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000
FXUS65 KTFX 260933
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
333 AM MDT Fri Apr 26 2024

.SYNOPSIS...

Moisture increases across the area through early this weekend with
rain and mountain snow showers becoming more widespread across the
area by Saturday. Significant snow accumulations are expected
across the highest elevations of southwest Montana through
Saturday with some wet snow possible over some mountain passes.
After some drying late Sunday, the next series of weather systems
from the Pacific move across the area early next week.

&&

.DISCUSSION...

An active weather pattern is evolving for the area with broad upper
level troughing in place across the western US and a leading wave
lifting out into the central Plains states this morning while
another moves onshore in the Pacific NW. The bulk of the energy
moving onshore dives southeast into the Great Basin later today and
tonight with a somewhat convoluted flow pattern developing to its
north across MT as embedded moisture and weaker disturbances shift
across the area in a developing easterly mid level flow later today
through Saturday. Precipitation is ongoing early this morning across
portions of SW MT where an embedded disturbance was located with
another area of precipitation associated with an axis of moisture
moving east into western MT. Deeper moisture and focus for
precipitation will expand north from SW MT today with the western area
of moisture gradually shifting to near the continental divide later
today and tonight before moving east across the area Saturday night.
The absence of larger scale forcing will favor more persistent
precipitation over the mountains of central and southwest MT with
probabilities for one half inch precipitation amounts through Saturday
ranging from around 50% across the central MT mountains to as much
as 80% across the mountains of Gallatin and Madison counties.

Snow levels fluctuate around 7000ft through Saturday night with
impactful snow accumulation mainly above this, but snow may fall
as low as around 6500ft in times of more intense precipitation.
This primarily affects Big Hole and Targhee Passes with potential
for snow accumulation on road surfaces but some periods of reduced
visibility and slushy surfaces are also possible at other passes
along the continental divide at 6500ft and above. Winter storm
warnings and winter weather advisories are in effect through
Saturday evening to highlight changing road conditions at pass
levels and heavy snow primarily above pass levels.

Flow aloft turns back to westerly Sunday with moisture exiting to
the east followed by a relatively dry period before the next series
of systems from the Pacific arrive early next week. Cluster analysis
reveals some notable differences still among the models, likely
related to timing and specific track of shortwaves embedded within
the broader trough and fast westerly flow that develops early next
week. The first in this series of Pacific shortwaves arrives Monday
with deterministic models now depicting a fairly vigorous Pacific
cold front moving east across the area, though timing and
moisture varies among the models. Probabilistic guidance currently
gives a greater than 50% chance for wind gusts in excess of 55
mph along the Rocky Mtn Front and adjacent areas Monday with
potential for more widespread strong wind gusts with a cold front.
Model differences amplify with additional waves and associated
moisture moving through the area Tuesday and Wednesday with about
one third of model ensembles depicting a somewhat further south
track to energy which would result in higher precipitation amounts
and cooler temperatures across northern portions of the forecast
area. Hoenisch

&&

.AVIATION...5
1200 AM MDT Fri Apr 26 2024 (26/06Z TAF Period)

VFR conditions will persist across much of North-central and
portions of Central Montana through the remainder of the evening and
into the early morning hours. Light precipitation will begin
affecting most terminals in central Montana after 26/16Z with
periods of MVFR visibilities and MVFR/IFR ceilings possible heading
into the afternoon.

Mountain snow across southwestern Montana has already started and
will continue through the remainder of the TAF period. Periods of
heavy mountain snow with mountain obscuration will be possible in
the vicinity of KBZN and KEKS. At the terminals, light rain will
persist through the period with reduced visibility and lowered cloud
ceilings in MVFR/IFR conditions possible after 26/12Z.

-thor

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

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  59  41  56  39 /  20  70  60  50
CTB  53  38  53  35 /  20  40  50  20
HLN  57  42  53  39 /  50  80  80  50
BZN  54  36  56  37 /  90  60  70  60
WYS  50  33  52  32 /  80  70  80  70
DLN  53  38  50  36 /  80  80  80  30
HVR  66  39  65  42 /  20  20  10  30
LWT  57  38  58  38 /  50  40  30  30

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 6 PM MDT Saturday for Elkhorn and
Boulder Mountains-Ruby Mountains and Southern Beaverhead
Mountains.

Winter Storm Warning until 6 PM MDT Saturday for Gallatin and
Madison County Mountains and Centennial Mountains-Northwest
Beaverhead County.

&&

$$

http://www.weather.gov/greatfalls