The Phoenix area will swelter under an excessive heat warning through Saturday evening, but those high temperatures are also expected to signal the start of monsoon activity in the state.
It’s not likely the Valley will see any rain this weekend, but storms in other parts of the state — southern Arizona in particular — could have an impact here.
Jaret Rogers, a meteorologist with the National Weather Service in Phoenix, said winds from storms near Tucson might stir up trouble.
Possibility of dust storms
“If we start to see storms form near the Tucson area, that’s usually where we look for possible dust storms moving up along I-10 into Phoenix,” Rogers said. “It shouldn’t be widespread or anything like that, but even a couple of storms could be enough to produce some blowing dust up toward us.”
Drivers, particularly those traveling between Phoenix and Tucson this weekend, should be aware of the possibility of blowing dust.
The Tucson forecast calls for about a slight chance (10%) of storms on Thursday but those chances climb over the weekend to 30% by Sunday.
Meanwhile, the National Weather Service in Flagstaff is also calling for the chance of storms to start Wednesday and increase over the weekend. The Wednesday storms could be dry (lower levels of the atmosphere contain little moisture) but the possibility of rain increases, particularly in the higher elevations.
High pressure, high heat
The reason for the uptick in monsoon activity is the same as the cause of the heatwave. An area of high pressure, called the monsoon ridge at this time of year, is building to the northeast.
Strong high pressure areas result in higher temperatures. During the excessive-heat warning, Phoenix is looking at highs of 113 degrees on Thursday and 112 degrees on Friday and Saturday. Highs are expected to top 110 degrees in Phoenix through Tuesday.
During times of extreme heat the Weather Service and other authorities urge people to take precautions including staying hydrated, limiting outdoor activities during the hottest parts of the day, seeking shelter in air-conditioned spaces, checking on elderly neighbors and making sure to keep kids and pets cool.
More moisture coming
A dust storm moved through the Phoenix area on July 10, 2018, bringing some rain with it.
Rob Schumacher, Arizona Republic
Winds flow in a clockwise manner around high pressure areas and the position of this high should bring in moist air from the south. That moisture is the fuel needed for monsoon storms.
“Usually in the early parts of the monsoon, it seems like we usually get a pretty big heat-up right before we get the moisture,” Rogers said. “That seems to be what’s occurring here too. That high pressure is going to set up over New Mexico for the next few days. That will help draw the moisture northward up into central Arizona.”
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