Sunday, July 20, 2014

Air Quality Forecast, Issued 12 Noon Sunday 20 July 2014

The Carlton Complex wildfire has grown to over 200,000 acres and is wreaking havoc with communications and travel in and around the Methow Valley, especially in Pateros and Brewster where hundreds of buildings have been destroyed.  The air quality at locations close to the fires is surprisingly good--the worst air quality is confined to the northeast portions of Washington where this morning it is Unhealthy in Spokane and Colville.

Breezy conditions will continue during the day and into Sunday night pushing the smoke southeast towards Moses Lake before curving northeasterly towards Spokane and the northern Idaho Panhandle.  Smoke concentrations in the central basin could reach the Unhealthy for Sensitive Groups (USG) Sunday night.  Winds decrease Monday morning and smoke concentration is expected to increase in the central basin and is likely to be borderline between USG and Unhealthy by mid-day Monday as the wind direction begins a shift from northwesterly to southerly.

By Monday afternoon the winds in the vicinity of the Washington fires will southerly and carry smoke northward along the east slopes of the Cascades in response to the approaching system moving down the British Columbia coast.  However, that system's influence will extend south into Oregon raising the possibility that smoke from the wildfires in Oregon will begin to reach Washington.  There is a slight possibility that smoke will reach southeastern Washington Monday afternoon and evening but is not likely to exceed the Moderate air quality level.

Winds are expected to decrease late Monday into Tuesday morning increasing the likelihood of higher smoke concentrations in areas north of the fires.  The level will be dependent on the fire activity--higher fire activity results in greater plume heights and lower concentrations at the surface, lower fire intensity is associated with lower plume heights and increased smouldering to produce higher concentrations at ground level.

Looking ahead into mid-week:  The southerly winds will continue and will likely bring smoke from the Oregon fires into Eastern Washington possibly as far west as Yakima but more likely only as far west as the Tri-Cities and could blanket most of the Columbia Basin with Moderate to occasionally USG air quality.  There is also the possibility that the system moving through on Wednesday will drop one-tenth to one-quarter inch of precipitation in the higher elevations.  Unfortunately, precipitation at this time of year often comes in the form of thundershowers and carries the possibility of additional fire starts from lightning.  That slight amount of precipitation will not be sufficient to extinguish the fires and will only decrease their intensity and raise the possibility of higher concentrations at the surface.

Barring any new fires air quality in areas of Washington not mentioned is expected to remain good.

Clint Bowman
Atmospheric Scientist
Washington State Department of Ecology
P.O Box 47600, Olympia, WA 98504-7600
Tel: 360-407-6807
Fax: 360-407-7534

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