047
FNUS75 KRIW 202145
FWSRIW

Spot Forecast for Butterfly Fire...Casper Interagency Dispatch Center
National Weather Service Riverton WY
345 PM MDT Mon Jul 20 2026

Forecast is based on forecast start time of 1800 MDT on July 20.
If conditions become unrepresentative, contact the National Weather
Service

.DISCUSSION...

Scattered rain showers and thunderstorms will remain near the fire
this evening through most of tonight. Most lightning will end by
midnight. There will be a short break from showers and storms from
sunrise until noon Tuesday. By noon scattered showers and storms
will develop once again and remain in the area through Tuesday
night. The thunderstorms will be wet, especially Tuesday as
monsoonal moisture moves into the area.

A northeasterly wind around 10-15 mph will move in behind a
boundary around 2100 this evening and will continue through much
of Tuesday morning. By Tuesday afternoon wind will be variable and
gusty due to numerous showers and storms. Smoke dispersal will
decrease from very good this afternoon to poor this evening after 2000.
It will then become good to very good after 1300 Tuesday
afternoon. RH recovery will be poor to fair tonight and improve to
very good Tuesday night.

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

.TONIGHT...

Sky/weather.........Partly to mostly cloudy (40-70%) Isolated showers
                    and thunderstorms.
CWR.................1 percent.
Chance of pcpn......20 percent.
Chance of thunder...15 percent.
Min temperature.....Around 63.
Max humidity........57 percent.
Wind (20 ft)........Northeast winds 7 to 13 mph with gusts to
                    around 18 mph. Gusty and erratic winds expected
                    near thunderstorms early in the evening.
Ridgetop wind.......Northeast 15 to 20 mph.
Mixing height.......11500 ft AGL until 1900. 500 ft AGL after 2000.
Transport winds.....East 15 to 21 mph until 2000, then 16 to 17 mph
                    until 2300, then northeast 14 to 17 mph.
Smoke dispersal.....Excellent early in the evening decreasing to
                    Poor after 2300.

TIME (MDT)      6PM 7PM 8PM 9PM 10P 11P MID 1AM 2AM 3AM 4AM 5AM
Sky (%).........35  65  70  70  65  70  50  50  45  45  60  55
Weather cov.....ISO ISO
Weather type....RW  RW
Tstm cov........ISO ISO
CWR.............0   0   0   0   0   0   0   0   0   0   0   0
Chc of pcpn (%).20  20  10  10  10  10  0   0   0   0   0   0
Chc of thdr (%).20  20  10  10  10  10  0   0   0   0   0   0
Temp............92  90  88  80  78  76  74  72  70  68  66  65
RH..............17  18  20  28  33  35  38  40  43  49  51  52
20 FT wind dir..E   E   E   E   E   NE  NE  NE  NE  NE  NE  NE
20 FT wind spd..8   13  10  10  9   7   7   10  10  9   8   8
20 FT wind gust.12  18  14  14  13  10  10  14  14  13  12  12
Ridge wind dir..E   E   E   E   E   NE  NE  NE  NE  NE  NE  NE
Ridge wind spd..15  20  15  15  15  15  15  15  15  15  15  15
Mix hgt (kft)...12  9.5 1.0 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5
Transp wind dir.E   E   SE  E   E   E   NE  NE  N   N   NE  NE
Transp wind spd.15  21  17  17  16  14  14  17  17  16  15  15
SDspl kt-ft/1000146 171 18  9   9   8   7   8   8   8   7   7

.TUESDAY...

Sky/weather.........Mostly sunny (30-40 percent) then becoming
                    mostly cloudy (65-75 percent). Scattered showers
                    and thunderstorms in the afternoon. Patchy smoke
                    in the afternoon.
CWR.................5 percent.
Chance of pcpn......40 percent.
Chance of thunder...34 percent.
Max temperature.....Around 91.
Min humidity........20 percent.
Wind (20 ft)........Northeast winds 7 to 8 mph until 0800, then
                    light until 1600, then east around 9 mph. Gusty
                    and erratic winds expected near thunderstorms
                    in the afternoon.
Ridgetop wind.......Northeast 10 to 15 mph until 0900, then south.
Mixing height.......2000 ft AGL until 1100, then increasing to 11000
                    ft AGL by 1300 until 1700, then 7000 ft AGL.
Transport winds.....Northeast 14 to 15 mph until 0800. West around
                    16 mph after 1600.
Smoke dispersal.....Poor until 1200, then increasing to very good
                    in the afternoon until 1700, then good.

TIME (MDT)      6AM 7AM 8AM 9AM 10A 11A 12P 1PM 2PM 3PM 4PM 5PM
Sky (%).........50  45  30  15  15  10  10  20  15  20  60  70
Weather cov.....                        ISO ISO ISO ISO SCT SCT
Weather type....                        RW  RW  RW  RW  RW  RW
Tstm cov........                        ISO ISO ISO ISO SCT SCT
CWR.............0   0   0   0   0   0   0   0   0   0   5   5
Chc of pcpn (%).10  10  10  10  10  10  20  20  20  20  30  30
Chc of thdr (%).0   0   0   0   0   0   20  20  20  20  30  30
Temp............64  63  67  71  78  81  86  89  89  91  89  88
RH..............57  56  49  42  37  33  29  24  21  20  20  23
20 FT wind dir..NE  NE  E   SE  S   S   S   S   SW  SW  SE  E
20 FT wind spd..8   7   6   3   4   4   5   5   6   6   9   9
20 FT wind gust.12  10  8   5   6   6   7   10  10  10  13  13
Ridge wind dir..NE  NE  E   SE  S   S   S   S   SW  SW  SE  E
Ridge wind spd..15  15  10  10  10  10  10  10  10  10  15  15
Mix hgt (kft)...0.5 0.5 1.0 1.5 2.0 3.5 6.5 9.5 11  12  11  7.0
Transp wind dir.NE  NE  E   S   S   S   S   SW  S   SW  W   NW
Transp wind spd.15  14  12  8   9   9   10  10  12  12  16  16
SDspl kt-ft/10007   6   8   11  18  27  57  84  108 114 149 99

.FORECAST DAYS 3 THROUGH 5...
.THURSDAY...
Mostly cloudy. Showers and chance of thunderstorms. Lows in the
upper 50s. Highs around 80. Light winds.
.FRIDAY...
Partly cloudy. Chance of showers and thunderstorms. Lows in the
upper 50s. Highs in the mid 80s. Light winds.
.SATURDAY...
Partly cloudy. Lows around 60. Highs in the upper 80s. Light
winds.

$$
Forecaster...Rowe
Requested by...Teddy Donoghue
Type of request...WILDFIRE
.TAG 2617814.0/RIW
.DELDT 07/20/26
.FormatterVersion 2.0.0
.EMAIL wycpc@firenet.gov