947
FXUS65 KTFX 191901
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
101 PM MDT Sat Sep 19 2026

.KEY MESSAGES...

 - Rain will slowly end from west to east across Southwest and
   Central Montana through the overnight hours tonight.

 - Drier and warmer weather pattern develops for the upcoming
   week.

&&

.DISCUSSION...

A vertically stacked mid-upper level low, centered over southern
will slowly track east into Wyoming through tonight while
gradually weakening. As the system continues eastward tonight, a
few lingering showers remain possible across southwestern Montana
into Sunday morning as moisture wraps around its backside.
Clearing skies from the west overnight into Sunday morning may
favor fog formation in southwestern Montana valleys. Upper-level
ridging will then rebuild across Montana and the Northern Rockies
by Sunday afternoon, returning predominantly sunny, warmer, and
drier conditions to the area.

A dry weather pattern with above-normal temperatures is expected
next week. Broad-scale ridging will attempt to build westward across
the CONUS while troughing persists off the West Coast, maintaining
upper-level heights above average under a southwesterly flow regime.
High temperatures in the upper 70s to around 80 are anticipated,
running roughly 10 degrees above early-autumn normals.

 - Forecast Confidence & Scenarios:

Hi-Res Ensemble Forecast (HREF) guidance supports a 20-30% chance
for reduced visibilities across Southwest and Central Montana
where recent precipitation has fallen, which seems reasonable
considering uncertainty with how fast skies clear tonight.
Confidence is higher in fog development for areas west of the US
Hwy 287 corridor where skies will clear well before sunrise on
Sunday, with decreasing confidence east of this line. Where fog is
able to develop there is the potential for locally dense fog
given antecedent low level moisture and light winds. - Moldan

&&

.AVIATION...
19/18Z TAF Period

Rain will continue to drift east across southwest MT through most
of the TAF period. MVFR conditions are likely across terminals
KWYS, KEKS, and KLWT with low ceilings being the primary risk as
the showers shift eastward. Across Central and Northern MT, VFR
conditions will prevail through the TAF period as cloud bases will
remain above the minimums, though a spot shower cannot be ruled
out especially for terminals KGTF and KHVR. As we move into the
overnight hours, uncertainty is high on lingering cloud cover as
the storm system exits east. Terminals KWYS, KBZN, and KEKS are of
highest uncertainty as earlier departure of cloud cover could
allow decreased visibility from fog particularly between 20/08z
and 20/15z. Overall, cloud decks will improve towards the end of
the TAF period moving from east to west giving way to VFR
conditions.
-JR

&&

.HYDROLOGY...

The Flash Flood Watch and Flood Watch for portions of Southwest
and Central Montana have been cancelled as precipitation rates
have largely fallen below 0.1" per hour. While additional light
rainfall will occur through the evening hours tonight the threat
for flooding has diminished significantly. None-the-less, some
areas that saw heavy rainfall from Friday evening/night through
this morning may still see linger impacts like muddy roadways and
ponding of water in low-lying areas. - Moldan

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  46  74  47  79 /  10   0   0   0
CTB  43  73  43  77 /   0   0   0   0
HLN  45  72  44  76 /  10   0   0   0
BZN  44  66  40  73 /  40  10   0   0
WYS  34  63  29  69 /  60  10  10   0
DLN  42  67  40  74 /  20   0   0   0
HVR  46  74  46  79 /  10   0   0   0
LWT  46  65  44  74 /  80  30   0   0

&&

.TFX WATCHES/WARNINGS/ADVISORIES...

None

&&

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