Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 280412

Area Forecast Discussion
National Weather Service Billings MT
912 PM MST Sun Nov 27 2016

Water vapor imagery shows a split upper trof over the region, with
weaker northern low over eastern MT and stronger energy in SD. The
latter will evolve into a northern plains storm which will wrap
pcpn into our east by late tomorrow. As of 04z, the western edge
of the pcpn was near KDIK. In the meantime, we are left with a
mostly dry airmass tonight with the exception of some light -shsn
over the mountains. Pac NW shortwave in fast NW flow aloft will
bring increasing snow showers over our western mountains later
tonight and tomorrow. All of this is covered well in current
forecast, but have lowered tonight`s pops a bit. Have also
adjusted sky and wind per current conditions. JKL


.SHORT TERM...valid for Mon and Tue...

Today will be the warmest day we will experience for quite some
time. Water vapor imagery is currently showing an upper low moving
out of Colorado northeast into Nebraska. Models are progging this
low to intensify and move northeast into the eastern Dakotas and
western Minnesota by Monday morning and remain fairly stationary
through Tuesday night. This low will rotate pieces of
energy/vorticity counter- clockwise westward over the western
Dakotas and the eastern half of Montana. In addition, a surface
low will develop over the same location, intensify as it moves
northeast, and remain stationary as well over the
Dakota/Minnesota border. This will allow for tight pressure
gradients across our far eastern counties resulting in very gusty
northwest winds.

These two lows will pull moisture all the way from the Gulf of
Mexico northward and wrap it around the low into the western
Dakotas and eastern Montana. Models have been consistent with this
set-up along with qpf amounts of .20-.30" across our 4 eastern
counties into the southern portions of Big Horn and Rosebud
Counties equating to about 3-6 inches of snow with possibly
isolated higher amounts. The accumulating snow will be a sharp
east/west line so further west from Treasure county westward only
snow showers or periods of light snow are expected. The exception
will be southern Big Horn County into Sheridan County and the Big
Horn Mountains where northwest flow is favorable for these
locations. However, confidence is low for accumulations for the
city of Sheridan as a northwest flow can often downslope that

Given the above scenario, we have issued a winter storm watch for
Custer, Fallon, Powder River and Carter counties starting mid
afternoon Monday continuing through Tuesday night. Even if snow
amounts fall short of criteria, winds will be an issue resulting
in blowing snow and significantly reduced visibilities. Confidence
is a bit lower further west for Rosebud and eastern Big Horn
County but an advisory may be needed for these areas. Highs
tomorrow will be in the upper 30s to lower 40s with readings
dropping below normal Tuesday with upper 20s near the Dakota
borders with lower to middle 30s elsewhere. Hooley

.LONG TERM...valid for Wed...Thu...Fri...Sat...Sun...

The extended period looks cooler and a bit unsettled. One storm
moves out of the area and the east will get a chance to dry out a
bit. For the west, more energy slides in on lowering heights as
the next bit of energy moves through the northern Rockies. The
strongest energy moves well to the south, but the northern trough
does contain a little circulation for a small closed low that
moves across central Montana. Will need to maintain low PoPs for
this system and keep things cool for Wednesday and Thursday.
Models are really struggling with this system and thus confidence
is not high on any chance of snow. Heights continue to lower and
the flow backs for Friday into next weekend. Will keep low PoPs in
as the main energy slides over northern Montana. Looks to be a bit
of a warming tend for the weekend with zonal flow ensuing, but
with heights lowering, and some fresh snow cover for the east,
would not expect a large warmup. TWH



Mountain snow showers ongoing will increase in coverage into tomorrow.
At the terminals, expecting VFR conditions with increasing and
lowering cloud decks by Monday afternoon. Some chance for MVFR
CIGS and -SHRA at LVM overnight into the morning hours. WNW winds
begin to increase by the end of the TAF period as a system
develops over the Dakotas. Walsh



    Mon     Tue     Wed     Thu     Fri     Sat     Sun
BIL 033/042 029/038 024/037 023/036 022/036 023/041 025/043
    12/R    22/O    10/U    22/S    21/B    12/O    11/B
LVM 030/039 027/035 021/037 023/036 018/037 022/040 026/042
    24/O    33/S    11/B    22/S    21/B    12/S    22/O
HDN 028/043 027/037 021/034 018/034 017/035 019/038 021/040
    12/R    43/O    11/B    12/S    21/B    12/S    11/B
MLS 029/041 026/034 021/034 014/031 015/035 017/039 020/038
    13/O    87/S    32/S    11/B    11/B    11/B    11/B
4BQ 028/042 024/033 018/032 011/031 012/031 014/038 019/039
    13/R    77/S    61/B    11/B    11/B    11/B    11/B
BHK 026/037 022/029 019/028 011/027 011/029 011/035 017/037
    24/O    87/S    63/S    21/B    11/B    11/B    11/B
SHR 028/039 022/031 017/034 015/033 013/029 012/038 016/041
    12/O    44/S    11/U    12/S    21/B    12/S    11/B


MT...Winter Storm Watch in effect from Monday afternoon through
      late Tuesday night FOR ZONES 32-33-36-37.


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