Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 111635

Area Forecast Discussion
National Weather Service Great Falls MT
935 AM MST Mon Dec 11 2017

With an upper level ridge of high pressure to our west, expect
mostly sunny skies over the region for the next few days. Afternoon
temperatures will be about 10 degrees above normal over the northern
Plains, while near normal temperature and morning fog can be
expected in the valleys of Southwest MT. A change in the weather
pattern is possible by next weekend, with a better chance for rain
and snow showers.



Forecast pattern continues to serve up more of the same... strong
ridge over the West Coast with north-northwest flow aloft over
Montana. Variable high level clouds continue advecting over the
region in the flow aloft with warm and breezy conditions expected
over the plains. Valley inversions keep temperatures cooler in
Southwest Montana with areas of morning fog. Am a little concerned
that forecast high temperatures across North Central Montana
today may be a touch too warm, but have opted to leave them as-is
for now as temperatures have been running well above guidance
lately. Went ahead and updated sky condition to indicate higher
cloud coverage and also did some fine-tuning of winds, mainly to
increase them a few knots in some of the windier locations.
Remainder of the forecast is in good shape and don`t anticipate
any further updates this morning. For the afternoon package, I am
going to be looking a bit closer at wind speeds for Tuesday as a
few models suggest that borderline high wind conditions are
possible. mpj


Updated 1055z.
VFR conditions will prevail across much of the region through the
period. The exception will be the valleys of Southwest MT, mainly
around Helena/West Yellowstone where some patchy freezing fog is
possible before 17z. Otherwise no other aviation impacts are
expected at this time. Brusda


/ISSUED 430 AM MST Mon Dec 11 2017/
Today through Tuesday...A ridge of high pressure will be over the
region, resulting in dry conditions prevailing. Some morning fog
will be possible in the Southwest valleys today and Tuesday
morning. Forecast temperatures continue to be well below
guidance over the Southwest. Over North Central MT, went above
guidance for today, but not quite as warm as yesterday. It remains
mild on Tuesday, with overall wind speeds on the light side today,
but increasing back to windy for Tuesday over North Central MT.

Wednesday...A weak upper level disturbance will move through
Southwest MT, with a light snow shower possible around Big Sky.
Otherwise persistence continues across the region for

Thursday/Friday...The start of a gradual weather change to more
December like conditions should begin. A stronger upper level
disturbance will move into the Northern Rockies by late Friday,
producing some rain/snow showers over the region. The
precipitation looks to be most widespread Friday night. Afternoon
temperatures will still average about 10 degrees above normal for
most areas though. There is the potential for some stronger winds
during this period, especially along the front range of the Rockies.

For Saturday through Monday...Confidence in the forecast gets
lower each day through the period...becoming quite low by Monday.
Expect a few passing showers on Saturday, with forecast models
differing for Sun/Mon. The EC wants to bring in a fairly good size
weather system for late Sunday into Monday. This would result in
colder temperatures and a good chance for accumulating snow. The
GFS/NBM is drier and not as aggressive with the colder air. For
now I leaned towards the GFS/NBM solution, but significant changes
in the forecast are possible by early next week. Brusda


GTF  54  33  55  31 /   0   0   0   0
CTB  55  28  56  28 /   0   0   0   0
HLN  34  14  35  14 /   0   0   0   0
BZN  32   6  33   9 /   0   0   0   0
WEY  25 -11  26  -7 /   0   0   0   0
DLN  36  15  37  15 /   0   0   0   0
HVR  56  26  57  26 /   0   0   0   0
LWT  50  34  55  30 /   0   0   0   0



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