Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 030338
AFDBYZ

Area Forecast Discussion...Updated
National Weather Service Billings MT
838 PM MST Fri Dec 2 2016

.UPDATE...

Snow showers were spreading across western and central
Montana this evening as a weak Pacific front was moving into the
region. Isolated to scattered snow showers will spread across the
CWA overnight into tomorrow morning. Snow accumulations are
expected to be pretty minimal with generally less than an inch of
snow for the plains and an inch or two for the mountains. Main
weather concern continues to be strong crosswinds from Livingston
to Nye as the surface pressure gradient tightens, effectively
increasing the gap winds. KLVM has begun to gust near 50 mph from
the west southwest in the past hour. The Wind Advisory in effect
through 6pm Sunday looks in good shape so will not make any
adjustments with that. Have adjusted pops, winds, sky cover, and
temperatures to current trends. Otherwise, the rest of the
forecast remains on track and the previous forecast discussion and
an updated aviation discussion are below. STP

&&

.SHORT TERM...valid for Sat and Sun...

Minimal changes for the short term forecast period...with main
concern being winds near Livingston and Nye. Winds in Livingston
continue to slow increase today...as the SFC pressure gradient
continues to tighten.

The pressure gradient is progged to tighten significantly tonight
and persist through Saturday morning...allowing for extended
period of advisory types winds. Models continue to favor some
degree of slackening of the gradient Saturday afternoon (with the
passage of a Pacific front)...but point to the gradient
tightening again Saturday night for another round of strong winds.
Therefore...The High Wind Advisory will remain in place from this
evening into Sunday...with mention of a brief lull in activity
Saturday afternoon.

Pieces of energy and Pacific moisture continue to stream across
the region through the period. The majority of precip will stick
in the high terrain...but there is a Pacific front progged across
the region Saturday (responsible for lull in wind for
Saturday)...that should spread at least a slight chance of precip
across the region. The Arctic front begins push into the area
Sunday...and across the region through Sunday night. Changes to
the forecast centered around fine tuning pops for arctic
system...with most significant changes to raise pops Sunday night.

Temps through the short term will remain above normal...with
highs in the 40s. AAG

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

Are you ready for winter?

Initial Pacific shortwave will pass east as we begin to advect
colder Canadian air from the north on Monday. Snow should
generally taper off as forcing departs to the east thru the day,
but there is some moisture in the trailing NW flow aloft that may
allow some lighter pcpn to linger into Monday night, especially as
the dendritic layer falls to the boundary layer where upslope
winds will exist. Next shortwave emerging from the north Pacific
will drop thru the Pac NW to the central Rockies Monday night and
Tuesday. Weaker ascent may brush our west/south so have added some
low pops to cover these areas during these periods. Though we
aren`t looking at significant snow accumulations, any snow that
falls will stick as temps plummet.

Main story early next week is the arctic air which will likely
drop temperatures to levels we did not see at all last winter.
This airmass has its origins up in AK/Yukon, and models are in
good agreement showing 850mb temps to the vicinity of -20C along
with surface pressures to 1040+mb. Monday is the transition day
and should see highs in the upper teens and 20s. Tuesday and
Wednesday will be quite cold with highs only in the single digits,
and lows below zero. Eastern areas will see a persistent NW wind
Tue/Wed and wind chills will be well below zero at such places as
Miles City, Baker and Ekalaka. There is model uncertainty
regarding when this cold air will be replaced by downslope
warming. The GFS is the fastest of all models to introduce lee
side troffing along our foothills by Thursday, whereas the ECMWF/
Canadian keep it colder w/ cyclonic flow aloft thru Thursday. The
GEFS mean is colder than the operational GFS, so have adjusted
temps down a bit Wednesday night and Thursday. Warming will
eventually commence by the end of the week, likely by Thursday
night and Friday. We could see wind issues along our western
foothills including Livingston once the lee side trof develops.

Will continue messaging for a combination of some snow
accumulation and high confidence of very cold temps along with
bitter wind chills Monday thru Wednesday.

Your climate tidbit of the day: The Billings airport has not
fallen below zero since January 10, 2015. The stretch of 693 days
(as of today) is the longest on record, but will likely come to an
end next week.

JKL

&&

.AVIATION...

VFR conditions will prevail tonight. Southwest winds gusting to
45kts are expected to develop in the western foothills, including
the KLVM vicinity this evening and persist through the weekend.
A disturbance will bring an increase in cloud cover and a few
showers to the area around sunrise Saturday, with local MVFR
conditions near any precipitation areas. BT/Chambers

&&

.PRELIMINARY POINT TEMP/POPS...

    Sat     Sun     Mon     Tue     Wed     Thu     Fri
-----------------------------------------------------------
BIL 026/043 028/044 021/025 005/008 905/004 903/016 013/033
    22/J    23/W    65/S    32/J    21/B    11/B    12/J
LVM 028/040 031/042 020/023 001/009 907/009 901/022 020/040
    22/W    45/W    64/S    32/J    21/B    12/J    22/W
HDN 022/043 027/046 022/027 005/009 905/003 907/017 009/027
    13/W    22/W    55/S    32/J    21/B    11/B    12/J
MLS 022/041 025/043 020/026 003/007 907/003 906/010 000/020
    03/W    12/W    45/S    32/J    11/B    11/B    12/J
4BQ 017/040 023/042 020/027 002/008 908/003 908/014 003/026
    02/W    11/E    36/S    32/J    21/B    11/B    11/B
BHK 016/038 022/040 018/025 002/006 908/002 908/008 903/017
    02/J    11/B    45/S    32/J    11/N    11/B    12/J
SHR 015/041 020/044 021/026 002/010 907/007 910/018 005/034
    02/W    22/W    36/S    32/J    21/B    11/B    11/B

&&

.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...Wind Advisory in effect until 6 PM MST Sunday FOR ZONES
      65-66.
WY...None.

&&

$$
weather.gov/billings


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