A weak trough just off the West Coast will combined with a high pressure circulation over southeast Arizona increase the pressure gradient and moisture over northern Arizona. A thunderstorm combined with the gradient wind to produce high wind gusts in Winslow.
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The episode as NWS FGZ wrote it up.
A weak trough just off the West Coast will combined with a high pressure circulation over southeast Arizona increase the pressure gradient and moisture over northern Arizona. A thunderstorm combined with the gradient wind to produce high wind gusts in Winslow.
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 May 9, 2:31 PM MST, 3 hours 24 minutes earlier.
Area Forecast Discussion National Weather Service Flagstaff AZ 231 PM MST Sat May 9 2020 .SYNOPSIS...Chances for showers and thunderstorms will continue across northern Arizona into Monday evening. Drier conditions are expected again by Tuesday through the work week. && .DISCUSSION...A few light rain or virga showers have developed over northern Arizona this afternoon and are moving to the southeast. This activity will end this evening. Moisture will continue to move northward from Mexico on Sunday leading to more shower and thunderstorm activity. With deeper moisture in place, any storms that do for could produce light to moderate rainfall amounts. Some storms could also produce strong gusty winds as well. High temperatures will be close to average on Sunday. A large area of low pressure off the West Coast will bring a much drier southwest flow over Arizona on Monday. Enough moisture will still remain over Apache County on Monday for a few storms there. From Tuesday onward...A dry southwest flow will continue. Look for near normal temperatures with gusty southwest winds each afternoon, strongest on Tuesday and Wednesday. && .AVIATION...For the 00Z package...Expect VFR conditions to dominate throughout the TAF period. Isolated showers and thunderstorms will continue to develop, mainly over higher terrain through sunset this evening. Some of the stronger storms may produce MVFR conditions and erratic wind gusts to 45kts. Outside of storms, expect southwest winds from 10-15 kts. After sunset winds will decrease to light and variable overnight. Gusty winds and convection will return around 18z Sunday. Aviation discussion not updated for TAF amendments. && .FIRE WEATHER....For Sunday, expect warm temperatures with afternoon humidity in 20 to 30 percent. This will allow for gusty winds and scattered thunderstorm development in the afternoon and evening hours, mainly over the higher terrain. These storms are likely to be high based with little rainfall making it to the surface. The primary hazards from this weekend's storms will be strong outflow winds and new fire starts from dry lightning. A downturn in storm activity is expected on Monday, primarily east of Flagstaff. Monday through Wednesday... Tuesday onward is expected to be dry with near average temperatures. && .FGZ WATCHES/WARNINGS/ADVISORIES...NONE. && PUBLIC...MAS AVIATION...Suk FIRE WEATHER...Suk For Northern Arizona weather information visit weather.gov/flagstaff
The Flagstaff radar (KFSX), 67 km away, was scanning. The volume nearest the first event began at 00:54 UTC.
1 thunderstorm wind. Local standard time, as filed.
A wind gust of 60 MPH was recorded at the Winslow Airport at 555 PM.
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, May 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: 883565.