777
FXUS65 KTFX 272002
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
202 PM MDT Thu Mar 27 2025

.KEY MESSAGES...

 - Scattered showers and a few thunderstorms develop this afternoon
   across Southwest and Central Montana.

 - Friday will begin a cooler and active period, with widespread mountain
   snow and lower elevation rain and snow for the weekend.

 - Daily chances for precipitation persists next week.

&&

.DISCUSSION...

 - Meteorological Overview:

A deep closed upper level low centered offshore of the WA/OR coast
will gradually open, sending Pacific moisture and a series of
shortwave disturbances across the Northern Rockies and MT through
the upcoming weekend. At the surface, low pressure developing across
central MT this afternoon will move off to the east tonight as a
Pacific cold front moves across the area this evening. Showers amd a
few thunderstorms develop this afternoon along the Pacific cold
front across southwest MT and further upstream across ID in
association with the initial shortwave disturbance and deeper cold
air aloft. Somewhat deeper instability will be available for
convection across eastern portions of SW MT late this afternoon,
though cloud-cover may inhibit more organized thunderstorm activity.
Still, initially dry and well mixed lower-mid levels could support
some stronger wind gusts with some cells across eastern portions of
SW and central MT early this evening. Showers and isolate
thunderstorms associated with the upper disturbance and colder air
aloft will track east across central and north-central MT late this
evening and overnight.

A colder airmass and high pressure spreads south from AB and SK
across most of the north-central MT plains behind the departing low
tonight with the cooler airmass extending further south and west
across central and southwest MT for the weekend. This results in
daytime temperatures only in the  30s to low 40s across much of the
area this weekend. Several rounds of precipitation are expected with
the passage of disturbances moving out of the offshore upper low
Friday through Sunday with more persistent precipitation focused
across southwest MT as the bulk of the energy and moisture track
east through ID and WY. By Saturday morning, snow levels are
expected to be as low as around 3000 ft across much of the area and
remain in the 3000-4000 ft range for most of the weekend.

Temperatures moderate some next week but look to remain at least
somewhat below seasonal averages. Longer range model ensembles
continues to broadly support another trough deepening offshore early
next week at least part of its energy progressing inland through
much of next week.

 - Forecast Confidence & Scenarios:

Thunderstorm Risk This afternoon/Evening: HREF calibrated
probability of lightning is as high as 50% from southern Madison
county northeast through Gallatin, Meagher and Fergus Counties
with a 20% or lower risk elsewhere. The risk for thunderstorm
gusts exceeding 50 mph is greatest (40-50%) along an axis from
eastern Meagher through Fergus counties.

Weekend Snow: Recent warmth and marginal daytime temperatures
make snow amount forecasts tricky, especially at lower elevations.
The central MT mountains ranges and Gallatin/Madison ranges in
southwest MT are most likely (50-70%) to see 2-day snow totals in
excess of 6 inches with a 30-40% chance for 2-day snow
accumulations to around 2" at lower elevations across north-
central MT. However, lower elevation snow will be more
intermittent/showery and prone to melting outside of areas of more
intense precipitation and overnight periods.

&&

.AVIATION...
27/18Z TAF Period

The initial concern this TAF period will be for showers and a few
thunderstorms this afternoon and evening, primarily across Southwest
Montana northeastward through eastern portions of Central Montana. A
secondary concern for showers and perhaps a few thunderstorms will
exist across most areas tonight, but is lower probability at this
time. Overall, the chance for precipitation was not high enough at
any time or location to warrant more than a prob30 mention.

Gusty southwesterly to westerly winds will develop by early
afternoon in most areas, with a cold front shifting winds more
northwesterly or northerly late tonight into tomorrow over the
plains. Aside from the wind shift, the main concern with this
front will be for a period of low clouds late tonight into
tomorrow over the plains. -AM

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

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  35  52  31  37 /  30  30  80  60
CTB  28  43  26  36 /  50  20  40  30
HLN  39  57  33  44 /  10  50  80  60
BZN  34  55  31  44 /  30  40  70  70
WYS  27  47  24  43 /  60  30  30  60
DLN  32  54  30  47 /  20  50  50  60
HVR  32  46  25  38 /  50  30  40  40
LWT  36  49  27  35 /  40  30  90  70

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
Winter Storm Watch from Friday evening through late Saturday
night for Little Belt and Highwood Mountains.

&&

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