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<div>SILVERTON HILLS FIELD BURNING FORECAST</div>
<div>OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE</div>
<div>9:00 AM PDT MON AUG 30 2010</div>
<div> </div>
<div>BURN ADVISORY:</div>
<div> </div>
<div> Recommended burn times for agricultural burning are from 9:00am to 6:00pm.</div>
<div> Prep burning is not allowed. </div>
<div> Propane flaming is not allowed. </div>
<div> </div>
<div>WEATHER DISCUSSION:</div>
<div> </div>
<div> Fall-like weather has settled in over the Pacific Northwest for the next few</div>
<div> days. </div>
<div> </div>
<div> A fairly broad upper level trough extends from the Yukon, across the Pacific</div>
<div> Northwest and southward to off the northwestern Mexican coast. Impulses rotating</div>
<div> through this trough will keep clouds and a chance for some light rain in the</div>
<div> forecast through mid week.</div>
<div> </div>
<div> Satellite pictures this morning show an area of thick clouds moving WNW to ESE</div>
<div> across the Valley. This cloud mass has produced rain across much of the area</div>
<div> this morning. Amounts include .11 at the Salem Airport and .15 at Jordan Valley.</div>
<div> </div>
<div> A weak Pacific front will move through western Oregon today followed by drying</div>
<div> overnight prior to another disturbance which should produce similar amounts of</div>
<div> rain tomorrow afternoon and evening.</div>
<div> </div>
<div> The morning Salem sounding showed a cool, moist air mass. Maximum mixing heights</div>
<div> will reach a bit over 3000 feet this afternoon, however wet fields should</div>
<div> preclude any open field burning today.</div>
<div> </div>
<div> Expect clouds, light rain and cool weather. Temperatures will be about 15</div>
<div> degrees below average for late August. Salem's high temperature today will be</div>
<div> near 65. Minimum relative humidity will be about 52%.</div>
<div> </div>
<div> Sunset tonight: 7:47 pm</div>
<div> </div>
<div>THREE-HOURLY DATA: </div>
<div> 11am 2pm 5pm 8pm </div>
<div> Temperature: 59 63 65 62 </div>
<div> Relative Humidity: 69% 56% 52% 62% </div>
<div> Surface Wind Direction: 030 220 290 270 </div>
<div> Surface Wind Speed: 4 4 6 5 </div>
<div> Transport Wind Direction: 120 150 190 190 </div>
<div> Transport Wind Speed: 10 5 5 3 </div>
<div> Estimated Mixing Height: 2000 2800 3200 500</div>
<div> Ventilation Index: 20 14 16 2</div>
<div> </div>
<div>EXTENDED DISCUSSION:</div>
<div> </div>
<div> A flat upper level ridge will begin building over the area later Wednesday for a</div>
<div> warming and drying trend. Longer range models show this flat ridge continuing</div>
<div> Thursday and Friday. Although the ridge will be weak there are indications that</div>
<div> a slight offshore wind component could develop. This would allow for clearing</div>
<div> skies and warmer weather, with temperatures back into the 80's. However,</div>
<div> offshore winds are not favorable for open field burning. </div>
<div> </div>
<div> Computer models suggest that another upper level trough will move over the</div>
<div> region sometime early in the coming weekend. Thus, any period of warming at</div>
<div> week's end will likely be short lived.</div>
<div> </div>
<div>EXTENDED FORECAST: </div>
<div> </div>
<div> Tuesday: Mostly cloudy, 65. Increasing chance of rain late. Wind SW 5-8 mph. A </div>
<div> Wednesday: Mostly cloudy, chance of light rain. High 70. Wind S 5. </div>
<div> Thursday Night: Partly cloudy, with a low around 52. </div>
<div> Friday: Mostly sunny, with a high near 82. </div>
<div> Saturday: Mostly cloudy, 78. </div>
<div> Sunday: Partly sunny, with a high near 77. </div>
<div> </div>
<div>Notes: </div>
<div> 1. Mixing height, as used here, is the lowest height at which the</div>
<div> potential temperature exceeds the potential temperature at the surface. </div>
<div> As a practical matter it is the approximate height to which a </div>
<div> smoke plume will rise assuming good ignition, dry fuels, and </div>
<div> winds less than about 15mph. </div>
<div> 2. Transport winds are a layer average through the mixing height, </div>
<div> weighted slightly toward the winds at the top of the layer. </div>
<div> 3. Ventilation Index is the height of the mixing layer times </div>
<div> the transport wind speed divided by 1000. </div>
<div> 4. Surface wind direction is the general expected wind direction. </div>
<div> At a specific point surface winds are highly dependent on </div>
<div> local terrain conditions.</div>
<div> </div>
<div>This forecast is provided under an agreement between the Oregon Department of</div>
<div>Agriculture and the Oregon Department of Forestry. For information contact ODA</div>
<div>at 503-986-4701.</div>
<div> </div>
<div> </div>
<div> </div>
<div> </div>
<div> </div>
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