Upper-Low targets Arizona: Potential for thunderstorms, severe weather, rain, and snowfall

According to the Arizona Weatherman, the models are now converging on the solution for the likely upper-level low to develop over Arizona next weekend, Friday, October 18, 2024, through Sunday, October 20, 2024. As this pending pattern develops, it will be a stark break from the pervasive high pressure and record-breaking temperatures the state has experienced over the past several weeks. This upper-level low will bring relief from the heat and drop the temperatures significantly. Secondly, rainshower and thunderstorms will accompany this system with potential severe weather as well. Lastly, snow is on the table with this system in the higher elevations in the mountains of northern Arizona.

300 mb low center over Arizona on 19 Oct Saturday 2024.Photo byWindy.com

The models are still in slight disagreement about how far south this low will push over Arizona, but in any case, the majority of the precipitation will be over Northern Arizona. In particular, Flagstaff is looking like ground zero, as is the Mogollon Rim triangle of Flagstaff, Payson, and Prescott. Also, northeast Arizona has a higher possibility of precipitation. The most likely precipitation for the state will be rain showers and thunderstorms, but higher elevations above 7,000 feet could get snow in the San Francisco range and northern Grand Canyon.

Model accumulated precip Friday to Sunday 18-20 Oct 2024.Photo byWindy.com

Less precipitation is expected for Central and Southern Arizona. However, due to its location and movement, Phoenix has a better chance than Tucson for this system to get rain and thunderstorms. The models are mixed in terms of how much precipitation each location will get due to the convective nature of this system. The 500 mb vorticity looks particularly impressive Saturday through Sunday, so expect the potential for severe weather. It is possible for convective gusts above 50 mph, 1-inch hail, and localized flooding. This will be on top of the already higher gradient level winds associated with the system. Also, this low will bring a significant reduction in temperatures throughout the state. This will be our real first impression of fall in Arizona. This will be even more pronounced for Northern Arizona than Southern Arizona, but one likely greeted favorably by most.

This is the initial long-range forecast for this system. As more details become evident, the Arizona Weatherman will provide more detailed articles on this upcoming low system. Also, this upcoming Monday and Tuesday, a weak pre-low pressure center will move over northern Arizona and likely produce some weak rain showers, but this will be nothing compared to next weekend's event.

Source: The Arizona Weatherman, a seasoned meteorologist with over 25 years of experience in aviation meteorology with the United States Air Force, government contracting, and private practice, provides this forecast. His experience training Special Operations Weather Technicians (SOWT) in weather techniques and his state certification as a STEM teacher further underscore his expertise. His weather predictions are trustworthy.

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