-- Discussion containing changed information from previous version are highlighted. --
312
FXUS65 KTFX 140530
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
1130 PM MDT Thu Jun 13 2024

...Aviation Section Updated...

.SYNOPSIS...

Quiet weather conditions are expected overnight, but there will be
increased chances for light rain showers on Friday morning over
Southwest MT. The showers will transition into thunderstorms on
Friday afternoon, mainly east of a line from Dillon to Bozeman.
Some of these storms could be strong. On Saturday, windy
conditions will develop over then Northern Rockies, which will
continue into early Sunday morning. For early next week, a late
spring storm will affect the entire region, with the potential for
heavy snow in the mountains and a widespread rain at lower
elevations.

&&

.UPDATE...

Given benign conditions forecast for the overnight period, no
significant update is needed this evening. -AM

&&


.AVIATION...
-- Changed Discussion --
14/06Z TAF Period

VFR conditions will prevail throughout the 1406/1506 TAF period;
however, chances for showers and thunderstorms will increase through
the afternoon hours on Friday along and east of a KEKS to KLWT line.
CIGS/VIS beneath or near these showers are not expected to fall
below VFR, but low-VFR conditions may briefly occur. Otherwise,
light winds are generally expected across most terminals outside of
KCTB where breezy and gusty west winds will develop by Friday
afternoon. Some mountain obscuration is possible over the next 24
hours. - Moldan

Refer to weather.gov/zlc for more detailed regional aviation
weather and hazard information.
-- End Changed Discussion --

&&

.PREV DISCUSSION...
/ISSUED 551 PM MDT Thu Jun 13 2024/
Tonight through Friday night...Quiet conditions will continue over
the CWA tonight, with just some passing high clouds. On Friday
morning, a moist southwest flow aloft will develop over Southwest
MT. This will result in showers/thunderstorms developing on Friday
morning, mostly south of a Helena to Lewistown line. On Friday
afternoon, there will be enough instability that a few
strong/isolated severe storms could develop in the Ennis, Big Sky
and Bozeman areas. The main threat from any severe storm will be
gusty winds at this time. It will be another very warm day over
the CWA, with most lower elevations having high temperatures in
the 80s.

Saturday through Sunday...Colder air will slowly move into the CWA
behind the cold front from Friday over the next few days.
Additionally, wind conditions will develop in the Browning and Cut
Bank areas Saturday afternoon and then continue into Sunday night.
There is a 60 percent chance wind gusts could exceed 60 mph in
these areas, thus a high wind watch has been issued for the
Browning and Cut Bank areas. A weak disturbance will move from
west to east across the CWA on Saturday afternoon, producing up
to a 60 percent chance for showers/thunderstorms.

Monday through Tuesday...A late spring storm will affect the
entire CWA early next week. There is 50 percent chance most areas
receive between 0.30 and 0.80 inches of precipitation. There is a
60 percent chance of the mountains receiving over 1 inch of liquid
and a 20 percent chance of the mountains receiving over 2 inches
of liquid. For lower elevations, generally there is a 30 percent
chance of receiving over 1 inch of precipitation, with less than
10 percent chance of 2 inches. With the upper level low moving
over MT, colder air will mix down from aloft, resulting in snow
levels falling down to about 6000 feet at times. This amount of
liquid could result in heavy snow falling for elevations above
7000 feet. Thus a winter storm watch has been issued for the Rocky
Mountain Front. For Southwest MT, the snow amounts look to be a
bit lighter. However, because this will be a heavy wet snow, and
given how late it is in June, the threshold for warning was
lowered a bit to 6 inches, thus a winter storm watch has also been
issued for some of the mountain areas of Southwest MT. It will be
up to later shifts if they want to continue this impact lower
warning snow amount, or make adjustments to the statement. All
areas will have much below normal temperatures, with temperatures
below freezing in many areas at night above 4000 feet.

Wednesday and Thursday...The upper level trof from earlier in the
week will slowly exit the region during this period. Warmer air
will slowly move back in from the west, with the
shower/thunderstorm activity becoming more scattered and lighter.
Brusda

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  48  84  53  72 /   0  10  20  40
CTB  46  78  47  65 /   0   0   0  30
HLN  55  86  56  73 /   0  10  20  40
BZN  50  86  51  75 /   0  40  30  40
WYS  46  77  45  69 /  10  40  10  10
DLN  50  84  51  74 /   0  10  10  10
HVR  52  86  52  73 /   0   0  10  40
LWT  50  81  50  75 /   0  20  40  60

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
High Wind Watch from Saturday afternoon through late Saturday
night for Eastern Glacier, Western Toole, and Central Pondera-
Northern High Plains.

Winter Storm Watch from Monday morning through Tuesday evening
for East Glacier Park Region-Southern Rocky Mountain Front.

Winter Storm Watch from Monday evening through Tuesday evening
for Elkhorn and Boulder Mountains-Gallatin and Madison County
Mountains and Centennial Mountains-Northwest Beaverhead County.

&&

$$

http://www.weather.gov/greatfalls