Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 260008
AFDTFX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
505 PM MST Thu Dec 25 2014

UPDATE TO AVIATION SECTION

.DISCUSSION...

Tonight through Saturday...Snow has ended for much of the forecast
area with the exception being the higher mountains across
southwest Montana. Less than an inch of additional snow
accumulation is expected in areas above pass level so have
canceled the Winter Weather Advisory. As skies clear tonight,
there may be some areas of fog that develop, but forecast
confidence is low on how widespread fog will be. Otherwise, quiet
conditions are expected overnight before another weaker system
moves over the forecast area on Friday. This system will be fast-
moving with little moisture associated with it, however an inch
or two of snow is possible in higher elevations with less than a
half-inch in the lower elevation plains and valleys. On Saturday,
mainly dry conditions are anticipated, however a stronger weather
system approaching from Alberta/Saskatchewan will begin impacting
areas along the Continental Divide by Saturday afternoon. MLV

Saturday Night through Thursday...This strong weather system will
bring a shortwave trough and associated cold front across the
US/Can border late Saturday night. This system will combine its
arctic air mass with a broad, but somewhat diffuse plume of
Pacific moisture, pushed into our region by a second weaker trof
along the PacNW Coast, to generate widespread snow for Sun through
Mon night. Initial estimates show that lower elevation locations
west and south of a Cut Bank-to- Great Falls- to- Lewistown line
could see snow totals of 3 to 7 inches, with mountain locations
possibly receiving 7-14 inches over the 48-hr period. Hiline
counties east of that line will only see totals of 1-3 inches.
Accompanying the snow will be a sharp drop in temperatures from
Sunday through early Wed, with low temps returning to the single
digits and teens below zero over the entire forecast area each
morning during the first half of the week. Forecast models are in
good agreement that the Canadian trof will push into the Great
Basin and northern California by Wed, allowing a strong high
pressure ridge in the eastern Pacific to build into the Northern
Rockies. This will keep our region under northerly flow aloft,
with a few weak disturbances embedded in the flow bringing
scattered areas of snow to eastern portions of the Hiline on
Thurs, while rest of the region remains dry. The arctic air mass
should erode by Wed, allowing high temps to rebound back into the
mid-upper 20s on Wed and Thurs. Waranauskas/MLV

&&

.AVIATION...
UPDATED 0005Z.
Lingering low MVFR clouds across the eastern portion of north
central Montana (including KHVR KLWT) will continue to move out of
the area through 04Z. Otherwise, clearing skies between 00Z and 06Z
will allow patchy fog to develop, but am not anticipating it to
significantly impact any of the terminals. A disturbance in the
northwesterly flow aloft will then spread mid level cloudiness into
north central and southwest Montana between 04Z and 10Z. Light snow
may also develop across the area, especially across north central
and central Montana, where occasional MVFR/high IFR conditions are
possible with the snow. Clouds and any snow that does develop will
move southeast out of the area beginning after 15Z along the
Canadian border.
Coulston

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  12  24  11  28 /  10  30   0  10
CTB  12  24  14  29 /  10  20   0  10
HLN  10  21   8  25 /  10  40  10  20
BZN   1  18  -3  20 /  20  20   0  20
WEY  -1  20  -5  18 /  30  10   0  40
DLN   6  23   4  24 /  20  20   0  10
HVR  16  27  15  31 /  10  30   0  10
LWT   9  23   8  29 /  10  20   0  10

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

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