186
FXUS65 KTFX 201940
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
140 PM MDT Fri Sep 20 2024

.SYNOPSIS...

This afternoon there will be showers and thunderstorms
primarily along the Hi-Line. This afternoon through this evening it
will be windy in North-central Montana with the strongest winds
along the Rocky Mountain Front over to the Hi-Line. Tomorrow morning
it will be cold with numerous lower-elevation locations seeing
frost. An upper-level shortwave will bring precipitation chances to
the area Sunday evening through Monday. A ridge builds into the area
on Tuesday which will bring warm temperatures and dry conditions for
the middle of next week.

&&

.DISCUSSION...

This afternoon through Saturday...A cold front is moving south from
Canada. This will bring showers and thunderstorms to the Hi-Line
this afternoon through this evening. The showers will slowly spread
south to the rest of North-central Montana by midnight tonight
before they fizzle out. An isolated thunderstorm along the Hi-Line
will produce strong to severe wind gusts. The Storm Prediction
Center has issued a Marginal Risk (5% chance within 25 miles of a
point)for severe wind gusts along the Hi-Line today. The Hi-Line
has a 15 - 30% chance for seeing a tenth of an inch of rain or
greater through midnight tonight. The front combined with an
upper-level shortwave trough is bringing strong winds to North-
central Montana. The strongest winds will be along the Rocky
Mountain Front over to the Hi-Line where gusts of 40 to 50 mph are
expected. The Rocky Mountain Front and adjacent plains have a 50 -
80% chance for winds of 47 mph or greater through midnight
tonight. The cold front and upper-level shortwave trough will
lower snow-levels to 5500 feet in Glacier National Park. Areas at
5500 feet and above are likely to see a dusting of snow this
afternoon through Saturday morning. There is a 20% chance for
patchy fog to form in some valley locations Saturday morning.
Surface high pressure moves over North-central, Central, and
Southwestern Montana on Saturday. This combined with the cold
front will bring cold temperatures and clear skies to the area.
This will result in numerous lower-elevation locations across
North-central, Central, and Southwestern Montana having frost.
Saturday morning will be the coldest morning of this early fall
period. On Saturday morning lower-elevations of Southwestern
Montana and the Cut Bank area have a 10 - 30% chance of seeing low
temperatures of 32 degrees or colder.

Sunday through Tuesday...On Sunday the upper-level ridge remains
over North-central, Central, and Southwestern Montana. Then late
Sunday afternoon an upper-level shortwave moves through the flow.
This will bring precipitation chances to North-central, Central, and
Southwestern Montana. On Sunday temperatures will warm up to
slightly above seasonal averages. Sunday morning it will be cold
with some valley locations of Southwestern Montana seeing frost.
On Sunday morning lower-elevations of Southwestern Montana have a
10 - 25% chance of seeing low temperatures of 32 degrees or
colder. On Monday the upper-level shortwave remains over the area
for most of the day. This will cool temperatures back down to
about seasonal averages with precipitation chances for North-
central, Central, and Southwestern Montana. Sunday through Monday
there is a 10 - 30% chance for a tenth of an inch of rain or
greater across North-central, Central, and Southwestern Montana.
On Tuesday an upper-level ridge moves over North-central,
Central, and Southwestern Montana. This will bring dry and warm
weather to the area. Temperatures look to be up to 10 degrees
above seasonal averages. -IG

Wednesday through next Friday... 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 less likely scenario will be a
continuation of dry conditions and above normal temperatures. -
RCG

&&

.AVIATION...
20/18Z TAF Period

A fast moving disturbance will bring lowering CIGS and chances for
showers to the plains of Central and North Central Montana this
afternoon and evening. While low-VFR/VFR conditions are
predominately expected across all terminals through the 2018/2118
TAF period, periods of MVFR conditions are possible at the KCTB,
KHVR, KGTF, and KLWT terminals through this evening, and potentially
into the morning hours on Saturday in northerly upslope favored
locations (i.e. KGTF and KLWT terminals). In addition to the chances
for showers, breezy and gusty southwest to northwest winds will
occur across all of Southwest through North Central Montana this
afternoon and through 00-03z Saturday, with the strongest winds
developing over the plains of Central and North Central Montana.
Mountain wave turbulence is possible across all of the Northern
Rockies. Mountain obscuration is likely through 12z Saturday over
Central and North Central Montana.

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 went back up to near Minor Flood
stage at 5.5 ft this morning. As a result a Flood Warning has been
issued through 6 PM tonight. -IG/RCG

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  71  35  62  39 /  20  30   0   0
CTB  64  32  61  35 /  50  40   0   0
HLN  70  39  66  40 /   0   0   0   0
BZN  72  34  63  34 /   0   0   0   0
WYS  61  27  62  26 /   0  10   0   0
DLN  70  33  61  34 /   0   0   0   0
HVR  65  39  62  36 /  50  20   0   0
LWT  69  34  58  36 /  10  10   0   0

&&

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

$$

http://www.weather.gov/greatfalls