Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 192045
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
245 PM MDT Tue Sep 19 2017

.SYNOPSIS...

Moist westerly flow aloft will continue to bring clouds and
showers to the western and southwest Montana mountains. Breezy
conditions and continued cool temperatures with isolated showers
are expected over the plains. This pattern is expected to
continue tonight through Friday.

&&

.DISCUSSION...

Tonight through Thursday...An upper level trough of low pressure
will remain over southwestern Canada through Thursday. This
pattern will allow cool temperatures to continue across the
region, while west to southwest flow aloft will bring abundant
Pacific moisture to the region. Periods of rain and snow are
expected over the mountains of Southwest Montana and along the
Continental Divide through the short term. Meanwhile, mostly dry
conditions are anticipated over the Plains with only an isolated
shower or two moving off the mountains. Surface low pressure
system currently in southern Alberta will remain in place tonight
and Wednesday before ejecting eastward Wednesday night and
Thursday. As a result, tight pressure gradients will fuel gusty
west to southwest winds along the east slopes of the Rocky
Mountains and through the higher terrain of Southwest Montana.
Breezy to windy conditions are also anticipated over the plains,
although they are not expected to be as strong as in the higher
terrain. At this time, it does not appear than any highlights will
be necessary but this will continue to be monitored. mpj

Friday through Tuesday...Though there are still discrepancies to
resolve between the various global models and their ensembles, there
is moderate confidence that an area of deformation combined with a
strong surface front over south-central and northeastern Montana
will result in a potentially widespread area of rain and high-
elevation snow. The less-confident aspect of forecasting this event
at this point is just how widespread the precipitation is, with
lowering confidence as one moves north and west through our CWA.
Within the region of widespread precipitation, there will be the
potential for significant snow accumulations above 5500-ft
elevation. This system will finally begin to slowly exit the region
to the east late Friday into Saturday, with just residual rain and
mountain snow showers remaining behind. A quieter weather pattern
with periods of sun and clouds and perhaps a stray shower or two can
be expected early next week as northwesterly flow increases across
the region ahead of a potentially robust upper level ridge moving
onto the PacNW coast. CC

&&

.AVIATION...
Updated 1900Z.

Variable mid- and high-level clouds will prevail over the plains
and valleys for widespread VFR conditions along with gusty winds
and a slight chance for a stray shower or thunderstorm. The
western and southwest mountains will see cloudy conditions with
areas of rain and snow causing widespread obscurations at times
mpj

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  42  54  35  53 /  10  30  20  20
CTB  39  52  33  47 /  10  10  10  30
HLN  37  52  35  53 /  30  40  30  30
BZN  34  51  34  49 /  50  50  40  30
WEY  25  41  25  39 /  60  60  70  60
DLN  34  51  30  44 /  20  50  30  40
HVR  41  59  36  56 /  10   0  10  10
LWT  38  51  36  52 /  30  40  20  10

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

weather.gov/greatfalls



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