483
FXUS65 KTFX 291750
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
1150 AM MDT Sun Jun 29 2025

Aviation Section Updated.

.KEY MESSAGES...

- Generally dry conditions and seasonably warm temperatures
  are expected today before very warm to hot weather moves in for
  much of the upcoming workweek.

- Daily rounds of showers an thunderstorms return Tuesday evening
  and continue for the duration of the week.

&&

.UPDATE...
/Issued 900 AM MDT Sun Jun 29 2025/

Today it will be warm and mostly dry with isolated showers along
the Hi-Line this afternoon and evening. For the update
temperatures across North-central, Central, and Southwestern
Montana were increased to reflect the latest model guidance and
current trends. PoPs along the Hi-Line this afternoon and evening
were increased to reflect the latest hi-res model guidance. The
rest of the forecast is on track. -IG

&&

.DISCUSSION...
/Issued 900 AM MDT Sun Jun 29 2025/

 - Meteorological Overview:

Northwesterly flow aloft will maintain periods of variable
cloudiness, northwesterly surface breezes, and seasonably warm
temperatures today before upper level ridging brings the warmest
workweek so far this season. Daily rounds of shower and
thunderstorm activity will return by the middle of next week as
moisture and weak disturbances begin to compromise the ridge.
Afternoon temperatures peak in the lower to middle 90s on Tuesday
and Wednesday followed by slight cooling to finish out the week
due to cold frontal passages and overall increased moisture.

Low level moisture streams in ahead of an approaching shortwave
and attendant cold front on Wednesday and pushes precipitable
water values to the 0.75 to one inch mark. Bulk shear over 30 kts
should compliment the moisture and intense diurnal heating for at
least a marginal severe weather threat Wednesday afternoon and
evening with some storms producing strong, gusty winds, hail, and
brief downpours.

The cold front may temporarily confine the convective activity to
Central and Southwestern areas on Thursday, but a trough moves
into the Pacific NW and sends another shortwave and additional
moisture Friday into Saturday for more areawide rounds of showers
and thunderstorms. The increased moisture levels mentioned above
should result in more productive showers and storms with localized
heavy downpours heading into the weekend. Temperatures during
this time will trend a little closer to normal compared to
previous days with the extra moisture and cloud cover. - RCG

 - Forecast Confidence & Scenarios:

Building heat next week...

Ridging aloft will bring hot and dry days with most lower
elevation temperatures ranging from the upper 80s to the middle
90s Monday through Wednesday before shower and thunderstorm
activity begins to cool things during the second half of the week.
The heat risk will be greatest on Wednesday for locations
southeast of the highway 87 corridor between Great Falls and Havre
excluding the Lewistown area. These areas will not only see
afternoon highs in the 90s, but will also have a 60 to 80% chance
for low temperatures not falling below the 60 degree mark
Wednesday and Thursday mornings. Localized areas with major heat
impacts can be expected, although it will be only for a 24 to 36
hour period. No heat products are anticipated at this time, but
the situation will continue to be monitored.

Increasing shower and thunderstorm activity...

Moisture and subtle disturbances begin to undercut the upper
level ridge Tuesday afternoon and evening and bring at least
isolated shower and thunderstorm activity to Southwest and
portions of Central Montana. Showers and storms become more
widespread on Wednesday with a shortwave and cold front adding
wind shear to the unstable environment. Model guidance has
generally been on the lower side for CAPE values (mostly around
500 J/kg), but may be underplaying them a bit with lapse rates
looking steep at and above 8C/km. At the very least, there`s an
expectation marginally severe storms with localized strong, gusty
outflow winds due to dry sub- cloud layers. With precipitable
water values looking to approach an inch, hail and brief downpours
are also hazards to watch for.

The cold front may suppress most showers and storms to Southwest
Montana on Thursday, but this looks to be temporary with
southwesterly flow aloft and passing shortwaves bringing more
areawide shower and thunderstorm potential heading into the
weekend. There are some mesoscale uncertainties that need to be
resolved before getting into the finer details for thunderstorm
activity heading into the weekend, but there will be enough
moisture and instability to consider severe weather and localized
heavy rain. - RCG

&&

.AVIATION...
29/18Z TAF Period

With high pressure in place across North Central and Southwestern
Montana this afternoon, expect skies to remain mostly clear with
generally light winds out of the west to northwest. Ludwig

Refer to weather.gov/zlc for more detailed regional aviation
weather and hazard information.

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  81  51  89  57 /   0   0   0   0
CTB  78  49  86  53 /  10   0   0   0
HLN  83  52  90  59 /   0   0   0   0
BZN  83  47  93  54 /   0   0   0   0
WYS  77  35  85  40 /   0   0   0   0
DLN  79  46  89  52 /   0   0   0   0
HVR  81  50  90  56 /  10   0   0   0
LWT  74  48  84  55 /   0   0   0   0

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
None.
&&

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