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Winter Air Quality Update & Forecast
Tuesday, February 12, 2019 9:14 AM

Locations and Air Quality Conditions

Current Situation Forecast

Tuesday AM Update:
While air quality has improved in most western valleys over the past 24 hours, the Helena Valley remains stuck under a strong inversion. Air quality in Helena as of Tuesday morning is currently UNHEALTHY. The inversion in Helena is still quite strong, with temperatures in the valley at 4 degrees, while the top of Mt. Helena is currently 27 degrees.

Monday AM:
Air quality is MODERATE in many western valleys Monday morning due to lingering cold pools. It is currently below zero or in the single digits in most valleys, while ridge tops and mountain passes are in the teens. This has caused pollution to remain trapped in the valleys, with MODERATE air quality in Libby, Seeley Lake, Frenchtown, Missoula, Helena, and Butte.
Tuesday Update:
Air quality in most western valleys is expected to be good today with warmer temperatures and breezy southwest winds. The Helena Valley is the big question. The inversion should erode throughout the day, hopefully bringing warmer air and good air quality to the valley by the afternoon. However, it is possible the inversion will remain in place until Wednesday when the next weather system moves in. The warmer air and breezy winds aloft will be working to erode the inversion throughout the day, when/if they are able to break through, temperatures will increase rapidly and air quality should improve.

Original Post:

The good news is that warmer air is starting to move into the area, as evidence by the warmer air aloft causing the cool pools in the valleys. A push of moisture from the Pacific Northwest will bring warmer air over the next 24 hours to most of western Montana. Most valleys should be able to break out from under the inversions later this morning or early afternoon, seeing temperatures reach the teens or maybe even 20s by late afternoon. Air quality should improve in most locations at the same time, although some stubborn valleys may remain stuck under an inversion into tonight. Right now, the Helena Valley inversion is quite strong and will likely take the longest to clear. The improved dynamics will bring another round of snow to the area. Widespread snow is expected in northwest Montana Monday, spreading to the south and east throughout the day. Most areas should see fresh snowfall by Tuesday morning, with snow showers persisting throughout the day on Tuesday for many locations. Throughout the day Tuesday, air quality should be good in most locations with breezy southwest winds. Temperatures are expected to be in the 20s (and maybe above freezing!) for a brief period on Tuesday.

On Wednesday, another arctic cold front will bring plummeting temperatures and more snow to most locations by Thursday morning. The fresh snowfall and cold air will likely cause another round of moderate air quality on Friday and Saturday morning before yet another storm moves in for the weekend.

Overall, this active weather pattern will inhibit the formation of strong inversions and keep air quality generally good, with only brief periods of moderate air quality in between storms.

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

Tuesday update: A shallow inversion is present over the Helena Valley this morning.  

Tuesday update: A shallow inversion is present over the Helena Valley this morning.
Source: Carroll College

Good dispersion is expected in most areas today.

Good dispersion is expected in most areas today.
Source: University of Washington

Winds are expected to be breezy in many locations today.

Winds are expected to be breezy in many locations today.

Source: Weather Underground 

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  Helena
  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