409
FXUS65 KTFX 090028
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
628 PM MDT Fri Aug 8 2025

.KEY MESSAGES...

 - Another breezy day is expected in the Havre and Lewistown areas
   on Saturday, along with a few showers in these areas.

 - Afternoon temperatures will trending back closer to normal
   starting on Sunday, with low chances for precipitation each
   day.

&&

.UPDATE...
Updated forecast is out for this evening. Only adjustment was to
increase pops in the Havre area, where light showers are more
numerous this evening. Otherwise, the chance for lightning is on
the low side, and QPF amounts will also be low tonight. Breezy
northwest winds this evening will make it feel a bit chilly.
Otherwise, the rest of the forecast is on track. Brusda

&&

.DISCUSSION...
/Issued 300 PM MDT Fri Aug 8 2025/

While the previous discussion from the previous shift remains on
track, recent radar trends have been to show numerous widespread
light rain showers across North Central Montana. While most of
these should be light, a few training showers could result in a
tenth of an inch or so through the afternoon. For more information
on the rest of the day and through next week, please see the
Previous Discussion section below. Ludwig

&&

.AVIATION...
09/00Z TAF Period

Light rain showers will mostly affect North Central MT through
about 06z on Saturday. An isolated lightning strike is possible,
but the probability is low. Breezy winds this evening will
diminish in most areas overnight, but do expect winds to increase
once again on Saturday over North Central MT. After 08z, do expect
skies to clear out a bit across the CWA. Brusda

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

&&

.PREV DISCUSSION...
/Issued 1151 AM MDT Fri Aug 8 2025/

 - Meteorological Overview:

Stout upper level troughing continues to pivot through the Northern
Rockies early this morning. Cooler air aloft is still resulting in
some elevated instability across the region, especially over the
plains. Forcing from the trough swinging through has been and will
be more than sufficient to tap into this instability and as a
result, showers and isolated thunderstorms look to continue
through the into the mid-morning in tandem with a more stratiform
rain, but slowly shift focus toward the Havre and Lewistown
areas. A briefly stronger gust cannot be ruled out in any
thunderstorm that manages to form the remainder of the overnight.

The coolest air aloft moves through early this morning associated
with the core of the upper level disturbance. A few instances of
light snow on the higher peaks of the Little Belts, Big Belts,
Tobacco Roots seems reasonable this morning given the core of the
coldest sub-zero H7 temperatures swinging through these areas.
Cold prone valleys, such as the Big Hole Valley, are likely to see
overnight lows in the 20s and 30s this morning.

Increased westerly to northwesterly mid level flow in the mid levels
behind the departing troughing today will allow for a breezy day. By
the afternoon, mixing should support sustained winds near or in
excess of 20 mph for most areas, with gusts in to the 30s or higher.
Although much cooler air will linger at the surface, sufficiently
cool air aloft over the plains and adjacent areas will support
afternoon and evening showers and a few thunderstorms. Forecast
soundings show little in way of instability over most areas, with
areas near Blaine county having the best chance to exceed 500 m2/s2
sfc-based CAPE in the afternoon. DCAPE appears minimal though in
this area, so small hail is the primary concern should a stronger
thunderstorm form. Given the core of the upper disturbance nearby in
the afternoon Friday, I cannot rule out an instance or two of a cold
air funnel.

Looking toward tonight, northwesterly mid level flow remains
rather impressive over the plains. Areas downwind of island ranges
of North- central and Central Montana are likely to remain gusty
through the night into Saturday. The most aggressive guidance
features a few instances of gusts near 50 kts immediately
downwind of terrain in Fergus county. Given the low member share
with gusts this high as well as the very small spacial extent of
these potential gusts, no High Wind Watches are being considered
at this time.

Another breezy day will be in store Saturday in the Lewistown and
Havre areas as northwesterly mid and upper level flow level flow
remains on the stronger side behind the departing troughing. Weak
and rather shallow instability in the aforementioned areas will
promote a few showers and perhaps an isolated thunderstorm in the
afternoon. Worth noting is that there will be the potential for a
period of wildfire smoke in the Havre area and potentially adjacent
areas as well, sourced from fires well north/north-northeast in
Canada.

Deterministic guidance keeps the northwesterly flow intact going
into early next week, downstream of an eastern Pacific ridge. This
looks to allow temperatures to trend closer to normal, with largely
low chances for precipitation. Deterministic guidance does feature a
few waves progressing downstream of the ridge within the
northwesterly flow aloft which may bring low-end chances for rain or
a brief local cooldown, but the timing of any one specific wave is
low confidence at this range.

Looking further into next week, ensemble averages do favor some
troughing by the end of the week, which would allow for at least
a low-end chance for precipitation. -AM

 - Forecast Confidence & Scenarios:

The greatest deal of uncertainty has to do with how strong gusts
become downwind of island ranges in Central/North-central MT
tonight. 00Z EC and GFS guidance, among others, features a H7 jet
that approaches 50 kts tonight in the vicinity of Fergus county.
Although ridgetop stability is not present, there is still concern
for these stronger winds to be translated to the surface.
especially from any showers or decaying showers in the area
leftover from daytime hours. The chance for a 55 mph gust in lee
of terrain in Fergus county is roughly 20% at this time.

Otherwise the other source of uncertainty has to do with how the
pattern plays out next week. As mentioned prior, troughing is
favored in the ensemble mean by late next week. Specifics will
remain murky til deterministic guidance becomes more consistent
resolving how the pattern unfolds. -AM

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  53  76  53  83 /  30  40  20   0
CTB  51  73  51  79 /  50  30  20  10
HLN  51  78  53  84 /  10  10  10   0
BZN  44  77  47  83 /  10  10  10   0
WYS  33  70  34  77 /   0  10  10  10
DLN  40  73  43  80 /   0  10   0   0
HVR  55  75  53  83 /  80  40  10  10
LWT  50  71  49  77 /  50  20  10  10

&&

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

&&

$$
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