[willamette-fcst] Silverton Hills Forecast - Wed, Jul 14 2010

[Willamette Valley Ag/Burning Forecast]

SILVERTON HILLS FIELD BURNING FORECAST
OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE
12:00 PM PDT WED JUL 14 2010

BURN ADVISORY:

     Recommended burn times for agricultural burning are now up until to 7:00pm.
     Prep burning is allowed up until 5:00pm with a 50 acre limit. 
     Propane flaming is allowed up until to 5:00pm.	
									
										
WEATHER DISCUSSION:

     As of 11am temperatures are running 5 to 7 degrees warmer than yesterday at 
     the same time in the Willamette Valley.  Bright sunshine and a high sun 
     angle should easily push temperatures into the mid 80's this afternoon.  
     The late morning ODF surface analysis shows a thermal trough in the 
     central valley of California with weak high pressure to the north over the 
     Puget Sound.  The west to east gradient (Newport to Redmond) is nearly flat.  The 
     north to south gradient (Portland to Medford) has dropped to about 3.5mb but
     is still enough to keep surface and transport winds northerly through the
     Willamette Valley.  The latest trajectory forecast from the RUC model continue to
     show any smoke from the Silverton Hills headed toward Eugene and central Lane
     County.  

     Expect total sunshine this afternoon in the central Willamette Valley.  Salem's
     high temperature today will be near 84 and the minimum relative humidity will be
     about 27%.  Winds will be northerly about 8-12mph.  

     Sunset tonight for Salem: 8:51 pm	
							
										
THREE-HOURLY DATA:		

                                     2pm     5pm     8pm			
     Temperature:                     78      84      80  			
     Relative Humidity:               34%     27%     35%     			
     Surface Wind Direction:         360     360     360 		
     Surface Wind Speed:               9      12       9    			
     Transport Wind Direction:       360     360     360 
     Transport Wind Speed:            10      15       6  
     Estimated Mixing Height:       4700    5000    1000
     Ventilation Index:               47      75       6

                               				
										
EXTENDED DISCUSSION:

     The Pacific Northwest is in a fairly normal summertime weather pattern and no
     extremes of weather are likely for the next few days.  Upper air charts show a 
     broad flat ridge today, a zonal or west-to-east flow aloft tomorrow, and a broad
     shallow trough Friday.  None of these features will have much effect on Willamette
     Valley weather other than to produce sunny skies and temperatures near or above
     average.  Maximum mixing heights will gradually lower during the rest of the week
     but should remain fairly high.  There are still indications of a more westerly
     transport flow next Monday.  Next week looks cooler with an upper level 
     trough developing over the region.



EXTENDED FORECAST:	

     Thursday: Sunny, with a high near 88. Winds calm becoming N 7-10 mph. . 
     Friday: Sunny, with a high near 83. NNW 5-15 and gusty.   
     Saturday: Mostly sunny, 85.   
     Sunday: Sunny, 82.  
     Monday: Mostly sunny, 80.  
     Tuesday: Sunny, 81.  
										
Notes:									
     1.  Mixing height, as used here, is the lowest height at which the
         potential temperature exceeds the potential temperature at the surface.  
         As a practical matter it is the approximate height to which a 
         smoke plume will rise assuming good ignition, dry fuels, and 
         winds less than about 15mph.								
     2.  Transport winds are a layer average through the mixing height, 
         weighted slightly toward the winds at the top of the layer.								
     3.  Ventilation Index is the height of the mixing layer times 
         the transport wind speed divided by 1000.								
     4.  Surface wind direction is the general expected wind direction.  
         At a specific point surface winds are highly dependent on 
         local terrain conditions.	

											
This forecast is provided under an agreement between the Oregon Department of
Agriculture and the Oregon Department of Forestry.  For information contact ODA
at 503-986-4701.