OPEN BURNING ANNOUNCEMENT MODEL GUIDANCE
800 PM PDT SUN AUG 23 2026
    NBM model output for: Portland KPDX  45.59N, -122.59W 
          Model Run Time:  2026-08-24 02Z

                             Mixing      Sfc     Transport                                 
                   Time      Height     Winds      Winds   Ventilation                    
  Day   Date      (PDT)     (ft MSL)    (mph)      (mph)      Index       Remarks         
  === ========   ========   =======    =======    =======    =======      =======         
  Sun Aug 23rd    8:00 pm     1000     330/08     350/12       12        
  Sun Aug 23rd    9:00 pm      500     330/08     350/10        5        
  Sun Aug 23rd   10:00 pm      500     320/08     350/10        5        
  Sun Aug 23rd   11:00 pm      600     320/08     350/09        6        

  Mon Aug 24th   12:00 am      500     330/08     350/08        4        
  Mon Aug 24th    1:00 am      400     330/08     350/08        3        
  Mon Aug 24th    2:00 am      400     330/07     350/07        3        
  Mon Aug 24th    3:00 am      400     330/07     340/07        3        
  Mon Aug 24th    4:00 am      400     330/07     350/07        3        
  Mon Aug 24th    5:00 am      400     340/07     360/07        3        
  Mon Aug 24th    6:00 am      400     330/07     360/07        3        
  Mon Aug 24th    7:00 am      400     340/07     010/07        3        
  Mon Aug 24th    8:00 am      600     340/07     010/07        4        
  Mon Aug 24th    9:00 am      800     340/07     050/07        6        
  Mon Aug 24th   10:00 am     1400     010/08     080/12       16        
  Mon Aug 24th   11:00 am     2300     050/08     080/13       29        
  Mon Aug 24th   12:00 pm     2700     060/09     090/13       34        
  Mon Aug 24th    1:00 pm     3400     060/09     090/12       39        Criteria Met
  Mon Aug 24th    2:00 pm     4100     060/09     090/10       42        Criteria Met
  Mon Aug 24th    3:00 pm     4200     050/08     090/09       39        Criteria Met
  Mon Aug 24th    4:00 pm     4300     040/08     090/09       40        Criteria Met
  Mon Aug 24th    5:00 pm     3800     030/08     080/09       35        Criteria Met
  Mon Aug 24th    6:00 pm     2700     020/07     060/08       22        
  Mon Aug 24th    7:00 pm     1400     360/07     040/09       13        
  Mon Aug 24th    8:00 pm      700     320/06     350/08        6        
  Mon Aug 24th   11:00 pm      400     330/00     350/05        2        

  Tue Aug 25th    2:00 am      400     140/00     180/05        2        
  Tue Aug 25th    5:00 am      400     140/05     160/05        2        
  Tue Aug 25th    8:00 am     1200     160/05     180/05        6        
  Tue Aug 25th   11:00 am     2200     200/07     200/07       15        
  Tue Aug 25th    2:00 pm     3700     210/08     210/08       30        Criteria Met
  Tue Aug 25th    5:00 pm     5300     230/07     220/09       49        Criteria Met
  Tue Aug 25th    8:00 pm     1300     290/08     310/10       13        
  Tue Aug 25th   11:00 pm      800     300/03     310/07        6        

  Wed Aug 26th    2:00 am      600     290/02     210/05        3        
  Wed Aug 26th    5:00 am      700     270/00     210/03        2        
  Wed Aug 26th    8:00 am     1300     210/00     190/03        4        
  Wed Aug 26th   11:00 am     2900     230/05     220/05       13        
  Wed Aug 26th    2:00 pm     3800     240/05     230/05       17        
  Wed Aug 26th    5:00 pm     4800     260/05     250/06       28        

Notes:
  Mixing Height = NBM mixing height (MHT)                               
  SFC Winds = NBM 10 meter winds                                        
  Transport Winds = NBM transport wind through the mixed layer          

Criteria (season-dependent; guidance only, forecaster judgment governs):
  Field-burning season (July 5 - September 30):
    Mixing Height >= 3000 feet, with Surface Winds >= 5 mph and Transport Winds >= 7 mph.
  Rest of year:
    Mixing Height >= 2000 feet or Ventilation Index >= 20, with Surface Winds >= 5 mph and Transport Winds >= 7 mph.
  In addition (both seasons):
    Transport wind direction greater than 10 and less than 350 degrees
    (excludes near-north transport, which piles smoke into the south
     end of the valley near Eugene).
  Ventilation Index = Mixing Height (ft) x Transport Wind (mph) / 1000.