<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=us-ascii">
<meta name="Generator" content="Microsoft Exchange Server">
<!-- converted from rtf -->
<style><!-- .EmailQuote { margin-left: 1pt; padding-left: 4pt; border-left: #800000 2px solid; } --></style>
</head>
<body>
<font face="Courier New, monospace" size="2">
<div>SILVERTON HILLS FIELD BURNING FORECAST</div>
<div>OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE</div>
<div>12:00 PM PDT MON AUG 23 2010</div>
<div> </div>
<div>BURN ADVISORY:</div>
<div> </div>
<div> Recommended burn times for agricultural burning are from Noon to 6:00pm.</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> Upper air charts show a cool trough to the east of the state and moving east</div>
<div> away from the region. An upper ridge of high pressure is building off the coast.</div>
<div> The late morning ODF surface analysis shows a thermal trough from central</div>
<div> California extending northwestward to just off the SW Oregon coast. Weak surface</div>
<div> high pressure covers the Puget Sound region. </div>
<div> </div>
<div> As of 11am there was a .4mb offshore gradient Redmond to Newport and the</div>
<div> Portland to Medford gradient had increased to 5.3mb. </div>
<div> </div>
<div> Satellite pictures show clear skies over the entire state. The morning Salem</div>
<div> sounding showed the atmosphere had warmed considerable above about 4000 feet</div>
<div> since yesterday, and models are showing additional warming throughout the day</div>
<div> today. This will stabilize the atmosphere and suppress mixing heights. The</div>
<div> maximum mixing height today in the mid-Willamette Valley will likely not reach</div>
<div> 3000 feet. </div>
<div> </div>
<div> The morning sounding showed northeasterly transport winds and computer models</div>
<div> continue to show that pattern through the afternoon and evening. Late morning</div>
<div> temperatures were running fairly close to where they were yesterday at the same</div>
<div> time, but high temperatures today should be 6-8 degrees warmer than yesterday.</div>
<div> With the low mixing heights and northeasterly transport winds today, there will</div>
<div> likely be no open field burning this afternoon. Salem's high temperature today</div>
<div> will be near 83. Minimum relative humidity today: 24%. Sunset tonight: 7:59 pm</div>
<div> </div>
<div> </div>
<div>THREE-HOURLY DATA: </div>
<div> </div>
<div> 2pm 5pm 8pm </div>
<div> Temperature: 74 81 75 </div>
<div> Relative Humidity: 36% 25% 33% </div>
<div> Surface Wind Direction: 360 010 020 </div>
<div> Surface Wind Speed: 10 13 7 </div>
<div> Transport Wind Direction: 010 010 010 </div>
<div> Transport Wind Speed: 11 12 5 </div>
<div> Estimated Mixing Height: 2700 2800 500</div>
<div> Ventilation Index: 30 34 2</div>
<div> </div>
<div>EXTENDED DISCUSSION:</div>
<div> </div>
<div> The upper level ridge off the coast this morning will strengthen and move over</div>
<div> the Oregon and Washington tomorrow for hot weather and gusty, dry offshore</div>
<div> winds. Temperatures will be around 10-12 degrees warmer than today. Burning is</div>
<div> not likely Tuesday. </div>
<div> </div>
<div> The next opportunity for open field burning may be Wednesday as the upper ridge</div>
<div> axis moves east and a marine push ends the minor warm spell. Timing is the key.</div>
<div> Both the GFS and the RUC models show this as a late afternoon event which would</div>
<div> allow for some burning. However this event is far enough in the future that we</div>
<div> have little confidence in the exact timing of the onset of westerly, burnable</div>
<div> winds. </div>
<div> </div>
<div> Thursday will be the first day after a marine push, which usually means low</div>
<div> mixing heights and gradient stacking (subsidence aloft) to the east and thus not</div>
<div> likely a good burn day. Friday will be partly sunny and the GFS model shows an</div>
<div> unfavorable northerly transport flow over the region.</div>
<div> </div>
<div> </div>
<div>EXTENDED FORECAST: </div>
<div> </div>
<div> Tuesday: Sunny, with a high near 94. Wind ENE 5-15, gusts to 20.</div>
<div> Wednesday: Sunny, with a high near 91. E 10mph becoming NNW, possibly WNW late. </div>
<div> Thursday: Partly sunny but chance of sprilkles. Hihg 78. </div>
<div> (First day after a marine push) </div>
<div> Friday: Partly sunny, 72. </div>
<div> Saturday: Mostly cloudy, 72. </div>
<div> Sunday: Mostly cloudy, chance of showers. High 68. </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>
<div><font face="Calibri, sans-serif" size="2"> </font></div>
<div><font face="Calibri, sans-serif" size="2"> </font></div>
</font>
</body>
</html>