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Area forecast discussion...updated 
National Weather Service Billings Montana
953 am MDT Wednesday Aug 31 2016

Update...
current forecast is in good shape and made only minor tweaks to
it. Upper ridge was still firmly in place with axis running
through eastern Montana. This will provide yet another hot day
with high temperatures in the 90s. The placement of the ridge will
keep the strongest energy farther west with shortwaves running
mainly into western Montana. Models do place some weak energy over
the park this afternoon for potential convective development
running into the beartooth/Absaroka Mountains, but this should be
quite isolated. Would not be surprised to see all the convection
developing to the west of our area though given the placement of
the ridge axis. Will leave low pops in for now, but confidence not
high on that activity developing. Did add areas of smoke to
western locations, per the what happened yesterday. Twh

&&

Short term...valid for tdy and Thu...

Water vapor imagery shows a strong ridge over the central rockies
and northern High Plains, with a trof off the Pacific coast and
several weak shortwaves embedded within the SW flow over the
western states and along the coast. Energy of interest is moving
into northern California and will lift toward western Montana later
today. This combined with a modest increase in mid-high level
moisture should bring an increased potential for high-based
T-storms in our far west late this afternoon and evening.
Strongest forcing and deepest moisture will reside west of our cwa
though, so am comfortable with sustaining only isolated pops west
of Billings, though some light showers or sprinkles may drift east
thru the Billings area late tonight as weak mid level trof moves
across central Montana.

Greater chance of convection in our west and central parts will be
on Thursday as SW flow deepens and more pv lifts out of the Great
Basin. Pwats expected to rise modestly toward three-quarters of an
inch, but T-storms will remain high-based with erratic sfc winds
being the primary risk.

Our east will see mid level capping and increased S-southeast winds over
the next two days, as pressure gradient tightens on western edge
of northern plains high. Winds will gust to 30+ mph along the
Dakotas border today, and winds will stay elevated tonight with 40
kts of 850mb flow developing. Core of strongest winds will begin
to shift east Thursday but places like Baker and Ekalaka will
remain windy for another day. With this in mind let's talk fire
weather.

Rhs will drop from tuesday's values but per latest guidance should
stay near or a bit above 20 percent in our far east today.
Humidity will be lower further west and areas from 4bq to mls
could see gusts to 25 mph for a few hours this afternoon.
Complicating factor in these areas could be additional smoke from
a new wildfire in northeast Wyoming. Overall do not see a strong need
for a fire weather highlight today, but will keep strong wording
in fwf for increased southerly winds over the next two days.
Further west, thunderstorm coverage and wind will be low today,
and in fact the convective potential in Park County may be
severely limited by smoke from Yellowstone Park, as latest hrrr
suggests a notable plume today. Thunderstorm coverage should
increase in our west Thursday as already mentioned, but with a
trend up in humidity and mid level flow on the order of only 15-20
kts, and again smoke concerns. So with the uncertainty will let
day shift further evaluate fire concerns for Thursday in our west.

Temps the next two days will remain above normal with highs in the
upper 80s and 90s, consistent with 700mb temps between 13-15c.
Smoke will almost certainly be a factor and could hold temps down
a few degrees as they did in places on Tuesday. For this reason
have lowered expected high temps just slightly. Jkl

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

Despite some pattern uncertainty during the extended period in the
ensembles, there was enough confidence to increase pops in certain
portions of the forecast.

Amplified Pacific trough, seen in water vapor imagery off the
western U.S. And Canadian coasts early this morning, will reach northwest
Montana on Friday. While precipitable waters will be a half inch to an
inch, the moisture was confined to the upper levels of the
atmosphere. GFS showed some high MUCAPES along the eastern border
in the morning on the edge of an 850 jet. Models have become
closer with the frontal timing and brought the cold front into the
central zones by 00z Saturday. Left some low pops in the far east
in the morning due to the above, and lingered them into the
afternoon. Also had low pops behind the front, west of kbil, in the
afternoon. Went a little below the blended guidance for high
temperatures with expected effects from smoke from Wyoming fires.
However, it will still be hot over a good portion of the area with
rh's in the teens to lower 20s. The above factors, combined with
increasing west winds behind the front, will likely result in fire
weather headlines for Friday and Friday evening. The European model (ecmwf) and GFS
both form an upper low in the northern part of the trough Fri.
Night and push the low into Canada. The trough will continue
pushing east Fri. Night. Went with slight chance pops across the area
Post-frontally.

For Sat. And Sat. Night, the trough digs into the Pacific NW,
while cold advection and moisture increase over the region.
Increased pops during this period. Sat. Will be cooler, and
breezy in spots, with highs in the 70s. The GFS came in colder at
700 mb than the European model (ecmwf) for Sat. Night, so the snow level in the
mountains was a bit uncertain. Did have some light snow
accumulation in the highest elevations of the SW mountains. The
next trough from the Pacific northwest approaches the area sun. And Sun.
Night. Raised pops during these periods with plenty of moisture
over the area. Model temperature blends gave highs in the upper
60s/lower 70s.

Models kept troughiness over the area for the rest of the extended
period with minor differences. Raised pops on Mon. And had
temperatures in the 60s. The flow began to look drier and had more
of a downslope component for Tue. Through Wed., So leaned toward
climo pops/drier conditions. Arthur

&&

Aviation...

VFR will prevail across the area today and tonight. An isolated
dry thunderstorm is possible west and southwest of kbil late this
afternoon and evening. Gusty surface winds are possible with any
thunderstorms. Smoke may lower visibilities over klvm today.
Localized mountain obscurations are possible over the crazys and
beartooths/absarokas late this afternoon through tonight. A few
light showers are possible tonight from around kbil west. Low level wind shear is
expected tonight in kmls and kbil mainly after 03z Thu. Low level wind shear
possible near kshr mainly between 01z and 05z Thu. Rms/twh

&&

Preliminary point temp/pops...

Tdy Thu Fri Sat sun Mon Tue
-------------------------------------------------------
bil 094 065/092 063/090 054/076 051/070 048/064 044/069
0/u 12/T 21/u 22/west 34/west 55/T 22/west
lvm 093 056/091 053/083 044/073 041/067 041/061 037/068
2/T 23/T 32/T 22/west 33/west 55/T 22/west
hdn 098 060/096 059/094 053/078 050/072 046/067 040/071
0/u 12/T 21/u 23/west 34/west 55/T 22/west
mls 097 065/097 065/095 057/078 053/073 050/066 045/070
0/north 02/T 21/b 23/west 33/west 55/T 32/T
4bq 092 063/094 063/095 056/078 052/073 050/067 045/070
0/north 01/north 22/T 24/west 44/west 55/T 22/T
bhk 091 062/090 062/094 055/077 050/071 048/065 045/067
0/north 01/north 22/T 23/west 44/west 55/T 32/T
shr 096 058/095 057/091 051/077 048/072 045/066 041/069
0/north 02/T 21/b 24/west 44/west 55/T 22/west

&&

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

&&

$$
Weather.Gov/Billings

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