414
FXUS65 KTFX 061551
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
951 AM MDT Mon Oct 6 2025

.KEY MESSAGES...

 - Dry conditions prevail through Friday with temperatures
   warming back to above seasonal averages beginning Tuesday.

 - A transition to cooler and unsettled conditions begins this
   weekend.

&&

.UPDATE...

The primary concern this morning is patchy dense fog, mostly in
the Helena area where visibility reductions below a half mile have
been observed. The latest hires guidance suggests this fog should
slowly thin out through around noon or so, but ridging moving in
aloft and a peak sun angle less than 40 degrees may maintain it a
little longer. Inversions over wind protected central/southwest
valleys, including Helena, may also result in slightly cooler
afternoon highs compared to what`s in the forecast. The primary
update was to adjust the fog grids to current trends. - RCG

&&

.DISCUSSION...
/Issued 312 AM MDT Mon Oct 6 2025/

 - Meteorological Overview:

Upper-level ridging will build across the Northern Rockies and
Montana today and tomorrow, causing temperatures to quickly
rebound to above-seasonal averages by Tuesday. 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...
06/12Z TAF Period

Early morning satellite imagery shows some some patchy low clouds
still clinging to some of the central and southwest MT mountain
rages as well as some fog visible in Missouri river valley/breaks
near and below Ft Benton. The risk for patchy fog development
still this morning is greatest at SW MT TAF sites, including
KBZN, KHLN and KWYS. Otherwise, VFR conditions prevail under
clear skies and relatively light surface winds through the period.
Hoenisch

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  58  35  69  40 /   0   0   0   0
CTB  58  32  67  35 /   0   0   0   0
HLN  58  32  67  36 /   0   0   0   0
BZN  54  27  65  30 /   0   0   0   0
WYS  51  17  57  22 /   0   0   0   0
DLN  55  29  64  30 /   0   0   0   0
HVR  61  33  70  37 /   0   0   0   0
LWT  56  32  67  40 /   0   0   0   0

&&

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

$$
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