785
FXUS65 KTFX 250229
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
829 PM MDT Tue Sep 24 2024

.UPDATE...

An upper level high is centered over SW WY this evening with
ridge axis extending north through western and central MT. Except
for thin/high clouds spilling over the ridge and some patchy haze
from prescribed burning in the region, mainly clear, quiet and
dry conditions will prevail across the area tonight. Hoenisch

&&

.SYNOPSIS...

Much warmer and dry conditions are expected over 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.

&&

.AVIATION...
25/00Z TAF Period

Flow aloft gradually turns more southwesterly through Wednesday as
upper level high pressure shifts east of the area with just some
increase in high level clouds. VFR conditions prevail with south to
southwesterly surface winds increasing at most terminals Wednesday
afternoon. Increased flow over the Rockies may also lead to some
Mountain wave turbulence on Wednesday. Hoenisch

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

&&

.PREV DISCUSSION...
/ISSUED 549 PM MDT Tue Sep 24 2024/

Key Points:

 - Well above normal temperatures on Wednesday with lower
   elevations reaching the upper 80s to low 90s.

 - A strong cold front will move through the region Wednesday
   night into Thursday morning bringing gusty winds along the
   Rocky Mountain front and the Hi-Line.

 - Warmer temperatures will continue through the weekend before
   another cool off at the start of next week.

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.

Updated model guidance has been split on how strong this event will
be and has reduced some of the probabilities further along portions
of the Hi-Line. Current probabilistic guidance for wind gusts in
excess of 55 mph ranges from 50 to 70% for locations along the Rocky
Mountain Front. East of Cut Bank these probabilities start to drop
off below 30% fairly quickly, however, the decision was made to keep
the Hi-Line portions of the High Wind Watch in order to wait for
confirmation with future model runs as typically there are some
concerns for stronger bursts of winds along the Hi-Line in this type
of set up as well.

Generally, the strongest wind gusts are expected between midnight
and noon on Thursday. But stronger wind gusts outside of that time
frame cannot be ruled out, thus the decision was made to keep the
watch timing the same for now. - RCG/thor

Friday thru Monday... 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  57  87  53  75 /   0   0   0   0
CTB  49  84  51  67 /   0   0  20   0
HLN  54  89  53  78 /   0   0   0   0
BZN  48  87  48  80 /   0   0   0   0
WYS  36  74  38  71 /   0   0   0   0
DLN  47  82  48  77 /   0   0   0   0
HVR  52  89  54  74 /   0   0   0  10
LWT  54  85  51  74 /   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