747
FNUS75 KBYZ 302314
FWSBYZ

Spot Forecast for North Derby Unit 3...USFS
National Weather Service Billings MT
514 PM MDT Wed Sep 30 2026

Forecast is based on ignition time of 1800 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...

Breezy conditions will begin to decrease after 2000 MDT this evening.
With east winds in place Thursday after a frontal passage this evening,
min RHs will be in the mid 40s percent with lighter winds than today
(Wednesday). Conditions turn dryer for Friday with about a 25% chance
for gusts to 20 mph.

.TONIGHT...

Sky/weather.........Partly cloudy then becoming mostly cloudy.
CWR.................0 percent.
Chance of lightning.3 percent.
Min temperature.....39-43.
Max humidity........74-78 percent.
Wind (20 ft)........
 Slope/valley.......Northwest 8 to 12 mph with gusts to 22 mph in
the evening shifting to the southeast then south
at 5 to 10 mph with gusts to 17 mph late evening.
 Ridgetop...........West becoming southwest around 10 to 15 mph.
Mixing height.......Decreasing to 500 ft AGL overnight.
Transport winds.....North at 15 mph becoming southeast at 10 mph.

TIME (MDT)      6PM 7PM 8PM 9PM 10P 11P MID 1AM 2AM 3AM 4AM 5AM
Sky (%).........18  17  42  56  61  72  48  38  24  52  58  52
Weather cov.....
Weather type....
Tstm cov........
Chc of ltng (%).0   0   0   0   0   0   0   0   0   0   0   0
Temp............61  58  53  51  50  48  47  46  45  45  43  41
RH..............36  45  56  64  66  69  72  72  72  71  73  76
20 FT wind dir..NW  N   NE  E   E   SE  SE  SE  SE  SE  SE  S
20 FT wind spd..10  10  9   9   9   8   8   8   8   7   6   5
20 FT wind gust.20  20  16  13  13  12  12  11  11  10  8   7

.THURSDAY...

Sky/weather.........Partly sunny then becoming mostly sunny.
CWR.................0 percent.
Chance of lightning.3 percent.
Max temperature.....53-57.
Min humidity........46-50 percent.
Wind (20 ft)........
 Slope/valley.......South winds becoming east then southeast at 4 to
8 mph with gusts to 16 mph in the afternoon.
 Ridgetop...........Southeast around 10 mph.
Mixing height.......Increasing to 3700 ft AGL in the afternoon.
Transport winds.....Southeast shifting to the east to
                    northeast in the afternoon at 7 to 10 mph.

TIME (MDT)      6AM 7AM 8AM 9AM 10A 11A 12P 1PM 2PM 3PM 4PM 5PM
Sky (%).........51  51  60  59  56  44  50  24  26  32  35  26
Weather cov.....
Weather type....
Tstm cov........
Chc of ltng (%).0   0   0   0   0   0   0   0   0   0   0   0
Temp............41  41  41  42  44  46  48  52  54  54  55  53
RH..............76  76  74  71  70  68  63  60  53  51  48  47
20 FT wind dir..S   S   SE  SE  E   NE  NE  NE  NE  NE  NE  E
20 FT wind spd..4   4   4   4   4   5   6   6   6   6   6   6
20 FT wind gust.6   5   5   5   6   6   7   7   10  12  14  14

.THURSDAY NIGHT...

Sky/weather.........Partly cloudy.
CWR.................0 percent.
Chance of lightning.3 percent.
Min temperature.....40-44.
Max humidity........74-78 percent.
Wind (20 ft)........
 Slope/valley.......Southeast winds 5 to 10 mph with gusts to 17 mph
in the evening becoming light.
 Ridgetop...........Southwest around 10 mph.
Mixing height.......Decreasing to 400 ft AGL overnight.
Transport winds.....Southeast 7 to 10 mph shifting to the west 8 to
                    9 mph after midnight.

TIME (MDT)      6 PM      9 PM      MIDNGT    3 AM
Sky (%).........47        47        47        25
Weather cov.....
Weather type....NONE      NONE      NONE      NONE
Tstm cov........
Chc of ltng (%).0         0         0         0
Temp............53        47        44        44
RH..............55        71        76        72
20 FT wind......E 6G11    SE 6G10   S 4G6     SW 3G5

.FRIDAY...

Sky/weather.........Sunny.
CWR.................0 percent.
Chance of lightning.0 percent.
Max temperature.....66-70.
Min humidity........26-30 percent.
Wind (20 ft)........
 Slope/valley.......Southwest becoming west 4 to 8 mph with gusts to
16 mph.
 Ridgetop...........West around 10 to 15 mph.
Mixing height.......Increasing to 6500 ft AGL in the afternoon.
Transport winds.....West 10 to 15 mph.

TIME (MDT)      6 AM      9 AM      NOON      3 PM
Sky (%).........30        11        13        25
Weather cov.....
Weather type....NONE      NONE      NONE      NONE
Tstm cov........
Chc of ltng (%).0         0         0         0
Temp............42        48        61        68
RH..............72        57        41        28
20 FT wind......SW 4G6    SW 6G8    W 4G11    W 5G14

$$
Forecaster...Stetzer
Requested by...Greg Oyler
Type of request...PRESCRIBED
.TAG 2622650.3/BYZ
.DELDT 09/30/26
.FormatterVersion 2.0.0
.EMAIL gregory.oyler@usda.gov