PHOENIX -- High pollution advisories have been issued for Thursday across Pinal and Maricopa counties, including the Phoenix-metro area.
Elevated levels of PM-10, better known as dust, plus ozone, are expected during this time.
The driving force behind the dust will be thunderstorms that will develop across southeastern Arizona Thursday during the afternoon and nighttime hours. It will be hard for those thunderstorms to produce any measurable rain.
Plus, they can create outflow boundaries that basically act as mini cold fronts. Outflow boundaries can kick up strong winds, which could potentially create hazardous dust storms in the Valley and in typical dust-prone areas, like the I-10 corridor between Phoenix and Tucson.
Wednesday afternoon, storms firing up in the high country were expected to stay north and east of the Valley, but they’re traveling in a southwesterly direction, so an outflow boundary with dust could not be ruled out in the East Valley through the evening hours of Wednesday.
Looking ahead to the Fourth of July, monsoon moisture will increase from the southeast into Arizona. With high instability in the atmosphere, combined with daytime heating, thunderstorms with rain could move into the Valley during the afternoon and evening hours.
With higher humidity, temperatures are expected to drop from Wednesday’s 110 range to the 105 range in the Valley.