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<p class="MsoNoSpacing">SILVERTON HILLS FIELD BURNING FORECAST<o:p></o:p></p>
<p class="MsoNoSpacing">OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE<o:p></o:p></p>
<p class="MsoNoSpacing">11:45 AM PDT THU JUL 16, 2015<o:p></o:p></p>
<p class="MsoNoSpacing"><o:p> </o:p></p>
<p class="MsoNoSpacing"><b>BURN ADVISORY:<o:p></o:p></b></p>
<p class="MsoNoSpacing"><b><o:p> </o:p></b></p>
<p class="MsoNoSpacing">Agricultural burning is not recommended.<o:p></o:p></p>
<p class="MsoNoSpacing"><o:p> </o:p></p>
<p class="MsoNoSpacing">Prep burning is allowed from 12 p.m. to 2 p.m. with a 50 acre limit.<o:p></o:p></p>
<p class="MsoNoSpacing"><o:p> </o:p></p>
<p class="MsoNoSpacing"><b>WEATHER DISCUSSION:<o:p></o:p></b></p>
<p class="MsoNoSpacing"><o:p> </o:p></p>
<p class="MsoNoSpacing">Onshore flow aloft increases as a series of upper-level troughs move in from the Pacific Ocean. A surface ridge offshore Oregon will provide northerly flow throughout the Willamette Valley until it weakens mid-afternoon, allowing a mild
sea breeze front to approach from the northwest. Mixing conditions are well-developed within a deep marine layer, and will be maintained through sunset. Clouds over western Oregon are beginning to scatter as they enter the Cascades, allowing more heating to
take place. Gradients have improved slowly, with +1.6mb onshore from Newport to Salem and +3.5mb onshore from Salem to Redmond. Several hours of persistent heating will be required to overcome these conditions. This points towards a late day of burning opportunities
in the Silverton Hills, if all of these wrinkles can be ironed out. <o:p></o:p></p>
<p class="MsoNoSpacing"><o:p> </o:p></p>
<p class="MsoNoSpacing"><b>TODAY’S FORECAST:<o:p></o:p></b></p>
<p class="MsoNoSpacing"><o:p> </o:p></p>
<p class="MsoNoSpacing">Mostly Cloudy skies becoming Partly Cloudy this afternoon.
<o:p></o:p></p>
<p class="MsoNoSpacing"><o:p> </o:p></p>
<p class="MsoNoSpacing">Salem's high temperature today will be near 79°F (average is 83°F).<o:p></o:p></p>
<p class="MsoNoSpacing">Relative humidity: Currently near 45% and lowering to near 35% by 5 p.m. this afternoon.<o:p></o:p></p>
<p class="MsoNoSpacing">Surface winds: N-NW 10-15 mph this afternoon.<o:p></o:p></p>
<p class="MsoNoSpacing">Transport winds: NW 15-20 mph this afternoon.<o:p></o:p></p>
<p class="MsoNoSpacing">Mixing height: Currently 5000 ft and sustained above 5000 ft until sunset.<o:p></o:p></p>
<p class="MsoNoSpacing">Salem’s sunset tonight: 8:55 p.m.<o:p></o:p></p>
<p class="MsoNoSpacing"><o:p> </o:p></p>
<p class="MsoNoSpacing">(Salem Airport data for Wednesday, July 15th: High 85°F; Rainfall: .00”)<o:p></o:p></p>
<p class="MsoNoSpacing">(Maximum Ventilation Index expected today: 100)<o:p></o:p></p>
<p class="MsoNoSpacing">
<o:p></o:p></p>
<p class="MsoNoSpacing"><b>EXTENDED DISCUSSION:<o:p></o:p></b></p>
<p class="MsoNoSpacing"><o:p> </o:p></p>
<p class="MsoNoSpacing">Mild weather continues into Friday, as the upper-level ridge over the Pacific rebuilds, forcing an upper-level low over Canada further east. A surface ridge will shift into the Oregon coast, producing northerly flow across the Willamette
Valley while weakening onshore gradients. This points towards a lower probability of open burning opportunities, but limited prep burning may be possible. The atmosphere will begin a period of warming as it dries out over the weekend. There will be no rainfall
for this time as temperatures creep slightly above seasonal averages during the afternoon hours.<o:p></o:p></p>
<p class="MsoNoSpacing"><o:p> </o:p></p>
<p class="MsoNoSpacing">Late Sunday night, the upper-level ridge will weaken considerably as a trough from Alaska and remnants from Hurricane Dolores, near southern California, force it back out to sea. The surface ridge will weaken as a result, opening Oregon
to westerly flow at all levels. Persistent onshore flow appears to provide multiple days of favorable burning conditions next week.
<o:p></o:p></p>
<p class="MsoNoSpacing"><o:p> </o:p></p>
<p class="MsoNoSpacing">The National Weather Service’s digital forecast is available at:<o:p></o:p></p>
<p class="MsoNoSpacing"><a href="http://forecast.weather.gov/MapClick.php?lat=44.90549606158295&lon=-122.8106689453125&site=pqr&unit=0&lg=en&FcstType=text">http://forecast.weather.gov/MapClick.php?lat=44.90549606158295&lon=-122.8106689453125&site=pqr&unit=0&lg=en&FcstType=text</a><o:p></o:p></p>
<p class="MsoNoSpacing"><o:p> </o:p></p>
<p class="MsoNoSpacing">Notes:<o:p></o:p></p>
<p class="MsoNoSpacing">
<o:p></o:p></p>
<p class="MsoNoSpacing"> 1. Mixing height, as used here, is the lowest height at which the<o:p></o:p></p>
<p class="MsoNoSpacing"> potential temperature exceeds the potential temperature at the<o:p></o:p></p>
<p class="MsoNoSpacing"> surface. As a practical matter it is the approximate height to<o:p></o:p></p>
<p class="MsoNoSpacing"> which a smoke plume will rise assuming good ignition, dry fuels,<o:p></o:p></p>
<p class="MsoNoSpacing"> and winds less than about 15 mph.<o:p></o:p></p>
<p class="MsoNoSpacing">
<o:p></o:p></p>
<p class="MsoNoSpacing"> 2. Transport winds are a layer average through the mixing height,
<o:p></o:p></p>
<p class="MsoNoSpacing"> weighted slightly toward the winds at the top of the layer.<o:p></o:p></p>
<p class="MsoNoSpacing">
<o:p></o:p></p>
<p class="MsoNoSpacing"> 3. Ventilation Index is the height of the mixing layer (ft) times
<o:p></o:p></p>
<p class="MsoNoSpacing"> the transport wind speed (mph) divided by 1000.<o:p></o:p></p>
<p class="MsoNoSpacing">
<o:p></o:p></p>
<p class="MsoNoSpacing"> 4. Surface wind direction is the general expected wind direction.
<o:p></o:p></p>
<p class="MsoNoSpacing"> At a specific point surface winds are highly dependent on local<o:p></o:p></p>
<p class="MsoNoSpacing"> terrain conditions.<o:p></o:p></p>
<p class="MsoNoSpacing"><o:p> </o:p></p>
<p class="MsoNoSpacing">This forecast is provided under an agreement between the Oregon Department<o:p></o:p></p>
<p class="MsoNoSpacing">of Agriculture (ODA) and the Oregon Department of Forestry (ODF). For<o:p></o:p></p>
<p class="MsoNoSpacing">information contact ODA at 503-986-4701.<o:p></o:p></p>
<p class="MsoNoSpacing"><o:p> </o:p></p>
<p class="MsoNoSpacing"><b>To add/remove your email address from this list, please go to:<o:p></o:p></b></p>
<p class="MsoNoSpacing"><o:p> </o:p></p>
<p class="MsoNoSpacing"><a href="http://listsmart.osl.state.or.us/mailman/listinfo/willamette-fcst">http://listsmart.osl.state.or.us/mailman/listinfo/willamette-fcst</a><o:p></o:p></p>
<p class="MsoNoSpacing"><o:p> </o:p></p>
<p class="MsoNoSpacing">Tom Jenkins<o:p></o:p></p>
<p class="MsoNoSpacing">ODF Meteorologist<o:p></o:p></p>
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