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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link=blue vlink=purple><div class=WordSection1><pre>SILVERTON HILLS FIELD BURNING FORECAST<o:p></o:p></pre><pre>OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE<o:p></o:p></pre><pre>9:00 AM PDT MON AUG 01 2011<o:p></o:p></pre><pre><o:p> </o:p></pre><pre>BURN ADVISORY:<o:p></o:p></pre><pre><o:p> </o:p></pre><pre>Agricultural burning burning is not recommended.<o:p></o:p></pre><pre>Prep burning is allowed from 12:00pm to 6:00pm with a 50 acre limit. <o:p></o:p></pre><pre>Propane flaming is allowed from 12:00pm to 6:00pm. <o:p></o:p></pre><pre> <o:p></o:p></pre><pre><o:p> </o:p></pre><pre>WEATHER DISCUSSION:<o:p></o:p></pre><pre><o:p> </o:p></pre><pre>A broad but weak upper level trough covers western North America and the northeastern<o:p></o:p></pre><pre>Pacific this morning. Satellite pictures show nearly clear skies over northwestern<o:p></o:p></pre><pre>Oregon with just a few areas of patchy morning fog.<o:p></o:p></pre><pre><o:p> </o:p></pre><pre>Pressure gradients are weakly onshore and should remain onshore throughout the day,<o:p></o:p></pre><pre>although gradient stacking to the east will continue. <o:p></o:p></pre><pre><o:p> </o:p></pre><pre>Low level winds are generally northerly this morning, but should turn more northwesterly<o:p></o:p></pre><pre>this afternoon.<o:p></o:p></pre><pre><o:p> </o:p></pre><pre>The morning Salem sounding was similar to yesterday's morning sounding above 5000 feet<o:p></o:p></pre><pre>but showed some cooling below 3000 feet. This has made the atmosphere a little more<o:p></o:p></pre><pre>stable today. Inversions were noted from about 1700 feet to 2200 feet, from 2900 feet to<o:p></o:p></pre><pre>3000 feet and from 4100 feet to 4800 feet. With ample heating today these inversions<o:p></o:p></pre><pre>should mix out, however, and the maximum mixing height this afternoon should reach 5000<o:p></o:p></pre><pre>feet. A 3000 foot mixing height should be reached by about noon. <o:p></o:p></pre><pre><o:p> </o:p></pre><pre>Good mixing heights this afternoon and a potential shift to a more favorable wind<o:p></o:p></pre><pre>direction late this afternoon may provide a burning opportunity. The limiting factor<o:p></o:p></pre><pre>would be gradient stacking east, which implies atmospheric subsidence, which implies<o:p></o:p></pre><pre>smoke hanging up in the Cascades and drifting back into the Willamette Valley during the<o:p></o:p></pre><pre>overnight hours. <o:p></o:p></pre><pre><o:p> </o:p></pre><pre>Winds and pressure gradients will be monitored carefully throughout the day. <o:p></o:p></pre><pre><o:p> </o:p></pre><pre>TODAY'S FORECAST:<o:p></o:p></pre><pre><o:p> </o:p></pre><pre>Sunny and warm. <o:p></o:p></pre><pre>Salem's high temperature today will be near 86.<o:p></o:p></pre><pre>Relative humidity drops to 50% by 10am. Minimum relative humidity 29%.<o:p></o:p></pre><pre>Surface winds: Northerly 4 to 6 mph this morning shifting to northwesterly 6-9 after<o:p></o:p></pre><pre>about 3pm. <o:p></o:p></pre><pre>Transport winds: Northerly about 5 mph this morning gradually backing to northwesterly<o:p></o:p></pre><pre>late this afternoon then westerly at about 5 this evening. <o:p></o:p></pre><pre>Maximum mixing height: 5000 feet.<o:p></o:p></pre><pre>Sunset tonight: 8:39 pm. <o:p></o:p></pre><pre> <o:p></o:p></pre><pre> <o:p></o:p></pre><pre>THREE-HOURLY DATA: <o:p></o:p></pre><pre> 11am 2pm 5pm 8pm <o:p></o:p></pre><pre> Temperature: 73 81 85 77 <o:p></o:p></pre><pre> Relative Humidity: 48% 35% 29% 39%<o:p></o:p></pre><pre> Surface Wind Direction: 010 340 310 280<o:p></o:p></pre><pre> Surface Wind Speed: 4 5 7 7 <o:p></o:p></pre><pre> Transport Wind Direction: 360 340 320 300 <o:p></o:p></pre><pre> Transport Wind Speed: 5 5 5 5<o:p></o:p></pre><pre> Estimated Mixing Height: 2800 4200 5000 1000<o:p></o:p></pre><pre> Ventilation Index: 14 21 25 5<o:p></o:p></pre><pre> <o:p></o:p></pre><pre>EXTENDED DISCUSSION:<o:p></o:p></pre><pre><o:p> </o:p></pre><pre>An onshore flow pattern should continue through the week with minor upper level<o:p></o:p></pre><pre>disturbances moving west to east mostly to the north of the area. This should present<o:p></o:p></pre><pre>occasional burning opportunities that need to be assessed on a day to day basis.<o:p></o:p></pre><pre>Temperatures should be near to slightly above average and no rain is likely through<o:p></o:p></pre><pre>through the week and into the weekend. <o:p></o:p></pre><pre><o:p> </o:p></pre><pre><o:p> </o:p></pre><pre>The National Weather Service’s digital forecast is available at <o:p></o:p></pre><pre><a href="http://forecast.weather.gov/MapClick.php?lat=44.905&lon=-122.810">http://forecast.weather.gov/MapClick.php?lat=44.905&lon=-122.810</a>.<o:p></o:p></pre><pre> <o:p></o:p></pre><pre>Notes: <o:p></o:p></pre><pre>1. Mixing height, as used here, is the lowest height at which the <o:p></o:p></pre><pre> potential temperature exceeds the equivalent potential temperature <o:p></o:p></pre><pre> at the surface. As a practical matter it is the approximate height <o:p></o:p></pre><pre> to which a smoke plume will rise assuming good ignition, dry fuels, <o:p></o:p></pre><pre> and winds less than about 15mph. <o:p></o:p></pre><pre>2. Transport winds are a layer average through the mixing height, <o:p></o:p></pre><pre> weighted slightly toward the winds at the top of the layer. <o:p></o:p></pre><pre>3. Ventilation Index is the height of the mixing layer times <o:p></o:p></pre><pre> the transport wind speed divided by 1000. <o:p></o:p></pre><pre>4. Surface wind direction is the general expected wind direction. <o:p></o:p></pre><pre> At a specific point surface winds are highly dependent on <o:p></o:p></pre><pre> local terrain conditions.<o:p></o:p></pre><pre> <o:p></o:p></pre><pre>This forecast is provided under an agreement between the Oregon Department of<o:p></o:p></pre><pre>Agriculture and the Oregon Department of Forestry. For information contact ODA<o:p></o:p></pre><pre>at 503-986-4701. <o:p></o:p></pre><pre><o:p> </o:p></pre><pre>Jim Little<o:p></o:p></pre><pre>ODF Meteorologist<o:p></o:p></pre><pre><o:p> </o:p></pre><pre><o:p> </o:p></pre><pre><o:p> </o:p></pre><pre><o:p> </o:p></pre><pre><o:p> </o:p></pre><pre><o:p> </o:p></pre><p class=MsoNormal><o:p> </o:p></p></div></body></html>