061
FXUS65 KTFX 270008
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
508 PM MST Tue Nov 26 2024

Aviation Section Updated.

.KEY MESSAGES...

-Areas of fog are likely to develop tonight across portions of north-
 central Montana, particularly across Hill and Blaine counties.

-Areas of light snow are expected Wednesday night through Saturday
 with potential for minor accumulations across north-central MT
 Wednesday night into Thursday

-Temperatures trend cooler for all areas later this week into the
 weekend.

&&

.DISCUSSION...
/Issued 505 PM MST Tue Nov 26 2024/

 - Meteorological Overview:

A northwesterly flow aloft sets up following the passage of the
trough axis tonight and continues through the upcoming weekend as
upper level ridging builds offshore of the west coast. A series of
shortwave disturbances cascade through the region in this flow with
the first arriving Wednesday night and additional waves moving
through the area later Thursday through Saturday. These are fairly
quick moving "Clipper" type disturbances with trajectories favoring
north-central MT for brief periods of light snow with passage of each
disturbance with most areas likely to see an inch or less of snow
accumulation. Each of these disturbances reinforces the cold
airmass/surface high pressure centered across the Canadian Prairies
with temperatures trending colder but the coldest of this airmass
looks to remain to the northeast with areas along the Hi-line
again most likely to see overnight temperatures near or below zero
later this week into the weekend.

 - Forecast Confidence & Scenarios:

Probabilities for fog with visibility less than 1 mile tonight is 50%
or higher from Toole county east through Blaine county and as far
south as Ft Benton in Chouteau county with hi-resolution model
ensembles highlighting areas from Havre through Big Sandy with an
80% probability of visibility to 1/2 mile or less.

The greatest risk for measurable snowfall with the clipper system
Wednesday night into Thursday morning will be across north-central
MT where probabilities for 1 inch or more snowfall amounts
are 40-50%.

Later this weekend into early next week, medium range model
ensembles broadly support upper level riding shifting inland across
the western US resulting in a trend toward drier and milder
conditions though some uncertainty continues on the timing
of the transition. Hoenisch

&&

.AVIATION...
27/00Z TAF Period

Expect passing clouds with a few light snow showers this evening.
Most of the snow showers should stay away from terminals, but some
tweaks might be necessary should a snow shower pass over. A few
hours of patchy fog are also possible in the Havre area on
Wednesday morning. The bigger concern is the potential snowfall
Wed night into Thur. Most of the snow will start after 00z Thu and
move from north to south through the CWA. More impacts from the
expected snowfall will be in the upcoming 6z Taf issuance.
Mountains/passes will be obscured at times through the period.
Brusda

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

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  14  33  10  29 /  10  10  70  10
CTB   6  21   1  20 /   0  10  70  10
HLN  22  37  19  36 /  10  10  40  10
BZN  16  34  13  33 /  10   0  30  10
WYS   6  26   8  24 /  30   0  50  30
DLN  13  33  12  33 /   0   0   0   0
HVR   2  21  -2  17 /   0  30  80  10
LWT  14  32   9  30 /  10  10  80  30

&&

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

&&

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