137
FXUS65 KTFX 241417
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
817 AM MDT Tue Sep 24 2024

.SYNOPSIS...

Much warmer and dry conditions are expected for the next couple
of days before a fast moving weather system brings periods of
breezy to windy conditions, a few showers or storms, and cooler
temperatures to close out the week.

&&

.UPDATE...

Winds this morning were coming in a little higher than previously
forecasted so some adjustments were made using the latest model
guidance to better fit what is expected through the rest of today.
Otherwise the going forecast remains on track. -thor


&&

.AVIATION...
24/12Z TAF Period

VFR conditions will continue through at least 25/12Z across North
Central (KCTB, KHVR), Central (KLWT, KGTF, KHLN), and Southwest
(KBZN, KEKS, KWYS) Montana.

High pressure aloft will only allow a few high clouds to pass
overhead. Breezy west to southwest surface winds will shift more
southerly after 18Z; occasional gusts will mostly stay between 20
and 30 kt. -Coulston

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

&&

.PREV DISCUSSION...
/ISSUED 442 AM MDT Tue Sep 24 2024/

High pressure builds in for the next couple of days for a return
of well above average temperatures and dry conditions. Expect
afternoon highs to warm into the 80s for most lower elevation
locations today, with the warmest areas making a run for 90 on
Wednesday.

A trough moves onto the Pacific NW coast and displaces the upper
level ridge in favor of a southwesterly flow aloft by late
Wednesday. This will increase west to southwesterly surfaces
winds, though the strongest winds look to hold off until Wednesday
night and Thursday when the trough ejects eastward and sends a
Pacific cold front racing through the CWA.

Isolated shower activity, mountain wave activity, and the
transfer momentum of the front itself looks to help mix 40 to 50
kt H500/H700 winds to the surface along the Rocky Mountain Front
and adjacent plains Wednesday night. This will be followed by the
maintenance of the windier conditions into Thursday thanks to deep
layer mixing and cold air advection.

Current probabilistic guidance for wind gusts in excess of 55 mph
are running over 50% for locations along the Rocky Mountain Front
eastward onto the northern high plains near the Cut Bank area.
These chances fall well below 30% for other areas, but there are
typically some concerns for stronger bursts of winds along the Hi-
Line in this type of set up as well.

Given the aforementioned factors, a High Wind Watch was issued
for the Rocky Mountain Front, their adjacent high plains zones,
and the eastern Toole and Liberty zone. Timing of the cold front
Wednesday night and the overall strongest mixing winds on Thursday
still needs to be fine tuned, but going with 26/03Z (9 pm Wed) to
26/21Z (3 pm Thurs) run time seems reasonable for now.

A stronger west to southwesterly flow aloft continues through at
least the first half of the weekend for more breezy to windy
conditions and above normal temperatures. probabilities for
sustained winds/gusts exceeding 40 mph/55 mph remain low, but
those with outdoor recreation plans should still expect windy
conditions along the Rocky Mountain Front.

Forecast certainty is still a bit murky for the weekend, though
more ensembles are now favoring the passage of an open wave and
attendant cold front sometime between the late Saturday and Monday
timeframe. While there are still differences among ensemble
members, most yield temperatures cooling closer to average and
slight chances for precipitation. - RCG

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  83  55  88  53 /   0   0   0   0
CTB  82  49  85  51 /   0   0   0  20
HLN  83  52  89  53 /   0   0   0   0
BZN  80  47  87  48 /   0   0   0   0
WYS  73  35  75  36 /   0   0   0   0
DLN  78  47  83  47 /   0   0   0   0
HVR  82  51  89  54 /   0   0   0   0
LWT  78  53  85  52 /   0   0   0   0

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
High Wind Watch from Wednesday evening through Thursday
afternoon for East Glacier Park Region-Eastern Glacier, Western
Toole, and Central Pondera-Eastern Toole and Liberty-Northern
High Plains-Southern High Plains-Southern Rocky Mountain Front.

&&

$$

http://www.weather.gov/greatfalls