Scattered thunderstorms moved slowly northwest across southeast Arizona. Heavy rain caused flash flooding in Pima and Pinal Counties and especially in Marana where up to three inches of rain caused widespread flash flooding and considerable damage including a train derailment from rapidly flowing flood waters.
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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 northwest across southeast Arizona. Heavy rain caused flash flooding in Pima and Pinal Counties and especially in Marana where up to three inches of rain caused widespread flash flooding and considerable damage including a train derailment from rapidly flowing flood waters.
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 Jul 10, 9:44 AM MST, 3 hours 11 minutes earlier.
Area Forecast Discussion National Weather Service Tucson AZ 944 AM MST Tue Jul 10 2018 .SYNOPSIS...Moisture streaming into southern Arizona will continue to generate showers and thunderstorms with a focus on the afternoon and evening hours. Some of the thunderstorms will produce heavy rains and strong winds. Cooler than average temperatures will also continue thanks to the cloud cover and showers. && .DISCUSSION...Lots of moisture around this morning with sfc dewpoints in the 60s. 12z sounding had PWAT values of 1.76 inches, just 0.10" shy of the record for this date. Already seeing new TS development in Sonora where morning cloud cover was the thinnest. Remnant showers still present in Pinal and NC Pima county this morning and an ongoing MCS in W New Mexico edging into Greenlee Co. Storms will move N to NW today instead of W to SW as was the case the past couple of days since we are now on the east side of the inverted trough. Initially expect new thunderstorm development to be concentrated in Santa Cruz and Cochise Co. then spread NW across SE AZ. Heavy rain will be the main concern. Storm motions of 15 mph or greater should limit rainfall from one storm over a given location, but still expect high enough rainfall rates to create issues in flood prone areas. Areas SE of Tucson where initial development occurs have not seen a lot of rain the past few days, so they should generally be able to handle more rainfall. Less heating today may reduce storm growth enough to limit wind gusts, but cannot completely rule out isolated wind damage. Abundant moisture should remain over SE AZ through at least this weekend with a continued chance for showers and thunderstorms through the period. && .AVIATION...Valid through 11/18Z. TSRA/SHRA will increase in coverage this afternoon and move in a NLY direction. -TSRA/-SHRA WILL decrease in coverage again after 11/06z. Expect MVFR CIGS/VSBYs in +RA, MT obscurations and gusts to 45 kts with the strongest storms. Otherwise, surface winds SSELY 5-15kts. Aviation discussion not updated for TAF amendments. && .FIRE WEATHER...The pattern remains favorable for isolated to scattered thunderstorm development throughout the forecast period. Other than strong outflows around afternoon thunderstorms, 20-ft winds hold below 15 mph shifting from an easterly component today to more typical diurnal flow tomorrow and beyond. && .PREV DISCUSSION...A very active afternoon yesterday from Tucson west to the California border and while it has settled down, we continue to have showers moving across the region early this morning. The flow has turned southeast on the backside of the inverted trough that passed across the area and this is evident in the NW movement of the showers and isolated thunderstorms. These are expected to continue the next 2-5 hours before tapering off later this morning. Then the focus turns to what may be in store for this afternoon and evening. Plenty of moisture and instability in place so it won't take much to kick things off. I'm in agreement with WPC that unlike the last few days, areas roughly from Tucson south and east are under the gun this afternoon and evening. Various model solutions point to this region including local CAM solutions and I agree as I can see this area breaking out into some sunshine behind this band of light showers to set things off. With the levels of PW and CAPE along with a lower level of DCAPE, the primary concern will be locally heavy rains in the strongest storms as they move generally south to north, especially with the potential for a couple of rounds of storms. Also expecting isolated showers and thunderstorms to continue well into and possibly through the night. Thankfully this area has been relatively dry the last few days which will help, however we will need to keep an eye on our Lizard and Frye burn scars over the next 24 hours. Also, as is usually the case, will need to be ready for the occasional strong wind producing storm. With the abundant shower activity expected today, high temperatures will be held back a good 4-8 degrees from long term normals. For Wednesday the inverted trough that worked its way across the area will have shifted well west of the region leaving behind weak mid- level ridging which should attempt to suppress the convection. With the moisture and instability available along with the weak nature of the ridging, it won't completely hold back the convection, likely just hold back the start time and the overall number of storms. The same can be said of Thursday, so basically scattered afternoon and evening storms primarily east of a Tucson/Nogales line. The Friday through the weekend period should take a turn toward being wetter again as models continue to indicate a shortwave rotating around the upper level high and moving across southern Arizona likely enhancing convection. So at this time I started the process of raising pops a bit at this time frame and maintaining the cooler than normal afternoon temperatures. && .TWC WATCHES/WARNINGS/ADVISORIES...None. && Drozd Visit us on Facebook...Twitter...YouTube...and at weather.gov/Tucson
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE TUCSON AZ
840 AM MST TUE JUL 10 2018
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0235 PM TSTM WND DMG 10 ENE SELLS 31.98N 111.73W
07/09/2018 PIMA AZ EMERGENCY MNGR
POWER POLE DOWNED.
0450 PM TSTM WND DMG 12 WSW CHUICHU 32.65N 111.97W
07/09/2018 PINAL AZ EMERGENCY MNGR
SEVEN POWER POLES DOWNED.
&&The Tucson radar (KEMX), 43 km away, was scanning. The volume nearest the first event began at 19:54 UTC.
2 flash flood, 1 heavy rain, 1 thunderstorm wind. Local standard time, as filed.
A driver lost control of her vehicle on I-10 east of Benson due to heavy rain and wet roads and hydroplaned into a palo verde tree.
Thunderstorm winds blew a tree down near Cortaro Farms and Magee Roads.
Thunderstorms produced 2 to 3 inches of rain in around on hour on both sides of I-10 from Cortaro to Twin Peaks which caused flash flooding. Some of these areas had als received 1 to 2 inches of rain two days earlier. Many roads and intersections were closed due to flash flooding on the northwest side of Tucson encompassing an area from Tangerine Rd and I-10 down to Ina Rd and I-10. First responders performed at least eight swift water rescues of motorists. A restaurant and animal shelter were also flooded, along with damage to Sanctuary Cove foot trail. A total of 8 swift water rescues had to be performed. Flood waters damaged railroad tracks and derailed over two dozen Union Pacific railroad cars north of Twin Peaks Road, causing extensive damage and closing the access road to Interstate 10 for several days.
Flash flooding caused off ramps along I-10 in the Eloy and Picacho areas to become impassable.
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, July 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: 775144, 773848, 773863, 775143.