248
FNUS75 KBYZ 121232
FWSBYZ

Spot Forecast for Gallatin Piles...Big Sky Fire Department
National Weather Service Billings MT
632 AM MDT Mon May 12 2025

Forecast is based on ignition time of 0800 MDT on May 12.
If conditions become unrepresentative...contact the National Weather
Service.

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

.DISCUSSION...

Winds will be gusty today, around 30 mph, although there is a 25%
chance of gusts greater than 40 mph between noon and 5 PM. A cold
front will move through from the northwest tonight, increasing the
chance for precipitation and may bring wind gusts to around 25 mph
through midnight. Overnight temperatures will decrease enough for a
rain/snow mix into the morning, although snow is unlikely to
accumulate, with a less than 10% chance of more than half an inch of
snow.

.REST OF TODAY...

Sky/weather.........Mostly sunny. Slight chance of showers and
                    thunderstorms late in the afternoon.
CWR.................20 percent.
Chance of lightning.10 percent.
Max temperature.....65-69.
Min humidity........17-21 percent.
Wind (20 ft)........
 Slope/valley.......South/southwest winds 5 to 10 mph with gusts
                    to around 32 mph. Gusty and erratic winds
                    expected near thunderstorms late in the
                    afternoon.
 Ridgetop...........Southwest around 35 mph.
Mixing height.......2100 ft AGL early in the morning increasing to
                    11200 ft AGL in the afternoon.
Transport winds.....Southwest around 20 mph increasing to 40 to 45
                    mph.

TIME (MDT)      8AM 9AM 10A 11A 12P 1PM 2PM 3PM 4PM 5PM
Sky (%).........46  42  31  26  34  43  57  64  63  69
Weather cov.....                            SCH SCH SCH
Weather type....                            RW  RW  RW
Tstm cov........                            SCH SCH SCH
Chc of ltng (%).0   0   0   0   0   0   0   10  10  10
Temp............47  51  56  60  62  64  66  67  67  66
RH..............49  36  30  25  22  21  20  19  19  20
20 FT wind dir..S   S   SW  SW  SW  SW  SW  SW  SW  S
20 FT wind spd..6   6   7   8   8   9   10  10  9   8
20 FT wind gust.17  18  21  23  26  30  32  32  26  22

.TONIGHT...

Sky/weather.........Mostly cloudy. Chance of rain showers early in
                    the evening, then rain showers likely in the
                    late evening and overnight. Chance of rain
                    showers and snow showers after 3 am.
CWR.................50 percent.
Chance of lightning.13 percent.
Min temperature.....33-37.
Max humidity........83-87 percent.
Wind (20 ft)........
 Slope/valley.......West winds up to 6 mph with gusts to around 25
                    mph becoming light.
 Ridgetop...........Southwest around 10 mph.
Mixing height.......8700 ft AGL early in the evening decreasing to
                    1600 ft AGL overnight.
Transport winds.....Southwest 22 to 30 mph becoming northwest 12 to
                    16 mph early in the evening, then shifting to
                    the southwest 10 to 12 mph after 3 am.

TIME (MDT)      6PM 7PM 8PM 9PM 10P 11P MID 1AM 2AM 3AM 4AM 5AM
Sky (%).........66  93  90  83  88  91  87  83  91  92  92  94
Weather cov.....CHC CHC CHC LKY LKY LKY LKY LKY LKY CHC CHC CHC
Weather type....RW  RW  RW  RW  RW  RW  RW  RW  RW  RS  RS  RS
Tstm cov........
Chc of ltng (%).10  10  10  10  10  10  10  10  10  0   0   0
Temp............66  63  58  53  48  46  43  41  40  39  37  37
RH..............21  27  35  44  54  61  71  75  77  80  82  82
20 FT wind dir..SW  W   W   NW  NW  NW  NW  NW  NW  N   W   W
20 FT wind spd..6   5   5   4   4   3   3   2   2   2   2   2
20 FT wind gust.19  17  13  20  20  8   7   6   6   6   5   4

.TUESDAY...

Sky/weather.........Cloudy. Rain showers and snow showers likely in
                    the morning, then rain showers and chance of
                    thunderstorms in the afternoon.
CWR.................73 percent.
Chance of lightning.30 percent.
Max temperature.....48-52.
Min humidity........50-54 percent.
Wind (20 ft)........
 Slope/valley.......Light winds. Gusty and erratic winds expected
                    near thunderstorms in the afternoon.
 Ridgetop...........Southwest around 5 mph.
Mixing height.......1700 ft AGL early in the morning increasing to
                    4900 ft AGL in the afternoon.
Transport winds.....Southwest 9 to 13 mph shifting to the west 10
                    to 12 mph late in the morning.

TIME (MDT)      6 AM      9 AM      NOON      3 PM
Sky (%).........91        90        91        90
Weather cov.....LIKELY    LIKELY    DEFNTE    DEFNTE
Weather type....RNSN      RNSN      RNSHWR    RNSHWR
Tstm cov........                    CHANCE    CHANCE
Chc of ltng (%).0         10        30        30
Temp............36        38        46        48
RH..............86        74        54        51
20 FT wind......W 2G4     SW 2G5    W 2G7     NW 3G10

$$
Forecaster...Archer/Setzenfand
Requested by...Jon Trapp
Type of request...PRESCRIBED
.TAG 2513758.0/BYZ
.DELDT 05/12/25
.FormatterVersion 2.0.0
.EMAIL jtrapp@bigskyfire.org