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<p class="MsoNoSpacing">SILVERTON HILLS FIELD BURNING FORECAST<o:p></o:p></p>
<p class="MsoNoSpacing">OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE<o:p></o:p></p>
<p class="MsoNoSpacing">8:50 AM PDT FRI SEP 8, 2017<o:p></o:p></p>
<p class="MsoNoSpacing"><o:p> </o:p></p>
<p class="MsoNoSpacing"><b>BURN ADVISORY:<o:p></o:p></b></p>
<p class="MsoNoSpacing"><b><o:p> </o:p></b></p>
<p class="MsoNoSpacing">Agricultural burning is not recommended.<o:p></o:p></p>
<p class="MsoNoSpacing"><o:p> </o:p></p>
<p class="MsoNoSpacing">Prep burning is not allowed.<o:p></o:p></p>
<p class="MsoNoSpacing"><o:p> </o:p></p>
<p class="MsoNoSpacing"><b>WEATHER DISCUSSION:<o:p></o:p></b></p>
<p class="MsoNoSpacing"><o:p> </o:p></p>
<p class="MsoNoSpacing">An upper-level trough, centered just off the northern California coast, sent a surge of showers and thundershowers northward into Oregon on Thursday. Strong thunderstorms produced large hail and brief downpours in the northern Cascades
but only spotty very light rain in the Willamette Valley. A switch to weak onshore flow also began to clear wildfire smoke from the valley.<o:p></o:p></p>
<p class="MsoNoSpacing"><o:p> </o:p></p>
<p class="MsoNoSpacing">An upper-level trough remains over the region today, but the system off the California coast has drifted southward and will be less of a factor. Winds aloft have veered from SSE to the SSW, which will stabilize the air mass and inhibit
thunderstorm development. However, the air mass remains very moist, so light showers are possible.<o:p></o:p></p>
<p class="MsoNoSpacing"><o:p> </o:p></p>
<p class="MsoNoSpacing">Mostly cloudy skies and increasing onshore flow will hold temperatures in the 70s today. Elevated wildfire smoke should continue to slowly clear from the region. High humidity and light winds will limit burning opportunities.<o:p></o:p></p>
<p class="MsoNoSpacing"><o:p> </o:p></p>
<p class="MsoNoSpacing"><b>TODAY’S FORECAST:<o:p></o:p></b></p>
<p class="MsoNoSpacing"><o:p> </o:p></p>
<p class="MsoNoSpacing">Mostly cloudy, cooler, and humid. Not as smoky. A light shower is possible.<o:p></o:p></p>
<p class="MsoNoSpacing"><o:p> </o:p></p>
<p class="MsoNoSpacing">Salem's high temperature today will be near 76°F (average is 79°F).<o:p></o:p></p>
<p class="MsoNoSpacing">Relative humidity: Dropping to 60% about 2 p.m. and to 55% by 5 p.m.<o:p></o:p></p>
<p class="MsoNoSpacing">Surface winds: Light this morning; NW 5-10 mph this afternoon.<o:p></o:p></p>
<p class="MsoNoSpacing">Transport winds: N 5 mph this morning; becoming NW 10 mph this afternoon.<o:p></o:p></p>
<p class="MsoNoSpacing">Mixing height: Rising to 3000 feet by 2 p.m. and to 4000 feet by 5 p.m.<o:p></o:p></p>
<p class="MsoNoSpacing">Salem’s sunset tonight: 7:35 p.m.<o:p></o:p></p>
<p class="MsoNoSpacing"><o:p> </o:p></p>
<p class="MsoNoSpacing">(Salem Airport data for Thursday, September 7th: High 86°F; Rainfall: Trace)<o:p></o:p></p>
<p class="MsoNoSpacing">(Maximum Ventilation Index expected today: 40)<o:p></o:p></p>
<p class="MsoNoSpacing">
<o:p></o:p></p>
<p class="MsoNoSpacing"><b>EXTENDED DISCUSSION:<o:p></o:p></b></p>
<p class="MsoNoSpacing"><o:p> </o:p></p>
<p class="MsoNoSpacing">An upper-level trough is predicted to move across southern British Columbia on Saturday, dragging a weak cold front across NW Oregon in the afternoon. Temperatures will cool into the low 70s with a chance of light showers late in the
day. Strengthening onshore flow should further improve air quality.<o:p></o:p></p>
<p class="MsoNoSpacing"><o:p> </o:p></p>
<p class="MsoNoSpacing">A building upper-level ridge is expected to turn transport winds northerly on Sunday, and offshore on Monday, as temperatures climb back to above normal. Wildfire smoke may get transported back into the region. Onshore flow could return
as soon as Tuesday, initiating a cooling trend, improving air quality, and possibly creating burning opportunities.
<o:p></o:p></p>
<p class="MsoNoSpacing"><o:p> </o:p></p>
<p class="MsoNoSpacing">The National Weather Service’s digital forecast is available at:<o:p></o:p></p>
<p class="MsoNoSpacing"><a href="http://forecast.weather.gov/MapClick.php?lat=44.90549606158295&lon=-122.8106689453125&site=pqr&unit=0&lg=en&FcstType=text">http://forecast.weather.gov/MapClick.php?lat=44.90549606158295&lon=-122.8106689453125&site=pqr&unit=0&lg=en&FcstType=text</a><o:p></o:p></p>
<p class="MsoNoSpacing"><o:p> </o:p></p>
<p class="MsoNoSpacing">Notes:<o:p></o:p></p>
<p class="MsoNoSpacing">
<o:p></o:p></p>
<p class="MsoNoSpacing"> 1. Mixing height, as used here, is the lowest height at which the<o:p></o:p></p>
<p class="MsoNoSpacing"> potential temperature exceeds the potential temperature at the<o:p></o:p></p>
<p class="MsoNoSpacing"> surface. As a practical matter it is the approximate height to<o:p></o:p></p>
<p class="MsoNoSpacing"> which a smoke plume will rise assuming good ignition, dry fuels,<o:p></o:p></p>
<p class="MsoNoSpacing"> and winds less than about 15 mph.<o:p></o:p></p>
<p class="MsoNoSpacing">
<o:p></o:p></p>
<p class="MsoNoSpacing"> 2. Transport winds are a layer average through the mixing height,
<o:p></o:p></p>
<p class="MsoNoSpacing"> weighted slightly toward the winds at the top of the layer.<o:p></o:p></p>
<p class="MsoNoSpacing">
<o:p></o:p></p>
<p class="MsoNoSpacing"> 3. Ventilation Index is the height of the mixing layer (ft) times
<o:p></o:p></p>
<p class="MsoNoSpacing"> the transport wind speed (mph) divided by 1000.<o:p></o:p></p>
<p class="MsoNoSpacing">
<o:p></o:p></p>
<p class="MsoNoSpacing"> 4. Surface wind direction is the general expected wind direction.
<o:p></o:p></p>
<p class="MsoNoSpacing"> At a specific point surface winds are highly dependent on local<o:p></o:p></p>
<p class="MsoNoSpacing"> terrain conditions. <o:p></o:p></p>
<p class="MsoNoSpacing"><o:p> </o:p></p>
<p class="MsoNormal"> 5. In accordance with OAR 837-110-0090, all field burning shall be
<span style="font-family:"Calibri",sans-serif"><o:p></o:p></span></p>
<p class="MsoNormal"> banned when any two of the following criteria are present:<o:p></o:p></p>
<p class="MsoNormal"> A. Temperature of 95 degrees Fahrenheit or above<o:p></o:p></p>
<p class="MsoNormal"> B. Relative humidity of 30 percent or below
<o:p></o:p></p>
<p class="MsoNormal"> C. Wind speed of 15 miles per hour or higher<o:p></o:p></p>
<p class="MsoNoSpacing"><o:p> </o:p></p>
<p class="MsoNoSpacing">This forecast is provided under an agreement between the Oregon Department<o:p></o:p></p>
<p class="MsoNoSpacing">of Agriculture (ODA) and the Oregon Department of Forestry (ODF). For<o:p></o:p></p>
<p class="MsoNoSpacing">information contact ODA at 503-986-4701.<o:p></o:p></p>
<p class="MsoNoSpacing"><o:p> </o:p></p>
<p class="MsoNoSpacing"><b>To add/remove your email address from this list, please go to:<o:p></o:p></b></p>
<p class="MsoNoSpacing"><o:p> </o:p></p>
<p class="MsoNoSpacing"><a href="http://listsmart.osl.state.or.us/mailman/listinfo/willamette-fcst">http://listsmart.osl.state.or.us/mailman/listinfo/willamette-fcst</a><o:p></o:p></p>
<p class="MsoNoSpacing"><o:p> </o:p></p>
<p class="MsoNoSpacing">Pete Parsons<o:p></o:p></p>
<p class="MsoNoSpacing">ODF Meteorologist<o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"><o:p> </o:p></span></p>
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