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000
FXUS65 KTFX 312057
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
257 PM MDT Tue Mar 31 2020

.SYNOPSIS...

Cold air moving south into the region along with a moist upper
level weather disturbance moving in from the west will bring snow
or snow showers to much of north-central and southwest Montana
tonight. An area of heavy snow is likely across eastern portions
of north-central Montana this evening, where travel may be
impacted. Much colder temperatures will be widespread on Wednesday
with isolated to scattered showers expected Thursday and Friday,
with below normal temperatures continuing.

&&

.DISCUSSION...

Deep upper level trough/low now centered in western Canada will
remain nearly stationary through the next several days keeping
conditions over MT unseasonably cold and unsettled. Surface cold
airmass continues to spread south over north-central MT this
afternoon while the next round of upper level energy moves in from
the west, resulting in increasing precipitation already over
western portions of the forecast area. Expect snow to intensify
this evening across central MT as the upper level energy moves
across an intensifying lower level temperature gradient behind the
cold front. Placement of these features looks to favor areas from
Judith Basin to Fergus to southern Blaine counties for heaviest
precipitation this evening. Somewhat unstable conditions are in
place as well which could lead to high precipitation rates of
around an inch per hour in these areas. A winter storm warning has
been issued for these areas and in addition to snow, a tightening
pressure gradient between the incoming cold surface high and low
pressure to the SE will produce wind gusts from the NW to around
30 mph. While this area will be the main focus for heavier
snowfall, we are still expecting 1 to 3 inches of accumulation in
periods of snow elsewhere across the forecast area tonight where a
winter weather advisory is in place. Temperatures fall to the 20s
and teens overnight with any wet road surfaces in the evening
likely to freeze up overnight, which could impact some roadways
into Wednesday morning, despite the decreasing trend in
precipitation. Coldest temperatures of the period occur WEdnesday
into Thursday morning with daytime temperatures Wednesday
remaining in the 20s for most areas and potentially falling to the
single digits Wednesday night.

A slow warming trend is expected late this week into the weekend
but temperatures look to remain below seasonal averages.
Diagnostic model solutions for this weekend and early next week
continue to indicate significant divergence with the GFS still
bringing another trough into the northern Rocky Mountains.
Meanwhile, the ECMWF, model ensembles, and the National Blend of
Models (NBM) continue to keep this feature off the West Coast. As
before, I have continued to use the NBM forecast solution for the
weekend and early next week.

&&

.AVIATION...
Updated 1105 AM MDT Tue Mar 31 2020 (31/18Z TAF Period)

Much of southwest and central MT lies in a brief lull in snow
activity early this afternoon but scattered to numerous snow showers
can be expected to develop late this afternoon and continue
overnight with widespread mountain obscurations. A strong cold front
will push south across the area from north to south, starting before
21z at KCTB and reaching KGTF around 23z-00z. Behind the front,
expect low clouds and areas of light snow to produce IFR/MVFR
conditions at times. By evening, widespread snow and low clouds
producing LIFR/IFR conditions will prevail and continue into
Wednesday morning.

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  11  23   4  25 /  90  60  10  10
CTB   7  20   1  23 /  80  40  10  10
HLN  19  31  10  33 /  80  40  20  20
BZN  21  33  12  30 /  80  50  40  20
WYS  14  31   7  30 /  90  70  60  50
DLN  20  34  11  32 /  60  40  40  20
HVR  14  24   0  26 /  80  60  10   0
LWT  12  20   0  20 / 100  80  30  30

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until noon MDT Wednesday above 4500 feet
for Central and Southern Lewis and Clark...Northern Rocky
Mountain Front...Southern Rocky Mountain Front.

Winter Weather Advisory until 6 AM MDT Wednesday Eastern
Glacier...Eastern Pondera...Eastern Teton...Liberty...Toole.

Winter Weather Advisory until noon MDT Wednesday Beaverhead...
Gallatin...Jefferson...Madison.

Winter Weather Advisory until noon MDT Wednesday Cascade...
Meagher.

Winter Storm Warning until noon MDT Wednesday Blaine...Fergus...
Judith Basin.

Winter Weather Advisory from 6 PM this evening to noon MDT
Wednesday Chouteau...Hill.

&&

$$

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