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000
FXUS65 KTFX 252325
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
525 PM MDT Thu Apr 25 2024

...Aviation Section Updated...

.SYNOPSIS...

Unsettled conditions are expected across the Northern Rockies
through the end of work week and portions of the weekend as a slow
moving disturbance slides over the Western United States. This
distance will bring widespread precipitation to Southwest and
portions of Central Montana, with precipitation amounts of half
of an inch to one inch being possible over this timeframe. Further
north across North Central Montana precipitation amounts will
decrease significantly the further north and east you move from
the Central Montana mountains and Continental Divide, with
generally less than a tenth of an inch expected across these
areas.

&&

.DISCUSSION...

Rest of today through tonight...Showers and thunderstorms were
developing quickly this afternoon across Northeast Idaho where
clearing occurred earlier in the day, with these showers and
thunderstorms expected to lift northeast across portions of
Southwest Montana through the remainder of the afternoon and evening
hours. Best chance for thunderstorm activity across Southwest
Montana exists along and south of the I-90 corridor, most notably
along and southeast of a Monida Pass, to Norris Hill, to Bozeman
Pass line. Primary threat from any thunderstorm will be lightning
and brief periods of heavy rainfall across lower elevations and
snowfall in the mountains. These heavier bursts in precipitation
will bring significant reductions in visibility over a short period
of time and distance. Precipitation chances will also be on the
increase along the Continental Divide through the evening and
overnight hours, in addition to south of the Montana Hwy 200
corridor as an embedded disturbance lifts northeast over the
Northern Rockies. - Moldan

On Friday an upper-level trough will begin to move over North-
central, Central, and Southwestern Montana. This will bring cooler
temperatures and precipitation to the area as a surface cold front
dives south from Canada and across the CWA. Isolated thunderstorms
will be possible in Southwestern Montana on Friday. The lower-
elevations of Southwestern Montana have a 15 - 35% chance of
receiving a half inch of rain or greater. The lower-elevations of
Central Montana have a 15 - 40% chance for a quarter inch of rain or
greater. This upper-level trough will remain in place over North-
central, Central, and Southwestern Montana on Saturday. This storm
will bring heavy snow to the mountains of Southwestern Montana. The
higher elevations of the mountains have a 80% chance for receiving 8
inches or more snow from Friday to Saturday. The mountain peaks have
a 70% chance for receiving a 12 inches or more snow from Friday to
Saturday. As a result, a Winter Storm Warning is in effect for the
Gallatin and Madison ranges and Northwest Beaverhead County from 6
AM Friday until 6 PM Saturday. A Winter Weather Advisory is in
effect for the Ruby Mountains and Southern Beaverhead Mountains and
Elkhorn and Boulder Mountains from 6 AM Friday until 6 PM Saturday.
On Saturday the lower-elevations of Central and Southwestern Montana
have a 30 - 50% chance for receiving a quarter inch of rain or
greater. Some of the lower-elevations of Southwestern Montana could
see a few flakes of snow mix in with the rain. On Saturday North-
central Montana has a 10 - 30% chance for receiving a quarter inch
of rain or greater. The mountains of North-central and Central
Montana will see a rain/snow mix on Friday and all snow for the most
part on Saturday. On Saturday the mountains of North-central and
Central Montana have a 35 - 50% chance for receiving an inch or more
snow. - IG/Moldan

Sunday through Monday...On Sunday above North-central, Central, and
Southwestern Montana there will be zonal flow with a shortwave
trough embedded in it. This will allow temperatures to warm back up
to slightly above seasonal averages. The shortwave trough will cause
isolated light rain to occur across North-central, Central, and
Southwestern Montana. There is a 10 - 20% chance for a tenth of an
inch of rain or greater across the lower-elevations of Central and
Southwestern Montana along and south of the Montana Highway 200
Corridor. On Sunday there will be a strong surface pressure gradient
and so there will be gusty winds along the Rocky Mountain Front.
There is 50 - 70% chance for wind gusts exceeding 55 mph on Sunday
along the Northern Rocky Mountain Front. On Monday there is an upper-
level trough and associated weak cold front that moves through the
area. This will slightly cool off temperatures and bring rain and
snow to Southwestern Montana. Due to the cold front there is a 70 -
90% chance for wind gusts exceeding 55 mph along the Rocky Mountain
Front on Monday. On Monday across the lower-elevations of
Southwestern Montana there is a 10 - 35% chance for a tenth of an
inch of rain or more. On Monday across the Mountains of Southwestern
Montana there is a 75% chance for a tenth of an inch of snow or
greater.

Tuesday through next Thursday... On Tuesday clusters indicate that
an upper-level ridge begins to move over North-central, Central, and
Southwestern Montana. This will warm up temperatures slightly with
dry conditions across the area. On Wednesday three clusters (87% of
ensemble members) indicate that there will be an upper-level ridge
in place over North-central, Central, and Southwestern Montana. The
other cluster (13% of ensemble members) has zonal flow over the
area. On Thursday clusters indicate that there will be an upper-
level ridge in place over North-central, Central, and Southwestern
Montana. This indicates that most likely temperatures will warm back
up across the area for Wednesday and Thursday. -IG

&&

.AVIATION...
525 PM MDT Thu Apr 25 2024 (26/00Z 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. Cloudiness will increase; however, and
some light precipitation may develop shortly thereafter. Showers and
a thunderstorm or two will continue to propagate into Southwest
Montana, specifically near KEKS and KBZN, resulting in periods of
reduced visibility and lowered cloud ceilings into MVFR conditions,
and will slowly progress into the Central Plains toward the latter
half of the TAF period. Development of any thunderstorms may result
in occasional lightning and periods of heavy precipitation, but will
likely be retained to Southwest Montana through the period. - Pierce

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

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  47  57  45  56 /  10  50  60  60
CTB  36  51  37  54 /  10  20  60  50
HLN  46  57  42  52 /  20  80  90  70
BZN  41  51  38  56 /  70  90  80  70
WYS  36  48  36  48 /  90  90  80  80
DLN  41  49  36  47 /  60  90  80  80
HVR  40  64  40  66 /  10  10  20  20
LWT  44  54  40  58 /  30  60  50  30

&&

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

Winter Storm Warning from 6 AM Friday to 6 PM MDT Saturday for
Gallatin and Madison County Mountains and Centennial Mountains-
Northwest Beaverhead County.

&&

$$

http://www.weather.gov/greatfalls