Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 310554
AFDTFX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
1055 PM MST Fri Jan 30 2015

.UPDATE...

Satellite imagery shows mainly clear skies across the region this
evening with the next upper level shortwave to impact the area seen
moving into SE BC. Weak low pressure trough exists at the surface
to the east of the Rockies with observations upstream in AB
indicating the frontal boundary expected to move south across the
border late tonight now in between Calgary and Lethbridge. This
reinforces the expected timing of the frontal passage across the
border around midnight and into central MT by Saturday morning.
Precipitation lags behind to the north and is just beginning in
Calgary, also supporting current forecast of snow developing and
spreading south across the region Saturday morning/mid-day with
the arrival of the mid level shortwave and upper level jet.
Current forecast appears to be in good shape with no updates
planned this evening. Hoenisch

&&

.AVIATION...
UPDATED 0555Z.
An upper level shortwave will move through the northwest flow aloft
and cross the Rockies Saturday morning. An associated cold front
will cross the Canadian border around 10z Saturday. Gusty north
winds and IFR conditions are likely as this front moves south
through Central Montana. Widespread MVFR conditions, and a chance of
IFR conditions, will continue into Saturday evening.

&&

.PREV DISCUSSION...
/ISSUED 230 PM MST Fri Jan 30 2015/

Tonight through Sunday...Clear and mild conditions prevail this
evening with an upper level split flow over the region. A
low-amplitude shortwave trof presently over British Columbia will
move through central Montana on Saturday. The surface cold front
associated with this feature will cross the International border
around 09Z. Synoptic-scale dynamical support with low-level upslope
flow will support snowfall across North Central Montana. Froude
numbers support mid-slope snow accumulation based on local office
research. Moisture is limited, and the system will move quickly.
Therefore, expected snow totals are 1-3 inches over the plains with
2-5 inches over the central mountains. The NAM-12 suggests banding
possible on the north-facing aspects of the Little Belt and Highwood
Mountains. A winter weather advisory has been issued to cover
travel impacts associated with this snowfall. Snow ends early
Sunday. The next wave approaches from the west late Sunday with
increasing PoPS over northern portions of the Continental Divide.
Nutter

Sunday night through Friday...Shortwave energy in a moist
northwesterly flow aloft will bring a continuing chance for light
rain and snow across the forecast area Sunday night and Monday. More
widespread snow is expected over the western mountains but
accumulations amounts do not look overly impressive at this time. By
Monday night, however, models are in good agreement pushing another
batch of cold Canadian air into central Montana along with periods
of snow. This system will continue to move southward through the
state with a band of precipitation gradually moving into southwest
Montana by Tuesday night. For the remainder of the week, models are
in relatively good agreement in building an upper level ridge over
the northern Rocky Mountains. Temperatures are expected to warm back
toward seasonal averages by Thursday with highs possibly climbing
well above average by Friday. Breezy and mostly dry conditions will
likely prevail at lower elevations with a chance for precipitation
expected to persist over the western mountains as flow aloft
squeezes out any moisture due to orographic lift. mpj

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  25  28   8  34 /  10  90  30  10
CTB  21  23   4  28 /  20  70  20  10
HLN  19  31  11  34 /   0  50  20  10
BZN  14  36  11  32 /   0  10  20  10
WEY   7  34   7  27 /   0  10  20  20
DLN  19  44  18  39 /   0   0  10  10
HVR  21  26   3  23 /  30  90  30  10
LWT  21  27   6  30 /   0  80  40  10

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY from 5 AM Saturday to 5 AM MST Sunday
Blaine...Cascade...Chouteau...Fergus...Hill.

&&

$$

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