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Area forecast discussion 
National Weather Service Billings Montana
502 PM MST sun Dec 28 2014

Update...
band of heavy snow has set up along the foothills from Red Lodge
to Nye this evening. VAD wind profile showing deep upslope flow
has set up over south central Montana and this is expected to
continue through the night. Will go ahead and upgrade the Winter
Weather Advisory for Red Lodge and Nye to a Winter Storm Warning.
6 to 10 inches of new snow will be possible with locally higher
amounts. Snow there will taper Monday morning. Rest of the
forecast is on track and have made no other changes. Richmond

&&

Short term...valid for Monday and Tuesday...

An active period of weather on going as snow and cold will be the
stories through the short term. Kblx radar was lit up with returns
as snow has been falling for much of the morning. A good deal of
this snow has been pre-frontal as qg forcing with a jet maximum served
to provide lift for snow ahead of the Arctic squeezing out its
share. The Arctic boundary was progressively moving southward and
went through Billings just before 20z. This will provide a very
cold period of weather to start the week.

As the Arctic sinks south through the area...the best dendrite
growth zone slides in early this evening. Upper forcing will be
weaker with the jet dynamics we saw earlier today sliding
southeast out of the area. Strong upslope flow will kick in though
and this should be enough to produce accumulating snow. The time
of strongest upslope forcing looks to be this evening. The airmass
deepens up overnight and takes the good dendrite growth zone out
of play...so accumulation should be limited overnight and early
Monday. Snow will continue into a good deal of the day Monday but
the main accumulation period will be this afternoon and this
evening.

Will keep advisories in place. Will have to keep an eye on
favored upslope locations of the foothills...from McLeod to Red
Lodge. A band of moderate snow just south of Columbus was sinking
toward this area at the moment. If this band gets hung up along
the foothills...may need a warning. Otherwise...advisories look in
good shape. There may be a few 6 inch totals in spots due to some
aggressive snow bands early today...but these amounts should not
be widespread. Still expect mainly 3-5 inches most locations.

Light snow lingers for western and central zones Monday morning.
The Arctic airmass should be adequately deep to limit additional
accumulation to an inch or so. Temperatures will be very chilly
Monday through Tuesday with highs around zero both days. Lows
Monday night will be tricky as cloud cover could keep readings up.
Any break in the clouds could allow temperatures to plummet to
near 20 below in low lying areas. Trimmed back highs Tuesday with
such a cold start Monday night. Twh



Long term...valid for Wednesday...Thu...Fri...Sat...sun...

Minor changes again to the extended forecast period...as overall
forecast appears in good shape. Wednesday and Thursday still
appear to be warming up...with downslope flow developing as a surface
trough develops between two high pressure systems.

Another Arctic system is prognosticated into the region Friday...which
looks quite similar to the system crossing the region now. The
Arctic air will interact with a strong influx of Pacific moisture
that will overrun the the Arctic boundary. This should bring snow
across the region for much of Friday. Snow appear to persist
across the region through the remainder of the extended period as
Arctic air continued to undercut the warm Pacific air...leading to
the extended period of snow across the region. Temperatures...as one
would expect...will plummet behind the Arctic cold front...with
highs once again in the teens to single digits for the weekend.
Aag
&&

Aviation...

Widespread of MVFR to IFR can be expected for all routes in
reduced visible in snow...and low ceilings. Occasional LIFR and vlifr
conditions are possible through the evening...becoming more
persistent and widespread later this evening...as snow increases.
Low visible and ceilings should begin to improve from north to south on
Monday morning. Aag

&&

Preliminary point temp/pops...

Monday Tuesday Wednesday Thursday Friday Sat sun
-----------------------------------------------------------
bil 902/001 914/902 913/025 013/031 014/026 008/009 905/012
+7/S 30/I 00/north 01/north 26/j 44/j 33/j
lvm 902/003 921/902 916/026 009/033 013/031 014/014 901/016
+8/S 30/I 10/north 00/b 26/j 54/j 33/j
hdn 902/002 915/000 916/022 007/030 009/026 006/011 904/015
+6/S 21/b 00/u 01/b 15/j 44/j 33/j
mls 907/001 915/000 909/024 013/029 014/023 005/007 907/008
72/j 11/b 00/u 01/b 25/j 33/j 22/j
4bq 000/004 915/001 913/023 011/030 012/027 008/011 901/011
+3/S 11/b 00/u 01/b 13/j 44/j 32/j
bhk 907/902 916/902 911/022 011/029 012/022 003/006 910/008
61/I 11/I 00/u 11/b 24/j 33/j 22/j
shr 901/004 918/903 914/027 007/032 010/031 011/018 001/016
++/S 21/I 00/u 00/b 13/j 44/j 33/j

&&

Byz watches/warnings/advisories...
Montana...Winter Weather Advisory in effect until noon MST Monday for
zones 28>32-34>36-38>42-57-58-63>65.
Winter Storm Warning in effect until noon MST Monday for
zones 56-66.
Wyoming...Winter Weather Advisory in effect until noon MST Monday for
zones 98-99.

&&

$$
Weather.Gov/Billings

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