Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 251035
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
335 AM MST Sat Feb 25 2017

.DISCUSSION...

Today through Monday...A subtle shortwave feature crossed southwest
MT early this morning and produced accumulating snowfall over Bozeman
and surrounding areas. This area of snow is exiting to the east as
an elongated upper level trough sweeps through the state today.
Downslope westerly winds strengthen behind the trough this
afternoon. Most areas will remain dry, but isolated to scattered
snow showers should be expected today and tonight over elevated
terrain. On Sunday morning attention turns to a vigorous shortwave
trough digging straight south along the British Columbia coast
into the PacNW. Backing winds aloft turn to west-northwest and
direct moisture across the northern Rocky Mountains. At low
levels, cold advection directs a shallow Canadian airmass into
North- central MT. The combination of shallow upslope flow and
mid-level overrunning aloft will produce widespread light snow
Sunday afternoon through early Monday. Snowfall rates increase
Sunday night as the system turns inland and moves just south of
our forecast area. Winter weather headlines may be needed on
subsequent shifts with potential hazards for Monday morning
travel. However, heavy snow is not anticipated as this system
moves quickly with snow tapering Monday afternoon. PN

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 0556Z.

An approaching shortwave (located over southern BC/AB as of 06Z)
will continue to sweep SE across the forecast area over the next 24
hrs or so. Ahead of it, low/mid level moisture will continue to lead
to scattered SHSN and SCT/BKN low/mid level clouds. Confidence in
SHSN impacting terminals is highest for KEKS/KBZN based on latest
obs/satellite trends. As the s/w moves through, a period of gusty
winds will likely develop at most, if not all, terminals. Drier
air/downsloping effects should lead to a decrease in SHSN activity,
especially across central MT. Overnight, there is still some
potential for BR/FG at KCTB/KHVR, but lingering low/mid level clouds
and a gradual increase in winds may tend to limit this potential,
but conditions will be monitored through the night. Martin

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  34  18  27  10 /  10  30  60  60
CTB  31  16  21   5 /  10  50  50  50
HLN  30  14  27   8 /  10  30  40  60
BZN  28   9  27  10 /  70  20  30  40
WEY  16   0  18   7 /  50  40  40  70
DLN  25   9  24  11 /  30  20  30  30
HVR  30  18  27  11 /  20  20  20  40
LWT  27  17  27  11 /  20  20  40  70

&&

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

$$

weather.gov/greatfalls



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