Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 241756
AFDTFX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
1155 AM MDT Tue Mar 24 2015

Updated Aviation Section.

.UPDATE...

A cold front remains stalled through North Central Montana along a
line from near Choteau to Fort Benton to Hays. Low stratus covers
much of the area north of this front...with areas of dense freezing
fog. The freezing fog advisory has been extended through 11 am.
Also, high temps were lowered a few degrees in these areas. Downslope
winds have cleared skies right along the Rocky Mountain Front...with
partly sunny skies extending through central Montana. Clouds have
advanced into southwest Montana ahead of the next shortwave. The
forecast remains on track for valley rain and mountain snow to
develop over the southwest through this afternoon and evening. Nutter

&&

.AVIATION...
UPDATED 1755Z.
A cold front has stalled in North-central MT, providing IFR overcast
at KCTB/KHVR along with some areas of fog. These conditions will
prevail through the evening. The front remains north of KGTF, but
winds have become VRB and may switch to the north this afternoon. An
upper level disturbance is entering SW MT. This will lower CIGS and
cause periods of light rain or snow for KHLN/KBZN overnight.
Confidence is lower for precipitatation at KGFT/KLWT. MVFR
conditions will develop due to snow, low clouds, and visibilities.
Nutter

&&

.PREV DISCUSSION...
/ISSUED 547 AM MDT Tue Mar 24 2015/

Today through Thursday...The band of snow showers expected to move
into the northern Rocky Mountain Front area overnight has weakened
and will likely only bring flurries to that area through this
morning. Have therefore cancelled the Winter Weather Advisory for
that area. However, snow may still move into the mountains this
afternoon, so will monitor the situation for possibly another
advisory. Otherwise, a shortwave trough is still on track to move
east through Montana today. However, the focus for the stronger
jet dynamics is forecast to move over southwest Montana this
afternoon and evening. Moisture also appears to be substantial
enough that light to moderate snow is expected to fall at and
above mountain pass level there. Have therefore issued a Winter
Weather Advisory for areas above 6000 feet south of Great Falls to
the Idaho border, which runs from 9 am this morning to midnight
tonight. Mountain passes could receive 1 to 3 inches of wet
slushy snow, while 3 to 6 inches are likely above mountain passes.
Valleys will mostly see rain, but snow may mix in with the rain at
times, for little if any accumulation. Gusty west winds will also
accompany the shortwave south of Interstate 90, which may reduce
visibility in localized blowing snow. Over north central Montana,
light accumulating snow is likely in the mountains, but only
scattered rain showers are expected over the plains, mainly
southwest of a Cut Bank to Lewistown line. Showers will decrease
overnight as the shortwave exits the area. An upper level ridge of
high pressure will then gradually move into the area from the
west. The resulting northwesterly flow aloft will keep a chance of
mainly mountain showers over the area. A weak Canadian cold front
will shift winds more northerly over north central and central
Montana today, which will help cool temperatures to near normal.
However, as the upper level ridge builds into the area,
temperatures will warm mostly into the mid 50s to mid 60s by
Thursday, as breezy westerly winds return to most of the area.
Coulston

Thursday night through Tuesday night...A high pressure ridge will
build over the Rockies Thursday night and Friday and the air mass
will continue to warm and dry. A shortwave will move over the
West Coast Friday night and approach the Rockies by morning. This
will bring a chance of showers over the Rockies. The air mass
could become a bit unstable ahead of this shortwave and a chance
of thunderstorms could develop as the system moves across Central
Montana. Despite the chance of thunderstorms, precipitation
associated with this system will generally be light. However,
this system will strengthen low pressure over
Alberta/Saskatchewan. This will result in strong surface winds
across the Rockies and adjacent plains which will spread east
during the day. Heights will build aloft again Saturday night and
the air mass will also trend warmer and drier. A weak disturbance
will move underneath the ridge Sunday and bring a chance of
showers to Southwest Montana. The air mass could become slightly
unstable Sunday afternoon and thunderstorms are not out of the
picture. High pressure aloft will be in place again Monday but
another shortwave will move through the Pacific Northwest Monday
night. Showers will develop over the Rockies ahead of this
shortwave and spread east Tuesday. A cold front associated with
this shortwave will bring much cooler temperatures into to the
region by late Tuesday. Zelzer

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  50  28  52  36 /  40  40  20  20
CTB  44  25  51  34 /  40  40  10  10
HLN  49  30  54  38 /  70  60  20  20
BZN  47  26  52  31 /  80  60  30  20
WEY  41  17  44  22 /  80  60  30  20
DLN  46  26  51  33 /  80  50  10  10
HVR  47  23  55  28 /  10  10  20  10
LWT  49  25  50  32 /  40  40  30  20

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY until Midnight MDT tonight FOR
ELEVATIONS ABOVE 6000 FEET FOR Beaverhead...Broadwater...
Cascade...Central and Southern Lewis and Clark...Gallatin...
Jefferson...Judith Basin...Madison...Meagher.

FREEZING FOG ADVISORY until 11 AM MDT this morning Eastern
Glacier...Eastern Pondera...Liberty...Toole.

&&

$$

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