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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 FRI SEP 07 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 burning is not recommended.<o:p></o:p></p><p class=MsoNoSpacing>Prep burning is not allowed. <o:p></o:p></p><p class=MsoNoSpacing>Propane flaming is not allowed. <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>Upper level ridge continues to build over the state today with a minor low pressure area to the southwest in the eastern Pacific. Expect mostly sunny skies.<o:p></o:p></p><p class=MsoNoSpacing><o:p> </o:p></p><p class=MsoNoSpacing>Expect mixing to slowly improve this afternoon with the heating of the day. Maximum mixing rises to about 4000 ft. Transport winds will be light N to NE, and then turn NW’erly this evening.<o:p></o:p></p><p class=MsoNoSpacing><o:p> </o:p></p><p class=MsoNoSpacing>Surface pressure pattern shows the thermal trough along the western side of the Willamette Valley extending to the northern Oregon coast. Current pressure gradients are .8 mb onshore from Newport to Salem and 4.5 mb offshore from Salem to Redmond. The thermal trough will remain in the Willamette Valley throughout the day with increasing onshore flow over the Coast Range with offshore flow remaining but weakening 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<o:p></o:p></p><p class=MsoNoSpacing><o:p> </o:p></p><p class=MsoNoSpacing>Salem's high temperature today will be near 93.<o:p></o:p></p><p class=MsoNoSpacing>Relative humidity: Minimum relative humidity 22%.<o:p></o:p></p><p class=MsoNoSpacing>Surface winds: Mostly northerly at 4-7 mph, turning NW’erly during the evening.<o:p></o:p></p><p class=MsoNoSpacing>Transport winds: N to NE at 5-8 mph, turning NW’erly during the evening.<o:p></o:p></p><p class=MsoNoSpacing>Maximum mixing height: near 4000 ft.<o:p></o:p></p><p class=MsoNoSpacing>Sunset tonight: 7:36 pm <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: 85 93 81 <o:p></o:p></p><p class=MsoNoSpacing> Relative Humidity: 30% 22% 35%<o:p></o:p></p><p class=MsoNoSpacing> Surface Wind Direction: 360 360 320<o:p></o:p></p><p class=MsoNoSpacing> Surface Wind Speed: 7 7 5 <o:p></o:p></p><p class=MsoNoSpacing> Transport Wind Direction: 020 030 310 <o:p></o:p></p><p class=MsoNoSpacing> Transport Wind Speed: 7 6 6<o:p></o:p></p><p class=MsoNoSpacing> Estimated Mixing Height: 2700 4000 1500<o:p></o:p></p><p class=MsoNoSpacing> Ventilation Index: 18 23 9<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 ridge will shift eastward on Saturday as the upper low in the eastern Pacific develops into a trough and starts moving inland over the weekend. This will bring some cooling over the region tomorrow and a chance of thunderstorms over the Cascades. Pressure pattern turns onshore. Skies, however, should remain mostly clear in the Willamette Valley. <o:p></o:p></p><p class=MsoNoSpacing><o:p> </o:p></p><p class=MsoNoSpacing>The trough will strengthen and move inland on Sunday bringing further cooling as marine low clouds move into the Valley. Another trough will drop down from the northwest Sunday evening and may produce some light rain over the region early Monday. This trough will quickly move to the east late Monday and Tuesday with another upper ridge moving in for the middle of 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>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>