An upper air disturbance moving eastward across northern Arizona and southern Utah|helped trigger strong thunderstorms over central Arizona.
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The episode as NWS FGZ wrote it up.
An upper air disturbance moving eastward across northern Arizona and southern Utah|helped trigger strong thunderstorms over central Arizona.
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 5, 10:02 AM MST, 50 minutes earlier.
Area Forecast Discussion National Weather Service Flagstaff AZ 1002 AM MST Sat Aug 5 2017 .SYNOPSIS...Scattered showers and thunderstorms are expected cross northern Arizona again today. A drier and more stable airmass is expected to move into the region Sunday and into early next week. This will result in much less storm coverage across northern Arizona. && .DISCUSSION...Morning water vapor imagery reveals significant dry air streaming westward across the Southwest US. This was evident on the 12z RAOB from Bellemont with much drier air above 500 mb compared to yesterdays sounding. There also was a cap just above 500 mb which will be another hindrance to widespread storm development today. However, residual low level moisture from the Mogollon Rim northward will lead to isolated to scattered storm development later this morning and into the afternoon. South of the rim, storm initiation will be difficult with even drier air over that region. The dry air will take more of a hold on the area Sunday and into next week with minimal shower and thunderstorm activity each afternoon. Isolated storm development will be favored north of the rim during this timeframe. && .PREV DISCUSSION /330 AM MST/...An upper air disturbance is moving eastward across northern Arizona and southern Utah this morning. This has allowed showers and thunderstorms to continue over night across central Arizona and along the AZ/UT border. Some storms have reformed over the same area leading to a few flooding issues. Storm activity this morning will continue to move east through the morning with other storms developing through mid-day. Drier and more stable air may move in from the west this afternoon with decreasing activity from west to east. Southwest flow aloft will bring drier air into the coming week. While the decreasing moisture will likely limit the amount of storms developing over the area, some isolated showers will still be possible during the afternoon hours. Models are indicating the potential for returning moisture by late next week, and we will watch for this in the coming days. && .AVIATION...For the 18Z package...Scattered SHRA persisting this morning north of KFLG where local MVFR possible. Thunderstorms will redevelop this afternoon...primarily north of a line from KPRC - KPAN. The strongest storm cells will produce IFR conditions and typical gusty winds. Storm activity will decrease aft 03Z Sunday, with only isolated showers overnight. Aviation discussion not updated for TAF amendments. && .FIRE WEATHER...Expect scattered thunderstorm activity this afternoon, generally along and north of the Mogollon Rim. The strongest storms may produce locally heavy rain and gusty winds. Drier conditions are expected on Sunday, with only isolated storms across the higher terrain. Monday through Wednesday...Dry weather will continue...with only isolated showers and thunderstorms expected over far northern and eastern Arizona through the period. && .FGZ WATCHES/WARNINGS/ADVISORIES...NONE. && PUBLIC...TPS/MAS AVIATION...MCT FIRE WEATHER...BAK For Northern Arizona weather information visit weather.gov/flagstaff
Hazardous Weather Outlook National Weather Service Flagstaff AZ 513 AM MST Sat Aug 5 2017 AZZ004>018-037>040-060400- 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- 513 AM MST Sat Aug 5 2017 This hazardous weather outlook is for Apache...Coconino... Northern Gila...Navajo...and Yavapai Counties in Northern Arizona. .DAY ONE...Today and Tonight Showers and thunderstorms will continue to move east to northeast today as a weather disturbance moves east across far northern Arizona. .DAYS TWO THROUGH SEVEN...Sunday through Friday Moisture begins to decrease across the area limiting storms to a more isolated pattern through the weekend and into early next week. .SPOTTER INFORMATION STATEMENT... Weather spotters are encouraged to report significant weather conditions according to standard operating procedures.
The Flagstaff radar (KFSX), 109 km away, was scanning. The volume nearest the first event began at 17:50 UTC.
1 funnel cloud. Local standard time, as filed.
At 10:52 AM MST, the Prescott Airport reported a funnel cloud three miles northeast of the tower moving northeast. At 11:25 AM MST, they reported that the cell was weakening with just a moderate intensity rain shaft. The duration of the funnel cloud was 15 minutes.
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: 720457.