Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 172108

Area Forecast Discussion
National Weather Service Great Falls MT
308 PM MDT Sat Mar 17 2018


A complex storm system will moving through the area this weekend
bringing areas of snow and freezing drizzle. In the mountains, the
precipitation will mainly fall as snow. At lower elevations, the
precipitation type will fluctuate between snow and freezing
drizzle. Precipitation gradually winds down from west to east by
Sunday night. Some precipitation will linger over the mountains
and hi-line into Monday.


Today through Monday...The forecast remains complex with
continued uncertainty regarding precipitation type and amounts. A
slow-moving upper level low continues to edge east through the
Pacific NW early this morning. Several shortwaves have been
pinwheeling around this low over the past several days and this will
continue through the weekend.

The next wave to impact our forecast area is moving north towards
Montana. The models have continued the northward trend (seen over
the past few days) with the track of this low, which now places the
axis of heaviest snow further north as well. Further complicating
the forecast, the areas along/south of the track of this low may see
more dry air than originally forecast, making snow/rain totals
lower/less certain. This also makes precip-type more questionable,
especially over the plains of Central Montana. Any shift in this
current track will alter the areas of mixed precipitation and
amounts. Regardless, be prepared for mixed precipitation and
difficult travel conditions tonight into Sunday.

An area of steadier/heavier precip moving north out of Idaho will
lead to impactful snow at higher elevations of SW MT, primarily
above 6500 feet. The Winter Weather Advisory in this area has been
adjusted and now is only in effect for mountain passes and does NOT
include valleys such as Dillon, Ennis, or Bozeman. This area of snow
should weaken with time as it pushes north. Another band of steadier
precip will develop near Helena and extend northeast through parts
of Central Montana. Forecast models continue to trend further
northwest with this band which puts more emphasis on the Rocky Mtn
Front and areas west of I-15. Because of this trend, the Winter
Weather Advisory was expanded north. Along and east of I-15, the
precip-type will fluctuate between snow and freezing drizzle.
Ultimately, this will lead to lower snowfall amounts than originally
forecast, but the combination of snow and freezing drizzle will lead
to travel concerns and the Winter Weather Advisory will stand for
now. Precip should begin to wind down from west to east on Sunday
with light snow lingering in the mountains through Monday. MARTIN/MLS

Monday night through Saturday...the chances for precipitation
during this period peak in the Thursday and Friday timeframe. The
models do have reasonable agreement during this period on the
timing and placement of precipitation. Temperatures should peak
Wednesday and Thursday, but still not a big warmup with highs
mainly in the 40s to mid 50s...with 30s over the hi-line. db


Updated 2105Z.

FG and IFR/LIFR conditions will continue to cause significant
aviation impacts across north-central MT through early this
afternoon. Elsewhere across north-central Montana, conditions are
gradually improving with cigs lifting.

Another weather system will begin to move into Montana from the
Great Basin bringing light rain and snow to southwest Montana by
this evening, then spreading north tonight with the possibility for
mixed precipitation. Precipitation type will primarily be light
snow, however may mix with freezing rain or drizzle, especially from
KGTF-KCTB-KHVR. Low cigs/vis are also likely with periods of IFR and
LIFR at all sites in falling precipitation. Mountains will be
obscured through the forecast period. Precipitation will gradually
diminish Monday afternoon most areas...but still linger in and
near the mountains. Low cigs will also persist. MLS/DB


Updated 17/300 PM.

General lowland flooding from snowmelt will continue to be a
concern over the weekend, especially across SW MT where
temperatures will warm somewhat. We will continue to cover these
hazards with Hydrologic Outlooks and Flood Advisories for now.

Temperatures will warm each day to start the upcoming work week,
with highs peaking on Wednesday and Thursday in the mid-40s to
mid-50s across Southwest and portions of North Central Montana, or
generally along and southwest of a Lewistown...Great
Falls...Choteau line. This will lead to continued snowmelt for
snow remaining at both lower and even high elevations during the
daytime hours. A large upper level disturbance is then expected to
move across the Northern Rockies during the second half of next
week, which could bring accumulating snow to the mountains of
Southwest and North Central Montana and rain/snow to lower
elevations. Any liquid precipitation on top of the remaining and
warmed snowpack, will only lead to additional flooding concerns
where poor drainage exists. MARTIN/Moldan/DB


GTF  24  36  20  39 /  70  50  30  20
CTB  22  32  17  34 /  70  70  30  20
HLN  28  38  24  41 /  60  70  50  20
BZN  22  39  20  40 /  30  40  30  20
WEY  14  29  13  31 /  30  50  50  30
DLN  20  36  16  36 /  40  60  50  20
HVR  19  34  16  30 /  60  70  40  20
LWT  22  35  19  37 /  30  30  30  20



Flood Advisory continues until further notice for snowmelt in
Jefferson...Broadwater...and Northern Gallatin Counties until Friday

Winter Weather Advisory from midnight tonight to noon MDT Sunday
Eastern Glacier...Eastern Pondera...Eastern Teton...Hill...

Winter Weather Advisory until 6 AM MDT Sunday above 6500 feet
for Beaverhead...Gallatin...Madison.

Winter Weather Advisory until noon MDT Sunday for Central and
Southern Lewis and Clark...Jefferson.

Winter Weather Advisory from 6 PM this evening to noon MDT
Sunday Cascade...Chouteau.

Winter Weather Advisory from 6 PM this evening to noon MDT
Sunday Northern Rocky Mountain Front...Southern Rocky Mountain


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