818
FXUS65 KTFX 041658
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
1058 AM MDT Sat May 4 2024

...Aviation Section Updated...

.SYNOPSIS...

Weak high pressure will keep North Central, Central, and Southwest
Montana dry and a bit warmer than normal through tonight with
gusty southeasterly winds. However, a Pacific weather system will
first bring an increasing chance for showers and thunderstorms to
the area on Sunday, then more widespread mountain snow and low
elevation rain with cooler than normal temperatures Monday through
Thursday. Warmer and drier conditions should then move in to end
the week.

&&

.UPDATE...

No major changes were made to the forecast on this quiet morning.
Expect clouds to be on the increase today, along with some breezy
areas across the plains. Ludwig

&&

.AVIATION...
1058 AM MDT Sat May 4 2024 (04/18Z TAF Period)

VFR conditions will prevail through much of the 0418/0518 TAF period
before lowering CIGS and increasing chances for precipitation bring
MVFR/low-VFR conditions to the terminals of Southwest Montana (i.e.
KWYS, KEKS, and KBZN) beyond 12z Sunday. Prior to 12z Sunday, mid-
to upper level cloudiness will begin to overspread the Northern
Rockies from southwest to northeast; however, mountain obscuration
will generally be confined to the Continental Divide. Otherwise,
easterly surface winds will begin to increase during the late
afternoon/early evening hours over the plains of Central and North
Central Montana, especially at the KHVR and KLWT terminals. - Moldan

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

&&

.PREV DISCUSSION...
/ISSUED 520 AM MDT Sat May 4 2024/

Today and Tonight... High pressure aloft will keep this period
dry and a bit warmer than normal across North Central, Central,
and Southwest Montana. However, a cold front approaching Montana
from the west ahead of a Pacific low pressure system will combine
with an exiting area of surface high pressure to strengthen the
surface pressure gradient over the area. This is forecast to
bring southerly winds gusting in excess of 30 mph at times today
across the area, with the winds shifting more easterly tonight and
remaining gusty.

Sunday through Sunday Night... The Pacific system is forecast to
move east across the Great Basin on Sunday, which put the area
under an increasingly moist and unstable southerly flow aloft as
the Pacific cold front moves across the area. This should spread
showers over most of the area Sunday into Sunday evening with a
few embedded thunderstorms. The main threats from these storms
will be isolated lightning strikes, brief heavy rain showers, and
gusty winds, but some small hail is also possible. The main threat
for thunderstorms will diminish during the evening, but snow
levels will start to lower from the southwest overnight as the low
pressure area is forecast to move northeast into Southwest
Montana. This will likely result in at least some light
accumulations of wet snow above 6000 feet, which may cause some
travel problems over mountain passes, so some winter weather
highlights may be needed starting Sunday night in Southwest
Montana.

Monday through Thursday... This is forecast to be coolest,
wettest, and windiest period of the upcoming week. The low
pressure center is predicted to continue moving northeast to
around the Montana/North Dakota border Monday into Monday night,
where it seems to deepen and cut off from its main trough,
causing it to remain there into Wednesday. This will result in
deep moisture wrapping around the low and bringing widespread
mountain snow and low elevation rain to the forecast area, as
temperatures cool back below normal. The heaviest precipitation
amounts are forecast to be closest to the low pressure center,
which includes the plains of North Central Montana; probabilistic
guidance gives a 50 to 70 percent chance of at least 1 inch of
precipitation there for Monday through Wednesday night, with a 40
to 50 percent chance of 2 inches of precipitation across Hill,
Blaine, and Chouteau Counties. However, this same guidance gives
at least a 50 percent chance of 12 inches or more of snow to the
mountains of the Rocky Mountain Front, the Little and Big Belt
mountains of Central Montana, and the mountains of Gallatin and
Madison Counties; in fact, there is a 70+ percent chance of 24
inches or more of snow in the Little Belts.

In addition, models are forecasting that northwest winds moving
around the low pressure area at the mid levels of the atmosphere
could exceed 60 mph on Tuesday, which may translate down into at
least the mountains, if not the plains of North Central Montana,
mainly on Tuesday. Overall, confidence is increasing in the
potential need for winter weather highlights in the mountains and
wind highlights on the plains. However, run-to- run model
inconsistency adds uncertainty to timing and location for such
highlights, so will hold off for now. Overall, though, the system
should start exiting the area on Thursday.

Friday through next Saturday... Ensemble model clusters are in
good agreement with bringing high pressure into Montana late in
the week, but just how strong it will be, and just how warm the
temperatures will be, remains uncertain. Regardless, this should
bring drying conditions to the area with a return to warmer than
normal temperatures. -Coulston

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  63  42  64  42 /   0  10  30  90
CTB  58  37  59  40 /   0  10  20  30
HLN  67  44  68  43 /  10  10  60  80
BZN  65  41  66  36 /   0  10  70  80
WYS  59  36  53  28 /   0  30  90  90
DLN  64  44  60  36 /   0  20  70  90
HVR  63  39  70  43 /   0   0  10  80
LWT  58  36  66  39 /   0   0  20  80

&&

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

$$

http://www.weather.gov/greatfalls