439
FNUS75 KBYZ 281236
FWSBYZ

Spot Forecast for North Derby Unit 3...USFS
National Weather Service Billings MT
636 AM MDT Mon Sep 28 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...
Expect dry and seasonably mild conditions at the burn location
this week. Wednesday may be a bit breezy with westerly winds
gusting over 20 mph at times in the afternoon. Thursday looks like
winds may be lighter and more easterly. Overnight RH recoveries
look good. BT

.WEDNESDAY...

Sky/weather.........Sunny.
CWR.................0 percent.
Chance of lightning.1 percent.
Max temperature.....60-64.
Min humidity........29-35 percent.
Wind (20 ft)........
 Slope/valley.......West winds 7 to 11 mph. Gusts up to 22 mph late
                    in the afternoon.
 Ridgetop...........West around 20-25 mph.
Mixing height.......800 ft AGL early in the morning increasing to
                    5600 ft AGL in the afternoon.
Transport winds.....West 12 to 16 mph.

TIME (MDT)      8AM 9AM 10A 11A 12P 1PM 2PM 3PM 4PM 5PM
Sky (%).........18  16  16  16  8   8   8   7   7   7
Weather cov.....
Weather type....
Tstm cov........
Chc of ltng (%).0   0   0   0   0   0   0   0   0   0
Temp............51  53  55  57  59  61  62  62  62  61
RH..............46  45  44  42  40  37  35  33  32  33
20 FT wind dir..SW  W   W   W   NW  NW  NW  NW  NW  NW
20 FT wind spd..8   7   7   7   6   7   8   11  11  10
20 FT wind gust.12  11  11  11  12  15  16  22  23  21

.WEDNESDAY NIGHT...

Sky/weather.........Partly cloudy.
CWR.................0 percent.
Chance of lightning.1 percent.
Min temperature.....37-44.
Max humidity........63-73 percent.
Wind (20 ft)........
 Slope/valley.......Northwest winds 5 to 9 mph shifting to the east
                    up to 6 mph in the late evening and overnight,
                    then becoming light after 3 am.
 Ridgetop...........West around 20 mph.
Mixing height.......3100 ft AGL early in the evening decreasing to
                    400 ft AGL overnight.
Transport winds.....Northwest 15 to 18 mph shifting to the east 8
                    to 12 mph early in the evening, then shifting
                    to the southeast 8 to 9 mph late in the
                    evening.

TIME (MDT)      6PM 7PM 8PM 9PM 10P 11P MID 1AM 2AM 3AM 4AM 5AM
Sky (%).........8   8   8   29  29  29  43  43  43  36  36  36
Weather cov.....
Weather type....
Tstm cov........
Chc of ltng (%).0   0   0   0   0   0   0   0   0   0   0   0
Temp............59  56  53  50  49  48  47  46  45  44  43  42
RH..............35  39  44  49  52  55  57  58  58  59  62  64
20 FT wind dir..NW  NW  NW  NE  NE  NE  E   E   E   SE  SE  SE
20 FT wind spd..7   7   7   6   6   6   5   5   5   3   3   3
20 FT wind gust.13  13  13  10  10  10  6   6   6   5   5   5

.THURSDAY...

Sky/weather.........Sunny.
CWR.................0 percent.
Chance of lightning.1 percent.
Max temperature.....57-61.
Min humidity........37-41 percent.
Wind (20 ft)........
 Slope/valley.......Light winds becoming northeast up to 8 mph late
                    in the afternoon.
 Ridgetop...........West around 15 mph.
Mixing height.......400 ft AGL early in the morning increasing to
                    2900 ft AGL in the afternoon in the morning and
                    early afternoon.
Transport winds.....Southeast 7 to 8 mph shifting to the east 8 to
                    10 mph late in the morning.

TIME (MDT)      6 AM      9 AM      NOON      3 PM
Sky (%).........23        21        19        13
Weather cov.....
Weather type....NONE      NONE      NONE      NONE
Tstm cov........
Chc of ltng (%).0         0         0         0
Temp............42        44        53        59
RH..............67        61        51        40
20 FT wind......S 3G4     SE 3G5    NE 4G7    NE 5G10

$$
Forecaster...Tesar
Requested by...Greg Oyler
Type of request...PRESCRIBED
.TAG 2622650.0/BYZ
.DELDT 09/28/26
.FormatterVersion 2.0.0
.EMAIL gregory.oyler@usda.gov