407
FNUS75 KRIW 201256
FWSRIW

Spot Forecast for Butterfly...BLM
National Weather Service Riverton WY
656 AM MDT Mon Jul 20 2026

Forecast is based on forecast start time of 0700 MDT on July 20.
If conditions become unrepresentative, contact the National Weather
Service

.DISCUSSION...

...Thunderstorms imply strong gusty and erratic winds...

The day will start off largely dry. Increasing moisture from the south
will bring around a 20 percent chance of a shower or thunderstorm
between 1400 to midnight, with a 10 percent chance after midnight. Wind
will be largely from the east to northeast and remain generally 12 mph
or less through the day. The exception will be around any shower or
thunderstorm where wind gusts over 40 mph will be possible. Mixing and
smoke dispersal should become very good after inversions break around
1000. Increasing moisture on Tuesday will bring an increased chance
of a shower of thunderstorm, with the chance of a wetting rain increasing
to over 30 percent. Wednesday looks like the wettest day with a greater
than 60 percent chance of a shower or thunderstorm and a greater than
50 percent chance of a wetting rain.

.REST OF TODAY...

Sky/weather.........Partly sunny (30-40 percent). Slight chance of
                    showers and thunderstorms after 1400.
CWR.................0 percent.
Chance of pcpn......20 percent.
Chance of thunder...15 percent.
Max temperature.....Around 92.
Min humidity........19 percent.
Wind (20 ft)........Light winds. Gusty and erratic winds expected
                    near thunderstorms late in the afternoon.
Ridgetop wind.......Light winds until 0900. Northeast 10 to 15 mph
                    after 1400.
Mixing height.......2000 ft AGL until 1100. 11500 ft AGL after
                    1300.
Transport winds.....East 7 to 13 mph.
Smoke dispersal.....Poor until 1000, becoming very good after 1300.

TIME (MDT)      7AM 8AM 9AM 10A 11A 12P 1PM 2PM 3PM 4PM 5PM
Sky (%).........30  40  30  20  25  30  30  30  30  35  40
Weather cov.....                            SCH SCH SCH SCH
Weather type....                            RW  RW  RW  RW
Tstm cov........                            SCH SCH SCH SCH
CWR.............0   0   0   0   0   0   0   0   0   0   0
Chc of pcpn (%).0   0   0   0   0   10  10  20  20  20  20
Chc of thdr (%).0   0   0   0   0   0   0   20  20  20  20
Temp............67  67  72  77  81  84  88  90  91  92  92
RH..............53  54  49  42  36  31  26  22  20  19  19
20 FT wind dir..SE  E   SE  SE  SE  SE  E   NE  NE  E   NE
20 FT wind spd..3   2   3   3   3   3   4   4   5   6   6
20 FT wind gust.5                       6   6   7   8   10
Ridge wind dir..E   E   SE  SE  SE  SE  E   NE  NE  E   NE
Ridge wind spd..5   5   10  10  10  10  10  10  10  10  15
Mix hgt (kft)...0.5 0.5 1.5 2.0 4.5 8.0 11  12  11  12  11
Transp wind dir.E   SE  SE  SE  SE  E   E   NE  NE  E   E
Transp wind spd.7   7   8   8   8   8   9   9   10  12  13
SDspl kt-ft/10003   4   9   15  31  57  86  94  101 113 124

.TONIGHT...

Sky/weather.........Partly cloudy (45-55 percent). Slight chance of
                    showers and thunderstorms before midnight.
CWR.................2 percent.
Chance of pcpn......20 percent.
Chance of thunder...19 percent.
Min temperature.....Around 62.
Max humidity........58 percent.
Wind (20 ft)........Light winds until 1900, then east 7 to 8 mph
                    with gusts to around 13 mph until 2200, then
                    light. Gusty and erratic winds expected near
                    thunderstorms in the evening.
Ridgetop wind.......Northeast 10 to 15 mph.
Mixing height.......9500 ft AGL until 2000, then 500 ft AGL.
Transport winds.....Northeast 13 to 15 mph until 2400, then north
                    10 to 13 mph.
Smoke dispersal.....Very good until 2000. Poor after 2200.

TIME (MDT)      6PM 7PM 8PM 9PM 10P 11P MID 1AM 2AM 3AM 4AM 5AM
Sky (%).........40  60  65  55  55  60  55  40  40  50  45  50
Weather cov.....SCH SCH SCH SCH SCH SCH
Weather type....RW  RW  RW  RW  RW  RW
Tstm cov........SCH SCH SCH SCH SCH SCH
CWR.............0   0   0   0   0   0   0   0   0   0   0   0
Chc of pcpn (%).20  20  20  20  20  10  10  10  0   0   0   0
Chc of thdr (%).20  20  20  20  20  10  10  10  0   0   0   0
Temp............91  89  87  79  77  75  73  71  70  68  66  65
RH..............20  21  23  31  36  39  40  43  46  50  52  53
20 FT wind dir..E   E   NE  SE  NE  NE  N   N   N   NE  NE  NE
20 FT wind spd..6   7   7   8   6   6   6   6   6   6   6   5
20 FT wind gust.10  11  11  13  10  10  8   10  10  10  8   7
Ridge wind dir..E   E   NE  SE  NE  NE  N   N   N   NE  NE  NE
Ridge wind spd..15  15  15  15  15  15  10  15  15  15  10  10
Mix hgt (kft)...11  9.5 1.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5
Transp wind dir.E   NE  N   E   E   N   N   N   N   N   NE  NE
Transp wind spd.13  14  14  15  13  13  12  13  13  13  12  10
SDspl kt-ft/1000116 115 18  8   7   6   7   6   6   6   5   5

.FORECAST DAYS 3 THROUGH 5...
.WEDNESDAY...
Mostly cloudy. Showers and chance of thunderstorms. Lows in the
upper 50s. Highs in the mid 80s. Light winds.
.THURSDAY...
Mostly cloudy. Showers and chance of thunderstorms. Lows in the
upper 50s. Highs around 80. Southwest winds around 7 mph.
.FRIDAY...
Partly cloudy. Chance of showers and thunderstorms. Lows in the
upper 50s. Highs in the mid 80s. Light winds.

$$
Forecaster...Hattings
Requested by...IC
Type of request...WILDFIRE
.TAG 2617796.0/RIW
.DELDT 07/20/26
.FormatterVersion 2.0.0
.EMAIL wycpc@firenet.gov