430
FXUS65 KTFX 162335
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
435 PM MST Sun Nov 16 2025

Aviation Section Updated.

.KEY MESSAGES...

 - Patchy dense fog is possible along the Hi-Line tonight into
   Monday morning.

 - Periods of light mountain snow and lower elevation rain are
   possible Monday through Wednesday before drying out for the
   second half of the week.

 - Above normal temperatures will persist through the first half
   of the week before cooling down to more seasonal temperatures
   by the end of the week.

&&

.DISCUSSION...
/Issued 238 PM MST Sun Nov 16 2025/

 - Meteorological Overview:

Weak southwesterly flow aloft develops today and tonight,
resulting in an increase in mid- and higher level cloudiness for
all areas with scattered areas of rain showers and some light
mountain snow developing along the Continental Divide and over
Southwest Montana. Winds will generally be on the light side and
will combine with lingering surface moisture for nighttime and
early morning patchy fog development over the next couple of days,
mostly near the Milk River Valley.

Periods of lower grade, mostly mountain rain and snow will
continue along and ahead of a weak Pacific trough due to pass
through the Northern Rockies sometime on Wednesday. H700
temperatures remain around -5C before falling to around -10C near
the trough axis. Theoretically, this would bring snow levels down
to the valleys and the plains on Wednesday, but precipitation
amounts look negligible by then.

Another trough moves into the western CONUS for the second half
of the workweek, but the main low pressure center looks to shear
off towards the southwestern CONUS, leaving drier conditions for
the state of Montana. The upper level jet moves over the Northern
Rockies Friday into next weekend and sends a broad trough that
will bring periods of mountain snow and a return to windy
conditions. - RCG


 - Forecast Confidence & Scenarios:

Fog Tonight:

There is a 60% chance for fog developing along the Hi-Line again
tonight into tomorrow morning. Visibility reductions down to 1
mile are expected with patches of dense fog with visibility less
than 1/4 mile possible, particularly along the Milk River Valley
including Havre. There is some uncertainty in how far west the
fog will develop. Currently there is a 40% chance for fog
developing as far west at Chester and a 20% chance as far west as
Cut Bank. Regardless, the main concern overnight will be
visibility impacts to US 2. The potential exists that a Dense Fog
Advisory may be needed at some point but, for now, that decision
will be held off until evening model runs arrive to help confirm
or deny whether widespread visibilities less than 1/4 mile are
possible.


Rain/Snow Monday through Wednesday:

The system expected Monday through Wednesday continues to err on
the lighter side of precipitation amounts with only a 30-50%
chance of precipitation amounts greater than 0.1" across the
mountains and a 10-30% chance across lower elevations. Snow
amounts are likely to be less than 2 inches and reserved for the
highest peaks above 8000ft. There is still a chance that some
foothill snowflakes could be observed Wednesday morning but with
this system being as dry as it is, there is low confidence in this
scenario playing out. Overall, significant impacts are not
expected through the first half of the week.


Rain/Snow this Weekend:

Drier conditions are expected for the second half of the week with
the next chance for unsettled weather arriving this weekend as an
upper level trough makes it way into the western CONUS. As it
stands, the track of this trough means that there is a chance
most of the lower elevations may get missed entirely by the
precipitation with only the mountains along the Continental Divide
receiving noticeable amounts. Should the track shift at all to
the north, there could be some more impacts of note for
southwestern Montana but as of now the concern for this system is
relatively low. -thor


&&

.AVIATION...
17/00Z TAF Period

VFR conditions will prevail across all terminals during this TAF
Period except for at the KHVR terminal. At the KHVR terminal
between 17/09Z and 17/18Z there is greater than a 70% chance for
fog to form and reduce visibility to at least IFR levels. At the
KCTB terminal between 17/09Z and 17/18Z there is a 35% chance for
fog to form. Due to there being a low chance for fog to form plus
uncertainty on how far west fog will spread fog/mist was left out
of the KCTB TAF for this issuance. During the majority of this
TAF Period there will be periodic mountain obscuration across
Southwestern Montana. -IG

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

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  39  60  36  53 /   0  10  10  10
CTB  33  57  30  49 /  10  10  10  10
HLN  36  56  35  53 /   0  10  10  10
BZN  34  55  33  52 /  10  10  20  10
WYS  30  41  27  43 /  40  60  40  20
DLN  34  53  31  51 /  10  10  10   0
HVR  31  52  31  47 /  10  10  10  10
LWT  37  57  33  52 /  10  10  20  10

&&

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

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