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FNUS75 KTFX 211329
FWSTFX

Spot Forecast for Headwaters Jam...Jefferson County Emergency Management
National Weather Service Great Falls MT
729 AM MDT Tue Jul 21 2026

Forecast is based on forecast start time of 1000 MDT on July 22.
If conditions become unrepresentative...contact the National Weather
Service.

.DISCUSSION...

.Initial concern this week will be for slow moving showers and
thunderstorms Wednesday afternoon and evening across Southwest
Montana, which will be capable of producing heavy rainfall. Should
a thunderstorm develop near or over the festival, there would be
concern for muddy fields and even localized flash flooding.

The risk for slow moving thunderstorms persists into Thursday,
though at this time Wednesday is the day of greater concern for
excessive rainfall leading to flash flooding. The drier air at the
surface may increase instances of strong, gusty winds near
showers and storms, with brief gusts over 50 mph with the stronger
storms.

The region begins to trend warmer and drier Friday, though a
lingering shower or thunderstorm cannot be completely ruled out.
Friday is also looking to be on the breezier side. The probability
for a max gust in excess of 40 mph Friday is roughly 40%.

That risk for gusty winds continues into Saturday, with a similar
probability for a 40 mph gust. Saturday looks to be the hottest
day at the festival. That said, temperatures each day look to warm
to at least 90, which raises concerns for heat related illness
for those who are not properly hydrated and taking breaks.


.WEDNESDAY...

Sky/weather.........Partly sunny (50-60 percent). Chance of showers
                    and thunderstorms in the afternoon.
Chance of pcpn......60 percent.
Chance of lightning.40 percent.
Max temperature.....88-93.
Min humidity........31-36 percent.
Surface winds (mph).North around 5 mph, with gusty and erratic winds near
                    any shower or storm
Pcpn amount.........0.04 inches, locally higher amounts beneath thunderstorms
Snowfall amount.....0.0 inches.
Visibility..........10.

.WEDNESDAY NIGHT...

Sky/weather.........Mostly cloudy (75-85 percent). Showers likely
                    and chance of thunderstorms in the evening,
                    then chance of showers overnight.
Chance of pcpn......70 percent.
Chance of lightning.30 percent.
Min temperature.....60-65.
Max humidity........72-77 percent.
Surface winds (mph).West winds up to 5 mph in the evening becoming
                    light and variable, with gusty and erratic winds near
                    any shower or storm
Pcpn amount.........0.08 inches, locally higher amounts beneath thunderstorms
Snowfall amount.....0.0 inches.
Visibility..........6 in the evening.

.THURSDAY...

Sky/weather.........Mostly sunny (35-45 percent). Slight chance of
                    showers through the day. Slight chance of
                    thunderstorms in the afternoon.
Chance of pcpn......20 percent.
Chance of lightning.24 percent.
Max temperature.....89-94.
Min humidity........27-32 percent.
Surface winds (mph).Light winds, with gusty and erratic winds near any shower or storm
Pcpn amount.........0.00 inches.
Snowfall amount.....0.0 inches.
Visibility..........MISSING.

.FORECAST DAYS 3 THROUGH 7...
.FRIDAY...
Mostly clear. Lows in the lower 60s. Highs in the upper 90s.
Southwest winds around 15 mph gusting to 35 mph at times.
.SATURDAY...
Mostly clear. Lows in the lower 60s. Highs in the upper 90s.
Southwest winds around 15 mph gusting to 35 mph at times.
.SUNDAY...
Mostly clear. Lows in the lower 60s. Highs in the mid 90s. West
winds around 10 mph.

$$
Forecaster...Greely
Requested by...Doug Dodge
Type of request...OTHER
.TAG 2617809.0/TFX
.DELDT 07/21/26
.FormatterVersion 2.0.0
.EMAIL ddodge@jeffersoncounty-mt.gov, tfx.ops@noaa.gov