921
FXUS65 KTFX 222014
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
214 PM MDT Wed Jul 22 2026

.KEY MESSAGES...

 - Showers and thunderstorms are expected each afternoon through
   Saturday.

 - Isolated thunderstorms in Southwestern Montana have the
   potential to produce localized flash flooding this
   afternoon/evening.

 - Temperatures will gradually warm up through Saturday and stay
   warm through early next week.

&&

.DISCUSSION...

 - Meteorological Overview:

This afternoon there is an upper-level ridge over North-central,
Central, and Southwestern Montana. An upper-level shortwave will
move through the upper-level flow and bring shower and thunderstorms
primarily south of I-90 Wednesday afternoon and evening. Due to an
increase in monsoonal moisture the thunderstorms will produce heavy
rainfall. There is a lack of steering flow so the thunderstorms will
also be slow moving. This has the potential to lead to some
localized flooding. See the Hydrology section for details. On
Wednesday isolated and showers have the potential to make it further
north but stay south of an Augusta to Great Falls to Lewistown line.

On Thursday the upper-level ridge remains over North-central,
Central, and Southwestern Montana. Another upper-level shortwave
moves through the flow. This will bring another day of hot weather
with isolated showers and thunderstorms. On Friday the upper-level
ridge remains over North-central, Central, and Southwestern Montana.
This will increase temperatures to well-above seasonal averages.
Winds will increase due to low-level and mid-level winds increasing.
This will dry out the area and bring elevated fire weather
conditions to North-central Montana. See the Fire Weather Section
for details. On Saturday the upper-level ridge remains over North-
central, Central, and Southwestern Montana. It will be the hottest
out of this forecast period across the area on Saturday with well-
above seasonal average temperatures. On Sunday a weak upper-level
trough moves through which will slightly cool down temperatures and
bring some windy conditions to the area. On Monday and Tuesday the
upper-level ridge remains over North-central, Central, and
Southwestern Montana. This will allow warm and dry conditions to
persist. -IG

 - Forecast Confidence & Scenarios:

On Wednesday there is a 40 - 60% chance for thunderstorms across
Southwestern Montana. On Wednesday there is a 15 - 35% chance for
thunderstorms across most of North-central and Central Montana. On
Thursday there is a 20 - 40% chance for thunderstorms across North-
central, Central, and Southwestern Montana. On Friday there is a 25 -
 30% chance for thunderstorms across Southwestern Montana. On
Saturday there is a 25 - 50% chance for thunderstorms across
Southwestern Montana.

On Friday there is a 20 - 60% chance for high temperatures of 100
degrees or greater across most of North-central Montana. On Saturday
there is greater than a 60% chance for high temperatures of 100
degrees or greater across North-central Montana. On Saturday across
portions of Fergus, Hill, and Blaine Counties there is a greater
than a 70% chance for high temperatures greater than 105 degrees.
This combined with low temperatures in the upper 60s to low 70s
across portions of Fergus, Hill, and Blaine County on Saturday and
Sunday morning led to an Excessive Heat Watch being issued for those
areas from Friday afternoon through Sunday evening. On Saturday
there is a 40 - 60% chance for high temperatures of 100 degrees or
greater from the Helena Valley through the Canyon Ferry area to
Townsend to the Three Forks to Bozeman area. -IG

&&

.AVIATION...
22/18Z TAF Period

The forecast area sits on the northern edge of monsoonal moisture
with sporadic restrictions possible for terminals along and south
of the I-90 corridor late this afternoon and evening as showers
and storms cross the area. Heavy rainfall associated with the
showers may briefly produce IFR conditions where downpours
directly impact sites. For the remainder of the area, the wave
will bring mixed VFR decks with the Hi-Line remaining mostly clear
for the period. Light winds will be prone to normal diurnal
trends and terrain funneling, as well as convectively driven
variability with gusty, erratic winds in the presence of showers
and storms. Sites that do see rain have an increased chance of
brief IFR/LIFR conditions in low stratus and fog late tonight and
early Thursday morning. -MEC

&&

.FIRE WEATHER...

Hot, dry, and windy conditions are expected through the weekend
which will lead to elevated fire weather concerns across much of the
region. The main limiting factor will be the potential for wetter
showers and thunderstorms both this afternoon/evening and
Thursday.

There is a concern that most of the wetter showers will not make it
north of a line between Helena and White Sulphur Springs which would
put North-Central Montana at a much higher risk for elevated fire
weather conditions through the weekend. Additionally, if the wetter
storms on Wednesday and Thursday are unable to materialize, or they
are a lot more isolated than what is currently expected, then that
could also elevate fire weather concerns for Central and Southwest
Montana.

As it stands there is a generalized concern for elevated fire
weather conditions starting on Friday but much of the threat will
not be determined until Thursday evening when it becomes clear which
locations were able to pick up some wetting rain ahead of the
incoming hot, dry, and windy conditions.  -IG/thor

&&

.HYDROLOGY...

Today the Weather Prediction Center (WPC) has issued a Slight
Risk (15% chance for flash flooding within 25 miles of a point)
for flash flooding across most of Southwestern Montana. Between
the I-90 corridor and a line between Augusta to Great Falls to
Lewistown WPC has issued a Marginal Risk (5% chance for flash
flooding within 25 miles of a point)for flash flooding today. In
addition across the mountains of Southwestern Montana there is a
50 - 70% chance for rainfall rates in excess of one half inch per
hour today. In addition there is around a 50% chance for rainfall
rates in excess of three quarter of an inch per hour across the
mountains of Southwestern Montana today. There is a 20 - 40%
chance for an inch of rain or greater across the mountains of
Southwestern Montana today. As a result a Flash Flood Watch
remains in effect for the mountains south of I-90 through midnight
tonight. -IG

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  62  96  63  98 /  10  10  20   0
CTB  58  94  62  93 /  10  10  10   0
HLN  62  94  63  97 /  30  20  10   0
BZN  58  91  60  97 /  50  20  20   0
WYS  50  82  50  87 /  70  30  20   0
DLN  55  87  57  92 /  60  20  20   0
HVR  60  99  64 102 /   0  10  10   0
LWT  57  90  60  95 /  10  30  10  10

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
Extreme Heat Watch from Friday afternoon through Sunday evening
for Bears Paw Mountains and Southern Blaine-Fergus County below
4500ft-Hill County-Northern Blaine County.

Flood Watch until midnight MDT tonight for Gallatin and Madison
County Mountains and Centennial Mountains-Northwest Beaverhead
County-Ruby Mountains and Southern Beaverhead Mountains.

&&

$$
http://www.weather.gov/greatfalls