097
FXUS65 KTFX 211937
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
137 PM MDT Sat Sep 21 2024

.SYNOPSIS...

High temperatures will warm to near normal on Sunday and Monday
before climbing well above normal for the remainder of the
upcoming work week. Overall dry conditions are expected for much
of the upcoming week; however, an isolated shower or two can`t be
ruled out from Sunday afternoon through Sunday night as a fast
moving disturbance moves over the Northern Rockies.

&&

.DISCUSSION...

Rest of today through Sunday...transient ridging moving over the
Northern Rockies through late(early) Sunday morning(afternoon) will
continue to bring dry and overall quiet conditions to Southwest
through North Central Montana. Light and variable winds, with the
exception of the eastern slopes of the Rocky Mountain Front, through
the overnight hours tonight will once again allow temperatures to
fall into the 20s to 30s; with the coldest temperatures occurring in
the cold prone valleys of Southwest and Central Montana. Increasing
cross barrier flow on the upstream side of the transient ridge and
an increasing surface pressure gradient along the Continental Divide
and Central Montana mountains will lead to breezy and gusty winds
for areas along the Rocky Mountain Front and MT Hwy 200 corridor for
the afternoon and evening hours on Sunday. While high winds are not
expected across these areas over this timeframe, latest NBM
probabilities do support a 15-30% chance for wind gusts in excess of
45 mph between Cut Bank and Marias Pass. These downsloping winds,
and overall increasing winds elsewhere, will help to push high
temperature on Sunday near to slightly above normal. A fast moving
shortwave over British Columbia Sunday afternoon will then dive
southeast and over the Northern Rockies through Sunday night,
potentially bringing an isolated shower or two to areas along and
north of the I-90 corridor. - Moldan

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

&&

.AVIATION...
21/18Z TAF Period

VFR conditions prevail this TAF period. Aside from some high clouds
late today and tonight, skies will be largely clear. Winds will
remain light, though increase out of the west to southwest late
Sunday morning over the plains. -AM

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

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  39  74  48  72 /   0   0  10   0
CTB  36  68  45  69 /   0  10  10   0
HLN  38  74  52  72 /   0   0  10   0
BZN  32  71  45  69 /   0   0  10  10
WYS  23  64  33  62 /   0   0  10  10
DLN  32  71  43  67 /   0   0  10   0
HVR  33  71  49  70 /   0   0  20   0
LWT  35  70  47  65 /   0   0  10   0

&&

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

$$

http://www.weather.gov/greatfalls