Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 050411
AFDBYZ

Area Forecast Discussion...Updated
National Weather Service Billings MT
911 PM MST Sun Dec 4 2016

.UPDATE...
Dynamic frontal system pushing through our CWA this evening. Came
through Billings around 8 PM. Instability and frontogenesis
produced some small pockets of sleet/ice pellets from Hysham to
just east of Billings which briefly led to slick roads according
to a few spotters. However, westerly winds and speedy frontal
movement has limited overall precipitation across central zones
including Billings. Still a chance of precipitation this evening
in Billings, but primary forcing then sets up mainly along north
facing slopes of the Beartooths/Pryors/BigHorns after midnight.

For this update package we increased PoP`s over and ahead of
frontal activity this evening, then lowered PoP`s over northern
tier of our CWA late and continued to focus on southern zones
later tonight. We lowered snow amounts a bit over the central
zones as well where forcing and west/northwest winds will make it
tough for widespread accumulation. We are banking on snow bands
developing tomorrow for best chance of accumulating snow in
Billings and surrounding areas at this point. BT

&&

.SHORT TERM...valid for Mon and Tue...

Latest surface analysis shows pressure falls in south central MT,
with a Pacific cold front near HLN-DLN, and a Canadian front
recently passed through CTB. Livingston has recently seen gusts
increase to in excess of 50 mph during this favored pre-frontal
time, so will let wind advisory ride for the remainder of the
afternoon. Winds will decrease significantly with the onset of
cold advection this evening.

Snotels near Cooke City show 6-10" of snow since Saturday evening,
and it continues to snow steadily over the high terrain, with more
accumulation to come thru the evening as Pacific shortwave
approaches and instability increases. Will make no changes to the
winter storm warning for the Beartooth Absarokas.

Pacific and Canadian fronts will somewhat phase together and
allow for cold advection into our cwa later tonight. Brief period
of synoptic forcing at the same time will allow for rain to snow
showers tonight. Latest models have trended quicker with the north
to south evolution of the precipitation tonight, and have adjusted
pops accordingly. Greatest snow accums will be across our south
per the NW upslope winds. Have lowered amounts to the north
including Billings tonight, but main story is the rapidly falling
temps and icing over of roads expected. Will continue to stress
this in our messaging, especially with regard to the Monday
morning commute, though the initial stage of snow will have mostly
ended by sunrise tomorrow.

Convergent NW-flow snow showers look to be a good bet for tomorrow
as models continue to suggest in the lee of the Belts/Snowies to
our north. This will be very interesting as we will see
instability thru a dendritic layer which will fall to the
850-700mb layer by tomorrow, so expect snow showers to be locally
heavy. These NW-SE oriented bands could impact Billings from late
morning into the evening. This is something to keep an eye on and
have introduced a weather story to cover the snow shower potential
tomorrow. Further east it looks like we`ll see a period of lighter
snow wrap around the mid level low in western ND, but this will be
w/o the instability that exists further west.

Cold air will surge steadily into our cwa as pressures build from
the north Monday and Tuesday, with pressures to 1040+mb by Tuesday
night. Periods of light snow will likely impact our west/south
late Monday night thru Tuesday as shortwave moves from the Pac NW
to central rockies, clipping our SW cwa. Must keep in mind that
temps will be quite cold and dendritic layer will be shallow.

Temps will not climb out of the 20s tomorrow, then be mainly in
the single digits by Tuesday as the arctic airmass settles in.
There should be enough NW wind for wind chills to -20F or colder
in our far east by Tuesday night.

JKL

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


The forecast area will see a break in the snow by Wednesday but
very cold temperatures will continue. Models try to scour the
arctic off the higher terrain Thursday and Friday allowing for
warmer air to push in from the west. Another fast moving system is
progged for Friday bringing a return chance for light snow or snow
showers Friday into Friday night. Models try to keep the arctic
just east and north of our forecast area next weekend with some
fluctuations of a baroclinic zone across the eastern portions of
the state. We will keep temperatures around normal for most areas
along with a chance of snow showers but below normal readings out
toward the Dakota borders. Hooley
&&

.AVIATION...


Rain/snow showers are expected to change to snow yet this evening as
arctic air moves across the forecast area. VFR conditions will
give way to MVFR/IFR conditions late tonight. The mountains will
remain obscured due to snow with heavy snow likely for the
Beartooth/Absarokas. AAG

&&

.PRELIMINARY POINT TEMP/POPS...

    Mon     Tue     Wed     Thu     Fri     Sat     Sun
-----------------------------------------------------------
BIL 023/025 005/007 907/004 904/016 012/027 020/032 018/036
    57/J    42/J    21/B    11/U    22/S    32/S    21/B
LVM 018/022 001/009 909/005 904/017 017/035 022/033 022/036
    84/J    33/J    21/B    11/B    23/S    42/S    22/J
HDN 024/026 005/008 908/003 908/018 010/024 013/031 015/037
    76/J    42/J    21/E    00/U    12/S    32/S    21/B
MLS 024/025 003/009 906/003 907/009 000/017 007/024 010/032
    94/J    21/B    11/E    00/B    12/S    32/S    21/B
4BQ 024/026 002/008 909/003 909/012 002/020 010/028 011/032
    45/J    21/B    11/E    00/U    01/B    32/S    11/B
BHK 023/024 002/007 906/002 911/005 904/014 004/020 006/027
    44/J    21/E    11/E    00/B    01/B    22/S    21/B
SHR 024/025 002/010 909/007 908/014 006/030 016/031 011/034
    57/J    32/J    21/B    00/U    11/B    42/S    11/B

&&

.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...Winter Weather Advisory in effect until 6 PM MST Monday FOR
      ZONES 28>30-34>42-56>58-63>66.
     Winter Storm Warning in effect until noon MST Monday FOR ZONE
      67.
WY...Winter Weather Advisory in effect until 6 PM MST Monday FOR
      ZONES 98-99.

&&

$$
weather.gov/billings


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