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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link=blue vlink=purple><div class=WordSection1><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>11:55 AM PDT FRI AUG 10, 2012<o:p></o:p></p><p class=MsoNoSpacing><o:p> </o:p></p><p class=MsoNoSpacing>BURN ADVISORY:<o:p></o:p></p><p class=MsoNoSpacing><o:p> </o:p></p><p class=MsoNoSpacing>Agricultural burning is not recommended.<o:p></o:p></p><p class=MsoNoSpacing>Prep burning is allowed from noon until 2 p.m. with a 50 acre limit. <o:p></o:p></p><p class=MsoNoSpacing>Propane flaming is allowed from noon until 5 p.m. <o:p></o:p></p><p class=MsoNoSpacing> <o:p></o:p></p><p class=MsoNoSpacing>WEATHER DISCUSSION:<o:p></o:p></p><p class=MsoNoSpacing><o:p> </o:p></p><p class=MsoNoSpacing>The weak upper-level trough that moved onshore this morning was pushing into central Oregon at midday. A reinforced marine layer, across western Oregon, is making for a slow break-up of the morning clouds, especially along the western foothills of the Cascades. Expect sunny skies by mid-afternoon.<o:p></o:p></p><p class=MsoNoSpacing><o:p> </o:p></p><p class=MsoNoSpacing>Moderate gradient stacking, which is not conducive to good smoke ventilation from the valley, may get balanced out by afternoon heating. However, transport winds are forecast to remain northerly and a bit brisk. Pibals are scheduled to begin at 2 p.m., to verify the forecast of northerly winds. An unlikely shift to northwesterly winds would be more favorable for burning. <o:p></o:p></p><p class=MsoNoSpacing><o:p> </o:p></p><p class=MsoNoSpacing>TODAY’S FORECAST:<o:p></o:p></p><p class=MsoNoSpacing><o:p> </o:p></p><p class=MsoNoSpacing>Turning sunny this afternoon. A little breezy.<o:p></o:p></p><p class=MsoNoSpacing><o:p> </o:p></p><p class=MsoNoSpacing>Salem's high temperature today will be near 82 degrees (normal is 83).<o:p></o:p></p><p class=MsoNoSpacing>Relative humidity drops to 50% by 2 p.m. and to near 40% by 5 p.m.<o:p></o:p></p><p class=MsoNoSpacing>Surface winds: N 8-13 mph this afternoon.<o:p></o:p></p><p class=MsoNoSpacing>Transport winds: N 12-18 mph this afternoon.<o:p></o:p></p><p class=MsoNoSpacing>Mixing height: Rising to 4500 feet by 5 p.m.<o:p></o:p></p><p class=MsoNoSpacing>Salem’s sunset tonight: 8:25 p.m. <o:p></o:p></p><p class=MsoNoSpacing> <o:p></o:p></p><p class=MsoNoSpacing>THREE-HOURLY DATA: <o:p></o:p></p><p class=MsoNoSpacing> 2 p.m. 5 p.m. 8 p.m. <o:p></o:p></p><p class=MsoNoSpacing> Temperature: 76 82 74 <o:p></o:p></p><p class=MsoNoSpacing> Relative Humidity: 47% 38% 50%<o:p></o:p></p><p class=MsoNoSpacing> Surface Wind Dir/Speed: N 10 N 12 NW 12<o:p></o:p></p><p class=MsoNoSpacing> Transport Wind Dir/Speed: N 14 N 16 N 18<o:p></o:p></p><p class=MsoNoSpacing> Mixing Height: 3800 4500 2500<o:p></o:p></p><p class=MsoNoSpacing> Ventilation Index: 53 72 45 <o:p></o:p></p><p class=MsoNoSpacing> <o:p></o:p></p><p class=MsoNoSpacing>EXTENDED DISCUSSION:<o:p></o:p></p><p class=MsoNoSpacing><o:p> </o:p></p><p class=MsoNoSpacing>A warm-up is expected this weekend, as an upper-level ridge builds over the region. Sunshine and offshore flow will likely push valley highs into the 90s. A very weak upper-level trough is forecast flatten the ridge Monday and Tuesday; turning the low-level flow onshore and possibly creating favorable burning conditions. Temperatures will likely cool back to normal by Tuesday.<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, and <o:p></o:p></p><p class=MsoNoSpacing> winds less than about 15mph.<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 times <o:p></o:p></p><p class=MsoNoSpacing> the transport wind speed 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 of<o:p></o:p></p><p class=MsoNoSpacing>Agriculture and the Oregon Department of Forestry. For information contact ODA at 503-986-4701.<o:p></o:p></p><p class=MsoNoSpacing><o:p> </o:p></p><p class=MsoNoSpacing>Pete Parsons<o:p></o:p></p><p class=MsoNoSpacing>ODF Meteorologist<o:p></o:p></p></div></body></html>