<pre>573
FXUS65 KTFX 231750
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
1050 AM MST Mon Dec 23 2024

Aviation Section Updated.

.KEY MESSAGES...

- Light snow today mostly over the Rockies and Southwest MT.

- Another round of light snow Christmas Eve into Christmas Day
  mostly over Southwest MT.

- Windy periods through this weekend along the front range of the
  Rockies and adjacent Plains, but overall wind speeds should
  remain below warning criteria.

- Above normal temperatures will continue through the weekend.

- Potential for a more significant snowfall and colder
  temperatures starting next Monday.

&&

.UPDATE...
/Issued 1037 AM MST Mon Dec 23 2024/

Just a few minor tweaks to the existing forecast were made this
morning, mostly to temperatures due to warmer than forecast
overnight lows. Ludwig

&&

.DISCUSSION...
/Issued 1037 AM MST Mon Dec 23 2024/

 - Meteorological Overview:

An upper level disturbance is approaching MT from the west this
morning. This disturbance will move across MT during the day
today. A mix of rain/snow will accompany this disturbance. For
areas north of a line from about Cut Bank to Lewistown, downslope
winds should prevent much precipitation from occurring in these
areas. South of this line, scattered areas of rain/snow will occur
today, with the Rocky Mountain Front and Southwest MT having the
highest probabilities. There is also the potential for some
morning fog today in the Havre/Harlem areas. With increasing high
clouds aloft, widespread impacts should be limited in our CWA.

The flow aloft is rather brisk and the next upper level
disturbance arrives Tue night into Wed morning. Again, Southwest
MT is the most favored area for light snow, but the NAM model
does have a small piece of energy moving northeast through the
eastern portions of the CWA, affecting areas mostly east of a
line from Great Falls to Havre.

A series of upper level disturbances will move from west to east
across the CWA from Thu into Saturday. Again, light precipitation
is expected with each of these disturbances, with the mountain
areas having the highest probability of precip.

The westerly flow aloft will result in above normal temperatures
across the CWA for all of this week and into the weekend.

Windy periods will also occur as these disturbances move through.
Wind speeds are forecast to remain below warning criteria,
however wind speeds are very close to warning criteria on
Saturday.

The most significant weather impact over the next week might be
the storm system for next Monday. Both the GFS/EC prog this
storm. Some models have over 0.75 inches of liquid with this
system, resulting in 5 to 10 inches or more of snowfall in the
mountains. At lower elevations a 1 to 3 inch snowfall is the
early estimate.

 - Forecast Confidence & Scenarios:

The chances for a 2 inch snowfall today and again Tue night into
Wed is quite low. The highest chance is in the mountains of
Southwest MT, and that probability is generally less than 40
percent. At this time, special weather statements will likely be
used to handle messaging of these disturbances. Should snow
amounts or intensity increase a bit, there would be a potential
that a winter weather advisory might need to be issued.

In terms of high winds, the probability of wind gusts reaching
warning criteria is less than 30 percent most days, except
Saturday. On Saturday, there is a 65 percent chance wind gusts
could reach warning criteria in the Cut Bank area. A high wind
statement might be needed for a short time as we approach the
weekend.

For the storm system arriving next Monday, there is a 60 percent
of 4 inches or more of snow in the mountains over the Northern
Rocky Mountain Front and in the mountains around Big Sky and West
Yellowstone. At lower elevations there is a 20 percent chance that
the snowfall could exceed 2 inches. Overall, there is the
potential that winter statements might be needed by early next
week. Brusda

&&

.AVIATION...
23/18Z TAF Period

VFR conditions will prevail across all terminals during this TAF
period. There is a 30% chance for rain at the KBZN terminal between
23/21Z and 24/00Z. At the KEKS and KLWT terminals there is a 20%
chance for rain between 23/19Z and 24/00Z. During this TAF period
there will be wind gusts up to 25kts at the KEKS, KGTF, and KHVR
terminals. Winds at the KCTB terminal will gust up to 37 kts at the
KCTB terminal during this TAF period. There will be isolated
instances of low-level wind shear across North-central and
Southwestern Montana during this TAF period. There will also be
mountain wave turbulence periodically during this TAF period. During
the first 6 hours of this TAF period there will be periods of
mountain obscuration in Southwestern Montana. -IG

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

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  52  28  50  31 /  30   0   0  20
CTB  48  23  43  28 /  10   0   0   0
HLN  48  24  43  27 /  50   0  10  40
BZN  45  21  43  25 /  70  10   0  60
WYS  34  15  35  18 /  80  30  10  70
DLN  44  22  41  25 /  40   0  10  70
HVR  46  21  41  25 /  10   0   0  20
LWT  47  25  48  30 /  30   0   0  30

&&

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

$$
http://www.weather.gov/greatfalls</pre>