126
FXUS65 KTFX 200250
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
850 PM MDT Sat Apr 19 2025

.KEY MESSAGES...

- A cold frontal passage this afternoon begins the active pattern
  this week, with daily chances for lower elevation rain mountain
  snow.

- Temperatures cool closer to normal for the week after today.

&&

.UPDATE...

Main adjustment to the overnight portion of the forecast period
was to back off a bit on additional rain shower potential over the
plains of North Central and Central Montana. While showers have
been moving over the area, those showers that reach the ground are
producing little rainfall. However, have left the chance for
showers fairly high over the Southwest Montana mountain areas, as
a weak trailing frontal boundary may provide enough of a forcing
mechanism that will keep showers going for most of the night.
-Coulston

&&

.DISCUSSION...
/Issued 556 PM MDT Sat Apr 19 2025/

 - Meteorological Overview:

Increasing moisture ahead of the front has begun precipitation
just to the east of the Continental Divide. The cold front
pushing east across the state later today will continue to bring
showers/mountain snow through the overnight hours Sunday. Cooler
temperatures settle in behind the front, with temperatures
cooling back towards normal for the week. A broad, upper level
trough sets up along the Northwest U.S for most of the week. This
will bring daily chances for lower elevation rain and mountian
snow. The best chances for widespread, precipitation will be
Sunday night through early Tuesday morning where there is better
forcing from the trough aloft. Weak instability in place Sunday
and Monday will allow for a few isolated thunderstorms in the
afternoon/evening. However, vertical profile soundings don`t
support for robust thunderstorms outside of the typical sub-
severe gusty winds. Snow levels will generally stay between
6,000-7,000ft Sunday, but will fall Monday and Tuesday morning,
which can allow light snow to mix in across lower elevations.

 - Forecast Confidence & Scenarios:

Forcing along the front today doesn`t look robust, so moisture
amounts will generally stay below 0.1" except for some areas in
Southwest MT, where they have better chances for 0.1"-0.25" of
moisture. For Sunday night through early Tuesday morning, there`s
a 40-80% chance for 0.1" of moisture across lower elevations and
a 30-50% for 0.25" of moisture east of the Havre to Monida line.
Through the week, precipitation remains on the lighter side unless
you get a good shower or thunderstorm.

Most of the snow will be above pass level in the Glacier Park
region and the Gallatin and Madison County Mountains. They have a
60-90% chance for 6" or more. Down to Pass level, there`s a 50%
chance for 4" at King`s Hill Pass and a 40-60% chance for 2" of
snow along Marias, Chief Joseph, and Raynolds Pass. The most
impactful time period for snow on passes will be overnight
Sunday/Monday morning with lower snow levels and temperatures
below freezing. Warming temperatures during the morning will
likely turn snow covered roads to slush, and melt off Monday
afternoon. -Wilson

&&

.AVIATION...
20/00Z TAF Period

Low VFR to MVFR ceilings and visibility are expected this evening
as a cold front brings low clouds and areas of rain to North
Central and Southwestern Montana this evening. As we head later
into the overnight, MVFR conditions will prevail even as rain
showers end, but further degradation of conditions is expected
Sunday morning as another round of rain showers push into the
area. Ludwig

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

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  37  59  36  54 /  30  30  40  70
CTB  33  54  31  50 /  20  30  20  60
HLN  37  59  36  50 /  40  40  60  80
BZN  33  56  31  46 /  80  50  90  90
WYS  27  49  25  45 /  60  60  70  90
DLN  31  57  32  48 /  60  30  60  60
HVR  35  60  34  56 /  30  50  60  70
LWT  36  55  34  50 /  40  60  80  80

&&

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

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