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000
FXUS65 KTFX 260609
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
1105 PM MST Sat Jan 25 2020

...UPDATED AVIATION SECTION...

.SYNOPSIS...

A moist westerly flow aloft will continue to reside over the
region for the next few days. Light rain or snow showers along the
divide this evening will give way to a more widespread light
snowfall on Sunday afternoon and evening over Southwest MT. Above
normal temperatures will continue over North Central MT, along
with some periods of winds. However, there is the potential for a
widespread strong wind event by late next week over much of North
Central MT.

&&

.Evening Update...

Update has been published, with only minor updates made to
temperatures and PoPs to account for latest radar trends and
surface observations, in addition to adding patchy to areas of fog
at some locations. Upper level ridge continues to slide east
towards the Northern Rockies this evening. At the surface, low
pressure over Southeastern Saskatchewan will continue to drop
southeast into Eastern North Dakota through Sunday morning. The
departure of this surface low from the Northern Rockies/High
Plains and strengthening high pressure over the Great Basin and
beneath the eastward ridge will allow the pressure gradient to
relax across Southwest and North Central Montana this evening and
during the overnight hours tonight. This will allow the boundary
layer to become decoupled across region, with surface winds
relaxing and becoming light. The one exception to these light
winds will be the narrow north-to-south orientated valleys across
Southwest Montana (i.e. Madison and Red Rock), where terrain
funneling and low level southerly flow will enhance surface winds
to maintain speeds of generally 10-20 mph tonight. Mid-level warm
front and upper level jet draped across Central Montana this
evening continues to produce light precipitation, especially over
the mountains where orographic lift is enhancing precipitation.
This area of precipitation is expected to gradually decrease in
coverage after midnight as the ridge moves overhead and the
forcing decreases/slides east. With clear and/or clearing skies
developing and boundary layer decoupling occurring/expected to
occur, patchy to areas of fog is expected to develop in some
valley and plains locations tonight and Sunday morning. - Moldan

&&

.AVIATION...

Updated 1105 PM MST Sat Jan 25 2020 (26/06Z TAF Period)

North Central and Central Montana (KCTB, KHVR, KLWT, KGTF, KHLN):
VFR conditions are expected to prevail through at least the next 24
hours. Skies will remain mostly clear through around 15Z with
decreasing mid clouds (between 6000 and 8000 feet agl) from KGTF
southwest to KHLN. A weak cold front will also bring areas of
fog/low clouds to the northeast plains (possibly including KHVR),
mainly between 08Z and 14Z. A disturbance will then bring mid and
high clouds to the area after 15Z. Scattered rain and snow showers
with an associated cold front will obscure mountains, as well as
bring periods of MVFR conditions to KHLN between 22Z and 02Z and to
KHVR and KLWT after 03Z. Light downsloping winds will hinder
precipitation development along the east slopes of the Rockies
(KCTB, KGTF).

Southwest Montana (KBZN, KEKS, KWYS): Mid clouds will decrease here
as well through 15Z, but MVFR/IFR conditions will likely persist at
KWYS due to low cloud advection from southeast Idaho. The
aforementioned disturbance will then bring widespread mountain
obscuration in low VFR/MVFR conditions with rain/snow showers after
16Z, then widespread MVFR/IFR conditions in snow after 00Z.
Coulston

&&

.PREV DISCUSSION...
/ISSUED 415 PM MST Sat Jan 25 2020/

Tonight through Monday...Weak upper level disturbances continue to
move from west to east through the region. Light showers west of
the divide at 2 PM are trying to move east of the divide, but
downslope winds are limiting the precipitation to mostly the
higher elevations. However, a few light showers will be possible
this evening, at lower elevations, mostly along the divide. On
Sunday, a stronger upper level disturbance will move across
Southwest MT. Expect some rain and snow to develop over the
Southwest by midday, with snow becoming likely at all elevations,
mostly south of I-90 on Sunday night. With 1 to 3 inches possible
at lower elevations and 4 to 8 inches possible in the mountains, a
winter weather advisory was issued for areas mostly along/south
of I-90 in Southwest MT. The heaviest snowfall is expected in the
West Yellowstone area for this event. On Monday, drier conditions
move into much of the region, along with increased winds. Overall
the strongest winds will be in the East Glacier Park and Cut Bank
areas, but at this time, wind speeds should remain below high
wind criteria.

Tuesday through Saturday...Quick moving weather disturbances will
continue to affect much of the region next week. Overall,
high amounts of precipitation are not expected, as the flow aloft
is more westerly and the system will be quick moving. Afternoon
temperatures are likely to remain above normal, with the potential
of well above normal temperatures possible by next
Friday/Saturday. Additionally, there is the potential for a strong
wind event starting late Friday and going into Saturday over North
Central MT. Brusda

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  26  45  31  47 /  10   0  10   0
CTB  21  41  30  42 /   0  10   0   0
HLN  24  42  28  45 /  60  20  10   0
BZN  22  43  26  44 /  10  50  60  10
WYS  21  33  15  31 /  90 100  90  30
DLN  21  38  24  37 /  10  40  60  10
HVR  20  37  26  43 /   0   0  10   0
LWT  24  45  28  45 /   0   0  20  10

&&

.TFX WATCHES/WARNINGS/ADVISORIES...

Winter Weather Advisory from noon Sunday to 5 AM MST Monday
Beaverhead...Gallatin...Madison.

&&

$$

http://www.weather.gov/greatfalls