OPEN BURNING ANNOUNCEMENT MODEL GUIDANCE
1000 PM PDT MON AUG 24 2026
NBM model output for: Portland KPDX  45.59N, -122.59W 
Model Run Time:  2026-08-25 04Z

                             Mixing      Sfc     Transport                                 
                   Time      Height     Winds      Winds   Ventilation                    
  Day   Date      (PDT)     (ft MSL)    (mph)      (mph)      Index       Remarks         
  === ========   ========   =======    =======    =======    =======      =======         
  Mon Aug 24th   10:00 pm      400     310/02     360/05        2        
  Mon Aug 24th   11:00 pm      400     250/00     060/03        1        

  Tue Aug 25th   12:00 am      400     170/00     150/05        2        
  Tue Aug 25th    1:00 am      400     150/00     150/05        2        
  Tue Aug 25th    2:00 am      400     150/00     170/06        2        
  Tue Aug 25th    3:00 am      400     140/03     170/06        2        
  Tue Aug 25th    4:00 am      400     120/05     170/06        2        
  Tue Aug 25th    5:00 am      500     130/06     160/08        4        
  Tue Aug 25th    6:00 am      600     140/06     170/07        4        
  Tue Aug 25th    7:00 am      600     140/06     160/06        3        
  Tue Aug 25th    8:00 am     1100     160/06     180/09       10        
  Tue Aug 25th    9:00 am     1300     180/06     190/07        9        
  Tue Aug 25th   10:00 am     1800     190/07     190/08       14        
  Tue Aug 25th   11:00 am     2200     190/08     200/08       18        
  Tue Aug 25th   12:00 pm     2700     200/08     200/08       22        
  Tue Aug 25th    1:00 pm     3200     200/08     200/08       26        Criteria Met
  Tue Aug 25th    2:00 pm     3800     200/08     210/08       31        Criteria Met
  Tue Aug 25th    3:00 pm     4100     210/08     210/08       33        Criteria Met
  Tue Aug 25th    4:00 pm     4700     210/08     200/10       49        Criteria Met
  Tue Aug 25th    5:00 pm     4900     220/07     210/09       45        Criteria Met
  Tue Aug 25th    6:00 pm     4300     230/07     230/10       45        Criteria Met
  Tue Aug 25th    7:00 pm     2000     280/07     280/10       21        
  Tue Aug 25th    8:00 pm     1000     310/07     310/10       10        
  Tue Aug 25th    9:00 pm      600     320/07     330/09        6        
  Tue Aug 25th   10:00 pm      600     310/06     320/07        4        
  Tue Aug 25th   11:00 pm      500     300/03     320/06        3        

  Wed Aug 26th    2:00 am      500     280/00     320/03        2        
  Wed Aug 26th    5:00 am      600     210/00     300/02        1        
  Wed Aug 26th    8:00 am     1200     220/00     230/03        4        
  Wed Aug 26th   11:00 am     2500     210/03     210/05       12        
  Wed Aug 26th    2:00 pm     3700     230/05     220/06       21        
  Wed Aug 26th    5:00 pm     5100     250/05     230/07       35        Criteria Met
  Wed Aug 26th    8:00 pm     1500     310/07     330/09       14        
  Wed Aug 26th   11:00 pm      900     320/03     340/07        6        

  Thu Aug 27th    2:00 am      800     280/02     360/02        2        
  Thu Aug 27th    5:00 am     1100     200/03     180/03        4        
  Thu Aug 27th    8:00 am     1700     200/06     210/06       10        
  Thu Aug 27th   11:00 am     4700     210/07     220/07       32        Criteria Met
  Thu Aug 27th    2:00 pm     6900     240/08     240/08       56        Criteria Met
  Thu Aug 27th    5:00 pm     6800     280/08     280/09       63        Criteria Met
  Thu Aug 27th    8:00 pm     2300     320/08     330/09       21        

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

Criteria:
  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.
  Ventilation Index = Mixing Height (ft) x
    Transport Wind (mph) / 1000.