846  
FNUS75 KBYZ 011006  
FWSBYZ  
 
SPOT FORECAST FOR NORTH DERBY UNIT 3...USFS  
NATIONAL WEATHER SERVICE BILLINGS MT  
406 AM MDT THU OCT 1 2026  
 
FORECAST IS BASED ON IGNITION TIME OF 1000 MDT ON OCTOBER 01.  
IF CONDITIONS BECOME UNREPRESENTATIVE...CONTACT THE NATIONAL WEATHER  
SERVICE.  
 
PLEASE CONTACT OUR OFFICE IF YOU HAVE QUESTIONS  
OR CONCERNS WITH THIS FORECAST.  
   
DISCUSSION
 
 
LOOK FOR VARIABLE CLOUDINESS ACROSS THE BURN SITE TODAY.  
CONDITIONS ARE STILL EXPECTED TO BE COOLER WITH EASTERLY WINDS  
PREVAILING. RH READINGS ARE ONLY EXPECTED TO DROP TO AROUND 50-55%  
RANGE BY MID AFTERNOON. RH RECOVERIES WILL BE ABOVE 65% TONIGHT.  
WINDS SHOULD TURN A LITTLE MORE SOUTHWESTERLY LATE TONIGHT INTO  
FRIDAY. FRIDAY WILL BE MOSTLY SUNNY AND WARMER, AND HUMIDITY  
DROPPING INTO THE 20S. WINDS WILL BE WEST/NORTHWEST WITH SOME  
GUSTY CONDITIONS IN THE AFTERNOON, BUT NOT AS STRONG AS WEDNESDAYS.  
BT  
 
   
TODAY
 
 
SKY/WEATHER.........PARTLY SUNNY.  
CWR.................0 PERCENT.  
CHANCE OF LIGHTNING.0 PERCENT.  
MAX TEMPERATURE.....53-57.  
MIN HUMIDITY........50-55 PERCENT.  
WIND (20 FT)........  
SLOPE/VALLEY.......EAST/SOUTHEAST WINDS 5-7 MPH EARLY, 6-9 MPH WITH A FEW GUSTS  
TO 13-16 MPH IN THE AFTERNOON.  
RIDGETOP...........WEST AROUND 15 MPH.  
MIXING HEIGHT.......1400 FT AGL EARLY IN THE MORNING INCREASING TO  
3300 FT AGL IN THE AFTERNOON.  
TRANSPORT WINDS.....EAST 7 TO 9 MPH.  
 
TIME (MDT) 10A 11A 12P 1PM 2PM 3PM 4PM 5PM  
SKY (%).........35 36 35 27 39 31 39 44  
WEATHER COV.....  
WEATHER TYPE....  
TSTM COV........  
CHC OF LTNG (%).0 0 0 0 0 0 0 0  
TEMP............46 47 49 52 54 55 55 54  
RH..............72 70 65 62 56 54 54 54  
20 FT WIND DIR..SE E E E E E E E  
20 FT WIND SPD..6 6 6 6 7 8 8 7  
20 FT WIND GUST.7 10 12 13 13 14 14 12  
   
TONIGHT
 
 
SKY/WEATHER.........PARTLY CLOUDY.  
CWR.................0 PERCENT.  
CHANCE OF LIGHTNING.0 PERCENT.  
MIN TEMPERATURE.....39-45.  
MAX HUMIDITY........70-76 PERCENT.  
WIND (20 FT)........  
SLOPE/VALLEY.......SOUTHEAST WINDS UP TO 7 MPH IN THE EVENING  
BECOMING LIGHT, THEN BECOMING SOUTHWEST UP TO 6  
MPH AFTER 3 AM.  
RIDGETOP...........SOUTH AROUND 5 MPH.  
MIXING HEIGHT.......2100 FT AGL EARLY IN THE EVENING DECREASING TO  
400 FT AGL OVERNIGHT.  
TRANSPORT WINDS.....SOUTHEAST 7 TO 10 MPH SHIFTING TO THE SOUTHWEST  
6 TO 8 MPH OVERNIGHT.  
 
TIME (MDT) 6PM 7PM 8PM 9PM 10P 11P MID 1AM 2AM 3AM 4AM 5AM  
SKY (%).........47 51 44 42 28 44 49 46 58 59 51 47  
WEATHER COV.....  
WEATHER TYPE....  
TSTM COV........  
CHC OF LTNG (%).0 0 0 0 0 0 0 0 0 0 0 0  
TEMP............53 51 48 47 46 45 45 45 44 44 45 42  
RH..............55 60 66 69 71 72 73 73 70 67 66 67  
20 FT WIND DIR..E SE SE SE SE S S S SW W W SW  
20 FT WIND SPD..7 7 7 7 6 5 4 4 4 4 5 6  
20 FT WIND GUST.11 11 12 13 10 7 6 6 6 6 6 7  
   
FRIDAY
 
 
SKY/WEATHER.........BECOMING MOSTLY SUNNY.  
CWR.................0 PERCENT.  
CHANCE OF LIGHTNING.0 PERCENT.  
MAX TEMPERATURE.....68-72.  
MIN HUMIDITY........23-27 PERCENT.  
WIND (20 FT)........  
SLOPE/VALLEY.......WEST WINDS 7-10 MPH WITH AFTERNOON GUSTS 16-22 MPH.  
RIDGETOP...........NORTHWEST AROUND 12 MPH.  
MIXING HEIGHT.......INCREASING TO 7400 FT AGL IN THE AFTERNOON.  
TRANSPORT WINDS.....WEST 9 TO 13 MPH INCREASING TO 13 TO 17 MPH  
IN THE AFTERNOON.  
 
TIME (MDT) 6 AM 9 AM NOON 3 PM  
SKY (%).........51 22 32 23  
WEATHER COV.....  
WEATHER TYPE....NONE NONE NONE NONE  
TSTM COV........  
CHC OF LTNG (%).0 0 0 0  
TEMP............45 53 64 70  
RH..............61 49 36 24  
20 FT WIND......SW 6G10 W 6G11 NW 7G14 W 8G17  
 

 
FORECASTER...TESAR  
REQUESTED BY...GREG OYLER  
TYPE OF REQUEST...PRESCRIBED  
.TAG 2622650.4/BYZ  
.DELDT 10/01/26  
.FORMATTERVERSION 2.0.0  
.EMAIL GREGORY.OYLER@USDA.GOV  
 
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