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Monsoon Rains & Thunderstorms to Continue Through Weekend

09 July 2018   Dr. Curtis James
Expect monsoon activity this week!

Forecast Discussion:

Over the weekend, rainfall totals across the Prescott area ranged from about 0.20” to 1.30”. It’s great to receive much needed moisture!

The good news is that the monsoon moisture will remain in place for this entire week as the high pressure dome aloft is expected to remain to our north or northwest and circulate easterly or east-northeasterly wind across Arizona. Today there is an approaching disturbance from the east that will bring cooler air aloft to help destabilize the atmosphere as well as provide lifting and additional wind shear, enhancing the potential for thunderstorms this afternoon through tonight. The mid-level winds are east-northeasterly at 20-30 knots, which will produce enough shearing over the low-level southerly or southwesterly flow to help organize lines of thunderstorms. Some of the storms will be strong or possibly even severe, especially as they descend into the lower deserts in the evening hours. The main threats will be strong gusty wind and microbursts, locally heavy rainfall, and small to moderate hail (up to 0.5” diameter). The storms will propagate toward the west-southwest at about 15 mph. The Storm Prediction Center has indicated a marginal possibility of severe thunderstorms today (, which is not a common occurrence during the monsoon.

By tomorrow, the flow aloft will weaken and the thunderstorms will become less organized for the rest of the week and into the weekend. The vertical wind shear will not be conducive to forming lines of storms or multicell thunderstorms, but rather, we will see airmass thunderstorms scattered across northern Arizona each day through the weekend. The direction of thunderstorm motion will vary throughout the week and will generally be at speeds of 5 mph or less. This could lead to locally heavy rainfall from slow-moving storms in some areas. There looks to be some slight drying in the lower atmosphere on Friday and Saturday, but not enough to reduce the probability of thunderstorms significantly.

C. James

Met Mail is an unofficial weather discussion and forecast transmitted once or twice a week via e-mail by the Embry-Riddle Department of Meteorology ( Embry-Riddle offers an undergraduate bachelor-of-science degree program in Applied Meteorology. Please spread the word to all potential qualified candidates!

Further Information:

ERAU Applied Meteorology degree program

Official National Weather Service forecast

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