08/24/2015 Idaho DEQ Smoke Forecast

Updated Noon MDT Monday, August 24, 2015

Valid through: Noon MDT Wednesday, August 26, 2015

Smoke Outlook

Air quality is currently ranging from Moderate to Hazardous 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 Very Unhealthy to Hazardous.  Hourly readings are fluctuating from Unhealthy 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 ridge of high pressure has become established over Idaho with the ridge axis over central Montana.  This will serve to severely hamper wind speeds and vertical mixing with surface wind speeds from 5-10 mph and 8-12 mph across northern Idaho.  Mixing heights will range from 2,500-8,000 ft AGL this afternoon with higher heights over the Central Idaho Mountains.  At that speed, it is important to remember that local terrain will drive wind direction.  While some moisture is embedded within this ridge pattern, it is not expected to generate much in the way of unsettled weather.  This pattern is expected to persist through the week as a low pressure trough approaches Idaho.

The strongest smoke impacts are occurring across the Clearwater drainages, Central Idaho Mountains as well as southwest 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 generally north of a line running from Weiser to Salmon.  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.  Dispersion models are currently depicting little influence in southern Idaho, but this is not evident based on recent observations.  High level smoke is expected from California fires as the southwesterly flow pattern continues to drive the weather over Idaho.  Impacts in the central Idaho region will continue to be quite strong as the ridge limits mixing and wind speeds into Thursday and Friday.  No major weather changes are expected until the end of this week with increasingly unsettled weather with the chance for afternoon thunderstorms.

DEQ Air Quality Advisories:

Idaho DEQ has issued a state-wide Forecast and Caution for all counties.  This will be re-evaluated Tuesday, August 25^th at 3pm 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.