A major Mesoscale Convective System pushed moisture back northward over Arizona during the night. This system also induced a Gulf of California moisture surgel, pushing dew points along the Lower Colorado river to near 80.
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The episode as NWS FGZ wrote it up.
A major Mesoscale Convective System pushed moisture back northward over Arizona during the night. This system also induced a Gulf of California moisture surgel, pushing dew points along the Lower Colorado river to near 80. This allowed a strong thunderstorm to form over the Goodwin Fire scar that produced flash flooding.
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 Aug 10, 4:15 PM MST, 1 hour 25 minutes earlier.
Area Forecast Discussion National Weather Service Flagstaff AZ 415 PM MST Thu Aug 10 2017 .SYNOPSIS...Expect a return to more typical monsoon weather conditions through the weekend. A weak trough moving northwest by later tonight and tomorrow may cause activity to persist into the overnight hours. && .DISCUSSION...Decent convective coverage this afternoon, especially over the western zones. So far, there has been enough of a cap to keep activity from getting out of control. To the east, substantial debris cloud that was pushed out ahead of a decaying MCS has kept convection to a minimum. An inverted trough that caused the MCS last night will start to slowly move northwest tonight and north on Friday in response to deepening low pressure over the northern Great Basin. This will mean several active days for Arizona, probably through the weekend. Models still showing westerly flow aloft next week, with a drying trend becoming probable. && .AVIATION...For the 00Z package...Scattered showers and tstorms will continue into the evening hours along and south of a KGCN-KFLG-KSOW line, isolated to the north. All activity diminishing to isolated light showers after 07z. VFR conditions overall for the period with local MVFR/IFR conditions near heavier thunderstorms. Look for a better chance of showers and thunderstorms on Friday. Aviation discussion not updated for TAF amendments. && .FIRE WEATHER...Monsoon moisture will spread back across Arizona as the flow turns southerly, bringing an increasing chance of showers and thunderstorms on Friday and Saturday. Sunday through Tuesday...Moisture will remain over the region with scattered afternoon and evening thunderstorms. Temperatures will be near to slightly below normal. && .FGZ WATCHES/WARNINGS/ADVISORIES...NONE. && PUBLIC...Peterson AVIATION...McCollum FIRE WEATHER...McCollum For Northern Arizona weather information visit weather.gov/flagstaff
Hazardous Weather Outlook National Weather Service Flagstaff AZ 506 AM MST Thu Aug 10 2017 AZZ004>018-037>040-111200- 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- 506 AM MST Thu Aug 10 2017 This hazardous weather outlook is for Apache...Coconino... Northern Gila...Navajo...and Yavapai Counties in Northern Arizona. .DAY ONE...Today and Tonight An increase in monsoon moisture will bring the return of thunderstorms to the area today and tonight. Scattered storms will develop this afternoon and may last well into the evening and overnight hours as a disturbance moves north through Arizona. Lightning and local areas of heavy rain with flooding are the main concerns. .DAYS TWO THROUGH SEVEN...Friday through Wednesday Expect more typical monsoon season weather conditions through the weekend with daily chances for showers and thunderstorms. Drier air will bring decreasing thunderstorm activity next week. .SPOTTER INFORMATION STATEMENT... Weather spotters are encouraged to report significant weather conditions according to standard operating procedures.
The Flagstaff radar (KFSX), 84 km away, was scanning. The volume nearest the first event began at 00:39 UTC.
1 flash flood. Local standard time, as filed.
A thunderstorm produced heavy rain over the Goodwin Fire scar that caused flash flooding on the Agua Fria River. The stream gauge went from 1 foot to 4.91 feet during the flash flood.
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, August 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: 720623.