Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 191139
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
539 AM MDT Tue Sep 19 2017

...UPDATED AVIATION...

.SYNOPSIS...

An active weather pattern will keep chances for rain and higher
elevation snow to western and southern portions today.
Meanwhile...the remaining areas will see slightly cooler
conditions with only an isolated rain shower possible. High
temperatures today will generally range in the 40s and 50s. Much
of the same is expected for Wednesday. Thursday and Friday will
see cooler temperatures and continued chances for rain and
mountain snow.

&&

.DISCUSSION...

Today through Thursday...A somewhat active pattern to continue
through the short term period. Currently we are seeing the exiting
of cold front across the CWA...with a few showers lingering across
the south and east in its wake. Snow levels this morning are
fairly reasonable and generally expected to be above 7000 feet. As
the cutoff mid level low associated with the front lingers in
Canada today...we see ourselves left in moist westerly flow. This
is a favorable pattern for continued showers across the south
through today...while downsloping air will keep only isolated to
scattered showers across the central and north. Weakly unstable
air may also provide for a few isolated thunderstorms today. A
brief lull in precipitation may then come tonight before a broad
and moist trough starts to push across the region for Wednesday.
This will bring chances for showers and higher elevation snow
through most of the day...with the best chances still coming
across the west and south. Wednesday night into Thursday sees a
weak cold front push through...once again bringing chances for
showers and perhaps some snow above 6000 feet. Models eventually
had this disturbance turning into a cutoff low Thursday into
Friday bringing widespread precipitation. Current model runs
starting to back down a little bit...although...still show perhaps
Thursday night into Friday the chances for widespread rain and
snow about 5500 feet and higher developing. Once again the south
has better chances for any precip...with some accumulating snow
possible to the mentioned elevated areas. This will have to be
watched for any winter highlights. Temperatures today through
Wednesday will be slightly before normal. Thursday sees temps even
more below normal with highs only in the 40s and 50s. Anglin

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 1200Z.

Exiting Cold front will continue to bring a few showers across
the region today...with the best chances coming across southern
and eastern MT. MVFR to brief IFR conditions are possible with
these showers...along with some higher elevation snow. Elsewhere
should be mainly VFR with some gusty winds possible and a slight
chance of a stray shower. A few areas may even see some VCTS this
afternoon...mainly from KHLN and southward. VFR conditions should
return to most sites tonight. Some gusty winds may also linger
through tonight...especially across central and northern sites.
Mountains will be obscured at times by clouds/smoke/precip. Anglin

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  56  39  56  36 /  20  20  30  30
CTB  55  36  54  34 /  10  10  10  20
HLN  53  35  56  35 /  40  30  50  30
BZN  50  33  54  34 /  70  50  40  40
WEY  38  24  42  29 /  80  70  60  70
DLN  48  30  50  29 /  40  30  40  40
HVR  61  39  60  37 /  20  20  10  10
LWT  54  36  56  36 /  30  20  30  20

&&

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

$$

weather.gov/greatfalls



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