Monday, September 19, 2016

Monday, September 19, 2016 - Yosemite National Park Lakes Fire Smoke Effects Forecast #5

Yosemite National Park                                                                                               
Prepared: 9/19/16                                                                                                                          
Prepared by:  Jim McNitt, Air Resource Specialist
Overview: The Lakes Fire is burning in the Chilnualna Lakes area, between Turner Meadow and Buena Vista Peak at about 8,000 feet in a designated wilderness area in Mariposa County. It is a lightning-caused fire that is being monitored and managed for resource and wildlife benefit. Managing fires that are started by lightning reduces the risk of high intensity fires and benefits the ecosystem. The size is estimated to be approximately 587 acres based on ground reconnaissance completed on 9/17/16. A prescribed burn was conducted at Ahwahnee Meadow with ignitions on 9/12/16 and 9/13/16 for approximately 62 acres. Burn down and mop up was completed on 9/15/16. Smoke from other wildfires will continue to elevate PM2.5 levels in the park.
Smoke Synopsis: A temperature inversion will trap smoke in Yosemite Valley overnight but the temperature inversion will break down by noon.  Overnight smoke settled down the Chilnualna drainage to Wawona through the early morning today and several hourly PM2.5 readings at Wawona were greater than 35 µg/m3 this morning.  Afternoon upslope flow and overnight and early morning downslope flow will continue through Tuesday.
Air Quality Outlook: High pressure over the area will cause fair to poor dispersion conditions today and tomorrow.   Dispersion conditions will improve on Wednesday as a cold front approaches from the west and winds will be gusty Wednesday night. The cold front will pass through the area on Thursday. Expect gusty winds and good vertical mixing of smoke as the front moves through on Thursday. Dispersion conditions on Friday will be fair but dispersion conditions will deteriorate throughout the weekend and will be poor by Sunday.
9/18/16 Observed*
9/19/16 Forecasted
9/20/16  Forecasted
Details for avoiding smoke during the worst hours of the day
Yosemite Valley
Campfire smoke will be trapped under a surface inversion Monday night/Tuesday morning. The highest hourly readings will be between 10 PM and 6 AM.
El Portal

People with heart or lung disease, children and older adults should reduce prolonged or heavy outdoor exertion in the morning. The highest hourly readings will be between 5 AM and noon.
Disclaimer:  Air quality predictions reflect only fine particulate matter (PM2.5). Sensitive individuals including people with asthma or heart disease, infants, children, pregnant women and older adults should take precautions to avoid exposure to smoke. If you experience health effects from smoke, contact your health professional. *The Air Quality Index (AQI) values used to create the following table are 24-hr averages (midnight-midnight local time). Locations listed in the above table can experience periods of poorer air quality than the24-hr average.

24 hr AQI Category
(PM2.5 µg/m3)
Potential Health Impacts
Actions to Protect Yourself
Good (0-12)
Little or no health risk
Moderate (13-35)
Air quality is acceptable for most. There may be moderate health concern for a small number of sensitive people.
Unusually sensitive people should consider reducing prolonged or heavy outdoor exertion.
Unhealthy for Sensitive Groups – USG (36-55)
Members of sensitive groups may experience health effects.  The general public is not likely to be affected.
People with heart or lung disease, children and older adults should reduce prolonged or heavy outdoor exertion.  Everyone else should limit prolonged or heavy exertion.
Unhealthy (56-150)

Everyone may begin to experience more serious health effects.
The following groups should avoid all physical outdoor activity: People with heart or lung disease, children and older adults.  Everyone else should avoid prolonged or heavy exertion.
Very Unhealthy
Triggers a health alert, everyone may experience more serious health effects
Everyone should avoid any outdoor exertion; people with respiratory or heart disease, the elderly and children should remain indoors.
Hazardous (>250)
The entire population is even more likely to be affected by serious health effects.
The following groups should remain indoors and keep activity levels low: People with heart or lung disease; children and older adults. Everyone else should avoid prolonged or heavy exertion
Learn more at:
Air Monitor Data                                                
California Smoke Blog                                                                        
Air Districts                                        

AirNow (AQI forecasts and nowcasts)                     

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