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<div>SILVERTON HILLS FIELD BURNING FORECAST</div>
<div>OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE</div>
<div>9:00 AM PDT FRI AUG 27 2010</div>
<div> </div>
<div>BURN ADVISORY:</div>
<div> </div>
<div> Recommended burn times for agricultural burning are from 11:00am to 6:00pm.</div>
<div> Prep burning is allowed from 11:00am to 4:00pm with a 50 acre limit. </div>
<div> Propane flaming is allowed from 11:00am to 5:00pm. </div>
<div> </div>
<div> </div>
<div>WEATHER DISCUSSION:</div>
<div> </div>
<div> Upper level trough is firmly entrenched over the state today with higher level</div>
<div> clouds over the region associated with the nearby jetstream. A disturbance will</div>
<div> rotate through the flow bringing increasing clouds later today and tonight.</div>
<div> Pressure gradients are rather flat this morning with the Newport to Salem</div>
<div> gradient at .3mb onshore and Salem to Redmond .9mb onshore. With modest heating</div>
<div> this afternoon pressure gradients should increase a little faster over the Coast</div>
<div> Range than the Cascades. However, the Medford draw will be prevalent and keep</div>
<div> winds fairly northerly today. </div>
<div> </div>
<div> Morning sounding showed a minor stable layer near the surface up to about 1000</div>
<div> ft. This will mix out with daytime heating. Mixing levels will rise nicely today</div>
<div> with the mixing height above 4000 ft by 11 a.m. and above 5000 ft around noon.</div>
<div> Low-level winds are rather variable up about 1500 ft then turn N to NE at 5 to</div>
<div> 10 mph. </div>
<div> </div>
<div> Expect partly to mostly cloudy skies today. High temperature will rise to near</div>
<div> 70. Relative humidity drops below 50% by 1 p.m. with the minimum near 40%. Wind</div>
<div> flow will be light this morning, becoming NW to N at 6 - 10 mph. Will have</div>
<div> release pibals to see whether enough NW'erly flow can be "squeezed out" for a</div>
<div> decent burning opportunity.</div>
<div> </div>
<div> Sunset tonight: 7:52 pm </div>
<div> </div>
<div> </div>
<div>THREE-HOURLY DATA: </div>
<div> </div>
<div> 11am 2pm 5pm 8pm </div>
<div> Temperature: 61 68 71 65 </div>
<div> Relative Humidity: 62% 42% 35% 50% </div>
<div> Surface Wind Direction: 360 340 340 310 </div>
<div> Surface Wind Speed: 5 6 8 7 </div>
<div> Transport Wind Direction: 350 340 340 350 </div>
<div> Transport Wind Speed: 7 10 11 12 </div>
<div> Estimated Mixing Height: 4500 5500 6000 4000</div>
<div> Ventilation Index: 32 55 66 48</div>
<div> </div>
<div> </div>
<div> </div>
<div>EXTENDED DISCUSSION:</div>
<div> </div>
<div> Upper level trough deepens tonight as a disturbance moves into the</div>
<div> state overnight. This quite possibly could produce some light rain over the</div>
<div> region on Saturday, mainly to the south. Pressure gradients will be light</div>
<div> northerly early, then turn more onshore during the day with NW'erly flow by mid</div>
<div> to late afternoon. Temperatures will remain cool under mostly cloudy skies and</div>
<div> may not reach 70.</div>
<div> </div>
<div> Upper trough moves off to the east Sunday but skies will remain cloudy and</div>
<div> temperatures cool. Wind flow turns more westerly. Another disturbance will ride</div>
<div> down the back side of the trough later Sunday and Monday and bring another</div>
<div> chance of some light rain. Wind flow will be SW'erly on Monday. Trough moves</div>
<div> off to the east Tuesday and Wednesday with a flat ridge moving in. Temperatures</div>
<div> will warm and the air mass will dry out.</div>
<div> </div>
<div> </div>
<div>EXTENDED FORECAST: </div>
<div> </div>
<div> Saturday: Mostly cloudy, with a high near 69. Calm wind becoming NW'erly</div>
<div> between 8 and 11 mph. </div>
<div> Saturday Night: Mostly cloudy, with a low around 48. NW'erly wind</div>
<div> between 8 and 11 mph becoming calm. </div>
<div> Sunday: Mostly cloudy, with a high near 68. Calm wind becoming westerly</div>
<div> between 5 and 10 mph. </div>
<div> Sunday Night: Mostly cloudy, with a low around 47. </div>
<div> Monday: A 30 percent chance of showers. Mostly cloudy, with a high</div>
<div> near 67. </div>
<div> Monday Night: A chance of showers. Mostly cloudy, with a low around 49. </div>
<div> Tuesday: Partly sunny, with a high near 74. </div>
<div> Tuesday Night: Mostly cloudy, with a low around 50. </div>
<div> Wednesday Night: Partly cloudy, with a low around 52. </div>
<div> Thursday: Mostly sunny, with a high near 82. </div>
<div> </div>
<div> </div>
<div> </div>
<div> </div>
<div> </div>
<div> </div>
<div> </div>
<div> </div>
<div> </div>
<div> </div>
<div> </div>
<div> </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><font face="Calibri, sans-serif" size="2"> </font></div>
<div><font face="Calibri, sans-serif" size="2"> </font></div>
<div><font face="Arial, sans-serif"><i>Nick Yonker</i></font></div>
<div><font face="Arial, sans-serif"><i>Meteorology Manager</i></font></div>
<div><font face="Arial, sans-serif"><i>Oregon Department of Forestry</i></font></div>
<div><font face="Arial, sans-serif"><i>503-945-7451</i></font></div>
<div><font face="Calibri, sans-serif" size="2"> </font></div>
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