Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 271120
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
520 AM MDT Wed Mar 27 2024

...Aviation Section Updated...

.SYNOPSIS...

Temperatures will take another step warmer today under increasing
south to west surface winds. A Pacific cold front passes across the
region Thursday, re-introducing chances for precipitation across the
region. There will be the potential for brief but intense snow
showers across Southwest Montana valleys along this cold front. A
cooler and unsettled weekend looks likely.

&&

.DISCUSSION...

Today and Tonight... Upper level ridging is building in across the
Northern Rockies in advance of a broad Pacific trough. As a result,
temperatures will climb to near average today, though it will
come at the expense of increased south to west surface winds.
Given the late-March sun angle and recent temperatures above
freezing along the Rocky Mountain Front, confidence in any blowing
snow is low, even with gusts exceeding 40 mph at times along the
immediate eastern slopes this morning. Before winds increase
across eastern portions of the plains this morning, recent
snowmelt and relatively clear skies will promote some patchy fog.
Any fog that forms looks to diminish through the morning as
daytime heating and winds begin to pick up.

Although ridging is building in, there is a weak embedded disturbance
that will bring a non-zero chance for some light snow showers along
the Continental Divide this morning.

Thursday... Upper level ridging will exit eastward as quickly as it
built in Thursday as an embedded wave within southwesterly flow
aloft ejects from the Pacific trough Thursday. A Pacific cold front
will accompany this wave, re-introducing chances for
precipitation across the region. Ahead of the Pacific front there
looks to be primarily light snow showers across terrain in
Southwest Montana Thursday morning. As the Pacific front arrives,
a period of more intense snow showers looks likely, especially
across the Madison and Gallatin ranges south of Bozeman. Forecast
guidance suggests road temperatures will be above freezing through
much of the day from mid-morning onward, leaving doubt as to how
much impact this narrow window of heavier snow showers will have.
Given uncertainty with respect to timing of the front and
associated heavier snow impacts on roadways in the mountains, I
have elected to hold off on a Winter Weather Advisory at this time
for zone 330 (Mountains south of Bozeman).

The Pacific front will raise additional concerns at valley floors
across Southwest Montana. Forecast soundings suggest that
precipitation rates (Associated with cooling temperatures at the
surface) along this front may be such that snow mixes in with rain
at valley floors or perhaps be the dominant precipitation type along
and behind the front for a brief period (Perhaps up to an hour or
so). Overall this raises a low confidence (Around a 20% chance) but
potentially high impact scenario across Southwest Montana valleys
for snow squalls. Uncertainty largely stems from issues with the
exact timing of the front (Earlier in the day would limit any
potential instability), but stems from winds along and behind the
front as well.

Elsewhere confidence is even lower for snow at lower elevations, but
trends will need to be monitored over the next day or so.

Friday through Sunday night... A broad upper level trough off the
coast of the Pacific NW will split, sending most upper level support
southward, setting up off the coast of California Friday into the
weekend. The weaker portion of this splitting trough will progress
eastward across the Northern Rockies, and combine with additional
troughing diving southeastward out of NW Canada this weekend to
result in a generally unsettled pattern, with temperatures falling
back below average. Given most upper level energy will miss the
Northern Rockies Friday into the weekend, confidence in any
appreciable precipitation at lower elevations is low. The chance
for 0.25" precipitation between Friday morning and Sunday night is
largely below 10% at lower elevations, but peaks around 25% in
Great Falls, Bozeman and Lewistown. Chances increase to around 50%
or so across the Rocky Mountain Front, Little/Big Belts and
adjacent island ranges, and across terrain across eastern portions
of Southwest Montana.

Monday into the middle of next week... Ensembles are in good
agreement that a ridge will build in from the west early next week,
allowing temperatures to climb back to near average Monday and above
average for Tuesday. Confidence for this ridge remaining in place
wanes heading toward the middle of next week, with around 40% of the
ensemble space favoring troughing across the region by Wednesday. -AM

&&

.AVIATION...
520 AM MDT Wed Mar 27 2024 (27/12Z TAF Period)

The main concern for today will be for increasing south to west
surface winds across the region. VFR conditions prevail today, with
just an outside shot of fog forming on the plains of North-central
Montana this morning. Mountains will become increasingly obscured
across Southwest Montana tonight as snow showers associated with the
next system approach the region. -AM

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

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  51  35  46  26 /   0  10  70  10
CTB  47  28  44  22 /   0  10  20   0
HLN  53  33  49  27 /   0  20  80  20
BZN  49  30  50  23 /   0  10  90  50
WYS  40  26  40  17 /  20  70 100  50
DLN  48  32  47  24 /   0  20  90  10
HVR  46  25  42  22 /   0  10  40  20
LWT  48  31  49  23 /   0   0  70  30

&&

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

$$

http://www.weather.gov/greatfalls


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