Scattered thunderstorms moved slowly southeast across portions of southeast Arizona from late morning on the 1st through the morning of the 2nd. Pockets of heavy rain totaling between 1 and 4 inches occurred in northeast Pinal County, southwest Graham County and Cochise County.
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Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS TWC wrote it up.
Scattered thunderstorms moved slowly southeast across portions of southeast Arizona from late morning on the 1st through the morning of the 2nd. Pockets of heavy rain totaling between 1 and 4 inches occurred in northeast Pinal County, southwest Graham County and Cochise County. Flash flooding was observed over the Frye Fire burn scar on Mount Graham and on Interstate 10 near Bowie.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Tucson, AZ wrote its last area forecast discussion before the first event at Sep 1, 9:35 AM MST, 4 hours 25 minutes earlier.
Area Forecast Discussion National Weather Service Tucson AZ 935 AM MST Sat Sep 1 2018 .SYNOPSIS...Expect isolated to scattered showers and thunderstorms especially from Tucson eastward through Labor Day. Daytime temperatures will generally be a few degrees below normal. A gradual drying trend will then occur later next week, with the bulk of thunderstorms mainly east of Tucson. && .DISCUSSION...There has been quite a bit of thunderstorm activity across east-central and Northeast Arizona over the past 6 hours as a few vorticity lobes track thru the the southern periphery of an upper trough positioned over Nevada/Utah. The favorable dynamics with this upper feature this morning are currently N and NE of our CWA in NE AZ and WRN NM. However, as the upper trough begins to sag south, it will result in another upper diffluent field establishing itself across the eastern portions of the forecast area this afternoon into Sunday. The 01/12Z KTWC upper air sounding indicated ample moisture still present in the lower-to-middle layers of the atmosphere with a PWAT value of 1.40 inches. It also indicated the warm air layer aloft last evening has eroded away, allowing for a more favorable environment for sustained convection. The majority of the Hi-Res models are in agreement with convection firing up from Tucson east this afternoon. Given the developing diffluent field aloft, I am leaning more toward the 01/12Z UofA WRFNAM solution which maintains convection overnight, especially along the AZ and New Mexico border. This is also reflected to a lesser extent by the 01/12Z HRRR and 01/12Z HREF ARW models. Given the moist airmass in effect, we will likely have to pay attention to rainfall amounts along the AZ/NM border resulting in minor small stream flooding issues(FLS) through Sunday. Otherwise...the mean upper trough remains over SE AZ Monday and slowly nudges to the east by the middle of next week as the upper ridge in the Eastern Pacific shifts NE into California. Although this would keep the WRN portions of the forecast area dry this week, enough instability will exist to the east of Tucson...especially if this trough phases up with an inverted trough west moving along the southern periphery of the upper high moving into the Great Basin next weekend. && .AVIATION...Valid through 02/18Z. Scattered -TSRA/-SHRA KTUS vicinity eastward into Sunday. Isolated -TSRA/-SHRA may also occur west of KTUS this afternoon. SCT-BKN clouds 8k-12k ft AGL areawide, with clearing west of Tucson late tonight. Surface wind variable in direction mainly less than 12 kts, though brief gusts to 40 kts near TSRA. Aviation discussion not updated for TAF amendments. && .FIRE WEATHER...Scattered thunderstorms east of Tucson with lesser coverage and precipitation chances west of Tucson through Labor Day. A gradual drying trend will evolve to isolated thunderstorms mostly east of Tucson by the middle of the upcoming week. Expect terrain driven 20-foot winds at less than 15 mph, except brief strong gusts near thunderstorms. && .PREV DISCUSSION...A cluster of thunderstorms managed to develop after midnight near the San Carlos Reservoir, and were tracking eastward through the Upper Gila River Valley at this time. Latest HRRR solution picked up on this area of rainfall and showed an area of further development along the Rim into the White Mountains through daybreak. Thereafter, the HRRR showed some scattered showers and thunderstorms developing across southeast Arizona from near Tucson and east through southeast of there after 18Z today. Both the ECMWF and GFS models continued to suggest a noticeable upswing in thunderstorms today and more so Sunday into early Monday as the tail end of a system swings through the state. Along with the increase in rain chances, daytime temperatures will drop a few degrees on today and level off next week with readings near normal. Drier conditions will return by Tuesday, with most of the thunderstorm activity remaining confined to far eastern Arizona and the mountains. && .TWC WATCHES/WARNINGS/ADVISORIES...None. && Visit us on Facebook...Twitter...YouTube...and at weather.gov/Tucson
Special Weather Statement National Weather Service Tucson AZ 1030 AM MST SAT SEP 1 2018 AZZ509-511-011815- Upper Gila River and Aravaipa Valleys including Clifton/Safford-Galiuro and Pinaleno Mountains including Mount Graham- 1030 AM MST SAT SEP 1 2018 ...SIGNIFICANT WEATHER ADVISORY FOR SOUTH CENTRAL GRAHAM COUNTY UNTIL 1115 AM MST... At 1029 AM MST, Doppler radar was tracking a strong thunderstorm over the Pineleno Mountains or 15 miles southwest of Safford, moving east at 5 mph. Dime size hail and wind gusts up to 50 mph will be possible with this storm. Locations impacted include... Safford, Thatcher, Pima, Swift Trail Junction, Mount Graham and Frye Mesa Dam. LAT...LON 3257 10990 3278 11004 3300 10982 3278 10961 TIME...MOT...LOC 1729Z 265DEG 4KT 3274 10995
Special Weather Statement National Weather Service Tucson AZ 1232 PM MST SAT SEP 1 2018 AZZ504-012000- Tucson Metro Area including Tucson/Green Valley/Marana/Vail- 1232 PM MST SAT SEP 1 2018 ...SIGNIFICANT WEATHER ADVISORY FOR EAST CENTRAL PIMA COUNTY UNTIL 100 PM MST... At 1231 PM MST, Doppler radar was tracking a strong thunderstorm over Tucson. This storm was nearly stationary. Dime size hail and wind gusts up to 50 mph will be possible with this storm. Locations impacted include... Tucson, Drexel-Alvernon, Flowing Wells, Tanque Verde, South Tucson, Catalina Foothills, Sabino Canyon and Davis-Monthan Air Force Base. PRECAUTIONARY/PREPAREDNESS ACTIONS... Heavy rainfall is also occurring with this storm, and may lead to localized flooding. Do not drive your vehicle through flooded roadways. && LAT...LON 3216 11100 3229 11099 3234 11080 3214 11081 TIME...MOT...LOC 1931Z 272DEG 4KT 3221 11093
Special Weather Statement National Weather Service Tucson AZ 200 PM MST SAT SEP 1 2018 AZZ507>509-511-012145- Upper Gila River and Aravaipa Valleys including Clifton/Safford-Upper San Pedro River Valley including Sierra Vista/Benson-Eastern Cochise County Below 5000 Feet including Douglas/Willcox-Galiuro and Pinaleno Mountains including Mount Graham- 200 PM MST SAT SEP 1 2018 ...SIGNIFICANT WEATHER ADVISORY FOR SOUTH CENTRAL GRAHAM AND NORTH CENTRAL COCHISE COUNTIES UNTIL 245 PM MST... At 200 PM MST, Doppler radar was tracking a strong thunderstorm 15 miles west of Willcox, moving east at 5 mph. Half inch hail and winds in excess of 40 mph will be possible with this storm. This storm will remain over mainly remote areas of south central Graham and north central Cochise Counties. PRECAUTIONARY/PREPAREDNESS ACTIONS... Heavy rainfall is also occurring with this storm, and may lead to localized flooding. Do not drive your vehicle through flooded roadways. && LAT...LON 3224 11013 3241 11018 3249 10991 3223 10986 TIME...MOT...LOC 2100Z 260DEG 6KT 3234 11009 ECC
The Tucson radar (KEMX), 117 km away, was scanning. The volume nearest the first event began at 20:57 UTC.
2 flash flood. Local standard time, as filed.
Thunderstorms produced 1 to 2 inches of rain over the Frye Fire burn scar early in the afternoon. This caused flash flooding along the creeks on east side of the burn scar.
Thunderstorms produced periods of heavy rain totaling 2 to 3 inches during the early morning hours. Interstate 10 near Bowie was closed in both directions due to flash flooding. Several swift water rescues were performed.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Arizona in 2018Every state in 2018This day in weather historyWarnings in Arizona, September 2018
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 785943, 785976.