Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 092129

Area Forecast Discussion
National Weather Service Great Falls MT
229 PM MST Fri Dec 9 2016


Tonight through Sunday...Bands of very light snow or flurries
continue to weaken this afternoon across north central MT while
radar/observations to the W/SW show the next batch of moisture and
precipitation to impact the region spreading east across Idaho.
Incoming plume of Pacific moisture will bring light snow to SW MT by
this evening with additional bands of light snow developing to the
north across Central MT late tonight through Saturday morning as
shortwave energy now moving into WA state tracks into the Northern
Rockies and MT. Areas along the Hi-line eventually see light snow re-
develop Saturday morning and continue through Saturday afternoon as
this energy tracks across the northern tier of MT. Total liquid
equivalent precipitation amounts through the next 24 hrs ranges from
0.05"-0.15" over the plains and valleys, with 0.15"-0.25" in the
Mtns. With snow to liquid ratios generally around 20:1 or better
expected, this should yield about 1 to 3 inches of snow at lower
elevations with 2 to 5 inches across the mountains over the next 24
hrs with the bulk of the snowfall across central/northern areas
occurring later tonight through Saturday morning. Have expanded the
winter weather advisory across northern counties beginning tonight at
midnight. Main impacts continue to be reduced visibility and
deteriorating road conditions in periods of light snow. Most areas
will continue to see light winds through Saturday with the exception
of some gusty SW winds over the Mtns of SW MT near the ID border.
The westerly flow aloft will begin to erode the cold airmass from
portions of SW MT tonight through Saturday, with some potential for
the cold airmass to briefly retreat north across portions of central
MT Sunday morning, allowing temperatures to rise into the 20s. This
looks be very short-lived however for much of north-central MT as
the cold airmass surges back south Sunday afternoon. During this
period (Saturday night through Sunday afternoon) precipitation will
diminish across all but the western Mtns, where orographic enhanced
snow showers will continue. Hoenisch

Sunday night through Friday...Northwest flow aloft over the Northern
Rockies will bring a continuing chance for snow Sunday night.
Another Canadian cold front pushes southward through North Central
Montana by Monday morning with high temperatures expected to drop
back into the single digits above zero while Southwest Montana
remains in the 20s. By Tuesday, a deep upper level closed low is
expected to be centered over central Manitoba with continued
northerly flow aloft continuing to push the surface cold front
through Southwest Montana along with areas of light snow and gusty
northerly winds. The closed low gradually drifts eastward across
Canada by late Tuesday night into Wednesday morning. From here
models diverge on what happens next. GFS solution keeps cold nw flow
over the region through the end of the work week...with limited
disturbances bringing some chances for light snow at
times...especially Thursday. The GFS solution then brings a more
active pattern by next weekend. The Euro solution has a different
thought. As the low moves out Tuesday night...a weak frontal
boundary could bring some overrunning and light snow to the southern
half of the CWA...the the remainder stays mainly dry and slightly
warmer for Wednesday into Thursday morning. Euro solution is then
dry until Friday when it indicates a shortwave trough moves across
the region and brings widespread snow...with some warming
conditions. The next weekend time period then looks cold with some
lingering light snow. Really tough to say which one wins out at this
point...tried to compromise and place some slight pops in a few
areas to account for either solution with this afternoons update.
Also lowered temperatures for mid next week...given the expected
snowfall and push of arctic air. mpj/anglin


.AVIATION...Updated 1800Z.

An initial band of light snow will begin to diminish across north
central MT this afternoon...however...could still bring light snow
and brief MVFR/IFR to site in a line from KCTB to KGTF to KLWT and
north. Elsewhere will see the return of VFR conditions this
afternoon...with some MVFR cloud decks possible at times. A second
disturbance will bring snow across the south this evening...then
spread north and eastward overnight tonight into Saturday morning.
Snow from this disturbance could also provide prevailing MVFR to
IFR conditions at times during this time frame. Surface winds
remaining generally less than 10 kts across the region through
tonight and tomorrow. With low clouds and light snow...mountain
obscuration is also expected for much of the forecast period. Anglin


GTF  -2   9   9  26 /  70  50  10  20
CTB  -7   1  -2   7 /  50  50  10  20
HLN   7  19  15  30 /  60  50  10  20
BZN  15  25  15  30 /  70  40  40  20
WEY  19  30   7  22 /  90  90  50  40
DLN  17  29  15  29 /  70  40  40  20
HVR  -3   4  -5   8 /  60  70  30  20
LWT   1  15   8  27 /  50  60  20  20


Winter Weather Advisory until 5 PM MST Saturday Broadwater...
Cascade...Central and Southern Lewis and Clark...Fergus...
Jefferson...Judith Basin...Meagher.

Winter Weather Advisory from 11 PM this evening to 5 PM MST
Saturday Blaine...Chouteau...Eastern Glacier...Eastern Pondera...
Eastern Teton...Hill...Liberty...Northern Rocky Mountain Front...
Southern Rocky Mountain Front...Toole.

Winter Weather Advisory until 5 PM MST Saturday Beaverhead...


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