Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 181039

Area Forecast Discussion
National Weather Service Billings MT
339 AM MST Thu Jan 18 2018

.SHORT TERM...valid for Tdy and Fri...

Issued a winter storm warning for the southern and western slopes
of the Beartooth/Absaroka mountains for tonight through tomorrow
evening. Wind advisory for the Livingston and Beartooth foothills
continues into this evening.

A dynamic storm system will move into the area over the next 18
hours with a good deal of wind. Gusts to near 70 mph have already
been recorded in and around Livingston and guidance and forecast
winds at 700mb are aligning for additional gusts in this range
later today. Expect gusty winds to occur all along the western
foothills today and spreading into the plains this afternoon as
temperatures in the 45 to 55 degree range allows better mixing of
stronger winds aloft to the surface. Those stronger winds are
courtesy of a SW-NE oriented jet stream that will be sitting over
the area this afternoon into tonight.

Cross sections still showing indications of mountain wave
activity late this afternoon through this evening ahead of the
cold front. Models currently insulating the surface from these
potential mountain wave gusts due to very cold sub-boundary layer
temperatures which look to be anomalously cold in many cases
(especially the NAM). Expect warmer sub boundary layer
temperatures and a weaker surface inversion thus have increased
wind speeds in these normally sheltered foothills locations, but
have kept well below wind warning levels. That said subsequent
shifts will need to keep an eye on this as 60+kt winds exist along
the crest of the Beartooth and Bighorn mountains late this
afternoon into this evening. Bottom line is it will be windier
than normal today in the foothills and isolated strong gusts are
not out of the question.

Cold front arrives after midnight from the northwest. Its going to
take a while for precipitation to get going over the lower
elevations due to the influence of the strong downslope W-SW
winds. As the cold front moves through gap and mountain wave wind
potential will decrease fairly quickly. Once that occurs the
atmosphere will begin to moisten over the lower elevations as
winds turn more northwesterly and weaken. Strong dynamics and good
moisture advection look to overcome unfavorable wind conditions
for at least a period Friday morning when a few inches of snow
could accumulate in the western foothills. Elsewhere a mix of rain
and snow in the morning will become isolated to scattered snow
showers by mid day Friday, sliding south Friday evening.
Temperatures will drop to around freezing Friday morning then warm
into the mid-upper 30s in the afternoon. This should minimize any
impacts from winter precipitation for most locations, though
rain/melted snow on icy/snow-covered rural roads could present
some travel issues.

Southwest to west winds advecting strong moisture feed into the
Beartooth/Absaroka mountains will bring periods of heavy snow
tonight into Friday, along with winds gusting to 65 mph at times.
These conditions will bring dangerous back country conditions to
the high country and increase avalanche danger, thus the Winter
Storm Warning for that area. The north and east facing slopes
(above Red Lodge and Nye) will see much less snow but still
strong winds. Red Lodge ski area can expect winds to become strong
at times this afternoon, with the strongest winds this evening.
Snow showers early Friday could bring a 2 to 4 inches of new snow
to these areas. Chambers

.LONG TERM...valid for Sat...Sun...Mon...Tue...Wed...

Still looks like a generally dry extended outside of the
mountains. Saturday will see the trough from Friday exit the
area, with some PoPs lingering in the mountains and SE MT. As some
ridging works into the area Sunday and Monday the surface
pressure gradient will tighten up. The favored areas for gap winds
will once again see increasing winds. Early next week the flow
becomes very progressive with several waves of energy moving
through. There is still differences in when the individual
impulses of energy moves across the area, but the main focus for
precip will be in the mountains with only slight chances else
where. Temperatures still look to be around seasonal normals.



VFR conditions will continue through the day today. Winds around
KLVM will continue to be 50 to 60 kts through 03Z. Expect some
MVFR conditions to develop after 03Z around KVLM as rain moves
into the area. Reimer



    Tdy Fri     Sat     Sun     Mon     Tue     Wed
BIL 049 032/038 023/034 015/030 015/035 017/027 013/029
    0/N 36/J    21/B    11/B    12/S    22/S    12/S
LVM 052 034/037 018/032 013/033 017/037 019/034 019/033
    0/N 68/J    32/S    21/N    22/S    32/S    22/S
HDN 044 028/035 020/033 012/029 010/031 014/026 007/030
    0/E 26/J    31/B    11/B    12/S    22/S    12/S
MLS 039 027/034 020/031 012/026 011/030 014/023 005/022
    0/B 23/J    11/B    11/B    12/S    22/S    11/B
4BQ 046 030/039 025/035 016/031 013/033 016/027 008/027
    0/B 12/J    22/S    21/B    12/S    22/S    11/B
BHK 046 025/039 021/035 013/030 010/032 013/025 005/024
    0/B 11/E    11/E    11/B    12/S    22/S    11/B
SHR 050 030/037 023/031 014/029 011/033 014/028 010/031
    0/B 13/J    34/S    21/B    11/B    22/S    11/B


MT...Wind Advisory in effect until 6 AM MST Friday FOR ZONES
     Winter Storm Warning in effect from 6 PM this evening to
      midnight MST Friday night FOR ZONE 67.


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