WILDFIRE SMOKE FORECAST

OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE

1:30 PM PDT FRI AUG 23, 2013

 

SIGNIFICANT FIRE INFORMATION:

 

Douglas Complex Fires – Seven miles northwest of Glendale in Douglas and Josephine Counties.

 

Big Windy Complex – 25 miles NW of Grants Pass; 8 miles NW of Galice.

 

Whiskey Complex – 6 miles east of Tiller in the Umpqua National Forest.

 

Government Flats Complex – 10 miles SW of The Dalles.

 

For updated “Significant Fire” details, visit ODF’s fire blog at http://wildfireoregondeptofforestry.blogspot.com/ or the Northwest Interagency Coordination Center (NWCC) at http://www.nwccweb.us/index.aspx.

 

A “Significant Fire Potential” map, for ODF protected lands, is available at (http://nfdrs.smkmgt.com/ODF_Significant_Fire_Potential.png). 

 

AIR QUALITY:

 

Measurement locations over the entire state of Oregon (38 total locations today) show good air quality today.  Improvement in the past 24-48 hours has been significant over the southwestern OR locations downwind of the Douglas/Whiskey and Big Windy Complexes, as well as The Dalles area as a wind direction shift to westerly/NWly has occurred there. The exit of an upper-level wave to the northeast over the last 12-18 hours has helped lead to the air quality improvement and a reduction in elevated smoke over much of the state.

 

Statewide air quality index readings are available at http://www.deq.state.or.us/aqi/index.aspx

 

SMOKE DISPERSION FORECAST:

 

Wildfire smoke dispersion depends on the stability of the atmosphere as well as wind direction and speed.  A stable atmosphere holds smoke to the ground and an unstable atmosphere allows smoke to rise and dissipate.  Smoke is typically mixed to higher altitudes during the afternoon, when daytime heating destabilizes the air mass.  Conversely, smoke tends to settle near the ground and in drainages during the overnight and early morning hours.

 

TODAY:

 

Clearing and improvement in air quality has been the trend over the last 12-18 hours over much of the state, and any major reversal of this trend is unlikely over the next several days barring additional major ignitions. Residual low clouds remain only over portions of western OR. Transport winds have switched to mostly southwesterly for much of the state. Smoke production for the Government Flats Complex likely remains significant but is now moving generally to the east/SE into areas of no air quality measurements; it is likely air quality is still being impacted negatively immediately east and southeast of this complex.

 

 

 

 

Saturday and Sunday:

 

Upper southwesterly flow will dominate the picture through the weekend ahead of a deep eastern Pacific trough, with transport winds generally having a significant westerly component. This will lead to a continuation of local air quality impacts immediately NE-E-SE of active fire zones, especially the Government Flats Complex. Otherwise, good air quality conditions are expected to continue. The flow aloft will contain enough moisture that late-day shower/thunderstorm activity is likely to be generated over many higher terrain areas of the state both days, especially the Cascade Range. Additional lightning ignitions are possible in these areas although many of the strikes are likely to be accompanied by rain, and we are generally seeing better low-level moisture conditions currently than we’ve seen in quite some time. In fact a return to Red Flag conditions is unlikely for any areas of the state as a general cooling trend at the surface is in place.

 

EXTENDED OUTLOOK:

 

The deep eastern Pacific trough will persist at least through next Tuesday August 27, with some ejecting waves generating late-day shower/thunderstorm activity over western and central OR, especially over higher terrain. While some recovery in afternoon temperatures is expected over eastern portions of the state, a return to hot/dry conditions is not likely. We do not anticipate air quality impacts from smoke unless there are major new ignitions or if the Government Flats Complex continues to generate significant smoke. In the latter case the impacts would likely be confined to the east of the fires and local areas of poor ventilation close to the fires.

 

Current weather forecasts from the Portland, Medford, and Pendleton National Weather Service offices are available at:  http://www.wrh.noaa.gov/pqr/, http://www.wrh.noaa.gov/mfr/, and http://www.wrh.noaa.gov/pdt/ respectively.

 

This bulletin is also available on the web at

http://www.odf.state.or.us/DIVISIONS/protection/fire_protection/DAILY/wfsmoke.htm

 

ODF Smoke Management Meteorologist