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Winter Air Quality Update & Forecast
Tuesday, January 2, 2018 12:30 PM

Locations and Air Quality Conditions


Current Situation Forecast
The ridge of high pressure is continuing to cause very stable conditions allowing very strong inversions to continue throughout the western valleys. The ridge starts to break down on Friday afternoon with the passage of a cold front, bringing better dispersion and a chance to break some of the stubborn inversions.

Currently, Helena is reporting UNHEALTHY FOR SENSITIVE GROUPS air quality while Libby, Frenchtown, Hamilton, Butte and Bozeman are reporting MODERATE air quality. All other locations are reporting GOOD air quality.
Air Quality and Dispersion Discussion for January 2 - 5, 2018

A high pressure ridge is situated to the west of Montana, creating a very stable atmosphere and thus preventing mixing down to the surface. Tuesday January 2, is bitterly cold across western Montana, especially in the west-central and southwestern valleys were cold air inversions are strong. The ridge of high pressure will remain firmly in place through the Northern Rockies through the week and as a result, warmer temperatures will slowly move back into western Montana over the next few days. It will likely take until Friday January 5 before the warm air moves into the entire region. Strong valley inversions will be very slow to break and air quality will likely be MODERATE to UNHEALTHY FOR SENSITIVE GROUPS as built up pollution gets trapped under the valley inversions. There is a small chance for a passing snow shower on Wednesday January 3, as a weak disturbance moves through the ridge. It won't be until Friday/Saturday that a stronger disturbance moves into the region from west to east, helping to break down the ridge.

Surface winds during this period will be calm (5 mph) and out of the south to southwest across much of western Montana. Some locations will have still, calm conditions, which coupled with very cold air, will make for very poor dispersion. Air quality will be MODERATE to UNHEALTHY FOR SENSITIVE GROUPS in many western locations throughout Friday, January 5.

Air Quality Bureau
Montana Department of Environmental Quality
Phone: (406) 444-3490
Email: DEQMTSmoke@mt.gov




Pollution lingering in Helena on January 2: 

Pollution lingering in Helena on January 2:
DEQ

 
Light winds Wednesday afternoon, January 3, throughout western Montana:

Light winds Wednesday afternoon, January 3, throughout western Montana:
NWS

Dispersion through Friday, January 5 will be very poor to poor throughout western Montana. This image shows dispersion on Wednesday afternoon, January 3:

Dispersion through Friday, January 5 will be very poor to poor throughout western Montana. This image shows dispersion on Wednesday afternoon, January 3:

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
  Hazardous  
  Very Unhealthy  
  Unhealthy  
  Unhealthy for Sensitive Groups  Helena
  Moderate

 Libby
Frenchtown
Hamilton
Butte
Bozeman
 

  Good

  

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