484
FXUS65 KTFX 060249
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
849 PM MDT Sat Jul 5 2025

.KEY MESSAGES...

 - A few stronger thunderstorms this afternoon, mainly over the
   eastern plains.

 - Another opportunity for a stronger thunderstorm or two across the
   Hi-Line Sunday afternoon.

 - Trending warmer and drier early next week.

&&

.UPDATE...

8:45 PM UPDATE

Slight adjustments were made to the precipitation chances and
winds in the next 24 hours based on updated NBM guidance.
Otherwise, no major changes to the going forecast.  -thor


6:20 PM UPDATE
Given that the main threat for severe weather has ended for
Fergus and Blaine counties, the severe thunderstorm watch has been
cancelled. A couple thunderstorms are expected to continue their
way across Fergus county with the potential for some stronger wind
gusts. However, gusts over 50 mph are not expected from here on
out.

Additionally, given the latest trends, the chance for fog was
added to the forecast for tonight. At this point in time,
widespread dense fog is not expected so no products are needed at
this time. However, motorists should be prepared for sudden
reductions in visibility during the overnight and early morning
hours.  -thor

&&

.DISCUSSION...
/Issued 624 PM MDT Sat Jul 5 2025/

 - Meteorological Overview:

Troughing well ahead of a building ridge across the eastern Pacific
will continue to support showers and thunderstorms this afternoon
and evening as it marches eastward out over the plains. Areas in and
adjacent to Blaine/Fergus county appear to have the greatest risk
for a strong to severe thunderstorm this afternoon. The best
thermodynamic and kinematic environments overlap here, which will
yield an initial large hail threat (Wind to a lesser extent)
before storms move east of the area later this afternoon and
evening. Given the proximity of the mid-level low over portions of
the Hi-Line and vicinity this afternoon, a brief funnel from a
more robust thunderstorm does not seem unreasonable.

The building ridge shifts eastward toward the west coast heading
into Sunday. One final wave cascading through the building ridge
clips the Hi-Line Sunday afternoon, which will yield at least a low-
end chance for thunderstorms. Forecast soundings show an environment
marginally conducive to supercells straddling the Canadian border
within the West-Northwest flow aloft. High resolution guidance is
split as to whether a rogue supercell or two will form north/south
of the border, with each solution seeming plausible at this point.

The ridge finally builds in for early this upcoming week, which will
promote a drying and warming trend through mid week or so. A more
zonal to slightly southwesterly flow develops briefly mid to late
week, which will re-introduce low-end shower and thunderstorms
chances. Ensembles favor another period of ridging then attempting
to build in toward next weekend, though specifics become murky at
that range. -AM

 - Forecast Confidence & Scenarios:

The point of greatest uncertainty in the next few days is where
exactly a stronger thunderstorm or two develops Sunday - whether
along the Hi-Line or further north into Canada. Guidance is split
between these solutions, and we will likely need to resolve finer
scale details that will play out through the day today before
getting a better idea as to where the greatest risk will ultimately
settle Sunday. If a rogue supercell or two were to form near the Hi-
Line, large hail and gusty winds will be the greatest concern.

Otherwise, confidence is high in a warming and drying trend heading
into next week with a brief cooldown mid-late week as precipitation
chances sneak back into the forecast. Larger spread exists in the
temperatures forecast into next weekend, as ridging attempts to
build in. A ridge that builds in faster/stronger would result in a
quicker warming trend while a slower to build/lower amplitude ridge
would favor slower warming. -AM

&&

.AVIATION...
06/00Z TAF Period

A few showers and thunderstorms will be near KHVR, KLWT and KWYS
initially this evening, with these moving east of the area by
04z. Otherwise, VFR conditions prevail across the area with
decreasing clouds overnight, though clearing may provide some
potential for patchy fog near the KWYS and KHVR terminals. Surface
winds primarily from the north to northwest this evening will
decrease overnight with generally light west to southwest winds
Sunday morning, turning more northwesterly again Sunday afternoon.
Hoenisch

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

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  50  81  52  86 /  20   0   0   0
CTB  46  73  47  81 /  10  20   0   0
HLN  51  82  53  87 /  20   0   0   0
BZN  45  82  49  89 /  30   0   0   0
WYS  35  73  37  79 /  20   0   0   0
DLN  42  79  46  85 /  10   0   0   0
HVR  50  80  52  86 /  40  20  20   0
LWT  46  75  49  80 /  40  10  20   0

&&

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

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