855
FXUS65 KTFX 152350
AFDTFX

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

UPDATED AVIATION SECTION

.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.

&&

.DISCUSSION...

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

&&

.AVIATION...
16/00Z TAF Period

VFR conditions are expected to continue through at least 17/00Z
across North Central (KCTB, KHVR), Central (KLWT, KGTF, KHLN), and
Southwest (KBZN, KEKS, KWYS) Montana, unless otherwise mentioned.

Winds will be the main concern for this period. Strong westerly
winds associated with a passing disturbance have mostly translated
down to the surface, bringing widespread sustained winds of 20 to 30
kt gusting to 50 kt at times. These mid-level and lower-level winds
will cause mountain wave turbulence and low-level wind shear,
respectively, through around 15Z, after which the winds should
gradually decrease.

Otherwise, clouds and showers will continue to decrease in the wake
of a cold front exiting the area to the east. However, the
disturbance mentioned above may bring a few showers with brief
periods of MVFR ceilings to the Canadian border area after 12Z, as
high- and mid-level cloudiness start to increase again from the west
after 15Z. -Coulston

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

&&

.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