High Wind in Montana, November 14, 2016

Area Forecast Discussion
National Weather Service Great Falls MT
1025 PM MST Sun Nov 13 2016

UPDATED AVIATION SECTION

.DISCUSSION...

Main update this evening was to increase winds over the North
Central Montana plains, and upgrade the High Wind Watch to a
Warning for the plains adjacent to the Rocky Mountain Front.
Models continue to indicate that strong winds between 850 and 700
mb will mix down to the surface in these areas Monday morning
through Monday afternoon, producing gusts up to 65 mph at times.
Even stronger winds are likely closer to the Rocky Mountain Front
(gusts to 80 mph at times in favored areas), so have left the
Warning there as is. Did not change the valid times of the
Warnings, as they appear to still be on track to increase over the
Rocky Mountain Front after midnight and spread out over the plains
after 9 am Monday. More localized strong wind gusts may occur in
some favored areas elsewhere, so will keep an eye on those areas
for possible further highlights. The remainder of the forecast
seems to be handling the situation well.
Coulston

&&

.AVIATION...
Updated 0525Z.

VFR conditions will continue over North Central and Southwest
Montana through at least Monday evening under scattered to broken
mid and high level cloudiness. Clouds may obscure mountain tops at
times along the Continental Divide. However, the wind will be the
main impact during this period. Strong westerly winds aloft will
continue to mix down to the surface over the area from the west
through 18Z or so, continuing through the remainder of the period.
The strongest winds will be east of Interstate 15 along the Rocky
Mountain Front. Gusts close to the Front will mostly be in the 50 to
70 kt range at times, with gusts increasing to between 40 and 50 kt
at times over the adjacent plains through 12Z. East of I-15, gusts
of 30 to 40 kt will be common after 12Z. Winds will also be strong
over ridge tops, but they will be less gusty in the southwest
valleys. Coulston

&&

.PREV DISCUSSION...
/ISSUED 450 PM MST Sun Nov 13 2016/

Tonight through Wednesday...A brisk westerly flow aloft will
continue to reside over the region through Tuesday. Winds could
be strong at times, thus the high wind watch has been changed to
a high wind warning for the Rocky Mountain Front. There is the
potential for strong winds in the Cut Bank/Shelby/Conrad/Chester
areas as well on Monday, thus these areas have been put in a high
wind watch. Expect a chance for precipitation mainly over the
western mountains, but an isolated shower is possible tonight
over the central mountain ranges. Afternoon temperatures will
remain mild through Tuesday. However, on Tuesday afternoon a
stronger area of low pressure will approach the region with the
area of low pressure moving through the region early Wednesday
morning. Expect colder air to move into the region during the day
on Wednesday. Precipitation should also become more widespread on
Wednesday over Southwest MT. Rain could start to change to snow
by Wednesday evening at lower elevations as the cold air moves
in. Forecast models are still quite uncertain, but we did send
our current estimated snowfall maps to the web.
Brusda

Wednesday night through Friday...Models still coming together on
widespread snow possible spreading from south to north Wednesday
night through the day Thursday. The northern extent of the snow
is still up to be determined. GFS blankets the entire CWA in
light...to at times moderate snow...while Euro has the best
chances for snow only reaching as far north as the Rocky Mountain
Front to Great Falls to Lewistown. Still maintained at least
slight chances across the entire CWA...while trying to put likely
where Euro and GFS solution agree. As a result snow accumulations
were bumped up slightly for Thursday...with 1 to 3 inches
possible across the lower elevations....and 4 to 8 across the
mountains...with up to a foot at the highest peaks. It should be
noted the GFS solution is colder and more aggressive...so higher
accumulations are possible for Thursday...although would like to
see more model agreement before hedging that way. The bigger
disagreement comes Friday. GFS lingers wrap around snow across
the region for much of the day...while the Euro has a more
progressive solution and ends snow much earlier. Compromised for
now and left slight chance to chance pops as previous models have
shown this slower snow lingering solution. The other item that
will be needed to watch is temperatures. Again GFS is much colder
and has lows and highs well below season norms...while the Euro
shows more a quick hitting cold burst of air then slowly warming
us back up to near normal readings. It will come down to how much
snow we actually receive. The more snow the cooler temps.
Compromised...and lowered...temps as well in the long term.

Saturday through Sunday...Ridge of high pressure should bring
warming and mainly dry condtions, however, a few snow showers are
possible along the Continental Divide Saturday through Sunday, as
multiple and subtle eastward-moving shortwave troughs may
traverse the mid-to upper-level ridge. Temperatures should
moderate during this period, with lows near-normal to about 10
degrees above normal and highs about 10 degrees below normal on
Friday warming to near- normal for the weekend. However, snow
cover from the mid- week system may cause temperatures to be
colder, especially in southwest MT valleys.
Jaszka/Anglin

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  46  60  43  59 /  20  10  20  20
CTB  43  55  35  52 /  10  10  20  20
HLN  44  59  37  58 /  10  10  10  30
BZN  39  62  41  58 /  10  10  20  20
WEY  30  46  31  48 /  10  10  20  30
DLN  39  61  38  57 /  10  10  20  20
HVR  42  60  35  55 /  10  20  10  20
LWT  41  59  39  58 /  20  10  20  30

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
High Wind Warning from midnight tonight to 8 PM MST Monday
Northern Rocky Mountain Front...Southern Rocky Mountain Front.

High Wind Warning from 9 AM to 8 PM MST Monday Eastern Glacier...
Eastern Pondera...Liberty...Toole.

&&

weather.gov/greatfalls