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<p class=MsoNormal>SILVERTON HILLS FIELD BURNING FORECAST<o:p></o:p></p>
<p class=MsoNormal>OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE<o:p></o:p></p>
<p class=MsoNormal>9:00 AM PDT FRI JUL 30 2010<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>BURN ADVISORY:<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal> Agricultural burning is not recommended.<o:p></o:p></p>
<p class=MsoNormal> Prep burning is not allowed. <o:p></o:p></p>
<p class=MsoNormal> Propane flaming is allowed from 2:00 p.m. until 5:00
p.m. <o:p></o:p></p>
<p class=MsoNormal> <o:p></o:p></p>
<p class=MsoNormal>WEATHER DISCUSSION:<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>A weak upper-level trough, just offshore, will bring
south-southwesterly flow aloft to Oregon again today. Weak onshore flow
brought marine low clouds onto the coastline again this morning, with some
penetration into the extreme northern Willamette Valley. Otherwise, skies were
mostly sunny again this morning with light winds.<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>The Salem sounding this morning was similar to yesterday
morning with a very stable atmosphere extending from the surface to about 8000
feet. That will retard the daily rise in mixing heights again today. The
offshore trough is forecast to begin moving onshore sounding from Salem surface
map shows weak but even onshore later this afternoon. That should increase the
onshore flow and may turn transport winds enough northwesterly to provide an
open burning opportunity. Pressure gradients are forecast to be favorable for
maintaining lift. However, afternoon thunderstorm development is possible
along the Cascades and will need to be closely watched.<o:p></o:p></p>
<p class=MsoNormal> <o:p></o:p></p>
<p class=MsoNormal>TODAY’S FORECAST:<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Mostly sunny and warm. After reaching 85 degrees on
Thursday, Salem's high temperature today will be near 84 degrees. The mixing
height will not climb to 3000 feet until around 2 p.m. but will likely jump to
nearly 4500 feet, late this afternoon, before a cooling sea breeze quickly
drops it to around 1000 feet just before sunset. Surface and transport winds
will be NNW 3-7 this morning and back to NW 6-10 this afternoon. Relative
humidity will drop to 50% by noon and to near 32% by late this afternoon. The
ventilation index will be low through midday, before jumping to about 36 late
this afternoon.<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Silverton area sunset tonight: 8:35 pm <o:p></o:p></p>
<p class=MsoNormal> <o:p></o:p></p>
<p class=MsoNormal>THREE-HOURLY DATA: <o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal> 11am 2pm 5pm
8pm <o:p></o:p></p>
<p class=MsoNormal> Temperature: 69 78 84
73 <o:p></o:p></p>
<p class=MsoNormal> Relative Humidity: 52% 41% 32%
48% <o:p></o:p></p>
<p class=MsoNormal> Surface Wind Direction: 350 320 310
280 <o:p></o:p></p>
<p class=MsoNormal> Surface Wind Speed: 4 5 7
7 <o:p></o:p></p>
<p class=MsoNormal> Transport Wind Direction: 340 330 320
300 <o:p></o:p></p>
<p class=MsoNormal> Transport Wind Speed: 5 6 8
9 <o:p></o:p></p>
<p class=MsoNormal> Estimated Mixing Height: 1800 3000 4500
1000<o:p></o:p></p>
<p class=MsoNormal> Ventilation Index: 9 18 36
9 <o:p></o:p></p>
<p class=MsoNormal> <o:p></o:p></p>
<p class=MsoNormal>EXTENDED DISCUSSION:<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>The upper-level trough is forecast to move across Oregon
over the weekend with the flow aloft turning northwesterly by Sunday. That
will continue to bring onshore flow and near-normal temperatures to the
Willamette Valley. Another weak upper-level trough may move into the region
early next week, with little change in the overall weather conditions. Western
flow aloft and onshore low-level flow may provide multiple burning
opportunities next week. <o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>EXTENDED FORECAST: <o:p></o:p></p>
<p class=MsoNormal> <o:p></o:p></p>
<p class=MsoNormal>Saturday: Cloudy through mid morning, then gradual
clearing. High near 73. <o:p></o:p></p>
<p class=MsoNormal>Saturday Night: Partly cloudy, with a low around 50.<o:p></o:p></p>
<p class=MsoNormal>Sunday: Mostly sunny, with a high near 80.<o:p></o:p></p>
<p class=MsoNormal>Monday: Mostly sunny, with a high near 81. <o:p></o:p></p>
<p class=MsoNormal>Tuesday: Mostly sunny, with a high near 80. <o:p></o:p></p>
<p class=MsoNormal>Wednesday: Mostly sunny, with a high near 83. <o:p></o:p></p>
<p class=MsoNormal>Thursday: Mostly sunny, with a high near 82.<o:p></o:p></p>
<p class=MsoNormal> <o:p></o:p></p>
<p class=MsoNormal>Notes:<o:p></o:p></p>
<p class=MsoNormal> <o:p></o:p></p>
<p class=MsoNormal> 1. Mixing height, as used here, is the lowest height
at which the<o:p></o:p></p>
<p class=MsoNormal> potential temperature exceeds the potential
temperature at the<o:p></o:p></p>
<p class=MsoNormal> surface. <o:p></o:p></p>
<p class=MsoNormal> As a practical matter it is the approximate height
to which a <o:p></o:p></p>
<p class=MsoNormal> smoke plume will rise assuming good ignition, dry
fuels, and <o:p></o:p></p>
<p class=MsoNormal> winds less than about 15mph. <o:p></o:p></p>
<p class=MsoNormal> 2. Transport winds are a layer average through the
mixing height, <o:p></o:p></p>
<p class=MsoNormal> weighted slightly toward the winds at the top of
the layer. <o:p></o:p></p>
<p class=MsoNormal> 3. Ventilation Index is the height of the mixing layer
times <o:p></o:p></p>
<p class=MsoNormal> the transport wind speed divided by 1000. <o:p></o:p></p>
<p class=MsoNormal> 4. Surface wind direction is the general expected wind
direction. <o:p></o:p></p>
<p class=MsoNormal> At a specific point surface winds are highly
dependent on local<o:p></o:p></p>
<p class=MsoNormal> terrain conditions.<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>This forecast is provided under an agreement between the
Oregon Department of<o:p></o:p></p>
<p class=MsoNormal>Agriculture and the Oregon Department of Forestry. For
information contact ODA at 503-986-4701.<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Pete Parsons<o:p></o:p></p>
<p class=MsoNormal>ODF Meteorologist<o:p></o:p></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif"'><o:p> </o:p></span></p>
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