-- Discussion containing changed information from previous version are highlighted. --
382
FXUS65 KTFX 211451
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
851 AM MDT Sat Sep 21 2024

.SYNOPSIS...

Temperatures will remain cooler than normal under a northwest flow
aloft through tonight, with the potential for frost again in
valleys and low-lying areas. High pressure aloft should then warm
temperatures back above normal on Sunday with breezy southwest
winds, before a weak cold front brings a chance of mainly
mountain precipitation and gusty westerly winds on Monday. Warmer
and drier conditions are expected again for the rest of the work
week.

&&

.Update...

-- Changed Discussion --
No morning update is needed as the on-going forecast is performing
well. Expect a pleasant fall day across all of Southwest through
North Central Montana, with high temperatures running 5 to 10
degrees below normal, light and variable winds, and sunny to
mostly sunny skies. - Moldan
-- End Changed Discussion --

&&

.AVIATION...
21/12Z TAF Period

Lingering low VFR/MVFR clouds over the eastern half of Central/North-
central MT is expected to continue dissipating through 21/16Z.
Patchy fog development can still be expected over the next few
hours. This should generally be confined to the wind protected
high/river valleys with KWYS being the most likely candidate for
some vicinity or brief prevailing fog. Otherwise, widespread VFR
conditions are expected for this TAF period. Winds become light
easterly for most locations this afternoon and evening. - RCG

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

&&

.PREV DISCUSSION...
-- Changed Discussion --
/ISSUED 537 AM MDT Sat Sep 21 2024/

Key Points:

- Cool through tonight with another chance for frost

- Next chance for precipitation on Monday

- Dry, breezy at times, and warm through the week

Today through Sunday... A lingering northwesterly flow aloft will
keep cooler than normal air over North Central, Central, and
Southwest Montana today into tonight. Areas of low clouds across
Central Montana and patchy fog in valleys and low lying areas
will burn off this morning, leaving skies mostly clear through the
weekend, as weak high pressure aloft is forecast to build into the
area. Light winds overnight will allow temperatures temperatures
to fall below normal again for much of the area; some valley and
low- lying areas could approach freezing temperatures again,
possibly causing some patchy frost. An approaching shortwave
Pacific trough will increase westerly winds aloft into Sunday,
which could be mixed down to the surface, as temperatures are
forecast to warm back above seasonal averages. However, winds are
not anticipated to be exceptionally strong, as the probabilities
for 15+ mph sustained winds and 25+ mph gusts are greater than 50
percent only over the plains along and west of Interstate 15.

Monday... The shortwave trough with its associated Pacific cold
front is forecast to move through the forecast area on Monday.
However, forecast models continue to weaken this fast-moving
disturbance, which will limit the 20 to 30 percent chance for
measurable precipitation to the mountains. Breezy westerly
downsloping winds with the passage of the system will also hinder
precipitation development over the plains. Temperatures are only
forecast to cool down to near or slightly below normal.

Tuesday through next Saturday... Ensemble model cluster analysis
continues to agree with bringing an amplified high pressure ridge
back into the area on Tuesday with an increasing southwest flow
aloft on Wednesday. This will keep the area dry as temperatures
warm to between 10 and 15 degrees above normal by Wednesday with
breezy southwest winds; some plains areas will have a 30 to 50
percent chance of exceeding 85 degrees on Wednesday. The cluster
analysis starts to differ after Wednesday, as 60 percent of the
clusters agree on keeping the area under the influence of the
ridge, while 40 percent want to start breaking the ridge down.
Regardless, moisture is fairly limited, so even a persistent
southwesterly flow aloft will keep the area dry, but the NBM
starts a gradual cooling of temperatures. The next chance for a
widespread chance of precipitation does not move in until Friday
night into Saturday as temperatures approach seasonal averages
once again. -Coulston
-- End Changed Discussion --

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  62  40  75  47 /   0   0   0  10
CTB  62  35  69  43 /   0   0   0  10
HLN  66  40  74  49 /   0   0   0  10
BZN  63  34  72  43 /   0   0   0  10
WYS  62  25  65  31 /   0   0   0  10
DLN  61  34  71  42 /   0   0   0   0
HVR  62  37  71  47 /   0   0   0  10
LWT  57  36  71  44 /   0   0   0  10

&&

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

$$

http://www.weather.gov/greatfalls