Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 301023
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
323 AM MST Wed Nov 30 2016

.DISCUSSION...

Today through Friday...Area is under a relatively light N/NW flow
aloft this morning between a broad upper level low centered over
MN/WI and a narrow upper level ridge with axis over ID. Dry
conditions will prevail today as the weak/narrow upper ridge pushes
east into MT ahead of a shortwave trough moving into the Pacific NW.
High level clouds will increase from west to east across the
forecast area this afternoon and evening as a narrow band of
moisture within a deformation zone shifts east across the region
ahead of the ridge axis. The Pacific trough continues into the
Northern Rockies late tonight then drops SE across western MT and SE
ID Thursday and Thursday night. Lift and moisture are not very
impressive with this system, but the increase in cyclonic and
somewhat unstable NW flow should be enough to provide a decent
coverage of snow showers Thursday and Thursday night, particularly
over the Mtns of western and SW MT where 1-3 inches of snow
accumulation is possible. Central MT Mtns will likely see the best
chance for for snow showers Thursday evening as the wave passes by
to the S and flow turns to the N/NW. Snow showers will be more
isolated to scattered in coverage across the valleys/plains where
any accumulations should remain under an inch Thursday/Thursday
night. Drier air moves in from the NW Friday as a positively tilted
upper level ridge moves from the Pacific NW to the Northern Rockies.
Temperatures will remain near seasonal averages through the rest of
the work week. Hoenisch

Friday night through Wednesday...Our warm and mainly dry pattern
looks to end in the long term period. Ridging pattern breaks down
Friday night and brings in quick and moist westerly flow. Scattered
light snow showers will be possible into Saturday morning as a
result. A weak clipper type disturbance then looks to bring another
shot of snow showers...possibly mixed with rain at times...Saturday
afternoon and evening. Accumulations through the day on Saturday
look to be light. In addition strong 700 mb winds...near 50 knots at
times...could bring some strong winds to border line High Wind
Warning criteria at times...mainly Saturday morning into the
afternoon hours. A large progressive trough then looks to influence
the area Saturday night into Sunday morning as it comes onshore from
the Pacific NW. This will stream ample moisture and provide
widespread snow showers to the region. As this wave moves across the
state Sunday afternoon through Sunday night...it is becoming more
and more likely widespread accumulating snow is to be expected for
our CWA. The best chances now look to come across the northern half
of the CWA...although most areas will see snow. Increased pops to
high chance and likely to areas with the best chances. Models do
indicated moderate snow rates will be possible at times into Monday
morning. The main disturbance will then exit the region Monday
night...however...we find ourselves in an unsettled pattern with a
large broad trough in the region...extending all the way south to NV
and UT. This combined with lingering moisture could bring at least a
slight chance of light snow showers Monday night through
Tuesday...and possibly into Wednesday...although with less coverage.
Temperatures will also be on a decline through the long term. Near
average temps will be found through Sunday. With the potential for
widespread accumulating snow...highs will then struggle to get into
the 20s on Monday...and possibly only the teens on Tuesday and
Wednesday. Lows could even get near to below zero later in the long
term period. Again...prepare for a dramatic shift in weather
conditions after Saturday...with the return of winter conditions
Sunday into next week. Anglin

&&

.AVIATION...Updated 0535Z.

High pressure will will keep the air mass dry tonight although low
level moisture across the northern portions of the region,
especially KHVR, could cause local IFR conditions due to low clouds
or fog towards morning. Elsewhere, VFR conditions will prevail
through through Wednesday noon. A low pressure shortwave will move
through the Pacific Northwest tonight and moisture will increase
east of the Rockies Wednesday. Showers over the Rockies could cause
some obscuration by morning, and by afternoon scattered showers are
expected across the Rockies and Southwest Montana. Local MVFR
conditions are expected near showers.

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  37  26  39  24 /  10  20  30  40
CTB  36  24  34  22 /  10  20  30  20
HLN  38  22  40  20 /  20  20  30  20
BZN  33  21  35  21 /  20  30  30  30
WEY  23   9  26   5 /  30  40  50  30
DLN  32  20  33  15 /  20  30  30  20
HVR  32  20  34  21 /   0  20  20  20
LWT  36  22  35  23 /   0  30  30  40

&&

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

$$

weather.gov/greatfalls



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