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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 MON AUG 2 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 burning is not recommended.<o:p></o:p></p>
<p class=MsoNormal> Prep burning is allowed from 12:00pm to 2:00pm with a
50 acre limit. <o:p></o:p></p>
<p class=MsoNormal> Propane flaming is allowed from 12:00pm to 5:00pm. <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 remains over the Pacific Northwest
this morning. Visible satellite imagery shows a band of what appears to be
elevated wild fire smoke extending from eastern and central Washington back
across northwestern Oregon, in association with an upper-level disturbance
moving through the region. Marine low clouds were blanketing the coast, but
inland penetration was limited to the extreme northern Willamette Valley, near
Portland. There were also patches of light fog in the extreme south valley,
near Eugene. Skies were mostly sunny over the remainder of the state.<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>The Salem sounding showed several degrees of warming aloft,
since Sunday morning. The marine air was very shallow with quite dry
conditions above 2500 feet. The low-level temperature profile is stable, with
a temperature inversion at about 4700 feet that should cap maximum mixing
heights this afternoon.<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>The weak upper-level disturbance that is over northwestern
Oregon this morning is forecast to continue eastward into central Oregon this
afternoon. Northwesterly flow aloft should promote an afternoon sea breeze.
Transport winds and pressure gradients will need to be monitored for the
possibility of limited open burning later this afternoon.<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>Smoke and haze aloft this morning, otherwise mostly sunny.
After reaching 80 degrees on Sunday, Salem's high temperature today will be
near 84 degrees. The mixing height will climb to 3000 feet about noon and
likely top out at around 4700 feet later this afternoon. A cooling sea breeze
will drop the mixing height to 1500 feet by shortly before sunset. Surface and
transport winds will be N 3-6 this morning and back to NW 6-10 this afternoon.
Relative humidity will drop to 50% by 1 p.m. and to near 36% by late this
afternoon. The ventilation index will climb 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: 8:32 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: 71 79 84
75 <o:p></o:p></p>
<p class=MsoNormal> Relative Humidity: 57% 44% 36% 50%
<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: 360 310 330
290 <o:p></o:p></p>
<p class=MsoNormal> Transport Wind Speed: 5 6 8
15 <o:p></o:p></p>
<p class=MsoNormal> Estimated Mixing Height: 2400 3800 4700
1500<o:p></o:p></p>
<p class=MsoNormal> Ventilation Index: 12 23 38
22 <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>Little change to the overall weather pattern is expected
through Friday, with a weak upper-level trough remaining over the Pacific
Northwest. Varying degrees of onshore flow will maintain at least a chance of
open burning each afternoon. The onshore flow may weaken a bit on Wednesday,
as the upper-level flow turns southwesterly, and then strengthen again late
Thursday and Friday. The best chances for open burning opportunities appear to
be Tuesday and Thursday afternoons, but that is certainly subject to change. <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>Tuesday: Patchy morning clouds, then mostly sunny. Wind: NW
5-12 mph. 55/84 <o:p></o:p></p>
<p class=MsoNormal>Wednesday: Mostly Sunny. Wind: NNW 5-12 mph. 55/86 <o:p></o:p></p>
<p class=MsoNormal>Thursday: Mostly sunny. Wind: NW 5-15 mph. 56/84<o:p></o:p></p>
<p class=MsoNormal>Friday: Morning clouds, then mostly sunny. 55/79 <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>
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