Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 260546
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
1145 PM MDT Mon Mar 25 2024

Updated Aviation Discussion

.SYNOPSIS...

Any lingering snow showers diminish this evening, but another
passing disturbance will bring another round of light snow later
tonight into Tuesday, especially for areas over or near higher
terrain. Breezy and milder conditions move in mid-week before
another series of weather systems bring cooler temperatures and
areas precipitation for the second half of the week.

&&

.UPDATE...

The current forecast is doing well for this evening and tomorrow
morning, just needed to lower temperatures 5 degrees across
Northern Blaine county for lows tonight into the morning hours.
Wet pavement surfaces will continue to re-freeze tonight where
snow melting had occurred this afternoon. Webb

&&

.AVIATION...
1145 PM MDT Mon Mar 25 2024 (26/06Z TAF Period)

A moist NW flow aloft with embedded disturbances will maintain
widespread mid level clouds and some mountain obscurations across the
region. Widely scattered snow showers will continue to track
southeast across mainly central and southwest MT tonight with some
increase in coverage on Tuesday. VFR conditions prevail at most
terminals with some brief MVFR possible with the passage of any
showers. There is some potential for more widespread lower cloud
development at N-central MT terminals later tonight with KCTB having
the highest probability (around 30%) for IFR cigs/vis in low clouds
and potentially some fog. Hoenisch

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

&&

.PREV DISCUSSION...
/ISSUED 517 PM MDT Mon Mar 25 2024/

A moist northwesterly flow aloft will maintain below average
temperatures and periods lower clouds/scattered areas of light
snow for the next 24 to 36 hours. Partial clearing continues to
take place in a northwest to southeast fashion this afternoon,
though the far eastern portions of N-Central/Southwest Montana may
hang onto to some low stratus and patchy light snow for a
majority of the afternoon. A few more isolated snow showers may
develop farther west with diurnal heating, particularly over
higher terrain, but low/mid- level lapse rates around 5 to 6 C/km
aren`t very supportive for appreciable development.

There will be some opportunity for patchy fog development this
evening and tonight for portions of the plains and some
central/southwest valleys, but clouds streaming ahead of an
approaching shortwave are expected to prevent this from becoming a
widespread/ long term concern. Regardless, there are some
isolated areas with probabilities approaching/exceeding 50% for
visibility reductions below 1 mile through midnight or so, mostly
in the eastern Glacier/western Toole county area.

Clouds will increase again heading into the overnight hours with
areas of light snow developing by day break. There`s nothing
really impressive at all about this system, other than the impacts
are looking to occur during the morning hours on Tuesday when
road surfaces are most likely to carry thin layers of snow/ice.
Snowfall probabilities support accumulations ranging from trace
amounts to as much as an inch or so, highest over or near higher
terrain. More snow shower activity is expected throughout the day
on Tuesday, though impacts will be lessened by increasing diurnal
heating. Temperatures begin to moderate on Tuesday, though the
traditional cooler areas along the Hi-line and adjacent river
valleys will struggle to surpass the 20s again.

Low amplitude transient ridging builds in for Wednesday,
resulting in a more zonal flow aloft and increased west to
southwesterly surface winds. The synoptic environment is initially
not supportive of wind gusts higher than 40 mph, but there will
be a short window for blowing/drifting snow along the Rocky
Mountain Front and adjacent high plains Tuesday night into early
Wednesday before temperatures rise above freezing. The
significance of this depends on whether Tuesday`s highs are able
to reach and exceed the freezing mark, and currently the
probabilities for readings less than freezing in that area are
generally running well less than 50% Tuesday afternoon. This
situation will continue to be monitored over the next 24 hours and
the appropriate actions will be taken if either winds increase
early or temperatures fail to rise sufficiently to avert impacts.
Temperatures warm further on Wednesday and the aforementioned
winds will expand onto the plains and portions of Southwest
Montana. - RCG

As quick as the ridging builds in Wednesday it will begin to be
displaced by broad upper level troughing heading into Thursday
through the early weekend. The first sign of this transition will
be a shortwave ejecting out of the broad trough across the Pacific
NW Thursday within a southwesterly flow aloft. This will re-
introduce chances for precipitation for most on Thursday into
Thursday night along and behind a Pacific cold front. Given
temperatures behind this front don`t look to fall too much, a mix
of rain and snow looks most likely at lower elevations, though
details on specifics will need to be worked out as confidence in
timing of precipitation increases. The chance for 0.25" liquid
equivalent precipitation between Thursday morning and Thursday
night is only up to 20% at lower elevations.

Looking toward Friday and next weekend, the pattern aloft becomes
a bit more complicated. The broad Pacific NW trough splits, with
most of its structure diving southward becoming a cutoff low off
the coast of California. Another portion of this trough will shift
eastward toward the Northern Rockies, eventually merging with
another trough diving southeastward out of northwestern Canada
late this weekend. The main takeaway is that an unsettled pattern
looks to remain Friday into the weekend, with temperatures falling
to a bit below average. At this point, no one day looks to be
particularly precipitation laden, but the chance for precipitation
will be around until upper level ridging looks to build in late
weekend or early next week. -AM

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  16  36  25  48 /  30  40  10   0
CTB  11  33  22  44 /  20  20   0   0
HLN  25  46  27  52 /  20  50  10   0
BZN  20  44  21  50 /  30  50  20   0
WYS  11  37  15  37 /  20  80  30  10
DLN  24  43  23  46 /  10  60   0   0
HVR   7  27  10  43 /  30  40   0   0
LWT  12  34  21  46 /  30  60  20   0

&&

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

$$

http://www.weather.gov/greatfalls


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