08/18/2015 Idaho DEQ Smoke Forecast

Updated 1130 am MDT Tuesday, August 18, 2015

Valid through: Noon MDT Wednesday, August 19, 2015

Smoke Outlook

Air quality is currently ranging from Good to Unhealthy across all of Idaho with higher impacts across the Clearwater Basin Drainage, the Treasure Valley, and the Salmon-Challis area.  Air quality is forecast to remain in the Moderate to Unhealthy category for the 24hr standard across central Idaho and Unhealthy for Sensitive Groups across the Treasure Valley.  Impacts are from regional fires burning in Washington State, California, Oregon, and a multitude of local fires in the Clearwater drainage, Central Idaho Mountains, and the Owyhees.

Nez Perce Reservation:  24-hour monitor readings range from Unhealthy for Sensitive Groups to Unhealthy.  Hourly readings are fluctuating from Moderate to Hazardous, depending on location and wind direction.  The Nez Perce Tribe will continue their Air Quality Advisory.  Please contact the Nez Perce Tribe for more information: airquality@nezperce.org.

An upper level dirty ridge over Idaho will provide a consistent northwesterly wind direction both at the surface and aloft.  Surface winds will be from the northwest-west across Idaho with northeast-northwest winds within the Purcell Trench.  Surface wind speeds will range from 10-15 mph in southwest Idaho, 5-10 mph in the southeast, and 2-8 mph in northern Idaho.  Mixing heights are expected to be range from 4,500-7,000 ft AGL this afternoon which should promote vertical mixing.  Expect similar weather patterns and wind regimes for Wednesday.

The strongest smoke impacts are occurring across the Clearwater drainages and southwest Idaho.  This will continue into the afternoon and especially this evening.  Expect to experience impacts from Boundary/Bonner County line south to the Idaho/Nevada and Idaho/Utah border.  The highest impacts are expected to be within the drainages of the Clearwater, Salmon, Lochsa, down into the Lewiston-Clarkston Valley.  In southern Idaho, impacts will be greatest within the Upper Treasure Valley, north to McCall and Garden Valley and east along the Arco Desert within the Snake River Plain and through the drainages into the Salmon and Challis regions.  Expect impacts within the Weiser, Payette, Brownlee, and Boise drainages this afternoon and evening.  Nocturnal drainage flow will contribute to greater impacts in all of Idaho tonight, especially within the drainages into the Snake River Plain off the Central Idaho Mountains.  Consistent smoke coverage is expected across all of Idaho except across the Southeast Highlands, Teton Valley, and the southern extent of the Upper Snake River Plain region into this evening.

Idaho DEQ has issued a Stage 1 Forecast and Caution for the following areas:

·                     Latah, Nez Perce, Lewis, Clearwater, Idaho Counties, river corridors and surrounding areas (off the Nez Perce Reservation) effective  through 10:00am PDT August 19, 2015, at which time it will be re-evaluated and either extended or lifted.

·                     Ada, Canyon, Gem, Owyhee, Payette, Valley, Adams and Washington Counties effective through 3:00pm MDT August 19, 2015, at which time it will be re-evaluated and either extended or lifted.

·                     Cassia, Gooding, Jerome, Lincoln, Minidoka, and Twin Falls Counties effective through noon MDT August 19, at which time it will be re-evaluated and either extended or lifted.

·                     Lemhi and Custer Counties effective through 12:00pm MDT August 19, 2015, at which time it will be re-evaluated and either extended or lifted.

·                     Boundary, Bonner, Kootenai, Shoshone, and Benewah Counties effective 12:00pm PDT August 20, 2015, at which time it will be re-evaluated and either extended or lifted.

Smoke forecasts are dependent on predicted fire growth and weather.  If conditions change unexpectedly, impacts could occur.  When visibility starts to go below 5 miles, sensitive groups should minimize outdoor activities.  Everyone else should minimize prolonged or physical activity outdoors.  Visit the Idaho Smoke Blog for more information at http://idsmoke.blogspot.com/

Your eyes are your best tools to determine if it’s safe to be outside.  Even if you smell smoke, the air quality may still be good. 

AQI Category	Visibility (miles)
Good	11+
Moderate	6-10
Unhealthy for Sensitive Groups	3-5
Unhealthy	1½  -2¾
Very Unhealthy	1-1¼
Hazardous	Less than 1

How to estimate air quality based on visibility for areas without an air quality monitor or airport visibility estimate:

a. Face away from the sun.

b. Determine the limit of your visible range by looking for targets at known distances (miles).

c. Visible range is when an object you can easily see in the distance disappears.

d. Use the visibility values above to determine the local wildfire smoke category.