572
FXUS65 KTFX 280640
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
1240 AM MDT Sun Apr 28 2024

.Aviation Section Updated...

.SYNOPSIS...

Rain and mountain snow diminish later this evening, giving way to
drier and breezy conditions for Sunday. The unsettled weather
pattern resumes early next week with potentially colder and wetter
systems moving through the Northern Rockies, especially towards
the end of the work week.

&&

.UPDATE...

Light precipitation persists across portions of Central and
North- central Montana east of I-15, with additional, perhaps
heavier precipitation developing along the MT-ID border. The
latest forecast does an excellent job showcasing PoPs associated
with this precipitation, which is forecast to begin diminishing
early tomorrow morning. Given this, opted to only amend the hourly
temperatures with the latest observations as the remainder of the
forecast continues to describe the situation well. No further
amendments were needed at this time. - Pierce

&&

.AVIATION...
1230 AM MDT Sun Apr 28 2024 (28/06Z TAF Period)

Light rain is slowly tapering off and moving towards the east
allowing all terminals to return to VFR. Most terminals will
maintain VFR through the remainder of the TAF period with the
exception of KEKS and KBZN which will experiences periods of MVFR
conditions along with light rain showers through Sunday evening.
Mountain obscuration will be a concern across southwest Montana
through the entire TAF period. Along central and north-central
Montana breezy conditions are expected after 28/09Z for KCTB and
after 28/14Z for all other terminals in central/north-central
Montana.

-thor

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

&&

.PREV DISCUSSION...
/ISSUED 540 PM MDT Sat Apr 27 2024/

Moisture and shortwave energy within a southwesterly flow aloft
has provided a cool and wet day for nearly all locations except
the far eastern portions of Central/North-central Montana. The
rainfall and abundant cloud cover have generally kept temperatures
about 5 to 10 degrees lower than earlier forecasts, so the
hourlies were adjusted through this evening to match current
expectations of clouds and rain persisting for the remainder of
the day. All winter weather highlights have been canned with
diurnal heating and diminishing snowfall limiting winter weather
impacts over the higher terrain of the southwest. The shortwave
responsible for the wet conditions exits the region tonight with
rain and mountain snow ending in a west to east fashion tonight.
Patchy overnight fog can`t be ruled out for areas receiving
precipitation this afternoon and evening, but lingering cloud
cover and a shift to southwesterly winds over the the plains
should limit both coverage and impacts. Drier and breezier weather
is expected on Sunday, with the strongest winds approaching the
40 to 55 mph range along the Rocky Mountain Front.

Most ensembles feature a split trough moving onto the Pacific
Northwest coast and impacting the Northern Rockies Monday through
Wednesday. On Monday, precipitation will initially come in the
form of lower elevation showers/isolated thunderstorms and
mountain snow, mostly along the Continental Divide, while large
scale ascent and moisture stream ahead of the approaching trough.
This system will have a better supply of colder air than previous
ones with H700 temperatures running around -10 to -15C behind the
cold front. this will result in snow levels falling to the valley
floors Monday night into Tuesday morning and at least a brief
period of accumulating snow over higher terrain. This quick
hitting area of snow looks to bring the best chance for 4 + inches
of snow to the Gallatin/Madison ranges. Other mountain areas,
including the Central ranges and the mountains along the
Continental Divide are currently looking at over a 50% chance for
2 inches of snow for the same period. Winter weather highlights
may be needed in spots, especially if timing shifts later from
Monday afternoon/evening to the overnight hours. This system will
also bring periods of gusty winds, initially to Southwest Montana
on Monday followed by the Rocky Mountain Front and the plains
Monday night into Tuesday. Although wind exceedence probabilities
support gusts over 40 mph, mostly along the Rocky Mountain Front
and the north/south oriented southwest valleys, probabilities for
gusts above 55 mph are running well under 50% for most locations.

The region will remain under the influence of the broad trough
through Wednesday. Some ensembles featuring the northern closed
circulation crossing the Continental Divide on Tuesday before
slowing down and remaining over eastern Montana through early
Thursday while the southern circulation moves southeastward along
Montana/Idaho border. This solution favors overall colder and
wetter conditions, particularly for the northerly upslope areas of
Central/North-central Montana, where rainfall exceedence
probabilities for a half inch of liquid precipitation are now
running around 30%. This colder solution also has H700
temperatures around -10C, cold enough to support snowfall at all
elevations, at least at night. At the very least, there is an
expectation for wet and unsettled condtions with below average
temperatures Monday night through Wednesday. Things warm and dry
out some on Thursday, but the parade of Pacific weather systems
continue heading into the next weekend favoring cooler and wetter
conditions overall. - RCG

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  37  60  39  55 / 100   0   0  60
CTB  33  57  36  54 /  80   0   0  10
HLN  38  62  38  55 /  80  10  10  80
BZN  36  59  35  57 /  90  40  30  90
WYS  33  49  28  47 /  90  60  20  90
DLN  34  56  35  54 /  70  10  10  80
HVR  41  66  38  62 /  90  10   0  30
LWT  37  58  36  56 /  80  10  20  90

&&

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

$$

http://www.weather.gov/greatfalls