Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 280945
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
345 AM MDT Thu Mar 28 2024

.SYNOPSIS...

A Pacific cold front will cross the region today spreading rain
and snow showers across the area. Little or no snow accumulation
is expected at lower elevations but some mountain passes will see
minor snow accumulation with several inches of snow likely across
the mountains near Yellowstone National Park. A cooler airmass
settles across the area through the weekend with some additional
snow showers possible at times. A warmer and dry weather pattern
returns for early next week.

&&

.DISCUSSION...

Early morning satellite imagery shows a stacked (co-located
surface to upper level) low off the Pacific NW coast with upper
level jet moving into CA and surface front pushing east into the
Northern Rockies. Layer advected precipitable water imagery shows
a fairly cohesive plume of moisture at 850-700MB and broader
700-500MB plume being maintained with the front as it moves from
WA/OR east into ID with upstream radar imagery in southern ID
showing widespread precipitation. This sets up favorable moist
southwest flow for orographically generated precipitation near the
ID/WY border already this morning ahead of the front`s arrival.

Timing of the front is slightly earlier than previous forecasts,
crossing the divide this morning, however most short term models
also develop a weak wave that slows the front’s progression across
central and southwest MT through this afternoon and results in
somewhat greater amounts and coverage of precipitation today.
Showers should begin to push east into central and southwest MT by
mid morning with a fairly wide coverage of showers accompanying
the front and additional showers moving across the area this
afternoon and evening under cooler and somewhat unstable westerly
flow behind the front. Snow levels initially around 6000 ft will
drop to 3000-4000 ft with the frontal passage resulting in periods
of mixed precipitation or snow at lower elevation locations
across central and SW MT today, however temperatures overall
at lower elevations (outside of precipitation) will be in the mid 40s
this afternoon resulting in little no impact to road surfaces,
but travelers should be ready for quickly changing visibility in
showers. One area that will see snow accumulation are the
mountains near the MT/ID border where a winter weather advisory
has been issued with greatest impacts likely near Raynolds and
Targhee passes where probabilities for accumulations of 6 inches
or more through early this evening are around 70%.

A cooler and unsettled weather pattern persists through the
upcoming weekend as the offshore upper low tracks well south of
the region into the SW US while some weaker disturbances from the
NW move through the Northern Rockies and MT. A somewhat colder
Canadian airmass also slides south across the north-central MT
plains later tonight through Friday keeping temperatures there
around 10-15 degrees below seasonal averages through the weekend
while temperatures across southwest MT remain closer to 5-10
degrees below seasonal averages. Moisture associated with the
disturbances from the NW and on the northern periphery of the SW
US low will produce some snow showers at times but no organized or
impactful precipitation is anticipated.

A warmup is still on tap for early next week with good multi-
model ensemble support for ridging with daytime temperatures
likely to reach into the 60s for many areas by Tuesday. Beyond
that there are some differences in how quickly the ridge is broken
down by stronger troughing digging southward from the Gulf of AK
with cluster analysis showing around 40% of longer range model
ensemble members breaking down the ridge by Wed and 60% delaying
the break down until Thursday or Friday.

&&

.AVIATION...
1141 PM MDT Wed Mar 27 2024 (28/06Z TAF Period)

Increasingly moist SW flow aloft brings more widespread mountain
obscuration overnight with snow increasing near the continental
divide. Rain/snow showers begin moving east across central/southwest
MT Thursday morning as an eastward moving cold front shifts across
the area. Most terminals will see a period of MVFR conditions with
some brief IFR possible in heavier showers which may also transition
to snow. Surface winds shift to the west with the frontal passage
and a few showers may linger into this evening. Hoenisch

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

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  46  25  42  25 /  70  20  20  40
CTB  45  22  38  20 /  20   0  10  30
HLN  48  27  48  27 /  90  20  20  20
BZN  48  24  47  23 /  80  50  10  20
WYS  39  16  39  12 / 100  60  30  20
DLN  47  25  45  25 /  80  20  10  10
HVR  44  22  36  20 /  40  20   0  20
LWT  48  23  41  22 /  90  40  30  50

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 9 PM MDT this evening for Gallatin
and Madison County Mountains and Centennial Mountains.

&&

$$

http://www.weather.gov/greatfalls


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