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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>12:00 PM PDT MON AUG 08 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 12:30pm to 3:00pm with a 50 acre limit. <o:p></o:p></pre><pre>Propane flaming is allowed from 12:30pm to 5:00pm. <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 weak upper level trough is swinging over the Pacific Northwest today. The marine layer<o:p></o:p></pre><pre>is hanging tough and late morning satellite pictures show very few breaks. Consequently<o:p></o:p></pre><pre>valley temperatures have been slow to warm, with low to mid 60's common throughout the<o:p></o:p></pre><pre>region as of late morning. I have lowered the forecast high temperature for today. <o:p></o:p></pre><pre><o:p> </o:p></pre><pre>Strong gradient stacking continues and is unlikely to even out this afternoon. Pressure<o:p></o:p></pre><pre>gradients as of 11am included: Newport to Salem, just 0.9 mb onshore; Salem to Redmond,<o:p></o:p></pre><pre>4.2 mb onshore; total Newport to Redmond, 5.1 mb onshore. Meanwhile the Portland to<o:p></o:p></pre><pre>Medford gradient was 4.3 mb northerly.<o:p></o:p></pre><pre><o:p> </o:p></pre><pre>Latest models are a bit more optimistic about transport winds with more northwest than<o:p></o:p></pre><pre>shown earlier. However the University of Washington models show winds actually going<o:p></o:p></pre><pre>light northeasterly above a couple thousand feet by about sunset. This may reflect the<o:p></o:p></pre><pre>possibility of thunderstorm buildups over the Cascades later this afternoon. In any case<o:p></o:p></pre><pre>northeasterly winds developing in the transport region would argue against allowing any<o:p></o:p></pre><pre>burning this afternoon. <o:p></o:p></pre><pre><o:p> </o:p></pre><pre><o:p> </o:p></pre><pre>THIS AFTERNOON'S FORECAST:<o:p></o:p></pre><pre><o:p> </o:p></pre><pre>Cloudy through early afternoon then partly cloudy. <o:p></o:p></pre><pre>Salem's high temperature today will be near 77. (Average: 85)<o:p></o:p></pre><pre>Minimum relative humidity will be about 40%.<o:p></o:p></pre><pre>Surface winds: N to NW 6-10. <o:p></o:p></pre><pre>Transport winds: N-NNW 5 becoming NW 8-10 late afternoon or early evening. <o:p></o:p></pre><pre>Maximum mixing height: 3900<o:p></o:p></pre><pre>Sunset tonight: 8:29 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> 2pm 5pm 8pm <o:p></o:p></pre><pre> Temperature: 71 77 70 <o:p></o:p></pre><pre> Relative Humidity: 53% 40% 49% <o:p></o:p></pre><pre> Surface Wind Direction: 340 330 300 <o:p></o:p></pre><pre> Surface Wind Speed: 6 8 10 <o:p></o:p></pre><pre> Transport Wind Direction: 350 340 300 <o:p></o:p></pre><pre> Transport Wind Speed: 5 5 9 <o:p></o:p></pre><pre> Estimated Mixing Height: 3400 3900 1000<o:p></o:p></pre><pre> Ventilation Index: 19 20 9<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>Latest forecast charts show another weak upper level low approaching the Pacific<o:p></o:p></pre><pre>Northwest tomorrow for a very similar weather pattern to today's. At this point computer models do<o:p></o:p></pre><pre>not show any significant switch to a more westerly transport flow with this feature. <o:p></o:p></pre><pre><o:p> </o:p></pre><pre>Weak upper ridging should limit the morning marine clouds later in the week, but a<o:p></o:p></pre><pre>northerly transport wind pattern will continue through the week for very limited, if any,<o:p></o:p></pre><pre>burn opportunities. <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>