Shelby Montana Weather Forecast Discussion

370
FXUS65 KTFX 070413
AFDTFX
Area Forecast Discussion
National Weather Service Great Falls MT
1013 PM MDT Mon Oct 6 2025
.KEY MESSAGES...
- After another cold night tonight, general dry condtions and
   above average temperatures are expected for the remainder of
   the workweek.
- A low pressure system and cold front will then bring windy
   conditions, increased shower activity, and mostly mountain snow
   this weekend.
&&
.UPDATE...
Evening update has been published, with the main adjustment being
to cool the valleys of Southwest Montana, especially those cold
prone valleys like Hebgen/West Yellowstone and Big Hole, some 3 to
5 degrees. Transient upper level ridging will continue to build
in over the Northern Rockies through the overnight hours, with a
weak disturbance within northwest flow diving southeast over
mainly Hill, Blaine, Chouteau, and Fergus Counties. This
disturbance will bring mainly mid-level cloudiness for a portion
of the overnight hours here, with skies clearing near sunrise on
Tuesday. Further south across the aforementioned valleys of
Southwest Montana clear skies are expected throughout the duration
of the overnight hours, which combined with light winds will lead
to ideal radiational cooling. This ideal cooling combined with
cool drainage from the recently snow covered mountains will set
the stage for the more cold prone valleys to overachieve on
cooling tonight, and thus the lowering of temperatures. Otherwise
the remainder of the forecast remains on track, with patchy fog
once again being possible overnight tonight. - Moldan
&&
.DISCUSSION...
- Meteorological Overview:
Upper-level ridging will build across the Northern Rockies and
Montana today and tomorrow, resulting in general dry and mild
conditions for much of the workweek following another cold night
tonight. An upper-level trough will split over western Canada on
Wednesday. A portion of its energy will track east and well north of
the area, bringing a slightly cooler airmass south across the plains
on Thursday. A larger portion of the upper troughs energy will dive
southwestward and offshore, leading to an amplification of the upper
ridge downstream across the western US through Friday. Dry
conditions will prevail across the area through at least Friday,
with temperatures likely to peak around 10-15 degrees above seasonal
averages on Friday. Medium-range model ensembles generally agree
that the offshore trough will progress inland this weekend, leading
to a transition to cooler and unsettled conditions by Sunday, which
may then persist into early next week.
- Forecast Confidence & Scenarios:
Looking ahead to the weekend, there is reasonable confidence in a
transition to cooler, unsettled conditions. However, details typical
of this timeframe, such as the exact timing of the trough`s push
inland, remain less certain. This will influence how long warmth
lingers into Saturday, with some spread still among ensemble
members. Uncertainty increases later in the weekend due to the
interaction of additional shortwave energy dropping into the upper
trough as it moves into the Northern Rockies. This interaction is
key to determining the placement of moisture and the overall
strength of the system. Regardless of the system`s strength, windy
conditions appear likely at some point during the weekend
transition. Precipitation timing and amounts are highly uncertain,
though currently, the NBM indicates a 50-80% probability for at
least 0.10 amounts and a 30-50% probability for amounts exceeding
0.25 late Saturday through Monday for much of the area. Hoenisch
&&
.AVIATION... 07/00Z TAF Period
The TAF period remains benign with the upper level ridge in place.
Confidence for fog overnight at any TAF site remains too low to
mention. -Wilson
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF  33  69  42  72 /   0   0   0   0
CTB  33  68  36  68 /   0   0   0   0
HLN  29  67  37  70 /   0   0   0   0
BZN  24  65  32  70 /   0   0   0   0
WYS  12  58  22  59 /   0   0   0   0
DLN  26  64  31  66 /   0   0   0   0
HVR  30  70  37  73 /   0   0   0   0
LWT  28  67  41  73 /   0   0   0   0
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
http://www.weather.gov/greatfalls

NWS TFX Office Area Forecast Discussion