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<div>SILVERTON HILLS FIELD BURNING FORECAST</div>
<div>OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE</div>
<div>9:00 AM PDT WED SEP 01 2010</div>
<div> </div>
<div>BURN ADVISORY:</div>
<div> </div>
<div> Recommended burn times for agricultural burning </div>
<div> are from 8:00am to 4:00pm.</div>
<div> Prep burning is not allowed. </div>
<div> Propane flaming is not allowed. </div>
<div> </div>
<div> </div>
<div>WEATHER DISCUSSION:</div>
<div> </div>
<div> A weakening Pacific cold front is moving through the region this morning. Valley</div>
<div> rainfall totals have generally been less than a tenth of an inch, but mountain</div>
<div> locations have received considerably more rain. Log Creek, near Mt Hood picked</div>
<div> up over 2.5 inches in the past 24 hours. Closer to home, Horse Creek, in the</div>
<div> Cascade foothills picked up .19 and Yellowstone Mountain recorded .62 inches.</div>
<div> Silverton had .04 in the rain guage, Jordan Valley recorded .12 and Turner picked</div>
<div> up .01 during the past 24 hours. </div>
<div> </div>
<div> Upper air charts show a ridge of high pressure aloft beginning to build off the</div>
<div> Oregon/Washington coast. This ridge will help to gradually decrease</div>
<div> precipitation during the day today. However skies should remain mostly cloudy</div>
<div> and relative humidities quite high for little drying of fields this afternoon. </div>
<div> </div>
<div> The ODF morning surface analysis showed the remains of the weak front trailing</div>
<div> southwestward from a minor surface low near Astoria. There is a well developed</div>
<div> thermal trough in California but it does not extend into Oregon. Gradients are</div>
<div> generally southerly and forecast models show a light southerly transport wind</div>
<div> today. </div>
<div> </div>
<div> For the mid Willamette Valley expect some light showers through the morning</div>
<div> hours, then mostly cloudy skies this afternoon. Salem's high temperature today</div>
<div> will be near 69, minimum relative humidity 59%.</div>
<div> </div>
<div> Sunset tonight: 7:43 pm </div>
<div> </div>
<div> </div>
<div>THREE-HOURLY DATA: </div>
<div> </div>
<div> 11am 2pm 5pm 8pm </div>
<div> Temperature: 63 67 69 65 </div>
<div> Relative Humidity: 81% 70% 59% 68% </div>
<div> Surface Wind Direction: 190 220 210 350 </div>
<div> Surface Wind Speed: 9 5 6 6 </div>
<div> Transport Wind Direction: 210 200 190 180 </div>
<div> Transport Wind Speed: 5 6 6 5 </div>
<div> Estimated Mixing Height: 1000 2500 2900 1000</div>
<div> Ventilation Index: 5 15 17 5</div>
<div> </div>
<div>EXTENDED DISCUSSION:</div>
<div> </div>
<div> Today marks the final surge of moisture into the Pacific Northwest for the next</div>
<div> couple of days. High pressure will quickly build offshore tonight and shift</div>
<div> inland later tomorrow for a quick warm-up. Temperatures tomorrow will jump on</div>
<div> the order of 15 degrees compared to today. At this point it appears that</div>
<div> transport wind directions will be unfavorable for burning Thursday and Friday. </div>
<div> </div>
<div> By late Friday the ridge over the region begins to shift east as another upper</div>
<div> level trough approaches from the Pacific. This should bring cooler weather to</div>
<div> the mid Willamette valley once again this weekend, although not as cool as the</div>
<div> past couple of days. There is a potential for some light rain over the weekend,</div>
<div> but moisture appears quite limited. Longer range models indicate a second trough</div>
<div> aproaching early next week.</div>
<div> </div>
<div>EXTENDED FORECAST:</div>
<div> </div>
<div> Thursday: Morning low clouds or fog, otherwisesunny. 85. N 5-10 mph. </div>
<div> Friday: Sunny, with a high near 87. N 5-10 g 15 mph. </div>
<div> Saturday: Partly sunny, with a high near 78. </div>
<div> Sunday: Partly sunny, with a high near 75. </div>
<div> Monday: Partly sunny, with a high near 75. </div>
<div> Tuesday: Partly sunny, with a high near 74. </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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