Area Forecast Discussion
Issued by NWS Great Falls, MT

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873
FXUS65 KTFX 270417
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
917 PM MST Sun Feb 26 2017

.UPDATE...
Short term forecast is on track with the next wave of snowfall
developing over central Montana. Only made minor adjustements to
the overnight forecast, extending higher PoPs further east to
match up with the neighbors. Langlieb

&&

.AVIATION...
UPDATED 0030Z.

Mountain obscuration in snow and low clouds to persist through at
least the next 24 hours. Terminal flight conditions will generally
be in the low MVFR/IFR range in low clouds/snow/fog for most of the
area through 15Z or so with occasional LIFR conditions possible. The
only exception will be in some of the Southwest Montana valleys
(KBZN KEKS). Snow will be less widespread there, allowing for mostly
VFR conditions with occasional MVFR/IFR conditions in heavier snow
showers. The weather system responsible for this snow will exit the
area after 15Z for decreasing snow and improving conditions.
Coulston

&&

.PREV DISCUSSION...
/ISSUED 530 PM MST Sun Feb 26 2017/

530 pm update...Have increased snow wording to definite across
Central Montana through most of tonight to reflect current and
expected persistent light measurable snow.  Langlieb/Coulston

Tonight through Tuesday...A shortwave trough over southern BC, the
Pac NW, and vicinity this afternoon should cross our CWA from west
to east between mid-morning and early evening on Monday. As
predominantly cyclonic flow aloft occurs, another shortwave trough
should advance eastward across our CWA during the day on Tuesday. At
the surface, a cold front has stalled along the Big/Little Belts and
Big Snowy Mountains. This front is expected to remain nearly-
stationary across this area through much of Monday morning. By late
Monday morning, the front should begin advancing slowly northward as
a warm front due to weak low-level WAA ahead of the first shortwave
trough. By late Monday evening, southerly to southwesterly flow is
expected region-wide behind this weak warm front. On Tuesday, a
Pacific cold front is expected to cross the CWA as the second
aforementioned shortwave does the same thing, causing predominantly
southerly surface winds to veer to westerly.

The above pattern will support periods of light snow across the CWA,
especially the rest of today into Monday. However, brief periods of
moderate to heavy snow are possible tonight into Monday morning
along and near the stalled front across the central third of our
forecast area. Here, snowfall rates may occasionally reach a half
inch to 1 inch per hour within a narrow band or bands due to
enhanced lift along the front extending through the dendritic snow
growth zone, where abundant moisture is also expected. Thus,
efficient snow production and higher snowfall rates are not out of
the question. Tough to say where exactly the heaviest and most
persistent snow will occur, but Great Falls, Helena, and Lewistown
may experience some heavier snow showers. In addition, periods of
moderate snow are expected along eastern aspects of the Rocky
Mountain Front, along/just north of the Continental Divide in far-
southern Southwest MT, and along the Bridgers due to upslope
flow. Thus, winter weather advisories remain in effect for much of
the CWA the rest of today into Monday. Please see our statements
for additional details, including expected additional snow
amounts.

Later Monday into Tuesday, more snow showers are expected,
especially along the Continental Divide and along the higher terrain
of Central and Southwest MT. Elsewhere, much less precipitation is
expected due to developing downslope flow. Below-normal
temperatures will prevail during the period.
Jaszka

Tuesday night through Sunday...Period begins with a fast NW flow
aloft over the region. Surface low develops east of the Rockies in
AB Tues night and quickly moves SE across eastern MT on Wed.
Increasing winds Tuesday night through early Wednesday with strong
winds possible along the east slopes of the Rockies. Enough snow-
cover will probably be present for potential blowing/drifting snow
issues across western portions of north-central MT, particularly
where winds will be strongest along the Northern Rocky Mtn Front.
Fast W/NW flow aloft continues through the rest of the upcoming week
with next stronger shortwave moving east along the MT/AB border
Friday night. Models continue to advertise favorable pattern for
widespread strong winds in association with this feature
Friday/Friday night but have backed off some with the strength of the
low emerging east of the Rockies on the Canadian Prairies as well as
overall wind speeds aloft. Temperatures will gradually warm through
the later part of the upcoming week before cooling again next
weekend.
Hoenisch

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF   8  22  14  29 / 100  50  20  10
CTB   3  18   7  23 /  70  40  20  20
HLN   6  23  11  27 / 100  40  20  20
BZN  11  25  10  26 /  50  50  30  30
WEY   9  22   4  19 /  80  70  60  60
DLN  12  26  11  25 /  30  30  20  20
HVR  10  22  13  28 /  50  40  20  20
LWT   9  21  10  28 / 100  60  20  20

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 11 AM MST Monday Blaine...
Broadwater...Cascade...Central and Southern Lewis and Clark...
Chouteau...Eastern Glacier...Eastern Pondera...Eastern Teton...
Fergus...Jefferson...Judith Basin...Meagher.

Winter Weather Advisory until 5 PM MST Monday Beaverhead...
Madison.

Winter Weather Advisory until 5 PM MST Monday For the Bridger
Range in Northern Gallatin County in Gallatin.

Winter Weather Advisory until 11 AM MST Monday Northern Rocky
Mountain Front...Southern Rocky Mountain Front.

&&

$$

weather.gov/greatfalls



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