Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 200315

Area Forecast Discussion
National Weather Service Billings MT
815 PM MST Fri Jan 19 2018

Northern portion of split trof is moving slowly thru central MT
this evening. As mid level flow has veered to the NW we are
advecting drier air now, and as a result precipitation has pretty
much ended across our western lower elevations. Have cancelled
the winter weather advisories. SW flow aloft continues to bring
some snow to the Beartooth Absarokas, though it has become
lighter. Will let the Warning for our southwest mountains continue
for now, with another couple inches expected through the night.
Fisher Creek snotel has received over an inch of SWE since
yesterday, and Mystic Lake reported 12 inches of snowfall.

Due to today`s precipitation, ground conditions are wet and
current dew point depressions are quite low. This suggests fog.
However, winds will remain westerly as we dry advect, and we will
keep some mid and high cloud for much of the night, so will hold
off on any mention of fog for now. Have adjusted evening pops per
current conditions (highest east of Billings), and extended slight
chances to our northeast border as rain is being reported at
Baker. Otherwise we will see precip taper and shift slowly to the
S/SE, as temps fall to the 20s tonight.



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

Deep and unstable trough was working through the Great Basin. Rich
moisture was on the front side of this trough and was pushing
right into the forecast area. The trough was in the process of
splitting, but enough moisture and instability around for areas of
precipitation to occur today, into this evening. Livingston has
had periods of heavy snow showers this afternoon, with roads
becoming snowpacked. Models weaken the snow showers by early
evening. The main focus for snow through the evening is the
mountains and the foothills, spreading out into southern locations
of south central Montana. Have added the other western foothills
into the existing Winter Weather Advisory. Raised PoPs and
included some light accumulations in southern Big Horn and
southern Rosebud counties through this evening. Will have to watch
this area closely, as impressive instability could produce a
little more snow than models have expected (already seen that
today along the foothills). Will keep the Winter Storm Warning
going for the mountains, Snotels showing 4-8 inches of snowfall
accumulated with an additional 3 to 5 inches late this afternoon
into this evening.

Snow showers were approaching Billings and expect these to get
into town late this afternoon and continue into early evening.
Models keep the strongest returns south of town, so not expecting
much in the way of accumulation, but did raise PoPs and snow
amounts early this evening. Wet roads tonight will become slick,
if they do not dry out, as temperatures fall into the 20s. Will
message this story through our webpage. Otherwise, snow showers
will taper off from northwest to southeast as the trough slides
across the forecast area. This weekend will be drier as the
northern part of the splitting trough slides through. The southern
stream will develop into a strong winter storm that will impact
the central and southern Rockies, along with the central plains
this weekend into early next week. TWH

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

A sharp ridge on Sunday will break down with energy streaming
across southern Canada. This process will cause an increase in gap
winds for Livingston and Nye. Bumped winds a little more for
Sunday and will have to watch this time frame for potential gusts
over 50 mph.

Northwest flow for Monday and Tuesday will have weak energy
streaming through, but little in the way of moisture to work with.
So the forecast will be generally dry with seasonal temperatures.
Another ridge moves in for Wednesday and shifts east Wednesday
night. A deepening trough will follow the ridge for Thursday
through Friday. This trough is progged to cut off a low over
Wyoming Thursday night. This could generate a period of
accumulating snowfall Thursday night through Friday night, and
will monitor this closely as the period approaches. TWH



Areas of rain and snow will continue to shift east and south
overnight, with most areas along and west of a Roundup-Billings-
Red Lodge line clearing, with exception of mountains. Mainly VFR
conditions will prevail for the TAF sites, but localized MVFR
conditions are possible in the rain and snow activity. The
mountains will be obscured through tonight due to snow. AAG



    Sat     Sun     Mon     Tue     Wed     Thu     Fri
BIL 025/036 018/034 018/036 019/033 016/035 021/033 016/029
    20/B    11/U    02/S    11/N    11/B    24/S    53/S
LVM 021/034 014/033 023/034 019/035 019/039 025/036 015/030
    30/N    21/N    13/S    21/N    13/S    35/S    53/S
HDN 024/035 014/032 011/035 014/032 011/033 015/032 014/028
    61/B    11/U    02/S    11/B    11/B    23/S    53/S
MLS 023/032 014/029 011/032 016/029 009/029 013/028 012/022
    20/B    00/U    01/B    11/B    11/B    12/S    44/S
4BQ 024/036 017/033 013/035 018/033 013/033 017/034 016/028
    31/E    11/B    01/B    11/B    11/B    12/S    45/S
BHK 023/036 014/031 011/033 017/032 010/033 015/031 012/024
    20/B    00/B    01/B    11/U    11/B    12/S    45/S
SHR 024/034 016/032 010/033 014/031 011/035 016/035 014/029
    54/S    31/B    02/S    21/B    11/B    13/S    43/S


MT...Winter Storm Warning in effect until midnight MST tonight FOR
      ZONE 67.


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