<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>9:00 AM PDT MON AUG 23 2010</div>
<div> </div>
<div>BURN ADVISORY:</div>
<div> </div>
<div> Recommended burn times for agricultural burning are from 12:00pm 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 moving east over eastern Oregon this morning</div>
<div> with an upper ridge of high pressure building off the coast. The morning ODF</div>
<div> surface analysis shows a thermal trough from central California extending</div>
<div> northwestward to the SW Oregon coast. Weak surface high pressure covers the</div>
<div> Puget Sound region.</div>
<div> </div>
<div> Satellite pictures showed nearly cloud-free skies over Oregon with just a</div>
<div> few low clouds banked up against the lower west slopes of the Cascades from</div>
<div> Multnomah County southward to Marion County. These should dissipate quickly.</div>
<div> </div>
<div> The morning Salem sounding showed the atmosphere had warmed considerable above</div>
<div> about 4000 feet since yesterday, with models showing additional warming</div>
<div> throughout the day today. This will stabililze the atmosphere and suppress</div>
<div> mixing heights. The maximum mixing height today in the mid-Willamette</div>
<div> Valley will likely not reach 3000 feet. Winds on the sounding were northeasterly</div>
<div> to about 4000 feet, then northerly and finally north-northwesterly above about</div>
<div> 8000 feet. </div>
<div> </div>
<div> As of 8am this morning there was a 0.9mb offshore gradient Redmond to Newport</div>
<div> and the Portland to Medford gradient was northerly at 3.8mb. The offshore flow</div>
<div> should increase this afternoon. </div>
<div> </div>
<div> Temperatures this morning were running 2-3 degrees cooler than yesterday</div>
<div> morning, but by this afternoon high temperatures should be 6-8 degrees warmer</div>
<div> than they were yesterday at the same time. </div>
<div> </div>
<div> With the low mixing heights and northeasterly transport winds today, there will</div>
<div> likely be no open field burning this afternoon. </div>
<div> </div>
<div> Salem's high temperature today will be near 83. Relative humidity drops to 50%</div>
<div> by 11am. Minimum relative humidity 24%.</div>
<div> </div>
<div> Sunset tonight: 7:59 pm</div>
<div> </div>
<div> </div>
<div>THREE-HOURLY DATA: </div>
<div> </div>
<div> 11am 2pm 5pm 8pm </div>
<div> Temperature: 67 77 83 77 </div>
<div> Relative Humidity: 52% 33% 24% 32% </div>
<div> Surface Wind Direction: 360 360 010 010 </div>
<div> Surface Wind Speed: 5 8 12 6 </div>
<div> Transport Wind Direction: 010 010 010 010 </div>
<div> Transport Wind Speed: 7 11 12 5 </div>
<div> Estimated Mixing Height: 1500 2700 2800 500</div>
<div> Ventilation Index: 10 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 winds.</div>
<div> Temperatures will be around 10-12 degrees warmer than today. Burning is not</div>
<div> 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 marine push ends the minor warm spell. Timing is the key. If</div>
<div> the marine push comes in too late there will be no burn opportunity. Models are</div>
<div> inconsistent on the onset of westerly flow in the Valley some showing a burn</div>
<div> possibility by mid-afternoon, others holding off the push until the evening, too</div>
<div> late for burning. </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>