813 
FXUS65 KTFX 131745
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
1045 AM MST Sun Dec 13 2020

Updated Aviation Discussion

.UPDATE...

Clouds continue to roll into the area this morning as a Pacific
weather system begins to nudge into the area. This will keep us on
the cool side today, with high temperatures still expected to be
in the teens along the Hi-Line and upper 20s across the Southern
Valleys. POPs were nudged up a bit for tonight and tomorrow with
this update, but snowfall totals were largely unchanged.

Ludwig

&&

.SYNOPSIS...
Colder air has moved into the far northern sections of North
Central MT today, with afternoon highs only expected in the single
digits for some areas north of Highway 2 today. Light snow over
Central MT will diminish this morning. Otherwise, another round of
snow will move into Southwest and Central MT by this evening, with
snow continuing through the Monday morning commute. Below normal
temperatures early this week, will give way to above normal
temperatures by late in the week across much of the region.

&&


.AVIATION...
1045 AM MST Sun Dec 13 2020 (13/18Z TAF period)

Moist low-level easterly flow over the N-central MT plains will 
maintain low clouds along the east slopes of the Rockies into this 
afternoon with IFR ceilings at KGTF and KCTB slowly improving. VFR 
conditions prevail elsewhere across the area with increasing and 
thickening clouds as a Pacific weather system moves in from the 
west. A few snow showers move into SW MT this afternoon with 
mountain obscuration increasing as cloud bases lower further. A 
period of IFR/MVFR conditions is expected at most central and SW MT 
terminals later tonight through Monday morning as an area of more 
widespread light snow moves across the area in association with the 
Pacific weather system. Expect improving conditions by Monday 
afternoon as the system exits the area with some snow showers 
lingering through the day across far SW MT. Hoenisch  

Refer to weather.gov/zlc for more detailed regional aviation 
weather and hazard information.

&&

.PREV DISCUSSION...
/ISSUED 359 AM MST Sun Dec 13 2020/
Today through Monday...Light snow is slowly coming to an end over
North Central MT this morning. Any new snow accumulations before
10 AM today will generally be less than a quarter of an inch. Cold
air continues to push southward into the northern portions of
North Central MT. Afternoon highs today will only be in the single
digits for some areas north of Highway 2, mostly in Hill/Blaine
counties. Otherwise, below normal temperatures can be expected
elsewhere across the region today. Light snow will begin to
develop by late afternoon over far Southwest MT and then gradually
spread northeastward up into Central MT by late evening. The light
snow will continue through Monday morning, affecting the Monday
morning commute. Snow accumulations of 1 to 2 inches are possible
at lower elevations of Southwest and Central MT, with 3 to 5 
inches in the mountains. Little/no snowfall is expected from this
event for areas mostly north of a line from Choteau to Fort Benton.
An SPS was issued to highlight this event. A winter weather 
advisory could be issued later today for portions of Southwest and
Central MT after further coordination with neighboring NWS 
offices. Warmer air starts to move back into the region after the 
snowfall exits on Monday afternoon.

Tuesday through Friday...Generally mostly dry conditions are
expected for the middle portion of the work week, but a few
passing, mostly mountain snow showers can not be ruled out.
Overall temperatures will begin a slow warming trend starting on
Tuesday, with generally above normal temperatures expected for the
remainder of the week. There is the potential for winds to
approach high wind criteria Tuesday afternoon/night over North
Central MT. However, at this time, it looks too marginal for any 
high wind highlights.

Saturday and Sunday...A stronger storm system is expected to move
into western Montana next weekend. At this time the best chances
for precipitation in our area look to be over the western 
mountains and Southwest MT. Temperatures will be warm enough that 
some rain could mix in with any snow showers that do develop over
North Central MT, especially during the daylight hours. 
Additionally there is the potential for some strong winds Saturday
afternoon into Sunday along the front range of the Rockies. We 
will have to monitor the stronger wind potential for possible high
wind highlights. Brusda

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  21  14  34  21 /  50  50  40   0 
CTB  16   9  32  19 /  30  20   0   0 
HLN  28  18  35  19 /  10  80  60   0 
BZN  27  14  32  11 /  10  80  70  10 
WYS  19   6  23   1 /  40  70  60  10 
DLN  28  15  31  11 /  50  80  70   0 
HVR  16   7  25  13 /  10  10  10   0 
LWT  24  12  31  16 /  30  50  50   0 

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

http://www.weather.gov/greatfalls