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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>11:50 AM PDT THU JUL 12, 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 to 7:00 p.m.<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>A large upper-level ridge remains centered over the southwestern United States, with a dry and warm southwesterly flow aloft over Oregon. A weak upper-level trough is just off the Washington coast. It has very limited moisture but is increasing the southwesterly flow aloft and onshore transport flow across western Oregon. That is improving air quality and pushing residual wildfire smoke east of the region.<o:p></o:p></p><p class=MsoNoSpacing><o:p> </o:p></p><p class=MsoNoSpacing>Increasing onshore flow brought some marine clouds into the extreme northern and southern sections of the Willamette Valley this morning. Low clouds and fog continue to blanket the coastline late this morning, with considerable high clouds stretching across the interior of western Oregon. Onshore Pressure gradients, from Newport to Redmond, have increased to more than 6 millibars late this morning. Corvallis has westerly winds in excess of 10 mph…indicating that a marine push is initiating into the Willamette Valley.<o:p></o:p></p><p class=MsoNoSpacing><o:p> </o:p></p><p class=MsoNoSpacing>Transport winds, which have been northerly the past couple of days, will turn northwesterly today; capping temperatures in the mid 80s (a few degrees cooler than yesterday). The air mass is still quite warm, but minor cooling aloft, combined with daytime heating, should help afternoon mixing heights climb to near 3500 feet.<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>Considerable high clouds with a developing sea breeze this afternoon.<o:p></o:p></p><p class=MsoNoSpacing><o:p> </o:p></p><p class=MsoNoSpacing>Salem's high temperature today will be near 85 degrees (normal is 82).<o:p></o:p></p><p class=MsoNoSpacing>Relative humidity drops to near 35% by 5 p.m.<o:p></o:p></p><p class=MsoNoSpacing>Surface winds: NW 7-12 mph.<o:p></o:p></p><p class=MsoNoSpacing>Transport winds: NW 10-15 mph.<o:p></o:p></p><p class=MsoNoSpacing>Mixing height: Rising to near 3500 feet this afternoon.<o:p></o:p></p><p class=MsoNoSpacing>Salem’s sunset tonight: 8:57 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: 80 84 77 <o:p></o:p></p><p class=MsoNoSpacing> Relative Humidity: 41% 36% 45%<o:p></o:p></p><p class=MsoNoSpacing> Surface Wind Direction: 320 320 300<o:p></o:p></p><p class=MsoNoSpacing> Surface Wind Speed: 8 10 8 <o:p></o:p></p><p class=MsoNoSpacing> Transport Wind Direction: 320 310 300 <o:p></o:p></p><p class=MsoNoSpacing> Transport Wind Speed: 10 12 12<o:p></o:p></p><p class=MsoNoSpacing> Mixing Height: 3200 3500 1500<o:p></o:p></p><p class=MsoNoSpacing> Ventilation Index: 32 42 18 <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>A very weak upper-level trough is forecast to stall over Oregon Friday and Saturday. That should maintain enough onshore flow to bring some morning marine clouds into the Willamette Valley, but expect plenty of sunshine in the afternoons with seasonably warm temperatures. A little stronger upper-level trough is forecast to drop into the region late Sunday and Monday. That will strengthen the onshore flow enough to cool temperatures below normal, by Monday, and introduce a slight chance of showers.<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>