Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 212342

Area Forecast Discussion...Updated
National Weather Service Billings MT
442 PM MST Tue Feb 21 2017

.UPDATE...With high CAPES over NE zones and lightning in the area...did
quick update to add thunder into early evening.

.SHORT TERM...valid for Wed and Thu...

Busy and challenging forecast for the short term. Strong 120kt
jet was crossing northern Wyoming with 700mb winds upwards of
55kts crossing far southern Montana. Strong downslope flow has
induced deep mixing and temperatures have responded in kind with
readings rising into the 60s this afternoon. Mixed winds have been
mainly in the 40-50mph range for most locations. Winds have been
very close to advisory criteria in Livingston but have stayed a
bit below warning criteria for Big Timber and areas of southern
Montana into Sheridan county Wyoming. Shortwave was moving through
the area as of this writing, and may induce a bit of subsidence
that could peak the winds over southern locations yet this
afternoon and early this evening. Winds looks to hang on a bit
longer over the west as the gradient orientates itself well for
the Big Timber to Harlowton corridor and 700mb winds hover around
50kts through the evening.

Attention then turns to cold frontal boundary pushing into the
area tonight and the potential for snow when combining this with
the approaching western trough. There have been differences on the
extent and timing of the 850mb frontal boundary dropping south
from northeast Montana. The NAM and ECMWF were more aggressive in
sending the boundary into south central Montana by late Wednesday
morning into early afternoon. The GFS holds off until late
Wednesday afternoon, or even early evening. Since the GFS was a
bit of an outlier, went with a EC/NAM combo. Am thus expecting
some precipitation to develop along the boundary over south
central Montana into southeast Montana by late Wednesday morning
into early afternoon. Would be a rain and snow mixture as the
airmass doesn`t get adequately cold until Wednesday evening. At
any rate, this boundary brings an end to the very mild weather of
the last few days.

The western upper trough will swing into the northern Rockies
Wednesday night and Thursday, with a low cutting off over southern
Wyoming early Thursday. The models have struggled greatly on
resolving this pattern, but have just lately pushed the system a
little farther north and deepened the low. This would provide
strong potential for accumulating snow over southern locations and
into northern Wyoming through Thursday. Have raised PoPs for
areas south of Billings with likely snow over southern Big Horn
county and Sheridan county Wyoming late Wednesday night through
the day Thursday. Added accumulating snow with a few inches
possible by the time the snow tapers off Thursday night. Will have
to watch these areas closely for potential highlights. TWH
.LONG TERM...valid for Fri...Sat...Sun...Mon...Tue...

Not many changes in the long term. Models continue to show a
general northwest flow pattern setting up Friday and continuing
through the weekend. While the general pattern in the models is
similar the timing and placement of the precip is still very
uncertain. This lower confidence has lead to only minor tweaks
based on a blend of the solutions. With moisture lingering in the
area have continued the chance PoPs. Temperatures will continue
to be slightly below normal through the period. With the cooler
temperatures still expecting any precip that falls to be snowfall.

Early next week a trough will move into the Norther Rockies giving
a chance for some better organized precip. Reimer


Thunderstorms over KMLS will move out early this evening. Small
hail is possible. Expect gusty winds to continue through this
afternoon from KBIL and KSHR west, especially around KLVM. Winds
will decrease tonight. Expect VFR conditions to prevail, though
late in the morning Wednesday some MVFR conditions could begin
around KMLS as some snow moves into the area. Arthur/Reimer &&


    Wed     Thu     Fri     Sat     Sun     Mon     Tue
BIL 036/048 026/036 021/033 017/032 016/036 019/033 014/033
    14/W    54/J    32/S    12/S    11/B    12/S    22/S
LVM 031/044 018/030 013/027 008/027 011/032 016/032 014/033
    23/W    44/J    33/S    32/S    21/B    22/S    22/S
HDN 033/047 024/036 020/033 014/031 013/035 017/035 014/033
    14/W    44/J    33/S    12/S    11/B    11/B    22/S
MLS 034/044 026/037 021/034 019/032 017/034 019/034 017/033
    35/W    33/J    22/S    12/S    11/B    11/E    22/S
4BQ 034/047 025/037 020/035 017/032 015/035 017/038 017/036
    14/W    45/J    42/S    12/S    11/B    01/B    22/S
BHK 034/041 024/034 017/030 017/028 013/030 015/032 014/030
    35/W    33/J    21/E    12/S    11/B    01/E    22/S
SHR 031/046 023/034 017/028 010/027 008/032 012/034 014/031
    13/W    67/J    64/S    32/S    11/B    01/B    22/S


MT...High Wind Warning in effect until midnight MST tonight FOR
      ZONES 28-41-63.
     High Wind Warning in effect until 9 PM MST this evening FOR
      ZONES 36-38-58.
     Wind Advisory in effect until midnight MST tonight FOR ZONES
WY...High Wind Warning in effect until 9 PM MST this evening FOR
      ZONE 99.


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