mesa, at 1830MST strong winds estimated to be as high as 70 mph downed a large tree; the tree was then blown onto a nearby Apartment building. The damage occurred near the intersection of Country Club Drive and Rio Salado Parkway. There were no injuries reported due to the fallen tree.

Thunderstorms with gusty and damaging outflow winds moved across the northern portion of the greater Phoenix area during the evening hours on August 8th. Some of the stronger storms affected the northern portion of the town of Scottsdale. According to a report from local broadcast media, gusty winds estimated to be near 65 mph downed numerous power lines. The downed lines were in northern Scottsdale, north of the Pima Freeway and along Scottsdale Road. The numerous downed power lines trapped people in 7 cars; fortunately no injuries were reports. There were no reports of power poles downed however.

Thunderstorms developed over the eastern portion of greater Phoenix area, and over higher terrain, during the evening hours on August 8th. Some of the storms produced very strong and gusty outflow winds. A mesonet automatic weather station 5 miles west of Saguaro Lake measured a wind gust to 64 mph at 1923MST. The station was along the Salt River and north of the Bush Highway.

Thunderstorms with strong and gusty outflow winds developed over the east and southeast portions of the greater Phoenix area during the evening hours on August 8th. Some of the storms affected communities such as Queen Creek and San Tan Valley. According to a member of the public located 5 miles southeast of Queen Creek, at 1923MST winds estimated as high as 70 mph downed 6 power poles. The downed poles were near the Hunt Highway at Gary Road, just to the northwest of San Tan Valley. No injuries were reported due to the strong winds.

Thunderstorms with strong and gusty outflow winds moved through the central and northern portions of the greater Phoenix metropolitan area during the evening hours on August 8th; some of the stronger storms affected the community of Scottsdale. Some of the stronger wind gusts led to significant damage to trees and power poles. According to a report from local broadcast media, at 1927MST gusty winds estimated to be as high as 75 mph downed numerous trees and power poles in Scottsdale, near the intersection of Thomas Road and Hayden Road. About 30 minutes later, at 2000MST, a trained spotter less than one mile to the west reported trees downed and damage at the Coronado Golf Course near the intersection of Scottsdale Road and Thomas Road. The spotter did not specify the type of damage that occurred. No injuries were reported due to the strong winds or falling trees.

Thunderstorms with gusty outflow winds developed over the higher terrain east of Phoenix during the evening hours, and some of them moved into the community of Fountain Hills. A COOP observer located 2 miles east of Fountain Hills reported a wind gust to 62 mph at 1930MST. The observer did not report any damage.

Thunderstorms with strong and gusty outflow winds developed across the eastern portion of the greater Phoenix area, including the community of Mesa, during the evening hours on August 8th. Some of the stronger storms generated gusty outflow winds in excess of 50 mph. According to a report from the public, at 1930MST gusty winds estimated as high as 70 mph downed a large tree. The downed tree was located about 2 miles north of East Mesa and near the intersection of McKelllips Road and Power Road. No injuries were reported.

Thunderstorms with locally heavy rains developed over the higher terrain areas to the northeast of Phoenix during the evening hours on August 8th. Some of the storms generated intense rainfall with peak rain rates approaching 2 inches per hour. The rain led to some flash flooding in the area around Fountain Hills. According to a report from the public, at 2100MST a road about 2 miles northeast of Fountain Hills was closed due to deep flowing water across the road at a low water crossing. This flash flooding was actually captured in a video. A Flash Flood Warning was issued for the area at 1921MST and it remained in effect until 2115MST. Additionally, the heavy rains resulted in a heavy flows in some of the washes in the warned area; a stream gauge at the Reata Pass Wash reported a rise of one and one half feet.

Thunderstorms with locally heavy rain developed across the higher terrain areas northeast of central Phoenix during the evening hours on August 8th; some of the peak rain rates with stronger storms approached 2 inches per hour and this led to episodes of flash flooding to the northeast of north Scottsdale and Paradise Valley. At 2001MST a county official indicated that the Reata Pass Wash displayed a very rapid rise of one and one half feet. The stream gauge at the wash indicated that it passed the alarm stage of 1.6 feet; this historically impacts low water crossings on Pima Road in the area. The flooding was located about 5 miles northeast of north Scottsdale, just to the southeast of Troon Mountain and north of the McDowell Mountains. A Flash Flood Warning was issued for the area at 1921MST and it remained in effect until 2115MST.

Thunderstorms with locally heavy rain developed across the central portions of the greater Phoenix metropolitan area during the evening hours on August 8th; some of the stronger storms affected areas around the town of Paradise Valley. Peak rain rates with the stronger storms were in excess of one inch per hour and resulted in some street flooding in the area. According to a trained spotter about 1 mile southeast of Paradise Valley, curb-to-curb street flooding was observed at about 1950MST. The flooding was just west of Scottsdale Road and between Jackrabbit Road and McDonald Drive. An Urban and Small Stream Flood Advisory was eventually issued for the area at 2018MST and it remained in effect until 2215MST.

Thunderstorms with strong gusty outflow winds moved across the northern portion of the greater Phoenix area during the evening hours on August 7th. Some of stronger storms affected the community of Scottsdale. At 1931MST The official ASOS weather station at the Scottsdale Municipal Airport measured a wind gust to 59 mph.

Thunderstorms with strong and gusty outflow winds moved across the eastern portions of the greater Phoenix area during the evening hours and some of the stronger storms affected areas around the community of Mesa. At 1940MST a report was received from a local utility company; he indicated that a wind gust of 59 mph was observed about 5 miles northwest of East Mesa and near the intersection of McDowell Road and Greenfield Road. He did not report any damage associated with the strong winds.

Thunderstorms with gusty outflow winds moved through the central portion of the greater Phoenix area during the evening hours on August 8th. Some of the stronger storms affected the area around Arizona State University. According to a report received from the public, gusty winds estimated to be upwards of 65 mph downed multiple trees 2 miles north of the University and just northeast of the Rolling Hills Golf Course. The report also indicated that the trees were downed near the intersection of 68th Street and Mckellips Road. No injuries were reported.

Thunderstorms with strong gusty outflow winds moved through the downtown portion of the greater Phoenix area during the evening hours on August 8th. The official ASOS weather station at Phoenix Sky Harbor Airport measured a gust to 63 mph at 1951MST. Damage was not reported at the airport however.

Thunderstorms with strong and gusty outflow winds developed across the central portion of the greater Phoenix area, including the community of Tempe, during the evening hours on August 8th. Some of the stronger wind gusts were sufficient to cause damage over portions of north Tempe. According to a trained weather spotter near the Shalimar Golf Course, at 1958MST gusty winds estimated to be at least 75 mph in strength snapped a flagpole in half. The damage occurred at 1924 East Wesleyan Drive in Tempe. A few minutes earlier, at 1955MST, a trained spotter located 1 mile east of Arizona State University reported a large branch downed onto the light rail near the intersection of Apache Boulevard and McClintock Road. The winds that downed the branch were estimated to be around 60 mph.

Thunderstorms with strong gusty outflow winds developed over the central portion of the greater Phoenix metropolitan area during the evening hours on August 8th. Some of the stronger storms affected portions of the community of Tempe and at about 2000MST multiple reports were received of large tree damage just south of the Superstition Freeway or Highway 60. According to a trained spotter located 3 miles southeast of Tempe, just south of Highway 60, gusty winds estimated as high as 75 mph downed a number of trees on the Loop 101 freeway near Highway 60 and the Guadalupe Road on-ramp. The damage occurred at about 2001MST. The trees and tree debris resulted in a significant driving hazard to motorists on the Loop 101. At the same time, a public report was received indicating many tree branches as well as whole trees were snapped and downed near the intersection of Rural road and Guadalupe Road. No injuries were reported due to the strong gusty winds.

Thunderstorms with strong gusty outflow winds moved across the central portion of the greater Phoenix area during the evening hours on August 8th. Some of the stronger storms affected the area around Phoenix Sky Harbor International Airport. At 2000MST a trained spotter 2 miles south of the airport reported that gusty winds uprooted and downed a large tree that he estimated to be 100 feet tall. Wind gusts were estimated to be 70 mph; at the exact same time the official ASOS weather station at the airport measured a wind gust of 63 mph.

Thunderstorms with strong and gusty outflow winds moved across western portions of the greater Phoenix area during the evening hours, and some of them affected the town of Buckeye. At 2015MST, the official ASOS weather station at the Buckeye Municipal Airport measured a wind gust to 58 mph.

Thunderstorms with gusty and damaging outflow winds moved across the eastern portion of the greater Phoenix area, including the community of Mesa, during the evening hours on August 8th. According to a trained weather spotter located 2 miles northwest of Mesa, at 2016MST outflow winds estimated to be at least 60 mph in strength broke off a number of tree limbs and also produced damage to some shingles near the intersection of Alma School Road and the Rio Salado Parkway.

Thunderstorms with strong and gusty outflow winds moved through the eastern portion of the greater Phoenix area, including the community of Mesa, during the evening hours on August 8th. Some of the stronger wind gusts from the storms resulted in significant tree damage. According to a trained spotter located 3 miles southwest of Mesa, at 2018MST gusty outflow winds estimated at 75 mph downed a very large tree at the Mesa Community College. The tree, with a diameter of 3 feet, was uprooted near the intersection of Dobson Road and Southern Avenue.

Thunderstorms with strong and gusty winds moved through the downtown portion of the greater Phoenix area during the evening hours on August 8th and affected areas around Phoenix Sky Harbor International Airport. According to a trained weather spotter 2 miles northwest of the airport, at 2019MST gusty winds estimated to be at least 65 mph in strength downed a tree; the tree landed on the Loop 202 Freeway near the intersection of Interstate 10. The tree presented a hazard to motorists on the freeway. No accidents were reported despite the hazardous driving conditions.

Thunderstorms with strong and gusty outflow winds moved through central and northern portions of the greater Phoenix area during the evening hours on August 8th. Some of the stronger storms affected the community of Scottsdale. According to a trained weather spotter 3 miles southeast of Scottsdale, at 2019MST gusty winds estimated to be as high as 65 mph downed a number of trees near the intersection of Pima Road and McDowell Road, just west of the Loop 101 Freeway. In addition, the gusty winds blew over some construction barricades in the area.

Thunderstorms with very heavy rain developed across the central portions of the greater Phoenix metropolitan area during the evening hours on August 8th; some of the stronger storms produced peak rainfall rates in excess of one inch per hour and this led to some flash flooding in Scottsdale, including the Indian Bend Wash. According to a mesonet stream gauge reports, flash flooding occurred in the Indian Bend Wash at the Murray Road crossing at approximately 2300MST. The upstream gauge measured a rise of over 2.5 feet in the wash as heavy flow developed down the wash. After midnight, at 0048MST on August 9th, a trained spotter indicated that flash flooding in Indian Bend Wash resulted in a swift water rescue at Murray Lane; a car with 2 passengers was caught in one foot of swiftly moving water in the wash. No injuries were reported however. A Flash Flood Warning was issued for the area at 2030MST and it remained in effect through 2330MST. A warning was not in effect during the early morning swift water rescue.