Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 181741

Area Forecast Discussion
National Weather Service Great Falls MT
1740 AM MDT Tue Oct 18 2016


Updated forecast is out. Sent a refresh on wx,pops,temps for
today. Light showers are exiting Blaine county with a few
sprinkles moving through the Helena Valley. Patchy dense fog
continues in the Cut Bank/Shelby area...this fog should dissipate
early this afternoon. Temperatures will be colder in the Cut Bank
area because of the northerly winds otherwise most other
temperatures are on track. Brusda


Updated 1740Z.

VFR conditions expected. Moisture traversing WNW flow aloft will
generally SCT-BKN mid-level clouds over central/southwest MT through
this aftn. -SHRA associated with a weak cold front near KHVR have
almost completely dissipated based on latest obs and radar imagery so
have removed mention of precipitation, but also added mention of
morning fog there in 18Z TAF. Large swath of moisture currently over
central Idaho will move into the region by late aftn/evening,
bringing more widespread BKN-OVC skies, with scattered -SHRA
and occasional MVFR ceilings near KHLN/KBZN/KEKS.


/ISSUED 548 AM MDT Tue Oct 18 2016/

Today through Thursday...We find ourselves in between systems at
the moment this morning. A surface cold front has pushed into
northern portions...and is expected to stall as it pushes
south...perhaps as far south as Teton...Cascade...and Chouteau
counties. Slight chances for isolated to widely scattered rain
showers will be the result of this weak front. With the cooler
temps and changing winds...areas of patch fog...perhaps dense at
times...will also be possible this morning...mainly across the Hi-
Line. The story for the rest of the day is the progression of
another upper level disturbance...mainly across western and
southern portions of the CWA. This disturbance is currently
located across Oregon and Idaho...perhaps delaying precip start
times to this afternoon and early evening across some areas in the
southwest. Snow levels will again drop into that 6000-7000 foot
range...keeping snow limited to the higher elevations and a few
mountain passes. Little impacts were seen yesterday with similar
snow levels...thus thinking impacts today will remain low...and
below advisory criteria. Snow accumulations of up to 1-2 inches
will be possible at the lower extent of these snow levels...with
4-6 inches across the higher terrain. This disturbance will also
linger slight chances of rain showers for northern portions of the
CWA...this afternoon through the evening. Precipitation then
begins to diminish tonight...and by early Wednesday morning may
only be found across isolated to scattered locations in western
and southern portions. Snow levels may come down to around 5000
feet Tuesday night into Wednesday...however...snow accumulations
will remain light and cause little impact. High pressure then
approaches the region for the rest of Wednesday...however
lingering moisture in nw flow could provide for a few isolated to
widely scattered rain and mountain snow showers across the region.
High pressure and dry conditions then arrive for Wednesday night.
Models now indicate this high pressure ridge will be short lived.
We then quickly return to quick and increasingly moist westerly
flow for Thursday. The Rocky Mountain Front will have a good
chance to see upslope showers return with snow around 7000 feet.
Moisture could stream east of Rockies...and with some weak warm
air advection...a few isolated to widely scattered rain showers
may also develop. Placed in slight chances as a result of this for
much of the CWA...minus the southwest. This increased westerly
flow may also bring some gusty winds at times for
Thursday...although still looking to be short of High Wind
Criteria. That said...gusts over 50 MPH will be possible along the
Rocky Mountain Front...with 30-40 MPH possible elsewhere. Temps
will remain near seasonal norms in the 50s today and again
Wednesday. The warming air from our westerly flow should warm
temps slightly on Thursday...perhaps seeing the return of 60s
across a few areas. Anglin

Thursday Night through Tuesday...Forecast models are now in
relatively good agreement throughout this period. High pressure
aloft will move east across the Southwestern United States/Northern
Mexico border area through Friday night. This will strengthen the
upper level ridge over the Western/Central U.S., and keep Montana
under a relatively strong westerly flow aloft. A disturbance in the
flow continues to bring a chance for strong westerly surface winds
Thursday night into Friday morning, but models are not as strong and
persistent as last night`s forecast, lessening the potential for
high wind highlights for now. However, this disturbance will likely
bring showers to the western mountains, with scattered showers
possibly moving out across Central Montana with the passage of the
disturbance. Precipitation chances will decrease with the exit of
the disturbance, but weaker disturbances will keep a chance for
showers over much of North Central and Central Montana for Friday
night through Saturday night, which is a minor difference over the
previous forecast.

The medium range models agree on digging a deep upper level low
pressure trough off the Pacific Northwest coast Sunday into Monday,
which will help amplify the high pressure ridge over the Central
U.S. This will keep any chance of showers over the mountains. The
models then bring a shortwave trough into the area from the
southwest for Monday night into Tuesday, spreading a chance for
showers over much of the area. Overall, temperatures will remain
near seasonal averages, with highs mostly in the upper 40s and 50s
and lows in the 30s to lower 40s.


GTF  55  37  53  35 /  20  10  20   0
CTB  46  34  51  32 /  20  10  10   0
HLN  54  35  51  32 /  20  30  20   0
BZN  52  34  49  29 /  20  60  20   0
WEY  39  25  40  21 /  40  60  20   0
DLN  50  29  47  30 /  30  40  10   0
HVR  46  32  51  30 /  20  20  20  10
LWT  53  34  49  32 /  10  20  20  10




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