OPEN BURNING ANNOUNCEMENT MODEL GUIDANCE
800 AM PDT TUE AUG 25 2026
NBM model output for: Portland KPDX  45.59N, -122.59W 
Model Run Time:  2026-08-25 15Z

                             Mixing      Sfc     Transport                                 
                   Time      Height     Winds      Winds   Ventilation                    
  Day   Date      (PDT)     (ft MSL)    (mph)      (mph)      Index       Remarks         
  === ========   ========   =======    =======    =======    =======      =======         
  Tue Aug 25th    9:00 am     1400     180/06     180/08       11        
  Tue Aug 25th   10:00 am     1900     180/07     190/08       15        
  Tue Aug 25th   11:00 am     2200     190/07     200/07       15        
  Tue Aug 25th   12:00 pm     2700     190/07     200/07       19        
  Tue Aug 25th    1:00 pm     3000     200/08     200/08       24        Criteria Met
  Tue Aug 25th    2:00 pm     3600     200/08     210/08       29        Criteria Met
  Tue Aug 25th    3:00 pm     4100     210/08     210/08       33        Criteria Met
  Tue Aug 25th    4:00 pm     4500     210/07     210/08       36        Criteria Met
  Tue Aug 25th    5:00 pm     4800     220/07     210/09       44        Criteria Met
  Tue Aug 25th    6:00 pm     4400     230/07     230/09       41        Criteria Met
  Tue Aug 25th    7:00 pm     2400     260/07     270/09       22        
  Tue Aug 25th    8:00 pm      700     310/08     310/10        7        
  Tue Aug 25th    9:00 pm      500     320/07     330/09        5        
  Tue Aug 25th   10:00 pm      500     310/06     320/07        3        
  Tue Aug 25th   11:00 pm      500     280/03     310/06        3        

  Wed Aug 26th   12:00 am      500     270/02     320/05        2        
  Wed Aug 26th    1:00 am      500     290/00     320/03        2        
  Wed Aug 26th    2:00 am      500     290/00     340/03        2        
  Wed Aug 26th    3:00 am      500     150/00     350/03        2        
  Wed Aug 26th    4:00 am      600     180/00     320/02        1        
  Wed Aug 26th    5:00 am      600     210/00     320/02        1        
  Wed Aug 26th    6:00 am      600     180/00     320/01        1        
  Wed Aug 26th    7:00 am      800     200/00     210/02        2        
  Wed Aug 26th    8:00 am     1200     190/00     190/03        4        
  Wed Aug 26th    9:00 am     1800     200/00     200/03        6        
  Wed Aug 26th   11:00 am     2700     220/05     220/05       12        
  Wed Aug 26th    2:00 pm     3800     230/05     230/06       22        
  Wed Aug 26th    5:00 pm     5200     250/05     240/07       36        Criteria Met
  Wed Aug 26th    8:00 pm     1500     320/06     320/09       14        
  Wed Aug 26th   11:00 pm      700     320/03     330/07        5        

  Thu Aug 27th    2:00 am      700     320/00     330/03        2        
  Thu Aug 27th    5:00 am      800     240/05     260/05        4        
  Thu Aug 27th    8:00 am     1900     200/06     200/06       11        
  Thu Aug 27th   11:00 am     3500     210/07     220/07       24        Criteria Met
  Thu Aug 27th    2:00 pm     6200     220/08     240/08       50        Criteria Met
  Thu Aug 27th    5:00 pm     6300     260/08     270/08       51        Criteria Met
  Thu Aug 27th    8:00 pm     2400     310/08     320/09       22        
  Thu Aug 27th   11:00 pm      700     320/07     330/08        6        

  Fri Aug 28th    2:00 am      600     330/06     340/06        3        
  Fri Aug 28th    5:00 am      700     340/03     350/05        3        
  Fri Aug 28th    8:00 am     1200     340/00     350/03        4        

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.