Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 041616

Area Forecast Discussion
National Weather Service Billings MT
916 AM MST Sun Dec 4 2016

Winds have increased and we are seeing gusts in the 40s at
Livingston again. Though pressures are falling across the region
and the IDA-LWT gradient remains only about 10mb, would expect an
increase in mountain top wind this afternoon in advance of
approaching cold front, so it is possible LVM could see some
enhanced 50+mph gusts later today. Will let the wind advisory ride
for now and take another look this afternoon. Have adjusted winds
down a bit for the morning hours in the gap areas.

Snow is falling at Cooke City per web cams and nearby snotels show
about 3 inches of accumulation so far. Snow will intensify over
the Beartooth Absarokas as ascent and instability increase later
today, so winter storm warning appears on track. Have maxed out
pops over the high terrain today.

Shower activity should generally increase otherwise across lower
elevations today, with best ascent and a transition from rain to
snow showers tonight. 12z models coming in shift the baroclinic
zone south a bit faster, so have tweaked pops late tonight and
early tomorrow to account for this slight change in timing. Think
Billings will see less than an inch tonight, perhaps less than a
half inch, with higher amounts (1-3") in our southern upslope
areas into early Monday. Greater snow potential for Billings
itself seems to be Monday due to convergent/unstable banding as
cold air advects from the north.



.SHORT TERM...valid for Tdy and Mon...

This morning, winds have generally been gusting in the 30 to 40
mph range from Livingston to Nye. Gap winds will begin to ramp up
again through the Livingston, Big Timber, and Nye areas peaking
this afternoon with gusts 50 to 60 mph possible.

Forecast looks on track for the Low pressure system progged to
move into the western mountains late this afternoon. Frontal
forcing will move precip onto the foothills and Plains in the
late afternoon and early evening hours. Temperatures, which will
be in the upper 30s to low 40s as precip moves in, will quickly
fall into the 20s by Monday morning. As the front moves east, QPF
amounts should be fairly low over the Plains and river valleys,
however the transition from rain to snow combined with quickly
falling temperatures could cause slick road concerns late Sunday
night into Monday.

While we remain confident in larger snowfall accumulations over
the Beartooth/Absarokas (10-12 inches) and Bighorn Mountains (6-8
inches) the snowfall amounts over the Plains remain less
confident. Expecting the best amounts to be from Interstate 90
southeastward toward Powder River county, and even those amounts
should generally be in the 1-3 inch range with this initial round
of snow.

The wildcard in the snowfall amounts will be Monday as arctic air
continues to surge in from the north. Most of the models are in
some agreement that while coverage of snow showers will generally
decrease through the day on Monday, there are some signs of banding
developing northwest to southeast from Golden Valley and
Musselshell counties, through Yellowstone and Big Horn, and down
to Sheridan. It is likely that narrow quasi stationary bands of
snow will develop which could allow for some locally higher
snowfall rates and accumulations during Monday afternoon.

As the arctic air forces in towards the foothills and
northeasterly upslope begins, flurries to light snow will
continue from Yellowstone through Sweet Grass counties and along
the northeastern facing slopes during Monday night. Confident we
will see a blustery and cold day Monday afternoon with single
digit lows across the foothills and Plains by Tuesday morning.

.LONG TERM...valid for Tue...Wed...Thu...Fri...Sat...

The coldest air of the season will be settling into the region
for Tuesday and Wednesday with a 1050mb surface high moving into
southern Canada. This will drive 850mb temperatures of -22c into
eastern Montana. Highs on Tuesday and Wednesday will be in the
single digits with lows below zero both nights. Northwest winds
will stay up enough to produce wind chills of 15 to 30 below over
southeast Montana Tuesday through Wednesday night.

A fast moving system will spread some overrunning snowfall into
western and central zones Tuesday. Dynamics of the system were
pushing well to the south, but very cold air in place with upslope
flow and lingering moisture, should be enough for snow showers.
Will be a break in snowfall on Wednesday, but very cold air will
remain in place. The arctic starts to move off the higher terrain
early Thursday and drives east, allowing for warmer air to push in
from the west. Models have backed off some on this timing and
actually, the ECMWF was very slow in doing this, so lowered high
temperatures on Thursday.

Another fast moving system is progged for Friday and have spread
PoPs in from west to east Friday and Friday night. This system may
be able to dislodge the arctic air briefly Friday through Sunday,
before the next batch of arctic air spills south for early next
week. All in all, looks chilly for the week ahead with a brief
warmup for next weekend. After that, may be looking at another
cold outbreak. TWH


Clouds will be on the increase today as a strong arctic front
approaches the forecast area. VFR conditions will prevail today.
Southwest winds near KLVM will continue to be gusty at times,
gusting around 35 to 45 kts. The Beartooth and Absaroka mountains
will be obscured as snow moves in and the snow will be heavy at
times. Rain/snow showers will develop over the west this afternoon
and spread east this evening. Rain will change to snow quickly
this evening as arctic air invades. Conditions will fall to
IFR/LIFR in areas of heavier snow, mainly south and west of a KLVM
to KBIL to KSHR line. TWH/Hooley



    Tdy Mon     Tue     Wed     Thu     Fri     Sat
BIL 045 021/024 005/006 907/004 905/016 010/027 020/032
    3/W 77/J    42/J    11/B    11/U    22/J    32/J
LVM 043 020/022 001/009 909/005 902/019 017/035 022/035
    6/W 85/J    33/J    11/B    11/B    23/J    42/J
HDN 047 022/026 005/008 908/003 910/016 006/024 013/032
    3/W 76/J    31/E    11/B    00/U    12/J    32/J
MLS 044 020/025 003/009 906/003 909/009 000/017 007/024
    2/W 63/J    21/E    10/B    00/U    12/J    32/J
4BQ 043 020/026 002/008 909/003 911/012 001/020 010/028
    2/W 67/J    21/E    11/B    00/U    01/B    32/J
BHK 041 018/024 002/007 907/002 912/005 903/014 004/020
    1/E 55/J    21/E    10/E    00/B    01/B    31/E
SHR 045 021/025 002/011 909/007 910/014 006/030 016/031
    2/W 77/J    31/B    11/B    01/U    11/B    42/J


MT...Winter Weather Advisory in effect from 6 PM this evening to 6
      PM MST Monday FOR ZONES 28>30-34>42-56>58-63>66.
     Wind Advisory in effect until 6 PM MST this evening FOR ZONES
     Winter Storm Warning in effect until noon MST Monday FOR ZONE
WY...Winter Weather Advisory in effect from 6 PM this evening to 6
      PM MST Monday FOR ZONES 98-99.


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