Isolated slow moving thunderstorms occurred mainly across Pima County during the afternoon and evening hours, and produced pockets of heavy rain. One storm caused flash flooding on the Tohono O'odham Nation.
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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.
Isolated slow moving thunderstorms occurred mainly across Pima County during the afternoon and evening hours, and produced pockets of heavy rain. One storm caused flash flooding on the Tohono O'odham Nation.
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 Aug 16, 1:18 PM MST, 3 hours 42 minutes earlier.
Area Forecast Discussion National Weather Service Tucson AZ 118 PM MST Thu Aug 16 2018 .SYNOPSIS...Scattered thunderstorms will diminish later this evening with skies gradually clearing. Then fairly typical monsoon conditions are forecast for Friday well into next week with the exception of Sunday which may be mainly dry. After a relatively cool afternoon today, warmer high temperatures are in the forecast through much of next week. && .DISCUSSION...Convection already developing across western Pima county this afternoon and the storms are quick to produce decent rains according to radar estimates. As we progress further into the afternoon the coverage of thunderstorms is expected to increase with a threat of a few of them producing very heavy rains thanks in large part to the abundant moisture in the atmosphere. A flash Flood Watch is in effect for the SW part of the forecast area with the main area of concern being generally west of I-19. The convection will die off fairly quickly this evening after 7-8 pm with skies clearing during the overnight hours. By Friday afternoon the upper level high that is currently just to our SE will have settled overhead which will help to suppress convective development to a certain degree. We will have plenty of moisture in place and enough instability that we should be able to produce some convection over higher terrain mainly east and south of Tucson. Temperatures during the afternoon will rebound to mid August normals. For the Saturday through Wednesday time period, the upper level high will meander back and forth across the SW resulting in varying amounts of convection from one day to the next. At this time Sunday looks to be be a significant down day convection wise if the current models are anywhere near to being correct. Time will tell. Afternoon temperatures will be near to or slightly warmer than normal under this scenario and will vary a few degrees each day depending on the amount and exact location of any convection. Further out, the Climate Center's outlooks continue to indicate somewhat wetter than normal conditions on average through the next 3 to 4 weeks overall. Monsoon 2018 continues && .AVIATION...Valid through 18/00Z. Isolated to scattered -SHRA/-TSRA develop this afternoon and evening, decreasing in coverage after sunset. Brief MVFR conditions possible with the -TSRA. Otherwise SCT-BKN cloud bases generally 8- 12k ft AGL this afternoon and evening with another BKN later AOA 20k ft AGL. Tomorrow afternoon isolated to scattered -SHRA/-TSRA will again be possible mainly from Tucson eastward. Outside of thunderstorm gusts, expect SFC winds mainly less than 12 kts. Aviation discussion not updated for TAF amendments. && .FIRE WEATHER...The pattern is favorable for scattered showers and thunderstorms through Saturday, with lower rain chances and drier conditions by Sunday. Rain chances will increase again early next week. Near or slightly below average temperatures will continue through the forecast period. 20-ft winds will be terrain driven at less than 15 mph, except for in and around thunderstorms where strong outflows may occur. && .TWC WATCHES/WARNINGS/ADVISORIES... Flash Flood Watch until 8 PM MST this evening for AZZ501>504-507- 513>515. && PUBLIC...Carpenter AVIATION....Hardin FIRE WEATHER...Hardin Visit us on Facebook...Twitter...YouTube...and at weather.gov/Tucson
The Phoenix radar (KIWA), 181 km away, was scanning. The volume nearest the first event began at 00:01 UTC.
1 flash flood. Local standard time, as filed.
About 1.5 inches of rain fell between 330 pm and 500 pm causing flash flooding along the Ali Chuk Wash. This made Route 1 impassable for vehicles for about two hours.
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, August 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: 782005.