Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 161451

Area Forecast Discussion
National Weather Service Great Falls MT
851 AM MDT Fri Mar 16 2018



The main focus this morning is the widespread dense freezing fog
across Northern and Central Montana. Decided to issue a Freezing
Fog Advisory for Hill, Blaine and Liberty Counties and extend all
areas to noon. Some reports include areas of <1/8mi visibilities,
with some light accumulations causing black ice issues. The
duration of the freezing fog this morning is still in question, as
some locations may remain locked in fog throughout the afternoon.
Will plan on evaluating future conditions later for any
possibility of advisory extensions. Otherwise, most of the area
remains quiet. Light snow, and perhaps mixed precipitation will
increase across Fergus and Blaine Counties later this morning and
through the afternoon. No real changes were necessary in these
locations. Will also evaluate southwestern areas later this
morning/early afternoon on the potential for convective snow
shower development beginning early Saturday, with the possibility
of highlights to follow. KLG



Winter weather won`t give up just yet across the area, with
multiple opportunities for snow and even some mixed precipitation
for parts of the area through the weekend. Fog will continue to
plague parts of the area as well, especially Central Montana.


Updated 1108Z.

Low clouds/fog to impact Central MT through this morning with
LIFR/VLIFR conditions at times.

Areas of FZFG, dense at times, will continue to plague Central MT
terminals with significant reductions in VIS/CIGs, down to VLIFR at
times. VIS should improve some later this morning, but low
clouds/mtn obscurations may linger all the way into this afternoon.
Mid level clouds should keep any fog at bay across SW MT. Later
today/this evening, a band of SN/RA will move NW, impacting
KLWT/KHVR with reduced VIS, especially KHVR. In the wake of the
precip, some -FZDZ cannot be ruled out, especially in the vicinity
of KHVR, with some icing potential. MARTIN


Updated 400 AM.

The flood advisory will continue for portions of Southwest MT, as
impacts from minor flooding continue to be reported via emergency

After a brief break this morning, precipitation will once again
develop across parts of the area through the weekend.
Precipitation will be a mix of liquid and frozen and temperatures
will be near to slightly below normal. Given all of this,
widespread flooding is not anticipated at this time. However,
continued snowmelt each afternoon will likely lead to some water-
logged fields and water-covered roads in some of the more flood-
prone areas. In addition, travel will continue to be more
difficult on unpaved roads and alleys. MARTIN


/ISSUED 508 AM MDT Fri Mar 16 2018/

Today through Sunday night...A dynamic, unsettled, and somewhat
complex pattern exists across the western half of the Nation this
morning. A spring storm system continues to take shape over the
Great Plains at this time, with an upper level low situated over
western Kansas. North of this low, a well defined 70-90kt jet max
was located over Montana, providing large scale lift from Nebraska
north to Montana. As this jet max translates NW into southern
Canada, it will combine with an area of low/mid level
frontogenesis (ie. focused lift), leading to a band of heavier
precipitation. Global and hi-res models have trended west with
this band and as such, the forecast reflects this change. This
mainly impacts areas from Lewistown to Havre. For now, the
westward shift leads to an increase in snow amounts, especially
over Blaine County. For this reason, it was decided to issue a
Winter Weather Advisory for that county. If the westward trend
continues, it is possible that Fergus and Hill Counties may need
to be added later. Of note, temperatures across Fergus County look
to be near/above freezing which may tend to limit snowfall
amounts/impacts. As the jet pulls away, drier air aloft will move
into the area as an upper low develops over Alberta. With
lingering low level moisture and possibly some weak low-level
lift, areas of freezing drizzle may develop along the Hi-line from
Cut Bank east, although QPF amounts look low, with only a light
glaze of ice expected.

Attention then turns to the next shortwave that is forecast to move
through parts of the area SAT/SUN. While there remains some
uncertainty in the evolution, the general idea is a mid/upper level
low will push east through southern Montana with a deformation band
of heavier precip developing later Saturday into Saturday night. It
should be noted that the exact track of the low will be key in where
the heaviest precip rates occur. For now, it appears this axis will
lie from Wisdom/Butte NE through Helena/Great Falls, and possibly as
far north as Havre. But, again, the exact location is subject to
change. Forecast soundings suggest some mixed precip potential
initially. However, dynamic cooling with the areas of heavier precip
should allow mostly snow by Saturday night. Outside of where the
heaviest precip occurs, precip type may be more problematic due to
the more showery nature of the precip. For now, we will hold off on
issuing any winter weather products for this event, but stay tuned.
In general, 1-4 inches of snow is expected in that above-mentioned
axis of heavier precip. A light glaze of ice cannot be ruled out as

The only other real issue will be fog. Dense, freezing fog will
continue to plague parts of Central Montana through this morning and
we will continue to cover this impact with SPS` and Freezing Fog
Advisories. MARTIN

Monday through Thursday...main forecast concerns through the long
term will be a continued active/unsettled pattern, with a brief
(36hr) break from precipitation chances Tuesday night-Wednesday.

Very, very messy upper level pattern to begin the long term, with
the main large H500 closed low over the Northwestern CONUS
dissolving into the morning hours on Monday into multiple shortwaves
chaotically scattered across the Western CONUS/Canada. One such
positively orientated shortwave over Alberta/Saskatchewan will slide
across North Central and Southwestern Montana Monday
afternoon/night. This will bring additional chances for generally
light precipitation to the region, most notably across Southwestern
Montana and the mountains of Central Montana. A second shortwave
will then be quick on the heels of the first, diving southeast from
Northern British Columbia/Alberta and across the Hi-Line of North
Central Montana Tuesday evening and into the early morning hours of
Wednesday. This second wave while apparent at H500, is moisture
starved and negligible at lower levels, and is only expected to
bring some increasing high clouds to North Central Montana. H500
ridge begins to amplify along the US Pacific Coast Tuesday night,
moving east across the Intermountain West/Northern Rockies for the
day on Wednesday. 1000-500mb thickness values are currently prog to
climb to around 540-550dam by Wednesday afternoon/early evening,
which should support daytime highs in the 40s to near 50 degrees.
Temperatures will warm further for the day on Thursday as increasing
warm air advection ahead of the next large H500 trough overspreads
the region. - Moldan


GTF  37  26  34  24 /  10  20  40  60
CTB  33  24  29  18 /  10  30  30  40
HLN  42  22  35  25 /  20  10  50  60
BZN  42  23  39  20 /  10   0  40  40
WEY  33  18  36  14 /  20  50  70  50
DLN  39  22  33  22 /  10  20  60  60
HVR  33  28  29  19 /  30  80  20  40
LWT  36  21  35  23 /  60  50  10  40



Freezing Fog Advisory until noon MDT today Blaine...Cascade...
Chouteau...Eastern Glacier...Eastern Pondera...Eastern Teton...
Hill...Liberty...Northern Rocky Mountain Front...Southern Rocky
Mountain Front...Toole.

Winter Weather Advisory from 3 PM this afternoon to midnight MDT
tonight Blaine.

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


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