Dust Risk-Based Forecast | Pinal County

Friday

Stagnation: Light stagnation

Wind: Light becoming East to southeast 5-15 mph, gusts 20-25 mph, diminishing late

Saturday

Stagnation: No stagnation

Wind: East to southeast 5-15 mph, gusts 20-25 mph becoming south to southwest in the afternoon, diminishing late

Sunday

Stagnation: No stagnation

Wind: Light becoming west to northwest 5-10 mph

Monday

Stagnation: Light stagnation

Wind: Light becoming west to northwest 5-10 mph

Tuesday

Stagnation: Light stagnation

Wind: Light becoming northeast 5-12 mph

Forecast Discussion:

High pressure is in control of the area today as evidenced by the early morning temperature inversion, light winds and clear skies. Unfortunately the inversion and light winds haven't helped the Hidden Valley area as once again the PM10 levels are spiking in that area. Several of the 5-minute PM10 averages at Hidden Valley have surpassed 1,500 ug/m3! The latest couple of hourly averages (8 & 9 a.m.) were 914 ug/m3 and 505 ug/m3 and so today's daily PM10 average at Hidden Valley is going to approach and perhaps exceed the health standard. The high pressure will move off to the east early Friday and the approaching Pacific low pressure system will cause a tight pressure gradient which will result in breezy to gusty easterly winds (25-35 mph gusts!) over the higher elevations of eastern Pinal County. Some blowing dust is expected for central locations (San Tan Valley, Florence, Coolidge, Eloy, etc.) and is reflected in the PM10 forecasts. The big question at this point, how far westward will those winds make it? Looking at the University of Arizona forecast model runs they are expected to reach central portions of the County by mid-morning on Friday, though the winds will be slightly weaker (10-15 mph sustained winds, gusts 20-25 mph). Unfortunately it doesn't look like the stronger winds will make it out west far enough to help disburse the particulates at Hidden Valley. The insult to injury will be the easterly component to the early morning winds and their expected effect on the PM10 levels at Hidden Valley (PM10 exceedance forecasted - high dust risk).
There is good air quality news on the horizon though, the approaching low pressure system will bring rain chances for late Friday and more widespread rain during overnight Friday into Saturday timeframe. Much of the area is forecast to receive at least a quarter of an inch of rain with higher amounts of half an inch to perhaps three quarters of an inch in some places (eastern mountains). There's even slight thunderstorm chances for Saturday. Have low dust risks forecasted for Saturday through next Tuesday due to the rain.


- S.DiBiase
Pinal County Air Quality Meteorologist