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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 TUE JUL 21, 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 not allowed.<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">An upper-level trough is approaching from northwest of Vancouver Island, and will be providing southwesterly onshore flow aloft all day. This will cause a surface ridge along the Oregon coast to weaken and move further south, with onshore
flow becoming northwesterly by mid-day. Morning clouds have broken up, allowing more heating to occur and mixing conditions to begin improving. Gradients are currently +0.6mb onshore from Newport to Salem, and +4.6mb from Salem to Redmond. Open burning opportunities
may develop today, but all indications point towards this event being a later afternoon window for field burning. A moderate sea breeze will move in to the Silverton Hills after sunset, bringing cool, marine air Tuesday evening.<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">Partly Cloudy and breezy this evening. <o:p></o:p></p>
<p class="MsoNoSpacing"><o:p> </o:p></p>
<p class="MsoNoSpacing">Salem's high temperature today will be near 78°F (average is 83°F).<o:p></o:p></p>
<p class="MsoNoSpacing">Relative humidity: Currently near 55% and lowering to near 35% by 4 p.m.<o:p></o:p></p>
<p class="MsoNoSpacing">Surface winds: 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 near 3500 feet and rising to 5000 feet by 2 p.m.<o:p></o:p></p>
<p class="MsoNoSpacing">Salem’s sunset tonight: 8:51 p.m.<o:p></o:p></p>
<p class="MsoNoSpacing"><o:p> </o:p></p>
<p class="MsoNoSpacing">(Salem Airport data for Monday, July 20th: High 89°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">A deep marine layer will be in place over the Willamette Valley on Wednesday, bringing more clouds in from the Pacific Ocean. A mid-level trough will sweep across northern Oregon Wednesday morning, helping to break up morning clouds
and allow heating to increase, improving mixing conditions under northwesterly onshore flow. Moisture carried over the Cascades will help form afternoon pop-up clouds along the ridgeline, with isolated showers further east Wednesday afternoon. These conditions
may provide a window for open burning opportunities earlier in the day if gradients improve quickly.<o:p></o:p></p>
<p class="MsoNoSpacing"><o:p> </o:p></p>
<p class="MsoNoSpacing">Thursday marks a brief period of stable weather, as an upper-level ridge moves in from the Pacific Ocean. This will help to dry out the atmosphere, but will limit mixing conditions while onshore flow weakens. A surface ridge will begin
to form near the Oregon coast that will also stack gradients unfavorably for open burning operations. Friday will see conditions become more favorable again, as a strong upper-level trough cruises down the Canadian coastline, weakening the upper-level ridge
in the Pacific Ocean. Onshore flow aloft increases, as straight westerly winds develop at all levels. The surface ridge near the Oregon coast will be pushed south, increasing onshore flow with west-by-northwesterly winds. Mixing conditions will improve, as
well as gradients, to provide another possible open burning opportunity ahead of the weekend.<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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