Maricopa County Forecast
Risk Scale
Air Quality Dust RiskISSUED ON: Wed. Sep 20, 2017
This report is updated Monday through Friday and is valid for Maricopa County, Arizona
Thursday 9/21/2017

HIGH
Winds:Light winds early, becoming gusty southwesterly winds 20-30+ mph for the the afternoon.
Stagnation:Morning
Friday 9/22/2017

MODERATE
Winds:Light winds early, becoming west-northwesterly 10-15 mph for the the afternoon.
Stagnation:Morning and Overnight
Saturday 9/23/2017

LOW
Winds:Light winds early, becoming west-northwesterly 5-15 mph for the the afternoon.
Stagnation:Morning and Overnight
Sunday 9/24/2017

LOW
Winds:Mainly light winds.
Stagnation:Possible All Day
Monday 9/25/2017

LOW
Winds:Mainly light winds.
Stagnation:Possible All Day


Synopsis & Discussion
Forecaster: -J. Malloy
Forecasted weather and air quality for today is on track: Seasonable temps, mostly sunny skies, afternoon breezes, and upper Good to lower Moderate AQIs for particulates. Eyes are on that Pacific trough over the Northwest U.S. and how it will evolve over the next 48 hours, which is projected with a high degree of confidence to occupy the entire western U.S. and swing southward into Arizona tomorrow through Friday.

Significance of the weather system and its cold front is going to come in the form of widespread gusty winds (20 to 30+ mph) and blowing dust potential for desert locales. Little to no recent rainfall has fallen over central parts of the state for a while. Southern California would be in the same boat. Thinking a combination of both long-range dust transport from the Lower Colorado River Valley and local dust generation off nature sources near Phoenix is plausible Thursday; enough so to warrant a PM-10 Health Watch issuance for the Phoenix area. Therefore, the dust risk for Thursday has now been raised to High.

After the dry cold frontal passage, winds near the surface on Friday back down, though a haze could linger for the first part of the day elevating particulates; however, the dust risk fall to Moderate then Low by Saturday.
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1110 W.Washington Street
Phoenix, AZ 85007
P: 602.771.2300
azdeq.gov