A significant increase in monsoon moisture brought scattered thunderstorms to Yavapai County with strong and damaging winds.
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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.
A significant increase in monsoon moisture brought scattered thunderstorms to Yavapai County with strong and damaging winds.
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 16, 9:11 AM MST, 4 hours 53 minutes earlier.
Area Forecast Discussion National Weather Service Flagstaff AZ 911 AM MST Sun Aug 16 2020 .SYNOPSIS...Widely scattered thunderstorms should develop this afternoon along the Mogollon Rim. These should move southwestward with gusty outflow winds across Yavapai and Gila Counties. The very hot temperatures that threaten daily record high temperatures to continue into midweek. Dangerous heat is forecast at lower elevations. && .DISCUSSION...We have updated todayS forecast to add or increase storm chances along the Mogollon Rim from Flagstaff to the White Mountains, northern Gila and Yavapai Counties. There has been a significant moisture increase overnight into these areas. Hi res models are showing scattered storms to develop today, first along the rim from Heber to Alpine. Storms and their outflow boundaries to push to the southwest through the afternoon. Otherwise, the heat will continue, especially north of I-40 due to less cloud cover. 7 sites tied or broke daily records on Saturday. .PREV DISCUSSION /452 AM/... very hot, dangerous, and occasionally record- setting temperatures are expected over the next several days as strong high pressure remains in place. As the center of the high shifts slightly northwestward over the next 48 hours, additional moisture may stream into the Northland. Still, only low-grade monsoon activity is anticipated, and hot conditions will persist. && .AVIATION...For the 18Z package...VFR conditions will prevail over the next 24 hours. Isolated thunderstorms will develop this afternoon, mainly southwest of a KFLG-KSJN line. The primary aviation hazard will be gusty outflow winds to 40 kts. North to northeast surface winds 5-15 kts during the daylight hours. Storm coverage and winds speeds will decrease after sunset. Aviation discussion not updated for amendments. && .FIRE WEATHER...Very hot conditions will continue through Monday. Chances for thunderstorms will slowly increase. Most coverage will remain south of I-40. The primary hazard will be gusty outflow winds. Haines indices remain high, especially over the northern zones. Tuesday through Thursday...Storm chances continue to improve with slowly moderating temperatures. Storm coverage most likely over the Mogollon Rim and White Mountains, spreading westward late in the afternoons and evenings. && .FGZ WATCHES/WARNINGS/ADVISORIES...Excessive Heat Warning until 8 PM MST Wednesday FOR AZZ005-006- 018-037-038. && PUBLIC...DL/KD AVIATION...TPS FIRE WEATHER...TPS For Northern Arizona weather information visit weather.gov/flagstaff
Special Weather Statement
National Weather Service Flagstaff AZ
114 PM MST Sun Aug 16 2020
AZZ017-162045-
White Mountains-
114 PM MST Sun Aug 16 2020
...SIGNIFICANT WEATHER ADVISORY SOUTH OF WHITERIVER UNTIL 145 PM
MST...
At 113 PM MST, Doppler radar was tracking a strong thunderstorm 8
miles south of Seven Mile, or 39 miles south of Show Low, moving
south at 15 mph.
Nickel size hail and winds in excess of 40 mph will be possible with
this storm.
This storm will remain over mainly rural areas of Navajo County.
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 3357 10996 3358 10996 3358 11000 3373 11000
3375 10991 3358 10990 3358 10992 3357 10993
TIME...MOT...LOC 2013Z 345DEG 14KT 3366 10996
TPSThe Flagstaff radar (KFSX), 126 km away, was scanning. The volume nearest the first event began at 21:02 UTC.
2 thunderstorm wind, 1 dust storm. Local standard time, as filed.
Thunderstorm wind gusts blew down tree limbs. Several weather stations in the area recorded wind gusts between 60 and 68 MPH.
A trained spotter reported a dust storm north of Paulden with visibility down to 1.5 miles. The sustained wind was north-northwest at 29 MPH.
A Mesonet weather station at Sunset Point measured a peak wind gust of 61 MPH.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Arizona in 2020Every state in 2020This day in weather historyWarnings in Arizona, August 2020
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: 915207, 915212, 915209.