Severe storms and a fatal flash flood occurred this past weekend. On Saturday at around 3 pm, 14 people were swept away in a flash flood at a swimming hole near Payson (and 9 were killed). Part of the reason for the flash flood was a recent wildfire upstream from the swimming hole, which made the soil less capable of absorbing rainfall and led to rapid runoff.
Yesterday at the Prescott airport, 1.5” hailstones and 42-knot wind gusts were observed. Quarter-sized hail was also reported in Williamson Valley. The wind at the surface today and tomorrow afternoon will be from the west-southwest at about 10 mph and the winds at 10,000’ above the surface will be from the east-northeast at about 15 mph. This shearing in the winds combined with very moist and unstable air will lead to lines of thunderstorms moving across the Prescott area from the east at about 5-10 mph and capable of producing frequent lightning, heavy rain, hail, and possibly flash flooding. I don’t expect the conditions to be as intense as this past weekend, but we may see more wetting rains and the possibility of flash flooding as the surface dew points are up near 60 degrees F today. There is a flash flood watch in effect through this evening.
By Wednesday, the winds aloft will shift to a south-southeasterly direction and by Thursday some of the lower-level winds will briefly turn around to a north direction. This trend will reduce the wind shear and the moisture to some extent by Thursday. Expect therefore a slight downturn in the strength and likelihood of thunderstorms Wednesday to Thursday, but the daily chance of thunderstorms will continue for at least a week.
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Official National Weather Service forecast
Graphical Weather Forecast for the Prescott Area: