895 
FXUS65 KTFX 201621
AFDTFX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
921 AM MST Sun Jan 20 2013

.UPDATE...Cold Canadian air will continue to push into Montana
today. As feared, it appears that snow amounts are much lower than
models anticipated so have updated to lower pops and snow amounts
across much of the forecast area. have also updated forecast highs
to reflect the likelihood of temperatures falling during the day.
At this time it also appears that wind speeds may be lower than
anticipated and wind chill advisory criteria may not be met in
Blaine and Hill Counties. However, will leave the advisory going
in case winds pick up a bit this afternoon. mpj

&&

.AVIATION...
Updated 1155Z.
A cold front continues to move across North Central and Central 
Montana during the TAF period. Winds will continue to originate out 
of the north or north east. Clouds and visibility conditions will 
remain difficult for much of the morning hours. Conditions will 
generally improve around 15z through 20z Weak upslope flow will 
continue to promote low clouds and IFR/LIFR CIGS along with the 
possibility for light snow and fog though little snow accumulations 
are expected during this time frame.  At KBZN and KHLN conditions 
are expected to remain VFR. Suk

&&

.PREV DISCUSSION...
/ISSUED 455 AM MST Sun Jan 20 2013/

TODAY THROUGH TUESDAY...An upper level high pressure ridge will be 
in place over the West Coast with northwest flow aloft over the 
zones. At the surface, a cold front will be moving through the zones 
and temperatures behind the front will be much colder. Currently, 
pressure rises over Alberta are very strong and surface pressures 
are also 1045+ mb across northern Alberta. The main questions for 
today will be snow amounts and temps. The upper level support for 
this system is very weak and precipitation will be generated mainly 
by the low level upslope flow. Temperatures will be highly dependent 
upon the frontal positioning with very cold temps to the north and 
much more mild temps to the south. Low level moisture will spread 
through the north and central zones by this morning. Snow reports to 
the north have so far been scanty although Medicine Hat an Calgary 
have both reported snow. By midday today, the northwest zones will 
be drying. Most precip will likely occur along the frontal 
boundary--across the central zones--and best snow amounts will be 
over the higher terrain of this region. The upper level high 
pressure ridge will remain over the West coast through Monday and 
slowly move over the Pacific Northwest Tuesday. This will keep the 
zones underneath the northwest flow aloft. However, by Monday the 
ridge will be near the Idaho panhandle and the jet will be east of 
the zones so the airmass be trending warmer. The cold airmass moving 
into the area and breezy conditions could cause some low wind chills 
across the northeast zones and will continue the current wind chill 
advisory. Zelzer

Tuesday Night through Sunday...A large scale ridge axis begins to 
move over the Rocky Mountains and in to the area Wednesday. By the 
middle of the day Wednesday a fast moving shortwave trough will move 
across the area bringing a quick decrease in temperatures and windy 
conditions Wednesday Night and Thursday. Some precipitation is 
possible too although it should be limited to area along the high 
line and the elevated terrain. This unsettled system will be 
relatively short lived as the large scale ridge once again build 
back into the are bringing warmer than average temperatures into the 
area Friday and Saturday. Model solutions are in general agreement 
through the bulk of the long term...by Sunday models do have 
significant differences. It should be noted though that both models 
due have a large scale low pressure system off the pacific 
coast...with the European retrograding and cutting off the low...and 
giving us more days under the high pressure ridge...while the GFS 
continues to move it across the continent as a large scale trough. 
Will continue to see how subsequent model runs address this 
discrepancy.  Suk

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  23   8  35  27 /  40  10   0   0 
CTB  11  -3  35  19 /  20  10   0   0 
HLN  25  12  33  15 /  10   0   0   0 
BZN  26   9  32   8 /  10  10   0   0 
WEY  25   0  26  -6 /   0   0   0   0 
DLN  35  15  38  12 /  10   0   0   0 
HVR  10 -14  11   4 /  60  10  10  10 
LWT  16   2  30  20 /  70  10  10  10 

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
WIND CHILL ADVISORY until 6 PM MST this evening Blaine...Hill.

&&

$$

weather.gov/greatfalls