Spot Forecast
Issued by NWS Riverton, WY
Issued by NWS Riverton, WY
240
FNUS75 KRIW 170957
FWSRIW
Spot Forecast for South Cache...Yellowstone National Park
National Weather Service Riverton WY
357 AM MDT Sun Aug 17 2025
Forecast is based on forecast start time of 0500 MDT on August 17.
If conditions become unrepresentative, contact the National Weather
Service
.DISCUSSION...
Skies will start mostly clear this morning, with winds slowly
switching to upslope around 5 to 10 mph through 1100. General winds will
then set up from the southwest through the day, 10 to 15 mph, with
occasional gusts near 20 mph after 1400. Showers and thunderstorms
are expected as early as 1100, and will continue through most of the
afternoon, peaking between 1300 and 1800. Rainfall accumulations
will remain light, with the main thunderstorm threat being gusty and
variable winds. Some gusts could reach 50 mph. After sunset, shower
activity quickly decreases, with light downslope winds returning
overnight.
Monday will be the start of a drying and warming trend, with
temperatures rising into the 70s allowing humidity levels to fall
below 20 percent in the afternoon. Very isolated showers are
possible (~10%) in the afternoon, but will be brief, and any wind gusts
will likely be lower than the past several days.
...Thunderstorms imply strong gusty and erratic winds...
.TODAY...
Sky/weather.........Mostly sunny (35-45 percent) then becoming
mostly cloudy (70-80 percent). Scattered rain
showers and isolated thunderstorms in the
morning, then numerous rain showers and
scattered thunderstorms in the afternoon.
CWR.................0 percent increasing to 10 percent in the
afternoon.
Chance of pcpn......60 percent.
Chance of thunder...38 percent.
Max temperature.....Around 66.
Min humidity........28 percent.
Wind (20 ft)........Light winds until 1000, then southwest 7 to 12
mph with gusts to around 17 mph. Gusty and
erratic winds expected near thunderstorms late
in the morning. Gusty and erratic winds
expected near thunderstorms in the afternoon.
Ridgetop wind.......Southwest 10 to 15 mph until 1200, then 15 to
20 mph.
Mixing height.......2500 ft AGL after 0900 until 1100, then 5000 ft
AGL until 1200, then 8000 ft AGL until 1400,
then 9000 ft AGL until 1500, then 7000 ft AGL
until 1700, then 3000 ft AGL.
Transport winds.....Southwest 8 to 17 mph until 1200, then 16 to 20
mph.
Smoke dispersal.....Poor until 1100, then good until 1200, then
good early in the morning increasing to very
good in the afternoon until 1600, then good
until 1700, then fair.
TIME (MDT) 6AM 7AM 8AM 9AM 10A 11A 12P 1PM 2PM 3PM 4PM 5PM
Sky (%).........35 30 25 20 25 35 40 50 60 70 70 75
Weather cov..... ISO SCT SCT SCT NUM NUM NUM SCT
Weather type.... RW RW RW RW RW RW RW RW
Tstm cov........ ISO ISO SCT SCT SCT SCT SCT SCT
CWR.............0 0 0 0 0 0 10 10 10 10 10 10
Chc of pcpn (%).0 10 10 10 20 30 40 50 60 60 60 40
Chc of thdr (%).0 0 0 10 10 10 30 30 30 40 40 40
Temp............45 44 48 54 60 63 64 65 64 63 62 59
RH..............73 76 71 57 46 41 38 35 35 35 41 35
20 FT wind dir..S S S SW SW SW SW SW SW SW SW SW
20 FT wind spd..3 3 4 6 7 10 12 8 8 9 12 12
20 FT wind gust.4 4 6 7 10 14 17 12 12 13 17 17
Ridge wind dir..S S S SW SW SW SW SW SW SW SW SW
Ridge wind spd..10 10 10 10 15 15 20 15 15 15 20 20
Mix hgt (kft)...0.1 0.1 0.1 1.0 2.5 5.0 7.0 8.0 9.0 7.0 5.5 3.0
Transp wind dir.SW SW SW SW W SW W SW SW SW SW SW
Transp wind spd.9 8 9 12 14 17 20 18 18 16 20 20
SDspl kt-ft/10001 1 1 9 29 78 119 129 141 95 90 54
.TONIGHT...
Sky/weather.........Mostly cloudy (65-75 percent) then becoming
partly cloudy (30-40 percent). Isolated
thunderstorms early in the evening. Scattered
rain showers in the evening.
CWR.................3 percent.
Chance of pcpn......30 percent.
Chance of thunder...23 percent.
Min temperature.....Around 45.
Max humidity........70 percent.
Wind (20 ft)........South winds 7 to 12 mph with gusts to around 17
mph until 2000. Light after 2400. Gusty and
erratic winds expected near thunderstorms early
in the evening.
Ridgetop wind.......South 15 to 20 mph until 2000, then around 10
mph.
Mixing height.......1000 ft AGL until 2000.
Transport winds.....Southwest 12 to 20 mph until 2100, then south 9
to 10 mph.
Smoke dispersal.....Fair until 1900. Poor after 2000.
TIME (MDT) 6PM 7PM 8PM 9PM 10P 11P MID 1AM 2AM 3AM 4AM 5AM
Sky (%).........75 70 70 60 45 40 35 35 30 30 25 20
Weather cov.....SCT SCT SCT SCT SCT SCT
Weather type....RW RW RW RW RW RW
Tstm cov........ISO ISO ISO
CWR.............0 0 0 0 0 0 0 0 0 0 0 0
Chc of pcpn (%).30 30 30 30 30 30 0 0 0 0 0 0
Chc of thdr (%).20 20 20 10 10 10 0 0 0 0 0 0
Temp............58 55 53 50 49 49 47 47 46 46 46 46
RH..............39 47 49 57 61 63 66 66 63 63 63 63
20 FT wind dir..SW S SW SW SW S SE SE S S S S
20 FT wind spd..12 7 6 5 4 4 4 4 4 4 4 4
20 FT wind gust.17 10 7 6 6 6 6 6 6 6 6 6
Ridge wind dir..SW S SW SW SW S SE SE S S S S
Ridge wind spd..20 15 10 10 10 10 10 10 10 10 10 10
Mix hgt (kft)...2.5 1.0 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1
Transp wind dir.SW S W SW S S S S S S S S
Transp wind spd.20 15 12 10 9 9 9 9 9 9 9 9
SDspl kt-ft/100041 13 1 1 1 0 0 0 0 1 0 0
.MONDAY...
Sky/weather.........Mostly sunny (25-35 percent).
CWR.................0 percent.
Chance of pcpn......10 percent.
Chance of thunder...13 percent.
Max temperature.....Around 70.
Min humidity........20 percent.
Wind (20 ft)........Light winds until 1100, then southwest 9 to 12
mph with gusts to around 17 mph. Gusty and
erratic winds expected near thunderstorms in
the afternoon.
Ridgetop wind.......South 10 to 15 mph until 1200, then southwest
around 20 mph.
Mixing height.......10000 ft AGL after 1200.
Transport winds.....Southwest 9 to 16 mph until 1100, then west 18
to 24 mph.
Smoke dispersal.....Poor until 1000. Excellent after 1200.
TIME (MDT) 6AM 7AM 8AM 9AM 10A 11A 12P 1PM 2PM 3PM 4PM 5PM
Sky (%).........20 25 5 5 5 15 25 35 40 50 45 40
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 (%).0 0 0 0 0 0 10 10 10 10 10 10
Chc of thdr (%).0 0 0 0 0 0 10 10 10 10 10 10
Temp............45 46 49 52 60 63 66 67 68 69 69 68
RH..............70 68 62 54 43 34 27 23 21 21 20 21
20 FT wind dir..S S S SW SW SW SW SW SW SW SW W
20 FT wind spd..4 4 4 5 6 9 11 12 11 11 11 11
20 FT wind gust.6 6 6 6 10 13 16 17 16 16 16 16
Ridge wind dir..S S S SW SW SW SW SW SW SW SW W
Ridge wind spd..10 10 10 10 15 15 20 20 20 20 20 20
Mix hgt (kft)...0.1 0.1 0.5 1.0 3.0 5.5 8.5 9.0 9.5 10 10 9.5
Transp wind dir.S S SW SW SW W W W W W W W
Transp wind spd.9 9 9 10 16 21 24 23 22 21 20 18
SDspl kt-ft/10001 1 2 10 42 103 177 180 182 183 168 153
.FORECAST DAYS 3 THROUGH 5...
.TUESDAY...
Mostly clear. Lows in the upper 40s. Highs in the mid 70s. Light
winds.
.WEDNESDAY...
Mostly clear. Lows around 50. Highs in the mid 70s. Light winds.
.THURSDAY...
Partly cloudy. Lows in the upper 40s. Highs in the lower 70s.
Southwest winds around 7 mph.
$$
Forecaster...Lowe
Requested by...E Folts
Type of request...WILDFIRE
.TAG 2520068.0/RIW
.DELDT 08/17/25
.FormatterVersion 2.0.0
.EMAIL ebf124@gmail.com,laura_dooley@nps.gov