579 
FXUS65 KTFX 030654
AFDTFX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
1145 PM MST Sun Mar 2 2014

.UPDATE...
1145 PM Update...With heavy snow developing in the Many Glacier 
area...have upgraded the northern Rocky Mountain Front to a winter 
storm warning through 11 am Monday. The rest of the forecast is on 
track. Brusda

930 PM Update...Upper air sounding and surface observations reveal 
that the cold airmass has eroded from above to around 6000 ft MSL 
over north-central MT and down to around 5000 ft MSL over SW MT. 
Temperatures above the strong inversion at the top of the cold 
airmass are running in the 20s and 30s at many mountain locations, 
while the valleys from Helena south through Bozeman and Dillon 
remain in the single digits and teens above zero and temperatures 
across the north central MT plains remain from around zero to 10 
below zero. Have adjusted min temps for tonight down to near current 
values across most lower elevation locations for tonight. Surface 
pressure field is not supportive of any large scale downslope 
effects through tonight as low pressure remains west of the divide 
with weakening high pressure off to the north and east, so am not 
anticipating a dramatic warm-up at lower elevations tonight where 
temperatures will likely remain steady or rise slowly through most 
of tonight. Shortwave energy currently seen in satellite imagery 
moving into the Pacific NW will likely be the main mechanism to 
scour out the cold low level airmass late tonight through Monday 
morning. Moist west flow aloft will continue to produce snow over 
the Mtns tonight with an area of light snow also continuing over 
central and eastern portions of north-central MT where the moist 
flow is lifted over a deeper cold airmass. This area of snow will 
remain primarily north and east of a line from Cut Bank to Great 
Falls to Lewistown, where accumulations of generally around an inch 
are expected ,while 1 to 3 inches is likely over Hill and Blaine 
counties where snow will persist the longest. Hoenisch

&&

.AVIATION...
UPDATED 0540Z.
Forecast will remain relatively unchanged overnight as Pacific 
moisture continue to overrun the cold airmass in place over the 
plains of North Central Montana. Areas of light snow and low 
ceilings will cause MVFR conditions at times. However, warm air will 
gradually push through the forecast area by 18Z with improvements in 
ceiling expected region wide as gusty westerly winds develop along 
the east slopes of the Rocky Mountains. Another disturbance moves 
through the forecast area after 00Z Tuesday bringing lower clouds 
and scattered showers. mpj

&&

.PREV DISCUSSION...
/ISSUED 450 PM MST Sun Mar 2 2014/
This Afternoon through Tuesday Evening...Broad moisture plume our 
ahead of a shortwave trof currently approaching the WA/OR coast is 
spreading good amount of cloud cover across central and southwest 
MT, but generating little in the way of precipitation.  Most of the 
snow is falling along the Rocky Mtn Front and immediate adjacent 
foothills, with only very isolated snowshowers occurring east of 
Great Falls and along eastern portions of the Hiline.  With drying 
westerly flow aloft becoming more established this evening and 
tomorrow, the chances for impact-producing snowfall over the central 
plains are decreasing, so have cancelled the winter weather advisory 
for eastern Glacier County southeastward through Cascade County to 
Fergus County.  The northern/southern Rocky Mtn Front areas remain 
in the advisory until early Mon morning, with an additional 1-3 
inches of accumulation likely.  Westerly flow should continue 
through Tues with a few minor disturbances coming through the flow 
to give a slight chance of occasional light snow east of the Divide 
both days. Best news is that the Chinook winds will steadily erode 
the low-level cold airmass that brought teens and 20s below zero 
this weekend. Latest short-term forecast models bumped high temps 
tomorrow into the mid- and upper 30s along/south of a Choteau/Great 
Falls/Lewistown line, with 20s for central/eastern parts of the 
Hiline. The warm-up continues on Tues with highs increasing to the 
upper 30s to mid 40s for central and southwest locations and low- to 
mid 30s for the Hiline. 
Waranauskas

Tuesday night through Sunday...Current medium range forecast 
continues to look on track. A closed upper low moves across northern 
Canada Wednesday while a short wave upper ridge builds over the 
Pacific Northwest. The resulting northwest flow aloft is very moist 
and unstable and results in scattered snow for the western and 
southwest mountains as well as isolated rain or snow showers over 
the plains. The ridge gets knocked down on Thursday as an upper trof 
moves onshore in the Pacific Northwest. The resulting mild westerly 
flow aloft will bring a plume of Pacific moisture with it and 
scattered rain and snow showers will have greater areal coverage. An 
upper ridge amplifies over the west coast on Friday, placing the 
area again, under a somewhat unstable northwest flow aloft and the 
possibility for isolated showers. Dry and mild conditions return on 
the weekend as the upper ridge builds into western Montana Saturday 
and then moves across the Continental Divide Sunday. A lee side trof 
developing Friday night and continuing into Saturday will provide 
breezy conditions. Afternoon temperatures will be above seasonal 
averages.

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  -4  38  23  44 /  40  20  20  20 
CTB  -9  31  14  40 /  50  20  20  20 
HLN   3  40  25  42 /  40  30  20  20 
BZN   6  41  27  43 /  30  20  20  20 
WEY  26  40  28  40 /  80  70  50  50 
DLN  14  40  23  39 /  30  20  20  20 
HVR  -4  22   7  34 /  90  40  20  20 
LWT  -2  39  24  41 /  50  30  20  20 

&&

.TFX WATCHES/WARNINGS/ADVISORIES...

WINTER STORM WARNING...until 11 AM MST Monday Northern Rocky 
Mountain Front.

WINTER WEATHER ADVISORY until 5 AM MST Monday Southern Rocky 
Mountain Front.

&&

$$

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