Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 250001

Area Forecast Discussion
National Weather Service Great Falls MT
459 PM MST Fri Feb 24 2017

Aviation Section Updated


Tonight through Sunday...This afternoon we find ourselves stuck in
a weak unstable pattern just enough to produce scattered snow
showers. Abundant moisture is still in the region trapped under
general weak ridging. However...we also find central and northern
portions in weak unstable NW flow...while a sfc low in ID/southern
MT brings lift to our southern CWA. The result will be chances for
scattered snow showers across much of the CWA this evening through
tonight. Models indicate that sw portions could see some moderate
snow at times...however...impacts should remain below advisory
criteria. With little change to the airmass...more patchy fog will
be possible for Saturday morning...mainly along the Hi-Line.
Saturday will see a weak shortwave and cold front slide across the
CWA...bringing more scattered light snow...mainly to the central
and southern portions...but at the same time break this weakly
unstable pattern we are in. This does however open the door for
another progressive system Saturday night into Sunday. A cold
front will sag south out of Canada while a large trough across
the northwest brings moist southwest flow to the region. This
will result in a better chance of widespread accumulating snow to
our region. Some areas could even see moderate snow at times under
frontogenesis banding by Sunday afternoon and evening.
However...overall accumulations will be in the 1 to 4 inch
range...and will hold off on any highlights at this moment. Did
however raise pops to introduce likely mentioning where the best
chances for snow currently appear. Temps were not quite as cold as
expected this morning...and feel this trend may continue for
tomorrow morning with only partial clearing expected tonight. With
a series of fronts slightly cooler temps are then expected each
day through the short term...and the whole short term should see
temps below normal. Some breezy winds will also be possible this
weekend from the passing disturbances. They should remain below
high wind criteria...but gusts 30 to 40 mph are possible. Anglin

Sunday night through Friday`s main forecast challenges will be the
chance for multiple, albeit light, shots of snow and stronger winds.
Medium to long range models continue to be in fairly good agreement
with the overall large scale pattern, which is very progressive in
nature (transitory weak ridging and quick moving long/shortwaves).
For the beginning of the medium range, a fast moving longwave will
dive south and east along the British Columbia Coastline to
Southwestern Oregon by Sunday night. This longwave feature will then
transition to the east into the Northern Great Basin by Monday
morning. Light snow is expected to overspread much of the forecast
area Sunday night within the WAA region of the approaching longwave.
Snowfall amounts look to be light Sunday night into Monday across
the Plains, with generally less than a couple of inches. Focus then
shifts to Tuesday through Friday, as a series of weak clippers move
across Southern Alberta and Saskatchewan. These clippers will bring
with them the chance for more light snow/snow showers Tuesday
through Friday to portions of the forecast area, but most noticeably
strong winds. At this time, strong winds continue to appear likely
from Tuesday afternoon through Wednesday evening, and then again
Thursday night through the day on Friday. While the Tuesday through
Wednesday event will be quite breezy in nature, am most concerned
about the Thursday night through Friday event. For the Thursday
night through Friday time frame, westerly downsloping winds of 25 to
50 knots with gusts approaching 65 knots appear possible along the
Rocky Mountain Front (especially across Western Lewis and Clark,
Teton, and Pondera counties). - Moldan



A moist and unstable NW flow will continue to bring scattered SHSN
to much of the area over the next few hours. However, a decreasing
trend is expected tonight with the loss of daytime heating. Any SHSN
that moves over a terminal could bring a sudden reduction in VIS (as
has been the case at KLWT where a recent shower lowered the VIS to
3/4SM). However, these reductions in VIS should be short-lived given
the showery nature of the snow. Across SW MT, the threat of -SHSN
will likely linger longest due to a weak SFC low in the area. In
fact, SHSN may continue on into SAT near KEKS/KBZN while the low is
in the vicinity. An upper level shortwave will pass through the area
on SAT bringing drier air with it. This should put an end to the
SHSN activity from NW to SE. Breezy conditions are likely to develop
in its wake as well, especially SAT afternoon. Of note, BR/FG will
once again be possible overnight at KCTB/KHVR with lingering low
level moisture, light winds, and less cloudcover. VIS/CIG may end up
even lower than currently forecast and this potential will be
closely monitored through the night. Martin


GTF  14  29  19  28 /  20  10  20  60
CTB   8  26  16  22 /  10  10  20  50
HLN  12  28  14  27 /  20  10  20  40
BZN  11  26   9  26 /  30  30  20  30
WEY   6  16   0  17 /  40  40  30  30
DLN  10  23   9  23 /  30  30  10  30
HVR  17  29  18  28 /  20  30  20  30
LWT  13  26  15  28 /  40  20  10  40



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