379
FXUS65 KTFX 260234
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
834 PM MDT Fri Apr 25 2025

.KEY MESSAGES...

 - Turning active this weekend with a few showers and
   thunderstorms on Saturday before widespread rain Sunday

 - Snow levels fall quickly Sunday night, bringing snow to at
   least pass level, with some low elevation snow possible as well

 - Temperatures rebound quickly next week after a cool Monday,
   with well above average temperatures expected by late next week

&&

.UPDATE...

Showers will linger in Southwestern Montana through tomorrow
morning primarily along the Montana/Idaho Border. Otherwise it
will be a pleasant night across North-central, Central, and
Southwestern Montana. For the update wind speeds and gusts were
adjusted to better reflect current observations and trends. Pops
across Southwestern Montana, primarily along the Montana/Idaho
Border, were increased through tomorrow morning to reflect
current radar imagery and the latest hi-res model guidance. The
rest of the forecast is on track. -IG

&&

.DISCUSSION...
/Issued 519 PM MDT Fri Apr 25 2025/

 - Meteorological Overview:
Sunny skies are found across most of North Central and
Southwestern Montana this afternoon as high pressure to the east
remains in control of the weather across the area. Although skies
are clear now, our next weather system approaching from the
Pacific will begin to influence the weather overnight tonight as
clouds push in from the south overnight tonight. While this system
will only bring a few showers (and maybe a thunderstorm) to the
area during the day on Saturday, mainly across the Central Montana
Mountains, precipitation will pick up noticeably on Sunday as
cold air begins to pour in from the north, which will result in an
area of moderate to possibly heavy precipitation, mainly along
and south of a line from Helena to White Sulphur Springs.
Initially, much of this precipitation will start as rain, possibly
at all elevations, but snow levels will quickly fall Sunday
afternoon and evening, and should result in snow levels dropping
to at least pass level, resulting in a heavy, wet snow that could
cause disruptions to travel and may even result in some tree
damage, especially as trees begin to come out of dormancy as
temperatures have been warming up.

After a cooler day on Monday, temperatures will recover quickly
through the remainder of the week, with temperatures climbing into
the 70s by the end of the week. The rest of the week will be on
the drier side as well, save for a few showers around midweek.

 - Forecast Confidence & Scenarios:

The biggest area of uncertainty remains tied to snow levels with
the weekend system. Recent NBM data has generally kept mean snow
levels above pass level, with this extending even to the 10th
percentile (or lowest expected by the model). With this being
said, it seems that the NBM is slightly under representing the
range of outcomes with this system, which has been demonstrated by
some recent runs of the NAM and the GFS, which have tended to
bring snow levels much lower than the NBM, with some runs even
suggesting that the valleys and plains could see some accumulating
snowfall Sunday evening through Monday morning. This possibility
also fits the conceptual model (in other words, what a
meteorologist would expect to happen) of this situation, with
heavier precipitation rates resulting in lowering snow levels,
especially since the lower part of the atmosphere will likely be
within a few degrees of freezing. Should the snow levels fall like
the GFS and NAM suggest, we could be looking at a much more
impactful system, with both higher snowfall totals and more
widespread snowfall to the valley floors and plains. However,
there remains the possibility that we wind up slightly warmer than
expected (generally less likely but always a possibility), which
could result in some more rainfall in the higher terrain. While
this would lessen the impact of snowfall on roads, it would raise
the risk for some stream rises due to the combination of snowmelt
and rainfall, though it seems that the remaining snowpack is still
able to absorb some rainfall before becoming an issue at this
time. Ludwig

&&

.AVIATION...
26/00Z TAF Period

Gusty east to southeast surface winds continue through early this
evening on the plains before diminishing later this evening and
overnight. Otherwise, VFR conditions prevail with higher level
clouds increasing from south to north through Saturday morning.
Isolated showers/thunderstorms developing in southeast Idaho may
reach the KWYS terminal before dissipating late this evening.
Similar activity is likely to develop across central and
southwest MT Saturday afternoon as additional moisture and a weak
weather disturbance track northward into the area. Hoenisch

Refer to weather.gov/zlc for more detailed regional aviation
weather and hazard information.

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  35  68  42  63 /   0  30  20  60
CTB  31  66  39  57 /   0  10  10  30
HLN  38  70  43  63 /   0  50  20  70
BZN  33  68  37  65 /   0  30  10  80
WYS  28  60  25  59 /  50  10   0  80
DLN  36  66  37  63 /  20  30  10  80
HVR  33  71  40  69 /   0   0  10  40
LWT  33  67  41  63 /   0  30  20  80

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
Winter Storm Watch from Sunday evening through Monday morning
for Gallatin and Madison County Mountains and Centennial
Mountains.

&&

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