892
FXUS65 KTFX 231702
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
1102 AM MDT Mon Sep 23 2024

...Aviation Section Updated...

.SYNOPSIS...

A disturbance passing over North Central and Southwest Montana
today will cool temperatures a few degrees and bring breezy
conditions, but there is only a slight chance for even mountain
precipitation. High pressure aloft will then bring warmer and
drier conditions through Friday, with Wednesday likely being the
warmest day.

&&

.Update...

No morning update is needed or planned as the on-going forecast is
handling current conditions well. Breezy southwest to northwest
winds will once again be experienced today, but these speeds and
gusts will be lower than what was observed yesterday. Otherwise,
high temperatures will be within several degrees of yesterday`s
highs, with decreasing clouds towards the late afternoon/early
evening hours. - Moldan

&&

.AVIATION...
23/18Z TAF Period

The primary concern today will be for breezy winds at times out of
the west to northwest, primarily across the plains. A few instances
of mountain wave turbulence will be around, but are not forecast to
be widespread nor strong. Otherwise, VFR conditions prevail as cloud
bases lift and eventually diminish through the afternoon and early
evening. A brief instance of fog cannot be ruled out around daybreak
tomorrow in high-elevation Southwest Montana valleys. -AM

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

&&

.PREV DISCUSSION...
/ISSUED 543 AM MDT Mon Sep 23 2024/

Today through Tonight... A weak disturbance in the northwest flow
aloft will move clouds over North Central, Central, and Southwest
Montana today. A few light mountain showers are possible, but
breezy westerly downslope winds behind a weak frontal passage will
likely keep any showers from reaching the ground. Winds will
generally have a 30 to 40 percent chance of exceeding 30 mph at
times over the plains, but the chance for gusts 40 mph or greater
increases to over 60% on the Rocky Mountain Front. The frontal
passage will also cool temperatures a few degrees over yesterday,
but they will remain slightly above normal.

Tuesday through Wednesday... An unseasonably strong high pressure
ridge is forecast to move east into the Rocky Mountain region for
Tuesday, then an approaching Pacific low pressure trough will
shift the ridge axis more so over the northern Great Plains on
Wednesday. This should keep the forecast area dry with significant
warming, with Wednesday likely being the warmest day of the week.
The current NBM has forecast highs on Wednesday well into the 80s
for lower elevations, but there are areas along the Missouri
River from Great Falls east that have at least a 20 percent chance
of exceeding 90 degrees. However, the shift in the ridge axis
will put much of the area under an increasing southwesterly flow
aloft, and the warm air mass will aid in mixing those winds down
to the surface. Areas along and west of the Interstate 15 corridor
on the plains and through north-south oriented valleys will
generally have a 30 to 50 percent probability of gusts exceeding
30 mph at times on Wednesday. This, combined with temperatures up
to 20 degrees above normal and afternoon humidity falling below
30 percent, could elevate fire weather conditions.

Thursday through Friday... The Pacific trough will weaken as it
moves east across the area Thursday into Friday, but it will be
strong enough to break down the high pressure ridge and move a
weak cold front through the area. The breakdown of the ridge will
put the forecast area under a stronger westerly flow aloft, and
these winds will mix down to the surface at times in the wake of
the cold front; much of the area will have at least a 30 percent
probability of gusts exceeding 30 mph, but the Rocky Mountain
Front will have at least a 30 percent probability of 40+ mph
gusts. Although temperatures will cool down a bit closer to
seasonal averages, moisture will be somewhat lacking, so humidity
will remain on the low side, continuing fire weather concerns.
The downsloping winds will limit any potential for precipitation
to the mountains of the Rocky Mountain Front.

Saturday through next Monday... The NBM is showing that another
low pressure trough from the Pacific is forecast to approach and
move through the area this weekend into early next week,
potentially bringing more unsettled weather and cooler than normal
temperatures. However, ensemble forecast model clusters continue
to be in disagreement between this scenario and one with a broad
high pressure ridge that would favor a less cool and unsettled
pattern. As a result, confidence is only moderate in the forecast
for this time period for now. -Coulston

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  74  50  83  54 /  10   0   0   0
CTB  71  49  82  49 /  10   0   0   0
HLN  75  49  82  53 /  10   0   0   0
BZN  73  43  80  46 /  10   0   0   0
WYS  64  32  72  35 /   0  10   0   0
DLN  69  42  77  45 /   0   0   0   0
HVR  73  50  82  51 /  10  10   0   0
LWT  68  46  78  52 /  10  10   0   0

&&

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

$$

http://www.weather.gov/greatfalls