889
FNUS75 KBYZ 291534
FWSBYZ

Spot Forecast for North Derby Unit 3...USFS
National Weather Service Billings MT
934 AM MDT Tue Sep 29 2026

Forecast is based on ignition time of 0800 MDT on September 30.
If conditions become unrepresentative...contact the National Weather
Service.

Please contact our office if you have questions
or concerns with this forecast.

.DISCUSSION...

Mainly dry and mild conditions will exist over the burn location
Wednesday into Thursday. While the chance is low, cannot rule out
a stray shower late Thursday over/near the burn location (10
percent chance). Otherwise, winds are expected to be breezy out of
the west to northwest on Wednesday with occasional gusts over 20
mph at times before decreasing and turning out of the east then
southeast Wednesday evening and night. Winds look to be lighter on
Thursday out of the east. Overnight relative humidity recovery is
forecast to be good Wednesday night.

.WEDNESDAY...

Sky/weather.........Mostly sunny.
CWR.................0 percent.
Chance of lightning.0 percent.
Max temperature.....62-66.
Min humidity........29-34 percent.
Wind (20 ft)........
 Slope/valley.......West becoming northwest 6 to 12 mph. Gusts up
                    to 23 mph in the late morning and afternoon.
 Ridgetop...........West becoming northwest around 15 to 20 mph.
Mixing height.......500 ft AGL early in the morning increasing to
                    6500 ft AGL in the afternoon.
Transport winds.....West becoming northwest 10 to 20 mph.

TIME (MDT)      8AM 9AM 10A 11A 12P 1PM 2PM 3PM 4PM 5PM
Sky (%).........22  3   3   3   6   6   6   22  23  30
Weather cov.....
Weather type....
Tstm cov........
Chc of ltng (%).0   0   0   0   0   0   0   0   0   0
Temp............51  53  56  57  60  62  63  64  63  62
RH..............49  47  44  43  41  38  34  31  31  32
20 FT wind dir..W   W   W   W   NW  NW  NW  NW  NW  NW
20 FT wind spd..8   9   10  10  10  10  10  10  10  10
20 FT wind gust.14  18  20  21  21  21  21  21  20  19

.WEDNESDAY NIGHT...

Sky/weather.........Partly cloudy.
CWR.................0 percent.
Chance of lightning.0 percent.
Min temperature.....38-44.
Max humidity........68-75 percent.
Wind (20 ft)........
 Slope/valley.......North 5 to 10 mph shifting to the east in the
                    evening, then shifting to the southeast and south
                    overnight. Occasional gusts up to 15 mph in the
                    evening.
 Ridgetop...........West around 10 to 15 mph.
Mixing height.......Decreasing to 400 ft AGL overnight.
Transport winds.....North 10 to 15 mph shifting to the east 5
                    to 10 mph in the evening, then shifting to the
                    southeast and south 4 to 8 mph overnight.

TIME (MDT)      6PM 7PM 8PM 9PM 10P 11P MID 1AM 2AM 3AM 4AM 5AM
Sky (%).........50  50  49  46  46  46  41  41  41  35  35  35
Weather cov.....
Weather type....
Tstm cov........
Chc of ltng (%).0   0   0   0   0   0   0   0   0   0   0   0
Temp............61  57  54  52  50  49  48  47  45  44  43  42
RH..............35  40  46  51  54  57  59  62  65  68  72  74
20 FT wind dir..NW  N   NE  E   E   E   SE  SE  SE  SE  S   S
20 FT wind spd..10  8   7   7   7   7   6   6   6   4   3   3
20 FT wind gust.15  12  11  11  11  10  10  10  10  8   5   5

.THURSDAY...

Sky/weather.........Mostly sunny.
CWR.................0 percent.
Chance of lightning.5 percent.
Max temperature.....55-60.
Min humidity........38-45 percent.
Wind (20 ft)........
 Slope/valley.......Light winds in the morning becoming east
                    5 to 10 mph by the afternoon.
 Ridgetop...........West 10 to 15 mph.
Mixing height.......Increasing to 3700 ft AGL in the afternoon.
Transport winds.....Southeast to south around 5 mph shifting to the
                    east 5 to 10 mph by the afternoon.

TIME (MDT)      6 AM      9 AM      NOON      3 PM
Sky (%).........29        24        28        39
Weather cov.....
Weather type....NONE      NONE      NONE      NONE
Tstm cov........
Chc of ltng (%).0         0         0         5
Temp............41        43        51        57
RH..............76        68        50        42
20 FT wind......SE 3G4    SE 3G5    E 5G7     E 5G10

$$
Forecaster...Arends
Requested by...Greg Oyler
Type of request...PRESCRIBED
.TAG 2622650.1/BYZ
.DELDT 09/29/26
.FormatterVersion 2.0.0
.EMAIL gregory.oyler@usda.gov