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000
FXUS65 KTFX 081745
AFDTFX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
1045 AM MST Sun Dec 8 2013

UPDATE TO AVIATION

.UPDATE...

Weak upper level disturbance on the tail end of a large upper
level low pressure system centered over the western Hudson Bay
will bring light snow showers and flurries through this afternoon,
lingering for SW Montana into early tonight. Accumulations will be
generally less than a half inch. Steady SW flow ahead of the
trough axis will lead to highs in the lower teens above zero in
favorable downslope areas of north-central Montana. Let the Winter
Weather Advisories and Wind Chill Advisories continue as the
inherited forecast was on track. One caveat is that wind chills
will moderate into the 5 to 15 below range this afternoon before
falling this evening. Sub-zero temperatures expected once again
tonight as surface to 500mb layer humidity decreases to near 50
percent leading to decreasing clouds. Uttech

&&

.AVIATION...
UPDATED 1745Z.
Upper level trough and associated surface cold front will continue
to move south through the area today. Areas of light snow and
blowing snow will cause IFR/MVFR ceilings as the front moves south
through Central Montana. Winds diminish around 00Z Monday with skies
temporarily clearing out behind the system. However, mid and high
level clouds increase after 06Z along with strong surface winds
creating a return to blowing snow and reduced visibilities as the
next weather system approaches. Suk

&&

.PREV DISCUSSION...
/ISSUED 445 AM MST Sun Dec 8 2013/
Today through Tuesday...A northerly wind flow aloft will reside
over the region for the next 3 days. As a result...upper level
disturbances will move southward through the region each
day...producing a chance for light snow across much of North
Central Montana during the day...and a light snow over Southwest
MT mostly during the afternoon and evening hours. In terms of snow
accumulations...generally less than a half inch of snowfall is
expected today and again on Monday. However...the upper level
disturbance looks a bit stronger on Tuesday...and a snowfall
accumulations of 1 to 2 inches looks possible over the Northern
Plains...with up to 3 inches in the mountains...(generally less
than an inch in the Southwest). Temperatures will warm today ahead
of the first disturbance...as Cut Bank is already above zero.
However...cold air will return tonight as temperatures fall below
zero in many areas. For Monday and Tuesday...the increased winds
will try to advect in some warmer air...with afternoon
temperatures climbing into the teens and 20s. Thus...with fairly
cold air in place today and tonight...the wind chill advisory has
been expanded to cover all areas through 10 am Monday.
Additionally...with gusty winds expected over Central and North
Central MT...a blowing snow advisory is now in effect until 5 PM
Monday...(but not for the Helena Valley). Brusda

Tuesday Night through Saturday...Medium range models continue to
agree that Montana will be underneath an unsettled northwest flow
aloft by midweek. The unsettled flow and occasional shortwave energy
remains favorable for slight chance to low chance pops across the
forecast area but there still does not appear to be any likelihood
for a large scale storm system. Also, shortwave ridging should move
over the region on Thursday for generally dry conditions with
temperatures near seasonable averages. However, unsettled flow
returns for Friday and Saturday before another weak transient ridge
improves conditions once again on Sunday. Overall, the entire medium
range period will see breezy westerly winds with temperatures that
are much milder than those seen over the last week. mpj

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  11  -7  19   7 /  60  10  50  20
CTB  11  -7  15   5 /  50  10  50  20
HLN   5  -7  16   8 /  50  10  30  20
BZN   2 -12  13   3 /  20  20  20  20
WEY   4 -21   5 -14 /  30  20  30  30
DLN   2 -13  11   1 /  20  10  20  10
HVR   5 -12  19   3 /  50  10  50  20
LWT   9  -7  21   8 /  40  20  50  20

&&

.TFX WATCHES/WARNINGS/ADVISORIES...

FLOOD ADVISORY until further notice for the Gallatin River near
Gallatin Gateway.

WIND CHILL ADVISORY until 10 AM MST Monday Beaverhead...Blaine...
Broadwater...Cascade...Central and Southern Lewis and Clark...
Chouteau...Eastern Glacier...Eastern Pondera...Eastern Teton...
Fergus...Gallatin...Hill...Jefferson...Judith Basin...Liberty...
Madison...Meagher...Northern Rocky Mountain Front...Southern Rocky
Mountain Front...Toole.

WINTER WEATHER ADVISORY until 5 PM MST Monday Central and
Southern Lewis and Clark.

WINTER WEATHER ADVISORY until 5 PM MST Monday Blaine...Cascade...
Chouteau...Eastern Glacier...Eastern Pondera...Eastern Teton...
Fergus...Hill...Judith Basin...Liberty...Northern Rocky Mountain
Front...Southern Rocky Mountain Front...Toole.

&&

$$


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