Strong thunderstorms developed across portions of south central Arizona, including the greater Phoenix area, during the late afternoon and evening hours on August 18th. The storms produced strong gusty outflow winds which caused a dust storm over the lower deserts, including portions of the greater Phoenix area and western Pinal counties. Damaging microburst winds and locally heavy rain accompanied the strong storms.

Dust Storm in CENTRAL DESERTS, ARIZONA
From 18-AUG-11 16:00:00 to 18-AUG-11 18:00:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Intense thunderstorms developed over portions of central Pinal county during the afternoon hours on August 18th. The storms produced strong and gusty outflow winds in excess of 50 mph which moved towards the northwest and generated a significant haboob. The haboob moved from the Eloy/Casa Grande/Coolidge area towards the northwest and into the greater Phoenix metropolitan area. The haboob was at least 2000 feet high and 50 miles wide. Between 4 and 430 pm, several trained spotters in the Coolidge and Casa Grande area reported a dust storm with visibilities at or below one quarter mile. At 5 pm, zero visibility in dense blowing dust was reported along the Hunt Highway in the San Tan valley. The haboob significantly disrupted the rush hour traffic across northwest Pinal county. Fortunately no major accidents or injuries were reported.

Thunderstorm Wind in PINAL, ARIZONA
From 18-AUG-11 16:50:00 to 18-AUG-11 16:50:00 (MST-7)
Location: MAGMA
Magnitude: 52.00 EG
Property damage: 30.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorms with damaging microburst winds affected the San Tan Valley area during the afternoon hours on August 18th. A trained National Weather Service storm spotter 4 miles west of Magma reported that 1 foot diameter trees were blown down. Additionally, a roof was blown off of a house. Wind speeds were estimated to be at least 60 mph. Hail one quarter inch in diameter occurred in association with the strong storms.

Thunderstorm Wind in PINAL, ARIZONA
From 18-AUG-11 16:54:00 to 18-AUG-11 16:54:00 (MST-7)
Location: MAGMA
Magnitude: 50.00 EG
Property damage: 225.00K
Crop damage: 0.00K
Reported by: Utility Company

Thunderstorms with damaging microburst winds affected the area around Magma during the afternoon hours on August 18th. According to a report from the local utility company, approximately 30 power poles were blown down in the Johnson Ranch area, along the Hunt highway near Judd road. Winds were estimated to be in excess of 50 knots.

Thunderstorm Wind in PINAL, ARIZONA
From 18-AUG-11 16:59:00 to 18-AUG-11 17:00:00 (MST-7)
Location: MAGMA
Magnitude: 50.00 EG
Property damage: 30.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Strong thunderstorms with damaging microburst winds moved through the San Tan Valley during the late afternoon hours on August 18th. Area law enforcement personnel reported that power lines were down at Bella Vista and Gantzel roads, and at least one of the lines fell onto a school bus from the Florence Unified school district. The bus driver and four children that were aboard were not injured.

Thunderstorm Wind in MARICOPA, ARIZONA
From 18-AUG-11 17:21:00 to 18-AUG-11 17:21:00 (MST-7)
Location: OCOTILLO
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorms with strong gusty winds developed over the southeastern portion of the greater Phoenix area during the afternoon hours of August 18th. A trained weather spotter approximately 5 miles east of Sun Lakes estimated a peak wind gust to 60 mph. The strong winds were associated with a dust storm moving through the area; at the same time visibility had lowered to less than one quarter of a mile.

Dust Storm in GREATER PHOENIX AREA, ARIZONA
From 18-AUG-11 17:00:00 to 18-AUG-11 19:30:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Strong thunderstorms developed over the south central deserts during the late afternoon hours on August 18th. The strong outflow winds from the storms generated a dust storm which moved steadily from the southeastern valley towards the northwest from approximately 5 pm through 8 pm. Much of the greater Phoenix area was affected. A number of trained weather spotters reported visiblities down to one quarter of a mile or below in dense blowing dust. A weather spotter 5 miles east of Sun Lakes reported visibility below one quarter of a mile in blowing dust at 520 pm. At 523 pm the official weather station at Mesa Gateway airport measured a visibility of one quarter mile.

Flash Flood in PINAL, ARIZONA
From 18-AUG-11 17:00:00 to 18-AUG-11 18:30:00 (MST-7)
Location: MAGMA
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Amateur Radio

Thunderstorms with locally heavy rainfall developed in the area around Magma during the late afternoon hours on August 18th. Rainfall, with rates estimated in excess of one inch per hour, led to flash flooding on the Hunt Highway west of Magma. The flooding was reported by an amateur radio operator.

Thunderstorm Wind in MARICOPA, ARIZONA
From 18-AUG-11 18:30:00 to 18-AUG-11 18:30:00 (MST-7)
Location: ENNIS
Magnitude: 54.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Broadcast Media

Strong thunderstorms moved across the greater Phoenix metropolitan area during the early evening hours of August 18th. According to local broadcast media sources, a wind gust measured at 62 mph occurred at Zuni Hills elementary school, located about 3 miles northwest of Sun City. No damage was reported at the school.