08/21/2015 Idaho DEQ Smoke Forecast

Updated Noon MDT Friday, August 21, 2015

Valid through: Noon MDT Monday, August 24, 2015

Smoke Outlook

Air quality is currently ranging from Moderate 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 Moderate 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 low pressure trough and associated cold front will serve to generate breezy winds with gusty conditions at the surface across all of Idaho today.  Surface winds will be from the northwest-west across Idaho with south-southwest winds within the Purcell Trench into Boundary County and southwest-west across the Rathdrum Prairie.  Southern Idaho will see northwest winds within the Treasure Valley and west-southwest winds elsewhere.  Surface wind speeds will range from 10-25 mph across all of Idaho with gusts to 40 mph across southeast Idaho.  Expect gusts from 25-35 mph across the rest of Idaho today.  This wind speed will help move smoke out of the area, but also serve to invigorate active fires, potentially leading to increased smoke production.  Mixing heights are expected to be range from 4,000-8,000 ft AGL this afternoon.  Tomorrow and Sunday will see an establishment of an upper level ridge centered directly overhead Idaho on Saturday night.  This will serve to severely hamper wind speeds and vertical mixing.  This is particularly evident over northern Idaho where wind speeds are less than 5 mph with a generally easterly direction.  At that speed, it is important to remember that local terrain will drive wind direction.

The strongest smoke impacts are occurring across the Clearwater drainages, Central Idaho Mountains as well as southeast Idaho.  This will continue into the afternoon and evening.  Expect to experience impacts from the Canada border 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 drainages around 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.  Smoke coverage will begin to improve in southern Idaho tomorrow and into Sunday as the winds shift.  Impacts in the central Idaho region will continue to be quite strong as a high-amplitude ridge develops and limits mixing and wind speeds Saturday night into Sunday.  Regional impacts from fires burning in California are possible beginning Sunday and into Monday in southwest Idaho.

DEQ Air Quality Advisories:

Idaho DEQ has issued a state-wide Forecast and Caution for all counties.  This will be re-evaluated Monday, August 24^th at 2pm MDT.

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.