Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 251733

Area Forecast Discussion
National Weather Service Great Falls MT
1131 AM MDT Sat Mar 25 2017

Aviation Section Updated


Splitting Pacific upper level trough continues to progress east
across the western US this morning with surface frontal boundary
now extending from eastern MT SW along the MT/WY/ID border. A few
showers linger this morning across far SW MT in the immediate
vicinity behind the front. Drier air is working east across
central and N-central MT. Weak instability and the arrival of
another minor embedded shortwave will result in the development of
showers this afternoon, primarily over the mountain areas.
Current forecast has this handled well with just a minor update of
PoPs and Wind to bring in latest short term model data and follow
observed trends. Hoenisch


Updated 1731Z.

A cold front has passed through the area with drier conditions
behind it. That said, behind the front, there is an area of moisture
moving NE out of the Great Basin/central Rockies that will clip
parts of SW MT and will likely aid in shower development this
afternoon/evening, possibly impacting KEKS/KBZN. A brief period of
lower CIGS/VIS cannot be ruled out at either site, but confidence is
too low to include any prevailing or TEMPO groups for SHRA at this
time. A weak upper level disturbance will move east through the area
this evening, with any shower activity ending from west to east in
its wake. Martin


/ISSUED 530 AM MDT Sat Mar 25 2017/

Today through Monday...A Pacific front has advanced through all
but far southern portions of the forecast area. The front is
associated with a weakening shortwave system crossing the
Canadian Rockies. Scattered rain and mountain snow showers over
Central and Southwest MT early this morning will gradually decline
in coverage while moving away to the east-southeast. SNOTEL
reports suggest mountain areas across southwest Montana could see
1-4 inches of fresh snowfall this morning. Roads around the the
West Yellowstone area may also see a slushy snow accumulation.
Isolated to scattered showers redevelop over mountain areas today
with weak mid-level instability, then continue into the evening
as another minor shortwave crosses the Northern Rockies. Breezy
west winds continue today and tonight across the North-central
plains with the passage of these two shortwaves. Fair weather
follows Sunday and Sunday night as weak ridging develops over the
area. The next Pacific trough arrives early Monday, with rain and
mountain snow showers advancing up to the Continental Divide and
spreading across Southwest Montana. PN

Monday Night through Saturday...A progressive pattern will be in
place for much of the workweek. The northern piece of a splitting
trough exits the area Monday night into early Tuesday with lingering
mountain snow showers, mainly over the far southeastern areas. A
transitory upper ridge builds over the area Wednesday, but is then
followed by a fast-moving yet digging upper level system that will
dive from the Northeast Pacific to the Southwest US and close off
into an upper low. This will bring unsettled weather to our region
in the late-week timeframe, though temperature trends since
yesterday have been warmer, indicating more of a rain threat outside
of the higher elevations of Southwest MT. Transitory upper ridging
then looks to build back across the region later Friday into the
weekend. Temperatures will average above normal through the period,
with the strongest warm anomalies coming Wednesday into early
Thursday under upper ridging ahead of the late-week storm system.


GTF  55  31  57  35 /  10  10   0  10
CTB  50  28  51  31 /  10  10   0  10
HLN  54  32  56  36 /  20  20   0  10
BZN  51  30  54  35 /  40  30  10  20
WEY  38  16  38  26 /  80  30  10  50
DLN  49  28  51  33 /  20  10   0  20
HVR  59  30  56  32 /  10  10   0   0
LWT  52  30  53  34 /  10  20   0  10



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