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Area forecast discussion 
National Weather Service Billings Montana
909 PM MDT Wednesday Oct 1 2014

Update...
no update to the forecast this evening. Instability showers and
gusty northwest winds have tapered off with sunset this evening
as expected.

Church

&&

Short term...valid for Thursday and Friday...

Cold pool aloft has yielded some mostly light instability driven
showers in northwest flow aloft this afternoon. This activity will
diminish quickly around sunset as we lose daytime heating and as
weak ridging spreads in from the west. Downslope gradients will
tighten somewhat tonight in response to approaching clipper. Thus
expect some SW wind along the foothills and temperatures not as cool as
they would be otherwise.

Main forecast issues in the short term involve the shortwave and
cold front emerging from northwest Canada. Maximum temperatures will be achieved
early tomorrow as cold advection commences in the morning...with a
front expected to reach Sheridan by around 18z. Have sided with
the GFS/European model (ecmwf) regarding frontal timing. Strong cold advection/
pressure rises will result in a few hours of gusty north-northwest winds
tomorrow...with surface temperatures in the upper 30s and 40s in the Post
frontal regime as 850mb temperatures fall to the lower single digits. We
should see a brief period of shower activity per the qg forcing
and middle level frontogenesis...along with the development of low
level upslope flow for our south. Temperatures should turn cold enough to
mix with wet snow along our foothills and up at Judith Gap. Wet
bulb zero heights will be quite low so would anticipate a mix with
snow or snow pellets within any heavier showers across the lower
elevations...and there is a little potential here as models have
been consistently showing some middle level cape intersecting the
dendritic layer. Also could see some northwest flow banding east of the
snowy mountains. Although it will be short-lived...tomorrow
should see some interesting Fall-like weather with this clipper.

Subsidence/drying will end any precipitation quickly early tomorrow
evening. Looks like another freeze for much of the area Thursday
night as surface ridge builds in...with core of surface ridge in our west
and central parts...suggesting the best potential for radiational
cooling in this area and persistent northwest winds in our east. Have
dropped expected lows a bit more...consistent with guidance
trends. Record low of 23 degrees at Livingston will be challenged.

Warmer temperatures coming Friday as ridge begins to build back in from
the west...but the onset of downslope flow has trended a bit
slower. Should see highs near 50f near the Dakotas border and the
low to middle 60s along our western foothills. Lee side trough Friday
night will result in a warmer and breezy night especially along
our foothills. No chance of precipitation from late Thursday night through
Friday night.

Jkl

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

Very little in the way of changes for the extended forecast
period this afternoon...as models all remain in good agreement
through period. Upper level ridging centered over the Pacific
northwest will keep persistent dry northwest flow across the
region through the bulk of the period. Models are not showing
anything in the way of quantitative precipitation forecast at this time..but flow would allow for
potential of backdoor energy into eastern most zones at least...so
will need to watch those areas closely in coming shifts. Have
continued with dry forecast. There are some indication of slight
stronger waves flattening the flow beginning Tuesday...but
currently best energy stays north...and conditions appear to
remain dry.

As for temperatures...expect to see above average reading throughout
the period. Ridging and downslope flow will result in temperatures in the upper
60s to middle 70s throughout the extended period. Aag



&&

Aviation...

VFR conditions will prevail overnight...with mainly clear skies
and light winds overnight. A quick-moving weather system will clip
the area during the day Thursday. Isolated/scattered rain showers
will develop across the area along and behind a cold front
Thursday afternoon...and could bring periods of MVFR/IFR
conditions and mountain obscurations. Winds will turn northwest
and gust to 25 kts behind the front.

Church

&&

Preliminary point temp/pops...

Thursday Friday Sat sun Monday Tuesday Wednesday
-----------------------------------------------------------
bil 044/052 030/060 047/073 047/069 048/071 049/070 047/066
03/west 10/u 00/u 11/u 10/u 11/b 11/b
lvm 036/054 025/064 041/070 040/067 042/070 043/070 041/067
12/west 10/b 00/u 11/u 11/u 11/u 11/b
hdn 039/055 027/060 041/074 045/069 046/071 047/071 044/069
04/west 10/u 00/u 11/u 11/u 11/b 11/b
mls 040/052 028/057 038/071 045/067 046/068 045/067 044/066
13/west 00/u 00/u 11/u 11/b 11/b 11/b
4bq 039/056 029/056 038/071 046/066 045/068 045/067 044/067
14/west 20/u 00/u 11/u 11/u 11/b 11/b
bhk 038/052 028/050 032/066 042/062 043/063 041/062 040/062
13/west 00/north 00/b 11/north 11/b 11/b 11/b
shr 036/057 026/057 037/071 043/067 042/070 043/069 042/068
05/west 20/u 00/u 11/u 10/u 11/u 11/b

&&

Byz watches/warnings/advisories...
Montana...none.
Wyoming...none.

&&

$$
Weather.Gov/Billings

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