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000
FXUS65 KTFX 162330
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
530 PM MDT Tue Apr 16 2024

Aviation Section Updated

.SYNOPSIS...

A Canadian cold front will bring periods of snow and gusty northerly
winds tonight into Wednesday, with the heaviest snow over mountain
areas and their adjacent northerly facing foothills. A cold and
moist air mass will then maintain welL below average temperatures
and isolated to scattered snow showers through Friday before more
seasonable temperatures return for the weekend.

&&

.DISCUSSION...

Remainder of this afternoon through Friday...Aside from gusty
winds and a few scattered showers this afternoon, the primary
concern will be will be falling temperatures and periods of snow
tonight into Wednesday. Ongoing mid- level cold air advection will
continue, with H700 temperatures between -10 to -15C reaching
Southwest Montana sometime this evening. This will result in
periods snow tonight into Wednesday, heaviest over the
Gallatin/Madison Mountains. There are plenty of uncertainties for
accumulating snow over the lower elevations, but given northerly
flow and the aforementioned H700 temperatures, I felt it necessary
to add a Winter Weather Advisory for the Gallatin valley due to
the accumulating snow potentially impacting the Wednesday morning
peak travel time. Although confidence was too low to add other
lower elevations such as the Dillon area, these areas may also
experience a brief period slushy snow impacts.

Farther north, snow initially develops along the Northern
Continental Divide before spilling southward into the plains via a
secondary cold front. H700 flow will generally favor more of a
northwesterly direction, but will increasing become more northerly
between midnight and 3 am MDT. This will increase snowfall along
the traditional northerly upslope areas along the Central MT
highway 200 corridor during the late overnight hours into
Wednesday morning. There`s little agreement among model guidance,
but the overall pattern favorable for snow and some gusty winds up
to 40 mph in these areas hasn`t changed much over the last 24
hours or so. Similar to the Gallatin valley mentioned above, a
Winter Weather Advisory has been posted for Cascade/Judith Basin
Counties and the Snowy Mountains.

Snow is expected to diminish sometime Wednesday morning for most
locations, but periods of accumulating snow will persist through
the day over the Gallatin/Madison Ranges and cold air advection
will maintain snow shower activity and cold temperatures
elsewhere. Highs will struggle to surpass the middle and upper
30s. The responsible cold trough will remain over the region for
the remainder of the work week, with passing disturbances
continuing the well below average temperatures and isolated to
scattered snow shower activity. - RCG

Saturday through next Tuesday... A broad high pressure ridge is
forecast to move into the western United States during this
period, as a low pressure trough digs south out of the Gulf of
Alaska just off the Pacific coast. This set-up should help warm
temperatures from just below seasonal averages on Saturday to
around 10 degrees above normal by Tuesday. This period should also
remain fairly dry, but weak disturbances ejecting from the
Pacific trough may bring periods of mainly mountain precipitation
and gusty westerly downslope winds. - Brusda

&&

.AVIATION...
530 PM MDT Tue Apr 16 2024 (17/00Z TAF Period)

Primary concerns for the TAF period continues to be gusty winds and
snow development tonight. Rain showers have moved into the Bozeman
airfield that should continue periodically through tonight,
transitioning over to a rain and snow mix between 2z and 5z. Gusty
north to northwesterly winds continue through the early evening
hours tonight and concerns for blowing snow tomorrow afternoon for
the Cut Bank airfield will depend on how much snow remains on the
ground after tonight. After 18z, the majority of North Central and
Central Montana airfields conditions should begin to improve and
snowfall diminishes. Mountain obstruction continues through the TAF
period. Webb

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

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  28  37  23  39 /  80  80  30  20
CTB  24  35  21  36 /  70  60  10  10
HLN  30  37  25  41 /  80  80  20  10
BZN  25  37  17  40 /  80  80  20  10
WYS  22  34   8  37 /  90  70  30  10
DLN  26  36  20  40 /  70  60  20  10
HVR  29  39  24  40 /  40  60  20  20
LWT  25  34  20  35 /  70  80  30  20

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 6 AM MDT Wednesday for East
Glacier Park Region-Northern High Plains.

Winter Weather Advisory from 9 PM this evening to noon MDT
Wednesday for Big Belt, Bridger and Castle Mountains-Cascade
County below 5000ft-Gallatin Valley-Gates of the Mountains-
Judith Basin County and Judith Gap-Little Belt and Highwood
Mountains-Snowy and Judith Mountains-Southern High Plains-
Southern Rocky Mountain Front-Upper Blackfoot and MacDonald Pass.

Winter Storm Warning until 6 PM MDT Wednesday for Gallatin and
Madison County Mountains and Centennial Mountains.

&&

$$

http://www.weather.gov/greatfalls