Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 240424

Area Forecast Discussion...Updated
National Weather Service Billings MT
924 PM MST Mon Jan 23 2017

Issued a quick update due to report of freezing drizzle along US12
between Roundup and Ingomar. Where clearing is trying to occur
aloft some saturated low level air could produce short periods of
freezing drizzle. borsum

Webcams show snow accumulating over portions of northern Wyoming
and along the foothills but elsewhere snow is just dusting the
ground. Storm system intensifying over southern Wyoming and radar
shows a second band of snow moving into the southern Beartooth and
Absaroka mountains that will support better accumulations
overnight. Current snow over the Billings area appears to be
decreasing as this next band strengthens with this next band
expected to remain south of the Yellowstone Valley. Current
forecast handles these details well and no updates planned. borsum


.SHORT TERM...valid for Tue and Wed...

Satellite imagery shows a broad low over the western CONUS with a
shortwave producing cold tops and an area of snowfall from
northern UT into southern ID and western WY. 150kt H3 jet is well
to our south and extends from southern CA to CO. Forcing with the
energy moving into the central Rockies will remain to our south
tonight into Tuesday.

We will see a period of mostly upslope-driven snowfall tonight
into Tuesday, with weak ascent provided over our far south from
passage of upper level low as it moves from WY into NE/SD. Recent
models have trended south with the low and lighter with QPF in our
cwa and today`s forecast reflects this trend. That being said,
combination of deepening upslope flow and moisture extending into
the dendritic layer will produce at least some snowfall. Greatest
amounts will of course be over our southern upslope areas, with
QPF of 0.05-0.15 inches likely to produce a general 1 to 4 inch
snowfall, perhaps a bit more over the north slopes of the
Beartooths and Bighorns. Further north, amounts will be less than
an inch as forcing will be weak and moisture itself fairly
shallow, extending to perhaps 700mb. Billings should pick up no
more than an inch. Have adjusted snow amounts down accordingly,
and will make no changes to the winter wx advisories in effect for
our southern foothills including locations such as Red Lodge,
Sheridan and Story. For far southeast MT including Broadus and
Alzada, weak ascent will clip this area and should see an inch or
two, but with baroclinicity staying to the south do not see a need
for a highlight.

Expect at least a dusting of new snow on roads across most of our
cwa for the Tuesday morning commute, including Billings.

The remainder of the short term period is fairly quiet, but should
see areas of light snow across our east late Tuesday into
Wednesday per weak shortwave in NW flow aloft. Given a dendritic
layer near the surface, it will not be difficult to produce some
light snow.

Temps will remain below normal the next couple days, with highs
mostly in the upper teens and 20s with lows in the single digits
to mid teens.


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

Mainly dry along with breezy to windy conditions can be expected
through the extended period. Models are in good agreement so
confidence is fairy high in the forecast. High pressure ridging
begins to build across the northern Rockies Thursday. Although
heights begin to rise, there will also be a Klondike Chinook
developing Thursday and Friday. This will bring a west wind to the
area, especially from Billings westward. Although heights will be
rising, this west wind may slow the warmup as opposed to a more
traditional southwest wind.

By Friday night into Saturday, models bring a disturbance south
out of Canada across mainly eastern Montana bringing the
possibility of a light snow shower. Ridging increases and lee-
side troughing develops Saturday night through Sunday. This will
result in gap winds developing across the Livingston to Nye areas
along with much windier conditions. Another disturbance may drop
southeast across the forecast area Sunday night into Monday
bringing a chance for snow showers. Temperatures will remain below
normal Thursday and Friday but begin to warm to around normal
next weekend and possibly above normal Sunday into Monday with
temperatures in the upper 30s to lower 40s possible. Hooley



Areas of light snow will affect the region overnight, continuing
into Tuesday. VFR to as low as IFR cigs and vsbys are possible
with mountain obscurations likely. The majority of accumulating
snow will be south of a KLVM-KBIL-Broadus-Ekalaka line. STP



    Tue     Wed     Thu     Fri     Sat     Sun     Mon
BIL 016/024 010/027 013/027 016/032 020/036 024/038 023/037
    75/S    11/E    10/B    00/N    00/N    00/N    01/N
LVM 012/025 009/027 011/026 011/031 018/035 021/042 031/040
    64/S    22/J    10/N    00/N    00/N    00/N    11/N
HDN 011/023 002/025 007/025 009/030 011/033 015/036 016/035
    86/S    22/J    10/B    00/B    00/U    00/B    01/B
MLS 012/020 006/021 006/022 009/028 014/032 017/034 018/032
    43/S    22/J    20/B    00/U    01/B    01/B    02/J
4BQ 014/022 005/023 007/024 011/029 015/033 018/037 017/034
    88/S    22/J    20/B    00/N    00/U    01/B    01/N
BHK 012/018 007/019 004/020 011/026 014/030 015/034 018/032
    43/S    22/J    21/B    00/N    01/B    21/B    02/J
SHR 012/021 003/024 005/026 008/031 014/035 017/040 017/036
    99/S    21/B    10/B    00/B    00/U    00/B    11/B


MT...Winter Weather Advisory in effect until 2 PM MST Tuesday FOR
      ZONES 38-56-66.
WY...Winter Weather Advisory in effect until 2 PM MST Tuesday FOR
      ZONES 98-99.


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