Moisture associated with an increase in southerly winds brought showers and thunderstorms to northern Arizona. One of the thunderstorms brought heavy rain and flash flooding close to Snowflake.
Every event with a place to put it. Tap one for its entry below.
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 FGZ wrote it up.
Moisture associated with an increase in southerly winds brought showers and thunderstorms to northern Arizona. One of the thunderstorms brought heavy rain and flash flooding close to Snowflake.
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 Flagstaff, AZ wrote its last area forecast discussion before the first event at Sep 9, 3:41 PM MST, 17 minutes earlier.
Area Forecast Discussion National Weather Service Flagstaff AZ 341 PM MST Sat Sep 9 2017 .SYNOPSIS...Deep moisture will remain over northern Arizona into this evening, resulting in scattered shower and thunderstorm activity, especially over eastern Arizona. Cooler temperatures will continue through the weekend. Above average temperatures and a drying trend will return by early next week. && .DISCUSSION...Despite the ample moisture, daytime convection has been minimal over Coconino and Yavapai counties due to a cool boundary layer and cloud cover. The main areas of storm activity have been over far western Arizona, and more recently southern and central Navajo & Apache counties. This will be where the best chance of showers and storms will be for the next few hours, with most activity diminishing shortly after sunset. Localized areas of heavy rain are possible with the activity over eastern Arizona. The upper low off the central California coast has begun to shift southward, eventually reaching a position west of San Diego through around Tuesday. Meanwhile, high pressure will build eastward toward Arizona Sunday through Tuesday, bringing a somewhat drier flow and more stable conditions. There will still be enough moisture for isolated to scattered afternoon showers and storms, but these should be more terrain focused with a lower threat of heavy rain. By Wednesday, the upper low is forecast to start to move eastward toward our area as a deeper trough moves into the Pacific NW. This will bring an increase in southwest winds, along with a chance for some showers and thunderstorms as the trough moves through. There are some slight timing differences between models, so kept low rain chances in for Thursday to account for the slower solutions. Behind the initial trough, we should see some drier and cooler air Thursday into the weekend with daytime highs a few degrees below average. Occasionally breezy west winds are expected Thursday into the weekend as the trough over the northwest U.S. shifts east. Mostly clear to partly cloudy skies are expected with rain chances below 10 percent. && .AVIATION...For the 00z package...The largest area of thunderstorm activity has transitioned to along and east of I-17 and Highway 89. However, some thunderstorms and associated MVFR conditions could sneak into KPRC later this afternoon. All thunderstorm activity will decrease after 02z. KFLG-KSEZ could see a few thunderstorms after 20z Sunday. Aviation discussion not updated for TAF amendments. && .FIRE WEATHER...Thunderstorm activity over northern Arizona will gradually diminish early this evening. Less thunderstorm coverage is forecast for Sunday, with the greatest thunderstorm chances over the Mogollon Rim, Black Mesa, and Chuska Mountains. Monday through Thursday, only slight chances for afternoon thunderstorms are in the forecast each day over the higher terrain of northern Arizona. Breezy to windy southwesterly winds are forecast Wednesday and Thursday. && .FGZ WATCHES/WARNINGS/ADVISORIES...NONE. && PUBLIC...JJ AVIATION...TM FIRE WEATHER...TM For Northern Arizona weather information visit weather.gov/flagstaff
Hazardous Weather Outlook National Weather Service Flagstaff AZ 1231 PM MST Sat Sep 9 2017 AZZ004>018-037>040-100215- Kaibab Plateau-Marble and Glen Canyons-Grand Canyon Country- Coconino Plateau-Yavapai County Mountains- Northeast Plateaus and Mesas Hwy 264 Northward-Chinle Valley- Chuska Mountains and Defiance Plateau- Little Colorado River Valley in Coconino County- Little Colorado River Valley in Navajo County- Little Colorado River Valley in Apache County- Western Mogollon Rim-Eastern Mogollon Rim-White Mountains- Northern Gila County-Yavapai County Valleys and Basins- Oak Creek and Sycamore Canyons-Black Mesa Area- Northeast Plateaus and Mesas South of Hwy 264- 1231 PM MST Sat Sep 9 2017 This hazardous weather outlook is for Apache...Coconino... Northern Gila...Navajo...and Yavapai Counties in Northern Arizona. .DAY ONE...This Afternoon and Tonight Increased moisture will bring scattered to numerous showers and thunderstorms to northern Arizona this afternoon and early evening. The main threat with these storms will be lightning, with a lower threat of localized heavy rainfall and flooding. .DAYS TWO THROUGH SEVEN...Sunday through Friday By Sunday, chances for thunderstorms will continue, but the threat of heavy rainfall and flooding will decrease further. For Monday through Thursday, drier air moving into the region will lead to only a slight chance of showers and thunderstorms. .SPOTTER INFORMATION STATEMENT... Weather spotters are encouraged to report significant weather conditions according to standard operating procedures.
The Flagstaff radar (KFSX), 106 km away, was scanning. The volume nearest the first event began at 22:59 UTC.
1 flash flood. Local standard time, as filed.
A thunderstorm with heavy rain caused a flash flood in the normally dry Dry Silver Creek Wash. A video submitted by weather spotter showed the water to be around six feet deep.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Arizona in 2017Every state in 2017This day in weather historyWarnings in Arizona, September 2017
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: 721054.