08/15/14 Idaho DEQ Smoke Forecast

Updated 1030am MDT Friday, August 15, 2014

Valid through Noon MDT Monday, August 18, 2014

Smoke Outlook

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

• Latah, Nez Perce, Idaho, Lewis, and Clearwater Counties (Off the Nez Perce Reservation)-effective  through 10:00am PDT August 15, 2014, at which time is 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, there is some transport of smoke from fires burning in California, Oregon, and Washington.  Smoke impacts were limited to regions close to fires as DEQ’s monitors and the Kootenai Tribe monitor in Bonner’s Ferry were Green for the 24hr AQI.  The USFS Emergency Monitor located at the Fenn Ranger Station recorded a 24hr AQI of Very Unhealthy with hourly values in the Very Unhealthy and Hazardous. 

Today, the upper level low pressure system located over Washington will fill and become an open wave as it moves to the northeast.  This will lead to a zonal wind pattern with a slight southerly component for southern Idaho.  There is a dry slot over Eastern Idaho and an incoming dry slot moving into southwest Idaho.  This is promoting warm air aloft and limiting mixing.  The monsoon moisture is has pushed east out of Idaho; however, the marginal instability associated with this upper level shortwave has the potential to fire off isolated thunderstorms in the Eastern Highlands.  We will continue to see moist and unstable air move into northern Idaho today. The flow aloft is from remains the south. The scattered showers and thunderstorms will continue this afternoon over northern Idaho accompanied by strong and gusty wind with locally heavy rain.  At the surface this afternoon a relaxed pressure gradient field is oriented west to east yielding generally a southwest to northwest surface wind direction. Surface wind speeds will be generally less than 10 mph, except for gusts to 30 mph near any thunderstorm.  Mixing heights this afternoon are expected to be quite low again due to the nearly saturated air mass over northern Idaho are will likely range from around 2-3,000 feet AGL over all air sheds with model soundings again being saturated above that level in the north with mixing heights from 3-7,000 feet AGL over southern Idaho. Transport winds are southwest to northwest over all air sheds. Transport wind speeds will be in the 5-10 mph range. Smoke dispersion is expected to be poor.

This weekend, weak upper level ridging will promote warm and dry conditions over the state as the current upper level wave passes into Montana by Saturday.  On Sunday, a cut-off low retrogrades over California and keeps Idaho under southwest flow through the mixed layer.  At the surface Monday a thermal ridge is moving into eastern Washington and northern Idaho. The surface pressure gradient field is relaxed and oriented west to east. Surface wind direction looks to be from the southwest to northwest over the air sheds. Surface wind speeds are light and generally less than 10 mph. Mixing heights by Monday afternoon are expected to range from 4-7,000 feet AGL. Transport winds look to be from the southwest to northwest at 5-10 mph producing marginal to good dispersion. Surface wind direction looks to be quite variable on Monday and likely follow the terrain, owing to the weak pressure gradient and related light surface wind speeds of 2-8 mph.  Skies are expected to be mostly sunny all day.  Mixing heights are forecast to be between 5,000-9,000 feet AGL. Transport wind direction is forecast to be from the south-southwest over southern Idaho at 5-10 mph. 

Smoke impacts today will continue to be strongest across the Clearwater with locally heavy impacts in and around the Grangeville area, north into the L-C Valley and into the Idaho Panhandle due to the proximity of the Big Cougar, High Range, and Johnson Bar fires.  Light smoke will also cover southern Idaho from the southwest corner of the start to Salmon via transport from fires burning in California.  Smoke will settle into the drainages again this evening.  This weekend will bring light smoke through the Snake River Plain.  The 24hr AQI forecasts for the Grangeville, Coeur d’Alene, Pinehurst and St. Maries areas are in the Moderate category for Today.  Higher values should be expected in the morning before the inversion breaks with similar conditions this weekend.

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