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.