172
FXUS65 KTFX 151422
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
822 AM MDT Tue Jul 15 2025

.KEY MESSAGES...

 - Precipitation continues across the region today, with the coolest
   temperatures across North-central Montana.

 - Temperatures trend closer to normal toward the weekend, with a
   few showers and thunderstorms Thursday near the Hi-Line.

 - At least a low-end risk for showers and thunderstorms each
   afternoon and early evening Friday through Sunday.

&&

.UPDATE...

Morning Update has been published, with the primary adjustment
being to decrease temperatures several degrees across Southwest
Montana where the cold front has already pushed through this
morning and low stratus has filtered through valleys. Otherwise
PoPs were adjusted to reflect latest Hi-Res and radar trends.
Changed precipitation, mainly north of the Montana Hwy 200
corridor, over to predominately stratiform in nature through the
day today; with a mixture of stratiform and showery precipitation
south of this line. Remainder of the forecast remains on track,
with a cool and wet mid-July day for those areas north of the I-90
corridor. - Moldan


&&

.DISCUSSION...
/Issued 521 AM MDT Tue Jul 15 2025/

 - Meteorological Overview:

Sharp upper level troughing within a northwesterly flow aloft will
continue its approach this morning before passing overhead today and
exiting eastward tonight. At the surface the cold front has already
moved into Southwest Montana, with gusty northerly winds behind the
front ushering in well below average temperatures. Elevated
instability has resulted in showers and thunderstorms in addition to
the lower level stratiform type of precipitation across northern
areas so far this morning. A mix of stratiform and showery
precipitation is forecast to continue today across northern areas as
forcing for ascent continues. The coldest air aloft moves in this
morning, with 700mb temps dropping to -2 to -4C on the east side of
Glacier NP. Hence, snow levels look to briefly fall to the 7,000-
8,000ft range this morning. Accumulating snow looks to be reserved
for peaks, however.

Further southwest the concern for today will be for a marginal risk
of severe thunderstorms near the Idaho border. Forecast soundings
show sufficient shear for a few loosely organized clusters capable
of large hail and gusty winds this afternoon and early evening south
of Ennis between Monida Pass and West Yellowstone.

As this system moves away late tonight into Wednesday morning, some
patchy fog will be possible, especially in areas where skies are
quick to clear. Temperatures during the day Wednesday begin to trend
a touch warmer, but still look to be well below average.

A zonal to slightly northwesterly flow aloft continues heading into
Thursday, with a weak wave passing across northern areas in the
afternoon. This should result in a few showers and thunderstorms
near the Hi-Line.

Thereafter guidance struggles with the specifics of the pattern
Several waves within a zonal to slightly northwesterly flow aloft
look to pass across the Northern Rockies Friday into early next
week, but the timing of any individual wave is uncertain still.
Temperatures look to trend closer to normal for this weekend, but
there is growing confidence in another cooler spell for the middle
of next week. -AM


 - Forecast Confidence & Scenarios:

Today:

High resolution guidance has been less bullish with lowering snow
levels across eastern Glacier NP compared to coarser counterparts in
BUFKIT soundings. Given the forecast cooler temperatures aloft in
most guidance, I leaned toward the lower snow level solution for
today, which resulted in at least a few inches on the highest peaks
of eastern Glacier NP.

The other point of uncertainty for today will be how much we warm on
the plains (If there is any warming at all). Northerly winds
continue today and with precipitation continuing through most of the
day, there is a realistic solution where there is nearly zero
warming through the day.


Late week into the middle of next week:

Deterministic guidance does agree that there will be a zonal to
slightly northwesterly flow aloft across the Northern Rockies Friday
into the weekend. Although there is agreement in the general pattern
setup, there is not a lot of agreement on the timing of any embedded
waves traversing this flow. Each wave will be capable of producing
scattered showers and thunderstorms. The when and where for each
wave remains uncertain.

Heading toward early next week, cluster guidance reveals better
agreement on the evolution of the pattern, with around 90% of
ensemble members favoring a period of troughing. This would result
in another cooler period, with increased chances for rain. -AM

&&

.AVIATION...
15/12Z TAF Period

Mountain obscuring low clouds and rain will be common through the
day today across the region. Showers and a few thunderstorms will be
around, especially in areas that remain clear today or at least
briefly clear this afternoon. Breezy northerly to northeasterly
winds continue for most areas through the day. -AM


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

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  53  46  70  48 / 100  70  10   0
CTB  52  40  67  46 / 100  20  10   0
HLN  58  47  75  49 /  90  70  10   0
BZN  67  47  75  45 /  80  80  20   0
WYS  76  40  75  37 / 100  70  10   0
DLN  69  46  76  45 /  60  40  10   0
HVR  60  46  70  48 /  90  50  10   0
LWT  53  43  63  43 / 100 100  40   0

&&

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

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