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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 THU AUG 12 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> Recommended burn times for agricultural burning are
from 1:00pm<o:p></o:p></p>
<p class=MsoNormal> to 6:30pm.<o:p></o:p></p>
<p class=MsoNormal> Prep burning is allowed from 1:00pm to 5:00pm with a 50
acre limit. <o:p></o:p></p>
<p class=MsoNormal> Propane flaming is allowed from 1:00pm 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>An upper-level ridge is building just offshore with a dry
north-northwesterly flow aloft over western Oregon. The onshore flow is very
weak this morning with satellite imagery showing low clouds only along the
coast and in the extreme northern Willamette Valley. The Salem sounding showed
several degrees of warming, since 24 hours ago, from just above the surface up
through 10,000 feet, so high temperatures will be much warmer today. Forecast
light northerly transport winds makes open burning highly unlikely 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>Sunny and warmer. After reaching 81 degrees on Wednesday,
Salem's high temperature today will be near 87 degrees. The mixing height will
climb to 3000 feet about 2 p.m. and likely top out near 3700 feet around 5
p.m. An evening sea breeze should drop the mixing height to near 1500 feet by
shortly before sunset. Surface and transport winds will be light northerly
this morning, increase to 5-10 mph later this afternoon, then turn NW 5-10 mph
this evening. Relative humidity will drop to 50% by noon and to near 30% around
5 p.m. The ventilation index will climb to only 22 this afternoon.<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Silverton area sunset tonight: 8:17 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: 70 81 87
78 <o:p></o:p></p>
<p class=MsoNormal> Relative Humidity: 55% 38% 30%
42% <o:p></o:p></p>
<p class=MsoNormal> Surface Wind Direction: 360 350 340
290 <o:p></o:p></p>
<p class=MsoNormal> Surface Wind Speed: 2 4 5
6 <o:p></o:p></p>
<p class=MsoNormal> Transport Wind Direction: 360 360 360
320 <o:p></o:p></p>
<p class=MsoNormal> Transport Wind Speed: 3 5 6
8 <o:p></o:p></p>
<p class=MsoNormal> Estimated Mixing Height: 1900 3000 3700
1500<o:p></o:p></p>
<p class=MsoNormal> Ventilation Index: 6 15 22
12<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>A strong upper-level ridge of high pressure will build over
the Pacific Northwest Friday through Monday with mostly clear skies and dry
offshore flow boosting high temperatures to near record values. The ridge is
forecast to shift east of the region during the middle of next week with the
surface flow turning back onshore. That will cool temperatures back closer to
normal by Wednesday and could create open burning opportunities. A strong
enough trough may come onshore by late Wednesday or Thursday to produce showers
or thundershowers in the Willamette Valley with temperatures falling to below
normal. <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>Friday: Sunny and very warm. NE wind 5-15 mph. 55/93<o:p></o:p></p>
<p class=MsoNormal>Saturday: Sunny with near-record warmth. NE wind 5-10 mph.
58/97<o:p></o:p></p>
<p class=MsoNormal>Sunday: Sunny with near-record warmth. Light wind. 59/98<o:p></o:p></p>
<p class=MsoNormal>Monday: Sunny with near-record warmth. Light wind. 61/99<o:p></o:p></p>
<p class=MsoNormal>Tuesday: Sunny. A little cooler. Wind becoming W 5-15 mph.
61/94<o:p></o:p></p>
<p class=MsoNormal>Wednesday: Partly cloudy and cooler. Wind W 5-15 mph. 56/84<o:p></o:p></p>
<p class=MsoNormal>Thursday: Mostly cloudy and cooler. Chance of showers.
54/75 <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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