230
FXUS65 KTFX 090437
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
937 PM MST Fri Nov 8 2024

Aviation Section Updated.

.KEY MESSAGES...

-Dry and mild conditions persist through Saturday with slightly
 cooler but still above average temperatures following early next
 week.

-A series of Pacific weather systems will bring increasing winds
 Sunday through Tuesday with locally strong winds possible late
 Monday.


-A more active weather pattern early next week will bring some
 light precipitation to the mountains Sunday with better chances
 Monday and Tuesday.

&&

.UPDATE...

No significant changes were needed with the update. A weakening
pressure gradient has allowed winds to relax across the plains a
bit. Aside from some patchy fog in valleys, the overnight period
looks to be benign across the region heading into a pleasant day
Saturday. Small tweaks were made to temperatures, otherwise no
changes were made this evening. -AM

&&

.DISCUSSION...
/Issued 842 PM MST Fri Nov 8 2024/

 - Meteorological Overview:

The upper level ridge in place across MT will gradually flatten
through the weekend with a weakening shortwave/Pacific disturbance
moving across the area Sunday ahead of a larger scale upper level
trough that shifts inland early next week. Daytime temperatures will
remain well above seasonal averages through Saturday with overall
quiet and dry conditions prevailing. Westerly flow aloft with
embedded moisture increases on Sunday as the the weakening Pacific
system moves across the area. Precipitation is fairly limited with
this initial system and focused primarily along the continental
divide and across southwest MT. Temperatures cool slightly on Sunday
and snow levels lower to 5000-6000 ft with potential for up to an
inch of snow (40-60%) for Marias Pass and Glacier NP while passes
further south along the divide and SW MT could see some snow
showers Sunday afternoon but with little or no accumulation.

 - Forecast Confidence & Scenarios:

Looking ahead to next week a more active weather pattern is on track
as a larger scale upper level trough moves onshore early next week
with a stronger Pacific cold front moving across the region between
Monday and Tuesday. Stronger SW flow aloft ahead of the trough and
surface low pressure emerging east of the Canadian Rockies on Monday
will lead to increasingly windy conditions, both along the Rocky Mtn
Front and eventually across north-central MT late Monday through
early Tuesday and in some SW MT valleys as south to southwest flow
is enhanced ahead of the front/upper trough Monday afternoon. On
Monday, there is a 50-70% chance for wind gusts in excess of 45 mph
along the Rocky Mtn Front and adjacent areas as well as areas
downwind of the Little Belts and through the Madison River Valley
and Norris Hill. For Monday night and Tuesday, much of north-central
and central MT has a greater than 50% risk for wind gusts in
excess of 45 mph with a 50% or higher risk of gusts in excess of
55 mph along the Rocky Mountain Front and east across Glacier
County as well as much of Judith Basin county.

Precipitation with the Monday/Tuesday system comes with a Pacific
frontal passage late Monday and with showers in the somewhat
unstable WNW flow that follows through Tuesday night. This again
favors areas along the continental divide and the mountains of SW
MT where there is a 60% or better probability for amounts of
0.25" or more while probabilities for 0.10" or higher precipitation
amounts at lower elevations range from less than 20% across the
north-central MT plains to 40-60% across the SW MT valleys. Snow
levels will be lower Monday night and Tuesday with periods of more
impactful snow possible across mountain passes, though there is
still some uncertainty with the timing and duration of snow during
this period.

Longer range model ensembles are in reasonable agreement with a
period of flat upper level ridging across the Northern Rockies
Wednesday and Thursday before the next larger scale trough
approaches from the west late next week/weekend. After cooling
back to seasonal averages briefly on Tuesday, temperatures are
likely to warm back above average Wednesday and Thursday before
trending down again next weekend. Hoenisch

&&

.AVIATION...
09/06Z TAF Period

VFR conditions prevail this TAF period. There is an outside chance
for Southwest Montana valley fog Saturday morning, but confidence
was too low to warrant mention at any site at this time. A
southerly to westerly wind will persist across the plains tonight
into Saturday, but will be on the lighter side. -AM

The KWYS TAF will not be issued until airport operations resume next
spring.

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

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  35  60  40  53 /   0   0   0  10
CTB  36  59  36  49 /   0   0   0  10
HLN  29  55  34  51 /   0   0   0  20
BZN  25  55  28  50 /   0   0   0  20
WYS  13  42  17  37 /   0   0  10  40
DLN  26  54  30  48 /   0   0   0  10
HVR  32  60  34  51 /   0   0   0  10
LWT  34  59  34  50 /   0   0   0  20

&&

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

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