Isolated thunderstorms developed across the southwest portion of Yuma county during the afternoon hours on September 30th, the final day of the Arizona monsoon. Moisture was already spreading north and into southwest Arizona ahead of Hurricane Rosa and the moisture was sufficient to allow strong storms to develop; some of the stronger storms formed just to the east of Yuma, producing gusty and damaging winds as well as very heavy rainfall. A trained spotter near Fortuna Foothills reported that just over 1.8 inches of rain fell between 1300MST and 1500MST and the rain led to flash flooding in the Fortuna Wash. At about 1300MST, four mobile homes lost awnings just east of Yuma due to microburst winds, and tree damage occurred as well. A flash flood warning was issued for the area around Fortuna Foothills at roughly 1400MST.

Flash Flood in YUMA, ARIZONA
From 30-SEP-18 15:00:00 to 30-SEP-18 17:00:00 (MST-7)
Location: LIGURTA
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Tropical moisture spread north and into southwest Arizona ahead of Hurricane Rosa on October 30th, and the moisture led to the formation of isolated thunderstorms. Some of the stronger storms produced very heavy rainfall in the area east of Yuma and  around the Fortuna Foothills. Trained spotters in the area reported rain totals over 1.8 inches near the Fortuna Foothills during the early afternoon; the intense rain led to flash flooding. At 1545MST a trained spotter in the Fortuna Foothills reported flash flooding over the Fortuna Wash near 40th Street and Ironwood. A Flash Flood Warning was issued for the area at 1404MST and it remained in effect through 1700MST. No injuries were reported as a result of the flash flooding.

Flash Flood in YUMA, ARIZONA
From 30-SEP-18 13:00:00 to 30-SEP-18 17:00:00 (MST-7)
Location: LIGURTA
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Tropical moisture was spreading north and into southwest Arizona on September 30th, ahead of hurricane Rosa. The moisture led to the formation of isolated thunderstorms, some of which produced intense rainfall just to the east of Yuma. A trained spotter 1 mile southeast of Fortuna Foothills measured 1.84 inches of rain between 1300MST and 1500MST. At about 1400MST the same spotter reported a wash running over the streets at 40th Avenue and Driftwood Drive. Area roads such as Driftwood Drive were impassable due to the flooding.

Thunderstorm Wind in YUMA, ARIZONA
From 30-SEP-18 12:50:00 to 30-SEP-18 12:54:00 (MST-7)
Location: (YUM)YUMA INTL ARPT
Magnitude: 56.00 EG
Property damage: 15.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Tropical moisture spread into southwest Arizona on September 30th ahead of hurricane Rosa. The moisture was sufficient to allow isolated thunderstorms to develop; some of the stronger storms generated gusty damaging microburst winds that affected the community of Yuma. According to a trained weather spotter, at about 1300MST gusty outflow winds estimated to be at least 65 mph in strength destroyed the awnings on four mobile homes located 2 miles southeast of Yuma. The strong winds also downed a number of tree limbs in the area. No injuries were reported due to the damaging winds.