Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 180232

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


Upper level low has set up a band of mainly snow across portions
of central MT while wrap-around snow is also found for western
and southwestern MT. Radar trends are showing the precip slightly
south of model predictions...centering more around the Great
Falls area versus the expected track of setting north of this
area. This may result in more precipitation for this area.
However, warm surface temperatures appear to be limiting snow have lowered snow ratios. The end result is
similar QPF with slightly less snow accumulations for the current
band in central MT.

As this system lifts north tonight chances for snow will continue
for much of the CWA. Dry air wrapping into the system will allow
for some areas of freezing rain/drizzle and perhaps some patchy
fog. Best chances for this look to be across northern and central
portions with a light ice glaze possible. Although the update may
have slightly lowered overall snow accumulations...advisories
will remain for the potential of impactful snow and some freezing
rain/drizzle. Snow still looks to become more scattered and
confined to the mountains Sunday afternoon through Sunday night.



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.


Updated 0220Z.

Another weather system will move into Montana from the Great
Basin bringing mainly snow from south to north, 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 Sunday afternoon
through Sunday night for most areas...but still linger in and near
the mountains. Low cigs will also persist. Some patchy fog is
also possible at times tonight into Sunday morning for areas
without precip...mainly from KHVR to KLWT. 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


/ISSUED 308 PM MDT Sat Mar 17 2018/
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


GTF  25  33  20  39 /  70  70  20  20
CTB  24  31  17  34 /  60  60  30  20
HLN  26  38  24  41 /  50  50  20  20
BZN  24  38  20  40 /  20  20  20  20
WEY  16  30  13  31 /  30  20  30  30
DLN  24  35  16  36 /  20  30  30  20
HVR  26  32  16  30 /  60  50  20  20
LWT  21  32  19  37 /  20  10  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 above 5000 feet
for Jefferson.

Winter Weather Advisory until noon MDT Sunday Cascade...Chouteau.

Winter Weather Advisory until noon MDT Sunday Central and
Southern Lewis and Clark...Northern Rocky Mountain Front...
Southern Rocky Mountain Front.


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