Area Forecast Discussion
Issued by NWS Great Falls, MT

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703
FXUS65 KTFX 221744
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
1145 AM MDT MON AUG 22 2016

Aviation section updated

.UPDATE...

For the morning update, adjusted wind/wind gusts to match current
obs. The wind continues to steadily increase along and just east
of the Rocky Mtn Front. KCTB recently gusted to 44 mph and sites
closer to the Front have already gusted in excess of 70 mph. The
wind will continue to increase for areas further east by this
afternoon. Of note, the 700 mb wind speed of 45kt on the 12z TFX
sounding this morning was 4-5 std deviations above the mean for
August and about 8kt shy of the record 700 mb wind speed for
August, so a decent wind event beginning/ongoing for parts of
central Montana. That said, still thinking the wind today will
remain below high wind criteria, so no warnings anticipated at
this time.

The other change for the update was to keep areas of smoke in the
forecast through this afternoon across parts of central Montana.
Quite the smoke plume coming off the Copper King fire in NW MT at
this time and this smoke has reached some of our northern counties from
GNP to Inverness and has caused a reduction in visibility at
times (note CTB got down below 2 miles at times this morning).
HRRR smoke guidance has this smoke plume shifting south some this
afternoon (ie. between Cut Bank and Choteau) and thinking this is
the area that will see the main smoke impacts this afternoon.
Given the strong low to mid level winds, smoke may reach even
farther east than currently depicted. With the increasing wind and
dry conditions, fire weather concerns remain. For a more detailed
discussion regarding the wildland fire potential, see the Fire
Weather Section below. Martin

&&

.AVIATION...
UPDATED 1745Z.
Windy conditions can be expected across the region, along with
widespread areas of smoke. The denser smoke is as far south as the
Great Falls area, and as far north/east as the Cut Bank/Havre areas.
Smoke should reside in these areas through the afternoon. Mountains
will be obscured in these regions as well. Otherwise just some
passing mid/high level clouds are expected. Brusda

&&

.FIRE WEATHER...
Red Flag Warning is now in effect beginning at noon Monday until 9
PM MDT Monday evening...for much of west central and southwestern
Montana...now including fire weather zone 117 and 123. Forecast
remains on track for widespread low humidities (10- 19%) and gusty
winds (15-25 mph sustained, with gusts 30-45 mph and a few spots of
50+ mph close to the Continental Divide) as a dry cold front pushes
across the forecast area. The main change today is the addition of
Fire Weather Zone 117 (mainly for Cascade and Meagher Counties) and
123 into the Red Flag Warnings. Here winds and RH values are likely
to hit critical values. The debate was how critical were the
fuels...especially with all the recent rains.
With Saturday and Sunday being very dry days...and current RH
values struggling to rebound...collaborated with neighboring
offices to add in these two zones to the Red Flag Warning. The
warning was also extended until 9 PM to account for continued
gusty winds and low RH this evening...as well as...matching well
with neighboring offices. Zones without Red Flag Warnings are
still experiencing fuels below critical status...however...with
the widespread low RH and strong winds today...elevated to near
critical fire danger is expected. Slightly diminishing winds...and
increasing RH from wrap around moisture...should lower the fire
danger for Tuesday...except across far sw MT where low RH may
continue. Anglin/Martin

&&

.PREV DISCUSSION...
/ISSUED 527 AM MDT MON AUG 22 2016/

Today through Wednesday...WV currently showing the upper level low
that will impact the region during the short term inland across
British Columbia. Two distinct features can be seen on WV that
will control our weather for today. First is the strengthening 700
mb winds starting to bring increase sw flow into MT. This feature
should start to increase winds this morning across much of the
CWA. Portions across the Rocky Mountain Front are still expected
to see gusts over 50 MPH develop this morning...with most other
areas expected to see gusts of 30 to 40 MPH by the end of the
morning hours. Fires that have flared up in ID and western MT will
also bring increase smoke to the region today...with Cut Bank
already reporting haze. The second feature currently showing up on
WV is the dry front associated with this feature...currently
located in WA. This dry front will push across the region this
afternoon...continuing strong winds and dry conditions. In fact
not much precipitation is expected from this front...with only a
few isolated showers possible across far NW and SW portions of the
CWA. It still looks like this front will help to lessen the
gradient and break down the mountain wave currently trying to set
up. So winds may peak by early afternoon...but still remain gusty
through the afternoon and early evening hours. With the strong
winds and very dry air associated with this feature elevated to
critical fire weather danger is expected today. Multiple Red Flag
Warnings have been issued from noon until 9 pm tonight. See the
Fire Weather Discussion for more details.

Upper low the rides along the Canadian and MT border tonight
through Tuesday bringing wrap around moisture into the
region...and lingered breezy conditions. Isolated to widely
scattered showers could result from this wrap around moisture for
Tuesday. The northerly flow this disturbance provides actually
increases moisture across the region for Tuesday. That combined
with some weak instability could support a few thunderstorms for
Tuesday afternoon and evening...however...shear diminishes as the
upper low pulls out of the region...and will make it difficult to
sustain any stronger thunderstorms. Wrap around moisture could
then linger for Tuesday night...keeping a few scattered showers
possible.

Models cannot come together on Wednesday. Some are hinting an
interesting weather set up may occur. As the upper low moves into
the far Northern Plains and a high pressure system builds across
the Pac NW....a secondary front moves into the region. This brings
in one more push of moisture...and could provide sort of an
easterly upslope pattern. GFS not quite as impressed with this set
up...however...00z NAM and Euro solutions sort of indicating a
weak shortwave accompanies the mentioned secondary front...and
indicates more widespread showers possible...especially in the
easterly upslope favored areas. Increased pops slightly to account
for the NAM and Euro solutions...but will have to be watched to
see which way models trend. With the series of cold fronts...high
temperatures will cool each day during the short term. Today`s
highs will be in the 70s and 80s...with 70s on Tuesday...and
possibly cooling into the 60s Wednesday. Anglin

Wednesday night through Monday...Forecast period starts off with
north/northwest flow aloft over the state and a relatively cool
airmass in place. Medium range model solutions quickly diverge with
the ECMWF keeping weak troughing over the region through Saturday
morning while the GFS trends toward building a short wave ridge over
the state. Both models gradually trend toward developing a weak
trough over British Columbia with flow over Montana backing to the
southwest by next Monday morning. Despite these differences, the
overall forecast for Montana will should remain relatively quiet
through next weekend. Have pretty much left the going forecast in
place with temperatures expected to rebound back toward seasonal
averages by Saturday. Conditions during the period will range from
mostly dry to slight chance PoPs at best prevailing for much of the
period. mpj

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  80  50  71  46 /   0   0  10  20
CTB  71  51  65  47 /   0  20  20  20
HLN  80  51  74  50 /   0   0  10  10
BZN  84  45  75  45 /   0   0  10  10
WEY  77  41  68  34 /   0   0   0   0
DLN  80  43  74  43 /   0   0   0  10
HVR  81  52  70  50 /   0  10  20  20
LWT  81  51  69  48 /   0   0  10  20

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning until 9 PM MDT this evening for MTZ110-111-114-
116>118-123.

&&

$$

weather.gov/greatfalls



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