WILDFIRE SMOKE FORECAST
OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE
10:25 AM PDT TUE JUL 22, 2014
SIGNIFICANT FIRE INFORMATION:
Numerous wildfires extend across central and eastern Oregon.
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).
DEQ smoke monitoring sensors are indicating generally “good” air quality statewide, except for “moderate” air quality in Madras and Prineville.
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.
An upper-level trough, centered just off the northern Vancouver Island coast, is producing a moist southwesterly flow aloft over Oregon. That is helping to decrease fire behavior and related smoke impacts. Transport winds are generally S-SW across central and eastern Oregon, so areas to the N-NE of active fires are most likely to have elevated smoke levels.
A potent upper-level trough will approach the Oregon coast on Wednesday, which will increase the moisture and instability over the region. Expect widespread showers with a chance of thunderstorms. Rainfall totals will vary but should be greatest across the northern half of the state. Expect a continued decrease in fire behavior and related smoke, but new fire starts, due to lightning, are possible. Transport winds will remain mostly S-SW across central and eastern Oregon.
Showers may linger through Thursday morning, followed by dry and warmer weather into the weekend. Wildfire smoke impacts will be dependent upon new fire starts and the progress of control on existing fires, both of which are impossible to accurately predict. However, mixing will generally begin to deteriorate with transport winds veering to W-N on Thursday and becoming light N-NE Friday. Communities directly to the SW-SE of active fires will become more vulnerable to smoke impacts.
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
ODF Smoke Management Meteorologist