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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>11:35 AM PDT WED AUG 8, 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>Recommended burn times for agricultural burning are from noon until 6:30 p.m.<o:p></o:p></p><p class=MsoNoSpacing>Prep burning is allowed from noon until 2:00 p.m. with a 50 acre limit. <o:p></o:p></p><p class=MsoNoSpacing>Propane flaming is allowed from noon until 5:00 p.m. <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>Late morning satellite imagery continued to show marine low clouds covering most of northwestern Oregon, but some breaks in the overcast were beginning to appear in the central Willamette Valley. The low clouds should slowly break up this afternoon, with high temperatures likely staying in the 70s. Cooler air aloft will result in high afternoon mixing heights. However, there continues to be significant pressure gradient stacking east of the Willamette Valley. That is not conducive to good ventilation, for burning, and is unlikely to reverse this afternoon.<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>Slowly clearing skies this afternoon. Cooler.<o:p></o:p></p><p class=MsoNoSpacing><o:p> </o:p></p><p class=MsoNoSpacing>Salem's high temperature today will be near 78 degrees (normal is 83).<o:p></o:p></p><p class=MsoNoSpacing>Relative humidity drops to near 40% by 5 p.m.<o:p></o:p></p><p class=MsoNoSpacing>Surface winds: SW 5-10; Becoming NNW 5-10 mph this afternoon.<o:p></o:p></p><p class=MsoNoSpacing>Transport winds: SW 5-10; Becoming NNW 7-12 mph this afternoon.<o:p></o:p></p><p class=MsoNoSpacing>Mixing height: Rising to near 5000 feet by 5 p.m.<o:p></o:p></p><p class=MsoNoSpacing>Salem’s sunset tonight: 8:28 p.m. <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> 2 p.m. 5 p.m. 8 p.m. <o:p></o:p></p><p class=MsoNoSpacing> Temperature: 75 78 71 <o:p></o:p></p><p class=MsoNoSpacing> Relative Humidity: 47% 42% 57%<o:p></o:p></p><p class=MsoNoSpacing> Surface Wind Direction: 330 350 340<o:p></o:p></p><p class=MsoNoSpacing> Surface Wind Speed: 5 7 9 <o:p></o:p></p><p class=MsoNoSpacing> Transport Wind Direction: 310 340 340 <o:p></o:p></p><p class=MsoNoSpacing> Transport Wind Speed: 6 9 12<o:p></o:p></p><p class=MsoNoSpacing> Mixing Height: 4500 5000 3000<o:p></o:p></p><p class=MsoNoSpacing> Ventilation Index: 27 45 36 <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>Another weak upper-level trough will maintain the onshore flow pattern across western Oregon, on Thursday, with morning clouds giving way to afternoon sunshine. Gradient stacking may, once again, be unfavorable for open burning, and transport winds will be mostly northerly. A weak westerly flow aloft, on Friday, will maintain a pattern of morning clouds and afternoon sunshine. Temperatures should stay near normal. Northerly transport winds will keep the potential for burning opportunities low. Little change to the weather pattern is forecast through early next week.<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>Pete Parsons<o:p></o:p></p><p class=MsoNoSpacing>ODF Meteorologist<o:p></o:p></p></div></body></html>