Monsoon moisture over northern Arizona brought thunderstorms and heavy rain to the Verde Valley.
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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 FGZ wrote it up.
Monsoon moisture over northern Arizona brought thunderstorms and heavy rain to the Verde Valley.
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 26, 3:15 PM MST, 45 minutes earlier.
Area Forecast Discussion National Weather Service Flagstaff AZ 315 PM MST Sun Aug 26 2018 .SYNOPSIS...Isolated showers and thunderstorms will come to an end during the evening hours. Starting Monday, drier air moving across Arizona will lead to a significant downturn in shower and thunderstorm activity through much of the coming week. && .DISCUSSION...Over the coming days low pressure to the north of Arizona combined with high pressure over Texas/New Mexico will produce a drying southwest flow. The result will be a distinct downturn in shower and thunderstorm activity across northern Arizona this week. The remainder of this afternoon and tonight...Monsoon moisture will linger across northern Arizona resulting in isolated showers and thunderstorms. Enough vertical wind shear and instability exists for a few of these storms to become organized and severe with the main threat being hail up to quarter size. All activity is expected to come to an end by mid evening. Monday through Friday...A drying southwest flow will become established across northern Arizona. For the most part this drying will spell the end for shower and thunderstorm activity across the area. The only exception may be the White Mountains region where a very slight chance of storms will continue on Monday and then reemerge on Friday. The stronger southwest flow aloft will result in breezy conditions at times through the week with the strongest of these winds on Monday where gusts approaching 30 mph could be observed. Otherwise, near normal temperatures and just a few afternoon fair weather cumulus. Labor Day weekend...Models are showing some moisture increase across northern Arizona over the Labor Day weekend with even deeper moisture just to the south. At this time models are showing little to no shower or thunderstorm activity because the air mass remains to dry in the lower levels and too warm aloft (stable configuration). However, this time of year any hint toward a moisture increase must be respected. Thus, we upped the chance for showers and thunderstorms into the slight chance category for Saturday, Sunday and Labor Day. If you have plans for the Labor Day weekend, keep updated with the latest forecasts through the week. && .AVIATION...For the 00Z package...Mainly VFR conditions for the next 24 hours. Look for isolated thunderstorms ending by 03Z. For Monday, expect mainly clear skies with southwest wind 10-20 kts gusting to 25 kts. A slight chance of a stray storm along the Arizona/New Mexico border Monday afternoon. Aviation discussion not updated for TAF amendments. && .FIRE WEATHER...Much drier air will move across northern portions of Arizona on Monday and Tuesday with only a slight chance of storms over the White Mountains. Expect lower humidity and breezy afternoon southwest winds both days. Wednesday through Friday...A drier air mass will bring mostly clear skies to northern Arizona. Other than a few afternoon fair weather cumulus look for locally breezy southwest winds with temperatures near normal for late August. A slight chance for showers and storms will return to the White Mountains on Friday. && .FGZ WATCHES/WARNINGS/ADVISORIES...NONE. && PUBLIC...McCollum AVIATION...McCollum FIRE WEATHER...McCollum For Northern Arizona weather information visit weather.gov/flagstaff
Special Weather Statement National Weather Service Flagstaff AZ 1201 PM MST SUN AUG 26 2018 AZZ012-015-261930- Little Colorado River Valley in Coconino County-Western Mogollon Rim- 1201 PM MST SUN AUG 26 2018 ...SIGNIFICANT WEATHER ADVISORY FOR COCONINO COUNTY UNTIL 1230 PM MST... At 1200 PM MST, Doppler radar was tracking a strong thunderstorm near Wupatki National Monument, or 28 miles north of Flagstaff, moving northeast at 10 mph. Dime size hail and winds in excess of 40 mph will be possible with this storm. Locations impacted include... Wupatki National Monument and Wupatki Visitors Center. PRECAUTIONARY/PREPAREDNESS ACTIONS... Torrential rainfall is also occurring with this storm, and may lead to localized flooding. Do not drive your vehicle through flooded roadways. Frequent cloud to ground lightning is occurring with this storm. Lightning can strike 10 miles away from a thunderstorm. Seek a safe shelter inside a building or vehicle. && LAT...LON 3547 11142 3556 11153 3573 11139 3559 11120 TIME...MOT...LOC 1900Z 218DEG 9KT 3557 11145 MCT
Special Weather Statement National Weather Service Flagstaff AZ 145 PM MST SUN AUG 26 2018 AZZ009-012-013-040-262130- Little Colorado River Valley in Navajo County- Little Colorado River Valley in Coconino County- Northeast Plateaus and Mesas Hwy 264 Northward- Northeast Plateaus and Mesas South of Hwy 264- 145 PM MST SUN AUG 26 2018 ...SIGNIFICANT WEATHER ADVISORY FOR NAVAJO AND COCONINO COUNTIES UNTIL 230 PM MST... At 145 PM MST, Doppler radar was tracking strong thunderstorms along a line extending from near Tuba City to 9 miles west of Tolani Lake. Movement was east at 10 mph. Dime size hail and winds in excess of 40 mph will be possible with these storms. Locations impacted include... Tuba City, Tolani Lake, Coalmine Canyon Chapter House, Tonalea, Moenkopi, Hopi and Hopi Reservation. PRECAUTIONARY/PREPAREDNESS ACTIONS... Frequent cloud to ground lightning is occurring with these storms. Lightning can strike 10 miles away from a thunderstorm. Seek a safe shelter inside a building or vehicle. && LAT...LON 3635 11096 3538 11058 3538 11107 3611 11134 TIME...MOT...LOC 2045Z 271DEG 8KT 3607 11124 3548 11100 MCT
Special Weather Statement National Weather Service Flagstaff AZ 258 PM MST SUN AUG 26 2018 AZZ006-007-262230- Coconino Plateau-Grand Canyon Country- 258 PM MST SUN AUG 26 2018 ...SIGNIFICANT WEATHER ADVISORY FOR COCONINO COUNTY UNTIL 330 PM MST... At 257 PM MST, Doppler radar was tracking a strong thunderstorm 15 miles northwest of Valle, or 33 miles southwest of Desert View at Grand Canyon, moving east at 20 mph. Nickel size hail and winds in excess of 40 mph will be possible with this storm. Locations impacted include... Ten-x Campground. PRECAUTIONARY/PREPAREDNESS ACTIONS... Frequent cloud to ground lightning is occurring with this storm. Lightning can strike 10 miles away from a thunderstorm. Seek a safe shelter inside a building or vehicle. && LAT...LON 3572 11232 3588 11237 3598 11198 3577 11193 TIME...MOT...LOC 2157Z 252DEG 17KT 3580 11234 MCT
Special Weather Statement National Weather Service Flagstaff AZ 304 PM MST SUN AUG 26 2018 AZZ008-037-038-262230- Yavapai County Valleys and Basins-Yavapai County Mountains-Oak Creek and Sycamore Canyons- 304 PM MST SUN AUG 26 2018 ...SIGNIFICANT WEATHER ADVISORY FOR YAVAPAI COUNTY UNTIL 330 PM MST... At 304 PM MST, Doppler radar was tracking a strong thunderstorm near Cottonwood, or 15 miles northwest of Camp Verde, moving east at 10 mph. Nickel size hail and wind gusts up to 50 mph will be possible with this storm. Locations impacted include... Clarkdale, Verde Village, Bridgeport, Cottonwood, Cornville, Jerome, Dead Horse Ranch State Park, Mingus Mountain Campground, Playground Group Campground, Potato Patch Campground and Tuzigoot National Monument. PRECAUTIONARY/PREPAREDNESS ACTIONS... Torrential rainfall is also occurring with this storm, and may lead to localized flooding. Do not drive your vehicle through flooded roadways. Frequent cloud to ground lightning is occurring with this storm. Lightning can strike 10 miles away from a thunderstorm. Seek a safe shelter inside a building or vehicle. && LAT...LON 3460 11214 3474 11218 3484 11194 3464 11186 TIME...MOT...LOC 2204Z 252DEG 10KT 3470 11207 MCT
The Flagstaff radar (KFSX), 73 km away, was scanning. The volume nearest the first event began at 23:00 UTC.
1 flash flood, 1 heavy rain. Local standard time, as filed.
Several roads in Cottonwood were closed with as much as 3 feet of water covering them. Two of the intersections included 6th Street at Boulder Lane and South Camino Real Road at East Fir Street.
Heavy rain (2.20 inches) fell in one hour in Cottonwood. Nickle hail also fell. This rain lead to flash flooding in town.
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: 786439, 786445.