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Area forecast discussion
National Weather Service Great Falls Montana
739 PM MST Tue Jan 23 2018


Only minor updates to the overnight forecast. Temperatures are
running somewhat cooler than those in the previous forecast,
especially across southwest Montana and over the northeast tfx
plains (including the Havre area), so have generally lowered lows
there between 5 and 10 degrees. Milk River Valley east of Havre
also has very small temperature-dewpoint spread, so have added
mention of patchy freezing fog there for after midnight through
most of Wednesday morning. The rest of the forecast appears to be
on track. Coulston



Mainly dry conditions, breezy winds, and an overall moderation in
temperatures are expected through Wednesday, as the next Pacific
disturbance approaches. The disturbance and accompanying cold
front will then sweep through our area on Thursday, resulting in
an increased potential for snow, especially for the Rocky Mountain
front, as well as central and southwest Montana. Cooler
temperatures and a continued chance of snow are in the forecast
for Friday, with the best chance for snow in the mountains.


updated 2350z.

VFR conditions will likely continue through at least the next 24
hours due to high pressure aloft. A weak disturbance will bring
areas of mid and high level cloudiness to the area, along with some
mountain top obscuring snow along and west of the Continental
Divide. Breezy southwest downslope wind will keep the terminals dry,
but it will likely cause areas of moderate turbulence and mountain
wave activity. Coulston


Previous discussion...
/issued 450 PM MST Tue Jan 23 2018/

Rest of today through Thursday...a high pressure ridge aloft will
crest over our region tonight into Wednesday morning as the next
Pacific weather disturbance approaches. Predominantly
southwesterly flow aloft is then expected later Wednesday into
Thursday, with the aforementioned disturbance beginning to enter
our region by early evening on Thursday. In addition, a Pacific
cold front will sweep across the County Warning Area on Thursday. This pattern
will support periods of mountain snow. At lower elevations, the
Chinook effect will likely promote dry conditions through
Wednesday. On Thursday, the potential for precipitation, mainly
in the form of snow, increases at lower elevations. This is
particularly the case for the southwest Montana valleys. At this
time, no significant snow accumulations are expected areawide.
Overall, temperatures will remain above-normal. Wednesday will
likely be the warmest day, when warm advection occurs ahead of
the approaching disturbance and front.

Thursday night through Tuesday...cold front exits the region
Thursday night...ending the initial round of Snow. Flat ridging
then leaves US in a zonal moist westerly flow for Friday. This
could bring scattered areas of light snow showers and lingering
mountain snow. A pattern of brief ridging followed by moist
westerly flow then looks to be the story of the weekend. A brief
ridge moves through Saturday morning before moist westerly flow
moves through the rest of Saturday. This combined with a weak
warm front boundary could bring more scattered snow showers and
mountain snow on Saturday...with a similar pattern also expected
for Sunday. A mainly dry and breezy pattern looks to be possible
for Monday. Models are then indicating a larger wave and stronger
cold front may then push across the region sometime early next
week. The exact timing is still in disagreement...with some
models indicating impacts could be seen as early as Tuesday. If
that is the case...this quick hitting system could bring chances
for widespread snow and colder conditions. Temperatures Friday
through Saturday look to be near seasonal normals...with a slight
warm up on Sunday and Monday. After that models
diverge...although it does appear a cool down is in store if the
aforementioned disturbance moves through.


Preliminary point temps/pops...
gtf 29 46 32 42 / 10 10 0 20
ctb 24 40 25 38 / 10 10 10 10
hln 17 38 21 32 / 10 10 0 40
bzn 12 37 21 34 / 10 10 0 40
wey 10 31 15 28 / 30 20 10 60
dln 10 37 24 34 / 10 10 10 40
hvr 15 36 20 36 / 10 10 10 10
lwt 21 40 27 40 / 10 10 0 10


Tfx watches/warnings/advisories...

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