Big Sky Resort

000
FXUS65 KTFX 312354
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
554 PM MDT Sat Oct 31 2026

Aviation Section Updated.

.KEY MESSAGES...

- Periods of dense fog and even some isolated instances of icing
  over elevated surfaces will continue through Sunday morning, 
  most widespread over central and north-central Montana.

- Precipitation becomes more widespread by Sunday, with
  accumulating snow most prevalent over the higher terrain of 
  southwest Montana Sunday night into Monday morning.

- Temperatures trend closer to average next week.

&&

.DISCUSSION...
/Issued 1220 PM MDT Sat Oct 31 2026/ 

 - Meteorological Overview:

Low level easterly flow continues to support low stratus and areas 
of dense fog development over central and north-central MT, while a 
moist southwesterly flow aloft overruns the cooler air mass and 
sends waves of light showers, sprinkles, and even some isolated 
instances of freezing drizzle. This general pattern will more or 
less persist through Sunday before a closed mid -level low over the 
Pacific NW heads towards the Northern Rockies and brings more 
widespread rain and snow Sunday through early Monday. The fog 
impacts will be most widespread over central and north-central areas 
during the overnight and early morning hours. 

The closed low will begin migrating towards the Northern Rockies 
late Saturday night into Sunday while being weakened and elongated 
by synoptic shearing. With the colder air aloft not scheduled to 
arrive until Sunday night, snow levels will be over 7000 ft for most 
locations, except along the Continental Divide. This will bring 
mostly liquid precipitation for lower elevations with the exception 
of some isolated instances of light freezing drizzle over the plains 
west of I15. Some freezing precipitation may also occur for the 
colder southwest valleys along the MT/ID/WY borders.

H700 temperatures finally fall to around -5C by Sunday night into 
early Monday and this will bring more efficient accumulating snow, 
heaviest over the Madison/Gallatin ranges above 6000 ft. There will 
be a brief period with snow levels falling to the valley/plains 
floors Monday morning, although it does not appear that this will be 
long enough to support widespread accumulating snow impacts. 
Northwesterly winds may get gusty Monday morning, though gusts look 
to stay below 40 mph. Ensembles continue to favor ridging aloft to 
bring drier conditions and near average temperatures for the 
remaining first half of next week, with unsettled conditions looking 
to return later in the week. - RCG

 - Forecast Confidence & Scenarios:

...Dense fog through Sunday...

Hi-Res Ensemble Forecast (HREF) guidance supports the development of 
fog between 9pm this evening and 3am Sunday over the plains of 
Central and North Central Montana, with this area of fog persisting 
through 9am to 3pm Sunday before an area of precipitation lifting 
northeast from Southwest Montana brings an end to the reduced 
visibilities. The aforementioned HREF guidance largely support 
probabilities of between 40-60% with respect to visibilities 
falling below 1/4 mile during the overnight hours, and for this 
reason a Dense Fog Advisory has been issued yet again through 12 
pm Sunday. Confidence is highest in visibilities falling to 1/4 
mile or less along and west of the I-15 corridor, MT Hwy 200/US 
Hwy 87 corridor, and in Milk River Valley where persistent low 
level east to north flow will support upslope fog. 
- Moldan

...Light mountain snow and lower elevation rain, snow, and some 
mixed precipitation Sunday through Monday morning...

The main trough moves through Sunday through early Monday and brings 
a wave of widespread precipitation to much of the forecast area. 
Aside from some light snow along the Continental Divide and perhaps 
some spotty freezing drizzle over the plains west of I15 and over 
the higher southwest valleys, most of the precipitation will be 
falling in the form of rain until Sunday night. The overall pattern 
and NBM probabilities favor the Madison and Gallatin ranges for the 
best chance (60 to 80%) for snowfall amounts in excess of 3 inches. 
Lighter snows, generally up to a couple inches, look to fall along 
the Continental Divide and the central island ranges. The colder air 
is still not looking to be optimally aligned with the moisture for 
lower elevation snows, but will monitor the Gallatin valley where 
there is around a 30 to 40% chance for a couple inches of snow on 
the south/eastern fringes of the valley Monday morning. - RCG

&&

.AVIATION...
31/18Z TAF Period 

While most areas saw some improvement to lower cloud ceilings 
this afternoon, expect ceilings to lower again this evening with 
light surface winds and elevated low level moisture remaining in 
place across the area. Fog development is most likely across
north-central MT, aided by low level northeast to east flow, but 
can not be ruled out at any terminals. Showers will increase 
overnight as moisture continues to deepen with an area of 
widespread rain moving into SW MT late tonight and spreading north
through central and portions of north-central MT by Sunday 
morning. Hoenisch

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  35  39  36  47 /  20  90 100   0 
CTB  29  41  29  50 /  10  60  50   0 
HLN  35  43  36  49 /  50 100  90  10 
BZN  34  41  34  41 /  20  90 100  30 
WYS  32  39  26  39 /  80 100  90   0 
DLN  37  40  33  43 /  70 100  90   0 
HVR  30  42  33  46 /   0  70  90  10 
LWT  34  45  33  42 /   0  60 100  40 

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
Dense Fog Advisory from 9 PM this evening to noon MDT Sunday for 
Bears Paw Mountains and Southern Blaine-Cascade County below 
5000ft-Eastern Glacier, Western Toole, and Central Pondera-
Eastern Pondera and Eastern Teton-Eastern Toole and Liberty-
Fergus County below 4500ft-Hill County-Judith Basin County and 
Judith Gap-Northern Blaine County-Northern High Plains-Southern 
High Plains-Western and Central Chouteau County.

&&

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