High Wind Watch 9, NWS Great Falls, MT

Area Forecast Discussion
National Weather Service Great Falls MT
1143 AM MDT Sun Jun 2 2024

...AVIATION SECTION UPDATED...

.SYNOPSIS...

A westerly flow across the region will maintain temperatures near
seasonal averages today. The next weather system brings
increasing clouds tonight with precipitation mainly near the
continental divide overnight before showers and a few
thunderstorms move across the area with a cold front on Monday.
Strong west winds develop behind the cold front Monday night with
periods of stronger winds affecting much of the area through
Tuesday night. Above normal temperatures and drier conditions
return for later next week.

&&

.UPDATE...

Primary concern for this afternoon will be isolated shower and
thunderstorm development, mostly along the Continental Divide and
Southwest MT. Impacts are expected to be limited to gusty and
erratic winds with the stronger cells. Otherwise, west to
northwesterly breezes may gust to around 25 mph or so over the
plains this afternoon and clouds will be on the increase with
light rain showers expected tonight, mostly over and near areas of
higher terrain. - RCG

&&

.AVIATION...

02/18Z TAF Period

VFR conditions prevail across the area through the afternoon hours
under scattered to broken clouds mid-level clouds. There will be a
few isolated showers and or thunderstorms this afternoon and
evening, mostly impacting areas of higher terrain. Upper level
moisture streams into the region tonight for increasing clouds and
the development of of light rain showers. Most of this activity will
be concentrated along the Continental Divide, but some light rain
and or sprinkles can be expected farther east, especially over areas
of higher terrain and over the eastern portions Central/North-
central MT. VFR conditions generally continue at TAF sites through
Monday morning but precipitation and mountain obscuration will
increase and expand eastward towards the end of the TAF period. - RCG

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

&&

.PREV DISCUSSION...
/ISSUED 432 AM MDT Sun Jun 2 2024/

A few light showers continue to track east across mainly southwest
MT early this morning associated with a relatively weak shortwave
disturbance thats exits the area later this morning. Clouds
decrease through early this afternoon before increasing again
later this afternoon through tonight as a deep plume of Pacific
moisture begins to move into the NW US, driven by an unseasonably
strong Pacific upper level jet. There is enough moisture and weak
instability in place this afternoon into this evening for some
isolated shower/thunderstorm development, primarily near the
continental divide and across southwest MT with the arrival of
additional moisture overnight leading to more widespread
precipitation developing near the continental divide.

A fairly potent shortwave trough moves onshore Monday and
continues east with cyclogenesis occurring in southern AB as the
wave emerges east of Rockies late Monday/Monday night. This drives
a Pacific cold front across the area Monday afternoon with
widespread precipitation initially along the continental divide
transitioning to showers and a few thunderstorms shifting east
across the area in association with the cold front. The risk for
thunderstorms is greatest across eastern portions of central and
southwest MT Monday afternoon with strong wind gusts being the
primary concern with any storms. Precipitation at higher
elevations in Glacier national park (above 5500 ft) may change to
snow Monday evening as colder air aloft moves in behind the cold
front though most areas further south and east across the area
will see precipitation diminish as the colder air arrives behind
the front.

The passage of the cold front late Monday afternoon/evening will
mark the beginning of a very windy period for much of the area as
strong westerly flow surges across the Rockies to the south of
the wave ejecting east across AB Monday night with another surge
of stronger westerly flow moving across the area Tuesday and
Tuesday night as the upper level jet moves across the region. Wind
gusts in excess of 55 mph become likely (>60% probability)
initially along the Rocky Mtn Front and adjacent areas Monday
evening and likely also adjacent to the the Little
Belt/Highwood/Bears Paw mountain ranges later Monday night aided
by favorable temperature/wind profiles for mountain wave
enhancement. The second surge of stronger westerly flow on Tuesday
looks to bring more widespread potential for gusts in excess of
55 mph with probabilities ranging from 40-60% across much of the
north-central MT plains to 90% or higher along the Rocky Mtn Front
with 20-30% probabilities for valley locations north of I90
including the Helena and Bozeman areas. No changes were made to
the High Wind Watch overnight.

The upper level jet lifts north Wednesday with winds aloft and at
the surface gradually relaxing by Wednesday afternoon and evening
as upper level ridging begins to build across the western US.
longer range model ensembles continue to support amplification
the the ridge late this week into the weekend with temperatures
trending above seasonal averages. There continues to be some
divergence however with the precise location of the ridge axis
leaving some uncertainty still at this time in exactly how much
above average temperatures will be and the location/origin of
moisture moving into the area around/over the ridge by next
weekend. Hoenisch

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  72  55  70  45 /  10  30  50  10
CTB  69  50  65  42 /  10  30  20  10
HLN  75  55  70  45 /  20  20  90  20
BZN  72  51  68  40 /  30  10  90  60
WYS  64  44  55  37 /  40  20 100  80
DLN  71  52  65  40 /  10  10  90  30
HVR  75  54  75  47 /   0  30  50  20
LWT  69  50  68  41 /  10  20  80  50

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
High Wind Watch from Monday evening through Wednesday morning
for East Glacier Park Region-Eastern Glacier, Western Toole, and
Central Pondera-Northern High Plains-Southern High Plains-
Southern Rocky Mountain Front.

High Wind Watch from Tuesday morning through Wednesday morning
for Bears Paw Mountains and Southern Blaine-Cascade County below
5000ft-Eastern Toole and Liberty-Fergus County below 4500ft-Hill
County-Judith Basin County and Judith Gap-Northern Blaine County.

&&

http://www.weather.gov/greatfalls