Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 292151

Area Forecast Discussion
National Weather Service Billings MT
251 PM MST Tue Nov 29 2016

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

Strong slow moving storm system centered over E ND/W MN this
afternoon continues to funnel strong north-northwesterly flow
into eastern Montana, along with bands of snow. Weak narrow snow
bands are evident on radar from near Billings west into the higher
terrain. Stronger and more persistent snow bands continue over
southeast Montana, generally east of a Miles City to Broadus line.
Once the sun sets the western snow bands should dissipate as
instability diminishes in the lower atmosphere, however eastern
areas will continue to see periods of light snow through the night
especially over Carter and Fallon counties. Additional Snow
accumulations over southeast Montana will be generally less than 2
inches and some areas may see just a dusting. Gusty winds will
show the same trend as snowfall with western and central zones
seeing a fairly quick diminishing of winds this evening, while
eastern zones remain gusty through most of the night. With 3 to 8
inches of snow on the ground over parts of SE MT, considerable
blowing and drifting is expected to continue making travel
difficult especially in rural areas. Will continue going winter
highlites as is for now. The Winter Weather Advisory for Custer
and Powder River county goes until midnight tonight, while the
Winter Storm Warning for Fallon and Carter runs through early
Wednesday morning.

A nice day in store for Wednesday with snow/wind tapering off over
eastern zones as shortwave ridging builds into the area. A fast
moving system dropping down the spine of the rockies will begin to
increase winds over the western foothills in the afternoon, but at
this point looks like speeds will stay under advisory levels for
Livingston. Snow shower activity will pick up Wednesday evening
over the western mountains and foothills, spilling into the plains
overnight into the morning on Thursday. Expect scattered mainly
snow showers Thursday across the area with the best chance of some
light snow accumulation in the north facing mountains and
foothills. This type of system sometimes over achieves on
snowfall for our western foothills and valleys (Paradise, Shields)
so will keep an eye on it, but at this time an inch or less of
snow will be the rule, with locally heavier accumulations possible
in the aforementioned areas. Scattered snow showers will taper off
overnight into Friday morning. With fresh snow on the ground and a
few breaks in the cloud cover will see some near single digit low
temperatures Friday morning over SE MT. Chambers
.LONG TERM...valid for Fri...Sat...Sun...Mon...Tue...

GEFS ensembles showed some uncertainty with the pattern beginning on
Saturday, while the ECMWF ensembles showed uncertainty with the
pattern for the weekend, then less uncertainty for Monday and
Tuesday. Beginning on Sun., the GEFS plumes showed decreasing
temperatures, but there were decent spreads in many of the GEFS
fields. So, an arctic surge continues to be a possibility late in
the period, but will need to continue to watch model trends given
the above.

Otherwise, the extended continued to look rather unsettled with
possible windy periods in the gap flow areas. The northern branch
of a split trough will move through the area on Friday, followed
by an active NW flow into Sat. night. Kept Fri. mainly dry due to
decreasing moisture from N to S during the day. Pacific moisture
surges into the area from the W Fri. night through Sat. night
supporting chances for showers overspreading the area from W to E.
The pattern looked favorable for possible strong gap flow during
this period, so kept higher wind speeds in these areas. Sat. will
be the warmer of the two days with highs reaching the 40s.

A brief flattening of the flow on Sunday gives way to another
trough moving in Sun. night. Had PoPs across the region with highs
in the 40s on Sunday. The models then had colder air working into
the area from the N Sun. night and Monday with differing strengths
of the cold air. As stated above, there was uncertainty with
moisture as well, so had blended PoPs over the area. Used WPC
temperatures for Monday which were in the 30s. The trough and
accompanying arctic air deepen through Tuesday. Followed WPC for
highs which were in the teens and 20s, and continued the blended
PoPs. Arthur


Snow from Rosebud County E will bring MVFR/IFR conditions to
this area, including KMLS, before decreasing overnight. NW winds
gusting to 35 kt will create poor visibilities in the snow, before
gradually decreasing overnight. Otherwise, scattered snow showers
with MVFR conditions will affect the area through the evening.
Gusty winds in KBIL and KSHR will decrease this evening. VFR will
return to the area overnight in most areas, and will prevail
across the area on Wednesday. Expect localized to areas of
mountain obscuration through Wednesday. Arthur



    Wed     Thu     Fri     Sat     Sun     Mon     Tue
BIL 023/038 026/038 023/037 027/044 029/042 027/033 016/019
    10/U    22/S    21/B    12/W    22/O    23/S    22/S
LVM 022/036 027/036 021/035 028/043 030/042 027/030 010/020
    11/N    33/S    21/B    32/W    33/O    33/S    22/S
HDN 021/037 023/038 020/036 023/043 026/041 023/034 016/020
    10/U    12/S    21/B    12/W    22/O    23/S    22/S
MLS 022/034 014/034 018/034 021/044 023/040 021/032 014/017
    31/B    11/B    21/B    12/W    21/B    23/S    22/S
4BQ 019/035 013/036 016/032 018/042 021/039 019/033 014/018
    31/B    12/J    21/B    02/W    21/B    12/S    22/S
BHK 017/027 008/028 012/029 015/039 018/036 016/029 011/013
    53/J    11/B    21/B    13/J    21/B    13/S    22/S
SHR 017/034 014/034 014/031 015/040 021/038 019/032 013/020
    10/U    12/S    21/B    11/B    11/B    12/S    22/S


MT...Winter Weather Advisory in effect until midnight MST tonight
      FOR ZONES 32-36.
     Winter Storm Warning in effect until 6 AM MST Wednesday FOR
      ZONES 33-37.


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