Area Forecast Discussion
Issued by NWS Great Falls, MT

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343
FXUS65 KTFX 252131
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
231 PM MST Sat Feb 25 2017

.DISCUSSION...

Tonight through Monday...A shortwave trough over northern BC and
vicinity this afternoon is expected to move southeastward and cross
our CWA Monday morning through afternoon. At the surface, a cold
front accompanying the shortwave is expected to advance southward
across the Canada border Sunday morning and should then stall along
the mountains in vicinity of Great Falls and Helena Sunday evening.
Lift ahead of the approaching shortwave trough amidst sufficient
moisture should trigger periods of light snow across the CWA during
the period. In addition, enhanced lift and pockets of weak
instability along the cold front are expected to trigger a narrow
band of heavy snow along the Rocky Mountain Front later Sunday
morning through evening. Thus, issued a winter weather advisory for
the Northern and Southern Rocky Mountain Front, including Marias
Pass. Snowfall rates may reach 1 inch per hour within the snow band,
resulting in a brief burst of heavy snow and difficult driving
conditions. This southward-moving snow band may extend farther
eastward and impact much of the North-Central MT plains for a short
period of time Sunday. However, confidence in this scenario is low.

Will have to monitor the central third of our forecast area for
steadier snow Sunday night into Monday, where enhanced lift and
somewhat heavier snowfall rates are possible along the stalled
front. Also, some mesoscale model guidance suggests low- to
midlevel frontogenetical forcing for ascent ahead of the shortwave
trough may trigger localized snow bands over far-southern
Southwest MT Sunday evening into Monday. Will hold-off on issuing
highlights for these areas, but later shifts will have to
reevaluate steadier snowfall potential in these areas. Below-
normal temperatures are expected throughout the period.
Jaszka


Monday Night through Saturday...Upper level trough axis shifts east
across the Northern Rockies and MT Monday night and Tuesday with
weak low pressure tracking east through central MT. Moisture is
fairly limited but a marginally unstable airmass and weak energy
associated with the upper trough should provide enough lift for
scattered snow showers continuing through Tuesday before drier and
more stable air moves in with a building upper level ridge Tuesday
night. Fast moving shortwave and upper level jet push east along the
US Canadian border Wed/Wed night for a period of increasing winds
and moderating temperatures. Some cold air will spill back south
across northern zones Wednesday night through Thursday morning
behind a clipper type surface low that moves east into the Dakotas
this period. Warming ensues for Thursday and Friday as upper level
ridge rebuilds ahead of the next shortwave moving in from the Gulf
of AK. Medium range models continue to advertise fairly deep surface
low emerging across the Canadian Prairies Friday night as this
energy moves across the Rockies with a strong upper level jet
punching east across MT. This is a favorable setup for strong winds
across the region with very strong winds currently depicted by GFS
model, though EC/CMC solutions are not as extreme at this point.
Situation will continue to be monitored through the upcoming week.
Hoenisch

&&

.AVIATION...
UPDATED 1735Z.

Weak disturbance aloft will move over Montana today for scattered to
broken mid- and high-level clouds. Despite the clouds, widespread
VFR conditions will prevail except for partial mountain obscurations
at times. Canadian surface cold front arrives late Saturday night or
earl Sunday morning for increasing low clouds and areas of light
snow. Snow is expected to become widespread across north central
Montana after 12Z with IFR/MVFR conditions prevailing beyond end of
the forecast period. mpj

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  21  28   9  24 /  30  70  60  40
CTB  19  21   4  18 /  40  70  50  40
HLN  20  29   8  24 /  20  60  60  30
BZN  16  27  11  25 /  10  20  30  40
WEY   6  18   7  21 /  40  40  70  60
DLN  13  25  12  26 /  10  20  30  30
HVR  20  27  10  23 /  30  30  50  30
LWT  18  27  11  23 /  20  40  60  40

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from 2 AM to 11 PM MST Sunday Northern
Rocky Mountain Front.

Winter Weather Advisory from 8 AM to 11 PM MST Sunday Southern
Rocky Mountain Front.

&&

$$

weather.gov/greatfalls



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