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<p class="MsoNormal">SILVERTON HILLS FIELD BURNING FORECAST<o:p></o:p></p>
<p class="MsoNormal">OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE<o:p></o:p></p>
<p class="MsoNormal">8:45 AM PDT TUE JUL 18, 2017<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">BURN ADVISORY:<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Agricultural burning is not recommended.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Prep burning is not allowed.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">WEATHER DISCUSSION:<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">A disturbance over the Pacific Ocean creates SW flow aloft, allowing onshore flow at the surface to redevelop. Gradients are balanced, mixing becomes favorable around noon, but wind direction will be a limiting factor with N-NE transport
winds currently that will turn NW later this afternoon. <o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">TODAY’S FORECAST:<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Mostly Sunny becoming Partly Cloudy this afternoon.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Salem's high temperature today will be near 83°F (average is 83°F).<o:p></o:p></p>
<p class="MsoNormal">Relative humidity: Dropping below 60% by 10 a.m. and dropping near 25% by 5 p.m.<o:p></o:p></p>
<p class="MsoNormal">Surface winds: N 5-10 mph this morning; shifting NW 5-10 mph this afternoon.<o:p></o:p></p>
<p class="MsoNormal">Transport winds: N-NE 5-10 mph this morning; NW 10 mph this afternoon shifting to SW at top of Mixed Layer.<o:p></o:p></p>
<p class="MsoNormal">Mixing height: Rising to 3000 feet around 12 p.m. and to 5000 feet by 5 p.m.<o:p></o:p></p>
<p class="MsoNormal">Salem’s sunset tonight: 8:53 p.m.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">(Salem Airport data for Monday, July 17th: High 83°F; Rainfall: .00”)<o:p></o:p></p>
<p class="MsoNormal">(Maximum Ventilation Index expected today: 50)<o:p></o:p></p>
<p class="MsoNormal">
<o:p></o:p></p>
<p class="MsoNormal">EXTENDED DISCUSSION:<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">SW flow aloft persists through the week for the Silverton Hills, as a disturbance over the Pacific Ocean pushes weak fronts into Oregon. Onshore flow builds with W-SW flow aloft and indicates more W-NW surface flow Wednesday afternoon across
the Willamette Valley ahead of a marine push. The disturbance gathers moisture by Wednesday night and moves across the Willamette Valley Thursday morning with patchy fog & drizzle that clears out by early afternoon. W flow aloft with onshore flow on Friday
appears particularly suited for field burning operations, if gradients stack favorably through the day.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">The National Weather Service’s digital forecast is available at:<o:p></o:p></p>
<p class="MsoNormal">http://forecast.weather.gov/MapClick.php?lat=44.90549606158295&lon=-122.8106689453125&site=pqr&unit=0&lg=en&FcstType=text<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Notes:<o:p></o:p></p>
<p class="MsoNormal">
<o:p></o:p></p>
<p class="MsoNormal"> 1. Mixing height, as used here, is the lowest height at which the<o:p></o:p></p>
<p class="MsoNormal"> potential temperature exceeds the potential temperature at the<o:p></o:p></p>
<p class="MsoNormal"> surface. As a practical matter it is the approximate height to<o:p></o:p></p>
<p class="MsoNormal"> which a smoke plume will rise assuming good ignition, dry fuels,<o:p></o:p></p>
<p class="MsoNormal"> and winds less than about 15 mph.<o:p></o:p></p>
<p class="MsoNormal">
<o:p></o:p></p>
<p class="MsoNormal"> 2. Transport winds are a layer average through the mixing height,
<o:p></o:p></p>
<p class="MsoNormal"> weighted slightly toward the winds at the top of the layer.<o:p></o:p></p>
<p class="MsoNormal">
<o:p></o:p></p>
<p class="MsoNormal"> 3. Ventilation Index is the height of the mixing layer (ft) times
<o:p></o:p></p>
<p class="MsoNormal"> the transport wind speed (mph) divided by 1000.<o:p></o:p></p>
<p class="MsoNormal">
<o:p></o:p></p>
<p class="MsoNormal"> 4. Surface wind direction is the general expected wind direction.
<o:p></o:p></p>
<p class="MsoNormal"> At a specific point surface winds are highly dependent on local<o:p></o:p></p>
<p class="MsoNormal"> terrain conditions.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">This forecast is provided under an agreement between the Oregon Department<o:p></o:p></p>
<p class="MsoNormal">of Agriculture (ODA) and the Oregon Department of Forestry (ODF). For<o:p></o:p></p>
<p class="MsoNormal">information contact ODA at 503-986-4701.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">To add/remove your email address from this list, please go to:<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">http://listsmart.osl.state.or.us/mailman/listinfo/willamette-fcst<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Tom Jenkins, AEM<o:p></o:p></p>
<p class="MsoNormal">ODF Meteorologist<o:p></o:p></p>
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