08/18/14 Idaho DEQ Smoke Forecast

Updated 1000am MDT Monday, August 18, 2014

Valid through Noon MDT Tuesday August 19th, 2014

Smoke Outlook

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

• Idaho County (Off the Nez Perce Reservation) -effective through 10:00am PDT August 18th, 2014, at which time it will be re-evaluated and either extended or lifted.

The areas of concern continue to be in the Clearwater Basin due to the proximity of local fires.  Smoke impacts have been limited to regions close to fires as DEQ's monitors have recorded Green for the 24hr AQI yesterday.  The USFS Emergency Monitor located at the Fenn Ranger Station recorded a 24hr AQI of Moderate.

Today, the upper-level low-pressure system is dropping south and settling over the California-Oregon border, which will put southern Idaho in a southwest-west flow regime.  The cut off low will provide enough instability for afternoon/evening thunderstorms today across the elevated regions. The surface pressure gradient is oriented south to north and is relaxed across southern Idaho.  Surface wind direction looks to be quite variable this afternoon and will likely follow the terrain owing to the weak pressure gradient and related light surface wind speeds of 2-8 mph. With any sort of sustained wind, the direction will likely be from the north-northwest across the Middle and Lower Snake River Plain and west-southwest across the Upper Snake River Plain and Central Idaho Mountains.  Skies are expected to be mostly sunny all day. Mixing heights are forecast to be between 3,000-12,000 feet AGL. Transport wind direction is forecast to be from the south-southwest over southern Idaho at 5-10 mph. Ventilation is forecast to be GOOD across southern Idaho with locally MARGINAL ventilation across the Snake River Plain in the afternoon. Inversions are expected to break late, if at all, between 12noon and 2pm.  This is due to a warm mid-level air mass that is creating a subsidence inversion.  A flat high pressure ridge is over northern Idaho today. The air mass continues to dry out and warm. The drier flow aloft is from the northwest to west today across northern Idaho. 

Smoke impacts today will continue to be strongest across the Clearwater with local impacts in and around the Grangeville area and drainages into the L-C Valley.  Light smoke will also cover southern Idaho and will settle into the drainages this evening.  Smoke is forecast to drain along the valley floors before lifting and turning to the east this afternoon.  All DEQ sites are forecast to be in the Good AQI category today.

The USFS has installed a monitor at the Fenn Ranger Station.  The information can be found at  http://www.wrcc.dri.edu/cgi-bin/smoke.pl

·         Fenn monitor is Smoke#25

·         Users should be aware that the Forest Service site reports the data in Coordinated Universal Time (UTC).  To convert from UTC to Mountain Daylight Time, subtract 6 hours

View DEQ near-real time monitoring at:  http://airquality.deq.idaho.gov/

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.  Refer to the Smoke and Health Tab on the Idaho Smoke Information Blog for additional health information. 

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