718
FXUS65 KTFX 201518
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
918 AM MDT Fri Sep 20 2024

.SYNOPSIS...

A cold front will bring breezy to windy conditions and scattered
showers today followed by a dry and cooler day on Saturday.
Another weather system quickly passes through the Northern Rockies
late Sunday into Monday for another chance for showers before
much warmer and drier conditions arrive for the middle of next
week.

&&

.UPDATE...

It will be windy across North-central and Central Montana this
afternoon and evening with the highest gusts of 40 to 50 mph
expected along the Rocky Mountain Front over to the Hi-line. This
afternoon through this evening a cold front will bring rain to
North-central Montana primarily north of the Highway 200 Corridor.
Only minor adjustments were made to the forecast this morning. See
the updated HYDROLOGY section below. -IG

&&

.AVIATION...
20/12Z TAF Period

VFR conditions are forecast to mostly continue across much of
Southwest (KWYS, KEKS, KBZN), Central (KHLN, KGTF, KLWT), and North
Central (KHVR, KCTB) Montana through at least 21/12Z, unless
otherwise mentioned, such as patchy fog development in the Southwest
Montana valleys potentially causing a period of MVFR conditions at
KWYS through 16Z or so.

A disturbance moving through the area will continue moderate west to
northwest mid-level winds, which will cause periods of mountain wave
turbulence. Areas of low-level wind shear will also occur through
around 15Z and again after 03Z; in between, these gusty winds will
mix down to the surface.

A weak frontal boundary will also move south over the plains of
North Central Montana after 15Z, which will shift winds more
northerly at the KCTB and KHVR terminals, as well as bring scattered
showers with periods of mountain obscuring MVFR/IFR ceilings to
those same terminals between 20Z and 02Z. Showers are less likely to
reach the KGTF and KLWT terminals, but ceilings could lower to
mountain top obscuring low VFR after 00Z.
-Coulston

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

&&

.HYDROLOGY...

The river gauge at Clear Creek near Chinook crested at 5.3 ft
during the overnight hours and has gone back up to near Minor
Flood stage at 5.5 ft this morning. As a result a Flood Warning
has been issued through tonight. The Milk River near Harlem has
also experienced a significant rise in water levels over the last
24 hours, but currently remains well below flood stage with no
further significant rises in the forecast. -IG/RCG

&&

.PREV DISCUSSION...
/ISSUED 500 AM MDT Fri Sep 20 2024/

A cold front over the Canadian prairies will continue to move
southward through Hi-Line this morning and eventually though the
remainder of Central/North-central MT while a shortwave trough
dives southeastward from British Columbia. This will bring a gusty
north to northwesterly wind shift, along with scattered showers,
mainly to the northern half of the CWA this afternoon and early
evening. Peak wind gusts may reach 40 mph along the Rocky Mountain
Front and the plains, but probabilities for gusts over 55 mph
remain well under 30% for most locations.

This system looks to drop snow levels to around 6,000 ft this
afternoon and evening in the East Glacier area. Logan Pass and
other areas of higher terrain in Glacier Park may see a dusting of
snow. Precipitation ends by late this evening and partial
clearing during the overnight hours will result in the chilliest
night thus far for this young fall season. Many lower elevations
will see lows in the 30s and temperatures will even drop in the
20s and teens in the wind protected valleys of central and
southwest MT.

After a relatively quiet period Saturday into early Sunday,
another shortwave moves through the region late Sunday into Monday
and brings more chances for showers, northwesterly breezes, and a
slight cool down. However, this system will not appear to be as
strong or cold as its predecessor.

The latest 3 to 7 day cluster analysis unanimously agree with
high pressure aloft building over the Northern Rockies by the
middle of the workweek for a return to well above normal
temperatures and dry conditions. Over 60% of ensemble suites
flatten the ridge by next weekend while the remaining members more
or less maintain its strength. Additional opportunities for
breezy to windy conditions, cooling temperatures, and shower
chances can be expected should the ridge become compromised.
Otherwise, the lesser likely scenario will be a continuation of
dry conditions and above normal temperatures. - RCG

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  69  37  62  38 /  30  30   0   0
CTB  61  34  62  35 /  60  60   0   0
HLN  71  39  64  39 /   0   0   0   0
BZN  72  32  63  34 /  10   0   0   0
WYS  63  25  63  26 /  10  10   0   0
DLN  68  31  62  34 /   0   0   0   0
HVR  65  37  61  37 /  60  20   0   0
LWT  67  36  58  35 /  10  10   0   0

&&

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

$$

http://www.weather.gov/greatfalls