Saturday, September 13, 2014 - Meadow Fire Yosemite NP

Smoke Impact Report – Meadow Wildfire, Yosemite NP, Saturday September 13, 2014

Prepared by Mike Beasley (ARA Trainee) & Gary Curcio

Weather and Smoke Dispersion Outlook: High Pressure continues to provide slightly warmer seasonal temperatures and drier air. This is coupled with instability, Haines Index 6, and increasing wind speeds. These conditions create opportunities for fire growth and smoke production. It also helps to disperse smoke. The Merced River Canyon is the major outlet for smoke moving as far west as Lake Don Pedro. This smoke continues to lift out during the day starting its up-slope, up-drainage flow by 11 am. This produces haze through the Sierra foothills in the afternoon and more concentrated smoke and haze in Yosemite Valley and surrounding canyons.

Figure.1 View from Sentinel Dome 7:00 am September 12th

Figure. 2 View from Sentinel Dome 7:00 am September 13th. 

Fire Operations:  Yesterday, September 12^th, estimated fire growth was about 96 acres which included last night’s burnout operation.  This slight increase reflects good suppression progress and decreasing smoke.  However, weather conditions are changing and can reverse this trend. Fuel is sparse at the high elevations and there are still enough area of isolated and intense heat for torching and spotting. The eastern side of the fire is still a concern for torching and spotting beyond the perimeter providing a means for fire growth and increased smoke production.

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Current Smoke Impacts: Yosemite Valley is now moderate for 3 and 24 hr. averages. El Portal, and Greely Hill were in the Moderate AQI range and now have moved to Good reflecting improving conditions. Tuolumne Meadows had data gaps and is projected to be Moderate for the 24 hr. average.

Forecast and Likely Smoke Impacts: Seasonal warmness, dry weather, instability, and increasing winds still can contribute to increasing fire behavior. It is optimistic that smoke impacts will continue to trend down with fire growth being checked by natural barriers and suppression actions.  Degraded air quality will be confined locally in Yosemite Valley and Merced River Canyon as well as on the east side of the Sierra in the Tuolumne River Canyon and other foothill locations. Please review the table below to review the current and projected impacts.

Table 1. Daily averages, current conditions, and our best estimation for conditions at the best and worst time of day for the next 24 hrs.  For more detail on the Air Quality Index, go to http://airnow.gov/index.cfm?action=aqbasics.aqi. For a map of the monitoring sites, go to: http://californiasmokeinfo.blogspot.com. 

For those inclined for more detailed graphing of hourly, 3-hr, and 24-hr PM2.5 averages in Yosemite Valley click here.  For other monitoring sites in the Central Sierra click here.