330
FXUS65 KTFX 051918
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
118 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.

&&

.DISCUSSION...

 - 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...
05/18Z TAF Period

While VFR conditions prevail across the North Central and
Southwestern Montana as of late this morning, showers and
thunderstorms will develop across the area over the next few hours
as we head into the afternoon. These SHRA and TSRA are generally
expected to be along and east of a line from KHVR to KBZN, though
a pop up SHRA/TSRA will be possible at any TAF site today. East of
the KHVR to KBZN line will be the best chance for gusty outflow
winds and some hail aloft and at the surface, particularly in the
KLWT vicinity and locations to the east and southeast. SHRA and
TSRA will clear the area around 9z Sunday, and aside from any
potential fog VFR conditions are expected to return to the area.
Ludwig

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  75  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  74  37  79 /  20   0   0   0
DLN  43  79  46  85 /  10   0   0   0
HVR  50  82  52  86 /  40  20  20   0
LWT  47  75  49  80 /  40  10  20   0

&&

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

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