786
FXUS65 KTFX 160420
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
1020 PM MDT Sat Jun 15 2024

...Aviation Section Updated...

.SYNOPSIS...

This afternoon, thunderstorms and showers move through the area.
Some of these thunderstorms have become severe producing erratic
high winds. Aside from winds associated with thunderstorms, gusty
winds develop across the region, with high winds forecast along
the Northern Rocky Mountain Front and the adjacent plains. These
strong winds continue through tomorrow morning. Next week, cooler
temperatures and widespread precipitation are forecast.

&&

.UPDATE...

Updated forecast is out. No major changes to the current forecast
overnight. Most of the precipitation has exited the CWA. There is
a 20 percent chances showers could redevelop after Midnight for
areas mostly north of Highway 2. Otherwise, periods of strong
winds are expected in the Browning/Cut Bank areas overnight and
into Sunday morning. Cut Bank did record a 58 mph gust earlier
this evening already. Thus, no changes to the high wind
statement. Cooler air is now moving into the region, with the
cooling trend to continue for the next few days.

Looking ahead to the late spring storm, Central MT looks like it
has the highest probability of receiving the most precipitation
with this system. With that said, snow amounts have decreased over
the Glacier Park region, and that winter storm watch might end up
being cancelled for that area, depending what the 0z runs shows
tonight. Otherwise, the rest of the winter storm watches remain on
track, generally using the lower threshold of 6 inches for
potential warning decisions. Brusda

&&

.AVIATION...
16/06Z TAF Period

VFR conditions will prevail for across all terminals through 12z
Sunday after which increasing shower activity and lowering CIGS
along the International Border may begin to usher MVFR conditions
south towards the KCTB and KHVR terminals. Confidence in these MVFR
conditions occurring is approximately 20-40% at this time, so
withheld mention of MVFR conditions for the TAF package given the
low probabilities. Otherwise the biggest concern to terminals will
be strong and gust west winds, particularly at the KCTB terminal
where frequent wind gusts approaching 50kts are expected through 12-
15z Sunday. Strong mid-level winds will also contribute to mountain
wave turbulence and instances of low level wind shear through 12-18z
Sunday over the plains of Central and North Central Montana. Winds
will gradually begin to subside from late Sunday morning and through
the afternoon hours. Mountain obscuration is likely along the
Continental Divide and North Central Montana for most of the next 24
hours. - Moldan


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

&&

.PREV DISCUSSION...
/ISSUED 230 PM MDT Sat Jun 15 2024/

Today...Thunderstorms and showers have developed, and are moving
across the region. Some of these storms have become severe,
producing high winds that are erratic in nature. Additionally,
periods of heavy rainfall accompany these storms. Aside from winds
associated with these thunderstorms, strong gusty winds have
developed across the region. High winds are forecast across the
Northern Rocky Mountain Front and the adjacent plains. These winds
are forecast to continue into tomorrow morning.

Tomorrow...A cooler day is forecast. Generally, dry conditions
prevail, with some moisture forecast along and north of the Hi-
Line. As the day progresses, wind speeds decrease.
- Fogleman

Monday through Wednesday...Ensemble clusters continue to support
longwave troughing moving over the Northern Rockies throughout the
period, with the leading modes of uncertainty being the amplitude
of the trough as it moves over the Great Basin on Monday and then
the position and/or timing of the trough on Tuesday and Wednesday as
it lifts northeast to over the High Plains. With respect to Monday`s
uncertainty, main impacts to North Central through Southwest
Montana will be just how "cold" and wet conditions will be, with
high temperature spreads across lower elevations between the 25th
and 75th percentiles being approximately 10-15 degrees from the
upper 40s/low 50s (25th percentile) to the upper 50s/low 60s.
Additionally, precipitation spreads for Monday and Monday night
range from a couple hundreths over northern and southern portions of
North Central and Southwest Montana (respectively) to 0.10"-0.25"
elsewhere for the 25th percentiles, with 0.25" to just over 1" for
the 75th percentiles. These large spread between temperatures and
precipitation also leads to uncertainty with respect to the type of
mountain precipitation, with NBM probabilities for 6" or more of
snow from Monday through Tuesday generally ranging between 30-50%.
Have continued the Winter Storm Watch from Monday through Tuesday
given this uncertainty, but regardless if the Watch is upgraded to
an Advisory or Warning or cancelled...recreationists should be
prepared for cold and raw conditions. Additionally, should higher
end snowfall amounts materialize over this timeframe, damage to tree
limbs and power outages would be possible given the heavy, wet
nature of the snow. High temperatures will warm slightly for Tuesday
and Wednesday, but remain below normal. Light precipitation is
expected linger through the morning and early afternoon hours on
Tuesday, with overall drying conditions expected thereafter.

Thursday through next Saturday...Ensemble clusters largely support
and unsettled southwest flow regime over the Northern Rockies for
the second half of the work week and into next weekend, which would
translate to moderating temperatures and daily chances for showers
and thunderstorms. - Moldan

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  41  65  42  51 /   0   0  40  80
CTB  40  59  36  56 /  10  30  20  60
HLN  42  67  44  53 /   0   0  60  90
BZN  35  66  40  56 /  10   0  40  90
WYS  35  60  37  51 /  10   0  10  60
DLN  33  65  38  51 /   0   0  40  80
HVR  44  64  42  57 /  10  20  20  80
LWT  37  63  38  51 /  10   0  40  90

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
High Wind Warning until 9 AM MDT Sunday for East Glacier Park
Region-Eastern Glacier, Western Toole, and Central Pondera-
Northern High Plains-Southern 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 Big Belt, Bridger and Castle Mountains-Elkhorn and Boulder
Mountains-Gallatin and Madison County Mountains and Centennial
Mountains-Little Belt and Highwood Mountains-Northwest
Beaverhead County.

&&

$$

http://www.weather.gov/greatfalls