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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link=blue vlink=purple><div class=WordSection1><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>11:45 AM PDT WED AUG 01, 2012<o:p></o:p></p><p class=MsoNoSpacing><o:p> </o:p></p><p class=MsoNoSpacing>BURN ADVISORY:<o:p></o:p></p><p class=MsoNoSpacing><o:p> </o:p></p><p class=MsoNoSpacing>Agricultural burning is not recommended.<o:p></o:p></p><p class=MsoNoSpacing>Prep burning is allowed from 12:00pm to 2:00pm with a 50 acre limit. <o:p></o:p></p><p class=MsoNoSpacing>Propane flaming is allowed from 12:00pm to 5:00pm. <o:p></o:p></p><p class=MsoNoSpacing> <o:p></o:p></p><p class=MsoNoSpacing>WEATHER DISCUSSION:<o:p></o:p></p><p class=MsoNoSpacing><o:p> </o:p></p><p class=MsoNoSpacing>Weak upper level trough to zonal-like pattern remains over the Pacific Northwest today. Satellite picture shows marine low clouds dissipating out of the Willamette Valley as temperatures warm. <o:p></o:p></p><p class=MsoNoSpacing><o:p> </o:p></p><p class=MsoNoSpacing>Expect little change in the upper air pattern today with only a minor disturbance moving down from the north later today and tonight. Mixing heights rise to similar levels as yesterday reaching about 3000 ft around noon and 4500 ft by late afternoon. Transport and surface winds will be mostly a light NW to N.<o:p></o:p></p><p class=MsoNoSpacing><o:p> </o:p></p><p class=MsoNoSpacing>Pressure gradient stacking has increased to the east with gradients 1.3 mb onshore from Newport to Salem and 3.3 mb onshore from Salem to Redmond. Portland to Medford gradient is 3.9 mb northerly. Gradients should increase some over the Coast Range this afternoon but probably not enough to overtake the gradient stacking over the Cascades.<o:p></o:p></p><p class=MsoNoSpacing><o:p> </o:p></p><p class=MsoNoSpacing>TODAY’S FORECAST:<o:p></o:p></p><p class=MsoNoSpacing><o:p> </o:p></p><p class=MsoNoSpacing>Sunny and warm<o:p></o:p></p><p class=MsoNoSpacing><o:p> </o:p></p><p class=MsoNoSpacing>Salem's high temperature today will be near 81.<o:p></o:p></p><p class=MsoNoSpacing>Relative humidity drops to 50% by 1:00 pm. Minimum relative humidity 35%.<o:p></o:p></p><p class=MsoNoSpacing>Surface winds: NNW to N at 4 - 8 mph<o:p></o:p></p><p class=MsoNoSpacing>Transport winds: NNW at 6 - 10 mph during the afternoon<o:p></o:p></p><p class=MsoNoSpacing>Maximum mixing height: 4500 feet <o:p></o:p></p><p class=MsoNoSpacing>Sunset tonight: 8:37 pm <o:p></o:p></p><p class=MsoNoSpacing> <o:p></o:p></p><p class=MsoNoSpacing> <o:p></o:p></p><p class=MsoNoSpacing>THREE-HOURLY DATA: <o:p></o:p></p><p class=MsoNoSpacing> 2pm 5pm 8pm <o:p></o:p></p><p class=MsoNoSpacing> Temperature: 77 81 70 <o:p></o:p></p><p class=MsoNoSpacing> Relative Humidity: 42% 35% 49%<o:p></o:p></p><p class=MsoNoSpacing> Surface Wind Direction: 350 350 320<o:p></o:p></p><p class=MsoNoSpacing> Surface Wind Speed: 7 8 8 <o:p></o:p></p><p class=MsoNoSpacing> Transport Wind Direction: 350 340 320 <o:p></o:p></p><p class=MsoNoSpacing> Transport Wind Speed: 7 8 11<o:p></o:p></p><p class=MsoNoSpacing> Estimated Mixing Height: 3800 4500 2000<o:p></o:p></p><p class=MsoNoSpacing> Ventilation Index: 27 36 22<o:p></o:p></p><p class=MsoNoSpacing> <o:p></o:p></p><p class=MsoNoSpacing>EXTENDED DISCUSSION:<o:p></o:p></p><p class=MsoNoSpacing><o:p> </o:p></p><p class=MsoNoSpacing>Upper level trough moves down from the north and may increase the onshore flow tomorrow afternoon. It's still questionable, however, whether it will be enough for a burning opportunity. This trough will move to the east Friday giving way to an upper ridge. Expect warming conditions through the weekend with mostly northerly to offshore flow.<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, and <o:p></o:p></p><p class=MsoNoSpacing> winds less than about 15mph.<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 times <o:p></o:p></p><p class=MsoNoSpacing> the transport wind speed 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=MsoNoSpacing>This forecast is provided under an agreement between the Oregon Department of<o:p></o:p></p><p class=MsoNoSpacing>Agriculture and the Oregon Department of Forestry. For information contact ODA at 503-986-4701.<o:p></o:p></p><p class=MsoNoSpacing><o:p> </o:p></p><p class=MsoNoSpacing>Nick Yonker<o:p></o:p></p><p class=MsoNoSpacing>ODF Meteorologist<o:p></o:p></p><p class=MsoNoSpacing><o:p> </o:p></p><p class=MsoNormal><o:p> </o:p></p></div></body></html>