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Winter Air Quality Update & Forecast
Monday, January 14, 2019 12:12 PM

Locations and Air Quality Conditions

Current Situation Forecast
We are seeing MODERATE air quality in Butte, Helena, and Seeley Lake due to strong inversions in place Monday morning. In Butte, hourly air quality briefly reached UNHEALTHY levels overnight as temperatures dipped below 0. Elsewhere, air quality conditions are better, with GOOD air quality in the rest of western Montana despite inversions present in many valleys. The ridge of high pressure responsible for the cold overnight temperatures and moderate to unhealthy air quality will continue to impact the state through Tuesday. We can expect worsening air quality again Tuesday morning in many valleys, although Helena and Butte are getting hit hardest. Air quality is expected to reach MODERATE to UNHEALTHY FOR SENSITIVE GROUPS in many western valleys overnight Monday into Tuesday. The light surface winds will become easterly on Tuesday, likely helping to keep pollution in place for the day. We should start to see improvement beginning Tuesday night, as the ridge starts to break down and a number of disturbances start to move through the area.

The first of these disturbances, moving through on Tuesday night, will cause winds to increase at higher elevations and become southwesterly. Some light snow showers are possible. We will likely see improvement in many valleys on Wednesday, but some of the more stubborn inversions may hang around into Wednesday.

The next disturbance, expected to move through on Thursday will be stronger, with a more widespread chance of snow showers and increasing winds aloft. These winds should eventually break down to the valley floor in any area still struggling under an inversion on Thursday. A ridge of high pressure looks to be moving in for the weekend, bringing another round of overnight inversions and clear skies. This ridge is not forecasted to last as long as this current one, with more active weather expected at the start of next week.

Air Quality Bureau
Montana Department of Environmental Quality
Phone: (406) 444-3490

Low clouds in the Bitterroot Valley today.  

Low clouds in the Bitterroot Valley today.
Source: USFS

The light winds are expected to continue today for western Montana valleys.

The light winds are expected to continue today for western Montana valleys.
Source: Weather Underground

Dispersion is expected to remain poor on Tuesday.

Dispersion is expected to remain poor on Tuesday.

Source: University of Washington  

Real time particulate information is currently available in most of the larger urban areas from MTDEQ's Today's Air website.

Today's particulate report below compares particulate levels received from DEQ's
reporting stations with MTDEQ’s Health Effect Categories.

Locations and severity of PM 2.5 particulate values over the past 24 hours from the time above.
Health Effects Categories City
  Very Unhealthy  
  Unhealthy for Sensitive Groups  



 All other reporting locations. 

B1(x) One-hour BAM value (number of values)
B8(x) Eight-hour average BAM
B24 24 hour  average BAM value