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Area forecast discussion...updated 
National Weather Service Billings Montana
900 PM MST Tuesday Nov 24 2015

current radar indicative of whats occurring in the lower and middle
levels. Downsloping southwest flow in middle levels is suppressing
any precipitation development in the foothills while overrunning
and vorticity producing areas of snow across our central and
northern zones. I clipped a bit of the snow amounts from the
foothills and mountains overnight. VAD wind profile shows upslope
flow only about 7k mean sea level...and until that deepens it will be hard to
get precipitation going in the foothills. However...VAD trends do
show it slowly deepening and middle level cold air is pushing
into Lewistown vicinity at this time. So I still expect things to
get socked in across the foothills later tonight.

Newest model proggs show precipitation diminishing a little
sooner across our nothern zones Wednesday than forecasts
indicate. So reduced probability of precipitation north of Billings and I-94 for tomorrow
afternoon. Bt


Short term...valid for Wednesday and Thursday...

Going forecast has remained on track with a few subtle
differences. The surface cold front has moved through Billings as
of 2pm local time.

Temperatures should start to fall from west to east at Sundown
with the arrival of the colder Canadian air.

Looking at satellite and radar imagery...light snow should start
at points west of Billings within the next few hours and fill in
around Billings by later this evening.

At middle levels...a cut off low is circulating over the Great Basin
underneath split upper level flow. The left exit region of the upper
level jet streak will be over south central Montana during the
overnight hours tonite. This should translate to the heaviest
snowfall rates from Billings westward. concern is
that this dynamical forcing may not be enough to push snowfall
amounts much past advisory levels in places like Billings and
points eastward.

Taking a look at the cips analogs...this was a particular tough
case to find a quality analog for. Scores were not very high...but
interestingly enough...the historical coop snowfall reports
painted a bleak picture for anything more than a couple of inches
over the plains.

All that being said...believe the going forecast for snowfall
amounts are right on track. One thing is for certain...the higher
elevations and foothill locations...including Red Lodge...should
see significant snow totals when all is said and done Wednesday

With respect to the temperatures...Wednesday and Thursday will be pretty
cold...and some locations may dip into the negative digits if the
skies clear out tomorrow night.

The previous issued highlights are in great shape...and we have
updated the wording to adjust for timing and impacts. Decided
against extending the highlights into the far eastern zones for

This weather event will have obvious impacts to Holiday travel...and
hunters will need to be prepared. Singer

Long term...valid for Friday...Sat...sun...Mon...Tue...

Latest GFS and Euro runs continue to disagree on how to handle
the closed low over the Great Basin and begin to diverge quite a
bit by the upcoming weekend. While the upper flow pattern appears
largely similar through Saturday morning... the GFS draws some
moisture north from the Central Plains early Saturday and to a
lesser extent in the Euro later in the day as the Great Basin low
elongates along a SW to NE axis and forms separate lobes of closed
heights. The formation of this NE lobe in the Euro appears to
close the window for precipitation quickly on Saturday as this
feature begins to dominate the broader closed circulation pattern
by Sunday night... but the GFS transitions the closed low from the
Great Basin in a more linear fashion to the NE and passing to our
southeast sometime after Monday afternoon... resulting in higher model
quantitative precipitation forecast... and snow... from Sunday to Monday night in our eastern
zones. Needless to say... inherited probability of precipitation were quite different from
the final product but made best effort to accommodate these and
new trends noted above over the course of this time period. The
pattern may finally settle for Tuesday Onward but prior upper-
level flow uncertainty leaves much doubt by this time period.

For temperatures... will remain cold with upper teens to lower
20s common across most areas until Monday when maxt values may
finally rise above freezing at lower elevations. Whether or not
this occurs is highly dependent on how the flow pattern discussed
above plays out. Mrowell



Snow is in the process of overspreading southern Montana from west
to east. Expect this snow to bring MVFR/IFR conditions with
localized LIFR conditions. LIFR conditions especially anticipated
near klvm. Conditions should imrpove after 00z Thursday over southern
Montana. Around kshr...snow should develop after 09z Wednesday and continue
through Wednesday night with MVFR/IFR conditions.

Mountain obscurations will increase overnight and persist into
Wednesday. Rms/bt


Preliminary point temp/pops...

Wednesday Thursday Friday Sat sun Monday Tuesday
bil 020/023 008/022 006/022 013/025 018/031 016/034 021/034
+8/S 62/S 10/b 11/b 21/b 21/b 11/b
lvm 020/023 008/022 007/021 006/027 013/031 013/031 014/032
+9/S 62/S 10/b 12/j 22/j 11/b 11/u
hdn 021/026 008/024 003/023 014/025 014/028 013/032 018/032
88/S 53/S 11/b 21/b 31/b 32/j 11/b
mls 022/027 009/023 006/025 018/029 017/029 020/030 021/032
77/S 31/b 00/b 12/j 31/b 32/j 21/b
4bq 023/027 012/021 004/023 016/025 012/026 020/028 018/031
46/S 74/S 10/b 32/j 31/b 32/j 21/b
bhk 022/026 009/022 007/026 017/028 019/028 021/029 021/030
46/S 21/b 00/u 02/j 31/b 32/j 20/b
shr 020/023 008/019 000/022 012/024 013/027 019/030 020/032
68/S 86/S 11/east 22/j 22/j 32/j 11/b


Byz watches/warnings/advisories...
Montana...Winter Storm Warning in effect until 5 am MST Thursday for
zones 28-41-56-63-65>68.
Winter Weather Advisory in effect until 5 am MST Thursday for
zones 29>31-34-35-39-40-42-64.
Winter Weather Advisory in effect until 11 am MST Thursday
for zones 38-57-58.
Wyoming...Winter Weather Advisory in effect until 11 am MST Thursday
for zones 98-99.



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