350
FXUS65 KTFX 120956
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
356 AM MDT Mon May 12 2025

.KEY MESSAGES...

- Passing showers or isolated thunderstorms today.

- Accumulating mountain snow, mostly above 7000 tonight for
  Southwest MT.

- Additionally accumulating mountain snow Tuesday night over
  Southwest MT.

- A slow cooling trend for afternoon temperatures this week.

- The potential for a bit more widespread rainfall once again by
  late next weekend over Southwest MT.


&&

.DISCUSSION...

 - Meteorological Overview:
Scattered showers/isolated thunderstorms continue to move from
southwest to northeast through the CWA this morning. The main
impact from any stronger storms will be gusty winds and small
hail. By tonight, a stronger upper level trof will begin to
approach Southwest MT. This will focus more of the heavier
precipitation towards that portion of the state. Enough cold air
will move in with the trof, that snow levels will fall to around
6500 feet or so. Overall snow is expected to accumulate in the
higher elevations of Southwest MT tonight, thus a winter weather
advisory was issued for that area. The precipitation does diminish
a bit during the day on Tuesday, only to redevelop on Tuesday
night, once again over the mountains of Southwest MT. Additional
winter statements might be needed for the some mountain ranges of
Southwest MT once again Tuesday night.

From Wednesday through Saturday, a spring time weather pattern
will reside over the CWA, resulting in passing
showers/thunderstorms. The overall confidence in precipitation
during this period is low, and most showers will be
small/isolated, thus not producing a significant/widespread
amount of precipitation.

Next Sunday/Monday...the GFS model is more aggressive with a
spring storm to affect portions of Southwest MT during this time.
The EC model, also has some precipitation progged, but just not as
much. Overall, there is still quite a bit of uncertainty on how
strong the weather system for next weekend will be at this time.

 - Forecast Confidence & Scenarios:
The main concern for weather will be in the mountains of Southwest
MT tonight, in terms of how low the snow levels get, and how heavy
the hourly snowfall rates will be. Overall, for mountain areas
above 7000 feet, snow accumulations of several inches are
expected. However, in the Pony area, some forecast models have
progged heavier snowfall in that area, possibly in excess of 8
inches. Day shift will continue to monitor for a possible change
to a winter storm warning for the Pony area should the higher
snowfall amounts look to pan out. Brusda

&&

.AVIATION...
12/06Z TAF Period

The initial concern this TAF period is for lingering showers and
isolated thunderstorms across the region in addition to patchy fog
in wind protected areas that saw precipitation Sunday. Heading
toward the morning, gusty west to southwest surface winds will
become increasingly common. A cold front arrives late Monday,
changing winds to be more westerly to northwesterly at the
surface. An area of rain and mountain snow then develops
thereafter, mostly across Southwest and Central Montana Monday
evening. Mountain obscuring low clouds are forecast with this
precipitation Monday evening. -AM

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

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  72  45  59  43 /  20  40  60  50
CTB  63  40  56  36 /  20  20  60  20
HLN  73  44  59  43 /  20  60  80  50
BZN  74  40  57  39 /  10  70  90  70
WYS  67  33  53  31 /  10  50  90  90
DLN  68  38  54  37 /  10  80  90  70
HVR  77  45  62  41 /  20  40  40  30
LWT  74  41  57  40 /  20  60  40  60

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from 8 PM this evening to 9 AM MDT
Tuesday for Elkhorn and Boulder Mountains-Gallatin and Madison
County Mountains and Centennial Mountains-Northwest Beaverhead
County-Ruby Mountains and Southern Beaverhead Mountains.

&&

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